Form 4 - Biology Notes

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Biology Form 4 Notes (2003-2004)2005 Jordan Mifsud (4.8) 5.8

Biology Notes Form 4

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1: N

UTRITION

The 7 Basic Food Substances

All the food we eat is made up of the following 7 basic substances: 1. Carbohydrates 2. Fats 3. Proteins 4. Vitamins 5. Minerals 6. Fibre 7. Water

Carbohydrates, fats, proteins and vitamins are organic substances because they contain carbon in their molecular structure. Water and minerals are inorganic substances since they don’t contain carbon.

Carbohydrates, fats and proteins are needed in bulk in our diet, while vitamins and minerals are needed in smaller amounts.

A person whose diet lacks any of these nutrients suffers from malnutrition, and this may give rise to a deficiency disease.

Food gives us energy. The amount of energy needed by our body isn’t the same for everyone. The amount of energy needed to live depends on the person’s sex, job, attitude, age and other factors like if the person is a pregnant woman.

\Carbohydrates are organic substances made up of carbon, hydrogen and oxygen. They are very important because they provide energy for the body. There are 3 types

of carbohydrates: sugars, starch, and cellulose. A. Sugars

 Glucose (C6H12O6)

 Fructose (sugars in fruit)

 Sucrose (table sugar)

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Biology Form 4 Notes (2003-2004)2005

 Lactose (found in milk)

 Maltose (found in barley grains) B. Strach

Jordan Mifsud (4.8) 5.8

 Found in bread, potatoes, rice, cereals etc. Plants store food as starch. C. Cellulose

 Found in all unrefined plant food. An important source of fibre.

Carbohydrates are all made up of molecules of glucose bonded (joined) together. The simplest form of carbohydrate is glucose. Two molecules of glucose joined together

with a bond, form maltose, lactose and sucrose sugars. Starch, cellulose and

glycogen are formed when 3 or more glucose molecules are joined together with bonds.

Glucose’s molecule is represented by a hexagon:

A single sugar molecule is called a monosaccharide. Examples of monosaccharides are glucose and fructose.

Glucose Molecule

Sucrose, maltose and lactose are all disaccharides because they have 2 sugar molecules bonded together.

Starch, cellulose and glycogen are all polysaccharides because they are made up of

3 or more sugar molecules bonded together.

Page 2 Fb: 2011 SPM Tips/Ramalan/Soalan Bocor (Public page)

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Carbohydrates are found in cereals, pasta, bread, fruit, potatoes sugary food such as ice cream etc.

Glucose’s chemical formula is the following: C6H12O6.

Plants store food as starch, while animals store food as glycogen. Both glycogen and starch are polysaccharides. Polysaccharides are NOT sweet but ARE insoluble.

2. Fats

 Fats are organic substances. Lipids are fats in a liquid state. Fats are useful for our body, because they:

 provide energy,

 can be stored for later use,

 build up cell membranes,

 layers serve as an insulating layers under mammal’s skins and

 and oils on the surface of the skin makes the skin waterproof. Fat is found in vegetable oil, milk, fried foods, eggs, beef etc.

The simplest fat molecule is made up of 1 molecule of glycerol and 3 fatty acids bonded together.

Fatty Acids Glycerol

Fatty Acids Fatty Acids

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3. Proteins

Proteins are organic substances made up of hydrogen, carbon and oxygen,

nitrogen and sometimes they contain sulphur. Proteins are needed by the body to

grow and repair tissues (a cellular structure), they are components of cell

membranes, are used to produce enzymes (biological catalysts) and hormones. The simplest possible protein is an amino acid, thus proteins are made up of amino acids, which can be represented as any form of shape (circle, rectangle, square).

Amino acids are joined together by peptide bonds. When 2 amino acids connected together with a peptide bond, a dipeptide forms. When 3 or more amino acids are joined together, a polypeptide is formed.

Amino Acid Dipeptide Polypeptide

When proteins are heated, they are denatured; they change shape, its properties and functions are destroyed. Food rich in proteins are milk, meat, eggs, nuts, fish etc.

4. Water

Water is vital for animals and almost all living organisms. It makes up to one third of

the human body mass. Water is an inorganic substance with the chemical formula H2O.

Water is important for animals because it gives support to aquatic animals, gametes (sex cells like sperms and eggs) travel in a watery medium, sweating has a cooling effect on the body, and urine and tears are mostly made up from water. There is water even in the joints, so that reduces friction when bones move. Even blood is partially made up of water.

Water is also needed by plants, to make leaves turgid, guard cells move by osmosis

and water takes part in the chemical reaction in which plants make there food (by photosynthesis). Some seeds germinate with the help of water.

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5. Minerals

Many minerals are important for our body. There are other trace elements not listed in the table which are useful for other bodily functions.

Mineral Calcium Iron Phosphorous Sodium Iodine Fluorine Magnesium 6. Vitamins Found in Milk, cheese, fish, mineral water Tomatoes, liver, kidneys Many foods, e.g. milk Salt, many foods. Sea food, drinking water Water, toothpaste Most foods

Use in the body

Developing bones and maintaining their rigidity. Forms intracellular cement and the cell

membranes, and in regulating nervous excitability and muscular contraction. Part of haemoglobin in red blood cells.

Important for bones and teeth.

Present in extra cellular fluid, and regulates it. Needed to synthesize hormones of the thyroid gland.

Builds a layer above enamel. Important for metabolism. Deficiency disease Rickets Anaemia headaches, tiredness, and lethargy Osteomalacia (rickets) Cramps Goitre

Can lead to tooth decay

Tremors and convulsions

Vitamins are very, very important for the body, but only in small quantities.

Vitamin Found in Use Deficiency disease

A Liver, carrot Important for eyes. Night Blindness

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Biology Form 4 Notes (2003-2004)2005 Jordan Mifsud (4.8) 5.8 D E K B1 B2 Niacin (B6) C

Fish liver oil

Milk, egg yolk, lettuce

Cabbage, spinach, fish livers

Pork, organ meats lean meats, eggs, leafy green

vegetables, whole or enriched cereals, berries, nuts, and legumes.

Liver, milk, meat, dark green vegetables, whole grain and enriched cereals, pasta, bread, and mushrooms.

Liver, poultry, meat, canned tuna and salmon.

Citrus fruits, fresh strawberries, cantaloupe, pineapple, and guava.

Healthy bones and teeth.

Healthy reproductive system.

Important for the coagulation of blood. Catalyst in carbohydrate metabolism, enabling pyretic acid to be metabolised and carbohydrates to release their energy. Serves as a

coenzyme-one that must combine with a portion of another enzyme to be effective-in the metabolism of carbohydrates, fats, and, especially, respiratory proteins. Works as a coenzyme in the release of energy from nutrients. Important in the formation and maintenance of collagen, the protein that supports many body structures and

Rickets. Sterility. Disorders in blood clotting. Beriberi; Disturbances, impaired sensory perception, weakness, periods of irregular heartbeat, and partial paralysis. Skin lesions.

Pellagra Diarrhoea,

mental confusion, irritability, and, when the central nervous system is affected, depression and mental disturbances. Scurvy; Bleeding gums Page 6 Fb: 2011 SPM Tips/Ramalan/Soalan Bocor (Public page)

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7. Fibre

plays a major role in the formation of bones and teeth.

Fibre is mainly cellulose from plant cell walls. Humans cannot digest fibre, but it is important because it helps food to pass from the gut, and prevents constipation. Food rich in fibre are whole meal bread, bran, cereals, fresh fruit and vegetables.

Food Tests

1) Test for Starch: with Iodine solution. If result is positive, a blue-black

precipitate forms.

2) Test for Glucose: with Benedict’s Solution and the mixture is heated. If the result is positive, an orange brown solution forms.

3) Test for Proteins: with Copper Sulphate and Sodium hydroxide. A purple colour forms if the tested food contains proteins.

4) Test for Fats: with Ethanol (alcohol) A milky white solution forms in presence of fat.

5) Test for Vitamin C: with DCPIP. A blue to a colourless liquid forms in presence of vitamin C.

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2 E

NZYMES

Enzymes are biological catalysts. A catalyst enhances the speed of a chemical reaction. Thus, enzymes are catalysts, which enhance the speed of the chemical reactions taking place in the body.

Properties of Enzymes

Enzymes are proteins, therefore, they become denatured by heat, which means that when heated above 40o

C, they change shape and do not work anymore. When the temperature is lower than normal, enzymes become inactive. Enzymes are specific,

which means that every enzyme catalysis only one type of food substance, for example, the enzyme amylase catalysis only starch, and does not take part in any other chemical reaction involving another food substance.

Enzymes do not take part in the proper chemical reactions (they do not react), they just enhance the speed, and this property makes them used over and over again.

An enzyme catalysis a reaction involving a substrate; the particular nutrient the enzyme acts on. When the reaction is complete, a product is produced. An example is

amylase acting on starch. Amylase, which is an enzyme, acts on its substrate (starch), to produce a product (maltose), which is a simpler type of carbohydrate.

The rate of productivity by enzymes is very affected by temperature and by pH. The

graph shows the rate of the activity by the enzymes in relation to temperature. The rate increases slowly when the temperature rises between 10o

C to 40o

C, but when the temperature rises further, activity decrease drastically, because enzymes are being denatured.

Effect of Temp. on Enzymes 6 5 4 3 2 1 0 mg of products per minute 10 20 30 40 50

Temerature in degrees celcius

4541/1  m  g  of  p  ro  du  ct  p  er  m  in  .

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The graph here below shows the sensitivity of enzymes to pH. It is a bell-shaped graph, showing that the enzymes work best that at their optimum pH, which in this case is pH 2. An example: Amylase acts on Enzyme 12 10 8 6 4 2 0

Effect of Temp. on Enzymes

0 0.5 1 2 3 3.5 4 pH Starch to produce Substrate activity of enzyme Optimum pH maltose Product Enzyme

The Lock and Key Theory

The lock and key theory is how scientists believe enzymes catalyze their substrate. It is shown in this

diagram. The substrate approaches the enzyme, then the substrate docks into the active site, where the reaction takes place. After the reaction, the enzyme releases the products.

Substrate Active Site Reaction taking place Products leave active site  ac  ti v  it y  o  f e  nz  ym  es

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Economic Important of Enzymes

Enzymes can be artificially made and used in Biological washing powders. These washing powders contain enzymes that work at a suitable temperature (e.g. 40o

C) and dissolve food stains from fabrics. They are specific to particular stains.

Protease is used for tenderising meat and removing hair from hides. Amylase is used to covert starch to sugars to make syrups and juices.

Enzyme Inhibitors

There are some poisons, such as cyanide and arsenic that block the enzymes’ active site, therefore the substrate cannot enter the active site and the reaction doesn’t take place. Certain pesticides block the active site of pests’ enzymes so that its respiratory system stops working and the pest dies.

Dentition

The teeth are made of hardest substance found in the body. Humans have 4 types of teeth:

1) Incisors: Adapted for cutting food. 2) Canines: for holing and tearing.

3) Premolars: For chewing and grinding food. 4) Molars: For chewing and grinding food.

Humans aged 6 months begin to grow 20 milk teeth (baby) teeth. Once he or she is an adult, 32 permanent teeth will be developed.

The tooth is made up of 2 sections, an exposed Crown and the Root which is embedded in the gum. The enamel (calcium phosphate: CaPO3) is the upper part of

the crown. It is very hard. Then beneath it there is the dentin. The tooth is primary made of dentin, which is a substance, similar to bone but harder. The central region of the tooth is the pulp cavity. It contains the pulp, which is composed of connective tissue with blood vessels, nerves etc. the pulp is connected to the blood capillaries, which give nutrients and oxygen to the dental cells.

Tooth decay (dental caries) is caused by bacteria in the mouth which produce acids

to digest food stuck in and between the teeth.

To prevent tooth decay, varies activities must be regularly done:

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V Brushing teeth with a fluoride toothpaste V Regular visits to the dentist

V X-rays of the jaw to ensure that no cavity is being developed where the dentist cannot see

V Use tooth floss

V Wash mouth with a suitable mouth wash

Herbivores have different a dental system since they eat only vegetable matter. In herbivores, there is a gap called diastema between the incisors and the molars. Instead of the upper incisors, herbivores have a hard pad to pull leaves and grass out

of the branches or soil. They have no canines and molars have a flat surface. Their teeth have an open root, which means that they grow continuously. Carnivores’ molars have cusps, to ensure that food is better chewed. They have canines, and

upper incisors, while teeth have a closed root unlike herbivores. The following article shows more clearly the difference between carnivores and herbivore dentition.

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Diastema

Meat Eaters and Plant Eaters

In carnivores (right), the front of the skull has a pair of enlarged canine teeth and the lower jaw moves only in an up-and-down direction, which assists with the capture and holding of prey. In herbivores (l t), the canine teeth are absent and the premolars and

molars are well developed. The jaw construction also allows for the

sideways movement of the lower jaw in relation to the upper jaw, which helps to provide the grinding motion necessary for breaking up plant materi s into a state suitable for swallowing and digestion.

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3: F

EEDING Feeding can be divided into 4 types:

1. Saprophytic: Saprophytic organisms such as fungi and some bacteria (called

decomposers) that feed on dead decaying matter. Saprophytes are useful to

the environment because they recycle nutrients.

2. Parasitic: When parasitic organisms feed on or in another organism harming it.

3. Holozoic (heterotrophic): Animals feed heterotrophically, because they must

search for their food. Herbivores eat vegetable matter and have special

bodily structures to help them digest cellulose. Carnivores eat meat and are

usually predators. Omnivores, such as humans eat both meat and vegetable matter.

4. Holophytic (autotrophic): Plants feed with this type of feeding. They are able to make their own food by photosynthesis.

Holozoic Nutrition

The digestive system can be divided into various stages, but it is basically divided into 5 main stages:

1. Ingestion: food is ate, chewed and mixed with saliva.

2. Digestion: Begins from the mouth by salivary amylase (starch-breaking enzyme) and continues till the duodenum (first part of the small intestine), were enzymes break down food into simpler soluble products (Glucose, amino acids, fatty acids and glycerol), stage by stage, and prepares nutrients for absorption.

3. Absorption: the blood absorbs soluble products in the ileum (second part of the small intestine).

4. Assimilation: the nutrients are then assimilated (taken to) various organs around the body.

5. Defecation (Egestion): Undigested matter such as fibre is egested (moved

out) of the body. [Do not mix excretion with egesting or defecation! Excretion is the removal of waste products made by chemicals reaction within the cells;

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Now the 5 stages will be examined more in detail.

Ingestion

The first stage, ingestion, is the actual eating of food, i.e. using teeth.

Digestion

The second stage, digestion begins from the mouth. It is divided into 2 other parts:

1. Physical digestion: teeth crush food to increase surface area for enzyme action to break down food.

2. Chemical digestion: food is mixed with enzymes and digestive juices to breaks down food into the 3 soluble products of digestion. The chemical digestion continues till the duodenum. Chemical digestion also begins in the

mouth. When food is mixed with saliva, the enzyme salivary amylase starts breaking down starch into maltose

Chemical Digestion in more detail

Saliva contains salivary amylase, mucus, water and lysozyme (which is also an enzyme) that kills bacteria. The food, after that it is chewed, forms into a bolus, (a

ball) of mixed food with saliva that goes down the oesophagus (or gullet). Between

the mouth and the oesophagus there is the epiglottis. The epiglottis is a flap that closes so as to prevent food entering the windpipe (trachea).

The oesophagus is made up of two layers of muscle cells. On layer is circular while

the other runs lengthwise. When they contract and relax, they push down food downwards in a movement called peristalsis. Therefore food does not go down by

gravity (astronauts would NOT survive in space if it would!). The food is pushed down to the stomach.

The stomach is made up of layers of muscles that make it twist and squeeze so that

food is mixed with gastric juices. There are about 35 million gastric glands that produce gastric juice. Gastric juice contains:

∑ Pepsinogen: an inactive form of pepsin that is then activated by the

hydrochloric acid.

∑ Pepsin: digestive enzyme, which breaks down proteins into smaller polypeptides.

∑ Mucus: Protects the stomach wall from being digested by the enzymes (prevention of self-digestion).

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∑ Hydrochloric acid (chemical formula HCl) kills bacteria and provides and

acidic, optimum pH for pepsin to work.

After 3 to 4 hours of digestion, food becomes chyme. At intervals it is passed into the

small intestine. The first part of the small intestine is called the duodenum. The

duodenum receives digestive juices for 3 different places: intestinal wall, pancreas and the liver.

From the intestinal wall, mainly 5 enzymes are produced: 1. Trypsin: breaks down polypeptides into dipeptides. 2. Maltase: breaks down maltose into glucose.

3. Lipase: breaks down fats (lipids are liquid fats) into fatty acids and glycerol. 4. Peptidases: breaks down dipeptides into amino acids

5. Sucrase: breaks down sucrose into glucose

These enzymes are summarised below in the following table: Enzymes from the

Substrate Product Intestinal Wall Trypsin Maltase Lipase Peptidases Sucrase polypeptides maltose fats dipeptides sucrose dipeptides glucose

fatty acids and glycerol amino acids

glucose

From the pancreas mainly 4 chemicals are produced:

1. Sodium hydrogen carbonate (NaHCO3): neutralizes acids from the stomach

and provides alkaline pH in the duodenum.

2. Trypsin: breaks down polypeptides into dipeptides. 3. Pancreatic amylase: breaks down starch into maltose. 4. Lipase: Breaks down fats into fatty acids and glycerol. These chemicals are enlisted here below:

Chemicals from the

Function / Substrate Product

Pancreas Sodium hydrogen carbonate

neutralizes acids from the stomach and provides

alkaline pH in the duodenum

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Biology Form 4 Notes (2003-2004)2005 Jordan Mifsud (4.8) 5.8 Trypsin Pancreatic amylase Lipase polypeptides Starch Fats dipeptides maltose

Fatty acids and glycerol

From the liver, the duodenum receives no enzymes, but gets bile. Bile is a green chemical, which helps to break down large fat molecules for lipase to act on it: this

process is called emulsification. It has a detergent effect, and it is stored in the gall

bladder and it is secreted from the gall bladder to the duodenum through the bile

duct. Digestion ends here.

Food has been all broken down into their soluble products, glucose, amino acids,

fatty acids and glycerol. They can be now absorbed into the blood stream from the

ileum.

The liver

The liver is the largest internal organ in vertebrates. It does the following functions:

synthesis of proteins, immune and clotting factors, and oxygen and fat -carrying substances. Its chief digestive function is the secretion of bile, a solution critical to fat

emulsion (emulsification) and absorption. The liver also removes excess glucose from circulation and stores it until it is needed. It converts excess amino acids into useful

forms and filters drugs and poisons (alcohol, pills Fb: 2011 SPM Tips/Ramalan/Soalan Bocor (Public page)etc) from the bloodstream,

neutralizing them and excreting them in bile. The liver has two main lobes located just under the diaphragm on the right side of the body.

The Ileum

The ileum is a very long part of the gut so that absorption takes places efficiently. Here, soluble products: glucose, amino acids, fatty acids and enter glycerol enter the

blood stream through millions of small finger-like structures called villi. The villi are tiny, to increase surface area for absorption. Each villus is covered with tiny ‘hairs’ called microvilli, that are actual villi but smaller, like root hairs on a root in plants. Villi have a thin lining and a good blood supply to allow blood to absorb the soluble nutrients. Food passes through the intestine with the help of muscular contraction (peristalsis) of the intestinal wall, which is also moist to allow food to pass well and to enhance the speed of absorption.

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Biology Form 4 Notes (2003-2004)2005 Thin Epithelium Jordan Mifsud (4.8) 5.8 Lacteal (absorbs fatty acids and glycerol

The villus’s structure is shown here;

Blood Vessels (absorb

glucose and amino acids)

Glucose and amino acids are absorbed by the blood capillaries, which are very thin blood vessels. Fatty acids and glycerol, being large molecules are absorbed by the lacteal first before draining into the blood stream.

The Large Intestine

The large intestine is divided into the colon and rectum. The colon is the part where water is absorbed. In the rectum, faeces (undigested food such as fiber) are stored until it is egested out of the body through the anus, within 24-48 hours after eating. The rectum wall is covered with a layer of mucus to ease the passage of faeces. This process is called defeacation.

The Caecum and the Appendix

The caecum and the appendix are vestigial organs, i.e. they do not have any known function in humans. In herbivores called ruminants, (such as rabbits) the caecum and appendix contain cellulose-digesting bacteria that produce the enzyme cellulase to digest cellulose in plant cells.

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Digestion in Herbivores

Herbivores such as cows, sheep and horses are called ruminants because they contain

a special digestive system. They have a special type of dentition, different from carnivorous dentition, to allow them to extract grass from soil easily. Their small intestine is about 40 meters long, to allow them to digest cellulose completely, before it reaches the end of the gut.

Their gut contains cellulose-digesting bacteria. These bacteria produce the enzyme

cellulase that catalysis the reaction that breaks down cellulose into soluble sugar

(glucose). The bacteria gain shelter and protection as well as food from the ruminants so their relation is a mutualistic one (both benefiting from one another).

These bacterial are housed in the caecum and appendix, so in the ruminants, they are not vestigial organs as in humans.

Ruminants have a special type of stomach called rumen. The rumen is a large

stomach that contains 3 other chambers. While the ruminant is grazing, grass is swallowed and enters the rumen. When the animals stops eating, it regurgitates the

grass (brings the already swallowed food back to its mouth), little by little to allow it to be chew and swallowed properly and then the food enters into the other 3 chambers to further digest the food before it goes into the small intestine.

The following article helps you understand how the ruminant’s digestive system works.

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Four-Chambered Stomach

True ruminants have four-chambered stomachs. They include sheep, domestic cattl goats, antelopes, deer, and giraffes.

reserved.

More information about the Liver

Liver

Hepatic Vein Hepatic portal vein

Hepatic Artery

Gut

The liver receives blood mixed with the soluble products of digestion from the hepatic portal vein. The liver receives blood rich in oxygen from the heart through

the hepatic artery. Then the blood leaves the liver through the hepatic vein which also carries a lot of heat since inside the liver, a lot of chemical reactions occur.

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ESPIRATION

What is Respiration and Why do we need it?

Respiration is a chemical reaction catalysed by enzymes. It takes place in each and every mitochondria of the cells. Respiration is done to obtain energy needed by the body. For vital functions to take place, the body needs energy. It also needs energy to keep a constant body temperature and to transport chemical messages. Plants need energy for active transport to take place.

Gas exchange

Differences between respiration and breathing:

Respiration is carried out in all cells to obtain energy.

Breathing is the exchange of gases, in case of humans and other organisms, the removal of carbon dioxide and obtaining oxygen.

In large organisms such as mammals, respiratory surfaces are required for gas exchange (breathing, not respiration) to take place efficiently. In humans, like all mammals, lungs are used for this purpose.

There are two types of respiration: Aerobic (oxygen involved) and anaerobic (no oxygen involved).

Anaerobic Respiration

Anaerobic means without oxygen, and thus this type of chemical reaction involves only sugars (obtained from digestion of food). Energy is released by the chemical breaking of bonds in organic molecules (containing carbon) present in sugars and other carbohydrates, obtained from digestion. There is more than one type of anaerobic respiration; it depends on the organism.

One very common type of anaerobic respiration is alcohol fermentation represented in this equation below:

H O

C

612 6



2 CO

2



2C

2

H

5

OH

energ

y

kJ

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This type of reaction (alcohol fermentation) is done by yeast. As it produces alcohol, it is important for world economy for the production of beer, wine and

other alcoholic drinks. Yeast’s most important function is surely in the production

of bread. Anaerobic

respiration is also important Fb: 2011 SPM Tips/Ramalan/Soalan Bocor (Public page)

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anaerobic bacteria produce lactic acid, which is used to make butter, yoghurt cheese and other dairy products. Some other types of bacteria produce methane

gas (CH4), a flammable gas used for cooking and fuelling machinery, lighting, and

used in the production of hydrogen, hydrogen cyanide, ammonia, ethyne, and formaldehyde.

Anaerobic respiration takes place in humans as well. During strenuous exercise, blood vessels cannot provide enough oxygen for muscle cells to do proper aerobic respiration; in this case, anaerobic respiration takes place in the muscles. In these reactions, lactic acid (slightly poisonous) is produced and can cause cramps. After the exercise, the lactic acid is converted into carbon dioxide and water by oxygen. This whole process is known as oxygen debt.

Making Bread

This is a simple method to make bread.

 Some yeast and sugar and mixed with a little warm water.

 After some time, the mixture froths and this indicates that yeast cells are becoming active.

 The yeast liquid is mixed with flour, salt and warm water to make the dough.

 The dough is then kneaded for a few minutes to ensure that all the yeast and the rest of the ingredients and evenly distributed.

 The dough is left in a warm place for fermentation is take place. Yeast produces alcohol and carbon dioxide and this gas causes the dough to rise. After an hour, the dough should have doubled its size.

 The dough is baked in a hot oven and yeast cells die. Alcohol, with a low boiling point evaporates almost immediately and the carbon dioxide leaves the bread with small holes inside it.

Aerobic respiration

Aerobic respiration is the respiration, which involves oxygen. An example of

aerobic respiration is shown here in this equation:

C6H12O66O2

 

6CO H O [energy]

 2 2 2880 glucos e oxygen carbon dioxed water ( KJ)

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The enzymes catalyze the oxidation of glucose to form carbon dioxide and water. 2830kJ of energy are released by oxidizing 180 grams of glucose. Energy

is stored in the body as ATP (adenosine triphosphate), because glucose alone

does not provide energy.

As enzymes catalyse this reaction, it is controlled also by temperature, so when the body temperature rises above 40o

C, respiration slows down because heat denatures enzymes.

The lungs

The lungs are the respiratory surface of mammals, birds, reptiles and some amphibians. Voice box (larynx) Rings of Cartilage Pleural membrane Pleural fluid Alveoli Intercostals muscles Ribs

Space for Heart Pulmonary Artery Pulmonary Veins

The Air Passage

Trachea

Bronchus

Bronchioles, terminal bronchioles

Diaphragm

The air passes through a number of passages before it goes to the bloodstream to be used up. First the air passes through the nose and through the trachea, which is surrounded by rings of cartilage to stay stiff. The nose and trachea have special cells on their walls. There are some cells with cilia; hair-like structures that are continuously beating up and down. These trap germs as well as dust from the air.

Another type of special cells in the epithelium of the nose and trachea are the

mucus-secreting cells. These have a hole in them from where mucus is secreted.

After the trachea, the air passes through the bronchi, bronchioles, terminal

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bronchioles and finally to the air sacks, or alveoli. These alveoli are shown here Blood capillary filled

with oxidized blood (oxy-hemoglobin

Alveolus

Blood capillary with

Thin water deoxidized blood

film in this diagram.

Oxygen and carbon dioxide are exchange in the alveoli by diffusion. Numerous alveoli create a large surface area for gas exchange. Oxygen is carried in the red

blood cells (rbc) while carbon dioxide is carried in the plasma as Hydrogen Carbonate (HCO3-) ions.

The alveoli are adapted for gas exchange by a number of factors:

1. They have a thin film of water to ensure good and fast gas exchange by diffusion surrounds the alveoli. In fact, some of this water evaporates and there is always some water vapour in our exhaled breath.

2. Alveoli are surrounded by a lot of blood capillaries 3. Blood capillaries are very thin to allow diffusion. 4. There are many air sacks for a large surface area.

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While breathing in, the rib cage moves upwards and outwards, the diaphragm flattens and the volume in the chest increases. Since the volume increases the

pressure decreases and the air is drawn into the lungs.

While you exhale, the rib cage moves inwards and downwards, the diaphragm relaxes (dome shaped) and the volume in the chest decreases. Since the volume

decreases pressure increases and the air is expelled out of the lungs.

Smoking and its Negative Effects

Cigarettes contain 3 harmful chemicals: 1) Tar, 2) nicotine and while it is burning it produces 3) carbon monoxide. Apart from these, the cigarettes contain many other chemicals. Some of these are irritants. Irritants and chemicals that annoy the lungs. Other chemicals are carcinogens; may cause cancer.

The smoke produced by the cigarettes is very harmful, it affects the epithelium in two ways: it irritates the goblet cells, making them produce more mucus. Secondly, it slows down, or even stops the beating of the cilia, so that they can no longer sweep out the mucus. Coughing can only clear the build up of mucus in the lungs. This is known as smoker’s cough.

Some diseases caused by cigarettes are bronchitis, emphysema and lung cancer.

Bronchitis: This disease results as much of the epithelium is damaged and destroyed by the cigarettes’ smoke and irritants. Germs and irritants penetrate deeper into the lung tissue and so the body’s defence cell move into attack. Their remains, along with the mucus make up phlegm, which must be coughed and spat

everyday. Bronchitis causes more than a 1000 deaths every year and it is a disease, which mostly causes loss of workdays.

Emphysema: Emphysema causes the walls between alveoli become torn and

broken, while the others left become thicker. This causes the lungs to have a smaller surface area for gas exchange. The sufferer coughs and wheezes and struggles for breath. This illness can cause permanent disability and eventually death.

Lung Cancer: Carcinogenic chemicals (chemicals which can cause cancer) cause lung tissue to divide in an uncontrolled manner. This growth is called a

tumour or cancer. The tumour spreads through the lung destroying other healthy

tissue. Cancerous cells may go into the bloodstream and secondary tumour may arise. This disease, although it can be treated if detected in the early stages, it is

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usually found too late and the victim dies.

Other Lungs diseases

Pneumonia: Certain bacteria and viruses cause this illness. These cause the alveoli to get filled with fluid and cell debris. Oxygen starvation results since a

much of the alveoli block gas exchange.

Tuberculosis (TB): It is cause by a bacillus (pathogenic bacteria). This disease

can be treated and cured nowadays. The germs doesn’t do much harm but sometimes, the bacillus may spread out through the lungs causing sever damage.

Dust Diseases: These diseases are caused when large amounts of dust are breath during work. Stonecutters, miners and asbestos workers may catch illnesses such as silicosis, pneumoconiosis and asbestosis respectfully. Special precautions must be taken because once caught, these diseases are incurable.

Air Pollution

The air is polluted by mainly 5 different gases: carbon dioxide, carbon monoxide, sulphur dioxide, nitrogen dioxide and ozone. 4 of them are poisonous for the hu man body, namely carbon monoxide CO, sulphur dioxide SO2, nitrogen dioxide NO2

and ozone O3.

Carbon dioxide CO2 is not a toxic gas in moderate concentrations, but it contributes

to global warming, thus it is a greenhouse gas (traps the sun’s heat, causing global temperature to rise, changing climate and endangering animal and plant species).

CFC’s (chlorofluorocarbons) although not considered pollutants, convert ozone in the protective ozone (O3) layer back into oxygen (O2), thus it makes a hole in this layer,

letting harmful ultraviolet rays from the sun penetrate the atmosphere, causing skin cancer.

Sulphur Dioxide and Nitrogen Dioxide rise from industrial effluent and car exhaust.

They are both toxic gases and in order to block nitrogen dioxide from escaping into

the air, cars should be equipped with catalytic converters. These devices convert nitrogen oxides and carbon monoxide into carbon dioxide, harmless ni trogen and water, with the help of rare catalysts.

Carbon monoxide is also produced by cars and other burning sources that are not properly ventilated such as gas heaters and fire places in enclosed rooms. It is a

harmful gas because it combines with the blood, preventing it from absorbing

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Certain electrical machinery and photocopiers produce ozone (O3) gas. Although

ozone is useful in the ozone layer, which is 20-50 km above sea level, it is highly

poisonous and can contribute to acid rain.

Glossary For Half Yearly Terms To Study

Nutrition: the study of food.

Basic Nutrients: The 7 basic food substances that are: Carbohydrates, Fats,

Proteins, Vitamins, Minerals, Fibre and Water.

Carbohydrates: 1 of the bulk material of which food is made of. An organic substance from which the body gets energy.

Fats: Made up of fatty acids and glycerol; another bulk material found in food.

Proteins: Substances made up of carbon, hydrogen, oxygen, nitrogen and sometimes sulphur. Used for growth and repair or tissue.

Vitamins: Organic substances needed in small amounts by the body. Some are co- enzymes and other help to prevent illnesses.

Minerals: Important substances needed in small quantities to prevent illnesses.

Fibre: An insoluble, non-digested substance used to sweep out undigested food out of the body; roughage

Water: Very important chemical; the most abundant compound in the Universe and in the body.

Sugars: Carbohydrates used to get energy.

Glucose: C6H12O6 Final product of digestion of carbohydrates.

Fructose: A sugar found in fruit. Sucrose: Table sugar.

Lactose: Found in milk.

Maltose: Found in barley grains.

Starch: Found in bread, potatoes, rice and cereals. A chemical used by plants to store food; an insoluble polysaccharide.

Monosaccharides: Sugar with one glucose molecule. Fructose is also a monosaccharides.

Disaccharides: Sugars with more than one glucose molecule attached together by

bonds.

Polysaccharide: three or more sugar molecules are bonded together; insoluble. Glycogen: The chemical used by animals to store food.

Glycerol: Part of the fat molecule.

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Fatty acid: There are 3 fatty acids in a fat molecule. Amino Acid: The final product of digestion of proteins. Peptide bonds: the bond by which amino acids are attached.

Dipeptide: 2 amino acids attached together by peptide bonds.

Polypeptides: 3 or more amino acids attached together by peptide bonds.

Peptide Bonds: Bonds attaching amino acids together to form dipeptides and polypeptides.

Foods rich in Protein: Meat, eggs, nuts.

Urine: The body’s excretorial waste.

Calcium: Found in Milk, cheese, mineral water; used for growth and repair of bone and cartilage tissue. Prevents rickets; malformed bones.

Iron: Found in tomatoes, liver and kidneys. Part of haemoglobin in rbc. Prevents anaemia (tiredness, headaches).

Phosphorous: Found in many foods; important for bones and teeth. Sodium: Found in salt. Prevents cramps.

Iodine: Found in sea food, and drinking water. Helps to prevent goitre.

Vitamin A: Found in liver and carrots. Prevents night blindness (exophthalmia). Vitamin D: Found in fish liver oil. Prevents richets.

Vitamin E: Found in milk, egg yolk, lettuce. Prevents sterility.

Vitamin K: Found in cabbage, spinach, fish liver. Important for blood coagulation.

Fat soluble Vitamins: Vitamins A, D, E, K.

Water Soluble Vitamins: Vitamins B1, B2, B6, C.

Vitamin B1: Found in Pork, eggs, leafy green vegetables. Prevents beriberi

(weakness, irregular heartbeat, partial paralysis)

Vitamin B2: Found in liver, milk, dark green vegetables. Prevents Skin lesions.

Niacin (B6): Found in liver, poultry, canned tuna. Prevents pellagra (metal confusion, diarrhoea)

Vitamin C: Found in citrus fruit. Prevents Scurvy. (bleeding gums) Enzymes: Biological catalysts.

Denatured: Proteins like enzymes get denatured by heat (loses its properties). Substrate: The food on which an enzyme acts.

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Biological Washing Powders: Washing powders that contain enzymes.

Protease: An enzymes used for tenderising meat.

Amylase: Found in saliva and duodenum. Used in industry to convert starch to sugars to make syrups and juices.

Cyanide: Enzyme inhibitor. Arsenic: Enzyme inhibitor.

Incisors: Teeth adapted for cutting food. Canines: for holing and tearing.

Premolars: For chewing and grinding food. Molars: For chewing and grinding food. Crown: The upper part of the tooth. Root: The lower part of the tooth. Dental Caries: Tooth decay.

Cusps: ‘hills’ on the teeth of carnivores and omnivores.

Saprophytic: When saprophytic organisms such as fungi and some bacteria that feed on dead decaying matter. Saprophytes are useful to the environment because they recycle nutrients.

Parasitic: When parasitic organisms feed on or in another organism harming it.

Holozoic (heterotrophic): Animals feed heterotrophically, because they must search for their food. Herbivores eat vegetable matter and have special bodily structures to help them digest cellulose. Carnivores eat meat and are usually predators. Omnivores, such as humans eat both meat and vegetable matter.

Holophytic (autotrophic): Plants feed with this type of feeding. They are able to make their own food by photosynthesis.

Ingestion: food is ate, chewed and mixed with saliva.

Digestion: Begins from the mouth by salivary amylase (starch-breaking enzyme) and continues till the duodenum, were enzymes chemically break down food into simpler soluble products, stage by stage, and prepare nutrients for absorption. Absorption: the blood absorbs soluble products.

Assimilation: the nutrients are then assimilated (taken to) various organs around the body.

Defecation (Egestion): Undigested matter such as fiber is egested (moved out) of

the body. [Do not mix excretion with egesting or defecation! Excretion is the removal of waste products made by chemicals reaction within the cells; e.g.

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excreting urine.

Physical digestion: teeth to increase surface area for enzyme action to break

down food.

Chemical digestion: food is mixed with saliva and salivary amylase breaks down

some starch from the food (if there is) into maltose. The chemical digestion continues till the duodenum.

Lysozyme: Chemical found in the saliva used to kill bacteria. Oesophagus: Gullet.

Pepsinogen: an inactive form of pepsin that is then activated by the hydrochloric acid.

Pepsin: digestive enzyme, which breaks down proteins into smaller polypeptides. Mucus: Protects the stomach from being digested by the enzymes.

Hydrochloric acid (HCl acid): kills bacteria and provides and acidic pH for pepsin to work.

From the intestinal wall:, Mainly five enzymes are produced:

Trypsin: breaks down polypeptides into dipeptides. Maltase: breaks down maltose into glucose.

Lipase: breaks down fates (lipids) into fatty acids and glycerol. Peptidases: breaks down dipeptides into amino acids

Sucrase: breaks down sucrose into glucose

From the pancreas mainly 4 chemicals are produced:

Sodium hydrogen carbonate (NaHCO3): neutralizes acids from the stomach and

provides alkaline pH in the duodenum. Trypsin: breaks down starch into maltose.

Pancreatic amylase: breaks down starch into maltose. Lipase: Breaks down fats into fatty acids and glycerol.

Liver: The largest and very important internal organ found in the body. Among its

functions, it produces bile, breaks down drugs and alcohol, and converts the final products of digestion into glycerol for storage. The liver cells help the blood to assimilate food substances and to excrete waste materials and toxins, as well as products such as steroids, oestrogen, and other hormones. The liver also stores

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iron, vitamin A, many of the B-complex vitamins, and vitamin D.

Detoxification: One of the functions of the liver, where the liver breaks down

drugs.

Deamination: The destruction of red blood cells so that the body forms new ones. This function is carried out by the liver, in fact, the liver is a source of iron.

Duodenum: The first part of the small intestine. It continues digestion of food and

it receives enzymes from the intestinal wall and from the pancreas. It receives bile that the liver produced from the gall bladder.

Gall Bladder: An organ used to store bile. Bile: A green chemical used for emulsification.

Emulsification: The process by which bile does detergent action on lipids. Fat

molecules are too large to be absorbed by the blood so it is broken down into smaller molecules by the bile.

Hepatic Artery: The artery that gives blood from the heart to the liver.

Hepatic Portal Vein: The vein that transports blood rich in soluble products of digestion from the ileum to the liver.

Hepatic Vein: The vein that transports blood from the liver to the heart.

Ileum: A long part of the gut where digestion stops and absorption starts.

Absorption is done by the villi surrounding its walls. It ends in the large intestine. Villi: Small structures found on the walls of the ileum where absorption stakes place. There are millions of them to ensure that all nutrients have been absorbed.

Microvilli: Even smaller villi on the large villi in the ileum.

Mucus-Secreting Cell: Cells present in the trachea, nose, stomach wall, the intestinal wall and on the epithelium of the villi, also called goblet cells.

Epithelium: The first thin layer of cells of the villi and other small structures in the body.

Lacteal: The structure found in the villi that absorbs fat droplets.

Venule: The vein that carries amino acids and monosaccharides. They are found in the villi.

Arteriole: The vein that transports blood in the villi.

Appendix: A vestigial organ located the between the ileum and colon. Caesium: Another vestigial organ located near the appendix.

Vestigial Organ: An organ that has no known functions. Vestigial organs found in the body are the caesium and the appendix. Ancient human beings who ate

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mainly vegetable matter probably used these organs. Then, by evolution, these organs ceased from being used. They were home to cellulose-digesting bacteria.

Large Intestine: Part of the alimentary canal. It is dividing into the colon and rectum.

Colon: The first part of the large intestine where water and fluid are absorbed. It ends in the rectum.

Herbivores: Vegetable eating animals.

Ruminants: Herbivores with a special type of stomach called a rumen.

Cellulose: A cellulose-digesting enzyme produced by certain bacteria found in

herbivores.

Mutualistic Relationship: A type of relationship between organisms where both

animals are benefiting from each other. An example of such relationships is the relationship between the cellulose-digesting bacteria in the caesium and appendix of ruminants.

Rumen: A large stomach with 3 compartments found in ruminants.

Regurgitation: Ruminants bring the food they have already eaten and swallowed back to their mouth to continue chewing it.

Respiration: A chemical reaction catalysed by enzymes where (in case of aerobic respiration) oxygen combines with glucose to form carbon dioxide, water and energy.

Aerobic: A type of respiration where oxygen is involved.

Anaerobic: A type of respiration that does not involve oxygen and doesn’t

produce as much energy as aerobic respiration.

Mitochondria/Mitochondrion: An organelle found in all cells that do respiration.

Gas exchange: The process where oxygen is absorbed by the blood and carbon

dioxide is exhaled out of the body. Don’t mix gas exchange with respiration. Respiration is a chemical reaction while gas exchange is just the exchange of

gases.

Organic Molecules: Molecule containing carbon.

Alcoholic Fermentation: A type of anaerobic respiration where alcohol is a product of the chemical reaction.

Lactic Acid: An acid produced in muscle tissues during strenuous exercise when

there is lack of oxygen.

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when after exercise the body continues breathing heavily so re gain all the oxygen needed by the muscle cells to break down lactic acid in carbon dioxide and water.

Aerobic respiration: A type of respiration where oxygen is involved. An example of this type of respiration is alcoholic fermentation.

Lungs: Major organs in some animals needed for gas exchange.

Trachea: Otherwise called windpipe. The second pipe from where air passes and

is filtered by cilia and mucus secreting cells. Rings of cartilage to make it stiff surround this structure and so that it doesn’t get bent.

Bronchus: One of the pipes from which air passes before going inside the lungs. There are two bronchi and they are attached to the trachea. Rings of cartilage to make it stiff surround these structures.

Alveoli: Also called air sacks. The place where the actual gas-exchange takes place. Tiny structures surrounded by many blood vessels to ensure that gas exchange takes place rapidly and efficiently.

Pleural Membrane: A thin membrane that covers the inside of the ribs and the

outside of the lungs. A film of moisture between the two layers lets them slide easily over each other as the lungs move.

Intercostals: Muscles between they ribs that contract and relax during inhalation and exhalation.

Inhalation: Breathing in. Exhalation: Breathing out.

Breathing: A series of movements made by intercostals, the rib cage and pectorals to enable the air to get into the lungs. These movements are shown here

in this diagram.

Ribs: Bones surrounding the lungs.

Bronchioles: Small pipes from which air passes. These are found inside the lungs.

Pulmonary Vein/Artery: Blood vessels from which blood passes from and into

the heart. They are connected to the lungs and the heart.

Diaphragm: A muscle present only in mammals to ease inhalation and exhalation. This muscle is found under the lungs.

Plasma: Part of the fluid in blood.

Hydrogen carbonate ions: Carbon dioxide is transported in the blood by this ion.

HCO3-.

Blood capillaries: Very, very small blood vessels that surround alveoli. They are

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very thin and tender and are found in many other places in the body. Tar: A chemical found in cigarettes.

Carbon monoxide: A poisonous gas released by lightened cigarettes.

Nicotine: Colourless, oily, liquid alkaloid, C10H14N2 that constitutes the principal

active chemical constituent of tobacco.

Epithelium: A layer of cells that serves as a protective covering over a surface,

such as the outside of an organ or the lining of a cavity wall in the body.

Goblet Cells: Mucus secreting cells.

Diseases caused by smoking: Bronchitis, Emphysema and Lung Cancer Other lung Diseases: Pneumonia, TB (Tuberculosis) and Dust Diseases.

Poisonous gases in the air: Carbon monoxide, sulphur dioxide, nitrogen dioxide,

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Part 2 of Biology Notes (Rest of syllabus)

T

OPIC

5: H

OMEOSTASIS

Introduction

KEEPING A CONSTANT BODY ENVIRONMENT

There are mainly 4 organs that help the body to keep a constant body environment: the lungs, the liver, the skin and the kidneys.

Lungs

The lungs are responsible to exchange of gases in the body. They exchange carbon dioxide with oxygen from the air. Also, the lungs must provide the oxygen

with a temperature of around 37 degress Celsius so that chemical reactions involving oxygen can take place.

The Liver

The liver is a major organ in the human body that makes a large amount of

chemical reactions that produce heat (chemical reactions that produce heat are

called exothermic).

Therefore, the liver produces all the necessary heat for the body to keep its internal temperature around 37o

C.

Skin

The skin is responsible for transferring excess heat from inside the body to the outside environment. For that reason it is one of the organs that does homeostasis.

It also protects the body from germs.

Kidneys

The kidneys are responsible for osmoregulation, i.e. to control the amount of water in the body, by filtering blood from salts, water and waste products (urea). Blood is involved and so the kidneys are also part of homeostasis, because blood transports heat and helps to keep the body at a constant temperature.

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The Excretory System

The excretory system is the system responsible for the disposal of waste material produced by the body --Urine. The major organs in the excretory system are the

kidneys. The body can survive with just one kidney, but with none, the person must use the kidney machine (explained in the following pages) or else he or she

dies. The function of the kidneys is to filter blood from urea (waste produced by

chemical reactions in the body) excess water, and excess salts. This process is

called ultra-filtration and it is done by nephrons (explained further in the

following pages)

The Kindey

The diagram below shows the kidneys, the bladder and blood vessels connected to it. Pyramid Pelvis Cortex Medulla Kidney Wall Renal Vein Renal Artery Urither

Renal Vein: The vein that transports blood OUT OF the kidneys. Blood in the renal vein is deoxidized or reduced (without oxygen) and filtered by kidneys, thus

it is clean.

Renal Artery: The artery that transports blood INTO the kidneys. Blood in the renal artery is full of oxygen but also full of waste (urea and salts) thus it has to be filtered.

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Ureters: Carry urine (urea, excess water, excess salts) into the bladder.

Bladder: The structure, which stores urine before it is excreted out of the body. Ring of Muscle: A ring of muscle that is kept closed before one goes to the toilet to excrete the urine. They control the passage of urine out of the body.

Urethra: The last structure from which urine passes before going out of the body.

Renal Vein Renal Artery Right Kidney Ureters Bladder Ring of Muscles Urethra Page 36 Fb: 2011 SPM Tips/Ramalan/Soalan Bocor (Public page)