biology spm chapter 6 form 4

(1)

CHAPTER 6

NUTRITION

(2)

What is Nutrition?



The entire process by which organism

obtain energy from food for growth,

maintenance and repair of damaged

tissues



Nutrient – the substances that are

required for the nourishment of an

organism

(3)

6.1 Type of Nutrition



Two main types:

1. Autotrophic

(4)

1. Autotrophic



A process in which organisms synthesise

organic substances from inorganic

substances



Autotroph = Auto – self, trophos – feed

(organism which can make their own food)



The source of energy for synthesising food

can be either light energy or chemical

energy.

(5)



The synthesis of food using light

energy – photosynthesis (photo –

light)



Photoautotroph – organisms which

produce organic molecules from

carbon dioxide and water using

sunlight as a source of energy



Example: green plants

(6)



The synthesis of food using chemical

energy – chemosynthesis (chemo –

chemical)



Chemoautotroph – organisms which

synthesise organic compound by

oxidising inorganic compound

(hydrogen sulphide and ammonia)



Example: certain bacteria

(7)

2. Heterotrophic



A type of nutrition in which organism

obtain energy through the intake and

digestion of organic substances.



Heterotroph =Hetero – other,

trophos – feed (organism that cannot

synthesis their own nutrients but

obtain the nutrients from other

organisms)

(8)



They may practice

a) Holozioc nutrition,

b) Saprophytism

(9)

- holo –like, zoon – animal

- The organism feeds by ingesting

solid organic matter which is

subsequently digested and

absorbed into their bodies

- Examples: humans, herbivores,

carnivores and some carnivorous

pitcher plants and Venus fly-traps

a) Holozoic nutrition

(10)

- The organism called saprophytes

- Feed on dead and decaying

organic matter

- Digest their food externally

before absorbing the nutrients

into their bodies

- Examples: bacteria, fungi

b) Saprophytism

(11)

- The organism called parasite

- Obtain nutrient from living on

(ectoparasites) or in (endoparasites)

the body of another living organism

(host)

- They absorbs readily digested food

from its host

- Examples: fleas (ectoparasites), lice,

worms (endoparasites), Rafflesia

plant

c) Parasitism

(12)

Test Yourself

1.

Differentiate between autotrophic and

heterotrophic nutrition.

A:

Autotrophic nutrition –

A process in

which organisms

synthesise organic

substances from inorganic substances

Heterotrophic nutrition -

A type of

nutrition in which organism

obtain

energy through the intake and

(13)

1.

Name two types of autotrophic

nutrition.

A:

Photosynthesis and chemosynthesis

Test Yourself

(14)

1.

Name three types of heterotrophic

nutrition.

A: Holozoic nutrition, saprophytism and

parasitism

Test Yourself

(15)

1.

Name the nutritional habits of the

following organisms;

a) Pitcher plants

A:

holozoic nutrition

b) Green algae

A:

photosynthesis

d) Tapeworm

A: parasitism

Test Yourself

(16)

Diet

fats-sweets group protein-rich group dairy products group fruits group vegetables group grain products group

(17)

Diet

Food

Group

Group Foods in the GroupFoods in the Group NutrientsNutrients

Grain

products

products Products made with whole grains or enriched flour.

Mostly carbohydrates and fibres, Vitamin B, iron and protein.

Fruits and

vegetables

Dark green vegetables (broccoli, spinach) and deep yellow vegetables

(carrots).

Most carbohydrates and fibre. Various vitamins and minerals

Protein-rich

food

Poultry, eggs, fish, red meat, organ meat such as kidneys and liver. Legumes,

nuts and seeds.

Rich in proteins, Vitamin B and minerals such as magnesium and zinc.

Dairy

products

products Milk and milk products such as yoghurt and cheese.

Protein, Vitamins A, B and B₂. Main source of calcium.

Fats-sweets

food

Candy, pastries, salad dressing, coffee and

cooking oil.

Supplies fats and sugar. Low in nutrient value.

(18)

 A balanced diet is a diet which supplies all

the essential nutrients in the correct proportions.

 A balanced diet must contain enough:

 Protein to provide all the essential amino acids for

growth and repair for the body

 Energy-food to meet the energy requirements of

the individual

 Minerals and vitamins to maintain good health  Roughage or dietary fibre to stimulate peristalsis  Water to aid the chemical reactions in the body

Diet

(19)



Basal metabolic rate and

physical activity

determine energy needs.



Basal metabolic rate

varies with sex, age and

state of health of a

person.

(20)

1.climate ~living in colder,less humid countries would result in a tendency to actually lose more energy to a person’s surrounding.

~this is due to the body needing more energy to regulate its body temperature.

~those living in hot,wet areas do not use as much energy to maintain their body temperature.

~people living in cold temperature regions would actually have a much higher basal metabolic rate than people living in the tropics.

2.body size ~the difference in body size also contributes to a person’s basal metabolism.

~it is estimated that people with a larger build would have a higher basal metabolic rate than another person with a

smaller build.

3.age ~growing children usually have higher basal metabolism rates than older people simply because of the fact they are

growing.

~for growth to take place,increased energy is also needed. ~adults tend to have a decresing basal metabolic rate throughout their lives.

Factors affecting the daily energy

requirement of the Human body

(21)

4.gender ~men normally have higher heat production than woman of the same size and age,because men usually have less fatty tissue in their body.

~fat healps to conserve heat,and thus,men with less fat would lose heat a a quicker rate than women.

~the result in men having a higher basal metabolic rate than women.

5.health ~the function of the thyroid galand is to control the metabolic rate by secreting a hormone known as thyroxin.

~an underactive thyroid gland would result in insufficient number of the hormone being

created,thereby causing a lower metabolic rate in the person.

~an overactive thyroid,however,may produced too many of these hormones,thereby speeding up the metabolic rate.

6.occupation ~a person who is very active and does heavy labour is only moderately active.

(22)

Energy value in food

samples

 carbohydrates , fats and protein are our main

supplier of energy.

 the same amount of these foods store

different amount of energy.

 the amount of stored energy in food is found

by burning a known mass of the food to heat a certain amount of water in a food calorimeter.

 the amount of heat released from the burning

of a fixed mass of food is equal to the amount of stored energy in the food.

(23)

Malnutrition

• Kwashiorkor

• Marasmus

• Cardiovascular diseases

• Rickets

(24)

KWASHIORKOR

Do you know what Kwashiorkor

is???

_{Kwashiorkor is a form of}

malnutrition

caused by

inadequate protein intake

in the presence of fair to

good energy (total

(25)

KWASHIORKOR

What are the

symptoms?

_{•Failure to gain weight and failure of linear growth}

•Irritability

•Lethargy or apathy •Decreased muscle mass •Swelling (edema)

•Large belly that stick out (protrudes) •Diarrhea

•Dermatitis

•Hair changes -- hair colour may change, often lightening or becoming reddish, thin, or brittle

•increased and more severe infections due to damaged immune system

•Shock (late stage) •Coma (late stage)

(26)

(27)

Marasmus

Marasmus is…

a form of severe protein-energy malnutrition

characterised by energy deficiency

A child with marasmus looks emaciated and the

body weight may reduce to less than 80% of the normal weight for that height.

Marasmus occurrence increases prior to age 1

whereas Kwashiorkor occurrence increases after

(28)

Symptoms??



dry skin, loose skin folds hanging

over the glutei, axillae, etc



Drastic loss of adipose tissue

from normal areas of fat deposits

like buttocks and thighs



pigmented and depigmented hair



flaky paint appearance of skin

(29)

(30)

Cardiovascular Diseases

What Are They??

A

collection of diseases and

conditions affecting :

•The heart

(

cardio

)

•Blood vessels

(

vascular

) –

arteries, veins, and capillaries

(31)

Cardiovascular Diseases



Coronary Artery Disease

– a disease of

the arteries that supply the heart muscles

with blood



Heart attack

– a sudden heart failure



Stroke

– the sudden death of brain cells

when blood supply to the blood cells is cut

off.



High blood pressure

– the excessive

force of blood pumping through the blood

vessels.

(32)

Rickets

Apa itu Rickets (What is

Rickets)?

Rickets is a softening of the bones in children potentially leading to fractures and deformity. Rickets is among the most frequent childhood diseases in many developing countries. The

predominant cause is a vitamin D deficiency, but lack of adequate calcium in the diet may also lead to rickets.

(33)

Symptoms of

Rickets

 Bone pain or tenderness  dental problems

 muscle weakness (

rickety myopathy or "floppy baby syndrome")

 increased tendency for

fractures (easily broken bones),

 Skeletal deformity  Growth disturbance

 Hypocalcaemia (low level of

calcium in the blood), and

 Tetany (uncontrolled muscle

spasms all over the body).

(34)

(35)

(36)

(37)

(38)

(39)

(40)

(41)

(42)

The

Digestiv

e

(43)

(44)

The Digestive

System

Which parts of the

body are involved

in digestion?

• Consists of the

alimentary canal and the glands and organs

associated with it.

• The alimentary canal is like a tube that extends from the mouth to the anus.

• Most of its length is

coiled in the abdominal cavity.

(45)

The Digestive

System

in digestion? in digestion? salivary gland stomach pancreas pyloric sphincter descending colon rectum anus mouth teeth oesophagus liver Gall bladder duodenum ileum ascending colon caecum appendix pharynx

(46)

The Digestive System -

Mouth

 Food enters the body

through the mouth.

 The mouth leads to

(47)

The Digestive System -

Mouth

What do you find in the mouth?:

 Teeth: chewing action

(mastication) breaks down large pieces of food into smaller pieces. This

increases surface area to volume ratio of the food for enzyme action.

 Salivary glands: secrete

saliva into the mouth via ducts.

 Tongue: helps to mix food

with saliva. Taste buds help one to identify and select suitable foods.

salivary gland mout h teeth Process of nutrition??

(48)

The Digestive System -

Pharynx

 Connects the buccal

cavity to the

oesophagus and larynx (voice box).

 Leads to the

trachea.

 Both food and air

must pass through the pharynx then they enter the body.

 Air will pass to the

trachea, while food will go into the

oesophagus. trachea (windpipe) glottis pharynx oesophagus larynx (voice-box) air trachea (windpipe) glottis pharynx oesophagus larynx (voice-box) air

(49)

The Digestive System -

Pharynx

 The epiglottis is

above the larynx, and it prevents food from going the wrong way.

 During swallowing,

the larynx moves up and the epiglottis

moves downwards so that the epiglottis

covers the larynx.

 If food or water enters

the trachea, it induces coughing to force the food/water particles out and prevent

choking. pharynx trachea (windpipe) oesophagus glottis epiglottis food particles larynx (voice-box) pharynx trachea (windpipe) oesophagus glottis epiglottis food particles larynx (voice-box)

(50)

The Digestive System -

Oesophagus

 Also known as the

gullet.

 A narrow, muscular

tube.

 Passes through the

thorax (chest) and the diaphragm to join the stomach.

(51)

The Digestive System -

Oesophagus

 Made up of 2 layers of

muscles, present from the oesophagus to the rectum:

 Longitudinal muscles

(outer layer)

 Circular muscles

(inner layer)

 These muscles are

antagonistic muscles – when one contracts, the other relaxes

circular muscles

Part of the gut wall

longitudin al muscles

(52)

The Digestive System -

Oesophagus

 The muscles cause

peristalsis – rhythmic, wave-like contractions of the gut walls.

 It helps to move food

along the gut while mixing the food with digestive juices.

circular muscles

Part of the gut wall

longitudin al muscles

(53)

The Digestive

System

in digestion? in digestion? mouth teeth oesophagus salivary gland

(54)

food mass

circular muscles longitudinal

muscles

The Digestive System -

Oesophagus

PERISTALSIS

 When circular muscles contract, longitudinal

muscles relax. The gut wall constricts (becomes narrower and longer). Food is squeezed or pushed forward.

 When longitudinal muscles contract, circular

muscles relax. The gut wall dilates (becomes wider and shorter). This widens the lumen for food to enter.

wall constricts to push food forward

wall dilates to allow food to enter

(55)

The Digestive System -

Oesophagus

PERISTALSIS

 When circular muscles contract, longitudinal

muscles relax. The gut wall constricts (becomes narrower and longer). Food is squeezed or pushed forward.

 When longitudinal muscles contract, circular

muscles relax. The gut wall dilates (becomes wider and shorter). This widens the lumen for food to enter.

(56)

The Digestive System -

Stomach

 The stomach is a

distensible (muscular) bag.

 The muscles of the

stomach wall are thick and well-developed.

 When fully stretched,

it sends signals to the brain to indicate that it is full.

(57)

The Digestive System -

Stomach

 The stomach wall has

many pits which lead to gastric glands.

 They secrete gastric

juices into the stomach.

What is

one

enzyme

found in

gastric

juice?

pits

(58)

The Digestive System -

Stomach

 The stomach stores

food for a few hours. It digests food to become chyme.

 Food stays in the

stomach because of the pyloric sphincter – a ring of circular

muscle located

between the stomach and duodenum.

 Contracts: stomach exit

closes

 Relaxes: stomach exit

opens, food leaves the stomach.

Where else

can we find

circular

muscles?

Process of nutrition??

(59)

The Digestive System – Small

Intestine



Consists of 3 parts:

Duodenum Jejunum Ileum

progres

sively

more

coiled

(60)

The Digestive System – Small

Intestine



Wall of small

intestine has 2

functions:

Contains glands which secrete intestinal juice. It contains digestive enzymes. Wall is adapted to absorb digested food products and water.

(61)

The Digestive System – Large

Intestine



The large intestine

is about 1.5 m long

Shorter and wider

than the small intestine 

Consists of 2 parts:

Colon Rectum large intestine small intestine rectum colon

(62)

The Digestive System – Large

Intestine



Only undigested

food enters the

colon.



It absorbs water

and mineral salts

from the food.



No digestion occurs

(63)

The Digestive System – Large

Intestine



The rectum

temporarily stores

faeces.



When it contracts,

faeces is expelled

through the anus.

(64)

The Digestive System – Large

Intestine

 Between the small

and large intestines lie the caecum and

appendix.

 The caecum has no

function in humans.

 The appendix contains

bacteria that are useful to the body.

caecum

appendix

(65)

The Digestive

System

in digestion?

(66)

The Digestive

System

in digestion? in digestion? salivary gland stomach pancreas pyloric sphincter descending colon rectum anus mouth teeth oesophagus liver Gall bladder duodenum ileum ascending colon caecum appendix pharynx

(67)

The Digestive System -

Liver

 The largest internal

organ in the body

 There are 3 important

blood vessels

attached to the liver:

 Hepatic vein  Hepatic artery

(68)

liver

gall bladder _{bile duct}

The Digestive System -

Liver

 It is also the largest

gland in the body.

 Secretes bile into the

duodenum

 Properties of bile:

 Alkaline

 Greenish-yellow

 Contains bile salts and

bile pigments

 Produced in the liver,

stored in the gall bladder

Why

alkaline?

(69)

The Digestive System -

Liver

 Functions of bile:  Neutralize acid in chyme  Activate intestinal enzymes

 Speed up fat digestion  Gives faeces its colour

 When the gall bladder

contracts, bile is secreted into the

duodenum via the bile duct.

liver

gall bladder _{bile duct}

(70)

The Digestive System -

Pancreas

 Connected to the

duodenum via the pancreatic duct

 Secretes pancreatic

juice which contains digestive enzymes.

 Also secretes

hormones which

control blood glucose level.

(71)

Definition of

Digestion

Digestion is the process by which the body breaks down carbohydrates, fats

and proteins into simpler substances that cells can absorb and use.

What is

Digestion?

Physical digestion

The mechanical break up of food into small particles.

Chemical digestion

The breaking down of large molecules in food into small,

soluble molecules which can be absorbed.

Chemical digestion involves hydrolysis catalyzed by digestive enzymes.

(72)

Physical

Digestion

What is What is Digestion? Digestion?

• Physical digestion breaks down food into smaller particles.

• Purpose: to increase surface area to volume ratio of the food to aid enzyme action.

• Food substances are not chemically changed during physical digestion.

• Where does physical digestion occur?

– In the mouth

– Along the alimentary canal

– Physical digestion of fats in the small intestine

chewing / mastication

peristalsis

emulsification

(73)

Physical

Digestion

What is What is Digestion? Digestion? EMULSIFICATION

• Fats do not dissolve in water – they tend to clump

together.

• This reduces the surface area for enzymes to work, slowing down fat digestion. • Bile molecules place

themselves in between the fat and water – half the

molecule is hydrophilic, half is hydrophobic.

• This prevents the fat from clumping together.

• Surface area of fat molecules is increased, speeding up

enzyme action.

Picture taken from

http://www.colorado.edu/eeb/web_resources/carto ons/bile.html

(74)

• Breaking down of large molecules in food (starch, protein, fats) into small soluble molecules which can be absorbed.

• Hydrolytic reactions – catalysed by ENZYMES

• Three groups of enzymes:

• Chemical digestion occurs mainly in 3 parts of the alimentary canal:

– Mouth, stomach, small intestine

Carbohydrases Lipases Proteases

What is

Digestion?

Chemical

Digestion

(75)

Chemical

Digestion

What is What is Digestion? Digestion? In the mouth...

• Food in the mouth stimulates the salivary glands to secrete saliva.

• Saliva is mixed with food. Mucin in saliva softens the food.

• Salivary amylase is found in saliva:

– Digests to

• The optimum pH of salivary amylase is pH 7.

– The pH of saliva is neutral.

• The tongue rolls the food into small, slippery, round masses called boli (singular: bolus).

• The boli are swallowed and passed down into the oesophagus.

(76)

Chemical

Digestion

What is What is Digestion? Digestion? In the stomach...

 _{The presence of food in the stomach}

stimulates the gastric glands to secrete gastric juice into the stomach.

 _{Gastric juice contains 3 substances:}

– Hydrochloric acid – Pepsinogen

(77)

Chemical

Digestion

In the stomach... Action of Pepsin

 _{Pepsinogen is activated to pepsin by} hydrochloric acid.

 _{Pepsin then digests protein to polypeptides.}

pepsinog en pepsi n hydrochloric acid protein s polypeptid es pepsin

(78)

Chemical

Digestion

In the stomach... Action of Rennin

 _{Prorennin is activated to rennin by} hydrochloric acid.

 _{Rennin curdles milk proteins by converting} soluble protein caseinogen into insoluble casein.

– Soluble caseinogen would pass through the stomach as easily as water and not be

digested.

– Insoluble casein can remain in the stomach to be digested. prorenni n renni n hydrochloric acid caseinog en casei n rennin casein polypeptid es pepsin

(79)

Chemical

Digestion

In the stomach... Purpose of Hydrochloric Acid

 _{Stops the activity of salivary amylase by} it

 _{Activates pepsinogen and prorennin to form} and respectively

 _{Provides acidic medium for the action of} pepsin and rennin

 _{Kills harmful microorganisms in food}

denaturing pepsin rennin

(80)

Chemical

Digestion

In the small intestine...

 _{When chyme enters the small intestine, it} stimulates 3 glands:

– Intestinal glands secrete intestinal juice, which contains enzymes sucrase, maltase,

intestinal lipase, lactase, enterokinase,

and erepsin.

– Pancreas secretes pancreatic juice, which contains pancreatic amylase, pancreatic

lipase, and trypsinogen.

– Gall bladder releases bile. It does not contain enzyme

SMILEE!

ALT

(81)

Chemical

Digestion

In the small intestine...



_{All 3 fluids are alkaline:}

– Neutralize acidic chyme

– Provide suitable pH for the action of pancreatic and intestinal enzymes

(82)

Chemical

Digestion

In the small intestine... Carbohydrate digestion starc h maltos e pancreatic amylase lactose glucose + galactose sucros e glucose + fructose gluco se maltase lactase sucrase

(83)

Chemical

Digestion

In the small intestine... Protein digestion

trypsinog en trypsi n enterokinas e proteins polypeptid es trypsin polypeptid es amino acids erepsin

(84)

Chemical

Digestion

In the small intestine... Fat digestion

f ats fatty acids + glycerol lipase

Recall: What

process

speeds up fat

digestion in

the small

intestine?

(85)

Digestive

Enzymes

What is What is Digestion? Digestion? starc h maltose pancreatic amylase lactose glucose + galactose sucros e glucose + fructose glucos e maltase lactase sucrase Carbohydrate digestion star ch maltose salivary amylase mou th sm al l i n te s ti ne

(86)

Digestive

Enzymes

What is What is Digestion? Digestion? Protein digestion sm al l in test

ine trypsinog_en trypsi_n

enterokinas e proteins polypeptid es trypsin polypeptid es amino acids erepsin prorenni n renni n hydrochloric acid caseinog en casei n rennin casein polypeptid es pepsin stom ac h

(87)

Absorption

What happens to What happens to food after food after digestion? digestion?

• Where does absorption occur?

 _{In the small intestine and large intestine}

• What nutrients are being absorbed?

 _{Simple sugars}  _{Amino acids}

 _{Fatty acids and glycerols}  _{Water and mineral salts}

(88)

Absorption

How does absorption take place in the small intestine?

• Glucose and amino acids:

– Absorbed by into blood capillaries of the villi.

– Absorbed by when there is lower concentration of digested food

substances in the small intestine than in the blood capillaries.

• Fatty acids and glycerol:

– Absorbed by into the epithelium – Combine to form fat globules which enter the

lacteals

• Water and mineral salts:

– Absorbed by the and

– Most of the water is absorbed by the ileum diffusio nactive transport diffusio n small intestine colon

(89)

Absorption: Small

Intestine

Adaptations of the Small Intestine for Absorption

• The rate of absorption of digested food substances depends on 3 factors:

1. Surface area

2. The thickness of cell membranes 4. Concentration

(90)

Absorption: Small

Intestine

What happens to What happens to food after food after digestion? digestion? 1. Surface Area

• The surface area of the small intestine is increased for absorption in 4 ways:

1. Inner walls have folds

2. The surface of the folds are lined with

numerous villi (singular: villus), which are minute finger-like projections.

3. The epithelial cells of the villi have numerous microvilli.

4. The small intestine is long, providing large surface area and ample time for absorption.

(91)

Absorption: Small

Intestine

(92)

Absorption: Small

Intestine

(93)

Absorption: Small

Intestine

2. Thickness of Cell Membranes

• The villi have very thin membranes: the epithelium is only one-cell thick.

3. Concentration Gradient

• In each villus is a lacteal (lymphatic

capillary) surrounded by blood capillaries. • The lacteal continually transports away

from the villus, while the blood capillaries transports and away.

• This maintains the concentration gradient needed for the absorption of food

substances.

fats

sugars amino

(94)

Egestion

• Some food substances cannot be digested and remain unabsorbed in the large

intestine.

• These are stored temporarily in the rectum. • When the rectum is full, they are discharged

as faeces through the .

• This process is known as egestion or defecation.

(95)

Transport and

Assimilation

Transport of Simple Sugars

• After absorption, the blood in the villi is rich in sugars.

• Blood capillaries unite to form the hepatic portal vein.

• The hepatic portal vein transports sugars to the liver.

(96)

Transport and

Assimilation

Assimilation of Simple Sugars

• In the liver, most sugars are converted to glycogen and stored.

• Glucose leaves the liver and is distributed around the body by the bloodstream.

– Used during respiration to provide energy for cells.

• Excess glucose is returned to the liver

– Hormone insulin (produced by Islets of

Langerhan in the pancreas) stimulates the liver to convert glucose to glycogen for

storage.

– When more glucose is required, the liver will convert glycogen back to glucose.

(97)

Transport and

Assimilation

Transport and Assimilation of Amino Acids

• Amino acids pass through the liver before they are transported to the rest of the body. • How are amino acids used?

– Converted to protoplasm by cells, used for growth and repair of body parts

– Used to form enzymes and hormones

(98)

Functions of the

Liver

The Liver has 7 Functions

2.Regulation of blood glucose concentration 3.Production of bile

4.Protein synthesis 5.Iron storage

6.Deamination of amino acids 7.Detoxification

(99)

Functions of the

Liver

1. Regulation of Blood Glucose Concentration

• Blood normally contains about 70-90 mg of glucose per 100 cm3 of blood.

• After a meal:

– Amount of glucose in the blood rises – Stimulates Islets of Langerhans in the

pancreas to secrete insulin into the bloodstream

– Insulin is transported to the liver.

– Insulin stimulates liver to convert excess glucose to glycogen for storage.

– Blood leaving the liver contains a constant amount of glucose.

What about

adrenaline??

(100)

Functions of the

Liver

• When body cells need glucose:

– Glucose level in the blood drops.

– Islets of Langerhan are stimulated to secrete hormone glucagon.

– Glucagon stimulates liver to convert stored glycogen to glucose.

– Glucose enters the blood; blood glucose level returns to normal.

(101)

Functions of the

Liver

• If we have not eaten for a long time:

– Glucose level in the blood drops below average.

– Blood that is low in glucose reaches the hypothalamus in the brain.

– Brain sends signals to the stomach.

– This causes strong contractions and we feel hunger pangs.

– After eating, the blood glucose level rises. The hypothalamus signals to the stomach to stop contracting.

(102)

Functions of the

Liver

high blood glucose concentratio

n

normal blood glucose concentration low blood glucose concentrati on pancreas secretes insulin pancreas secretes glucagon converts glucose to glycogen converts glycogen to glucose

(103)

Functions of the

Liver

What happens to What happens to food after food after digestion? digestion? 2. Production of Bile

• The liver produces bile which is stored in the before use.

• Bile is used in the of fats.

3. Protein Synthesis

• Blood plasma contains amino acids from the diet.

• The liver synthesizes these amino acids to form proteins, e.g.:

– Albumins, globulins, fibrinogen (for blood clotting)

gall bladd

er _emulsifica tion

(104)

Functions of the

Liver

What happens to What happens to food after food after digestion? digestion? 4. Iron Storage

• Red blood cells contain a iron, which is involved in the transportation of oxygen around the body.

• These cells become worn out after some time.

• They are destroyed in the spleen, a gland near the liver.

• Haemoglobin from red blood cells is brought to the liver.

• Haemoglobin is broken down, forming iron and bile.

(105)

Functions of the

Liver

5. Deamination of Amino Acids

• Excess amino acids are transported to the liver.

• The amino groups are removed and converted to urea.

• Urea leaves the body in urine.

• The remains of the amino acid are converted into glucose.

• Excess glucose is converted to .

(106)

Functions of the

Liver

What happens to What happens to food after food after digestion? digestion? 6. Detoxification

• This is the process of converting harmful substances into harmless ones.

• Breaks down alcohol to acetaldehyde by the action of alcohol dehydrogenase

• Acetaldehyde can be broken down to compounds which can be used in

respiration.

• Excessive alcohol consumption stimulates acid secretion in the stomach, increasing the risk of gastric ulcers.

(107)

Functions of the

Liver

What happens to What happens to food after food after digestion? digestion? 6. Detoxification

• Prolonged alcohol use can lead to cirrhosis of the liver.

– Liver cells are being destroyed and replaced with fibrous tissue

– Cells are less able to function

(108)

Functions of the

Liver

What happens to What happens to food after food after digestion? digestion? 7. Heat Production

• There are many chemical reactions taking place in the liver.

• Heat is produced from these reactions.

• The heat is distributed by the blood to other parts other body.

(109)



Bowel movements are difficult and do

not occur often enough.



It is caused by a lack of exercise,

emotional distress or misuse of

laxatives, and/or a diet low in dietary

fibres.



Due to constipation, abdominal

pressure causes blood vessels in the

rectum to enlarge, producing

haemorrhoids.

Evaluating Eating Habits

(110)

 Anorexia nervosa is characterised by constant

dieting, rapid weight loss and feeling too fat in spite of the weight loss.

 Bulimia is characterised by eating too much food

through vomiting or the use of laxatives; tend to gain weight easily and live in constant fear of

becoming obese. Bulimics often have mouth and throat problems due to repeating vomiting.

Both

anorexics

and

bulimics

have a constant fear of

being fat and fear rejection

Evaluating Eating Habits

(111)

Photosynthesis

(112)

Photosynthesis



The synthesis of organic

compounds



From the splitting of water

(photolysis) in the light

dependent reaction



And from the reduction of

carbon dioxide in the light

independent reaction

(113)

Photosynthesis

LIGHT

H

₂₂

O

Oxygen

2H+

ATP

CO

₂₂

Carbohydrate

(114)

Leaf structure



The leaf is the main site for

photosynthesis in plants



It has several special features

which help it carry out this role;



Flattened shape – increasing surface

area



Thin – so that gases can diffuse

quickly



A vascular system – to supply water

& take away the products



Stomata – To allow gas exchange



Chloroplast containing cells – to

(115)

Leaf structure

Cuticle Upper epidermis Palisade Vascular tissue Spongy mesophyll Lower epidermis

(116)

Palisade cell structure

Chloroplast Cell surface membrane Vacuole Tonoplast Starch grain Cytoplasm Nucleus

Cellulose cell wall Cytoplasm

(117)

Chloroplast structure

(118)

Chloroplast structure

Oil droplet Ribosomes Thylakoid membranes DNA

Starch grain Intergranal membrane Stroma

(119)

(120)

Factors Affecting Photosynthesis

Light Intensity

Concentration Of Carbon Dioxide

Temperature

(121)

LIGHT INTENSITY

Light is essential during the light

reaction of photosynthesis.

When the concentration of carbon

dioxide and temperature are controlled

at constant level, the rate of

photosynthesis is directly

proportional to light intensity up to

a certain point.

(122)

Light intensity

Light intensity R ate of phot osy nt hesis

(123)

Concentration of carbon

dioxide

 Carbon dioxide is needed in the dark reaction as a

raw material used in the synthesis of glucose if there is no other factors limiting photosynthesis and increase in the concentration of carbon

dioxide results in an increase in the rate of photosynthesis.



At a very high light intensity, the rate of

photosynthesis slows down because the

pigment chlorophyll is damaged by

ultra-violet rays.

(124)

Carbon dioxide

concentration

Light intensity  Rate of photos ynt hes is 0.035% CO₂ 1% CO₂

(125)

WATER SUPPLY

Water is needed for

photosynthesis, however water is rarely the limiting factor in photosynthesis because the amount of water required is small.

If water is not supplied,

wilting occurs and the stomata is closed.This prevents the

diffusion of carbon dioxide

into the leaves.As a result the rate of photosynthesis

decreases as the lower

concentration of carbon dioxide becomes the limiting factor.

(126)

Temperature

The dark reaction of photosynthesis is

catalysed by the photosynthetic enzyme and

therefore changes in temperature will

affect the rate of photosynthesis.

Generally, an increase of 10 degree Celsius

in the surrounding temperature will doubled

the rate of photosynthesis.

The optimum temperature for most of the

plants are between 25-30 degree celcius.

However, when the temperature is too high

the photosynthetic enzyme are destroyed and

photosynthesis stops altogether.

(127)

Temperature

Rate of photos ynt hes is Temperature 25ºC Increasing KE Enzymes denatured

(128)

Carring attitude towards

plants

…

THE NEED TO TAKE CARE OF PLANTS.

 Sustains life

d) Green plans produce and generates the supply of oxygen that all

living things need.

 Air quality

f) Plants influence the quality of the air that we breathe. g) Plants stop the movement of dust and pollutants.

h) Plants reduce the greenhouse effect caused by burning of fossil

fuels by absorbing and removing large amounts of carbon dioxide from the atmoshere.

 Climate

j) The type of plant cover influences regional climates.

k) The destruction of forest causes drought and turns fertile land

(129)



Water quality

b) Forests are important in maintaining healthy watercatchment

areas.

c) Forest hold sil in place,and filtering sediments from water

flowing into streams,rivers and lakes.



Control of erosion

e) Plants and trees help to protect the soil from erosion caused

by heavy rains.

f) Uncontrolled felling of trees and clearing of plants and

clearing of plants can cause landslides.



Fish and wildlife habitat

h) Plants provide the necessary habitats for wildlife and fish

(130)



Ecosystem

b) Humans,plants and animals all live together supporting each

other.

c) Each species serves an important role in the ecosystem.



Food

e) Humans use about 3000 species of plants as food.



Medicine

g) Plants have been providing humans with medicines thoughout

human history.

h) About 80% of all medicinal drugsoriginate from wild plants and

there are many important drugs yet to be discovered from plants.

(131)



Industrial products

b) We use fibres from plants to provide clothing.

c) We build our houses and furniture using wood from plants. d) We produce fuel products are made from plants,palm oil