41_Lecture_Student_Presentation.ppt

(1)

PowerPoint®_{Lecture Presentations for}

Biology

Eighth Edition

Neil Campbell and Jane Reece

Lectures by Chris Romero, updated by Erin Barley with contributions from Joan Sharp

Chapter 41

(2)

Overview: The Need to Feed

• Food is taken in, taken apart, and taken up in the process of animal nutrition

• _{In general, animals fall into three categories:}

– Herbivores eat mainly autotrophs (plants and algae)

– _{Carnivores eat other animals}

(3)

Concept 41.1: An animal’s diet must supply chemical energy, organic molecules, and essential nutrients

• An animal’s diet provides chemical energy, which is converted into ATP and powers

processes in the body

• _{Animals need a source of organic carbon and}

organic nitrogen in order to construct organic molecules

(4)

Essential Nutrients

• There are four classes of essential nutrients:

– Essential amino acids

– Essential fatty acids

– Vitamins

(5)

Essential Amino Acids

• Animals require 20 amino acids and can

synthesize about half from molecules in their diet

• _{The remaining amino acids, the}_essential

amino acids, must be obtained from food in preassembled form

• A diet that provides insufficient essential amino acids causes malnutrition called protein

(6)

• Meat, eggs, and cheese provide all the

essential amino acids and are thus “complete” proteins

• _{Most plant proteins are incomplete in amino}

acid makeup

• Individuals who eat only plant proteins need to eat specific plant combinations to get all

(7)

Fig. 41-2

Beans and other legumes

Corn (maize)

and other grains

Lysine

Essential amino acids for adults

Tryptophan Isoleucine

Leucine

Phenylalanine Threonine

Valine

(8)

• Some animals have adaptations that help them through periods when their bodies demand

(9)

Essential Fatty Acids

• Animals can synthesize most of the fatty acids they need

• _The_{essential fatty acids}_{are certain}

unsaturated fatty acids that must be obtained from the diet

(10)

Vitamins

• Vitamins are organic molecules required in the diet in small amounts

• _{13 vitamins essential to humans have been}

identified

(11)

(12)

Minerals

(13)

(14)

Dietary Deficiencies

• Undernourishment is the result of a diet that consistently supplies less chemical energy

than the body requires

• _{Malnourishment}_{is the long-term absence}

(15)

Undernourishment

• An undernourished individual will

– Use up stored fat and carbohydrates

– Break down its own proteins

– _{Lose muscle mass}

– Suffer protein deficiency of the brain

(16)

Malnourishment

• Malnourishment can cause deformities, disease, and death

• _{Malnourishment can be corrected by changes}

(17)

Assessing Nutritional Needs

• Insights into human nutrition have come from

epidemiology, the study of human health and

disease in populations

• _{Neural tube defects were found to be the result}

(18)

(19)

Concept 41.2: The main stages of food processing are ingestion, digestion, absorption, and

elimination

(20)

Suspension Feeders

• _{Many aquatic animals are}_suspension

(21)

Substrate Feeders

• _{Substrate feeders}_{are animals that live in or}

(22)

Fig. 41-6b

Leaf miner caterpillar, a substrate feeder

(23)

Fluid Feeders

• _{Fluid feeders}_{suck nutrient-rich fluid from a}

(24)

Bulk Feeders

(25)

• Digestion is the process of breaking food down into molecules small enough to absorb

– In chemical digestion, the process of enzymatic hydrolysis splits bonds in molecules with the addition of water

• _Absorption_{is uptake of nutrients by body cells}

(26)

Fig. 41-7

Ingestion Digestion Absorption Elimination

Undigested material

Chemical digestion

(enzymatic hydrolysis) Nutrient_molecules

enter body cells Small molecules Mechanical digestion Food Pieces of food

(27)

Digestive Compartments

• Most animals process food in specialized compartments

• _{These compartments reduce the risk of an}

(28)

Intracellular Digestion

(29)

Extracellular Digestion

• Extracellular digestion is the breakdown of food particles outside of cells

• _{It occurs in compartments that are continuous}

(30)

Fig. 41-8

Gastrovascular cavity

Food

Epidermis

Mouth Tentacles

(31)

• Animals with simple body plans have a

gastrovascular cavity that functions in both digestion and distribution of nutrients

Video: Hydra Eating Daphnia

(32)

• More complex animals have a digestive tube with two openings, a mouth and an anus

• _{This digestive tube is called a}_complete

digestive tract or an alimentary canal

(33)

Fig. 41-9 Esophagus Mouth Pharynx Crop Gizzard Typhlosole Intestine

Lumen of intestine

(34)

Concept 41.3: Organs specialized for sequential stages of food processing form the mammalian digestive system

• _{The mammalian digestive system consists of}

an alimentary canal and accessory glands that secrete digestive juices through ducts

• Mammalian accessory glands are the salivary glands, the pancreas, the liver, and the

(35)

• Food is pushed along by peristalsis, rhythmic contractions of muscles in the wall of the canal

• Valves called sphincters regulate the

(36)

Fig. 41-10 Cecum Anus Anus Ascending portion of large intestine Gall-bladder Small intestine Large intestine Small intestine Rectum Pancreas Liver Salivary glands Tongue Oral cavity Pharynx Esophagus Sphincter Stomach Sphincter Duodenum of small intestine Appendix Liver Pancreas Small intestine Large intestine Rectum Stomach Gall-bladder

A schematic diagram of the human digestive system

Esophagus

(37)

The Oral Cavity, Pharynx, and Esophagus

• The first stage of digestion is mechanical and takes place in the oral cavity

• _{Salivary glands}_{deliver saliva to lubricate food}

• Teeth chew food into smaller particles that are exposed to salivary amylase, initiating

(38)

• The tongue shapes food into a bolus and provides help with swallowing

• _{The region we call our throat is the}_pharynx_{, a}

junction that opens to both the esophagus and the trachea (windpipe)

(39)

• The esophagus conducts food from the pharynx down to the stomach by peristalsis

• _{Swallowing causes the epiglottis to block entry}

to the trachea, and the bolus is guided by the larynx, the upper part of the respiratory tract

(40)

(41)

Digestion in the Stomach

(42)

Chemical Digestion in the Stomach

• _{Gastric juice is made up of hydrochloric acid}

and the enzyme pepsin

• Parietal cells secrete hydrogen and chloride

ions separately

• _{Chief cells}_{secrete inactive}_pepsinogen_, _which

is activated to pepsin when mixed with hydrochloric acid in the stomach

• _Mucus_{protects the stomach lining from gastric}

(43)

Fig. 41-12 Interior surface of stomach Esophagus Chief cells Small intestine Epithelium Stomach Sphincter Parietal cell

Pepsinogen and HCl are secreted.

HCl converts

pepsinogen to pepsin.

(44)

(45)

Stomach Dynamics

• Coordinated contraction and relaxation of

stomach muscle churn the stomach’s contents

• _{Sphincters prevent chyme from entering the}

(46)

Digestion in the Small Intestine

• The small intestine is the longest section of the alimentary canal

• _{It is the major organ of digestion and}

(47)

Fig. 41-13 Oral cavity, pharynx, esophagus Stomach Lumen of small intes-tine Epithelium of small intestine (brush border) Carbohydrate digestion Polysaccharides Smaller polysaccharides, maltose Polysaccharides

Maltose and other disaccharides

Disaccharides

Protein digestion Nucleic acid digestion Fat digestion

Proteins Small polypeptides Pepsin Pancreatic amylases Salivary amylase Disaccharidases Monosaccharides Small peptides Amino acids Amino acids Polypeptides Smaller polypeptides

Pancreatic trypsin and chymotrypsin Pancreatic carboxypeptidase Dipeptidases, carboxypeptidase, and aminopeptidase DNA, RNA Pancreatic nucleases Fat globules

Nucleotides Fat droplets

Nucleosides Nitrogenous bases, sugars, phosphates Nucleotidases Nucleosidases and phosphatases Glycerol, fatty acids, monoglycerides Bile salts Pancreatic lipase

(48)

• The first portion of the small intestine is the

duodenum, where acid chyme from the

stomach mixes with digestive juices from the pancreas, liver, gallbladder, and the small

(49)

(50)

Pancreatic Secretions

• The pancreas produces proteases trypsin and chymotrypsin, protein-digesting enzymes that are activated after entering the duodenum

• _{Its solution is alkaline and neutralizes the}

(51)

Bile Production by the Liver

• In the small intestine, bile aids in digestion and absorption of fats

• _{Bile is made in the}_liver_{and stored in the}

(52)

Secretions of the Small Intestine

• The epithelial lining of the duodenum, called the brush border, produces several digestive enzymes

• _{Enzymatic digestion is completed as peristalsis}

moves the chyme and digestive juices along the small intestine

• Most digestion occurs in the duodenum; the jejunum and ileum function mainly in

(53)

Absorption in the Small Intestine

• The small intestine has a huge surface area, due to villi and microvilli that are exposed to the intestinal lumen

• _{The enormous microvillar surface greatly}

(54)

Fig. 41-15

Muscle layers

Microvilli (brush border) at apical (lumenal) surface Vein carrying blood

to hepatic portal vein

(55)

• Each villus contains a network of blood vessels and a small lymphatic vessel called a lacteal

• _{After glycerol and fatty acids are absorbed by}

epithelial cells, they are recombined into fats within these cells

• These fats are mixed with cholesterol and

coated with protein, forming molecules called

(56)

Fig. 41-16

Lumen of small intestine

Lacteal

Chylomicron

Phospholipids, cholesterol, and proteins

Triglycerides

Monoglycerides Triglycerides

Fatty acids Epithelial

(57)

• Amino acids and sugars pass through the

epithelium of the small intestine and enter the bloodstream

• _{Capillaries and veins from the lacteals}

(58)

Absorption in the Large Intestine

• The colon of the large intestine is connected to the small intestine

• _The_cecum_{aids in the fermentation of plant}

material and connects where the small and large intestines meet

• The human cecum has an extension called the

(59)

• _{A major function of the colon is to recover}

water that has entered the alimentary canal

• Wastes of the digestive tract, the feces,

become more solid as they move through the colon

• _{Feces pass through the rectum and exit via the}

(60)

• The colon houses strains of the bacterium

Escherichia coli, some of which produce

vitamins

• _{Feces are stored in the}_rectum_{until they can}

be eliminated

(61)

Concept 41.4: Evolutionary adaptations of

vertebrate digestive systems correlate with diet

• Digestive systems of vertebrates are variations on a common plan

• _{However, there are intriguing adaptations,}

(62)

Some Dental Adaptations

• Dentition, an animal’s assortment of teeth, is one example of structural variation reflecting diet

• _{Mammals have varying dentition that is}

adapted to their usual diet

• The teeth of poisonous snakes are modified as fangs for injecting venom

• _{All snakes can unhinge their jaws to swallow}

(63)

Fig. 41-18

Incisors

(c) Omnivore

Molars

(b) Herbivore (a) Carnivore

(64)

Stomach and Intestinal Adaptations

(65)

Fig. 41-19

Cecum

Small intestine

Herbivore Carnivore

Colon (large intestine) Stomach Small

(66)

Mutualistic Adaptations

• Many herbivores have fermentation chambers, where symbiotic microorganisms digest

cellulose

• _{The most elaborate adaptations for an}

(67)

Fig. 41-20

Esophagus

Omasum Abomasum

Intestine

Rumen Reticulum

1 2

(68)

Concept 41.5: Homeostatic mechanisms contribute to an animal’s energy balance

(69)

Energy Sources and Stores

• Nearly all of an animal’s ATP generation is based on oxidation of energy-rich molecules: carbohydrates, proteins, and fats

• Animals store excess calories primarily as glycogen in the liver and muscles

• Energy is secondarily stored as adipose, or fat, cells

(70)

Fig. 41-21

Homeostasis: 90 mg glucose/ 100 mL blood

Stimulus: Blood glucose

level rises after eating.

Stimulus: Blood glucose

(71)

Overnourishment and Obesity

• Overnourishment causes obesity, which

results from excessive intake of food energy with the excess stored as fat

• _{Obesity contributes to diabetes (type 2), cancer}

(72)

• Researchers have discovered several of the mechanisms that help regulate body weight

• _{Homeostatic mechanisms are feedback circuits}

that control the body’s storage and metabolism of fat over the long-term

(73)

• The complexity of weight control in humans is evident from studies of the hormone leptin

• _{Mice that inherit a defect in the gene for leptin}

(74)

Fig. 41-24

Obese mouse with mutant

ob gene (left) next to wild-type mouse.

EXPERIMENT

(75)

Obesity and Evolution

• The problem of maintaining weight partly stems from our evolutionary past, when fat hoarding was a means of survival

• _{A species of birds called petrels become obese}

as chicks; in order to consume enough protein from high-fat food, chicks need to consume

(76)

Fig. 41-UN1

Bloodstream

Veins to heart

Lymphatic system Small intestine Esophagus Stomach Lipids Mouth

Hepatic portal vein

Absorbed food

(except lipids) Absorbedwater

Secretions from the gastric glands of the stomach

Secretions from the pancreas and the liver

Liver

Rectum Anus

(77)

You should now be able to:

1. Name the three nutritional needs that must be met by an animal’s diet

2. Describe the four classes of essential nutrients

3. Distinguish among undernourishment, overnourishment, and malnourishment

4. Describe the four main stages of food processing

(78)

6. Follow a meal through the mammalian digestive system:

– List important enzymes and describe their roles

– Compare where and how the major types of macromolecules are digested and absorbed

7. Relate variations in dentition with different diets