1

2

Lecture 13 Outline (Ch. 41)

I. Animal Nutrition Overview

II. Essential Parts of Animal Diet

III. Food Intake

IV. Digestive Compartments

V. Adaptations

VI. Obesity

VII. Lecture Concepts

3

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, algae)– Carnivores eat other animals– Omnivores regularly consume animals as well as

plants or algal matter

4How does a diet of lean fish help make a bear fat?

5

• Chemical energy, which is converted into ATP and powers processes in the body

• Organic carbon and organic nitrogen • Essential nutrients must be obtained

from dietary sources

Essential Parts of Diet

–Essential amino acids–Essential fatty acids–Vitamins–Minerals

6

• Meat, eggs, cheese - provide all nine essential amino acids ( “complete” proteins)

• Individuals eating only plant proteins need specific plant combinations for all essential amino acids

Essential Parts of Diet

Beans and otherlegumes

Corn (maize)and other grains

Lysine

Essential amino acids for adults

Tryptophan

Isoleucine

Leucine

Phenylalanine

Threonine

Valine

Methionine

7

Essential Fatty Acids• Animals can synthesize most fatty acids they need• The essential fatty acids are certain unsaturated

fatty acids that must be obtained from the diet• Deficiencies in fatty acids are rare

8

Vitamins• Vitamins: organic molecules, small amounts needed• 13 vitamins essential to humans have been identified• Two categories: fat-soluble & water-soluble

B-complex

Biotin

Vitamin C (ascorbic acid)

Vitamin A

Vitamin D

Vitamin E

Vitamin K

Table 41-1

9

Minerals

• Minerals: simple inorganic nutrients, usually required in small amounts

Calcium

Phosphorus

Potassium

Sulfur

Chlorine

Sodium

Magnesium

Iron

Table 41-2

10

Dietary Deficiencies• Undernourishment – diet consistently low in chemical energy• Malnourishment – long-term absence of essential nutrients

An undernourished individuals use up stores, break down own protein and muscle

Malnourishment can cause deformities, disease, and death

11

Ingestion: the act of eating

• Suspension feeders - many aquatic animals, which sift small food particles from the water

• Substrate feeders are animals that live in or on their food source

• Fluid feeders suck nutrient-rich fluid from a living host

• Bulk feeders eat relatively large pieces of food

Food Intake

12

Humpback whale, a suspension feeder

Baleen

Leaf miner caterpillar, substrate feeder

Caterpillar Feces

Mosquito, a fluid feeder Rock python, a bulk feeder

13

• 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

• Elimination is the passage of undigested material out of the digestive compartment

14

Ingestion Digestion Absorption Elimination

Undigestedmaterial

Chemical digestion(enzymatic hydrolysis)

Nutrientmoleculesenter bodycells

Smallmolecules

Mechanicaldigestion

Food

Piecesof food

1 2 3 4

Food Intake

15

Digestive Compartments• Most animals process food in specialized

compartments• Reduces risk animal digesting

its own cells/ tissues

Gastrovascularcavity

Food

Epidermis

Mouth

Tentacles

Gastrodermis

16

• More complex animals: digestive tube with two openings (mouth, anus)

• Tube called a complete digestive tract or an alimentary canal

• Can have specialized regions, carry out digestion and absorption stepwise

Digestive Compartments

Esophagus

Mouth

Pharynx

Crop Gizzard

Typhlosole

Intestine

Lumen of intestine

Anus

(b) Grasshopper

Foregut

(c) Bird

(a) Earthworm

Midgut Hindgut

Esophagus RectumAnus

Mouth

Crop

Gastric cecae

Esophagus

Mouth

CropAnus

StomachGizzard

Intestine

17

Cecum

Anus Anus

Ascendingportion oflarge intestine

Gall-bladder

Smallintestine

Largeintestine

Smallintestine

Rectum

Pancreas

Liver

Salivary glands

TongueOral cavity

PharynxEsophagus

Sphincter

Stomach

Sphincter

Duodenum ofsmall intestine

Appendix

Liver

Pancreas

Smallintestine

Largeintestine

Rectum

StomachGall-bladder

A schematic diagram of thehuman digestive system

Esophagus

Salivaryglands

Mouth

Digestive Compartments

• Mammalian alimentary canal and accessory glands that secrete digestive juices through ducts

18

Larynx

Trachea

Epiglottisup

Pharynx

Tongue

Glottis

Esophagus

Esophagealsphinctercontracted

Food

Tostomach

Tolungs

Epiglottisdown

Esophagealsphincterrelaxed

Glottis upand closed

Epiglottisup

Esophagealsphinctercontracted

Sphincterrelaxed

Relaxedmuscles

Contractedmuscles

Relaxedmuscles

Stomach

Glottisdownand open

Oral Cavity, Pharynx, Esophagus

• Food shaped into a bolus, lubricated by saliva, digestion begins with amylase.

• Pharynx, a junction that opens to both the esophagus and the trachea (windpipe)

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

• Epiglottis blocks entry to the trachea, and larynx.

19

Digestion in the Stomach• The stomach stores food and secretes gastric

juice, which converts a meal to acid chyme

• Gastric juice - hydrochloric acid and the enzyme pepsin

• Mucus protects the stomach lining from gastric juice Interior surface

of stomach

Esophagus

Chief cells

Small intestine

Epithelium

Stomach

Sphincter

Parietal cell

Chief cell

Folds ofepithelialtissue

Pepsin

Sphincter

Pepsinogen

HCl

H+

Cl–

Parietal cells

Mucus cells

Gastric gland

1

2

3

5 µ

m

20

Digestion in the Small Intestine • The small intestine: longest section of alimentary canal• Major organ of digestion and absorption

• First is the duodenum - acid chyme from the stomach mixes with digestive juices from the pancreas, liver, gallbladder, and the small intestine itself.

pancreas

proteases trypsin & chymotrypsin, protein-digesting enzymes

neutralizes the acidic chyme

liver/gallbladder

bile aids digestion and absorption of fats

small intestine

lining of duodenum (brush border) produces several digestive enzymes

jejunum and ileum mainly absorb water & nutrients

21

Oral cavity,pharynx,esophagus

Stomach

Lumen ofsmall intestine

Epitheliumof smallintestine(brushborder)

Carbohydrate digestion

Polysaccharides

Smaller polysaccharides,maltose

Polysaccharides

Maltose and otherdisaccharides

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

Smallerpolypeptides

Pancreatic trypsin andchymotrypsin

Pancreatic carboxypeptidase

Dipeptidases, carboxypeptidase,and aminopeptidase

DNA, RNA

Pancreatic nucleases

Fat globules

NucleotidesFat droplets

Nucleosides

Nitrogenous bases,sugars, phosphates

Nucleotidases

Nucleosidasesandphosphatases

Glycerol, fattyacids, monoglycerides

Bile salts

Pancreatic lipase

(starch, glycogen) (sucrose, lactose)

22

Absorption in the Small Intestine• small intestine has huge surface area, from villi and

microvilli exposed to the intestinal lumen• enormous microvillar surface greatly increases rate

of nutrient absorption

Muscle layers

Microvilli (brushborder) at apical(lumenal) surface

Vein carrying bloodto hepatic portal vein

Villi

Intestinal wall

Key

Nutrientabsorption

Largecircularfolds

Bloodcapillaries

Epithelialcells

Villi

Lymphvessel

Basal surface

Lacteal

Epithelial cells

Lumen

23

Absorption in the Large Intestine• The colon of the large intestine is

connected to the small intestine• The cecum aids in

fermentation of plant material, connects where the small and large intestines meet

• Human cecum has extension (appendix), plays a minor role in immunity

Feces stored in rectum until eliminated

24

• The colon houses strains of the bacterium Escherichia coli, some of which produce vitamins

• Two sphincters between the rectum and anus control bowel movements

25

• Herbivores generally have longer alimentary canals than carnivores, reflecting the longer time needed to digest vegetation

Cecum

Small intestine

HerbivoreCarnivore

Colon(largeintestine)

StomachSmall intestine

Adaptations

26

Mutualistic Adaptations• Many herbivores have symbiotic microorganisms

that digest cellulose• The most elaborate adaptations in ruminants

Esophagus

OmasumAbomasum

Intestine

Rumen Reticulum1 2

4 3

27

Energy Sources and Stores• Animals store excess calories as glycogen in the

liver and muscles• Energy secondarily stored as adipose, or fat, cells• When fewer calories are taken in than are

expended, fuel is taken from storage and oxidized

100 µm

Fat cells

• Obesity is due to excessive intake of food energy, excess stored as fat

• Obesity contributes to diabetes (type 2), cancer of the colon and breasts, heart attacks, and strokes

28

Homeostasis:90 mg glucose/100 mL blood

Stimulus:Blood glucose

level risesafter eating.

Stimulus:Blood glucose

level dropsbelow set point.

29

LeptinPYY

Insulin

Ghrelin

Energy Sources and Stores

• 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 become very obese

30

Obese mouse with mutant ob gene (left) next to wild-type sibling mouse.

31

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 more calories than they burn

32Figure 41.25 A plump petrel

33

Lecture 13 concepts- Name the three nutritional needs that must be met by diet

- Describe the four classes of essential nutrients

- Distinguish among undernourishment, overnourishment, and malnourishment

- Describe the four main stages of food processing

- Distinguish between complete digestive tracts and gastrovascular cavities

- 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

- Explain where and in what form energy-rich molecules may be stored in the human body

- Make a list of new vocabulary with definitions.