Chapter 41: Animal Nutrition

1. Why do we eat?- Fuel (chemical energy)- To get organic material for biosynthesis (carbon skeletons)- Essential nutrients (substances that can’t be made from scratch)

2. What are the 4 main feeding mechanisms of animals?- Suspension feeders- Substrate feeder- Fluid feeders - Bulk feeders

Figure 41.2 Four Main Feeding Mechanisms of Animals

Baleen

SUSPENSION FEEDERS

Feces

SUBSTRATE FEEDERS

BULK FEEDERS

FLUID FEEDERS

Caterpillar

Chapter 41: Animal Nutrition

1. Why do we eat?2. What are the 4 main feeding mechanisms of feeding?3. When our bodies need energy, what is the order of fuel usage?

(fat- protein- carbs- )4. How is appetite regulated in the body?

- Hormonessource fcn

- PYY S. intestine suppresses appetite(after meals)

- Insulin pancreas suppresses appetite ↑blood sugar=↑insulin- Ghrelin stomach triggers hunger ↓weight = ↑ghrelin

(+) makes dieting difficult

- Leptin adipose suppresses appetite- ↑ Fat = ↑ leptin = ↓ appetite- ↓ Fat = ↓ leptin = ↑ appetite

1st 2nd 3rd

Figure 41.5 A few of the appetite-regulating hormones

Produced by adipose (fat) tissue, leptin suppresses

appetite as its level increases. When body fat decreases,

leptin levels fall, and appetite increases.

LeptinPYY

Insulin

Ghrelin

Secreted by the stomach wall, ghrelin is one of the signals that triggers feelings of hunger as mealtimes approach. In dieters who lose weight, ghrelin levels increase, which may be one reason it’s so hard to stay on a diet.

The hormone PYY, secreted by the small intestine after meals,

acts as an appetite suppressant that

counters the appetite stimulant ghrelin.

A rise in blood sugar level after a meal stimulates the pancreas to secrete insulin (see Figure 41.3). In addition to its other functions, insulin suppresses appetite by acting on the brain.

Chapter 41: Animal Nutrition

1. Why do we eat?2. What are the 4 main feeding mechanisms of feeding?3. When our bodies need energy, what is the order of fuel usage?

(fat- protein- carbs- )4. How is appetite regulated in the body?

- Hormonessource fcn

- PYY S. intestine suppresses appetite(after meals)

- Insulin pancreas suppresses appetite ↑blood sugar=↑insulin- Ghrelin stomach triggers hunger ↓weight = ↑ghrelin

makes dieting difficult

- Leptin adipose suppresses appetite- ↑ Fat = ↑ leptin = ↓ appetite- ↓ Fat = ↓ leptin = ↑ appetite

• What happens if there is a mutation in the leptin system?

1st 2nd 3rd

Figure 41.6 A ravenous rodent

Chapter 41: Animal Nutrition

1. Why do we eat?2. What are the 4 main feeding mechanisms of feeding?3. When our bodies need energy, what is the order of fuel usage?4. How is appetite regulated in the body? 5. What happens if there is a mutation in the leptin system?6. What are essential nutrients & what are the 4 classes?

- Nutrients our bodies cannot make- Essential amino acids (8)- Essential fatty acids – certain unsaturated FAs – linoleic acid- Vitamins- Minerals

Figure 41.10 Essential amino acids from a vegetarian diet

Corn (maize)and other grains

Beansand other legumes

Essential amino acids for adults

Methionine

Valine

Threonine

Phenylalanine

Leucine

Isoleucine

Lysine

Tryptophan

Table 41.1 Vitamin Requirements of Humans

Table 41.2 Mineral Requirements of Humans

Chapter 41: Animal Nutrition

1. Why do we eat?2. What are the 4 main feeding mechanisms of feeding?3. When our bodies need energy, what is the order of fuel usage?4. How is appetite regulated in the body? 5. What happens if there is a mutation in the leptin system?6. What are essential nutrients & what are the 4 classes?

- Nutrients our bodies cannot make- Essential amino acids (8)- Essential fatty acids – certain unsaturated FAs – linoleic acid- Vitamins- Minerals

7. What is the difference between malnourished & undernourished?- Under – get all essentials…just not enough- Mal – missing some essentials

8. How is food processed?

Figure 41.12 The four stages of food processing

Piecesof food

Smallmolecules

Mechanicaldigestion

Food

Chemical digestion(enzymatic hydrolysis)

Nutrient moleculesenter body cells

Undigested material

INGESTION1 DIGESTION2 ELIMINATION4ABSORPTION3

Chapter 41: Animal Nutrition

1. Why do we eat?2. What are the 4 main feeding mechanisms of feeding?3. When our bodies need energy, what is the order of fuel usage?4. How is appetite regulated in the body? 5. What happens if there is a mutation in the leptin system?6. What are essential nutrient & what are the 4 classes?7. What is the difference between malnourished & undernourished?8. How is food processed?9. What is the path that food takes through us?

Mouthesophagusstomachsmall intestinelarge intestinerectumtoilet

IIeumof small intestine Duodenum of

small intestine

Appendix

Cecum

Ascendingportion of large intestine

Anus

Small intestine

Large intestine

Rectum

Liver

Gall-bladder

Tongue

Oral cavity

Pharynx

Esophagus

Stomach

Pyloricsphincter

Cardiacorifice

Mouth

Esophagus

Salivaryglands

Stomach

Liver

Pancreas

Gall-bladder

Large intestines

Small intestines

RectumAnus

Parotid glandSublingual gland

Submandibular gland

Salivaryglands

A schematic diagram of the human digestive system

Figure 41.15 The human digestive system

Pancreas

Chapter 41: Animal Nutrition

1. Why do we eat?2. What are the 4 main feeding mechanisms of feeding?3. When our bodies need energy, what is the order of fuel usage?4. How is appetite regulated in the body? 5. What happens if there is a mutation in the leptin system?6. What are essential nutrient & what are the 4 classes?7. What is the difference between malnourished & undernourished?8. How is food processed?9. What is the path that food takes through us?

Mouthesophagusstomachsmall intestinelarge intestinerectumtoilet10. Let’s find out what happens along the way?

Esophagus

Tongue

Pharynx

GlottisLarynx

Trachea

Bolus of food

Epiglottisup

To lungs To stomach

Esophageal sphinctercontracted

Figure 41.16 From mouth to stomach: the swallowing reflex and esophageal peristalsis (layer 1)

Figure 41.16 From mouth to stomach: the swallowing reflex and esophageal peristalsis (layer 2)

Esophagus

Epiglottis down

Tongue

Pharynx

GlottisLarynx

Trachea

Bolus of food

Epiglottisup

To lungs To stomach

Esophageal sphinctercontracted

Glottis upand closed

Esophageal sphincterrelaxed

Figure 41.16 From mouth to stomach: the swallowing reflex and esophageal peristalsis (layer 3)

Esophagus

Epiglottis down

Tongue

Pharynx

GlottisLarynx

Trachea

Bolus of food

Epiglottisup

To lungs To stomach

Esophageal sphinctercontracted

Glottis upand closed

Esophageal sphincterrelaxed

Glottisdown and open

Esophageal sphinctercontracted

Epiglottisup

Relaxedmuscles

Contractedmuscles

Relaxedmuscles

Figure 41.21 Flowchart of enzymatic digestion in the human digestive system

Oral cavity,pharynx,esophagus

Carbohydrate digestion

Polysaccharides(starch, glycogen)

Disaccharides(sucrose, lactose)

Salivary amylase

Smaller polysaccharides,maltose

Stomach

Protein digestion Nucleic acid digestion Fat digestion

Proteins

Pepsin

Small polypeptides

Lumen of small intes-tine

Polysaccharides

Pancreatic amylases

Maltose and otherdisaccharides

Epitheliumof smallintestine(brushborder)

Disaccharidases

Monosaccharides

Polypeptides

Pancreatic trypsin andchymotrypsin (These proteasescleave bonds adjacent to certainamino acids.)

Smallerpolypeptides

Pancreatic carboxypeptidase

Amino acids

Small peptides

Dipeptidases, carboxypeptidase, and aminopeptidase (These proteases split off one amino acid at a time, working from opposite ends of a polypeptide.)

Amino acids

DNA, RNA

Pancreaticnucleases

Nucleotides

Nucleotidases

Nucleosides

Nucleosidasesandphosphatases

Nitrogenous bases,sugars, phosphates

Fat globules (Insoluble inwater, fats aggregate asglobules.)

Bile salts

Fat droplets (A coating ofbile salts prevents small drop-lets from coalescing intolarger globules, increasingexposure to lipase.)

Pancreatic lipase

Glycerol, fattyacids, glycerides

Figure 41.17 The stomach and its secretions

Pepsin (active enzyme)

HCl

Parietal cellChief cell

Stomach

Folds of epithelial tissue

Esophagus

Pyloric sphincter

Epithelium

Pepsinogen

3

2

1

Interior surface of stomach.The interior surface of the

stomach wall is highly folded and dotted with pits leading

into tubular gastric glands.

Gastric gland. The gastric glands have three types of cells

that secrete different components of the gastric juice: mucus cells,

chief cells, and parietal cells.

Mucus cells secrete mucus,which lubricates and protects

the cells lining the stomach.

Chief cells secrete pepsino-gen, an inactive form of the

digestive enzyme pepsin.

Parietal cells secretehydrochloric acid (HCl).

1 Pepsinogen and HCIare secreted into thelumen of the stomach.

2 HCl convertspepsinogen to pepsin.

3 Pepsin then activatesmore pepsinogen,starting a chainreaction. Pepsinbegins the chemicaldigestion of proteins.

5 µ

m

Small intestine

Cardiac orifice

- stomach epithelium secretes gastric juice- parietal cells secrete HCl & chief cells secrete pepsinogen- pH = 2

Figure 41.19 The duodenum

Liver Bile

Acid chyme

Stomach

Pancreatic juice

Pancreas

Intestinaljuice

Duodenum of small intestine

Gall-bladder

Figure 41.21 Flowchart of enzymatic digestion in the human digestive system

Oral cavity,pharynx,esophagus

Carbohydrate digestion

Polysaccharides(starch, glycogen)

Disaccharides(sucrose, lactose)

Salivary amylase

Smaller polysaccharides,maltose

Stomach

Protein digestion Nucleic acid digestion Fat digestion

Proteins

Pepsin

Small polypeptides

Lumen of small intes-tine

Polysaccharides

Pancreatic amylases

Maltose and otherdisaccharides

Epitheliumof smallintestine(brushborder)

Disaccharidases

Monosaccharides

Polypeptides

Pancreatic trypsin andchymotrypsin (These proteasescleave bonds adjacent to certainamino acids.)

Smallerpolypeptides

Pancreatic carboxypeptidase

Amino acids

Small peptides

Dipeptidases, carboxypeptidase, and aminopeptidase (These proteases split off one amino acid at a time, working from opposite ends of a polypeptide.)

Amino acids

DNA, RNA

Pancreaticnucleases

Nucleotides

Nucleotidases

Nucleosides

Nucleosidasesandphosphatases

Nitrogenous bases,sugars, phosphates

Fat globules (Insoluble inwater, fats aggregate asglobules.)

Bile salts

Fat droplets (A coating ofbile salts prevents small drop-lets from coalescing intolarger globules, increasingexposure to lipase.)

Pancreatic lipase

Glycerol, fattyacids, glycerides

Figure 41.20 Protease activation

PancreasMembrane-boundenteropeptidase

Trypsin

Active proteases

Lumen of duodenum

Inactivetrypsinogen

Other inactiveproteases

Chapter 41: Animal Nutrition

1. Why do we eat?2. What are the 4 main feeding mechanisms of feeding?3. When our bodies need energy, what is the order of fuel usage?4. How is appetite regulated in the body? 5. What happens if there is a mutation in the leptin system?6. What are essential nutrient & what are the 4 classes?7. What is the difference between malnourished & undernourished?8. How is food processed?9. What is the path that food takes through us?10. Let’s find out what happens along the way?11. What hormones control digestion?

- CCK – cholecystokinin- Secretin- Gastrin - Enterogastrone

Figure 41.22 Hormonal control of digestion

Amino acids or fatty acids in the duodenum trigger the release of cholecystokinin (CCK), which

stimulates the release of digestive enzymes from the pancreas and bile

from the gallbladder.

Liver

Gall-bladder

CCK

Entero-gastrone

Gastrin

Stomach

Pancreas

Secretin

CCK

Duodenum

Key

Stimulation

Inhibition

Enterogastrone secreted by the duodenum inhibits peristalsis and acid secretion by the stomach, thereby slowing digestion when acid chyme rich in fats enters the duodenum.

Secreted by the duodenum, secretin stimulates the pancreas to release sodium bicarbonate, which neutralizes acid chyme from the stomach.

Gastrin from the stomach recirculates via the bloodstream back to the stomach, where it stimulates the production of gastric juices.

This ensures enzymes are only present when needed.

Chapter 41: Animal Nutrition

1. Why do we eat?2. What are the 4 main feeding mechanisms of feeding?3. When our bodies need energy, what is the order of fuel usage?4. How is appetite regulated in the body? 5. What happens if there is a mutation in the leptin system?6. What are essential nutrient & what are the 4 classes?7. What is the difference between malnourished & undernourished?8. How is food processed?9. What is the path that food takes through us?10. Let’s find out what happens along the way?11. What hormones control digestion?12. How & where are nutrients absorbed?

- Facilitated diffusion & active transport of monomers- Microvilli of small intestine

Figure 41.23 The structure of the small intestine

Epithelialcells

Key

Nutrientabsorption

Vein carrying blood to hepatic portal vessel

Villi

Largecircularfolds

Intestinal wall Villi

Epithelial cells

Lymph vessel

Bloodcapillaries

Lacteal

Microvilli(brush border)

Muscle layers

Chapter 41: Animal Nutrition

1. Why do we eat?2. What are the 4 main feeding mechanisms of feeding?3. When our bodies need energy, what is the order of fuel usage?4. How is appetite regulated in the body? 5. What happens if there is a mutation in the leptin system?6. What are essential nutrient & what are the 4 classes?7. What is the difference between malnourished & undernourished?8. How is food processed?9. What is the path that food takes through us?10. Let’s find out what happens along the way?11. What hormones control digestion?12. How & where are nutrients absorbed?13. How & where are fats absorbed?

- Fats are emulsified by bile salts- Absorbed into the lacteal w/in the villi – lymph system

Figure 41.24 Digestion and absorption of fats

Large fat globules are emulsified by bile salts in the duodenum.

Fat globule

Lacteal

Epithelialcells ofsmallintestine

Micelles madeup of fatty acids,monoglycerides,and bile salts

Fat dropletscoated withbile salts

Bile salts

Digestion of fat by the pancreatic enzyme lipase yields free fatty acids and monoglycerides, which then form micelles.

Fatty acids and mono-glycerides leave micelles and enter epithelial cells by diffusion.

Chylomicrons containing fattysubstances are transported out of the epithelial cells and into lacteals, where they are carried away from the intestine by lymph.

1

2

3

4

Chapter 41: Animal Nutrition

1. Why do we eat?2. What are the 4 main feeding mechanisms of feeding?3. When our bodies need energy, what is the order of fuel usage?4. How is appetite regulated in the body? 5. What happens if there is a mutation in the leptin system?6. What are essential nutrient & what are the 4 classes?7. What is the difference between malnourished & undernourished?8. How is food processed?9. What is the path that food takes through us?10. Let’s find out what happens along the way?11. What hormones control digestion?12. How & where are nutrients absorbed?13. How & where are fats absorbed?

- Fats are emulsified by bile salts- Absorbed into the lacteal w/in the villi – lymph system

14. What is the purpose of the large intestine?- Absorption of water – makes feces solid- Home of endosymbiotic bacteria

Chapter 41: Animal Nutrition1. Why do we eat?2. What are the 4 main feeding mechanisms of feeding?3. When our bodies need energy, what is the order of fuel usage?4. How is appetite regulated in the body? 5. What happens if there is a mutation in the leptin system?6. What are essential nutrient & what are the 4 classes?7. What is the difference between malnourished & undernourished?8. How is food processed?9. What is the path that food takes through us?10. Let’s find out what happens along the way?11. What hormones control digestion?12. How & where are nutrients absorbed?13. How & where are fats absorbed?14. What is the purpose of the large intestine?15. What are some evolutionary adaptations of the vertebrate digestive system?

- Teeth shape- Intestinal length- Symbiotic adaptations for fermentation in herbivores- Storage chambers

Figure 41.26 Dentition and diet

(a) Carnivore

(b) Herbivore

(c) Omnivore

Incisors

Canines

Premolars

Molars

Figure 41.27 The digestive tracts of a carnivore (coyote) and herbivore (koala) compared

Carnivore Herbivore

Colon(largeintestine)

Cecum

StomachSmall intestine

Small intestine

Figure 41.28 Ruminant digestion

Reticulum. Some boluses also enter the reticulum. In both the rumen and the reticulum, symbiotic prokaryotes and protists (mainly ciliates) go to work on the cellulose-rich meal. As by-products of theirmetabolism, the microorganisms secrete fatty acids. The cow periodically regurgitates and rechews the cud (red arrows), which further breaks down thefibers, making them more accessible to further microbial action.

Rumen. When the cow first chews andswallows a mouthful of grass, boluses(green arrows) enter the rumen.

1

Intestine

2

Omasum. The cow then reswallowsthe cud (blue arrows), which moves tothe omasum, where water is removed.

3 Abomasum. The cud, containing great numbers of microorganisms, finally passes to the abomasum for digestion by the cow‘s own enzymes (black arrows).

4

Esophagus