1

ANIMAL NUTRITION

2

Figure 41.1 Homeostatic regulation of cellular fuel

3

Figure 41.2 A ravenous rodent

Leptin receptors are found in high concentrations in the hypothalamus, region of the brain that’s known to be involved in regulating appetite and metabolism.

4

Figure 41.4 Essential amino acids from a vegetarian diet

5

Table 41.1 Vitamin Requirements of Humans: Water-Soluble Vitamins

6

Table 41.1 Vitamin Requirements of Humans: Fat-Soluble Vitamins

7

Table 41.2 Mineral Requirements of Humans

8

Figure 41.10 Intracellular digestion in Paramecium

Paramecium Still Images

9

Figure 41.11 Extracellular digestion in a gastrovascular cavity

Cnidarians

Nematocysts

10

Figure 41.12 Alimentary canals

11

Figure 41.13 The human digestive system

12

Figure 41.14 From mouth to stomach: the swallowing reflex and esophageal peristalsis (Layer 1)

Components of Saliva

Mucin

Buffers

Antibacterial agents

Salivary amylase

When not swallowing, the glottis is open.

13

Figure 41.14 From mouth to stomach: the swallowing reflex and esophageal peristalsis (Layer 2)

When swallowing: the glottis moves down closing off the trachea and bolus moves down esophagus.

14

Figure 41.14 From mouth to stomach: the swallowing reflex and esophageal peristalsis (Layer 3)

15

Figure 41.15 Secretion of gastric juice

Gastric Juice

a) Pepsin and pepsin- ogen (zymogen)

b) HCl

Positive feedback: some activation of pepsinogen increases production of pepsin.

Heliocobacter pylori

16

STOMACH

Stimulation

Gastrin from stomach into circulatory system

stimulates release of

Pepsin

HCl Pepsinogen

17

Figure 41.16 The duodenum

Duodenal ulcers

18

Figure 41.17 Enzymatic digestion in the human digestive system

19

CHO Digestion

Sucrase, lactase

Protein Digestion

Trypsin(trypsinogen) and chymotrypsin (chymotrypsinogen)

look for specific bonds in polypeptides and make smaller fragments.

Procarboxypeptidase (zymogen) for carboxypeptidase which will split one amino acid off of a polypeptide at a time (at the COOH end)

Aminopeptidase as at the amino end of the polypeptide chain.

All this is triggered by enteropeptidase.

20

Figure 41.18 Activation of protein-digesting enzymes in the small intestine

21

What Regulates the Secretion of These Digestive Enzymes?

1. Secretin

2. Cholecystokinin( CCK )

3. Enterogastrone

22

Small Intestine

Receives low amino acids and fatty acids fats

pH chyme

Enterogastrone

Secretin Cholecystokinin (CCK) (slows passage of food into SI)

(from intestinal wall) Pancreas Gall Bladder Bile

Procarboxypeptidase carboxypeptidase

(Pancreas)

HCO3- +

Chymotrypsinogen chymotrypsin

+

Trypsinogen trypsin

23

Figure 41.19 The structure of the small intestine

24

Evolutionary Adaptations of Vertebrate Digestive System

1. Dentition and Diet

a) Mammalian vertebrates

b) Nonmammalian vertebrates

2. Length of vertebrate digestive system

25

Figure 41.20 Dentition and diet

26

Figure 41.21 The digestive tracts of a carnivore (coyote) and a herbivore (koala) compared

27

Figure 41.22 Ruminant digestion

28

Symbiotic Relationships in Herbivores

Vertebrates and termites have microorganisms (protists and bacteria). . .

29

What Is Fat?

Fat Or Adipose As A Tissue

• Fat is used for energy storage and insulation

• It is involved in metabolism. It really doesn’t just sit there.

• Fat cells express certain genes and secrete hormones as well as other signaling molecules.

30

What Is Fat?

Fat As a Cell

• Fat cells are called adipocytes

• Adipocytes are specialized for storing fat.

• Inside the adipocyte are the fat droplets

31

What Is Fat?

Fat As a Molecule

• It’s a lipid

• Triglycerides are a form of lipid and they consist of one glycerol molecule and 3 fatty acids (remember?)

• Triglycerides store 3 times more energy than sugars per gram.

• Saturated Fats vs. unsaturated fats

32

How the Body Processes Fat

The body’s primary energy source is glucose

Any excess glucose is stored in your muscles and liver as glycogen.

Any excess beyond this is converted to fat (triglycerides) for storage.

Between meals when glucose levels drop, either

1) glycogen is broken down to glucose (glycogenolysis) or

2) the body makes glucose from other precursors (gluconeogenesis)

3) triglycerides can also be catabolized for energy (glycerol is used for gluconeogenesis and the fatty acids are broken into 2 carbon units for the Krebs cycle

33

How the Body Processes Fat

Cholesterol

• Cholesterol is a form of lipid

• Component of cell membranes

• Used to make steroid molecules and also bile salts

• Transported with fat in what are called “lipoproteins.”

• Low Density Lipoproteins (LDLs) vs. High Density Lipoproteins (HDLs)

34

Transportation of Fat

Lipoprotein Structure

• Phospholipids and cholesterol form a sphere on the outside (where it would contact water). Therefore the hydrophilic regions are pointing outward.

• Apolipoproteins, another protein, are also on the surface and these regulate the function of the lipoproteins.

• Inside this sphere are triglycerides and cholesterol esters.

35

36

Transportation of Fat

Lipoprotein Size and Origin

Small Intestine Transports fat and cholesterol absorbed from digested food from the gut to the rest of body.

Liver Supply the body with triglyc- erides synthesized in the liver.

Converted VLDL Supply the body with cholesterol

Multiple Sources Collect excess cholesterol and transport it to the liver.

chylomicron

VLDL

LDL

HDL

37

Transportation of Fat

Lipoprotein Conversion

• The lipoproteins can be converted from:

chylomicron

Chylomicron remnants

LDL

VLDL

Fatty Acid Transport

• Fats are leased from the fat cells in the form of fatty acids.

• These become bound to a protein, albumin, that can transport them throughout the body.

• Each albumin molecule can carry 7 fatty acids.

38

What Goes On Inside Cells?

There are regulatory molecules that control what happens to fat

• PPARγ: fat sensor that belongs to a class of molecules called nuclear receptors (found in the nucleus).

• PPARγ molecules bind to fatty acids, become activated and cause cells to store fat.

• PPARδ: fat sensor that belongs to a class of molecules called nuclear receptors (found in the nucleus).

• PPARδ will bind to fatty acids, become activated and cause cells to metabolize of “burn” fat.

39

Endocrine Regulation?

Your hypothalamus in your brain is a center for many activities, one of which is appetite and hunger.

• Appetite is stimulated by a hormone called ghrelin.

• Appetite is suppressed by leptin, insulin, cholecystokinin and 2 other peptides (peptide YY and glucagon-like peptide-I)

Normally, the more fat you have in a cell, the more you have a signal that tells the brain it can reduce food intake. In obese people, the brain does not sense these higher levels of leptin; they are less responsive to the signal that tells them to reduce food intake.

40

How the Body Processes Fat: Part II

From Mouth To Stomach

• Triglycerides are not digested in mouth but the complex carbohydrates do get broken down into complex sugars.

• So in the stomach you have triglycerides and complex sugars and off they go to the small intestine.

41

In Small Intestine

• Bile acids made in liver and stored in the gall bladder are delivered to the duodenum. Bile salts break up the triglycerides into small droplets.

• Pancreas secretes lipase which removes the fatty acids from the triglycerides.

• The triglycerides are digested into one fatty acid attached to glycerol, a monoglyceride, and this can be absorbed into the blood stream.

42

At the Liver

• The liver can take stored or absorbed glucose and convert it to:

• glycerol (which can then become a triglyceride)

• glycogen

• fatty acids (which can then become a triglyceride)

43

• These triglycerides can leave the liver and go to the blood stream and:

• combine with proteins to become VDLP and go to a muscle cell

• or they can go to a fat cell and become fatty acids and be stored

At The Muscle Cell

• the triglycerides can become fatty acids and be used for energy

44

What About The Cholesterol

• The cholesterol can be transported as LDLs which can go to a muscle cell or to a fat cell.

• Some cholesterol can be transported as HDLs and go the liver and be stored or released back into the blood.