1. ANIMAL NUTRITION

2. Figure 41.1 Homeostatic regulation of cellular fuel

3. Figure 41.2 A ravenous rodent
Leptin:
1996: identified a gene in mice that regulates body weight.
Took the leptin gene, cloned it, injected its product into mice and found that it dramatically reduced the animal’s body weight.
The effect was strongest in those mice with defective obese genes.
Leptin Receptors:
identified the gene
in obese mice, there is a shortened receptor that fails to pass on the message that binding has occurred.
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.
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
Cilia direct food (bacteria) into the oral groove
The food vacuole is simply a small “stomach” or digestive compartment
Cytoplasmic streaming moves the food vacuole the Paramecium
Enzymes are secreted into the vacuole. Amino acids, sugars, etc are transported across the membrane of the food vacuole and into the cytoplasm.
Paramecium Still Images

9. Figure 41.11 Extracellular digestion in a gastrovascular cavity
Cnidarians
Nematocysts
Extracellular digestion
Cnidarian
Hydras are carnivores
Sting prey with nematocysts and use tentacles to pull the prey in.
Gastrodermis secretes digestive enzymes
Cells lining the cavity engulf the food particles and most of digestion occurs intracellularly.
Waste products exit through mouth.

10. Figure 41.12 Alimentary canals
Earthworm
Muscular pharynx sucks soil in through mouth
Esophagus
Crop: stored and moistened
Gizzard: bits of sand and gravel to grind up food
Digestion and absorption in intestine
Folds in intestine increase surface area
Grasshopper
Same basic process except the gastric ceca pouches absorb the nutrients.
Birds

11. Figure 41.13 The human digestive system

12. When not swallowing, the glottis is open.
Figure 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.
Nervous reflex that causes salivation
1 liter of saliva per day
Saliva contains:
a) mucin which lubricates the food for swallowing
b) buffers to prevent tooth decay
c) antibacterial agents because of the bacteria in the food
Pharynx: same as throat
opens to both the trachea and esophagus

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
a) Pepsin and pepsin- ogen (zymogen)
b) HCl
Positive feedback: some activation of pepsinogen increases production of pepsin.
Gastric Juice
HCl: breaks up proteins; also kills bacteria; secreted by parietal cells
Pepsin: hydrolysis of proteins; acts between specific amino acids.
Pepsinogen: secreted from the chief cells
Heliocobacter pylori

16. Gastrin from stomach into circulatory system
Stimulation
Gastrin from stomach into circulatory system
stimulates release of
Pepsin
HCl Pepsinogen

17. Figure 41.16 The duodenum Duodenal ulcers SI: 6 meters long
inside diameter is smaller than large intestine
Duodenum: receives secretions from:
1) liver, gall bladder and pancreas
2) Bile: contains pigments from RBC destruction in liver and gives feces its color

18. Figure 41.17 Enzymatic digestion in the human digestive system

19. Trypsin(trypsinogen) and chymotrypsin (chymotrypsinogen)
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.
CHO Digestion:
Salivary amylases
Pancreatic amylases
polysaccharides into disaccharides
Sucrase: sucrose into glucose and fructose

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

21. What Regulates the Secretion of These Digestive Enzymes?
Secretin
Cholecystokinin( CCK )
3. Enterogastrone
Secretin: released from the intestinal wall when the pH is low, goes to blood, travels to pancreas and causes the release of bicarbonate
Cholecystokinin (CCK): produced by the duodenum; stimulates the gall bladder to release bile .
Also stimulates pancreases to secrete its CHO digesting enzymes.
3. Enterogastrone: this slows the stomach movements for fat digestion.

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
Lacteal: within each villus is a collection of capillaries and a small lymph vessel. So the digested materials enter this capillaries.
Hepatic Portal Vessel: carries all nutrients to liver for metabolic processes balance.

24. Evolutionary Adaptations of Vertebrate Digestive System
Dentition and Diet
a) Mammalian vertebrates
b) Nonmammalian vertebrates
Length of vertebrate digestive system
Dentition and Diet
a) Mammalian vertebrates
-Carnivores: pointed incisors and canines; premolars and molars crushing of food
-Herbivorous:cows have broad surfaces for the grinding of food.
-Omnivores (humans) unspecialized dentition; we have incisors and canines and the flat surfaces of premolars and molars but there is absence of specialization.
Nonmammalian Vertebrates
a) Snakes have modified teeth – fangs – for injecting venom
they also can move their lower jaw around their prey for swallowing.
Length of the Vertebrate Digestive System
Herbivores and omnivores have longer digestive tracts when compared to their body size vs. carnivores.
Increased digestion time for the vegetation.

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)
Bacteria and protists live in special fermentation chambers
Some live in crop or esophageal pouch Hoatzin, an herbivorous bird in S. American rain forest)
Horses: cecum, area between the large and small intestine, that houses microog.
Rabbits: large intestine and cecum.
Animals with microorg. In the large intestine do not get much of a chance to absorb the nutrients produced by the microorganisms. These nutrients are lost in the feces. Rabbits and other rodents therefore eat some of their feces, and therefore put the microorg. into their intestine that way. (Rabbit pellets are the feces that have passed through a second time)
Have the enzymes to digest the cellulose
Many times the microorganisms use the sugars from the cellulose and other minerals to make other vitamins and amino acids for the host.

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
glycogen is broken down to glucose (glycogenolysis) or
the body makes glucose from other precursors (gluconeogenesis)
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.

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
VLDL
LDL
Chylomicron remnants
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.