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Chapter 41: Animal Nutrition. 3 dietary categories. Herbivores eat mainly autotrophs (plants and algae) Carnivores eat other animals Omnivores consume animals as well as plants or algal matter. Diet. An adequate diet must satisfy 3 nutritional needs - PowerPoint PPT Presentation
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Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Chapter 41: Animal Nutrition
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
3 dietary categories
– Herbivores eat mainly autotrophs (plants and algae)
– Carnivores eat other animals– Omnivores consume animals as well as plants
or algal matter
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Diet
• An adequate diet must satisfy 3 nutritional needs– Chemical energy for all cellular work– The organic raw materials for biosynthesis– Essential nutrients, substances such as
vitamins that the animal cannot make for itself
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Why We Eat
• Animal’s diet must supply carbon skeletons and essential nutrients
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Essential Amino Acids• Animals require 20 amino acids
– Synthesize about half of them from the other molecules they obtain from their diet
• Essential amino acids– Must be obtained from food in preassembled
form
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Amino Acids
Essential Amino Acids Non-Essential Amino Acids
histidine alanine
isoleucine arginine*
leucine aspartic acid
lysine cysteine*
methionine glutamic acid
phenylalanine glutamine*
threonine glycine*
tryptophan proline*
valine serine*
tyrosine*
asparagine*
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• A diet that provides insufficient amounts of one or more essential amino acids causes protein deficiency
Figure 41.9
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Most plant proteins are incomplete in amino acid makeup
– eat a variety to get all the essential amino acids
Corn (maize)and other grains
Beansand other legumes
Essential amino acids for adults
Methionine
Valine
Threonine
Phenylalanine
Leucine
Isoleucine
Lysine
Tryptophan
Figure 41.10
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Vitamins
• Vitamins are organic molecules– Required in the diet in small amounts
• To date, 13 vitamins essential to humans– Have been identified
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Vitamins: Water Soluble
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Vitamins: Fat Soluble
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Minerals• Simple inorganic nutrients
– Usually required in small amounts
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Mineral requirements of humans
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The four stages of food processing
Figure 41.12
Piecesof food
Smallmolecules
Mechanicaldigestion
Food
Chemical digestion(enzymatic hydrolysis)
Nutrient moleculesenter body cells
Undigested material
INGESTION1 DIGESTION2 ELIMINATION4ABSORPTION3
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Basic Set up of our Digestive System
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
Parotid gland
Sublingual gland
Submandibular gland
Salivaryglands
Pancreas
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
The Oral Cavity, Pharynx, and Esophagus
• Digestion begins– And teeth chew food into smaller particles that
are exposed to salivary amylase, initiating the breakdown of carbohydrates into glucose polymers
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
The Stomach• Secretes gastric juice, which converts a meal
to acid chyme
• Gastric juice– Hydrochloric acid and the enzyme pepsin– pH around 2
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Enzymatic Action in the Small Intestine
• First portion of the small intestine (duodenum)
– Acid chyme from stomach mixes with digestive juices from the pancreas, liver, gallbladder, and intestine itself
Figure 41.19
Liver Bile
Acid chyme
Stomach
Pancreatic juice
Pancreas
Intestinaljuice
Duodenum of small intestine
Gall-bladder
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
The Pancreas
• The pancreas produces proteases, protein-digesting enzymes– That are activated once they enter the
duodenum
PancreasMembrane-boundenteropeptidase
Trypsin
Active proteases
Lumen of duodenum
Inactivetrypsinogen
Other inactiveproteases
Figure 41.20
pH change
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Hormones control the secretion of digestive enzymes
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 thePancreas to release sodiumbicarbonate, whichneutralizes acid chyme from the stomach.
Gastrin from the stomach stimulates the production of gastric juices.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Small Intestine: Organ of digestion and absorption
• The enormous microvillar surface area– Greatly increases the rate of nutrient
absorption
Epithelialcells
Key
Nutrientabsorption
Vein carrying blood to hepatic portal vessel
Villi
Largecircularfolds
Intestinal wallVilli
Epithelial cells
Lymph vessel
Bloodcapillaries
Lacteal
Microvilli(brush border)
Muscle layers
Figure 41.23
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Homeostatic mechanisms tell us what we need
• Homeostatic mechanisms manage animal’s energy budget
• Animal’s ATP generation– Based on the oxidation of energy-rich
molecules: carbohydrates, proteins, and fats
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Glucose Regulation as an Example of Homeostasis
• Animals store excess calories– As glycogen in the liver and muscles and as fat
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Glucose major fuel for cells
• Its metabolism, regulated by hormone action, is an important example of homeostasis
Figure 41.3
1 When blood glucose level rises, a gland called the pancreas secretes insulin,a hormone, into the blood.
Insulin enhances the transport of glucose into body cells and stimulates the liver and muscle cells to store glucose as glycogen. As a result, blood glucose level drops.
2
STIMULUS:Blood glucose
level risesafter eating.
Homeostasis:90 mg glucose/100 mL blood
STIMULUS:Blood glucose
level dropsbelow set point.
Glucagon promotesthe breakdown of
glycogen in theliver and the
release of glucoseinto the blood,
increasing bloodglucose level.
4
When blood glucose level drops, the pancreas secretes the hormone glucagon, which opposes the effect of insulin.
3
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Hormones regulate appetite (Controlled by Brain)
Leptin produced by Fat cells
Leptin
PYY
Insulin
Ghrelin
Secreted by the stomach wall, ghrelin is one of the signals that triggers feelings of hunger at mealtimes. In dieters who lose weight, ghrelin increases, 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 insulin suppresses appetite by acting on the brain.
CCK inhibits gastric emptying. It stimulates the pancreas to release digestive enzymes.Released by duodenum.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Mice that inherit a defect in the gene for leptin
– Become very obese
Figure 41.6