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BIOL 260 > Animal Nutrition > Flashcards

Animal Nutrition Flashcards

1
Q

what are the four steps in digestion (4)

A
  1. ingestion
  2. digestion
  3. absorption
  4. elimination
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2
Q

what is the role of the digestive system

A
  • ingestion and digestion of food into component molecules and then absorption of molecules by intestine
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3
Q

what are the functions of the mouth (4)

A
  • ingestion
  • mechanical digestion
  • enzymatic digestion
  • not all species perform all types of digestion in their mouth
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4
Q

what kind of feeders are humans (2)

A
  • generalist feeders: omnivores that eat both plants and other animals
  • our digestive system is generalized
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5
Q

what is the function of the mouth in humans (3)

A
  • performs ingestion
  • mechanical digestion (chewing)
  • enzymatic digestion (saliva contains enzymes)
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6
Q

snakes are carnivores and tend to swallow their food whole: what type of digestion occurs in snake mouths

A
  • no types of digestion; mouth is only involved in ingestion
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7
Q

when flies land on food, they spit out liquid contained digestive enzymes before sucking up the resulting fluid: why types of digestion do fly mouths perform

A
  • enzymatic digestion
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8
Q

what does mouth anatomy and role depend on (2)

A
  • the food source

- the type of feeder

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9
Q

what are the feeder types (3)

A
  • bulk feeders: ingest large pieces of food
  • fluid feeders: ingest fluid
  • suspension and filter feeders: capture particles in the water column
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10
Q

what begins enzymatic digestion in humans

A
  • saliva
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11
Q

saliva (2)

A
  • human salivary glands secrete salivary amylase enzyme that performs enzymatic digestion of carbohydrates
  • contains water and mucus to help lubricate food
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12
Q

salivary amylase

A
  • digests glucose polymers such as starch and glycogen into disaccharides
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13
Q

do all humans have the same amount of amylase

A
  • humans vary in the amount of salivary amylase they produce
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14
Q

why does salivary amylase vary among humans (3)

A
  • related to dietary composition
  • due to the variation in the copy number of the salivary amylase gene
  • populations with traditionally high starch diets have additional copies of the amylase gene in their genomes
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15
Q

how does the amount of amylase influence behaviour (2)

A
  • amylase gene copy number in humans is associated with risk of obesity
  • the lower the copies of salivary amylase, the more likely a person is to be predisposed to obesity
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16
Q

why do most mammals lack salivary amylase

A
  • amount of salivary amylase activity is based on dietary types
  • species with specialized diets tend to have less salivary amylase activity, whereas those with broad diets tend to have higher salivary amylase activity
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17
Q

which dietary types are not likely to have salivary amylase (2)

A
  • herbivores and carnivores

- specialized feeders don’t need to taste/distinguish between food because their diet is so specific to one food type

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18
Q

how is saliva secretion regulation (2)

A
  • thought, taste, texture of food can stimulate saliva secretion
  • regulation by the autonomic nervous system, and more specifically the parasympathetic branch
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19
Q

autonomic nervous system (2)

A
  • two branched: parasympathetic and sympathetic

- branches act on similar organs, but tend to have opposite effects

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20
Q

parasympathetic activity

A
  • resting and digesting
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21
Q

sympathetic activity

A
  • fight or flight
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22
Q

salivary reflex (3)

A
  • thought of food in mouth or food being in mouth trigger salivary control centres in the hypothalamus
  • this increases parasympathetic activity and decreases sympathetic activity
  • causes salivary glands to increase saliva production
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23
Q

what type of digestion does the stomach perform (3)

A
  • mechanical
  • chemical
  • enzymatic
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24
Q

mechanical digestion in the stomach

A
  • peristalsis
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25
Q

chemical and enzymatic digestion in the stomach

A
  • secretion of acid (HCl) and enzymes that help to digest proteins
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26
Q

what is the function of the low pH (extremely acidic) environment of the stomach (2)

A
  • disrupts hydrogen bonds that stabilize secondary and tertiary structures of proteins in foods, denaturing them so they are more accessible to digestive enzymes
  • create low pH environment where stomach enzymes thrive
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27
Q

enzymatic digestion in the stomach

A
  • proteins are digested by the enzyme pepsin, which is only active at low pH
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28
Q

stomach anatomy (4)

A
  • stomach lining contains gastric pits/gastric glands
  • chief cells
  • parietal cells
  • goblet cells
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29
Q

chief cells

A

produce pepsinogen (pepsin precursor)

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30
Q

parietal cells

A
  • produce HCl
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31
Q

goblet cells

A
  • produce mucus
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32
Q

pepsin activation in the stomach (3)

A
  • pepsin synthesized in inactive form (called pepsinogen)
  • low pH causes pepsinogen to change conformation: it attacks itself and cuts out a part of protein to expose the pepsin active site that can digest proteins
  • pepsin can also digest pepsinogen and active it, called positive feedback
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33
Q

what stops the stomach from digesting itself

A
  • stomach mucus
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34
Q

stomach mucus (2)

A
  • produced by goblet cells

- contains bicarbonate that neutralizes acid and mucins that make it thick

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35
Q

stomach ulcers (3)

A
  • bacteria can penetrate the mucus layer lining of the stomach
  • it can then damage the goblet cells
  • loss of mucus exposes cells to stomach acids, causing ulcers
36
Q

how is stomach acid secretion stimulated/inhibited (3)

A
  1. sight, smell, taste or though of food stimulates secretion
  2. presence of food in the stomach stimulates secretion
  3. presence of food in intestine inhibits secretion
37
Q

acid reflux (3)

A
  • if the sphincter between esophagus and stomach doesn’t tightly close between swallows, acid from the stomach can come back up into the esophagus
  • this can damage the cells of the esophagus and burning sensations near the heart
  • can lead to esophageal cancer as there is selection for fast-dividing cells to replace damaged ones
38
Q

lumen (2)

A
  • interior space in parts of the digestive system

- part of the outside of the body

39
Q

chemical digestion

A
  • requires corrosive chemicals that can damage more sensitive organs
40
Q

which dietary types are likely to have salivary amylase

41
Q

digestive enzymes

A
  • increase rate at which specific nutrients are broken down
42
Q

what are the chemicals that can stimulate/inhibit stomach acid secretion (4)

A 
stimulate:
- acetylcholine
- histamine
- gastrin
inhibit:
- somatostatin
43
Q

when are gastrin levels high (3)

A
  • during the “on” system, when we want to produce stomach acid
  • when the stomach pH is high due to neutral foods entering the stomach
  • this is likely during the thought/taste/smell of food or when food is in the stomach
44
Q

what is “off system” stomatostatin

A
  • when stomach pH is low
45
Q

what is the role of the small intestine in digestion (2)

A
  • performs enzymatic and chemical digestion

- secretions from the pancreas and the gall bladder are important

46
Q

pancreatic secretions (4)

A
  • lipase
  • amylase
  • protease
  • bicarbonate
47
Q

why is bicarbonate secreted at the beginning of the small intestine (4)

A
  • to neutralize incoming stomach acid
  • to protect the lining of the intestine
  • to allow intestinal digestive enzymes to function by altering pH
  • to lubricate the small intestines
48
Q

pancreatic amylase (3)

A
  • all vertebrates secrete amylase into the intestine
  • allows digestion of glucose polymers (starch and glycogen) to disaccharides
  • amylase on intestinal wall digests the disaccharides into monosaccharides that can be absorbed
49
Q

disaccharides

A
  • maltose, sucrose, lactose
50
Q

monosaccharides

A
  • glucose, fructose, galactose
51
Q

pancreatic protease activation (2)

A
  • pancreas will secrete a variety of proteases in their inactive form
  • they must be activated when they reach the small intestine through enzymatic activation
52
Q

why are pancreatic proteases secreted in their inactive form

A
  • inactive when they are not needed to prevent damage to intestinal wall
53
Q

final step of protein digestion (2)

A
  • occurs inside intestinal cells by intracellular peptidase enzymes
  • additional protein digesting inside cells that turn smaller peptides into amino acids
54
Q

digestion of fats (3)

A
  • requires both pancreatic and gall bladder secretions
  • bile salts from gall bladder break large fat droplets into small ones
  • pancreatic lipases digest fat droplets into glycerol and fatty acyds
55
Q

role of the large intestine (3)

A
  • primary role: water re-absorption
  • absorption of nutrients
  • home to many microorganisms that contribute to digestion
56
Q

colonic bacteria (3)

A
  • present in all vertebrate organisms
  • bacteria cells outnumber human cells greatly
  • symbiotic relationship: repress the growth of pathogenic microbes and digest nutrients into forms that can be reabsorbed in exchange for suitable habitat
57
Q

microbiome nature (3)

A
  • differs between individuals
  • lifestyle can change the microbiome composition
  • composition will affect how body reacts to nutrients (digests nutrients and gain/lose of weight): transfer of microbiome from an obese mice will predispose the mouse to obesity
58
Q

fecal transplantation (2)

A
  • can be used to treat an infection that causes relentless diarrhea
  • feces from a healthy patient are extracted and transferred to a patient with the disease
59
Q

cellulose (3)

A
  • one of the most abundant organic molecules on earth
  • polymer of glucose found in plant cell walls
  • contains glucose linked in specific way that differs from starch and glycogen
60
Q

why is cellulose difficult to digest (2)

A
  • no animal expresses the cellulase enzyme needed to break these bonds
  • instead, commensal bacteria can digest the cellulose into glucose
61
Q

where are the bacteria that digest cellulose found (2)

A
  • the large intestine, particularly the cecum (or appendix in humans)
  • cecum can vary in size: small in humans; so large in herbivores that it forms an outpocketing of the large intestine
62
Q

hindgut fermenters (2)

A
  • herbivores with a large cecum at the backend of the digestive system
  • large cecum acts as a fermentation chamber for cellulose digestion
63
Q

hindgut fermenters: body size effects (2)

A
  • small animals have a large cecum and small colon

- larger animals have a large cecum and a very large colon

64
Q

small hindgut fermenters (2)

A
  • have a large cecum

- “home” for commensal bacteria to digest cellulose

65
Q

large hindgut fermenters (3)

A
  • have a large colon, and may or may not have a large cecum
  • “home” for commensal bacteria that digest cellulose
  • large colon allows absorption of nutrients
66
Q

foregut fermenters/ruminants (4)

A
  • have specialized pocket of the stomach that houses bacteria and acts as a fermentation chamber to digest cellulose
  • bacterial waste products and dead bacteria are digested in the rest of the intestine
  • produce nutrients for the animal
  • more efficient than hindgut fermenters; these animals don’t need to eat their poop
67
Q

how to identify a foregut fermenter

A
  • look for complicated stomach with outpockets
68
Q

nutrient absorption (2)

A
  • most nutrient absorption occurs in the intestines

- small intestine deals with absorption of peptides, amino acids, glucose, fructose, fats, water, minerals, and vitamins

69
Q

stomach absoprtion

A
  • lipid-soluble substances such as alcohol and aspirin
70
Q

large intestine absorption

A
  • ions, water, minerals, vitamins, and organic molecules
71
Q

small intestine environment (2)

A
  • very long

- highly folded surface increases surface area for absorption of nutrients

72
Q

what would happen to glucose transport into the blood if intestinal ATP levels were decreased

A
  • it would decrease
73
Q

what would happen to glucose transport into the blood if [Na+] was greatly reduced in the intestinal lumen

A
  • no [Na+] gradient, so decrease
74
Q

what are the 3 transporters that take up amino acids in the intestines (3)

A
  1. a sodium amino acid (Na/AA) co-transporter
  2. a passive amino acid transporter
  3. the Na+/K+ ATPase
75
Q

water absorption (2)

A
  • absorption/loss occurs in the intestine

- the colon is the most important intestinal region for the regulation of water because it determines stool consistency

76
Q

water movement

A
  • it is passive: net movement is driven by relative concentrations of solutions
  • moves through aquaporin pores and spaces between cells
77
Q

sodium uptake and water movement (3)

A
  • sodium uptake drives water movement
  • Na+ is reabsorbed by secondary active transport and water passively follows between cells
  • allows regulation of water content of the stools
78
Q

osmotic diarrhea (4)

A
  1. ingestion of a non-absorbable solute
  2. increases osmolarity in large intestines
  3. fluid entry into lumen of intestine
  4. diarrhea
79
Q

common causes of osmotic diarrhea (4)

A
  • lactose
  • sorbitol
  • high fructose drinks/fruits
  • some laxatives
80
Q

cholera cause (4)

A
  • vibrio cholerae bacteria release a toxin
  • toxin binds tp a receptor on surface of cells in large intestine
  • causes cells to secrete ions into intestine
  • water follows and causes diarrhea; leads to death in some cases where there is too much water loss
81
Q

lactose (2)

A
  • primary sugar in milk

- broken down by the enzyme lactase

82
Q

lactose intolerant (2)

A
  • although most mammals can digest lactose when they are young, they lose this ability as adults
  • due to loss of lactase activity
83
Q

lactose tolerant

A
  • the people who retain the ability to digest lactose as adults
84
Q

what happens to undigested lactose (4)

A

travels to the colon where:

  • causes osmotic diarrhea
  • lactose is broken down by bacteria in the colon
  • releases methane, carbon dioxide, and hydrogen gas
  • causes bloating, abdominal pain, and flatulence
85
Q

why/where did lactase persistence evolve (2)

A
  • in the populations that practiced pastoralism (herding animals)
  • happened in independent evolutionary events in a regulation gene that neighbours the lactase gene
86
Q

did lactase persistence rise in all pastoralists societies (2)

A
  • no, asian pastoralists lack the lactase persistence gene

- they often drank pre-fermented milk and ate cheese

BIOL 260 (10 decks)

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