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MCDB > CHAPTER 51 ~ Nutrition, Digestion, Absorption > Flashcards

CHAPTER 51 ~ Nutrition, Digestion, Absorption Flashcards

1
Q

amino acids that humans need from Grains

A

Tryptophan, Methionine, Valine, Threonine, Phenylalanine, Leucine

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2
Q

amino acids that humans need from Legumes

A

Valine, Threonine, Phenylalanine, Leucine, Isoleucine, Lysine

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3
Q

human infants need what 4 extra amino acids?

A

histidine, tyrosine, cysteine, and arginine

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4
Q

why ingested proteins not just simply used “as is”?

A

macromolecules cannot be absorbed by epithelial cells lining gut; protein structure and function highly specific to species, so wouldn’t be compatible with humans’, and because foreign proteins would be attacked by immune system

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5
Q

Tissue Layers of the gut

A

1st: mucosa
2nd: submucosa
external to submucosa = two muscle layers, circular and longitudinal –>nerve net in between layers
serosa (visceral peritoneum)

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6
Q

1st layer Mucosa

A

delicate epithelial cells; secrete mucus to lubricate and protect walls of gut; some secrete HCl in stomach; absorb nutrients in some regions.

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7
Q

2nd layer Submucosa

A

blood and lymph vessels that carry absorbed nutrients to the rest of the body; network of nerves responsible for secretory and sensory functions

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8
Q

circular muscle layer

A

constricts the gut

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9
Q

longitudinal muscle layer

A

shortens length of gut

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10
Q

enteric nervous system

A

nerve nets b/n smooth muscle and in submucosa, neurons reside entirely inside the gut, and do not contribute synapses or neurons to CNS.

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11
Q

small intestine consists of…

A

duodenum, jejunum, and ileum

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12
Q

goblet cells

A

are among microvilli and secret lubricating mucus

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13
Q

hydrolytic enzymes

A

break down protein, carbs, and fat molecules into their monomers

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14
Q

Carbohydrase

A

hydrolyzes carbs

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15
Q

proteases

A

hydrolyze proteins

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16
Q

Lipase

A

hydrolyze fats

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17
Q

Nucleases

A

hydrolyze nucleic acids

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18
Q

salivary glands

A

secrete mucus and amylase

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19
Q

amylase

A

hydrolyzes bonds between the glucose monomers that make up starch - digests it into maltose (secreted by serous cells)

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20
Q

functions of saliva

A
  • lubrication and binding (binding of food into “bolus”)
  • coats oral cavity & esophagus = protect
  • solubizes dry food
  • important for oral hygiene (washes away food and contains lysozyme to lyse bact.)
  • initiates starch digestion
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21
Q

serous cells

A

secrete amylase

22
Q

swallowing:

A

soft palate pulled up while vocal chords pulled together to close larynx = larynx covered by epiglottis, esophageal sphincter relaxes to allow bolus to enter.

23
Q

peristalsis

A

undulating movement of the GI tract that permits food to be moved along caused by alternating contractions of circular and longitudinal smooth muscle layers

24
Q

stomach acid

A

HCl (pH 1-3)

  • secretes 2-3 liters gastric fluid/day
  • kills microorganisms
  • hydrolize acid-labile substances
  • activates pepsin
25
pepsin
endopeptidase --> major enzyme produced by stomach - secreted by enzyme-secreting or "zymogenic" cell as a zymogen called pepsinogen. - activated by low pH of stomach acid, once activated, newly formed pepsin can activate other pepsin molecules through autocatalysis.
26
zymogen
inactive enzyme precursor
27
how does HCl activate pepsin?
low pH activates pepsinogen by cleaving away a sequence of amino acids that masks the active site of the enzyme.
28
ulcers caused by
bacteria helicobacter pylori
29
side effects of untreated ulcers
indigestion, heartburn, gastric bleeding and stomach cancer
30
chyme
mixture of food and gastric juice in the stomach
31
what can be absorbed directly across stomach wall?
alcohol, aspirin, ad caffeine
32
Small Intestine
digestion of carbs and proteins CONTINUES, while digestion of fats and absorption of nutrients BEGINS.
33
Duodenum
(25 cm) = site of most digestion
34
Jejunum
2.5 m. along with ileum, is responsible for 90% of absorption of nutrients
35
Ileum
3.5 m. along with Jejunum, is responsible for 90% of absorption of nutrients
36
Liver
produces and secretes bile (made from bile salts from cholesterol) --> flows to small intestine through hepatic duct
37
bile
an emulsifier; disperses fat droplets into micelles --> increase surface area of fats that are exposed to lipases
38
micelles
stabilized tiny droplets of fat that can no longer aggregate due to bile salts
39
chylomicrons
largest lipoproteins, synthesized in mucosal cells of intestine; transport fats from intestine to adipose tissue (enter blood through thoracic ducts at base of the neck)
40
Lipoproteins
transport fats in aqueous circulatory system --> move fats from sites of storage to sites of use
41
High-Density Lipoprotein (HDL)
remove cholesterol from tissues --> carry it to liver for use in bile production = "good" cholesterol, high in fit people
42
Low-Density Lipoprotein (LDL)
transport cholesterol around body for storage and use in biosynthesis - 50% cholesterol = bad lipoproteins
43
Very Low-Density Lipoprotein (VLDL)
transport mostly triglycerides from liver to adipose tissue around body. "ugly" b/c excessive fat deposition and high risk for cardio disease
44
high LDL to HDL ration means
high risk for atherosclerotic heart disease
45
Pancreas
exocrine tissues of pancreas release a variety of digestive enzymes into the intestines. - Trypsinogen (activated to trypsin) - Bicarbonate secretion
46
Trypsinogen
zymogen released by the exocrine Pancreas; activated in duodenum by enterokinase into Trypsin. Active trypsin can activate other trypsinogens through autocatalysis. (if trypsin activated accidentally while still in pancreas, can cause pancreatitis!!)
47
Pancreatitis
accidental digestion of the pancreas via enzymes --> destroys both it's exocrine and endocrine functions
48
Bicarbonate secretion (HCO3-)
neutralizes acidic chyme that enters intestine from stomach --> intestinal digestive enzymes function better at neutral/slightly alkaline pH levels
49
membrane-bound peptidases (on microvilli):
final digestion takes place here; cleave peptides into tri-, dipeptides, and individual amino acids
50
Colon
absorbs water, nutrients, and ions to produce semisolid feces
51
prolonged intake of antibiotics =
vitamin deficiency because they kill intestinal bacteria that help with vitamin uptake

MCDB (6 decks)

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