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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
Q

pepsin

A

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
Q

zymogen

A

inactive enzyme precursor

27
Q

how does HCl activate pepsin?

A

low pH activates pepsinogen by cleaving away a sequence of amino acids that masks the active site of the enzyme.

28
Q

ulcers caused by

A

bacteria helicobacter pylori

29
Q

side effects of untreated ulcers

A

indigestion, heartburn, gastric bleeding and stomach cancer

30
Q

chyme

A

mixture of food and gastric juice in the stomach

31
Q

what can be absorbed directly across stomach wall?

A

alcohol, aspirin, ad caffeine

32
Q

Small Intestine

A

digestion of carbs and proteins CONTINUES, while digestion of fats and absorption of nutrients BEGINS.

33
Q

Duodenum

A

(25 cm) = site of most digestion

34
Q

Jejunum

A

2.5 m. along with ileum, is responsible for 90% of absorption of nutrients

35
Q

Ileum

A

3.5 m. along with Jejunum, is responsible for 90% of absorption of nutrients

36
Q

Liver

A

produces and secretes bile (made from bile salts from cholesterol) –> flows to small intestine through hepatic duct

37
Q

bile

A

an emulsifier; disperses fat droplets into micelles –> increase surface area of fats that are exposed to lipases

38
Q

micelles

A

stabilized tiny droplets of fat that can no longer aggregate due to bile salts

39
Q

chylomicrons

A

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
Q

Lipoproteins

A

transport fats in aqueous circulatory system –> move fats from sites of storage to sites of use

41
Q

High-Density Lipoprotein (HDL)

A

remove cholesterol from tissues –> carry it to liver for use in bile production = “good” cholesterol, high in fit people

42
Q

Low-Density Lipoprotein (LDL)

A

transport cholesterol around body for storage and use in biosynthesis - 50% cholesterol = bad lipoproteins

43
Q

Very Low-Density Lipoprotein (VLDL)

A

transport mostly triglycerides from liver to adipose tissue around body. “ugly” b/c excessive fat deposition and high risk for cardio disease

44
Q

high LDL to HDL ration means

A

high risk for atherosclerotic heart disease

45
Q

Pancreas

A

exocrine tissues of pancreas release a variety of digestive enzymes into the intestines.

  • Trypsinogen (activated to trypsin)
  • Bicarbonate secretion
46
Q

Trypsinogen

A

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
Q

Pancreatitis

A

accidental digestion of the pancreas via enzymes –> destroys both it’s exocrine and endocrine functions

48
Q

Bicarbonate secretion (HCO3-)

A

neutralizes acidic chyme that enters intestine from stomach –> intestinal digestive enzymes function better at neutral/slightly alkaline pH levels

49
Q

membrane-bound peptidases (on microvilli):

A

final digestion takes place here; cleave peptides into tri-, dipeptides, and individual amino acids

50
Q

Colon

A

absorbs water, nutrients, and ions to produce semisolid feces

51
Q

prolonged intake of antibiotics =

A

vitamin deficiency because they kill intestinal bacteria that help with vitamin uptake

MCDB (6 decks)

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