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biology 153 > digestive system (physiology) > Flashcards

digestive system (physiology) Flashcards

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1
Q

two forms of digestion

A

mechanical and chemical digestion

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2
Q

what is mechanical digestion

A

breakdown of large food particles into smaller food particles
-involves, teeth, stomach, small intestine
stomach is churning
small intestine is segmentation

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3
Q

what is chemical digestion

A

enzymatic breakdown of organic macromolecules into smaller molecules (monomers); chemical bonds broken

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4
Q

what are enzymes

A

proteins that catalyze biological reaction

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5
Q

how do enzymes facilitate chemical reactions in the body?

A

lower activation energy of biological reactions (allow them to take pace quickly at body temp)

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6
Q

can enzymes catalyze any reaction?

A

no they are very specific and bind to specific substrates

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7
Q

what are the reactants in an enzyme catalyzed reaction called

A

substrate

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8
Q

what are some factors that affect the rate of enzyme catalyzed reactions?

A

pH, enzyme concentration, temperature

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9
Q

enzyme has an active site for the substrate, and then..

A

enzyme-substrate complex forms, products are made.
products release energy when bonds are broken
energy is used to make ATP

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10
Q

enzyme is changed or unchanged

A

unchanged, can catalyze other reactions

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11
Q

chemical digestion involves _______ reactions

A

catabolic

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12
Q

catabolic reactions are ..?

A

exergonic/exothermic. energy is released when chemical bonds are broken, energy is used to make high energy phosphate bonds in ATP

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13
Q

what are the 3 main macromolecules in the diet that are digested chemically

A

protein, carbohydrate, fat (lipids)

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14
Q

chemical digestion of protein

A

very long polymer of amino acids- peptide with peptide bonds- amino acid

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15
Q

chemical digestion of carbohydrate

A

complex carb (starch, glycoge)- disaccharides (sucrose, maltose, lactose)- monosaccharides (glucose, fructose, galactose)

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16
Q

chemical digestion of fats (lipids)

A

triglyceride- glycerol and fatty acids

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17
Q

where does absorption of nutrients occur

A

mainly in small intestine (especially ileum and jejunum) across brush border membrane

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18
Q

the small nutrient molecules move into epithelial cells, then..

A

into blood or lymph capillaries (lacteals)

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19
Q

how are sugars and amino acids transported

A

by cotransport or facilitated diffusion

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20
Q

products of protein and carbohydrate digestion enter?

A

capillaries in the lamina propria- hepatic portal vein- liver

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21
Q

monoglycerides and fatty acids..

A

lipid soluble diffuse across brush border membrane, no transporters
-not water solube, must be coacted in proteins and phospholipids to be transported in blood or lymph

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22
Q

what are the lipoproteins called

A

chylomicrons

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23
Q

what are micelles

A

bile coated fat droplets containing fatty acids and monoglycerides

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24
Q

what happens when fatty acids and monoglycerides diffuse across c.m?

A

reassembled into triglycerides then combined with cholesterol, phospholipids, and proteins to form chylomicrons

25
Q

how do the chylomicrons leave into blood?

A

chylomicrons leave by exocytosis

-chylomicrons are too large to move into capillaries, so they are picked up by lacteals

26
Q

what do lacteals do

A

deliver fatty chyle to cisterna chyli- thoracic duct- veins

27
Q

where do chylomicrons go once they are in the blood?

A

-enzyme lipoprotein lipase in endothelium of capilaries breaks down the triglycerides into monoglycerides and fatty acids

28
Q

fatty acids are stored?

A

in adipose tissue (as triglycerides)
muscle (for energy)
liver (processing center)

29
Q

where are lipoproteins synthesized?

A

the liver

30
Q

lipoprotein function

A

deliver lipids (triglycerides, cholesterol) to and from liver and tissues

31
Q

LDL ?

A

low density lipoprotein (lots of lipid, less protein)

transports lipids from liver to tissues

32
Q

how does LDL transport lipids

A

receptor mediated endocytosis (pulls lipids into cells)

can be deposited in endothelium (becomes plaque under endothelium)

33
Q

HDH ?

A

high density lipoprotein (less lipid, more protein) good cholesterol
transports lipids from cells to liver, can be excreted in bile

34
Q

how are water soluble vitamins absorbed

A 
facilitated diffusion (C and B vitamins)
except B12 which must be bound to intrinsic factor glycoprotein secreted by parietal cells of stomach)
35
Q

how are fat soluble vitamins absorbed

A

A,D,E,K diffusion with lipids (incorporated into chylomicrons)

36
Q

what is pernicious anemia caused by

A

genetic defect in the gene that codes for intrinsic factors; individuals cannot absorb B12 which is required for cell division

37
Q

how are ions/ electrolytes absorbed

A

transporters are required, facilitated diffusion or active transport

38
Q

how does water enter the GI tract

A

from food/beverages and GI secretions

39
Q

how much water is ingested a day

A

2000 mL

40
Q

digestive secretions include?

A

saliva, gastric secretions, intestinal secretions, pancreatic secretions, bile

41
Q

water is reabsorbed by?

A

process of osmosis

42
Q

where is water reabsorbed

A

small intestine 97%
large intestine 6-7%
only about 150ml a day is excreted in feces

43
Q

what is digestion regulated by

A
  • hormones

- ANS: enteric plexus (network of sensory and motor neurons in GI tract)

44
Q

three phases of digestion

A
  1. cephalic phase
  2. gastric phase
  3. intestinal phase
45
Q

cephalic phase of digestion

A

before food enters stomach

-sight, smell, touch, taste, thought- hypothalamus- parasympathetic increases saliva and gastric juice secretion

46
Q

gastric phase of digestion

A

activated by arrival of food in the stomach

  • stimulates chemoreceptors and stretch receptors that increase gastric juice and gastric motility
  • gastrin secretion (hormone by G cells)
  • parasympathetic (vagus nerve)
47
Q

what is the intestinal phase

A

activated by arrival of acid chyme in duodenum
-chemoreceptors and stretch receptors
-duodena endocrine cells secrete hormones
(secretin and CCK- cholecystokinin)
-parasympathetic activation

48
Q

secretin causes

A

pancreatic NaHCO3 to increase
bile secretion by liver to increase
gastric secretion and motility to decrease

49
Q

CCK (cholecystokinin) causes

A 
pancreatic enzyme secretion to increase
gallbladder concentration to increase
relaxes hepatopancreatic sphincter
increase pancreatic NaHCO3
decrease gastric secretion and motility
50
Q

parasympathetic activation causes

A

increased intestinal motility, vagus nerve and reflexes

51
Q

GIP (glucose dependent insulinotropic peptide)

A
  • secreted when sugars and fats enter duodenum
  • stimulates insulin secretion by pancreas
  • stimulates lipogenesis in adipocytes
52
Q

VIP (vasoactive intestinal peptide)

A
  • stimulates intestinal glands to increase NaHCO3 and water secretion
  • dilates intestinal blood vessels to increase blood flow
53
Q

how is defecation controled

A

mass movements (peristalsis) cause the urge to defecate, initiated by arrival of food in stomach and intestine

54
Q

arrival of food causes which reflexes

A

gastrocolic and duodenocolic reflexes

55
Q

distension of rectum with feces causes

A

defecation reflex, relaxation of internal anal sphincter

56
Q

the internal sphincter is under what control?

A

parasympathetic, conscious control of external (voluntary)

57
Q

regulation of appetite?

A

satiety centers in hypothalamus regulate feeding behaviours

58
Q

short term regulation of appetite

A

stretch receptors in stomach decrease appetite

-ghrelin (hormone secreted by cells lining stomach when empty) increase appetite

59
Q

long term regulation of appetite

A

leptin (hormone secreted by adipose tissue)

increase adipose tissue, increases leptin, decreases appetite

biology 153 (17 decks)

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