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BIO 153 final (Lab Exam + Lecture) > Digestive physiology review > Flashcards

Digestive physiology review Flashcards

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1
Q

What is mechanical digestion

A

breakdown of large food particles into smaller food particles

  • Teeth
  • Stomach churning
  • Sm. Intestine segmentation
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2
Q

What is chemical digestion

A

enzymatic breakdown of organic macromolecules into smaller molecules (monomers)
*Chemical bonds are broken

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3
Q

what do enzymes do

A
  • lower energy requirement for rxn. to take place (catalyst proteins)
  • allow rxn’s to take place quickly even @ body temperature
  • Very Specific: Bind to substrates & produce products
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4
Q

what are the reactants in an enzymatic reaction called

A

substrates

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5
Q

what are the factors that affect the rate of enzyme catalyzed reaction

A

1) Ph
2) Temp
3) Soln. conc.

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6
Q

what is a catabolic reaction

A

large macromolecules/polumers are broken down into smaller monomers.
These are EXERGONIC/EXOTHERMIC (energy is released when the bonds are broken & it can be used to make ATP)

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7
Q

Explain protein, amino acid & peptides

A
  • Protein = very long polymer of amino acids
  • Peptides= a couple amino acids linked together
  • Amino acid = singular. R= the variable. There is 20 different ones
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8
Q

Explain complex carbohydrate/polysaccharide, disaccharides, and monosaccharides/simple sugar

A
  • Complex carbohydrate/polysaccharide: Starch or glycogen (many monosaccharides all linked together)
  • Disaccharides: Sucrose, maltose, lactose (2 monosaccarides)
  • Monosaccaride/simple sugar: just one. Glucose, fructose, galactose
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9
Q

explain a lipid triglyceride & glycerol & fatty acids

A

Triglyceride = glycerol + 3 fatty acids unsaturated or saturated
saturated =no double carbon bond
unsaturated = double carbon bond

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10
Q

Where can protein be digested into peptides and by what

A

1) stomach by pepsin
2) Duodenum by trypsin
3) sm. intestine by chymotrypsin
4) in sm intestine by carboxypeptidase

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11
Q

How is protein digested into peptides in the stomach

A

by pepsin, secreted by chief cells, activated by HCL.

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12
Q

how is protein digested into peptides in the duodenum

A

by trypsin, secreted by the pancreas

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13
Q

how is protein digested into peptides in the sm. intestine

A

by chymotrypsin, secreted by the pancreases & bu carboxypeptidase, secreted by the pancreas.

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14
Q

how are peptides digested into amino acids in sm intestine.

A

by peptidases secreted by the sm. intestine brush boarder enzymes.

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15
Q

What is so special about trypsin, chymotrypsin & carboxypeptidase

A

1) these proteases/peptidases are secreted by the pancreases as inactive proenzymes (can’t digest proteins).
2) Trypsinogen is activated by enteropeptidase (brush boarder enzyme)
3) Chymotrypsinogen & procarboxypeptidase are concerted by trypsin

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16
Q

how are complex carbs digested into tri/disaccharaides in the mouth

A

by salivary amylase secreted by the salivary glands

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17
Q

how are complex carbs digested into disaccharides in the sm. intestine

A

by pancreatic amylase secreted by the pancreas

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18
Q

how are disaccharides digested into monosaccharides in the sm intestine.

A

by Disaccharidases secreted by brush border

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19
Q

how are triglycerides digested into fatty acid & monoglycerides in the mouth

A

by lingual lipase secreted by the tongue

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20
Q

how are triglycerides digestied into sm. drops in digestive solution in the duodenum

A

by bile secretion by the liver

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21
Q

how are triglycerides digested into fatty acids & monoglycerides in the small intestine

A

by pancreatic lipase secreted by the pancreas

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22
Q

how are nucleic acids digested into nitrogenous bases & sugar in the sm. intestine

A

by nucleases & nucleosides secreted by the pancrease& sm/ intestine

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23
Q

where does absorption of nutrients take place

A

mainly the ileum & the jejunum (across the brush boarder)

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24
Q

How are sugars (monosaccarides) & amino acids transported across brush boarder of sm. intestine

A

1) By cotransport (move molecules into cell even where conc. is more high)
2) By facilitated delusion (b/c some can only move down their gradient)

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25
Q

the products of protein & carbohydrate digestion enter…

A

the capillaries in the lamina propria & then the hepatic portal vein & then the liver

26
Q

How do lipids cross the brush boarder

A

1) Monoglycerides & fatty acids (lipid soluble) diffuse across the brush border w/ no transporter needs
2) The are NOT h20 soluble so they must be coated in proteins &phospholipds to be transported into blood/lymph: called chylomicrons

27
Q

step by step process of fat digestion to being put into blood

A

1) Fatty acids & monoglycerides emulsion by bile
2) Now micelles (bile coated droplets containing fatty acids/ monoglyceride)
3) Fatty acids & monoglycerides diffuse across cell membrane.
4) reassemble into triglycerides, then combine w/ cholesterol, phospholipids & proteins to form chylomicrons
5) chylomicrons leave sm. intestine cell by exocytosis
6) they are to large to go into blood vessels, so they are picked up by lacteals to the cisterna chyli to thoracic duct to veins

28
Q

What do the chylomicrons do once they’re in blood?

A

LIPOPROTEIN LIPASE in endothelium of capillaries breaks down triglycerides
-Fatty acids go to adipose to be stored as triglycerides, muscle to be used as energy & liver to be processed

29
Q

what breaks down triglycerides in capillaries once their in blood

A

lipoprotein lipase

30
Q

what is a micelle

A

bile coated droplet containing fatty acids & monoglycerides) product of emulsification

31
Q

What are lipoproteins

A

proteins made in the liver
they transport lipids to & from the liver & tissues
there is Low density & high density

32
Q

Low Density lipoproteins

A

LOWSY (lots of lipid, less protein)

  • transports lipids from LIVER to TISSUES via:
  • Receptor mediated endocytosis (pulls lipids into cells)
  • Can be deposited in endothelium (Plaque deposited that sits under the endothelium & causes atherosclerosis)
  • increased risk of heart attack & stroke
33
Q

what are high density lipoproteins

A

HEALTHY (less lipid, more protein)

-Transports lipids from cells to liver - can be excreted in bile ( made form cholesterol)

34
Q

what are the LDL & HDL steps in the liver

A

1) Liver removes fatty acids from chylomicrons, adds cholesterol to from LDL
2) LDL enters circulation
3) Receptor mediated endocytosis of LDL
4) Cells use cholesterols to synthesize cell membrane, hormones, etc.
5) Cholesterol not used is picked up by HDL in the blood

35
Q

Explain the carb/starch absorption pathway

A

1) Oral (salivary amylase)
2) sm. intestine (pancreatic amylase)
- it is now disaccharides & trisaccharides
3) Facilitated cotransport diffusion of monosaccharides into brush border
4) facilitated diffusion of monosaccharides into capillaries

36
Q

explain lipid absorption pathway

A

1) Oral (lingual lipase )
2) sm. intestine (emulsified by bile from liver)
- pancreatic lipase
- now monoglycerides & fatty acids
3) diffuse into brush border -reassembled into triglyceride
4) Packaged into chylomicrons
5) Into lacteals by exocytosis

37
Q

Explain the protein absorption pathway

A

1) stomach (pepsin enzyme) = peptides
2) Sm. Intestine (trypsin, chymotrypsin, carboxypeptidase, elastase) all from pancreas
-product = peptides & amino acids
3) Intestinal mucosa secretes peptidases
=amino acids now
4) facilitated diffusion cotransport into mucosa
5) facilitated diffusion cotransport of amino acid into capillary

38
Q

what happens to the absorption of vitamins

A

1) water sol. (B,C) -> facilitated diffusion
- Except b12 must be bound to intrinsic factor
2) Fat sol. (ADEK) diffuse w/ lipids (in chylomicrons)

39
Q

What i s pernicious anemia

A

defect in gene that codes for intrinsic factor. Cannot absorb B12 need for cell division

40
Q

Explain the absorption of ions/electrolytes

A
  • Transporter required (H2O soluble & charged)
  • facilitative diffusion of active transport
  • Na+ with amino acids is cotransported
  • Ca2+ transported is activated by vit. D3 & parathyroid hormone
  • Iron = active transport enhanced by vit C/acids
41
Q

How is water absorbed

A

By osmosis (92% in sm. intestine) (6-7% in lrg intestine)

  • only about 150ml in feces per day
  • no absorption in stomach
42
Q

How is digestion regulated

A

by hormones & Autonomic nervous system (enteric plexuses = neurons in GI tract)

43
Q

what are the 3 phases for digestion regulation

A

1) Cephalic phase
2) Gastric Phase
3) Intestinal phase

44
Q

what happens in the cephalic phase

A

occurs b4 food enters stomach

-sight/smell/taste/thought -> hypothalamus -> parasympathetic system -> increase saliva & gastric juice

45
Q

what happens in the gastric phase

A

activated by the arrival of food/protein in the stomach

1) Chemoreceptors trigger gastrin secretion by the G cells in the gastric gland
2) Stretch receptors trigger parasympathetic vagus nerve
3) both of these increase gastric juice & increase gastric motility

46
Q

What happens in the intestinal phase

A

1) Activated by the arrival of chyme in the duodenum
2) The chemo & stretch receptors cause:
- duodenal endocrine secretion of hormones
- parasympathetic activation -> increases intestinal motility

47
Q

what are the 2 main duodenal endocrine hormones secreted in the intestinal phase

A

1) Secretin

2) cholecytoskinin

48
Q

what does secretin do

A

1) Increases pancreatic sodium bicarbonate secretion
2) increase bile secretion by liver
3) decreases gastric secretion
4) decreases gastric motility

49
Q

what does cholecystokinin do

A

1) Increases pancreatic enzyme secretion
2) increases gallbladder contraction
3) relaxes hepatopancreatic sphincter
4) increases pancreatic sodium bicarbonate secretion
5) decreases gastric secretion
6) decreases gastric motility

50
Q

What is glucose dependent insulinotropic peptide and when is it secreted

A
  • secreted when sugars&fats enter duodenum
  • Stimulate insulin secretion
  • stimulate lipogenesis in adipocytes
51
Q

what is vasoactive intestinal peptide

A

stimulated intestinal glands to increase sodium bicarbonate & H20 secretion
-it dilates the intestinal blood vessels to increase blood flow

52
Q

explain control of defecation

A

-mass movements (twice a day)
-initiated by arrival of food in stomach/intestine (gastrocolic/duodenocolic reflexes)
-under parasympathetic control
-and conscious control of skeletal muscles
Transit time: 24-48hr

53
Q

distesion of the rectum causes…

A

relaxation of internal smooth muscle. sphincter & defecation

54
Q

Where are the satiety centres

A

the hypothalamus
it recieves signals from stretch receptors in GI tract, blood chemoreceptors, hormones, energy storage tissues, the brain (emotions) and gut bacteria

55
Q

explain short term appetitive decrease

A

Stretch receptors, Increased blood glucose, increase insulin, increased blood amino acids & increased Cholecystokinin DECREASE APPETITE

56
Q

explain short term appetite increase

A

Ghrelin (hormone secreted when stomach lining is empty) increases appetite

57
Q

explain long term regulation of appetite

A

Lectin (secreted by adipose)
increased adiopose, increased leptin, = decreased apeitite
-obesity leads to lectin resistance

58
Q

peristalsis in the small intestine begins …

A

when chyme enters the duodenum

59
Q

glucose & sodium are

A

cotrasported together

60
Q

secreted by intestinal gland & by acinar cells

A

sodium bicarbonate

BIO 153 final (Lab Exam + Lecture) (13 decks)

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