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HOS Unit 4 > 19 Nutrient Digestion and absorption > Flashcards

19 Nutrient Digestion and absorption Flashcards

1
Q

T-F– only monosaccharides can be absorbed?

A

T

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2
Q

What is branched vegetable starch is called? Unbranched starch?

A

amylopectin

amylose

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3
Q

Amylose has what type of linkages?

A

alpha-1,4-linkages

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4
Q

Branch points in amylopectin consist of what type of linkages?

A

alpha-1,6

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5
Q

What are the 3 basic monosaccharides?

A

glucose, fructose, and galactose

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6
Q

Does glycogen or amylopectin have more alpha-1,6 linkages?

A

Much more in glycogen

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7
Q

What are the 2 phases of digestion of carbohydrates?

A
  1. gut lumen by secreted enzymes

2. along brush border wall by enzymes

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8
Q

Is salivary amylase or pancreatic amylase more important?

A

Pancreatic

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9
Q

What types of bonds to alpha-amylases act upon?

A

alpha-1,4

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10
Q

What type of bonds can alpha-amylases not act upon?

A
  1. Terminal alpha-1,4
  2. alpha-1,6
  3. alpha-1,4 bonds adjacent to 1,6 branches
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11
Q

Starch digestion by amylase results in production of what 3 sugar structures?

A

maltos, maltotriose and alpha-limit dextrins

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12
Q

What are the remnants of branching points and the surrounding alpha 1,4-bonded glucose molecules that cannot be cleaved by amylase?

A

Dextrins

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13
Q

Can glucose be produced by amylase hydrolysis of starch?

A

No

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14
Q

What cleaves alpha-1,4 linkages of maltose, maltotriose, and alpha-limit dextrins to yield glucose?

A

Maltase

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15
Q

What is sucrase-isomaltase dual activities?

A
  1. cleave sucrose into glucose and fructose

2. Isomaltase cleaves alpha-1,6 bonds of a-limit dextrins

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16
Q

What does lactase do?

A

hydrolyze lactose

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17
Q

What is the protein responsible for Na/Glu coupled uptake that is driven by NaK ATPase?

A

SGLT1

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18
Q

Insulin has what effect of which receptor of glucose absorption?

A

Downregulates expression of Glut 2 on the apical membrane

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19
Q

When is Glut 2 upregulated?

A

Increased sugar load [and artificial sweetener as she pointed out]

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20
Q

What fructose protein carrier is found primarily in the jejunum?

A

Glut5-facilitated diffusion

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21
Q

Sugar transport across basolateral membrane occurs via facilitated diffusion by which transport protein?

A

Glut2 [glucose, fuctose, and galactose]

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22
Q

T-F–50% of our protein load comes from endogenous sources?

A

True

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23
Q

What are endogenous sources of protein intake?

A
  • proteins from secretions

- shed epithelial cells

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24
Q

What is the gastric protease?

A

pepsin

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25
Q

How much protein digestion is pepsin responsible for? is it necessary?

A

10-15%

No

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26
Q

What type of enzyme cleaves peptide bonds adjacent to the carboxyl terminus and releases individual AA

A

exopeptidase-carboxypeptidase A and B

27
Q

What type of enzyme cleaves peptide bonds between specific AA sequences and produces oligos with 2-6 AA?

A

endopteptidases- trypsin, chymotrypsin, and elastase

28
Q

What is the division by percentage of pancreatic protease production of short peptide chains versus individual AA?

A

70% and 30%

29
Q

T-F–N-terminal and C-terminal peptidases are made?

A

True

30
Q

There exists brush border peptidases on the membranes of enterocytes, but are there any in enterocyte cystosols?

A

Yes [ endopeptidases and dipeptidases and exopeptidases]

31
Q

What type of peptides are specifically absorbed by secondary active transport via PepT1?

A

Short peptides

[PepT1 symports H and peptide, HNa antiporter pumps H back out. NaK pump sets gradient]

32
Q

T-F—short peptides are better absorbed that individual amino acids into the enterocytes?

A

True

33
Q

What is a neutral AA-Na cotransporter that is driven by Na gradient?

A

System B

34
Q

What transports basic amino acids along with Na?

A

System B 0+

35
Q

Is AA exiting basolateral membrane a sodium dependent dependent process?

A

No

36
Q

What are long chain fatty act esters of glycerol?

A

Triglycerides

37
Q

What is glycerol backbone with a phosphoester bond at 3rd position?

A

phospholipids

38
Q

What 2 lipase’s function well at low pH and initiate lipid digestion?

A

lingual lipase

gastric lipase

39
Q

What does lingual and gastric lipase’s remove from triglycerides?

A

one fatty acid [generates a diglyceride to]

40
Q

What happens to medium and short chain fatty acids?

A

soluble and and enter the aqueous phase and are absorbed by gastric mucosa

41
Q

What pH does collapse and pancreatic lipase function at?

A

neutral

42
Q

What does collapse do?

A

anchor lipase to the lipid micelle and penetrate the coat

43
Q

What positions does pancreatic lipase remove fatty acids from in the triglyceride?

A

position 1 and 3

44
Q

What is lipase function inhibited by?

A

bile acids

45
Q

Phospho lipids are digested by what?

A

phospholipase A2—removes a single fatty acid from the molecule

46
Q

What helps make micelles mallet and thins out the coat to one layer?

A

bile acids

47
Q

What are unilameller micelles which have been maximally digested, containing mostly: fatty acids, monoglycerides, cholesterol and lysophospholipids?

A

mixed micelles

48
Q

How are long chain FA and monoglycerides transported out of the enterocyte?

A

reassembled into triglycerides and packaged into chylomicrons

49
Q

What can pass right through the enterocytes into the blood stream without the need of packaging into chylomicrons?

A

short chain fatty acids, medium chain, and glycerol

50
Q

deficiency in folate leads to? what is the biologically active form of folate?

A

megaloblastic anemia

tetrahydrofolate

51
Q

What does a deficiency in B12 cobalamin result in?

A

megaloblastic anemia

52
Q

What does B12 bind to in the acidic stomach environment?

A

haptocorrin

53
Q

What is produced in the stomach and and binds to B12 after it is in an alkaline environment?

A

intrinsic factor

54
Q

Intrinsic factor is made by what cells?

A

gastric parietal cells

55
Q

Doe proton pump inhibitors or H2 receptor inhibitors block intrinsic factor secretion?

A

Only H2 receptor blockers

56
Q

T-F–B12 without intrinsic factor is absorbed in the terminal ileum?

A

False–they have to be complexed together

57
Q

Where does active absorption of calcium only occur?

A

duodenum

58
Q

what does free Ca in the cytosol immediately bind to after it penetrates apical membrane do to electrochemical gradient? How is it transported from cell? What stimulates all of these steps?

A
  1. calbindin [keeps calcium levels low]
  2. Ca pum and CaNa exchanger
  3. Vitamin D
59
Q

T-F–passive uptake of Ca occurs throughout the small bowel occurs paracellularly?

A

True—does not need vitamin D stimulation

60
Q

Where does active uptake of magnesium occur?

A

in the ileum—passive can take place elsewere

61
Q

Where is non-heme iron absorbed? Is ferrous or ferric more soluble?

A

only in duodenum

ferrous

62
Q

Is heme iron or non-heme iron more easily absorbed?

A

Heme-iron

[binds to brush border proteins or is absorbed—>inside the cell heme oxygenate releases Fe3+ and reduces it to Fe2+]

63
Q

What acid reduces ferric iron to ferrous?

A

ascorbic

64
Q

Tannins found in tea do what with iron?

A

interfere uptake by forming insoluble complexes

HOS Unit 4 (18 decks)

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