19 Nutrient Digestion and absorption

Question 1

T-F– only monosaccharides can be absorbed?

Answer 1

T

Question 2

What is branched vegetable starch is called? Unbranched starch?

Answer 2

amylopectin

amylose

Question 3

Amylose has what type of linkages?

Answer 3

alpha-1,4-linkages

Question 4

Branch points in amylopectin consist of what type of linkages?

Answer 4

alpha-1,6

Question 5

What are the 3 basic monosaccharides?

Answer 5

glucose, fructose, and galactose

Question 6

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

Answer 6

Much more in glycogen

Question 7

What are the 2 phases of digestion of carbohydrates?

Answer 7

1. gut lumen by secreted enzymes

2. along brush border wall by enzymes

Question 8

Is salivary amylase or pancreatic amylase more important?

Answer 8

Pancreatic

Question 9

What types of bonds to alpha-amylases act upon?

Answer 9

alpha-1,4

Question 10

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

Answer 10

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

Question 11

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

Answer 11

maltos, maltotriose and alpha-limit dextrins

Question 12

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

Answer 12

Dextrins

Question 13

Can glucose be produced by amylase hydrolysis of starch?

Answer 13

No

Question 14

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

Answer 14

Maltase

Question 15

What is sucrase-isomaltase dual activities?

Answer 15

1. cleave sucrose into glucose and fructose

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

Question 16

What does lactase do?

Answer 16

hydrolyze lactose

Question 17

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

Answer 17

SGLT1

Question 18

Insulin has what effect of which receptor of glucose absorption?

Answer 18

Downregulates expression of Glut 2 on the apical membrane

Question 19

When is Glut 2 upregulated?

Answer 19

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

Question 20

What fructose protein carrier is found primarily in the jejunum?

Answer 20

Glut5-facilitated diffusion

Question 21

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

Answer 21

Glut2 [glucose, fuctose, and galactose]

Question 22

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

Answer 22

True

Question 23

What are endogenous sources of protein intake?

Answer 23

• proteins from secretions

- shed epithelial cells

Question 24

What is the gastric protease?

Answer 24

pepsin

Question 25

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

Answer 25

10-15% | No

Question 26

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

Answer 26

exopeptidase-carboxypeptidase A and B

Question 27

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

Answer 27

endopteptidases- trypsin, chymotrypsin, and elastase

Question 28

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

Answer 28

70% and 30%

Question 29

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

Answer 29

True

Question 30

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

Answer 30

Yes [ endopeptidases and dipeptidases and exopeptidases]

Question 31

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

Answer 31

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

Question 32

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

Answer 32

True

Question 33

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

Answer 33

System B

Question 34

What transports basic amino acids along with Na?

Answer 34

System B 0+

Question 35

Is AA exiting basolateral membrane a sodium dependent dependent process?

Answer 35

No

Question 36

What are long chain fatty act esters of glycerol?

Answer 36

Triglycerides

Question 37

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

Answer 37

phospholipids

Question 38

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

Answer 38

lingual lipase | gastric lipase

Question 39

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

Answer 39

one fatty acid [generates a diglyceride to]

Question 40

What happens to medium and short chain fatty acids?

Answer 40

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

Question 41

What pH does collapse and pancreatic lipase function at?

Answer 41

neutral

Question 42

What does collapse do?

Answer 42

anchor lipase to the lipid micelle and penetrate the coat

Question 43

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

Answer 43

position 1 and 3

Question 44

What is lipase function inhibited by?

Answer 44

bile acids

Question 45

Phospho lipids are digested by what?

Answer 45

phospholipase A2---removes a single fatty acid from the molecule

Question 46

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

Answer 46

bile acids

Question 47

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

Answer 47

mixed micelles

Question 48

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

Answer 48

reassembled into triglycerides and packaged into chylomicrons

Question 49

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

Answer 49

short chain fatty acids, medium chain, and glycerol

Question 50

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

Answer 50

megaloblastic anemia | tetrahydrofolate

Question 51

What does a deficiency in B12 cobalamin result in?

Answer 51

megaloblastic anemia

Question 52

What does B12 bind to in the acidic stomach environment?

Answer 52

haptocorrin

Question 53

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

Answer 53

intrinsic factor

Question 54

Intrinsic factor is made by what cells?

Answer 54

gastric parietal cells

Question 55

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

Answer 55

Only H2 receptor blockers

Question 56

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

Answer 56

False--they have to be complexed together

Question 57

Where does active absorption of calcium only occur?

Answer 57

duodenum

Question 58

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?

Answer 58

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

Question 59

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

Answer 59

True---does not need vitamin D stimulation

Question 60

Where does active uptake of magnesium occur?

Answer 60

in the ileum---passive can take place elsewere

Question 61

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

Answer 61

only in duodenum | ferrous

Question 62

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

Answer 62

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

Question 63

What acid reduces ferric iron to ferrous?

Answer 63

ascorbic

Question 64

Tannins found in tea do what with iron?

Answer 64

interfere uptake by forming insoluble complexes