B22 Digestion And Absorption Of Proteins

Question 1

What kind of enzymes cleave internal peptide bonds

Answer 1

Endopeptidases

Question 2

What enzymes cleave ends of protiens

Answer 2

Exopeptidases

Question 3

What does HCl in the stomach do to proteins

Answer 3

Denature the,

Unfolding makes the protein more accessible to digest

Question 4

What doe chief cells secrete

Answer 4

Pepsinogen

Question 5

What si pepsinogen

Answer 5

Inactive precursor of pepsin

Question 6

What can activated pepsin do

Answer 6

Auto catalyse the conversion of further mo,ecules of pepsinogen to pepsin

Question 7

What does pepsinogen to pepsin stimulate the secretion of

Answer 7

Cck

Question 8

What kind of protein structure is pepsinogen

Answer 8

Enzyme tertiary structure

Prosegment mask active site

Question 9

What stimulates the secretion of sce retain

Answer 9

Acidity of stomach entering the duo

Question 10

What kind of hormone is secretin

Answer 10

Peptide

Question 11

What does secretin stillage

Answer 11

The secretion of bicarbonate rich pancreatic fluid to neutralise and dilute acid in duo

Question 12

What does cck stimulate

Answer 12

Release of main digestive enzymes by the pancreas

Question 13

What converts trypsinogen to trypsin

Answer 13

Duodenal enteropeptidases

Trios in can then auto activate

Question 14

When trypsin is activated what can it do for the other zymogens

Answer 14

Activates them

Question 15

How does the trypsin inhibitor inhibit trypsin

Answer 15

Lysine 15 in the inhibitor penetrates into the active site of enzyme and forms a salt bridge with aspartate in the active site

Question 16

What are some pancreatic enzymes and their active forms

Answer 16

Chymotrypsinogen –> chymotrypsin
Trypsinogen –> trypsin
Pro elastase –> elastase
ProPhospholipase A2 –> phospholipase A2

Question 17

Where is enteropeptidases produced and bound

Answer 17

Produced in the duodenum and bound to the brush border of the enterocytes

Question 18

What does enteropeptidases do

Answer 18

Initaties the activation of pancreatic zymogens by activating trypsin which then activates other zymogens

Question 19

Where does trypsin hydrolyse polypeptides on the chain

Answer 19

On the Carboxyl side of arginine and lysine residues

Question 20

What does chymotrypsin bind

Answer 20

Aromatic amino acids as hydrophobic pocket

Question 21

What does elastase interact with

Answer 21

Active site partially blocked by side chains of valine and threonine

Question 22

What kind of amino acids can move via passive diffusion

Answer 22

Limited to hydrophobic amino acids such as tryptophan

Question 23

How most amino amino acid transport

Answer 23

Against conc grad which is via active mechanism

Question 24

Where are amino acid carrier systems

Answer 24

Exist in brush border of enterocyte basolateral border

Question 25

How are di tri peptide transport into the enterocyte

Answer 25

By secondary active transport

Question 26

How are the small si tri peptides transported across the brush border

Answer 26

By hydrogen ion dependant co porter

Question 27

What do the basolateral facilitated diffusion not depend on

Answer 27

Sodium

Question 28

What are some fat soluble vitamins

Answer 28

A K E D

Question 29

What are some water soluble vitamins

Answer 29

B1- B9 | C

Question 30

What is the chemical property of water and fat soluble vitamins

Answer 30

Water sol - hydrophilic | Fat sol - hydrophobic

Question 31

How are water soluble vitamins excreted

Answer 31

In the urine

Question 32

How are fat soluble,e vitamins excreted

Answer 32

Not stored in body

Question 33

How are fat soluble vitamins carried

Answer 33

In Micelle and absorbed by the enterocytes

Question 34

How are most water soluble vitamins absorbed

Answer 34

By simple passive diffusion

Question 35

What are Cobalamins

Answer 35

4 metabolically imp forms of B12

Question 36

What are Cobalamins released form their protein by

Answer 36

Pepsin and stomach acid

Question 37

What are Cobalamins bound to

Answer 37

Glycoproteins haptocorrin which is sec by stomach

Question 38

What does free Cobalamins bind to

Answer 38

Intrinsic factor

Question 39

Heat does free B12 bind to

Answer 39

Trans cobalamin II

Question 40

What does the B12 and trans cobalamin II do when in a complex

Answer 40

Leaves the cell Enters the portal vein Taken up by liver by receptor mediated endocytosis

Question 41

How do u syn vit D3

Answer 41

Skin by Uv radiation of 7 - dehydrocholesterol

Question 42

What happens to vitamin D3 after syn in skin

Answer 42

Carried in serum by vitamin binding protein | Hydroxyl acted in liver and then kidney

Question 43

What si the final product of vit d3 syn

Answer 43

Calcitriol active form | 1,25-OH2D3

Question 44

What does calcitriol do

Answer 44

Circulates the blood to control calciu metabolism and homeostasis in various tissue

Question 45

What kind of hormone is calcitriol

Answer 45

Steroid hormone

Question 46

What si vitamin D3 deficiency

Answer 46

Rickets | Osteomalacia

Question 47

Where is calcium absorbed predominately

Answer 47

In the proximal small intestine

Question 48

What are the two cellular calcium transport processes

Answer 48

Trans cellular abs stimulated by calcitriol | Para cellular

Question 49

What are the steps for moving calcium across the enterocyte

Answer 49

Entry via one of 2 calcium channels Intracellular diffusion aided by transport molecule calbindin Extrusion from the cell mediated mainly by calcium ATPase on the basolateral border

Question 50

The syn of calbindin and trpv6 are upregukated by

Answer 50

The active form of vit d

Question 51

What is iron especially important for

Answer 51

Transfer of molecular oxygen present in Hb

Question 52

What component does iron part of in Hb and myoglobin

Answer 52

Heme

Question 53

Where else is iron found

Answer 53

Cytochrome a,b and c

Question 54

What form is dietary iron

Answer 54

Ferric form Fe3+

Question 55

Where is ferric form of iron reduced

Answer 55

In GI tract

Question 56

What reduces the ferrous form of iron

Answer 56

Ascorbate and ferrireductase in brush border of enterocyte

Question 57

How is fr2+ transported into the cells

Answer 57

By a divalent metak transporter

Question 58

What happens to an excess of iron

Answer 58

Incomrp into a protien ferritin

Question 59

How does iron be in crop into heme

Answer 59

Fe2+ ferrioxidase turns to Fe3+ which is then bound to transferrin in the plasma then take up by bone marrow rescued again and incorp to heme

Question 60

What enzymes hydrolyse proteins

Answer 60

Peptidases