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Biochemistry > B22 Digestion And Absorption Of Proteins > Flashcards

B22 Digestion And Absorption Of Proteins Flashcards

1
Q

What kind of enzymes cleave internal peptide bonds

A

Endopeptidases

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2
Q

What enzymes cleave ends of protiens

A

Exopeptidases

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3
Q

What does HCl in the stomach do to proteins

A

Denature the,

Unfolding makes the protein more accessible to digest

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4
Q

What doe chief cells secrete

A

Pepsinogen

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5
Q

What si pepsinogen

A

Inactive precursor of pepsin

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6
Q

What can activated pepsin do

A

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

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7
Q

What does pepsinogen to pepsin stimulate the secretion of

A

Cck

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8
Q

What kind of protein structure is pepsinogen

A

Enzyme tertiary structure

Prosegment mask active site

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9
Q

What stimulates the secretion of sce retain

A

Acidity of stomach entering the duo

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10
Q

What kind of hormone is secretin

A

Peptide

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11
Q

What does secretin stillage

A

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

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12
Q

What does cck stimulate

A

Release of main digestive enzymes by the pancreas

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13
Q

What converts trypsinogen to trypsin

A

Duodenal enteropeptidases

Trios in can then auto activate

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14
Q

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

A

Activates them

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15
Q

How does the trypsin inhibitor inhibit trypsin

A

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

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16
Q

What are some pancreatic enzymes and their active forms

A

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

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17
Q

Where is enteropeptidases produced and bound

A

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

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18
Q

What does enteropeptidases do

A

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

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19
Q

Where does trypsin hydrolyse polypeptides on the chain

A

On the Carboxyl side of arginine and lysine residues

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20
Q

What does chymotrypsin bind

A

Aromatic amino acids as hydrophobic pocket

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21
Q

What does elastase interact with

A

Active site partially blocked by side chains of valine and threonine

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22
Q

What kind of amino acids can move via passive diffusion

A

Limited to hydrophobic amino acids such as tryptophan

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23
Q

How most amino amino acid transport

A

Against conc grad which is via active mechanism

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24
Q

Where are amino acid carrier systems

A

Exist in brush border of enterocyte basolateral border

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25
Q

How are di tri peptide transport into the enterocyte

A

By secondary active transport

26
Q

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

A

By hydrogen ion dependant co porter

27
Q

What do the basolateral facilitated diffusion not depend on

A

Sodium

28
Q

What are some fat soluble vitamins

A

A
K
E
D

29
Q

What are some water soluble vitamins

A

B1- B9

C

30
Q

What is the chemical property of water and fat soluble vitamins

A

Water sol - hydrophilic

Fat sol - hydrophobic

31
Q

How are water soluble vitamins excreted

A

In the urine

32
Q

How are fat soluble,e vitamins excreted

A

Not stored in body

33
Q

How are fat soluble vitamins carried

A

In Micelle and absorbed by the enterocytes

34
Q

How are most water soluble vitamins absorbed

A

By simple passive diffusion

35
Q

What are Cobalamins

A

4 metabolically imp forms of B12

36
Q

What are Cobalamins released form their protein by

A

Pepsin and stomach acid

37
Q

What are Cobalamins bound to

A

Glycoproteins haptocorrin which is sec by stomach

38
Q

What does free Cobalamins bind to

A

Intrinsic factor

39
Q

Heat does free B12 bind to

A

Trans cobalamin II

40
Q

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

A

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

41
Q

How do u syn vit D3

A

Skin by Uv radiation of 7 - dehydrocholesterol

42
Q

What happens to vitamin D3 after syn in skin

A

Carried in serum by vitamin binding protein

Hydroxyl acted in liver and then kidney

43
Q

What si the final product of vit d3 syn

A

Calcitriol active form

1,25-OH2D3

44
Q

What does calcitriol do

A

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

45
Q

What kind of hormone is calcitriol

A

Steroid hormone

46
Q

What si vitamin D3 deficiency

A

Rickets

Osteomalacia

47
Q

Where is calcium absorbed predominately

A

In the proximal small intestine

48
Q

What are the two cellular calcium transport processes

A

Trans cellular abs stimulated by calcitriol

Para cellular

49
Q

What are the steps for moving calcium across the enterocyte

A

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

50
Q

The syn of calbindin and trpv6 are upregukated by

A

The active form of vit d

51
Q

What is iron especially important for

A

Transfer of molecular oxygen present in Hb

52
Q

What component does iron part of in Hb and myoglobin

A

Heme

53
Q

Where else is iron found

A

Cytochrome a,b and c

54
Q

What form is dietary iron

A

Ferric form Fe3+

55
Q

Where is ferric form of iron reduced

A

In GI tract

56
Q

What reduces the ferrous form of iron

A

Ascorbate and ferrireductase in brush border of enterocyte

57
Q

How is fr2+ transported into the cells

A

By a divalent metak transporter

58
Q

What happens to an excess of iron

A

Incomrp into a protien ferritin

59
Q

How does iron be in crop into heme

A

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

60
Q

What enzymes hydrolyse proteins

A

Peptidases

Biochemistry (13 decks)

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