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Biochemistry > Revsion Lecture Semester 2 > Flashcards

Revsion Lecture Semester 2 Flashcards

1
Q

How are primary monosacs abs

A

Via carrier mediated mechanisms which demo stereo specificity, saturation kinetics and can be specifically inhibited

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2
Q

What is SGLT1 and what dos it do

A

Sodium- glucose linked transporter mem bound proetin binds glucose and sodium at diff sites - symporters driven by conc grad of these two
also transport galactose

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3
Q

What is an example of secondary active trans

A

SGLT1 trans galactose

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4
Q

What does GLUT2 do

A

Uni porter transports monosacs into circulation facilitated

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5
Q

Where is SGLT1 found

A

Luminal mem of enterocyte

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6
Q

How is the sodium gradient maintained

A

Maintained by sodium potassium ATPase which keeps intracellular sodium conc low

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7
Q

What is the driving force of sodium transport

A

Sodium conc grad set up by ATPase also brings glucose

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8
Q

How is facilitated sugar transport mediated

A

By members of the glut transporter family

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9
Q

What is glycogenesis

A

Synthesis of glycogen from glucose

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10
Q

What is Glycogenolysis

A

Breakdown of glycogen to form glucose

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11
Q

What is gluconeogensis

A

Syn of glucose in body from non- carb precursors such as amino acids, lactic acid and glycerol

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12
Q

What is glycogen

A

Main storage form of glucose in liver and muscle cells

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13
Q

What is liver glycogen used for

A

Broken down between meals and released to maintain the brain and blood levels for red blood cells

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14
Q

What is muscle glycogen used for

A

Not available for maintenance of blood glucose levels

Provides energy via glycolysis and the TCA cycle during bursts of physical activity

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15
Q

What are the bonds of glycogen

A

Alpha 1-4 glycosidic links - between glucose molecules

Alpha 1-6 glycosidic bonds - introduce branches

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16
Q

What enzyme is used to convert glucose to glucose 6 Phosphate

A

Hexokinase

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17
Q

What enzyme converts glucose 6 Phosohate to glucose 1 phosphate

A

Phosphoglucomutase

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18
Q

What is glucose 6 phosphate used in

A

Glycolysis

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19
Q

What is glucose - 1 - phosphate used for

A

Glycogen synthesis

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20
Q

What does glycogen synthesis require

A

Primer which contains at least 4 glucose residues

Made up by convalently attached to glycogenin

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21
Q

What is activated glycogenin

A

Uses UDP-glucose - activated glucose

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22
Q

What enzyme is used in UDP glucose formed

A

UDP glucose pyrophosphorylase

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23
Q

What is the reactions of UDP glucose formation

A

UTP + glucose 1 phosphate –> UDP glucose + pyrophosphate

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24
Q

Is UDP glucose reversible

A

Yes

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25
Q

How is glycogen syn by UDP glucose

A

Via glycogen synthase rate limiting step

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26
Q

What does glycogen synthase do to glucose mole

A

Add one glucose mol to glycogen at a time forming alpha 1-4 glycosidic bond
Can only extend chains not new branches

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27
Q

What is the branching enzyme

A

Transglycosylase introduces alpha 1-6 glycosidic branches to glycogen

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28
Q

When does glycogenesis occur

A

Immediately after meals when blood glucose increased

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29
Q

What is the importance of cholesterol

A

Essential component of mammalian cell membranes as reg fluidity

Precursor of 3 imp classes of bio active compounds

Imp for metabolism

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30
Q

Why is cholesterol imp for metabolism

A

CVD

Component to gall stones

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31
Q

What is cholesterol the precursor of

A

Bike acids
Steroid hormones
Vitamin D

32
Q

What kind of solubility does cholesterol have in water

A

Low

33
Q

How much of circulating cholesterol is in the free form

A

30%

34
Q

What are cholesterol esters and what is their solubility like in water

A

Majority esterified to a wide range of long chain fatty acids they are esterified through cholesterol hydroxyl

Less soluble in water

35
Q

How are cholesterol esters stored and where

A

Lipid droplets in ER

36
Q

What is cholesterol incorporated in

A

Lipoproteins

Present as free cholesterol and cholesterol esters which are located in the core of molecule

37
Q

How does fee cholesterol control its own synthesis

A

Negative feedback regulator

38
Q

How is the regulation of cholesterol controlled

A

Mediated by a family of transcription factors (DNA binding) STEROL REGULATORY ELEMENT BINDING PROETINS -SREBS

39
Q

What are SREBS

A

Regulate syn of enzymes which control prod of cholesterol
HMG CoA reductase
HMG CoA synthase

Also codes for cell surface receptor
APOPROTEIN RECEOTOR

40
Q

What does the deletion of hepatic sterols do to SREBS

A

Increases SREBS and therefore increases cholesterol syn and expression of APOPROTEIN receptors

41
Q

What is the APOPROTEIN receptor recieve

A

Cholesterol in form of lipoprotein

42
Q

What are some features of endocarp sis

A

Receptor mediated
Specific saturable
Movement into cell
E.g binding of LDL

43
Q

What are some properties of exocytosis

A

Secretory
Movement out of cell
E.g when chylomicrons carrying tags or cholesterol Etc
Leave enterocyte and enter lacteals

44
Q

What is the primary function of lipoproteins

A

Transport vehicles for lipids in lymph and blood

45
Q

What is the structure of a lipoprotein

A

Core hydrophobic lipids - cholesterol esters and tags

Surrounded by shell- polar lipids whic are phospholipids, apoproteins, free cholesterol

46
Q

How are lipoproteins distinguished

A

By size and density
More lipid the lower density
The more proetin the higher density

47
Q

Explain some properties of low density lipoproteins

A

Major lipid - cholesterol
Delivers cholesterol to cells for cell mem and hormone prod
LDL receptor is mem bound proetin which binds LDL causing is to be taken up by cell and dismantled

48
Q

Explain some properties of high density lipoproteins

A

Major lipid - phospholipid
Syn by liver snd intestine
Circulates blood to collect excess cholesterol

49
Q

What are high density lipoproteins important for

A

Reverse cholesterol transport

Salvages excess cholesterol form cells
Chol then esterified with fatty acids
Trans back to liver
Excreted as bile salts via biliary system or faeces

50
Q

What is the only organ capable of metabolising and excreting cholesterol

A

Liver

51
Q

Where does cholesterol synthesis occur

A

In the cytoplasm but some enzymes bound to ER mem

Main site syn is liver but also lesser contributions form intestine, adrenal Cortex, gonads

52
Q

What dos the synthesis of 1 mole of cholesterol require

A

Source of C atoms
- 18 moles of acetyl coA

A source of reducing power
- 16 moles nADH

Significant amount of energy
- 36 atp

53
Q

What is mevalonic acid

A

3 moles of acetyl coA are converted into 6-carbon mevalonic acid

54
Q

What enzymes are used in acetyl coA reactions

A

Acetoacetyl coA thiolase
HMG-coA synthase
HMG-coA reductase (rate limit step of chol syn)

55
Q

What is the rate limiting step of chol syn

A

HMG-coA reductase

Formation mevalonic acid irreversible

56
Q

What is HMGR

A

HMG-coA reductase

57
Q

Where is HMGR found

A

Embedded in ER

58
Q

How is HMGR controlled

A

Feedback inhibition
Rate of deg
Phosphorylation
Gene expression

59
Q

What hormones affect HMGR

A

Insulin and T3 - increase activity

Glugacon and cortisol - inhibit activity

60
Q

What does a high intracellular free cholesterol lead to

A

Limit syn by HMG-coA reductase activity

Limit uptake by down reg of LDL receptors

Increase in efflux

Increased rate of conversion to bile salts

61
Q

How much of free cholesterol obtained form diet

A

15%

62
Q

What do statin drugs do

A

Inhibit cholesterol syn

63
Q

What does the inhibition of cholesterol synthesis lead to

A

Leads to increase in LDL receptor expression

Promotes removal of LDL form blood

64
Q

What is the main metabolic product from cholesterol

A

Bile salts

65
Q

How do bile salts differ

A

In number and position of hydroxyl groups

66
Q

Where are bile salts syn and sec

A

Liver

67
Q

How are the four primary bile acids formed

A

Before secretion

Cholic acid and chenodeoxycholic acid are conjugated though Carboxyl to glycine or taurine

68
Q

Where are bile salts stored

A

Gall bladder

69
Q

What do bile salts do

A

Sec and into duodenum act as detergents for emulsifying ingested lipids

70
Q

What does vitamin D do

A

Play a role in regulation of calcium/phosphorous metabolism

71
Q

How is vitamin D3 synthesised

A

In the skin by uv light from the sun of 7-dehydrocholesterol

72
Q

What is the active form of Vit D3

A

Calcitriol

Steroid hormone

73
Q

What are the three organs that convert cholesterol into steroid hormones

A

Adrenal cortex - corticosteroids
Testis- androgens
Ovary - estero gens

74
Q

How do steroid hormones act

A

Binding to specific receptors
Zinc fingers next to DNA binding domain of hormone
Binging hormone facilitates translocation of activated receptor

75
Q

What is the gene transcription by glucocorticoids

A

Steroid binds to receptor in cytoplasm
receptors dimerises
Exposes a nuclear localisation signal
Enters nucleus
Binds DNA at specific response element which is a hormone response element
Activate promoter and switch transcription on or off

76
Q

What does the transformation of cholesterol to bile acids and steroid hormones include

A

Hydroxylaction reactions catalysed by cytochrome P450 mono oxygenate

77
Q

Give some examples of primary mono sacs

A

Glucose fructose and galactose

Biochemistry (13 decks)

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