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Biochemistry > Revsion Lecture Semester 2 > Flashcards

Revsion Lecture Semester 2 Flashcards

(77 cards)

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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
How is glycogen syn by UDP glucose
Via glycogen synthase rate limiting step
26
What does glycogen synthase do to glucose mole
Add one glucose mol to glycogen at a time forming alpha 1-4 glycosidic bond Can only extend chains not new branches
27
What is the branching enzyme
Transglycosylase introduces alpha 1-6 glycosidic branches to glycogen
28
When does glycogenesis occur
Immediately after meals when blood glucose increased
29
What is the importance of cholesterol
Essential component of mammalian cell membranes as reg fluidity Precursor of 3 imp classes of bio active compounds Imp for metabolism
30
Why is cholesterol imp for metabolism
CVD | Component to gall stones
31
What is cholesterol the precursor of
Bike acids Steroid hormones Vitamin D
32
What kind of solubility does cholesterol have in water
Low
33
How much of circulating cholesterol is in the free form
30%
34
What are cholesterol esters and what is their solubility like in water
Majority esterified to a wide range of long chain fatty acids they are esterified through cholesterol hydroxyl Less soluble in water
35
How are cholesterol esters stored and where
Lipid droplets in ER
36
What is cholesterol incorporated in
Lipoproteins | Present as free cholesterol and cholesterol esters which are located in the core of molecule
37
How does fee cholesterol control its own synthesis
Negative feedback regulator
38
How is the regulation of cholesterol controlled
Mediated by a family of transcription factors (DNA binding) STEROL REGULATORY ELEMENT BINDING PROETINS -SREBS
39
What are SREBS
Regulate syn of enzymes which control prod of cholesterol HMG CoA reductase HMG CoA synthase Also codes for cell surface receptor APOPROTEIN RECEOTOR
40
What does the deletion of hepatic sterols do to SREBS
Increases SREBS and therefore increases cholesterol syn and expression of APOPROTEIN receptors
41
What is the APOPROTEIN receptor recieve
Cholesterol in form of lipoprotein
42
What are some features of endocarp sis
Receptor mediated Specific saturable Movement into cell E.g binding of LDL
43
What are some properties of exocytosis
Secretory Movement out of cell E.g when chylomicrons carrying tags or cholesterol Etc Leave enterocyte and enter lacteals
44
What is the primary function of lipoproteins
Transport vehicles for lipids in lymph and blood
45
What is the structure of a lipoprotein
Core hydrophobic lipids - cholesterol esters and tags Surrounded by shell- polar lipids whic are phospholipids, apoproteins, free cholesterol
46
How are lipoproteins distinguished
By size and density More lipid the lower density The more proetin the higher density
47
Explain some properties of low density lipoproteins
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
Explain some properties of high density lipoproteins
Major lipid - phospholipid Syn by liver snd intestine Circulates blood to collect excess cholesterol
49
What are high density lipoproteins important for
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
What is the only organ capable of metabolising and excreting cholesterol
Liver
51
Where does cholesterol synthesis occur
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
What dos the synthesis of 1 mole of cholesterol require
Source of C atoms - 18 moles of acetyl coA A source of reducing power - 16 moles nADH Significant amount of energy - 36 atp
53
What is mevalonic acid
3 moles of acetyl coA are converted into 6-carbon mevalonic acid
54
What enzymes are used in acetyl coA reactions
Acetoacetyl coA thiolase HMG-coA synthase HMG-coA reductase (rate limit step of chol syn)
55
What is the rate limiting step of chol syn
HMG-coA reductase | Formation mevalonic acid irreversible
56
What is HMGR
HMG-coA reductase
57
Where is HMGR found
Embedded in ER
58
How is HMGR controlled
Feedback inhibition Rate of deg Phosphorylation Gene expression
59
What hormones affect HMGR
Insulin and T3 - increase activity Glugacon and cortisol - inhibit activity
60
What does a high intracellular free cholesterol lead to
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
How much of free cholesterol obtained form diet
15%
62
What do statin drugs do
Inhibit cholesterol syn
63
What does the inhibition of cholesterol synthesis lead to
Leads to increase in LDL receptor expression | Promotes removal of LDL form blood
64
What is the main metabolic product from cholesterol
Bile salts
65
How do bile salts differ
In number and position of hydroxyl groups
66
Where are bile salts syn and sec
Liver
67
How are the four primary bile acids formed
Before secretion | Cholic acid and chenodeoxycholic acid are conjugated though Carboxyl to glycine or taurine
68
Where are bile salts stored
Gall bladder
69
What do bile salts do
Sec and into duodenum act as detergents for emulsifying ingested lipids
70
What does vitamin D do
Play a role in regulation of calcium/phosphorous metabolism
71
How is vitamin D3 synthesised
In the skin by uv light from the sun of 7-dehydrocholesterol
72
What is the active form of Vit D3
Calcitriol | Steroid hormone
73
What are the three organs that convert cholesterol into steroid hormones
Adrenal cortex - corticosteroids Testis- androgens Ovary - estero gens
74
How do steroid hormones act
Binding to specific receptors Zinc fingers next to DNA binding domain of hormone Binging hormone facilitates translocation of activated receptor
75
What is the gene transcription by glucocorticoids
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
What does the transformation of cholesterol to bile acids and steroid hormones include
Hydroxylaction reactions catalysed by cytochrome P450 mono oxygenate
77
Give some examples of primary mono sacs
Glucose fructose and galactose

Biochemistry (13 decks)

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