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GI > GI biochemistry > Flashcards

GI biochemistry Flashcards

1
Q

gluconeogenesis

A

formation of glucose from precursors (AA, lactate, glycerol)

lactate- SM, anaerobic
AA-muscle, proteinolysis
Glycerol- TAG, lipolysis

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2
Q

where is glycogen found

A

liver, muscle

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3
Q

function of liver glycogen

A

broken down during meals to maintain BGL

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4
Q

function of muscle glycogen

A

cannot be broken down to main BGL

Broken down by glycolysis and TCA to provide energy in physical activity

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5
Q

Sources of blood glucose

A

Dietary, Gluconeogenesis, glycogenesis

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6
Q

Structure of glycogen

A

polymer of glucose, a1-4 glycosidic bonds in chains

a1-6 glycosidic branching

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7
Q

Can one glucose start a new Glycogen?

A

No
Glucose must add to an existing glycogen chain
need glycogen primer containing 4 glucose attached to glycogenin

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8
Q

What must attached to glucose for it to add to glycogen chain

A

UDP

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9
Q

Four enzymes involved in glycogen synthesis

A

Hexokinase (phosphorylates glucose)
Phosphoglucomutase (changes position of phosphate)
UDP glucose pyrophosphorylase (binds UDP)
glycogen synthase (UDP-glucose onto glycogen)

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10
Q

Function of glycogen synthase and its limitations

A

adds UDP glucose to glycogen

can only add one at a time, can’t introduce branching, can’t start a new molecule

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11
Q

What enzyme can start a1-6 glycosidic chains

A

transglycosylase (every 10 residues)

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12
Q

Enzyme that catalyses glycogenolysis

A

glycogen phosphorylase

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13
Q

Equation for glycogenolysis and what happens to products

A

glucose + Pi –> G-1-P + [glucose]n-1

G1P-> G6P

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14
Q

Glycogenolysis in liver vs skeletal muscle

A

in liver, the G6P can be dephosphorylated to glucose - bloodstream

SM- G6P cannot be dephosphorylated

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15
Q

what enzyme causes G1P to turn into G6P in glycogenolysis

A

phosphoglucomutase

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16
Q

Precursors, energy source and location of gluconeogenesis

A

Lactate, AA, Glycerol
FA oxidation
mostly liver cells, some kidney

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17
Q

reversible reaction enzymes of glycolysis

A

hexokinase
phosphofructokinase
pyruvate kinase

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18
Q

four liver enzymes required for gluconeogenesis

A

Glucose -6-phosphostase
Fructose-1,6-phosphotase
PEP carboxykinase
Pyruvate carboxylase

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19
Q

what is the Cori Cycle

A

when lactate is the precursor of gluconeogenesis

lactate carried to the liver, liver converts lactate to glucose and releases glucose

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20
Q

what does glucagon signal

A

• Glucagon signals fasted state

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21
Q

what does insulin signal

A

Insulin signals the fed state

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22
Q

components of triglycerides

A

1 glycerol, 3FAs

23
Q

T/F most triglycerides have long chains and have rings

A

T- most have long FA chains

F- most are aliphatic (no rings)

24
Q

normal configuration of double bonds in FA

A

cis-kink

25
Q

which FA are solid and which are liquid @RT

A

up to 8= liquid

>8 solid

26
Q

effect of double bonds on Melting point of TAG

A

double bonds reduce MP

27
Q

Main products of FA digestion

A

glycerol, FA, monoglycerides

28
Q

what happens to short and medium chain FA

A

Enter portal circulation via stomach

29
Q

what happens to long chain FA and monoglycerides

A

combine to from Triglycerides

30
Q

where do chylomicrons go to once formed

A

lymph-blood stream- muscle and tissue

31
Q

what happens to chylomicrons at muscle and tissue

A

cleaved by lipoprotein lipase

32
Q

what must happen to FA before they can provide energy

A

Must be oxidated to acyl CoA in the cytoplasm
Requires 2 ATP
Further oxidation occurs in mitochondrial matrix (requires carrier)

33
Q

2 additional enzymes required for beta oxidation

A

enoyl - CoA Isomerase

2,4 Dienoyl CoA reductase

34
Q

what happens in carnitine shuttle

A

acyl-CoA moves into mitochondrial matrix via conversion to CoA

35
Q

Where does Beta oxidation occur

A

Mitochondrial matrix

36
Q

products of beta oxidation

A

1FADH2
1 acetyl CoA
1NADH, H+
1 fatty acyl-CoA

37
Q

P/O ratio

A

No of phosphate added onto ADP to create ATP divided by no of oxygen atoms consumed by oxidative phosphorylation to make water

38
Q

where are ketone bodies formed and what from

A

liver mitochondria

from acetyl CoA from Beta-oxidation

39
Q

what are ketone bodies important for

A

renal cortex and heart muscle

40
Q

Ketosis in Diabetes and starvation

how can ketosis be detected

A

acetyl CoA is converted to ketones which are acidic and lead to severe acidosis impairing CNS

smell of acetone on breath

41
Q

Major site of AA degradation

A

Liver

42
Q

potential problem with breakdown of AA

A

produces NH3 and NH4 (toxic at high levels)

43
Q

where is urea formed

A

liver

excreted by kidneys

44
Q

Steps in the synthesis of urea

A

AA is converted to glutamic acid by transamination
Glutamic acid to NH4 by deamination
NH4 and aspartic acid make urea

45
Q

where does transamination occur

where does deamination occur

A

all tissues

liver

46
Q

Degradation of carbon skeleton

A

carbon skeletons converted to glucose or go to TCA cycle

47
Q

Ketogenic AA

A

Degraded to acetyl CoA or acetoacetyl CoA

Can make ketones or FA

48
Q

glycogenic AA

A

Degraded to pyruvate or TCA cycle intermediates

can be converted to glucose

49
Q

if the yield of Beta oxidation is C18 how many cycles was this

A

8

18/2=9, 9-1=8

50
Q

what is the FA precursor

A

malonyl CoA

51
Q

What is FA synthesis and where does it occur

A

lipogenesis

Brain, kidneys, mammary glands, liver, kidneys

52
Q

what happens when excess carbs are taken in

A

converted to FA and TAG in liver

transported in plasma bound to albumin to adipose tissue via VLDL for storage

53
Q

T/F Lipogenesis is an oxidative process

A

False

reductive-electrons required

GI (7 decks)

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