Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

MEH > Carbs 2 > Flashcards

Carbs 2 Flashcards

1
Q

Why does glycolysis need to be regulated

A
  • control flux in response to demand
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the most important regulatory enzyme in glycolysis

A

phosphofructokinase - 1

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What are the two ways phosphofructokinase-1 can be regulated

A

allosteric
hormonal

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What molecules allosterically inhibit phosphofructokinase-1

A

high ATP
high citrate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What molecules allosterically stimulate phosphofructokinase-1

A

high AMP
high fructose-2,6-bisphosphate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are high energy signals

A

indicate cell has enough energy
ATP
NADH
FADH2
NADPH

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are low energy signals

A

indicate the cell is using and requires energy
AMP/ADP
NAD
FAD
NADP

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are two other regulatory enzymes in glycolysis

A

hexokinase (not glucokinase in liver)
pyruvate kinase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

how is hexokinase regulated in glycolysis

A

end product inhibition
G6P

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

how is pyruvate kinase regulated

A

hormonal
high insulin : low glucagon

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Why is lactate produced

A
  • step 6 of glycolysis needs constant NAD source
  • done when insufficient oxygen
  • done in cells with no mitochondria e.g. RBC
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What enzyme produces lactate

A

lactate dehydrogenase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is the equation for pyruvate to lactate

A

2 pyruvate + 2 NADH + 2H+ –> 2 lactate + 2NAD+

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

How is lactate used

A
  • by heart to turn back to pyruvate for energy
  • by liver and kidney for pyruvate for energy or gluconeogenesis
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What are normal plasma levels of lactate

A

less than 1 nm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What lactate levels suggest hyperlactaemia

A

2-5 nm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What plasma lactic levels suggest lactic acidosis

A

above 5nm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what is the normal production of lactate in a day without exercise

A

40-50 g

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What can strenuous exercise increase plasma lactate levels by a min

A

10g

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

what is galactose require for

A

synthesis of glycolipids and glycoproteins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Where is galactose found in diet

A

lactose

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Where is galactose metabolised

A

liver

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What enzyme is used in the first reaction of glycolysis

A

galactokinase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What is the reaction of galactokinase

A

galactose + ATP –> galactose-1-p + ADP + Pi

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What is the second enzyme in galactose metabolism

A

galactose-1-p uridyl transferase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What does the enzyme galactose-1-p uridyl transferase do

A

transfers a UDP group from UDP-glucose to galactose-1-p to make glucose-1-p (which enters glycolysis) and UDP galactose

25
Q

How is UDP glucose regenerate and with what enzyme

A

UDP-galactose-4-epimerase converts UDP-galactose to UDP-glucose by changing orientation of OH group

26
Q

Why is the UDP-galactose-4-epimerase enzyme important for pregnancy

A

allows production of lactose from glucose via UDP- glucose

27
Q

Where does fructose come from in the diet

A

sucrose

28
Q

where is fructose metabolised

A

liver

29
Q

What is the first enzymes required in fructose metabolism

A

fructokinase

30
Q

What is the reaction for fructokinase

A

fructose + ATP –> fructose-1-p + ADP + Pi

31
Q

What is the second enzyme in fructose metabolism

A

adolase

32
Q

What is the reaction for adolase

A

fructose-1-p cleaved into glyceraldehyde and DHAP

33
Q

What enzyme converts glyceraldehyde into glyceraldehyde-3-p

A

triose kinase
requires ATP

34
Q

What enzyme converts DHAP into glyceraldehyde-3-p

A

TPI

35
Q

What are the two conditions involving fructose

A
  • essential fructosuria
  • fructose intolerance
36
Q

What is essential fructosuria

A

fructokinase missing
fructose in urine

37
Q

What enzyme is missing in fructose intolerance

A

adolase

38
Q

what is the result of fructose intolerance

A

fructose-1-p accumulates in liver
cells depleted of Pi
liver damage

39
Q

how is fructose intolerance managed

A

remove all fructose and sucrose from diet

40
Q

What is galactosemia

A

unable to digest galactose

41
Q

What are the two causes of galactosemia

A
  • galactokinase deficiency
  • transferase deficiency (most damage)
  • epimerase deficiency
42
Q

What are the symptoms of galactosemia

A
  • hepatomegaly and cirrhosis
  • renal failure
  • vomiting
  • seizure and brain damage
  • cataract
  • hypoglycemia
43
Q

What happens when galactose accumulates

A

reduced to galacticol

44
Q

What enzyme converts galactose to galacticol

A

aldose reductase

45
Q

What does aldose reductase require to reduce galactose to galacticol

A

NADPH

46
Q

Why does a lack of GALT enzyme cause a lot of damage

A

accumulation of galactose-1-p causes liver, kidney and brain damage and depletes cells of Pi

47
Q

Explain how galactosemia can cause cataracts

A
  • build up of galactose converted to galacticol by aldose reductase
  • this uses up excessive NADPH
  • compromises defences against oxidative damage
  • ox damage causes cross linkages of S-S disulphide bonds in lens causing crystallisation
48
Q

How does galactosemia relate to glaucoma

A

accumulation of galactose and galacticol in lens increases intra-ocular pressure

49
Q

What is the treatment for galactosemia

A

remove lactose from diet

50
Q

What are the defences against oxidative damage

A
  • glutathione ( uses NADPH for electron donor)
  • catalase (NADPH structural component)
  • thioredoxin system (NADPH electron donor)
  • thiltransferase system (uses glutathione as cofactor)
51
Q

How can galactose still be produced on galactose free diet for lactation

A

using glucose and UDP galactose which can be made from UDP glucose to make lactose through lactose synthase

52
Q

What is the importance of the pentose phosphate pathway

A
  • major source of NADPH
  • generates pentose sugars for nucleotides
53
Q

What is the starting point for pentose phosphate pathway

A

some of glucose-6-phosphate from glycolysis

54
Q

What is the first enzyme in the pentose phosphate pathway

A

glucose-6-p dehydrogenase

55
Q

What is the reaction for the enzyme glucose-6-p dehydrogenase

A

glucose-6-p + NADP –> 6-phosphogluconolacetone + NADPH

56
Q

What happens to any unused 5C sugars from pentose phosphate pathway

A

converts any unused sugars 5C sugars to intermediates of glycolysis

57
Q

What is the regulatory enzyme in the pentose phosphate pathway

A

glucose-6-p dehydrogenase

58
Q

How is the enzyme glucose-6-p dehydrogenase regulated

A

NADP : NADPH ratio.
NADPH inhibiting
NADP activating

59
Q

Where is the glucose-6-p dehydrogenase enzyme found

A

X chromosome

60
Q

What does a deficiency in glucose-6-p dehydrogenase cause

A

low NADPH
less glutathione
this causes less protection from oxidative damage

61
Q

Why is NADPH require for glutathione synthesis

A

NADPH require to reduce oxidised form of glutathione back to active reduced form

62
Q

Why are RBC particularly affected by glucose-6-p dehydrogenase deficiency

A

pentose phosphate pathway is RBC only source of NADPH
- Hb cross linked by disulphide bonds from ox damage
- forms insoluble aggregates called Heinz bodies
- haemolysis

MEH (12 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions