Brainscape's Knowledge GenomeTM

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


See full index

Semester 1 - MCBG > 4. Carbohydrates 2 > Flashcards

4. Carbohydrates 2 Flashcards

1
Q

What are the two important intermediates in glycolysis?

A
  1. Glycerol phosphate

2. 2,3-bisphosphoglycerate

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

How is glycerol phosphate produced?

A

After the glucose has been phosphorylated in glycolysis, fructose 1,6-bisphosphate is produced which is converted to DHAP instead of being split into two 3 carbon molecules. The DHAP is converted to glycerol phosphate by the enzyme glycerol 3-phosphate dehydrogenase which oxidises NADH

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

What is glycerol phosphate used for?

A

Important to triglyceride and phospholipid biosynthesis

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

Where is glycerol phosphate produced?

A

Produced from dihydroxyacetone phosphate (DHAP) in
adipose tissue and liver.
Therefore, lipid synthesis in liver requires glycolysis

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

How is 2,3-bisphosphoglycerate produced?

A

Produced from 1,3-bisphosphoglycerate in RBC in the presence of Bisphosphoglycerate mutase enzyme.

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

What is the function of 2,3-bisphosphoglycerate (2,3-BPG)?

A

Regulator of haemoglobin
O2 affinity (promotes
release)

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

Why do red blood cells normally and muscle cells when under strenuous activity respire anaerobically?

A

• Total NAD+ + NADH in cell is constant,
therefore, glycolysis would stop when all
NAD+ is converted to NADH
• Normally, NAD+ is regenerated from NADH in
stage 4 of metabolism
BUT
• RBC have no stage 3 or 4 of metabolism
• Stage 4 needs O2 - supply of O2 to muscles and
gut often reduced

• Therefore, need to regenerate NAD+ by some other route - anaerobic respiration

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

How is lactate produced?

A

Pyruvate reduced by gaining H+ from NADH to produce NAD and lactate in the presence of Lactate Dehydrogenase

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

Why is pyruvate converted to lactate?

A

To regenerate NAD to be used n glycolysis to produce ATP

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Where is lactate produced and where is it released into?

A

produced by RBC and skeletal muscle (skin, brain, GI). Released into blood

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

Where is lactate normally metabolised(converted back into pyruvate)?

A

normally metabolised by liver and heart

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

What happens to the lactate in liver and kidney?

A

Converted to pyruvate by losing H+ to NAD. Then used to produce energy or converted to glucose by gluconeogenesis which is released into the blood and picked up by tissues which convert it to pyruvate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is hyperlactemia?

A

Increase in plasma lactate but below renal threshold and no change in blood ph.

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

What is lactic acidosis?

A

When increase in lactate goes a love Rena threshold and causes blood pH to be lowered. Lactic acid is then found in the urine

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

Describe fructose metabolism

A
  • Fructose phosphorylates into fructose-1P by the enzyme fructokinase. This requires ATP hydrolysis.
  • the fructose 1-P then splits into glyceraldehyde and DHAP by the enzyme Aldolase.
  • The glyceraldehyde is converted into glyceraldehyde-3P by the enzyme triose kinase (which requires ATP hydrolysis)
  • DHAP is also converted to gyceraldehyde-3P by enzyme TPI.
  • The glyceraldehyde-3P is then used in glycolysis.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Where is fructose metabolised?

A

Liver

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

What is essential fructosuria?

A

When fructokinase is missing - fructose cannot be metabolised.

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

How is essential fructosuria identified?

A

Fructose in urine

no clinical signs - not too damaging

19
Q

What is fructose intolerance?

A

Aldolase missing - Fructose-1-P accumulates in liver

- leads to liver damage

20
Q

What is the treatment for fructose intolerance?

A

remove fructose from diet

21
Q

Describe Galactose metabolism

A
  1. lactose is broken down into glucose and galactose
  2. Galactose is phosphorylated to galactose- 1P by galactokinase. This requires ATP hydrolysis to ADP
  3. The galactose-1P is converted to glucose-1P by galactose-1-P uridyl transferase.
  4. This requires UDP-glucose as the glucose from UDP-glucose is transferred to galactose-1-P and the galactose from galactose-1-P is transferred to the UDP-glucose. The products are glucose-1-P and UDP-galactose.
  5. The glucose-1P is then converted to glucose-6P which is used in glycolysis.
  6. The UDP-galactose is then converted back to UDP-glucose by UDP-galactose epimerise. The UDP-glucose can then be reused in converting galactose-1-P to glucose-1-P
22
Q

Where is galactose metabolised?

A

Liver

23
Q

What is Galactosaemia?

A

Deficiency in any of the 3:
Galactokinase
Uridyl transferase
UDP-galactose epimerase

Therefore Unable to utilise galactose

24
Q

What would happen if the galactosaemia was due to Galactokinase deficiency?

A

galactose accumulates

25
Q

What would happen if the galactosaemia was due to Transferase deficiency?

A

galactose and galactose-1-P accumulate

26
Q

What is the problem with accumulation of galactose?

A

Galactose enters other pathways

27
Q

What other pathway would the accumulated galactose be used in?

A

The galactose is converted to galactitol in the presence of the enzyme aldose reductase. The enzyme requires the oxidation of NADPH to NADP.

28
Q

What disease does the conversion of galactose to galactitol cause and why?

A

Causes cataracts because:
• it uses up NADPH which would’ve been used to Maintain free -SH (cysteine) groups on certain proteins. This prevents oxidation to - S - S - (disulphide bonds)
• depletion of the NADPH Prevents maintenance of free sulphydryl groups on proteins
• Inappropriate disulphide bond formation
• Loss of structural and functional integrity of some proteins that
depend on free -SH groups
• E.g. lens of eye

29
Q

What organs do the accumulation of galactose -1-p effect?

A

affects liver, kidney, brain

30
Q

What is the treatment for galactosaemia?

A

no lactose in diet

31
Q

What is galactosaemia?

A

rare genetic metabolic disorder that affects an individual’s ability to metabolize the sugar galactose properly

32
Q

What happens if fructose-1-P builds up?

A

Leads to liver damage

33
Q

What are the symptoms of galactosaemia?

A
  • hepatomegaly + cirrhosis
  • renal failure
  • vomiting
  • seizure + brain damage
  • cataracts
  • hypoglycaemia
34
Q

Where does the pentose phosphate pathway feed out from?

A

Glucose-6-P

35
Q

Where does the pentose phosphate pathway occur?

A

In the cytosol

36
Q

Describe the pentose phosphate pathway

A

Two stage pathway - cytoplasmic
:
(a) Oxidative decarboxylation
• the glucose-6-P made in is converted to 5C sugar phosphates in the presence of the enzyme glucose-6-P dehydrogenase
• this involves the reduction of NADP to NADPH and the release of carbon dioxide

(b) Rearrangement to glycolytic intermediates (multistep)

3 C5-sugars ————> 2 Fructose-6-P + 1 Glyceraldehyde-3-P

•the Fructose-6-P and Glyceraldehyde-3-P is fed back into glycolysis

37
Q

What are 3 things that need to remembered about the pentose phosphate pathway?

A
  1. No ATP production
  2. Loss of CO2, therefore irreversible
  3. Controlled by NADP+/NADPH ratio at G6P dehydrogenase
38
Q

Why is the pentose pathway very important?

A

Because it produces NADPH and 5C sugar phosphates

which is needed in the body

39
Q

What is NADPH required for?

A

• Fatty acid biosynthesis
• Steroid biosynthesis
• GSH regeneration
• Maintain free -SH (cysteine) groups on certain proteins
Prevent oxidation to - S - S - (disulphide bonds)

41
Q

Where in the body is there high activity of the pentose phosphate pathway due to it producing NADPH?

A

liver and adipose tissue - lipid synthesis

42
Q

Where in the body is there high activity of the pentose phosphate pathway due to it producing 5C sugar phosphates?

A

dividing tissues e.g. bone marrow

43
Q

What happens in Glucose-6-phosphate dehydrogenase deficiency?

A

• Pentose phosphate pathway has an important role in providing NADPH to maintain SH group of proteins in a
reduced state
• Structural integrity and, hence, functional activity of some proteins depends on -SH groups
• G6PDH deficiency is a very common
inherited defect
• e.g. in RBC, reduced NADPH —> disulphide bonds formed —> aggregated proteins,
Heinz bodies —> haemolysis
• Lens of eye

44
Q

What is the 5C sugar phosphate needed for?

A 
Needed for nucleic acid synthesis:
• Nucelotides 
• DNA 
• RNA 
• Coenzymes

Semester 1 - MCBG (18 decks)

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