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Science for Medicine > Carbohydrates 4 > Flashcards

Carbohydrates 4 Flashcards

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1
Q

What tissues rely completely on glucose as their main source of energy?

A
  • Brain
  • Nervous system
  • RBCs
  • Testes
  • Embryonic tissues
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2
Q

What happens if we do a lot of exercise or fast and we need more energy?

A

Glucose can be generated from other non-carbohydrate molecules which usually occurs in the liver in response to hormonal controls.

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3
Q

What is gluconeogenesis not

A

A reverse of glycolysis

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4
Q

How many glycolysis reactions are reversible?

A

7 out of 10

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5
Q

What prevents reactions in glycolysis from being reversible?

A

Large –ve ΔG

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6
Q

How does the cell bypass the irreversible reactions?

A

With enzymes that catalyse a separate set of irreversible reactions

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7
Q

How many reactions sidestep the 3 irreversible reactions?

A

4 bypasses

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8
Q

What do the bypass reactions in glycolysis allow?

A

Independent control of the glycolysis and gluconeogenesis pathways and ensures they do not cancel each other out

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9
Q

Where do the bypass reactions occur?

A
  • A+B =mitochondria

- B+D= cytosol

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10
Q

What is usually the end point of gluconeogenesis?

A

F-6-P being converted to G-6-P

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11
Q

Where does the final step to make free Glc take place?

A

Lumen of ER

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12
Q

What does the process of making free Glc require?

A

Requires G-6-P to be shuttles into the lumen and the Glc to be shuttled back out to the cytoplasm

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13
Q

What metabolises most fructose?

A

Liver

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14
Q

Where can fructose and galactose enter glycolysis?

A

At various points

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15
Q

What are the enzymes in the fructose -1- phosphate pathway?

A
  • Fructose-1-phosphat aldolase

- Triose kinase

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16
Q

What is the end product of the fructose-1-phosphate pathway?

A

Glyceraldehyde-3-phosphate

17
Q

How does galactose enter glycolysis?

A
  • Galactose is converted to G-1-P through a sugar-nucleotide derivative UDP-galactose
  • UDP-glucose and UDP-galactose amounts remain unchanged as they are recycled, therefore the net product is G-1-P
18
Q

What are the products of the pentose phosphate pathway?

A
  • NADPH

- Pentoses

19
Q

What are pentoses?

A

5C sugars that are precursors of ATP, RNA and DNA

20
Q

What are the 2 parts of the pentose phosphate pathway?

A
  • Oxidative, irreversible part

- Reversible, non-oxidative part

21
Q

What takes place in the oxidative part off the PPP?

A
  • Generation of NADPH

- Converts G-6-P to a pentose phosphate

22
Q

What takes place during the non-oxidative part of the PPP?

A

-Interconverts G-6-P and pentose phosphate to form lots of different 3,4,5,6 and 7C sugars

23
Q

When does the reversible part take place?

A

When lots of NADPH is needed

24
Q

When does the irreversible part take place?

A

When lots of nucleotides are required

25
Q

What links catabolic and anabolic reactions in the PPP?

A

nadph

26
Q

When is NAD used?

A

In metabolism of dietary sugars in the redox reactions of glycolysis and the CAC

27
Q

When is NADP used?

A
  • In anabolism to convert simple precursors into things like fatty acids
  • Also acts as an antioxidant
28
Q

What stops NAD and NADP being used interchangeably?

A

Enzymes involved in pathways having differing specificities for the two electron carriers

29
Q

What happens when people get drunk?

A

Reduced gluconeogenesis

30
Q

What happens in the liver when excess alcohol is consumed?

A
  • Ethanol is converted to acetyl CoA through intermediates producing NADH.
  • Acetyl CoA can then be stored as fat or proceed through the CAC and terminal respiration.
31
Q

What does the inhibition of gluconeogenesis lead to?

A
  • Lactiacidaemic (increased [blood lactate])

- Hypoglycaemia (decreased[blood Glc])

32
Q

What is black water fever?

A

G-6-P dehydrogenase deficiency

33
Q

What does black water fever cause?

A

Low RBC NADPH levels which allows damaging free radicals and H2O2 to build up which damages the membranes of the RBC

34
Q

What is the result of damages RBC in black water fever?

A

They are unable to suffer the extra trauma of infection

35
Q

What is the result of overexpression of PEPCK?

A

Lots of PEP in muscle from lactate

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