Carbohydrates 4 Flashcards

1
Q

Which cells rely on glucose as their main source of energy?

A

Brain cells, RBC’s, nervous system, testis, embryonic tissue

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2
Q

How many out of the 10 glycolysis reactions are irreversible?

A

3

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3
Q

What are the 4 reactions called that side step the three irreversible reactions of glycolysis

A

Bypass reactions, allow for the independant control of pathways and to stop them canceling each other out

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4
Q

Where do the first two bypass reactions occur?

A

Mitochondria

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5
Q

What are the first two bypass reactions?

A

Pyruvate - Oxaloacetate
Oxaloacetate - PEP
Pyruvate can be derived from lactate, Lactate +(NAD)+ (lactate dehydrogenase) = pyruvate + NADH

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6
Q

What is the pathway of molecules in the first bypass reactions if pyruvate has and hasn’t been derived from Lactate?

A

Lactate : Lactate, Pyruvate, Oxaloacetate, PEP
No Lactate: Pyruvate, Oxaloacetate, Malate, Oxaloacetate, PEP

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7
Q

What is the control point for gluconeogenesis?

A

The third bypass reaction for, it is irreversible under cell conditions

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8
Q

What enzyme catalyses the hydrolysis of f-1,6-bisP to Fructose-6-Phosphate?

A

Fructose 1,6-bisphosphatase

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9
Q

What is the fourth bypass reaction?

A

Dephosphorylation of G-6-P to glucose, the final stage in gluconeogenesis. Glucose 6-phosphatase is the catalyst

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10
Q

Why is G-6-P normally the end point for gluconeogenesis?

A

Allows the cells to ‘trap’ the glucose

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11
Q

Where does the final step of gluconeogeneogenesis to make free glucose take place?

A

Lumen of the ER

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12
Q

Where is most fructose metabolised?

A

Liver

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13
Q

How many ATP are used for each molecule of Frutose converted into Glyceraldehyde -3- phosphate?

A

1 or 2§

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14
Q

What is the first molecule of ATP used for?

A

Converts fructose to fructose - 1 - Phosphate (using fructokinase enzyme)

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15
Q

What is the reaction pathway for fructose-1-phosphate?

A

Reacts with fructose-1-phosphate aldolase froming glyceraldehyde and dihydroxyacetone phosphate. Glyceraldehyde reacts with triose kinase and another molecule of ATP to form Glyceraldehyde 3-Phosphate

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16
Q

How is galactose converted to glucose 1-phosphate?

A

Through use of sugar-nucleotide derivative UDP-galactose

17
Q

What is the function of the pentose phosphate pathway?

A

Produces NADPH for all organisms, produces pentose sugars, metabolises the small amount of pentoses in the diet (usually come from digestion of nucleotides)

18
Q

What is the oxidative irreversible part of the pentose phosphate pathway?

A

Generates NADPH
Converts G-6-P to pentose phosphate
Required when lots of NADPH is needed

19
Q

What is the reversible non-oxidative part?

A

Interconverts G-6-P and pentose phosphate to produce lots of different 3,4,5,6,7 carbon sugars
When lots of nucleotides are required

20
Q

What is the function of NADPH?

A

Links anabolic and catabolic pathways

21
Q

What type of reaction is NAD+ involved in?

A

Metabolism of dietary sugars in the redox reactions of glycolysis and the citric acid cycle

22
Q

What type of reactions is NADP+ involved in?

A

Anabolism to convert simple precursors into things like fatty acids
Also acts as an antioxidant

23
Q

What stops NADP+ being used in metabolism?

A

Enzyme specificity

24
Q

What is the effect of being drunk on gluconeogenesis?

A

Reduced gluconeogenesis

25
Q

How can being drunk be linked to lacticacidaemia?

A

Reduced level of NAD+
Less lactate converted into pyruvate

26
Q

How can being drunk be linked to hypoglycemia?

A

Decreased blood glucose concentration since gluconeogenesis is inhibited