Carbohydrates 4 Flashcards Preview

01. Year 1: Science for Medicine > Carbohydrates 4 > Flashcards

Flashcards in Carbohydrates 4 Deck (49)
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1
Q

What are some tissues that completely rely on glycolysis for their energy?

A

Brain

Nervous system

RBCs

Testes

Embryonic tissue

2
Q

What happens if we have no more carboyhydrates but need more glucose?

A

It can be generated from non-carbohydrate molecules in the liver

3
Q

Why is gluconeogensis not the direct reverse of glycolysis?

A

Due to the 3 irreversible steps (steps 1, 3 and 10)

4
Q

What is gluconeogensis?

A

The generation of glucose from non-carbohydrate substances

5
Q

How many reactions are used to bypass the irreversible steps of glycolysis?

A

4

6
Q

What does the bypassing of the irreversible steps of glycolysis allow?

A

Gluconeogenesis and glycolysis to be regulated seperately

7
Q

What irreversible reaction does A and B of gluconeogenesis deal with?

A

PEP to glycolysis

8
Q

What is step A?

A

The conversion of pyruvate to oxaloacetate

9
Q

What is step B?

A

The conversion of oxaloacetate to PEP

10
Q

What do reactions A and B look like?

A
11
Q

What step of glycolysis does reaction C bypass?

A

F-6-P to F-1,6-bisP

12
Q

What does reaction C look like?

A
13
Q

Why is reaction C not the direct reverse of F-6-P to F-1,6-bisP?

A

It would require the transfer of a phosphyl group which is energetically unfavourable

14
Q

What step of glycolysis does reaction D bypass?

A

Glucose to G-6-P

15
Q

What does reaction D look like?

A
16
Q

Where is G-6-P converted to glucose?

A

In the lumen of the endoplasmic reticulum

17
Q

What does the conversion of G-6-P to glucose in the ER require?

A

G-6-P to be shuttled into the ER and glucose to be shuttled out, an inorganic phosphate is also shuttled out

18
Q

What does this pump controlling the conversion of G-6-P to glucose look like?

A
19
Q

How many points can galactose and fructose enter glycolysis?

A

Several

20
Q

What is fructose converted into to enter glycolysis?

A

Glucose-6-phosphate

21
Q

What is fructose converted into in adipose tissue to enter glycolysis?

A

Fructose-6-phosphate

22
Q

What is fructose in the liver converted into to enter glycolysis?

A

Glyceraldehyde-3-P (GAP) or dihudroxyacetone-P (DHAP)

23
Q

Where is most fructose metabolised?

A

Liver

24
Q

What pathway does fuctose use to become DHAP or GAP in the liver?

A

Fructose-1-phosphate

25
Q

How much ATP does the conversion of fructose to DHAP or GAP use?

A

1 or 2

26
Q

What does the conversion of fructose to DHAP or GAP look like?

A
27
Q

What is galactose converted to G-1-P through?

A

UDP-galactose

28
Q

What are the steps of galactose becoming glucose-6-phosphate to enter glycolysis?

A
  1. Galactose comes in and is phosphorylated
  2. UDP glucose transfers UDP molecule to galactose
  3. Captures electrons by producing NADH
29
Q

What does the pentose phosphate pathway produce?

A

NADPH and pentoses (5C) sugars

30
Q

Where and what is NADPH used for?

A

Liver (fatty acid synthesis)

Mammary gland (fatty acid synthesis)

Adrenal cortex (steroid synthesis)

RBC (antioxidant)

31
Q

What are pentoses precursers for?

A

ATP

RNA

DNA

32
Q

What are the two stages of the pentose phosphate pathway?

A

Oxidation (irreversible)

Non oxidation (reversible)

33
Q

Is the oxidation stage of the pentose phosphate pathway reversible?

A

No

34
Q

Is the non oxidation stage of the pentose phospate pathway reversible?

A

Yes

35
Q

What happens during the oxidative stage of the pentose phosphate pathway?

A

Generates NADPH

Converts G-6-P to a pentose phosphate

36
Q

What happens during the non oxidative stage of the pentose phosphate pathway?

A

Forms lots of different 3, 4, 5, 6 and 7 carbon sugars

37
Q

What does the pentose phosphate pathway look like?

A
38
Q

What does NADPH link?

A

Anabolic and catabolic pathways

39
Q

Are NAD+ and NADP+ the same?

A

They are both electron carriers but they are not the same

40
Q

What are NAD+ and NADP+?

A

Electron carriers

41
Q

What is NAD+ used for?

A

Metabolism of sugars in glycolysis and the citric acid cycle

42
Q

What is NADP+ used for?

A

Anabolism to make things like fatty acid

43
Q

What does breaking down ethanol require?

A

NAD+

44
Q

What does the breakdown of ethanol look like?

A
45
Q

Why does breaking down lots of ethanol inhibit gluconeogenesis?

A

Low NAD+ to facilitate the reaction as most has bean used to breakdown ethanol

46
Q
A
47
Q

What does a low level of NAD+ lead to?

A

Lacticacidaemia (increase[blood lactate])

Hypoglycaemia (decreased [blood glucose])

48
Q

What is black water fever?

A

A difficiency of G-6-P dehydrogenase

49
Q

What does black water fever cause?

A

Low RBC NADPH levels

Build up of free radicals and H2O2 which damages cells