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Flashcards in Carbohydrates 4 Deck (49):
1

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

Brain

Nervous system

RBCs

Testes

Embryonic tissue

2

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

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

3

Why is gluconeogensis not the direct reverse of glycolysis?

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

4

What is gluconeogensis?

The generation of glucose from non-carbohydrate substances

5

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

4

6

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

Gluconeogenesis and glycolysis to be regulated seperately

7

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

PEP to glycolysis

8

What is step A?

The conversion of pyruvate to oxaloacetate

9

What is step B?

The conversion of oxaloacetate to PEP

10

What do reactions A and B look like?

11

What step of glycolysis does reaction C bypass?

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

12

What does reaction C look like?

13

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

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

14

What step of glycolysis does reaction D bypass?

Glucose to G-6-P

15

What does reaction D look like?

16

Where is G-6-P converted to glucose?

In the lumen of the endoplasmic reticulum

17

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

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

18

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

19

How many points can galactose and fructose enter glycolysis?

Several

20

What is fructose converted into to enter glycolysis?

Glucose-6-phosphate

21

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

Fructose-6-phosphate

22

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

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

23

Where is most fructose metabolised?

Liver

24

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

Fructose-1-phosphate

25

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

1 or 2

26

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

27

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

UDP-galactose

28

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

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

29

What does the pentose phosphate pathway produce?

NADPH and pentoses (5C) sugars

30

Where and what is NADPH used for?

Liver (fatty acid synthesis)

Mammary gland (fatty acid synthesis)

Adrenal cortex (steroid synthesis)

RBC (antioxidant)

31

What are pentoses precursers for?

ATP

RNA

DNA

32

What are the two stages of the pentose phosphate pathway?

Oxidation (irreversible)

Non oxidation (reversible)

33

Is the oxidation stage of the pentose phosphate pathway reversible?

No

34

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

Yes

35

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

Generates NADPH

Converts G-6-P to a pentose phosphate

36

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

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

37

What does the pentose phosphate pathway look like?

38

What does NADPH link?

Anabolic and catabolic pathways

39

Are NAD+ and NADP+ the same?

They are both electron carriers but they are not the same

40

What are NAD+ and NADP+?

Electron carriers

41

What is NAD+ used for?

Metabolism of sugars in glycolysis and the citric acid cycle

42

What is NADP+ used for?

Anabolism to make things like fatty acid

43

What does breaking down ethanol require?

NAD+

44

What does the breakdown of ethanol look like?

45

Why does breaking down lots of ethanol inhibit gluconeogenesis?

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

46

47

What does a low level of NAD+ lead to?

Lacticacidaemia (increase[blood lactate])

Hypoglycaemia (decreased [blood glucose])

48

What is black water fever?

A difficiency of G-6-P dehydrogenase

49

What does black water fever cause?

Low RBC NADPH levels

Build up of free radicals and H2O2 which damages cells