Carbohydrates 4

Question 1

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

Answer 1

• Brain
• Nervous system
• RBCs
• Testes
• Embryonic tissues

Question 2

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

Answer 2

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

Question 3

What is gluconeogenesis not

Answer 3

A reverse of glycolysis

Question 4

How many glycolysis reactions are reversible?

Answer 4

7 out of 10

Question 5

What prevents reactions in glycolysis from being reversible?

Answer 5

Large –ve ΔG

Question 6

How does the cell bypass the irreversible reactions?

Answer 6

With enzymes that catalyse a separate set of irreversible reactions

Question 7

How many reactions sidestep the 3 irreversible reactions?

Answer 7

4 bypasses

Question 8

What do the bypass reactions in glycolysis allow?

Answer 8

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

Question 9

Where do the bypass reactions occur?

Answer 9

• A+B =mitochondria

- B+D= cytosol

Question 10

What is usually the end point of gluconeogenesis?

Answer 10

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

Question 11

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

Answer 11

Lumen of ER

Question 12

What does the process of making free Glc require?

Answer 12

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

Question 13

What metabolises most fructose?

Answer 13

Liver

Question 14

Where can fructose and galactose enter glycolysis?

Answer 14

At various points

Question 15

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

Answer 15

• Fructose-1-phosphat aldolase

- Triose kinase

Question 16

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

Answer 16

Glyceraldehyde-3-phosphate

Question 17

How does galactose enter glycolysis?

Answer 17

• 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

Question 18

What are the products of the pentose phosphate pathway?

Answer 18

• NADPH

- Pentoses

Question 19

What are pentoses?

Answer 19

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

Question 20

What are the 2 parts of the pentose phosphate pathway?

Answer 20

• Oxidative, irreversible part

- Reversible, non-oxidative part

Question 21

What takes place in the oxidative part off the PPP?

Answer 21

• Generation of NADPH

- Converts G-6-P to a pentose phosphate

Question 22

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

Answer 22

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

Question 23

When does the reversible part take place?

Answer 23

When lots of NADPH is needed

Question 24

When does the irreversible part take place?

Answer 24

When lots of nucleotides are required

Question 25

What links catabolic and anabolic reactions in the PPP?

Answer 25

nadph

Question 26

When is NAD used?

Answer 26

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

Question 27

When is NADP used?

Answer 27

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

Question 28

What stops NAD and NADP being used interchangeably?

Answer 28

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

Question 29

What happens when people get drunk?

Answer 29

Reduced gluconeogenesis

Question 30

What happens in the liver when excess alcohol is consumed?

Answer 30

• 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.

Question 31

What does the inhibition of gluconeogenesis lead to?

Answer 31

• Lactiacidaemic (increased [blood lactate])

- Hypoglycaemia (decreased[blood Glc])

Question 32

What is black water fever?

Answer 32

G-6-P dehydrogenase deficiency

Question 33

What does black water fever cause?

Answer 33

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

Question 34

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

Answer 34

They are unable to suffer the extra trauma of infection

Question 35

What is the result of overexpression of PEPCK?

Answer 35

Lots of PEP in muscle from lactate