lecture 28 - glucose as a fuel molecule

Question 1

glucose is oxidised where

Answer 1

glycolysis in the cytoplasm

Question 2

what is glucose essential for

Answer 2

fuel for red blood cells
- as they do not have mitochondria - dont have other pathways

Question 3

why is glucose the preferred fuel for the brain

Answer 3

high energy requirement

• glucose easily crosses the blood brain barrier
• a high fatty acid metabolism is dangerous

Question 4

why is glucose the favoured fuel in the eye

Answer 4

because blood vessels (brining oxygen) and mitochondria would refract light in the optical path to retina

= uses glycolysis

Question 5

why do white muscles tend to use glucose as fuel but red uses fats

Answer 5

white muscle = short term muscle, used in sprinting etc

works under anaerobic conditions = oxygen low so uses glycolysis

Question 6

what is glycolysis

Answer 6

the splitting of glucose

• conversion of one molecule of glucose (6 carbon) to two molecules of pyruvate (3 carbon)

Question 7

how is energy conserved in glycolysis

Answer 7

ATP and NADH

Question 8

what is the energy investment phase of glycolysis

Answer 8

activation of glucose = getting the molecule in a form so energy can be captured

requires energy input (2 ATP)

• splitting (6C to 3C) the molecule occurs at the end of the investment phase

Question 9

what is the energy pay off phase of glycolsys

Answer 9

• making ATP profit

after conversion, both 3C molecules processed the in the same way

Question 10

how many ATP are produced in the energy pay off phase of glycolysis

Answer 10

4 ATP

Question 11

how many NADH are produced in the energy pay off phase of glycolysis

Answer 11

2 NADH

Question 12

what is the net profit of ATP in glycolysis

Answer 12

2 ATP

Question 13

what does the reaction from glucose to glucose-6-phosphate involve in glycolysis

Answer 13

couples two reactions to make the reaction spontaneous

Question 14

what happens in the reaction from glucose-6-phosphate to fructose-6-phosphate

Answer 14

rearrangement

Question 15

happens in the reaction from fructose-6-phosphate to fructose-1,6-biphosphate in glycolysis

Answer 15

2nd activation of glucose; ATP hydrolysis

Question 16

what is substrate phosphorylation

Answer 16

the direct use of energy from a substate molecule to drive the synthesis of ATP (or equivalent)

Question 17

does the addition of a phosphate require ATP

Answer 17

no

Question 18

what does cleaving a phosphate do in terms of energy

Answer 18

releases energy

Question 19

what is the overall reaction of glycolysis

Answer 19

glucose + 2NAD+ + 2ADP + 2Pi > 2 pyruvate + 2NADH + 2H+

Question 20

what is aerobic oxidation

Answer 20

oxygen available = occurs in the mitochondrial matrix

• oxidative decarboxylation

Question 21

what is the oxidative decarboxylation reaction that occurs in aerobic oxidation

Answer 21

CO2 released (3C to 2C)

pyruvate is oxidised energy captured in NADH and used to add Coenzyme A to two carbon chain

Question 22

what is anaerobic glycolysis

Answer 22

low oxygen

• red blood cells, muscles in anaerobic conditions

Question 23

what happens in anaerobic glycolysis

Answer 23

lactate dehydrogenase oxidises NADH to NAD+ to convert pyruvate to lactate

• energy captured in NADH is lost
• lactate causes muscle fatigue

Question 24

why does the lactate dehydrogenase reaction occur and what occurs in aerobic oxidation

Answer 24

• low concentration of co enzymes in cells
• during aerobic oxidation coenzymes are oxidised (regenerated) in oxidative phosphorylation

Question 25

how does lactate formation allow for the regeneration of NAD+

Answer 25

• lactate dehydrogenase oxidises NAD - so that glycolysis can continue