Carbohydrate metabolism

Question 1

how many carbs does body need?

Answer 1

55%

Question 2

what happens when you have fructose?

Answer 2

hexokinase can turn fructose into F6P in the muscle cells; in the liver, fructo-kinase adds phosphate on 1st carbon of fructose and makes F1P which then has to go through other modifications

Question 3

galactose?

Answer 3

galactose can enter glycolysis via conversion of galactose to G1P through UDP- galactose4-epimerase

Question 4

sugar being added to glycogen always adds to

Answer 4

non-reducing end

Question 5

debranching enzymes

Answer 5

debranches glycogen for use in glycolysis

Question 6

phosphoglucomutase

Answer 6

transfers phosphate on G1P to G6P for use in glycolysis

Question 7

steps in glycolysis

Answer 7

G–> G6P (hexokinase)- phosphorylation (energy investment)
G6P–> F6P (phosphoglucose isomerase)
F6P–> F1,6BisP (phosphofructokinase)-phosphorylation (energy investment)
Fructose is cleaved (aldolase)
2 molecules of glyceraldehyde-3-P (triose phosphate isomerase)
Makes 1,3BPG (glyceraldehyde-3-phosphate dehydrogenase) and results in NADH (oxidation and phosphorylation)
1,3BPG–> 3PG (phosphoglycerate kinase)
results in 1 ATP
3PG–> 2PG (phosphoglycerate mutase- isomerization)
2-PG–> Phosphoenolpyruvate (enolase- dehydration)
–> Pyruvate (pyruvate kinase) and get ATP

Question 8

basic glycolysis steps

Answer 8

energy investment to make Fru1,6BP from glucose
cleavage to get 2 same molecules- 1,3BPG and make 2 NADH
Produce 2 ATP, isomerize some more, produce 2 more ATP, then create pyruvate

Question 9

Use of Mg+ in glycolysis

Answer 9

Mg-ATP- ATP has a lot of negative charge and the positive charge in Mg+ neutralizes and helps in active site

Question 10

how is pyruvate from glycolysis used

Answer 10

enters into mitochondria and used in TCA cycle

Question 11

how is NADH used from glycolysis?

Answer 11

can enter mitochondria and be used in TCA cycle via Malata aspartate shuttle or glycerophosphate shuttle

Question 12

NADH in malate-aspartate shuttle

Answer 12

protons transfer to oxaloacetate and turns into malate and can enter matrix of mitochondria

Question 13

NADH is glycerophosphate shuttle

Answer 13

transfer protons to FADH2 for use in ETC

Question 14

why is NAD+ necessary

Answer 14

used in ETC; if no NAD+ or no O2, entire mechanism can shut down

Question 15

alternative methods of NAD+ regeneration

Answer 15

via lactate dehydrogenase; pyruvate–> lactic acid and oxidizes NADH to NAD

Question 16

NAD+ regeneration in yeast

Answer 16

via alcohol dehydrogenase producing ethanol; ONLY IN YEAST

Question 17

how is glycolysis regulated?

Answer 17

different enzymes catalyze forward (glycolysis) and reverse (gluconeogenesis) reactions

Question 18

essentially irreversible steps in glycolysis

Answer 18

• hexokinase (G–> G6P)
• PFK (F6P–> F16BP)
• PK (phosphoenolpyruvate–> pyruvate)

Question 19

role of ATP in metabolism

Answer 19

inputting ATP energy can insure that both opposing pathways are favorable; allosteric effectors and phosphorylation can control direction of flux effectively

Question 20

F26BP

Answer 20

only used for regulation purposes; allosteric activator for PFK

Question 21

phosphofructokinase

Answer 21

main regulatory site for glycolysis

Question 22

where do substrates for gluconeogenesis come from?

Answer 22

citric acid cycle- amino acids

Question 23

how does glucose get into blood from liver

Answer 23

glucose-6-phosphatase dephosphorylates G6P for release of glucose into blood; liver uses alanine to make glucose via glucose-alanine cycle;

Question 24

branching of glycolysis

Answer 24

via UDP-glucose pyrophosphorylase; requires energy input; the UDP-glucose can then bind with glycogen (branching enzyme)

Question 25

pentose phosphate pathway

Answer 25

generates NADPH (used to build stuff) and ribose production- both used to build macromolecules

Question 26

pyruvate kinase deficiency

Answer 26

leads to build up in 2,3 BPG because it is a part of the glycolysis pathway–> increase of O2 affinity and so oxygen releases

Question 27

fructose intolerance

Answer 27

aldolase deficiency- F6P cannot be cleaved into two molecules and builds up; reduces ATP because it blocks ATP making steps in the further pathway