Sugar Metabolism Flashcards
major carbohydrates
sucrose
lactose
starch
high-fructose corn syrup
sucrose
glucose - fructose
lactose
galactose - glucose
starch
polymeric form of glucose
high -fructose corn syrup is __% fructose?
55%
Glycolysis is broken down from a __ carbon sugar to ________
6-carbon sugar to 2 pyruvate
Glycolysis occurs in the
cytoplasm
Can glycolysis occur when oxygen levels are low?
yes
energy consuming phase _______ ATP and energy producing phase ______ ATP
requires, produces
How does glucose go from the bloodstream to the cell membranes?
through glucose transporters like GLUT (are in the cell membrane)
What prevents glucose from exiting cell?
the enzyme kinase
What changes the shape of glucose?
when kinase adds a phosphate group (comes from breakdown of ATP to ADP)
this then does not allow it to diffuse
What is the name of 2 Kinase and what do they do?
hexokinase & glucokinase
- they add a phosphate group to the 6 carbon end of a glucose molecule
What is the difference between hexokinase and glucokinase?
hexokinase is found in all cells
glucokinase is induced by the presence of insulin ( found in liver and beta cells of pancrease)
Is the third step in glycolysis irreversible or reversible?
irreversible
What steps of glycolysis are irreversible?
1,3,10
What is the rate limiting step? What enzyme?
3rd step, with the enzyme PFK1
When blood glucose goes up, insulin goes up, and this makes more _____ which makes more
PFK2, PFK1
When blood glucose go back to normal, pancreas secretes _____
glucagon
Glucagon inhibits
PFK2
What happens when PFK2 is inhibited by glucagon?
It slows down the rate of glycolysis because it will not be making fructose 2,6-bisphosphate which makes more PFK1. So less PFK1 = lower rate of glycolysis
How many G3P molecules per glucose molecules?
2
each G3P is converted to __________ by ________.
1,-3-Bisphosphoglycerate (1,3-BPG) by GAP dehydrogenase
What upregulates pyruvate kinase?
fructose-1,6-bisphosphate
- feed-forward regulation
What downregulates pyruvate kinase?
high ATP or alanine
- alanine comes from skeletal muscle breakdown during fasting
High levels of alanine signify that the body needs to
make more glucose not break it down in glycolysis
- since alanine is released when skeletal muscle is being broken down bc of fasting (hence the body is looking for glucose) you do not want to waste glucose by breaking it down during glycolosis
Is glycolysis aerobic or anaerobic?
anaerobic
What cells have limited oxygen?
RBC (bc no mitochondria), exercising skeletal muscle cell
glycolosys makes net
2 ATP
2 NADH
1 NADH makes __ ATP in the mitochondria
3
1 FAD can make __ ATP
2
1 glucose makes __ Net ATP
38
