9.4-9.5 Glycolysis Regulation

Question 1

what are the 3 irreversible steps of glycolysis? what enzymes catalyze each step?

Answer 1

step 1: hexokinase
step 3: PFK-1
step 10: pyruvate kinase

Question 2

how is step 1 of glycolysis regulated? (what general kind of inhibition)

Answer 2

feedback inhibition by product

Question 3

how is hexokinase regulated? (catalyzes step 1 of glycolysis)

Answer 3

inhibited by glyceradehyde-3-phosphate

Question 4

compare and contrast hexokinase and glucokinase

Answer 4

hexokinase is found in most cell types, binds hexoses with a greater binding affinity (smaller Km), and IS inhibited by G3P
whule glucokinase is only in liver and peancreatic cells, only binds to glucose with a lower binding affinity and IS NOT inhibited by G3P

Question 5

where does excess glucose go? for what?

Answer 5

excess glucose flows to the liver for energy storage

Question 6

how is energy stored in the liver? (2)

Answer 6

1. production glycogen
2. fatty acid synthesis

Question 7

what does glucokinase lead to in pancreatic beta cells? (remove this note when you have added the full signalling mechanism)

Answer 7

insulin release

Question 8

what does insulin signal for? (6 but give general also)

Answer 8

1. activate glucose utilization
2. increase glycolytic flux
3. build glycogen
4. builds TAGs
5. store fat
6. stop hunger
   basically tells body to use glucose in some way bc we haven enough to use it

Question 9

what does PFK-1 regulate?

Answer 9

step 3 of glycolysis; so regulates glycolytic flux (the entire pathway because RDS)

Question 10

how is PFK-1 regulated generally?

Answer 10

by the energy charge of the cell

Question 11

what activates PFK-1? (3) why?

Answer 11

1. AMP
2. ADP
3. fructose-2,6-bisphosphate
   all signal low energy charge in the cell

Question 12

what inhibits PFK-1? (3) why?

Answer 12

1. ATP
2. citrate
3. PEP (end of glycolysis)
   all signal high energy charge

Question 13

what are the two states of PFK-1?

Answer 13

T state: inactive
R state: active

Question 14

describe allosteric regulation of PFK-1 (2)

Answer 14

1. high energy charge (like from more ATP) means the T state is dominant and PFK-1 is inactive
2. low energy charge (like from AMP and ADP) mean that the R state is dominant and PFK-1 is active

Question 15

what are 2 sources that glycolytic intermediates can be obtained from other than food?

Answer 15

1. disaccharides can be broken down to obtain sugars as glycosidases break glycosidic bonds and isomerase can form glucose and fructose
2. lipids can be broken down by lipases and converted to glyceraldehyde-3-phosphate for the glycolysis pathway

Question 16

what are glycosidases?

Answer 16

a specific enzyme that cuts specific glycosidic bonds; the enzyme name mathces the disaccharide it cuts

Question 17

what causes a lactose intolerance?

Answer 17

lacking the lactase enzyme (the glycosidase that degrades lactase)

Question 18

what is crucial for controlling glycolytic flux that can be affected by several metabolites entering at several different points?

Answer 18

choke points in steps 1, 3, and 10

Question 19

how does galactose enter glycolysis?

Answer 19

galactose goes through a series of conversions to get to glucose-6-phosphate which enters at step 2

Question 20

what do glycolysis intermediates do?

Answer 20

create carbn backbones used to synthesize essential biocompounds

Question 21

what are the 2 possible fates of pyruvate under anaerobic conditions?

Answer 21

1. lactic acid fermentation
2. alcohol fermentation

Question 22

what is lactic acid fermentation? when does it occur?

Answer 22

production of lactate under anaerobic conditions

Question 23

in what organisms does alcohol fermentation occur? what does it produce and where is it used?

Answer 23

in microorganisms; produces ethanol which is used in commercial alcohol production

Question 24

what is the fate of pyruvate under aerobic conditions?

Answer 24

CO2 and H2O production during oxidative phosphorylation