Glycolysis

Question 1

the breakdown of glucose by enzymes, releasing energy and pyruvic acid

Answer 1

glycolysis

Question 2

where does glycolysis occur

Answer 2

in the cytosol of the cell

Question 3

glycolysis is also known as the

Answer 3

EMP Pathway (Embden – Meyerhof – Parnas Pathway)

Question 4

net reaction of glycolysis

Answer 4

glucose (6C) + 2 NAD+ 2 ADP +2 inorganic phosphates (Pi) yields 2 pyruvate (3C) + 2 NADH + 2 H+ + 2 net ATP (bc investment phase used 2 atp)

Question 5

2 phases of glycolysis

Answer 5

the “investment phase” because it requires an input of energy in the form of 2 ATPs per glucose molecule (steps 1-5, results in 2 3C molecules) and. the “pay off phase” because energy is released in the form of 4 ATPs, 2 per glyceraldehyde molecule. (steps 6-10)

Question 6

step 1 of glycolysis

Answer 6

phosphorylation of glucose

A phosphate group is transferred from ATP to glucose, making glucose-6-phosphate. Glucose-6-phosphate is more reactive than glucose, and the addition of the phosphate also traps glucose inside the cell since glucose with a phosphate can’t readily cross the membrane.

enzyme: hexokinase
cofactor: Mg2+

Question 7

step 2 of glycolysis

Answer 7

isomerization of glucose-6-phosphate

Glucose-6-phosphate is converted into its isomer, fructose-6-phosphate.

enzyme: phosphoglucoisomerase/phosphoglucose isomerase
cofactor: Mg2+

Question 8

step 3 of glycolysis

Answer 8

phosphorylation of fructose-6-phosphate

A phosphate group is transferred from ATP to fructose-6-phosphate, producing fructose-1,6-bisphosphate.

enzyme: phosphofructokinase (can be regulated to speed up or slow down the glycolysis pathway.)
cofactor: Mg2+

Question 9

step 4 of glycolysis

Answer 9

cleavage of fructose 1,6-bisphosphate

Fructose-1,6-bisphosphate splits to form two three-carbon sugars: dihydroxyacetone phosphate (DHAP) and glyceraldehyde-3-phosphate. They are isomers of each other, but only one—glyceraldehyde-3-phosphate—can directly continue through the next steps of glycolysis.

enzyme: aldolase

Question 10

step 5 of glycolysis

Answer 10

isomerization of DHAP

DHAP is converted into glyceraldehyde-3-phosphate.

enzyme: triose phosphate isomerase

Question 11

step 6 of glycolysis

Answer 11

glyceraldehyde-3-phosphate is oxidized, extracting high-energy electrons, which are picked up by the electron carrier NAD+, producing NADH. The sugar is then phosphorylated by the addition of a second phosphate group (from hydrogen phosphate), producing 1,3-bisphosphoglycerate.

enzyme: glyceraldehyde phosphate dehydrogenase

Question 12

step 7 of glycolysis

Answer 12

transfer of phosphate from 1,3-BPG to ADP

1,3-bisphosphoglycerate donates one of its phosphate groups to ADP making a molecule of ATP and turning into 3-phosphoglycerate in the process.

enzyme: phosphoglycerate kinase
cofactor: Mg2+

Question 13

step 7 of glycolysis

Answer 13

transfer of phosphate from 1,3-BPG to ADP

1,3-bisphosphoglycerate donates one of its phosphate groups to ADP making a molecule of ATP (from substrate-level phosphorylation) and turning into 3-phosphoglycerate in the process.

enzyme: phosphoglycerate kinase
cofactor: Mg2+

Question 14

step 8 of glycolysis

Answer 14

isomerization of 3-PGA

3-phosphoglycerate is converted into its isomer, 2- phosphoglycerate.

enzyme: phosphoglycerate mutase
cofactor: Mg2+

Question 15

step 9 of glycolysis

Answer 15

dehydration of 2-PGA

2-phosphoglycerate loses a molecule of water, becoming phosphoenolpyruvate (PEP). PEP is an unstable molecule, poised to lose its phosphate group in the final step of glycolysis.

enzyme: enolase

Question 16

step 10 of glycolysis

Answer 16

transfer of phosphate from PEP

PEP readily donates its phosphate group to ADP, making a second molecule of ATP. As it loses its phosphate, PEP is converted to pyruvate, the end product of glycolysis.

enzyme: pyruvate kinase
cofactor: mg2+

Question 17

end products of the yield phase

Answer 17

2 H2O, 2 NADH, 4 ATP, 2 H+, 2 Pyruvate (doubled product since 1 Glucose produces 2 G3P in the yield phase)

Question 18

which steps of glycolysis is irreversible and why

Answer 18

steps 1, 3, and 10

Some steps in glycolysis are irreversible because they are needed to control the glycolytic pathway and ensure the production of ATP.

Question 19

where does pyruvate go in glycolysis

Answer 19

aerobic respiration/anaerobic respiration/fermentation