Chapter 18 (Glycolysis)

Question 1

Glycolysis is ten reactions that are (different/the same) in all cells but have (different/the same) rates of reaction

Answer 1

the same different

Question 2

The products of glycolysis are

Answer 2

2 NADH 2 ATP (net) 2 pyruvate

Question 3

Three possible fates for pyruvate

Answer 3

Aerobic oxidation (TCA cycle) Anaerobic glycolysis (2 lactate) Anaerobic fermentation (2 ethanol + 2 CO2)

Question 4

Two stages of glycolysis

Answer 4

First stage - the conversion of a 6C sugar to 2 3C sugars (requires 2 ATP) Second stage - the energy products (produces 2 NADH + 4 ATP)

Question 5

The first reaction of glycolysis (Stage 1) Hexokinase

Answer 5

The phosphorylation of glucose Irreversible Priming reaction Requires 1 ATP

Question 6

Reaction 1 of glycolysis is important because (Stage 1)

Answer 6

Glucose readily diffuses through the cell via facilitated diffusion (which goes from high to low concentrations) so the conversion of glucose to glucose-6-P allows it to stay inside the cell (cannot diffuse across)

Question 7

Why is the first reaction in glycolysis not the most important? (Stage 1)

Answer 7

Because glucose-6-P can go into several different metabolic pathways

Question 8

Why is H2O excluded from a kinase active site

Answer 8

Because the -OH of H2O would hydrolyze the ATP (instead of the gamma phosphate going to the -OH on the C#6 in glucose)

Question 9

The second reaction of glycolysis (Stage 1) Phosphoglucose Isomerase (PGI)

Answer 9

It is the isomerization of glucose-6-P into fructose-6-P Changes an aldehyde into a ketone

Question 10

Why is the second reaction of glycolysis important? (Stage 1)

Answer 10

Because it makes the C#1 in fructose-6-P easier to be phosphorylated (primary -OH) Activates C#3 for cleavage in the aldolase reaction (breaking of bond between C#3 and C#4)

Question 11

An isomerase reaction will always have a ___ intermediate

Answer 11

endiolate intermediate (HO-C=C-OH)

Question 12

The third reaction of glycolysis (Stage 1) Phosphofructokinase (PFK)

Answer 12

It is the phosphorylation of the C#1 of fructose-6-P which produces fructose-1,6-BP The first committed step of glycolysis The second priming reaction Highly regulated Requires 1 ATP

Question 13

When energy is low the enzyme phosphofructokinase activity (increases/decreases) and vis versa

Answer 13

increases

Question 14

The bis- in bisphosphate means

Answer 14

That there are 2 phosphate groups but they are not attached to one another

Question 15

The fourth reaction of glycolysis (Stage 1) Aldolase

Answer 15

The cleavage of fructose-1,6-BP in between C#3 and #4 into 2 3C sugars: DHAP and GAP

Question 16

For an aldol cleavage to occur between the C#3 and C#4 in fructose-1,6-BP, there must be

Answer 16

a carbonyl at C#2 (C=O) and a hydroxyl group at C#4 (C-OH) This is one of the reasons why the isomerization of glucose-6-P to fructose-6-P is so important

Question 17

Class I Aldolase

Answer 17

Animal aldolases that form a covalent Schiff base intermediate between a substrate and the active site on lysine (Fru-C=N-lys)

Question 18

The reason why we make a Schiff base

Answer 18

Because the carbon in the Schiff base is more electrophilic

Question 19

Class II Aldolase

Answer 19

Occurs in bacteria and fungi A metal ion (usually Zn) is used as the active site No Schiff base is formed

Question 20

The fifth reaction of glycolysis (Stage 1) Triosphosphate Isomerase (TIM)

Answer 20

The isomerization of DHAP into GAP A ketone to aldehyde isomerization

Question 21

In the cell which concentration is usually higher - DHAP or GAP?

Answer 21

DHAP because it helps with regulation

Question 22

Carbon labeling of GAP

Answer 22

Aldehyde = C#3 or C#4 Alcohol = C#2 or C#5 Phosphate group = C#1 or C#6

Question 23

The sixth reaction of glycolysis (First of Stage 2) GAP Dehydrogenase (GAPDH)

Answer 23

The oxidation (of the aldehyde) and the phosphorylation of GAP by NAD and Pi which produces 1,3-Bisphophoglycerate Since the aldehyde is oxidize that means the NAD+ is reduced

Question 24

Is 1,3-Bisphosphoglycerate (BPG) considered a high energy or low energy compound?

Answer 24

High energy

Question 25

Using the enzyme GAPDH involves a ___ transfer and a ___ intermediate

Answer 25

hydride transfer (from GAP to NAD) acylthioester intermediate (E-S-C=O)

Question 26

The seventh reaction of glycolysis (Second of Stage 2) Phosphoglycerate Kinase (PGK)

Answer 26

The transfer of a phosphate group from 1,3-BPG to ADP which yields 3-Phosphoglycerate Produces the first ATP of glycolysis Considered substrate level phosphorylation because it takes the “high energy” phosphate from 1,3-BPG

Question 27

The eighth reaction of glycolysis (Third of Stage 2) Phosphoglycerate Mutase (PGM)

Answer 27

The transfer of a phosphate group from C#1/6 to C#2/5 to yield 2-Phosphoglycerate Has unique phosphorylated Histidine in its active site Important step in creating the next high energy compound

Question 28

Mutase

Answer 28

catalyzes the transfer of a function group from one position to another on a molecule

Question 29

Using the enzyme PGM forms a ___ intermediate

Answer 29

2,3-BPG intermediate required in trace amounts to regenerate PGM when it is inactive

Question 30

The ninth reaction of glycolysis (Fourth of Stage 2) Enolase

Answer 30

The dehydration of 2-PG (-OH on C#1/6) into Phosphoenolpyruvate Creates a compound (PEP) that is capable of synthesizing ATP via its high energy phosphate

Question 31

The last reaction of glycolysis (Fifth of Stage 2) Pyruvate Kinase

Answer 31

The transfer of a phosphate group from C#2/5 on PEP to ADP to generate ATP Irreversible Involves a tautomerization

Question 32

Tautomerization

Answer 32

Going from the enol form (O-C=C-R) to the more stable keto form (O=C-C-R)

Question 33

The tautormerization produced when using Pyruvate Kinase is very

Answer 33

exergonic and represent the majority of the phosphoryl group transfer potential of PEP (where all the energy in the reaction comes from)

Question 34

What are the three irreversible steps of glycolysis and why are they irreversible

Answer 34

Hexokinase Phosphofructokinase Pyruvate kinase They are irreversible because they have a large delta G

Question 35

What is the overall reaction of glycolysis

Answer 35

Glucose + 2 NAD + 2 ATP + 2 Pi goes to 2 Pyruvate + 2 NADH + 2 ATP + 2 H2O + 4 H

Question 36

For glycolysis to continue ___ must be recycled to ___

Answer 36

NADH NAD+

Question 37

Through glycolysis there is a net ATP gain of ___ per molecule of Glucose

Answer 37

2