CH 16 Glycolysis Stage 1

Question 1

What does glycolysis produce?

Answer 1

pyruvate

Question 2

What are the fates of pyruvate?

Answer 2

1. Fermentation - ethanol.
2. Lactate
3. Complete Oxidation - CO2 and H20

Question 3

Pancreatic and Salivary α-amylase cleaves at the ____ of ____ and ____ to yield ____ and ____.

Answer 3

α-1,4-bonds
starch and glycogen
maltose and maltriose

Question 4

α-glucosidase (maltase)

Answer 4

completes digestion of di and trisaccharides into glucose.

Question 5

Which molecule remains after amylase digestion?

Answer 5

limit dextrin

Question 6

limit dextrin

Answer 6

dextran-rich in α-1,6-bonds.

Question 7

α-Dextrinase

Answer 7

degrades limit dextrin.

Question 8

Sucrase

Answer 8

hydrolyzes sucrose.

Question 9

Lactase

Answer 9

cleaves lactose.

Question 10

Glucose is generated from?

Answer 10

dietary carbohydrates.

Question 11

What is the only fuel that the brain uses under non-starvation cond’s?

Answer 11

glucose

Question 12

RBCs can only use this as fuel?

Answer 12

glucose

Question 13

Why is glucose a prominent fuel in all life forms?

Answer 13

1. available for primitive biochemical systems - formed under prebiotic cond’s.
2. most stable hexose.
3. low tendency to non-enzymatically glycosylate proteins.

Question 14

The glycolytic pathway is common to?

Answer 14

virtually all cells, prokaryotic and eukaryotic.

Question 15

In eukaryotic cells glycolytic enzymes are organized in?

Answer 15

cytoplasmic supramolecular complexes.

Question 16

Cytoplasmic supramolecular complexes are an efficient organization strategy of glycolytic enzymes because?

Answer 16

the substrate channeling btw active sites prevents the release of toxic intermediates.

Question 17

Glycolysis converts one molecule glucose into?

Answer 17

2 molecules pyruvate

generates 2 molecules ATP

Question 18

Glycolysis - Stage 1

Answer 18

traps glucose in cell, modifies it to be cleaved into a pair of phosphorylated 3C compounds.

Question 19

Glycolysis - Stage 2

Answer 19

oxidizes 3C compounds to pyruvate.

generates 2 molecules ATP.

Question 20

The 1st stage of gylcolysis begins with _____ and ends with _____.

Answer 20

Phosphorylation of glucose by hexokinase.

Isomerization of dihydroxyacetone phosphate to glyceraldehyde 3-phosphate.

Question 21

Hexokinase req’s ____ as cofactors to catalyze the rxn?

Answer 21

Mg2+, Mn2+

Question 22

Glucose must enter the cell via?

Answer 22

a specific transport protein

Question 23

Glucose is phosphorylated into ____ at the expense of ____ to form ____.

Answer 23

phosphorylated
ATP
glucose-6-phosphate

Question 24

Hexokinase begins glycolysis by?

Answer 24

trapping glucose in the cell.

Question 25

Hexokinase employs ____ to exclude ____ and minimize the undesired ____.

Answer 25

substrate-binding induced fit
water
hydrolysis of ATP

Question 26

Hexokinase - Induced Fit

Answer 26

two lobes sep’d when glucose is absent.
conf. change when glucose binds.
lobes come together to create necessary environment for catalysis.

Question 27

Step 1 - Glycolysis

Answer 27

Glucose is converted to G6-P.
Phosphorylation via hexokinase.
Irreversible.

Question 28

Step 2 - Glycolysis

Answer 28

G6-P is converted to F6-P.
Catalyzed by phosphoglucose isomerase.
Readily reversible.

Question 29

Step 3 - Glycolysis

Answer 29

F6-P converted to F-1,6-BP.
Catalyzed by allosteric enzyme PFK.
Irreversible.

Question 30

In step 3 of glycolysis the ____ is trapped in ____ form by the addition of a _____.

Answer 30

carbohydrate
fructose
2nd phosphate

Question 31

Step 4 - Glycolysis

Answer 31

F-1,6-BP cleaved into (2) 3C DHAP and GAP.
Catalyzed by aldolase.
Readily reversible rxn.

Question 32

GAP can be processed to ____ to yield ___, while DHAP cannot.

Answer 32

pyruvate.

ATP.

Question 33

Step 5 - Glycolysis

Answer 33

DHAP interconverted to GAP.
Isomerization by enzyme triose phosphate isomerase (TPI / TIM)
Proceeds via enediol intermediate.

Question 34

TPI / TIM is the only glycolytic enzyme for which ____ can be ____.

Answer 34

genetic deficiency in expression.

lethal.

Question 35

Triose Phosphate Isomerase (TIM / TPI) - Structure

Answer 35

Central core of 8 parallel β strands surrounded by 8 parallel α strands.
αβ barrel
His-95 and Glu 165 essential components of active site.
Loop closes off active site upon substrate binding.

Question 36

αβ barrels are found in which glycolytic enzymes?

Answer 36

TPI / TIM
Aldolase
Enolase
Pyruvate Kinase

Question 37

Triose Phosphate Isomerase (TIM / TPI) converts a ____ into a ____ via ____.

Answer 37

Ketose (ketone group ROR’). Aldose (aldehyde group ROH).

Enediol intermediate.

Question 38

Triose Phosphate Isomerase (TIM / TPI) - Mechanism

Answer 38

1. Glu 165 acts as gen base catalyst, removes H+ from substrate’s C1 to form enediol intermediate.
2. Glu 165 acts as gen acid catalyst, donates H+ to C2 while His 95 removes H+ from C1.
3. Product formed, Glu 161 and His 95 return to initial states.

Question 39

TIM / TPI is considered a kinetically perfect enzyme because its?

Answer 39

rate of catalysis is near the diffusion limit.

Question 40

The enediol intermediate of TPI could decompose into?

Answer 40

Reactive methyl gloxal (undesired product).

Structural features in enzyme prevent this.

Question 41

The ____ of an aldehyde to an acid powers formation of a compound with a high ____.

Answer 41

oxidation

phosphoryl-transfer potential

Question 42

When does the second stage of glycolysis begin?

Answer 42

high-phosphoryl transfer potential 1,3-bisphosphoglycerate gen’d by oxidation of GAP in rxn catalyzed by glyceraldehyde 3-phosphate dehydrogenase.