Week 9: Digestion, Metabolism, Glycolysis

Question 1

The ΔG°’ for the reaction Citrate –> Isocitrate is 6.64 kJ mol-1.

The ΔG°’ for the reaction Isocitrate –> α-Ketoglutarate is -267 kJ mol-1.

What is the value of ΔG°’ for the reaction Citrate –> α-Ketoglutarate?

Answer 1

because the product of the first reaction “cancels” the reactant of the second reaction. Thus, the free energy change of the first reaction added to that of the second reaction gives the net free energy change of the net reaction:

ΔG°’net = (6.64 kJ mol-1) + (-267 kJ mol-1) = -260. kJ mol-1

The net reaction is highly favorable toward products. That is, it is very exergonic.

Question 2

The biosynthesis of proteins is an ______ process, and is accompanied by a large ______ in entropy.

Answer 2

endergonic
decrease

Question 3

In the steps of glycolysis, as glucose is converted to lactate or ethanol, ______ and ________ both catalyze reactions that produce ATP, while ________ catalyze reactions that consume ATP.

Answer 3

phosphoglycerate kinase, pyruvate kinase

hexokinase, glucokinase, and phosphofructokinase

Question 4

In the steps of glycolysis, as glucose is converted to pyruvate, _______ catalyzes the conversion of two molecules of glyceraldehyde-3-P to 1,3-bisphosphoglycerate. This reaction consumes an _____ and produces an ______.

Answer 4

glyceraldehyde-3-P dehydrogenase
NAD+, NADH

Question 5

______ catalyzes the conversion of pyruvate to lactate, consuming an _____- and producing an ____ during the reaction.

Answer 5

Lactate dehydrogenase
NADH, NAD+

Question 6

________ catalyzes the conversion of acetaldehyde to ethanol, consuming an ______ and producing an ______ during the reaction.

Answer 6

Alcohol dehydrogenase
NADH, NAD+

Question 7

Changing the oxidation state of a substrate by removing hydrogens

Answer 7

Dehydrogenases

Question 8

Performing an aldol cleavage of a sugar

Answer 8

Aldolases

Question 9

Transferring a phosphate from one substrate to another

Answer 9

Kinases

Question 10

Altering the structural formula of a molecule without altering its molecular formula

Answer 10

Isomerases

Question 11

Three regulatory enzymes:

Answer 11

Hexokinase
Phosphofructokinase
Pyruvate kinase

Question 12

Step 1 - Hexokinase
Glucose –> Glucose 6-Phosphate

Hexokinase tells us its from a _____ carbon ring
When _____ is added, transporter can no longer recognize this and it gets stuck in the cell

Answer 12

6-membered
phosphate

Question 13

A zymogen is a protein that is the ______ form of an enzyme

Answer 13

inactive
A zymogen is just the inactive form of an enzyme that eventually gets activated by other molecules in the digestion process.

Question 13

Generally, when you are adding a phosphate group onto a molecule, it is a thermodynamically ______ reaction.

Thus in the reaction
Creatinine + ATP ⇌ Creatinine phosphate + ADP, the free energy of the forward reaction would be calculated as

Answer 13

ATP is hydrolyzed to ADP (-30.5), while creatinine is phosphorylated to creatine phosphate (+43.1), so -30.5 + 43.1 = +12.6 kJ/mol

Question 14

Catabolic pathways synthesize ______ and are typically ______
Anabolic pathways synthesize ______ and are typically _______

Answer 14

ATP or ion gradients, spontaneous
larger biomolecules, non-spontaneous

Question 15

Coenzyme A carries _____; NADH/NAD+ is an _____ carrier and ATP ‘carries’ ______ groups.

Answer 15

Acyl groups
electron
phosphate

Question 16

Order the enzymes from beginning to end according to the glycolytic pathway.

Answer 16

Hexokinase
Phosphoglucose Isomerase
Phosphofructokinase
Aldolase
Triose Phosphate Isomerase
Glyceraldehyde 3-phosphate Dehydrogenase
Phosphoglycerate Kinase
Phosphoglycerate Mutase
Enolase
Pyruvate Kinase

Question 17

Which enzymes catalyze reactions that produce ATP in glycolysis?

These enzymes specifically ________ from the high phosphoryl transfer potential molecules and ______ to create ATP!

Answer 17

Phosphoglycerate kinase
Pyruvate kinase

remove a phosphate
give it to ADP

Question 18

Under anaerobic conditions in skeletal muscle, pyruvate is converted to ________.

Answer 18

Lactate

Question 19

The primary purpose of alcohol fermentation is _________.

Answer 19

regeneration of NAD+
You recognize that this is an anaerobic condition, so the body will not be able to make more NAD+ that allows glycolysis to take place, and therefore needs to make more of it!

Question 20

Factors that make ATP an energy-rich molecule:

Answer 20

Separating negative charge, decreasing charge repulsion
Increasing resonance
Increase an entropy
Stabilization by hydration

Question 21

ATP can power reactions that would otherwise not take place by providing energy through ______, which ______ a significant amount of energy when the high-energy phosphate bonds are broken. This energy can be coupled to _____ reactions, driving them forward by shifting the equilibrium, thus enabling biological processes that require energy input to occur.

Answer 21

hydrolysis, releases

endergonic

Question 22

Oxidation: ____ C-O or _____ C-H bond

Reduction: ____ C-O or _____ C-H bond

Answer 22

gain, lose

lose, gain

Question 23

Anabolism refers to the set of metabolic pathways that _____ molecules from smaller units, ______ energy to synthesize complex molecules such as proteins and nucleic acids.

Answer 23

construct, utilizing

non-spontaneous

Question 24

catabolism is the process of ______ larger molecules into smaller units, ______ in the form of ATP as nutrients are metabolized.

Answer 24

breaking down, releasing energy

spontaneous