(Dr. McLachlin) (Unit B) Topic Note 8

Question 1

What is required to determine if a chemical reaction requires energy to procedd in a particular direction?

Answer 1

Change in Gibbs free energy
* ΔG = Gproducts - Greactants

Question 2

When is ΔG negative?

Answer 2

When G of reactants is higher than G of the products
* Reaction is spontaneous and energetically favorable

Question 3

Le Chatelier’s Principle

Answer 3

Reaction shifts to counteract any change that is made
* Happens to reactions at equilibrium, when reactions are reversible

Question 4

How do energetically unfavorable processes occur?

Answer 4

1. Reaction coupling: Couple the reaction to an energetically unfavorable one so that the total net ΔG is negative

Question 5

What kind of bond does ATP have?

Answer 5

“High-energy” phosphoanhydride bond

Question 6

What can ATP be hydrolyzed into?

Answer 6

• ADP + Pi
• AMP + PPi (pyrophosphate)

Question 7

Metabolism

Answer 7

The combined sum of the chemical reactions that occur in living organisms

Question 8

What is metabolism split into?

Answer 8

• Catabolism: Breaking down of large molecules into smaller ones
• Anabolism: Combining of small molecules to make larger ones

Question 9

What reactions of optimal points to control the flux through a metabolic pathway?

Answer 9

Irreversible reactions
* They are far away from the equilibrium

Question 10

What would increasing the activity of an enzyme catalyzing a reversible reaction result in?

Answer 10

Increased rate of reaction in both directions, with little/no net effect

Question 11

What are two important mechanisms used to rapidly change enzyme activity?

Answer 11

1. Allosteric regulation
2. Covalent modification

Question 12

Allosteric enzymes can bind…

Answer 12

Effectors
* At sites other than the active site

Question 13

What does binding of effectors cause?

Answer 13

Conformational changes in the enzyme that increase of decrease its activity

Question 14

What function does PEP have on phosphofructokinase?

Answer 14

Effector, feedback inhibition
* Meatbolite in a metabolic pathway inhibits an enzyme that function earlier in the pathway

Question 15

Does allosteric inhibition obey Michaelis-Menten kinetics?

Answer 15

No it does not

Question 16

What is one group that commonly regulates enzyme activity?

Answer 16

Phosphate

Question 17

What is the phosphorylation state of a target enzyme controlled by?

Answer 17

• Protein kinase: Adds phosphate
• Protein phosphatase: Removes phosphate

Question 18

What is phosphorylation used for?

Answer 18

Used to transmit and amplify signals from outside the cell to the nucleus to control gene expression

Question 19

Reduction vs. Oxidation

Answer 19

• Reduction: Gain of electrons
• Oxidation: Loses electrons

Question 20

What are two key biological molecules involved in red-ox reactions?

Answer 20

• Nicotinamide Adenine Dinucleotide (NAD)
• Nicotinamide Adenine Dinucleotide Phosphate (NADP)

Question 21

What are the oxidized forms of NAD and NADP?

Answer 21

• NAD+
• NADP+

Question 22

What are the reduced forms of NAD and NADP?

Answer 22

Add a H- ion
* NADH
* NADPH

Question 23

What is the reducing power of NADH used for?

Answer 23

Regenerate ATP from ADP

Question 24

What is the reducing power of NADPH used for?

Answer 24

Used in the synthesis of biomolecules, notably fatty acids and cholesterol

Question 25

Describe:

Ubiquinone

Answer 25

Also known as Coenzyme Q or simply, Q
* Has a long hydrophobic polyisoprene tail
* Can accept electrons temporarily

Question 26

What is the reduced form of ubiquinone?

Answer 26

QH2

Question 27

NADH vs. QH2

Answer 27

• Both are used to generate ATP
• NADH is water soluble
• QH2 is very hydrophobic

Question 28

Where are QH2 molecules found?

Answer 28

Embedded in the inner mitochondrial membrane