6 Bioenerg

Question 1

What is bioenergetics?

Answer 1

Study of cellular energy changes that accompany biochemical reactions in living cells

Question 2

Two types of biochemical reactions

1. Exergonic
2. Endergonic

A. Spontaneity of reaction
B. Reacting system proceeds from high to low OR low to high energy level
C. Resulting to loss/gain of energy
D. Uphill/Downhill reaction

Answer 2

Exergonic
A. Spontaneous

B. From high to low

C. loss of energy

D. Downhill

Endergonic
A. Non-spontaneous
B. Low to high
C. Gain of energy
D. Uphill reaction

Question 3

Where does an endergonic reaction obtain its energy?

Answer 3

By coupling/linking with an exergonic reaction

Question 4

What happens to energy released after an exergonic reaction?

Answer 4

Becomes chemical energy (driving many cellular reactions) or heat (thermogenesis to maintain normal body temperature)

Question 5

When it is cold, what does your body do?

Answer 5

(1) Shivering thermogenesis, body responds to cold by asynchronous muscle contraction = increase ATP utilization = energy released as heat
(2) Nonshivering thermogenesis = less fuel oxidation to maintain constant ATP levels = more heat generated

Question 6

Two mechanisms in coupling reactions?

Answer 6

1. Formation of a common obligatory intermediate for both reactions (*linking the exergonic with the endergonic reactions)
2. Formation of high-energy intermediate compound from the energy released in the exergonic reaction. (*ATP; used to push through with endergonic reaction)

Question 7

Laws of Thermodynamics

Answer 7

1. First Law (Law of Conservation of Energy)
2. Second Law of Thermodynamics
   >In all natural processes, the universe tends towards disorder. Hence, the total entropy of a system must increase if a reaction is to occur spontaneously.

Question 8

Measure of the degree/disorder/randomness of a system

Answer 8

Entropy

Question 9

ATP Structure?

Which part stores energy?

Answer 9

ATP Structure

(1) adenine nitrogenous base
(2) ribose sugar
(3) Triphosphate group

1 & 2 linked at N9 and OH of C1 ribose by N-glycosidic bonds

Phosphate groups in 3 linked by phosphoanhydrous bonds

> Beta and gamma bonds store energy/high energy

Question 10

Why is ATP the common currency of the cell?

Answer 10

Besides placing, the phosphoanhydrous bonds are unstable because of the negativity of the Phosphate bonds causing them to repel each other. Thus, need high energy for PO4 to stay together.

Question 11

ATP Hydrolysis in beta phosphate bond leads to?in gamma phosphate bond?

Answer 11

ATP Hydrolysis

Gamma phosphate bond:
ATP -> ADP + Pi Delta G0 = -7.3 kcal/mol

Beta phosphate bond

ATP -> AMP + PPi
DeltaG0 = -7.3 kcal/mol

Question 12

AMP hydrolysis

Answer 12

AMP -> Adenosine + Pi

Energy released = -3.4 kcal/mol

Question 13

Nucleoside triphosphates and diphosphates in aqueous solution and at active sites of enzymes are usually present as complexes with what ion? Nomenclature/Classification?

Answer 13

Mg2+

Either alpha, beta complex of MgATP
Or beta, gamma complex of MgATP

Question 14

Josiah Gibb’s Equation

Answer 14

AG = AH - TAS

AG = change in free energy os the system

AH = change in enthalpy

T = absolute temperature

AS = change in entropy of the system

Question 15

If AG (change in free energy) is:

(1) AG > 0
(2) AG < 0
(3) AG = O

Answer 15

AG > 0 = (+) = Non-spontaneous/endergonic = Products formed will have more energy than reactants

AG < = = (-) = Spontaneous/exergonic = Products have less chemical energy than reactants

AG = 0 = system in equilib bc reacting system has exhausted its capacity to do work

Question 16

What represents maximum amount of energy capable of doing work that can be obtained from a reaction?

Answer 16

AG = difference in Gibb’s free energy

Question 17

Formula for standard free energy change (AG0) of a chemical reaction

Results interpretation

Answer 17

AG0 = -2.303 RT log Keq

*R = 1.987 cal/mol/deg
T = abs temp

AG0 = Algebraic sum of the standard changes in free energy of a consecutive series of reactions

If Keq = 1, AG0 = 0 -> No free energy
If Keq > 1, AG0 = (-) -> Exergonic rxn
If Keq < 1, AG0 = (+) -> Endergonic rxn

Question 18

Can AG0 predict whether a reaction can occur?

Answer 18

No because standard conditions do not always prevail in body cells

Question 19

Compute AG from AG0

Answer 19

AG = AG0 + RT ln (([C][D])/([A][B]))

Question 20

If you increase the substrate concentration and decrease the product of an exergonic rxn, what will happen?

Answer 20

Same. Will still move forward.

Question 21

Why is ATP the common currency of the cell?

Answer 21

-

Question 22

E.g. of osmotic work by ATP?

Answer 22

-

Question 23

Chemical work of ATP: Heme synthesis

Answer 23

E.g. Proprionyl CoA -> D-methyl malonyl CoA

Question 24

De novo synthesis of fatty acids

Answer 24

Acetyl CoA -> Malonyl CoA

Question 25

TAG synthesis

Answer 25

Glycerol -> G3P

Question 26

Metabolic roles of ATP

Answer 26

1. Phosphoryl-group transfer (Glutamate (+NH3) -> Glutamine)
2. Production of ATP by Phosphoryl-group transfer (PEP -> Pyruvate)
3. Nucleotidyl Group Transfer (Acetate -> Acetyl CoA)

Question 27

Why is ATP an ideal carrier of molecules?

Answer 27

=

Question 28

Major sources of P in energy conservation

Answer 28

1. Oxidative Phosphorylation (Most Abundant)
2. Glycolysis
   A. Phosphoglycerate kinase
   B. Pyruvate kinase
3. Kreb’s
   Succinate thiokinase

Question 29

Creatine kinase importance

Answer 29

Production of ATP from phosphocreatine