Bioenergetics And High Energy Compounds

Question 1

What is bioenergetics

Answer 1

The study of
energy living systems
in (environments)
and the (plants and animals) that utilize them
organisms.

How organisms manage their energy sources

Question 2

What is energy

Answer 2

capacity to cause change
• It exists in various forms, some of which can
perform work
– Chemical energy is potential energy available for release in a chemical reaction.
• Required by all organisms
• May be Kinetic or Potential energy

• Energy can be converted from one form to another

Question 3

What is k.e

Answer 3

• Energy of Motion
• Heat and light energy are examples

Question 4

What is p.e

Answer 4

•
Energy
of position.
Includes
Energy stored in chemical
Bonds

Question 5

What is free energy

Answer 5

• The free-energy change of a reaction tells us whether the reaction occurs spontaneously
• A living system’s free energy is energy that can do work when temperature and pressure are uniform, as in a living cell

Question 6

What is enthalpy

Answer 6

tell us the heat content (energy) of a system. - delta H

Question 7

What is entropy

Answer 7

tell us whether a process is favourable (spontaneous) ( T delta S)

Question 8

Define free energy change

Answer 8

∆G = ∆H – T∆S

Question 9

Explain a spontaneous reaction

Answer 9

A reaction can occur spontaneously (is favoured) only if ∆G is negative
If: ∆G is negative (-)
• the process is exergonic
• the reaction proceeds with the release of
free energy
• the reaction will be thermodynamically
favourable in the direction written

Question 10

Explain a non spontaneous reaction

Answer 10

A reaction cannot occur spontaneously (is not favoured) if ∆G is positive
If: ∆G is positive (+)
• the process is endergonic
• an input of free energy is required to
drive the reaction
• the reaction will be thermodynamically
unfavoured
(reverse process is favoured)

• Most of these metabolic reactions are not spontaneous
•(i.e., they are accompanied by a positive change in free energy, ΔG>0) and do not occur without some other source of free energy.
• Hence, the body needs some sort of “free-energy currency,” a molecule that can store and release free energy when it is needed to power a given biochemical reaction.

Question 11

What happens to spontaneity at equilibrium

Answer 11

A system is at equilibrium and no net change can take place if ∆G is zero
If: ∆G is zero (0)
•The process is at equilibrium
•No net flow in either the forward or the reverse direction
•Neither process is favoured

Cells are not in equilibrium; they are open systems experiencing a constant flow of materials
A catabolic pathway in a cell releases free energy in a series of reactions

Question 12

What are high energy compounds

Answer 12

• Compounds with a high energy bond
• If the bond is hydrolysed – chemical
energy is made available
• Less favourable reactions can be driven forward
• ATP – most commonly encountered

Question 13

Hydrolysis & dehydration. Exergonic or endergonic

Answer 13

-Hyrolysis is Exergonic
Energy Used by Cells

-Dehydration is Endergonic
Energy is restored in Chemical Bonds

Question 14

Name 5 phosphorylase high energy compounds

Answer 14

• ATP (hydrolysis products are ADP, AMP): major energy carrier

GTP, UTP, CTP: also high energy compound

Phosphoenol pyruvate

•Creatine phosphate (energy storage In muscle cells)

Phosphorylatedcarbohydrates(e.g.glycerol3-phosphate)

Question 15

3 High energy reducing power carriers

Answer 15

: NADPH (NAD+)
NADPH (NADP+)
• FADH, (FAD)

Question 16

High energy coenzyme

Answer 16

Coenzyme A(CoA) (carry “activated” carbon group)
• Acetyl CoA

Question 17

Large negative free energies using example

Answer 17

The free energy change for the hydrolysis of ATP is large and negative

•This equilibrium lies so far to the right that ATP hydrolysis can be considered essentially irreversible
•compounds that can undergo reactions with a resulting large negative free energy change (like ATP) are used as shuttles of free energy in the cell
•(the bonds are said to contain potential transfer energy)

Question 18

Coupling of biochemical reactions

Answer 18

• Because the free-energy changes of sequential reactions are additive;
• Any phosphorylated compound can be synthesized by coupling the synthesis to the breakdown of another phosphorylated compound with a more negative free energy of hydrolysis
(1) Hydrolysis of PEP: PEP pyruvate + Pi
(2) Phosphorylation of ADP: ADP + Pi ATP

Glucose + Pi glucose 6- phosphate
ATP+H20 ADP+Pi ∆

These two reactions share an intermediate (Pi) and may be expressed as sequential (coupled) reactions

cleavage of Pi from phosphoenolpyruvate (PEP) releases more free energy

Question 19

How Much ATP Do Cells Use?

Answer 19

• It is estimated that each cell will generate and consume approximately 10,000,000 molecules of ATP per second

Question 20

What allows ATP to be donor and acceptor

Answer 20

The free energy of phosphate hydrolysis of ATP when compared to other molecules is at the middle.
This allows ATP to accept energy from high energy donor compounds & to act as a donor for low energy phosphate acceptor.

Question 21

Energy levels from high to low ( RANGE FROM -60 TO -10)

Answer 21

Phosphoenolpyruvate

1,3-Bisphosphoglycerate

Phosphocreatine

“High-energy” phosphate
compounds

ATP

“Low-energy” phosphate
compounds

Glucose 6-phosphate

Glycerol-3-phosphate

Question 22

WHY do some compounds have a higher free energy of hydrolysis?

Answer 22

It’s not the phosphate bonds themselves, but rather some property of both the reactants and products in the reactions that contribute to the differences in free energy

Question 23

3 FUNCTIONS CARRIED OUT BY ATP

Answer 23

• Active transport - molecules & ions
• Mechanical work – muscle contraction & other cellular movement
• Biosynthesis of macromolecules
(ATP serves as the immediate donor of free energy in biological systems)

Question 24

3 Compounds with more free energy of hydrolysis than ATP

Answer 24

1. 1,3-bisphosphoglycerate
2. Creatine phosphate (CP)
   store of free energy in muscle
   CP + ADP ATP + creatine
   creatine kinase
3. Phosphoenol pyruvate (PEP in glycolysis)
   PEP + ADP ATP + pyruvate

Question 25

2 examples of CoA Esters

Answer 25

•Succinyl Co A
•Malonyl CoA

Question 26

3 groups of compounds with equal free energy of hydrolysis

Answer 26

1. Nucleoside triphosphates/ Deoxy nucleoside triphosphates:

GTP ATP CTP UTP
(PPi bonds present in all compounds)

Nucleoside diphosphate forms:
ADP GDP CDP UDP
(ATP + GDP GTP + ADP)

2. NuDP Sugars (activated molecules) • UDP glucose
   • CDP glucose
   • ADP glucose
   • UDP galactose
3. NuDP Bases
   • CDP choline
   Glucose derivative polymers Biosynthesis
   Biosynthesis of phospholipids
   All involved in Biosynthesis = Anabolism