Bioenergetics

Question 1

What is bioenergetics?

Answer 1

Study of energy transductions - changes of one form of energy into another - which occurs in living cells and physical-chemical nature

Question 2

What is the direct chemical combustion of glucose?

Answer 2

Going from glucose and oxygen to CO2 and heat

Question 3

What is the cellular combustion of glucose?

Answer 3

Staring with glucose and going to ATP

Question 4

What is gibbs free energy (G)?

Answer 4

Every rxn in the cell is either using or producing energy in different forms

Gibs is the available energy of any substance

Question 5

How is a rxn like A–>B expressed in gibbs free energy (G)?

Answer 5

Both A and B has its own level of gibbs free energy

**A (or B) can have different G based on its physical status like different pH, temp or pressure, etc

**the gibbs free energy of B minus the Gibbs of A is the delta G
Also written as the G of the product minus the G of the substrate is the delta G

Question 6

What are the two types of delta G?

Answer 6

If you see detla G = actual delta G

If you see delta G0 = means standard delta G

Question 7

What does the standard delta G refer to?

Answer 7

The free energy change for a rxn starting at 1 M substrate and 1 M product concentrations and attained equilibrium under standard

** its calculated at equilibrium, which means there is no change in substrate and product concentrations with time

Question 8

What can we predict from the standard delta G when looking at the glycolytic 2nd rxn of glucose 6-P to glucose 1-P?

Answer 8

the delta G0= -.06 kcal/mol
A negative value of delta G0 tells us
1. if the rxn will be spontaneous to move forward
2. at equilibrium, there will be more fructose 6-P than glucose 6-P
4. Exergonic rxn, although ergonic means heat, but can be any form of energy

Question 9

What is a endergonic rxn?

Answer 9

One that requires an input of energy (+delta G0)

Question 10

What is an exergonic rxn?

Answer 10

If any rxn releases energy (-delta G0)

Question 11

What is the reaction quotient (Q)?

Answer 11

Measures the relative amount of products and reactants present during a rxn at a particular point in time

Question 12

What is the equilibrium constant (keq)

Answer 12

Its the value of its rxn quotient Q at chemical equilibrium

**this is fixed for every rxn

Question 13

What happens if the value of Q is lower than Keq?

Answer 13

Reaction will move forward till the value of Q=Keq

Question 14

What happens if the value of Q is higher than Keq?

Answer 14

Rxn will move backward till the value of Q=Keq

Question 15

What is le chatelier’s principle?

Answer 15

Whenever a system in equilibrium is distrubed the system will adjust in such a way that the effect of the change will be nullified

**means that even when you change the system it will do something to bring it back to equilibrium

Question 16

What is meant by pushing the rxn?

Answer 16

It means that a step which comes before another will push a positive delta G0 to move towards it product even tho it isnt spontaneous

Question 17

What is meant by pulling the rxn?

Answer 17

This means that the step following the + delta G0 rxn moves very fast and uses the product created by the step before it, this is make it pull the rxn forward

Question 18

What are high-energy comounds?

Answer 18

The ones which contain phosphate. they are considered high if they can phosphorylate other compounds

They are temporary forms of stored energy and are used to carry energy from one rxn to another

**they can drive positive delta G0 rxns towards negative

Question 19

What happens when you take in more glucose than is needed to feed the cells?

Answer 19

It is going to be taken into the liver and converted into storage forms of glycogen and triglyceride (fat)

Question 20

What is glycogen as cellular fuel storage?

Answer 20

1. Its large and insoluble glucose polymer
2. Almost all cells store some of it as a emergency supply for their own needs
3. Its used by the liver to replenish blood glucose for up to 24 hrs after dietary fuels are depleted
4. The cost = energy cost of 2 ATP for each glucose added to glycogen polymer
5. The benefit of glycogen = less osmotic pressure, if glycogen were stored as free glucose, it would cause an unsustainable increase in cellular osmotic pressure

Question 21

What is fat as cellular fuel storage?

Answer 21

1. Fat is synthesized from excess glucose mostly in the liver and stored in adipose tissue
2. Cost = energy loss, 20% of glucose’s free energy is lost when converted to fat
3. the benefit = efficient energy storage
   * * single triglyceride contains the energy of >10 glucose (minus the cost to make it)
   * ** lipids weigh less and use up less space and water than glycogen