Bioenergetics

Question 1

What constitutes an exergonic reaction?

Answer 1

An exergonic reaction is a spontaneous reaction, therefore, the Gibbs free energy is negative as the reaction releases energy.

Question 2

What constitutes an endergonic reaction?

Answer 2

An endergonic reaction is not spontaneous, therefore the Gibbs free energy is positive and the reaction takes in energy.

Question 3

Under what conditions is a reaction neither endergonic nor exergonic?

Answer 3

If there is no change in Gibbs free energy then the reaction is neither endergonic or exergonic.

In other words, the change in Gibbs free energy is zero.

Question 4

What is the Gibbs free energy equation?

Answer 4

∆𝐺=∆𝐻−𝑇∆𝑆

The change in Gibbs free energy is equal to the change in enthalpy minus the temperature*change in entropy

Question 5

What is entropy?

Answer 5

(S) is a quantitative expression for the randomness (disorder) in a system

Question 6

How do you increase entropy?

Answer 6

When the products of a reaction are less complex AND more disordered than reactants.

Question 7

How do you decrease entropy?

Answer 7

When the reactants are less complex and disordered than the products.

Question 8

What is enthalpy?

Answer 8

(H) is the heat content of the reacting system. It reflects the number and kinds of chemical bonds win the reactants and products.

Question 9

What is happening if enthalpy is increased?

Answer 9

When the reaction consumes heat the change in enthalpy is positive.

Question 10

What is standard free energy?

Answer 10

Change in Gibbs free energy of a reaction when the conditions are ‘standard.’ You must include the concentrations.

Question 11

How do you find standard free energy?

Answer 11

Standard free energy is equal to the negative R times the temperature in Kelvin times the equilibrium constant.

∆𝐺^′°=−𝑅𝑇 ln(Keq)

∆𝐺^′°=−𝑅𝑇 ln⁡( [products at equilibrium]/[reactants at equilibrium] )

Question 12

What reaction conditions are used to measure standard free energy?

Answer 12

Temperature at 25C aka 298K
Atmospheric Pressure at 1 atm
pH at 7
55.5M H2O
1 mM Mg2+
1M of substrates
1M of products

Question 13

What is Gibbs free energy?

Answer 13

Gibbs free energy expresses the amount of energy capable of doing work at constant temperature and pressure.

Question 14

What is standard temperature in celsius?

Answer 14

25

Question 15

What is standard temperature in Kelvin?

Answer 15

298K

Question 16

What is standard body temperature?

Answer 16

310K

Question 17

What is the change in Gibbs free energy equation in relation to standard gibbs free energy?

Answer 17

∆𝐺=∆𝐺′°+𝑅𝑇 ln⁡〖[𝐵_𝑟𝑒𝑎𝑙 ]/[𝐴_𝑟𝑒𝑎𝑙 ] 〗

Question 17

What is the change in Gibbs free energy equation in relation to standard gibbs free energy?

Answer 17

∆𝐺=∆𝐺′°+𝑅𝑇 ln⁡〖[𝐵_𝑟𝑒𝑎𝑙 ]/[𝐴_𝑟𝑒𝑎𝑙 ] 〗

Question 18

If a reaction is moving forward is it exergonic or endergonic?

Answer 18

exergonic

Question 19

How many ways are there for endergonic reactions to occur?

Answer 19

2

Question 20

One way for an endergonic reaction to occur involves the coupling of the reaction to a strongly exergonic reaction with a shared intermediate. How many steps does this involve?

Answer 20

This is a two-step reaction.

Question 21

What molecule is often used to help endergonic reactions to proceed?

Answer 21

ATP because it is highly exergonic. First the reactant reacts with ATP to create a reactant-phosphate complex and then reacts with the other reactant to form the products and free phosphorus.

Question 22

When ATP is used to help an endergonic reaction to proceed, is that known as pushing or pulling the reaction?

Answer 22

Pushing

Question 23

What is meant when saying an endergonic reaction is pulled?

Answer 23

The reaction is said to be pulled when the endergonic reaction is coupled with an exergonic reaction. The sum of both of these products is negative so it continues.

Question 24

How do you find the the Keq of a net reaction for two sequential reactions?

Answer 24

Ka mulitplied by Kb = Keq

Question 25

What molecule does ATP become when the first phosphate bond is cleaved?

Answer 25

ADP

Question 26

What molecule does ADP become when the 2nd phosphate bond is cleaved?

Answer 26

AMP

Question 27

What is the main source of chemical energy in most organisms?

Answer 27

Oxidation of reduced carbon

Question 28

Do reduced carbons have more or less electrons than oxidized carbons?

Answer 28

Reduced carbons have less electrons. Typically have less oxygens too.

Question 29

Will the oxidation of glucose or a fatty acid provide more chemical energy per carbon atom given they have the same number of carbons?

Answer 29

The oxidation of the carbon is the main source of energy in organisms. The fatty acid will provide more chemical energy because each carbon has more potential to be oxidized.

Question 30

What is the symbol for Reduction Potential?

Answer 30

∆𝐸

Question 31

Name four types of redox reactions

Answer 31

1. Direct transfer of electrons
2. Transfer of hydrogens
3. Transfers of an hydride anion (H-)
4. Direct combination with oxygen

Question 32

What type of agent (reducing/oxidizing) is the most reduced reactant?

Answer 32

Reducing

Question 33

Redox reactions can be written as two half-reactions. In which direction are the half-reactions written?

Answer 33

They are written in the direction of reduction. The product is reduced.

Question 34

Which way will electrons spontaneously flow based on the Reduction Potentials?

Answer 34

The electrons will spontaneously flow from the more negative reduction potential to the more positive reduction potential

Question 35

How can you tell spontaneity from the ruction potential?

Answer 35

The larger/positive the number, the more likely the reaction will be spontaneous

Question 36

How do you find the change in reduction potential?

Answer 36

∆𝐸=𝐸_𝑜𝑥 − 𝐸_𝑟𝑒𝑑
aka
∆𝐸=𝐸_𝑎𝑐𝑐𝑐𝑒𝑝𝑡𝑜𝑟−𝐸_𝑑𝑜𝑛𝑜𝑟