Topic 10 - Bioenergetics and Thermodynamics Flashcards
Living cells require energy for…?
Synthesis of new macromolecules and chemical bonds Transport against [] gradient Mechanical work Maintenance of body temp.
Name 3 energy rich compounds that cells use to extract energy
Glucose Fatty Acids Proteins
Draw the diagram that represents the maintenance of dynamic steady state
What is metabolism and what are the two types of reactions that occur with in cells?
Metabolism: Sum of ALL biochemical reactions w/in cell
Catabolic (exergonic) reactions: energy-liberating (∆G is -ve). Spontaneous.
Anabolic (endergonic) reactions: energy-requiring (∆G is +ve). Not sponaneous.
What is causes thermodynamically unfavourable (endergonic/anabolic) reactions to occur?
They are coupled w/ exergonic/catabolic reactions so overall process has a -ve free energy change and so will occur spontaneously.
What is a metabolic pathway?
Sequence of consecutive biochemical reactions
- product of one reaction becomes reactant in next
- each step in pathway constitutes a sml chemical change
Describe the two types of metabolic pathways
Catabolic pathways:
- Degradative-lrg molecules into sml molecules
- Release energy
- Energy is conserved in ATP and reduced e carriers (NADH, FADH2)
Anabolic pathways:
- Build up -sml molecules into lrg molecules
- Require energy input -ATP and reducing power (NADH, FADH2)
What is reciprocal regulation and why does it occur?
Activation of one pathway, suppression of another.
Used to prevent simultaneous synthesis and degradation which is wasteful
Name the four major metabolic control mechanisms
Control of:
- Intracellular substrate concentration
- Allosteric enzymes by inhibitors and activators
- Amount of enzymes
- Enzymes through signalling substances (eg hormones)
Describe the control of intracellular concentration
Concentration (availability) of substrate affects rate of reaction
Describe control of allosteric enzymes
Allosteric enzymes respond to key inhibitors and activators
Activity can be inhibited or activated by the level of product or other chemical
-Feedback inhibition: product of a metabolic PW allosterically inhibits an enzyme in that PW
The amount of enzymes present can be controlled by…? (among other things)
regulating rate of synthesis of proteins
Hormonal control of enzymes and metabolic PW’s involves activation or inhibition by phosphorylation.
T or F?
True, duhhh
Name the five reaction classes of Biochemistry
- Group transfer reactions
- Oxidation-reduction
- C-C cleavage
- Internal rearrangements, isomerisation, elimination
- Free radical reactions
What is the 1st Law of Thermodynamics?
- Total amount of energy in universe remains constant
- Energy can be changed or transported from one region to another
- It cannot be created or destroyed
What is the 2nd Law of Thermodynamics?
Do living organisms violate this? How?
-In all natural processes, entropy of universe increases
Yes. Does not require that a reacting system increase entropy. Order in our cells is offset by disorder in our surroundings
Name and define the two quantities that describe energy changes
Gibbs free energy (G) and Gibbs free energy change (∆G)
- Amount of energy in a reaction
- Determines whether reactions are spontaneous
When ∆G is -ve, what happens to a reaction?
Reaction:
- releases energy
- is exergonic/catabolic
- thermodynamically favourable
- Can proceed in absence of energy -spontaneous
When ∆G is +ve, what happens to a reaction?
Reaction:
- Requires energy
- is endergonic/anabolic
- thermodynamically unfavourable
- Energy must be supplied
When ∆G is = to 0, what happens to a reaction?
Reaction is at equilibrium
What are the condition standards that accompany the standard free energy change (∆G˚)?
T=298K/25˚C
Pressure = 1 atmosphere
[] of reactants & products = 1M
Please remind yourself of the Keq equation and did you know this is related the free energy change?!
How are they related? *hint use an equation
Keq = [C] [D]/ [A] [B]
products/reactants
-Related because ∆G˚ = -RT In Keq
R=gas constant 8.315 J/mol. K
T=absolute temp (K)
When Keq is
>1.0
1.0
<1.0
What is ∆G’˚?
>1.0 = -ve
1.0 = zero
<1.0= +ve
Which determines the direction of a reaction, ∆G (free energy) ∆G˚ (STD FE)?
∆G
