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
- Will proceed spontaneously from L to R
- None of the above
- B formation is kinetically slow; equilibrium has not been reached by 24 hours
**hard Q practice this!!
- ∆G’˚ is -4.44kJ/mol
Describe energy coupling in chemical processes
- Cells obtain e from oxidising reduced fuels
- In combustion all E is released as heat, which is not in useable form. Cells need free e
- Cells overcome this by oxidising glucose in many steps, trapping released e in sml, useable forms
- (glycolysis)
What is the common energy store for cells?
see slides for extra notes 46 & 47
ATP
Adenosine Tri Phosphate
-usually complexed w/ Mg2+ which is the active form
Useable e stored in phosphoanhydride bonds
-anhydride is an acid condensation
Phosphoryl Group Transfers & ATP
Standard free energy change of ATP is in middle.
What are the 2 important consequences?
- Compounds above ATP in table have a higher tendency to transfer phosphate to ADP to form ATP
- forms basis for substrate level phosphorylation (one molecule leads the phosphorylation of another) - ATP can donate its phosphate to compounds w/ a lower ∆G˚, overcoming equilibria which would otherwise be unfavourable
Describe REDOX reactions
See sl 60
- Involve transfer of electrons
- One molecule loses electrons (oxidised) -releases energy
- One molecule gains electrons (reduced) -incorporates energy
- OILRIG (Oxidation Is Loss, Reduction Is Gain)
Transfer of electrons can occur:
- directly as electrons
- As H or O atoms
- Oxidation: loss of H on C; gain of O atoms on C
- Reduction: gain of H on C; loss of O on C
What is reduction potential? What is the equation used to measure energy made available from these reactions?
Reduction potential (E) is a measure of a reducing agents affinity for electrons
∆G = -nF ∆E
Where n= number of electrons transferred
F= Faraday constant (96 480 J/V.mol)
+ve E (reduc. potent.) =?
Gives rise to -ve ∆G
strong tendency to accept electrons and become reduced
-ve E (reduc. potent.)=?
strong tendency to lose electrons and become oxidised
