Intro To Metabolism Flashcards
How much oxygen is consumed per minute in a resting human?
350 ml
How much can a human’s consumption of oxygen be increased per minute during exercise?
X5
Why is oxygen required in humans?
To oxidise substrates - produces energy for body’s needs
Definition of oxidation:
Addition of oxygen
Removal of electrons (and H+ ions)
Definition of reduction:
Removal of oxygen
Addition of electrons (and H+ ions)
What two limbs are involved in metabolism?
Catabolism and anabolism
What is anabolism?
Large molecules built from smaller molecules
Requires energy
What is catabolism?
Larger molecules broken down into smaller molecules
Releases energy
What is energy released by catabolism used for?
To drive anabolism and other energy-requiring processes
What is change in free energy?
When chemical reactions either absorb or release energy
Change in free energy: symbol
ΔG
When is there a change in free energy?
When a metabolite is converted into another
Reaction to find ΔG:
[C][D]
ΔG = ΔG˚ + RT loge ———-
[A][B]
What does ΔG stand for?
Free energy change
Reactants at concentration given
What does ΔG˚ stand for?
Standard free energy change
All reactants at conc. 1 mol
What does R stand for?
Gas constant
What does T stand for?
Absolute temperature
298K
What is ΔG at equilibrium?
0 as gross amount of A,B,C,D unchanged
When is ΔG˚ measured?
When 1 mol of A,B,C,D are added together in standard conditions until equilibrium reached
What happens if A,B,C,D concentrations are different to how they are in equilibrium?
ΔG changes inside cell
What happens if ΔG is negative?
Spontaneous reaction
Reaction moves left -> right
What happens if there is more product in reaction?
ΔG˚ is negative as reaction lies to right - more energy released
When can a reaction only occur spontaneously?
If ΔG is negative
What is meant by a spontaneous reaction?
No energy input
Magnitude of ΔG?
Does NOT indicate rate of reaction
Why doesn’t magnitude of ΔG indicate RofR?
As RofR depends on energy requires for reaction to occur
Free energy of activation
What does ΔG* stand for?
Free energy of activation
Unrelated to ΔG
Difference between ΔG and ΔG*:
ΔG = amount of energy in system that can do work
ΔG* = energy needed for system to move from A+B to C+D
What will a reaction normally involve the formation of?
Intermediate (transitional) state
What’s required for formation of intermediate state?
Energy
Slow RofR as need to get all reactant molecules up to transition state before products are formed
What happens if catalyst is added to reaction?
Fast reaction
Reduces transition state of energy
ΔG* much lower
Why does a catalyst lower transition state of energy?
Provides substrate to allow reactants to come together at lower energy states
When can a sequence of coupled reactions take place without energy input?
When there is an overall negative change in ΔG between starting materials and final products
Coupled sequences: individual reactions with positive free energy change:
Can be driven by those with negative free energy change
Why is ATP formed?
To allow energy-requiring processes to occur
How is ATP formed?
Energy released during catabolism is stored in a usable form
Inorganic phosphate:
PO4(3-)
Or
Pi
What can Phosphate groups sometimes shown as?
-P to make structures look simpler
What’s phosphorylation?
Adding phosphate group to molecules (converts ADP to ATP)
Hydrolysis of ATP:
Broken down into ADP and Pi
Releases energy
Approx. Amount of energy released in hydrolysis of ATP?
-7 to -12 kcal/mol (reaction lies to right)
What are ATP, ADP and AMP like under appropriate conditions?
Interconvertible
What is hydrolysis of ATP used to drive?
Energy-requiring processes
What else can ATP be formed from?
When fuel molecules are oxidised
What nucleotides can serve a similar role to ADP and ATP?
Guanosine diphosphate (GDP) and guanosine triphosphate (GTP)
How much ATP does a resting human consume in 24hrs?
Approx 50kg
What is ATP needed for?
Body movement
Neuronal activity
Cellular movements
Active transport
Synthesis of large molecules
How many stages in ATP generation?
3
Stage 1 of ATP generation?
Fats, polysaccharides and proteins broken down into monomers and absorbed into gut
Stage 2 of ATP generation:
Monomers processed into AcetylCoA - used in citric-acid cycle
Stage 3 of ATP generation:
AcetylCoA broken down in stages
Movement of electrons to oxygen - produces ATP
What can effect activity of key enzymes?
Allosteric changes
Effects of substrate and downstream products
Covalent modification of enzymes (e.g. phosphorylation)
