Introduction to Metabolism Flashcards
What is metabolism?
Means by which organisms extract energy from their environment and use this to synthesize large molecules
Why is metabolism clinically important in regards to health?
Good health is absolutely dependent on well-balanced metabolism
Why is it clinically important to know about metabolism?
Many disorders involve changes in the balance of metabolic activities
E.g. Diabetes, obesity or vitamin deficiencies
Many clinical biochemical tests are designed to investigate aspects of metabolic function
Understanding the molecular mechanisms underlying these conditions is essential
What is the oxygen requirement of a resting human?
approx ml 350 O2/min
1.75 litres/ 5 mins
By what factor does oxygen consumption increase when a person is exercising?
Up to roughly 5x
What is oxygen used for?
To oxidize substrates and produce energy for the bodys needs
Define oxidation and reduction
Oxidation = Addition of oxygen to molecules
-Can also be considered as removal of electrons from molecules
Reduction = removal of oxygen from molecules -Can also be considered as addition of electrons
Define anabolism and catabolism
Anabolism: Process by which large molecules are built from smaller ones
-Requires an energy input
Catabolism: Breakdown of large molecules to smaller ones -Releases energy
What is DeltaG
Chemical reactions either absorb or release energy
This is expressed as the change in free energy = DeltaG
How does one figure out DeltaG?
For the reaction A + B C + D
DeltaG = DeltaGo + RT loge ([C][D])/([A][B])
Where
DeltaG = Free energy change for the reaction with reactants at the concentrations given
DeltaGo = Standard free energy change (when all reactants are present at a concentration of 1.0 M)
R = Gas constant
T = Absolute temperature
When can a reaction occur spontaneously(without energy input)?
if the free energy change (DeltaG) is negative
What determines the reaction rate of a spontaneous reaction?
Free energy of activation
The reaction rate depends on the energy hump that must be climbed for the reaction to occur. This is called the free energy of activation (DeltaG*) which is unrelated to DeltaG
What is normally involved between the substrate and the product in a reaction?
An intermediate (transitional) state
What may increase the reaction rate?
A catalyst amongst other things
How might a spontaneous reaction take place with a positive deltaG?
coupled reactions can take place without energy input as long as there is a overall negative change in free energy (DeltaG) between the starting materials and the final product(s) of the reaction sequence.
What is the purpose of ATP in metabolism
To allow energy-requiring processes to occur, the energy released during catabolism needs to be captured and stored in a form that is usable
ATP is that form (= currency)
What is ATP?
Inorganic phosphate = PO>4^3- =Pi Phosphate groups (PO>4^3-) are sometimes shown as –P just to make structures look simpler (e.g. glucose-6-P)
What is phosphorylation?
Phosphorylation (phosphorylate) = adding a phosphate group to a molecule (e.g. converting ADP to ATP)
Discuss the high energy bonds of ATP
A large amount of energy is released when ATP is hydrolysed to ADP + inorganic phosphate (Pi)
= approx -7 to -12 kcal/mol
Hydrolysis of ATP is used to drive energy-requiring processes (e.g. anabolism, movement and ion transport)
What is the ATP turnover in a resting human and a human partaking in strenuous exercise?
Resting human consumes approx 50 kg (approx 110lb = 71⁄2 stone) of ATP in 24 hrs (approx 175 g/5 mins)
-In strenuous exercise can be as much as 0.5 kg/min (2.5 kg/5 mins)
What is ATP used for in the body? (other than for phosphorylation)
- Body movement (via muscular contraction)
- Neuronal activity (CNS & peripheral nerve activity)
- Cellular movements (via cytoskeleton)
- Active transport
- Synthesis of large molecules
What process generates ATP?
The citric acid (krebbs) cycle and anaerobic respiration
How can regulation of the metabolism be achieved?
- Changes in amounts of substrates and products of pathways (e.g. ratio of ATP to ADP + Pi affects energy producing and energy-requiring pathways in opposite ways)
- Changes in amounts of key enzymes
- Changes in activity of key enzymes
What changes in activity of key enzymes might help bring about the regulation of the metabolism?
- Allosteric changes
- Effects of substrate and downstream products on enzyme activity
- Covalent modification of enzymes (e.g. phosphorylation)
What are some hormones that have a major regulatory effect on some enzymes?
insulin, glucagon and adrenaline
When is ATP formed?
ATP is formed when fuel molecules are oxidized
What molecules are interconvertible with ATP?
ATP, ADP and AMP are interconvertible under appropriate conditions
What molecules may serve a similar role to ATP?
In some cases other nucleotides such as guanosine diphosphate (GDP) and guanosine triphosphate (GTP) can serve a similar role to those of ADP and ATP
