Energy Balances in Cells and Organisms Flashcards
What is the first law of thermodynamics (regarding energy)?
- the total energy within a system is constant
- energy cannot be created or destroyed
- energy can be converted between forms
Biochemistry relies on energy conversions
- pathways for processing fuel molecules for ATP synthesis concentrate on relations involving energy conversions
Describe the energy conversion pathway in biology
Sun:
- releases energy as photons
Plants:
- take up the energy from the sun for photosynthesis to make bigger molecules
Bigger molecules:
- energy is now stored in chemical bonds (anabolism)
- we (animals) eat these plants in out diet
Animals:
- break molecules down (catabolism)
- releases energy from chemical bonds
Energy is used to do cellular work:
- anabolism (protein synthesis)
- movement
- signalling pathway
CO2 and H2O produced?? and go back into plants to continue the cycle
describe adenosine triphosphate (ATP)
It is the major energy intermediate (currency) of the cell
- the phosphoanhydride bonds between phosphates in ATP are very high energy bonds
Hydrolysis:
- reaction where a chemical bond is broken using water
- water molecule is consumed in the separation of a larger molecules into smaller parts
Chain of reactions (top to bottom):
- Fuel molecules (from diet) and O2 synthesise ATP (catabolism - oxidative, exergonic) with ADP and P to produce ATP, CO2 an H2O
- ATP and precursors then do ATP hydrolysis (anabolism - reductivetive, endergonic) to produce products of anabolism (for cellular work) and ADP+P
(once we make ADP we need to find a phosphate and put it back on, we do this by taking the energy in the things we have eaten)
Describe what macronutrients are, and what they are used for in the body
- consumed in food
- large molecules: polymers
eg. carbohydrates, proteins, fats, nucleic acids.
Digestion involves:
1. hydrolysis of bonds connecting monomer units
2. absorption from gastrointestinal tract into body
Monomers used in body for:
- Anabolism - making bigger molecules (not the focus of these lectures)
- catabolism (fuel molecules) - breaking molecules down and energy conversion into ATP
Describe what minerals are and what their two groupings are
- inorganic elements in the diet (don’t have carbon in them)
- two groups: major (macro) and minor (trace)
Major:
- greater abundance in the body
- range of functions
eg Mg as a cofactor, P in ATP
Minor:
- initially termed trace as concentration so low difficult to identify/measure
eg. Fe in haem and cytochrome C
what are vitamins and their two classifications?
- organic substances usually essential in diet
- not related chemically, different roles
Classified as:
- water soluble - not stored, B class in metabolism
- fat soluble - can be stored
what are cofactors and coenzymes and what do they do?
Minerals and vitamins are often cofactors
- small molecules required for the activity of an associated enzyme
- range of mechanisms
Coenzyme:
- type of cofactor
- organic, often derived from vitamins
- key coenzymes: NAD, FAD, CoA
Key features of coenzymes in the pathways:
- low concentration in cells
- act as carriers (transfer things)
- have two forms
describe what the different Gibbs free energy values mean
The delta G of a reaction tells us about the energy stores in the chemical bonds of the products and substrates
delta G < 0 for A to B:
- reaction is spontaneous/energetically favourable/more energy stored in the bonds of A/energy released
delta G = 0 for A to B:
- reaction is at equilibrium/similar energy in A and B/no change in the energy
delta G > 0 for A to B:
- reaction is not spontaneous/energetically unfavourable/more energy stored in the bonds of B/energy required (and enzyme cannot make this happen)
what do the different delta G symbols mean?
delta G = specific conditions
- using this is hard because of all the conditions you have to have
delta G* = standard conditions (all reactants are at 1M and pH is 0 (because H+ conc. also have to be 1M))
delta G*’ = standard conditions but pH = 7
pathways for processing fuel molecules for ATP synthesis concentrate on reactions involving energy conversions. what are the two types of reactions?
- those involving ADP and ATP
- redox reactions: fuel molecules get oxidised
describe redox reactions and how these work in relation to fuel molecules
energy is released from fuel molecules by oxidation reactions (they release a lot of energy when oxidised)
Redox involves the transfer of electrons
OIL - oxidation is loss of an electron
- so it is the reducing agent and provides a reducing power
RIG - reduction is gain of an electron
- so it is the oxidising agent and provides and oxidising power
what are reducing equivalents?
biological redox reactions often involve the transfer of hydrogen (H) atoms (includes electron)
H = H+ + e-
- Hydrogen referred to as a reducing equivalent (it is the equivalent of moving an election, we just have an H+ coming along too)
- The enzymes that catalyse these reactions are often called dehydrogenases
how does oxidation of fuel molecules occur in pathways?
It happens stepwise so that it is slowly breaking down. we do this by linking the oxidation reactions to other things, allowing us to capture energy and use it to make ATP.
- if we did it all at once all the energy would be released as heat (not ATP)
