metabolism Flashcards
what is metabolism?
- the sum of chemical reactions occurring in a living organism
describe what all reactions are and what they are governed by
- reversible reactions
- governed by principle of mass conservation
- some can be complex but often form linked pathways
what do metabolic pathways involved and what do they do?
- involve a number of different metabolites that undergo reactions in order to derive each other
e.g., glycolysis
what is thermodynamics?
- study of the flow of energy changes in chemical systems
what is bioenergetics?
- study of energy changes in living organisms
how do chemical reactions take place in cells?
- take place between products and reactants with different energy content
free energy change equation
change in FE = enthalpy - (temp x entropy)
G= H- (T x S)
what are the units of change in free energy?
- kcal
what is enthalpy?
- amount of bond energies in either product or reactants
- directly related to energy required to break bonds
what bonds are harder to break and what is the energy influenced by?
- double and triple bonds are harder to break
- influenced by amount of free energy available/ consuming
what is entropy?
- appreciation of disorder or randomness
- increases when disorder increases
what does the second law of thermodynamics state?
- state of entropy of an isolated system will always increase over time
are reactions isolated? what does this do to the entropy?
- many aren’t isolated so increase in order and hence decreases entropy
e.g. reaction that links amino acids to form proteins
what solution has a lower entropy; proteins or unlinked amino acids?
- solution of proteins have a lower entropy (more order) than a solution of unlinked amino acids
what must happen for the linking reaction to proceed?
- compensatory decrease in free energy must occur elsewhere in the system
- in a linked reaction
what factors influence change in free energy?
- temperature, pressure, initial amounts of products+ reactants, pH
what is the standard free energy change of reaction delta G nought prime?
- value of the change of free energy in standard conditions
- 25 degrees, 1atm pressure, pH 7
describe the free energy change in biochemical reactions where there is a different temperature and initial concentration
- G= G ‘ + RT InQ = G’ + RT In products/ reactants
- R= gas constant
- Q = initial ratio of products to reactants
what is an exergonic reaction?
- free energy of products is lower than the reactants <0
- favoured thermodynamically> energy released for work
what is an endergonic reaction?
- free energy of products is higher than the reactants <0
- unfavoured as energy consumed
describe equilibrium
- free energy = 0
- dynamic state whereby energy of products and reactants is equal
can expression of free energy be useful?
- yes because comparison of free energy changes between different reactions provides context
e.g., free energy derived from different biomolecules
what is 1kcal?
- amount of energy required to raise the temperature of one kilogram of water by 1 degree
in the case of exergonic reactions what does G nought tell us?
- how much energy is available for work
what is the main source of energy? describe its structure
- adenosine trisphosphate
- ribose linked to an adenine and three phosphoryl groups (alpha, beta+ gamma)
what does hydrolyse of ATP create and what is important?
- phosphoryl group is removed to form adenosine diphosphate
- hydrolysed twice to form adenosine monophosphate
- bond energy of phosphate bonds is important in providing energy
what is the equation of ATP hydrolysis ?
ATP + H20 –> ADP + Pi + H+
what is the standard free energy change of ATP hydrolysis and what does this show?
- ATP + 2h20 - AMP+ 2Pi+ H+ = -12kcal. mol -1 (very negative)
- favoured thermodynamically so ATP referred to as a high energy compound
what is catabolism
- series of reactions that break down biomolecules into smaller molecules
why is the synthesis of ATP linked to catabolic reactions?
- because synthesis of ATP is endergonic so unfavoured
- linkage allows it to proceed as its manipulated to a favourable reaction
what is anabolism? what is it needed for?
- formation of structures needed for growth, cell division, energy storage
what does synthesis require and what type of reaction is it?
- synthesis requires energy so it is endergonic and hence unfavoured
- more ATP hydrolysis needed
describe redox reactions
- oxidation= compound gains H and loses 02
- reduction= compound loses H and gains 02
- constant equilibrium
what is oxidation usually involved in?
- breakdown of large molecules
what is reduction usually involved in?
- generation of large molecules
how do oxidation and reduction work?
- work in constant equilibrium as no atoms are lost or gained
- when one substance is reduced another is oxidised
describe NAD
- exists in oxidised and reduced forms
- oxidised form NAD+ accepts H from an oxidising metabolite forming NADH (reduced form)
what does NAD do and how is it formed?
- works to lend and receive hydrogen atoms
- AMP plus nicotinamide mononucleotide derived from vitamin Niacin
what other redox compounds assist hydrogen transactions?
- nicotinamide adenine dinucleotide phosphate (NADP +/ NADPH)
- flavin adenine dinucleotide (FA
what does the transfer of electrons from NADH and FADH2 to 02 mean?
- marks the end of oxidation of metabolites within cells
- creating water
how many atoms do NAD and FAD receive?
- FAD receives 2; NAD receives 3
what compounds serve as oxidants?
- NAD+, NADP+ and FAD
- accept H from metabolites
what compounds serve as reductants?
- NADH, NADPH and FADH2
- donate H (or more precisely, electrons)
