Johnson - Intro to metabolism

Question 1

name the 3 laws of thermodynamics

Answer 1

1) energy can never be created or destroyed
2) the entropy of the universe always increases
3) the entropy of a perfect crystal of any element of compound is zero at absolute zero

Question 2

what is anabolism and catabolism? state whether they are usually exergonic or endergonic

Answer 2

anabolism: making stuff (anabolic steroids - muscle BUILDING) - usually endergonic
catabolism: breaking stuff - usually exergonic

Question 3

name 3 methods of cellular organisation that help a cell metabolise

Answer 3

1) physically separate soluble enzymes with diffusing intermediates
2) a multienzyme complex ‘metabolon’ with substrates channelled between them sequentially before release
3) membrane bound multi-enzyme systems
these can be in organelles/protein compartments

Question 4

are C-H bonds more or less stable than C-O and C=O bonds?

Answer 4

C-H bonds are less stable than C-O and C=O bonds

Question 5

how is ATP used as a cofactor?

Answer 5

the excess of ATP is required to get energy (so it held away from equilibrium)
ATP hydrolysis releases free energy and is coupled to reactions that require free energy to happen

Question 6

how is NAD(P) used as a cofactor?

Answer 6

the energy derived from C oxidation or sunlight can drive the energetically unfavourable formation of NADH from NAD+ +2e- +H+.
the reverse reaction yields energy which can be harnessed to do useful work

Question 7

generally is NADPH/NADH used for catabolism/anabolism

Answer 7

NADPH = anabolism
NADH = catabolism

Question 8

describe the property of cofactors that make them kinetically stable

Answer 8

react slowly with oxygen/water (have a large free energy of activation barrier in absence of enzymatic catalyst