BIOCH Y1 S1: Cellular Energetics

Question 1

metabolism

Answer 1

sum total of all chemical reactions re: energy production and utilisation

Question 2

2 types of metabolism

Answer 2

• anabolism: use small molecules to synthesise big molecules, requires energy stored in chemical bonds
• catabolism: break down complex molecules to release energy stored in chemical bonds

Question 3

first and second laws of thermodynamics

Answer 3

• 1) energy is neither created nor destroyed
• 2) energy conversion results in some energy being “lost” or unable to do work (entropy)

Question 4

ΔG signs

Answer 4

• if ΔG is +ve: energy is released (exergonic - generate disorder)
• if ΔG is +ve: energy is required (endergonic - generate order)
• if ΔG is 0: reaction is @ equilibrium so [reactants] and [products] determine which reaction will be favoured

Question 5

ATP cycle

Answer 5

• ATP hydrolysed into ADP + Pi > release chemical energy to power endergonic reactions
• exergonic reactions occur, producing energy which is used to convert ADP + Pi back into ATP

Question 6

primary structure of a protein

Answer 6

• sequence of amino acids in a polypeptide chain, held together by peptide bonds

Question 7

secondary structure of a protein

Answer 7

• folding of primary structures into alpha helices or beta pleated sheets
• held together by H bonds

Question 8

tertiary structure of a protein

Answer 8

• 3D structure composed of folded secondary structures (one polypeptide chain)
• hydrogen, ionic, disulfide bridges

Question 9

quaternary structure of a protein

Answer 9

• 2 or more polypeptide chains joined together

Question 10

structure and function of an enzyme

Answer 10

• S = protein w/ a S&C (in S/C) active site
• F = speeds up rate of a chemical reaction by lowering activation energy, unchanged in process

Question 11

factors that affect rate of reaction

Answer 11

• catalyst
• temp
• SA
• pressure
• substrate concentration: after saturation point, all active sites have been used up

Question 12

3 types of other molecules needed by enzymes to function

Answer 12

• inorganic co-factors: metal ion e.g. Mg2+ that changes shape of enzyme by binding to non-active site (permanently bound)
• organic coenzymes: bind to active site w/ substrate, add or remove chemical groups e.g. H+ or e-, changed by reaction (not permanently bound)
• inorganic prosthetic groups: bound permanently to enzyme

Question 13

2 ways that enzyme activity is regulated

Answer 13

• inhibit expression of gene that codes for the enzyme protein
• use inhibitors to regulate enzyme activity

Question 14

irreversible inhibition

Answer 14

• inhibitor binds to site near the active site, preventing substrate from binding and hence formation of products

Question 15

3 types of reversible inhibition

Answer 15

• competitive: inhibitor w/ similar shape binds to active site, blocking substrate (can be reversed by adding more substrate)
• uncompetitive: inhibitor binds to E/S complex, preventing formation of products
• non-competitive: inhibitor binds to allosteric site and causes active site to change shape > no longer S/C to substrate > can’t bind

Question 16

feedback inhibition (end product inhibition)

Answer 16

• when there is too much of a product or it isn’t needed anymore so an earlier step in the pathway is inhibited
• end product binds to allosteric site and acts non-competitively

Question 17

unusual property of water

Answer 17

• H bonds continually form and break
• this allows for high surface tension and high specific heat capacity

Question 18

difference between starch and glycogen

Answer 18

• starch = moderately branched
• glycogen = highly branched