biochemistry

Question 1

what is the difference between osmolarity and tonicity?

Answer 1

osmolarity is the number of particles in a solution measured in osm/l whilst tonicity considers both the osmolarity of a solution and the osmolarity of the cell

Question 2

what is the difference between primary and secondary active transport?

Answer 2

primary active transport uses energy from ATP e.g. proton pump in the stomach, whilst secondary active transport uses energy from the concentration gradient e.g. the movement of glucose and amino acids into the intestine

Question 3

what is the equilibrium potential ?

Answer 3

where the ions chemical driving force (difference in solute concentration) in one direction = the electrical force (charge difference) in the other direction

Question 4

what is the resting potential?

Answer 4

the difference in electrical potential between the interior and exterior of cell due to large molecules, pumps and channels creating an ion imbalance

Question 5

what is the main composition of the intracellular fluid?

Answer 5

low sodium, high potassium, very low calcium and chloride ions

Question 6

what is the main composition of the extracellular fluid?

Answer 6

high sodium, low potassium, low calcium and chloride

Question 7

what are the different types of amino acid?

Answer 7

electrically charged side chain, uncharged side chain, hydrophobic side chain, and some special cases

Question 8

what are the features of globular proteins? and two examples

Answer 8

compact and usually soluble e.g. enzymes and antibodies

Question 9

what are the features of fibrous proteins? and 3 examples

Answer 9

multiple strands held together by strong bonding

e.g. collagen, keratin, fibroin

Question 10

what are the features of membrane proteins? and 2 examples

Answer 10

hydrophobic regions which sit in the cell membrane e.g. channels and receptors

Question 11

what causes hyperelastic skin?

Answer 11

defect in enzyme procollagen N- proteinase –> malformed fibrils in collagen

Question 12

what is a prion? and give two examples

Answer 12

an infectious protein e.g. BSE, Scrapie

Question 13

How do enzymes decrease activation energy?

Answer 13

bring substrates together, excluding water stabilising transition state, transfer chemical groups

Question 14

how do isoteric enzymes work?

Answer 14

the rate increases with substrate until enzyme is saturated

Question 15

how do allosteric enzymes work?

Answer 15

substrate/ effectors induce a change in the enzyme shape which increases activity - rate increases in a sigmoidal curve

Question 16

what are the 3 types of allosteric inhibitors?

Answer 16

competitive, non competitive ( bind to allosteric site), uncompetitive (bind to E/S complex)

Question 17

list 5 factors which affect enzyme activity

Answer 17

temperature, pH, concentration, post transnational modification e.g. phosphorylation, cofactors

Question 18

what is a proteinase? and how are they named?

Answer 18

an enzyme which cleaves proteins, they are named after the amino acid at their active site e.g. cysteine proteinase

Question 19

what is a multisubunit enzyme?

Answer 19

an enzyme with different forms which can catalyse the same reaction

Question 20

what is a multienzyme complex?

Answer 20

an aggregation of several enzymes into a single functional unit