1.2

Question 1

signal sequence

Answer 1

short stretch of amino acids at one end of a polypeptide which determines the eventual location

Question 2

amino acid groups

Answer 2

• non-polar, hydrophobic, CH3 and CH2
• polar, hydrophilic, Oxygen Nitrogen and sulfur on R group.
• acidic, negative charge, COOH on R group
  basic, positive charge, NH2 on R group

Question 3

primary structure

Answer 3

sequence in which amino acids are synthesised into a polypeptide

Question 4

secondary structure

Answer 4

hydrogen bonding along the backbone of the strand; alpha helices, parallel and anti-parallel beta-pleated sheets, or turns

Question 5

tertiary structure

Answer 5

formed by interactions between R groups:
- hydrophobic interaction
- ionic bonds
- LDF
- hydrogen bonds
- disulfide bridges

Question 6

quaternary structure

Answer 6

exists in proteins with 2 or more connected polypeptide subunits

Question 7

prosthetic group

Answer 7

a non-protein unit tightly bound to a protein and necessary for it’s function

Question 8

ligand

Answer 8

a substance that can bind to a protein

Question 9

proteome

Answer 9

the entire set of proteins expressed by a genome
the proteome is larger than the number of genes particularly in eukaryotes, because more than one protein can be produced from a single gene as a result of alternative RNA splicing

Question 10

transmembrane proteins

Answer 10

they carry a signal sequence which is a short stretch of amino acids t the end of a polypeptide which will determine the eventual location of a protein in a cell
this halts translation and directs the ribosome synthesising the protein to dock with the ER forming the RER
translation continues after docking and the protein is inserted into the membrane of the ER

Question 11

movements of proteins between intracellular membranes

Answer 11

when proteins in the ER they are transported by vesicles that bud off from the ER and fuse with the GA
as proteins move through the GA they undergo post-translational modification
vesicles that leave the GA take proteins to the plasma membrane and lysosomes
vesicles move along microtubules to other membranes and fuse with them within cells

Question 12

Secretory pathways

Answer 12

secreted proteins are translated in ribosomes on the RER and enter it’s lumen
the proteins move through the GA and are packaged into secretory vesicles
these vesicles move to and fuse with the plasma membrane releasing proteins out of the cell

many secreted proteins are synthesised as inactive precursors and require proteolytic cleavage to produce active proteins

Question 13

temp influence on the R-groups

Answer 13

increase in temp disrupts interactions that hold the protein in shape, the protein begins to unfold eventually becoming denatured

Question 14

pH influence on the R-group

Answer 14

as pH increases or decreases from the optimum the normal ionic interactions between charged groups are lost, which gradually changes of the protein until it becomes denatured

Question 15

ligand

Answer 15

a substance that can bind to a protein

Question 16

modulator

Answer 16

regulate the activity if the enzyme when they bind to the allosteric site

Question 17

positive modulator

Answer 17

increase the enzyme’s affinity for the substarte

Question 18

negative modulator

Answer 18

reduce the enzyme’s affinity for the substrate

Question 19

co-operativity

Answer 19

when the finding of a substrate to the first subunit affects the affinity of remaining subunits

Question 20

cooperativity of haemoglobin

Answer 20

shown through the binding of oxygen to the first subunit which increases affinity of further subunits