1.2 proteins

Question 1

define proteome

Answer 1

the entire of of proteins that can be expressed by a genome

Question 2

why the proteome is larger than the genome

Answer 2

more than one protein can be produced from a single gene as a result of alternative RNA splicing

Question 3

alternative RNA splicing

Answer 3

one gene can produce different proteins as a result of which segments are treated as introns or exons

Question 4

non-coding RNA genes

Answer 4

genes that don’t code for proteins
are transcribed to produce tRNA, rRNA or RNA molecules that control gene expression

Question 5

factors that influence gene expression (4)

Answer 5

metabolic activity
cellular stress
signalling molecules
healthy vs diseased cells

Question 6

internal membranes in eukaryotic cells

Answer 6

increase the total membrane surface area
allows for vital functions to be carried out

Question 7

endoplasmic reticulum

Answer 7

forms a network of membrane tubules continuous with the nuclear membrane
smooth = lacks ribosomes
rough = ribosomes are docked on its cytosolic face

Question 8

golgi apparatus

Answer 8

a series of flattened membrane discs

Question 9

lysosomes

Answer 9

membrane-bound organelle containing digestive hydrolases

Question 10

vesicles

Answer 10

transport materials between membrane compartments

Question 11

synthesis of lipids

Answer 11

synthesised in smooth endoplasmic reticulum and are inserted into its membrane

Question 12

synthesis of cytosolic proteins

Answer 12

synthesised in cytosolic ribosomes and remain in the cytosol

Question 13

define signal sequence

Answer 13

a short stretch of amino acids that determines the eventual location of a protein in a cell

Question 14

synthesis of transmembrane proteins

Answer 14

synthesis begins in cytosolic ribosomes
signal sequence directs ribosome to dock on endoplasmic reticulum (forms rough er)
translation continues
transmembrane protein is inserted into the er membrane

Question 15

movement of vesicles

Answer 15

vesicles containing proteins bud of from er
fusion with golgi apparatus
bud off from one golgi disc and fuse with the next in the stack

Question 16

post-translational modifications

Answer 16

proteins undergo as they move through golgi apparatus
addition of carbohydrates to form glycoproteins

Question 17

vesicles that leave golgi apparatus

Answer 17

take proteins to plasma membrane and lysosomes
move along microtubules to other membranes and fuse with them

Question 18

synthesis of secreted proteins

Answer 18

translated in ribosomes on rough er and enter its lumen

Question 19

secretory pathway

Answer 19

proteins move through golgi apparatus and are packaged into secretory vesicles
fusion with plasma membrane and are released out of the cell

Question 20

proteolytic cleavage

Answer 20

a type of post-translational modification
can produce active proteins from inactive precursors

Question 21

amino acids

Answer 21

amine group and carboxyl group
formed by condensation reactions
linked by peptide bonds

Question 22

purpose of R groups

Answer 22

determine the protein’s position in the cell and overall conformation

Question 23

acidic R group

Answer 23

second carboxyl group
negatively charged
form ionic bonds
hydrophilic

Question 24

basic R group

Answer 24

second amine group
positively charged
form ionic bonds
hydrophilic

Question 25

polar R group

Answer 25

hydroxyl group
overall neutral
form hydrogen bonds
hydrophilic

Question 26

non-polar R group

Answer 26

attracts only other non-polar R groups
hydrophobic

Question 27

factors affecting R groups

Answer 27

temperature and pH disrupt interactions between R groups

Question 28

primary structure

Answer 28

sequence of amino acids along a polypeptide chain

Question 29

secondary structure

Answer 29

form due to hydrogen bonds
alpha helix, beta-pleated sheets, beta turns

Question 30

tertiary structure

Answer 30

form due to interactions between R groups
London dispersion forces, hydrophobic interactions, ionic bonds, hydrogen bonds, disulphide bridges

Question 31

quaternary structure

Answer 31

occurs in proteins with multiple polypeptide subunits
linked by interactions between R groups of adjacent subunits

Question 32

prosthetic groups

Answer 32

non-protein units tightly bound to a protein
essential for the protein’s function

Question 33

define ligand

Answer 33

non-protein substance which binds to a protein and alters its conformation and function

Question 34

allosteric interactions

Answer 34

occur between spatially distinct sites
ligand binding on one site increases affinity of other sites

Question 35

co-operativity

Answer 35

shown in allosteric proteins of quaternary structure
changes at one subunit alters the affinity at remaining subunits

Question 36

factors affecting oxygen affinity in haemoglobin

Answer 36

decrease in pH/ increase in temperature lowers oxygen affinity, so more oxygen is released

Question 37

allosteric enzymes

Answer 37

have secondary allosteric sites for modulator binding

Question 38

types of modulators

Answer 38

positive = increase affinity
negative = decrease affinity

Question 39

protein kinase

Answer 39

catalyse the phosphorylation of proteins

Question 40

protein phosphatase

Answer 40

catalyse the dephosphorylation of proteins