Proteins

Question 1

What is the step called which copies a genes DNA sequence to make an RNA molecule?

Answer 1

Transcription

Question 2

What is the step called whereby an RNA molecule is coded into a protein?

Answer 2

Translation

Question 3

What is an amino acid made up of?

Answer 3

An amino group, a carboxylic acid group and a side chain

Question 4

What is primary protein structure?

Answer 4

The sequence of amino acids in a polypeptide chain

Question 5

Where and when do peptide bonds form?

Answer 5

Within a ribosome during translation

Question 6

What is secondary protein structure?

Answer 6

The spatial arrangement of amino acid residues that are near each other in the linear sequence

Question 7

Where are examples of secondary structure found?

Answer 7

Alpha helices (in myoglobin/ferritin) and beta pleated sheets (fatty acid binding protein/porin)

Question 8

What is the beta pleated sheet held together by?

Answer 8

Hydrogen bonds between amid groups of linear polypeptide chains

Question 9

What is tertiary protein structure?

Answer 9

The spatial arrangement of amino acid residues that are far apart in a linear sequence

Question 10

What kind of forces can hold amino acids together in the tertiary structure?

Answer 10

van der Waals, ionic interactions, hydrogen bonds, disulphide bridges, hydrophobic interactions

Question 11

Where do ionic interactions occur?

Answer 11

Occur between two close oppositely charged R groups, are strong

Question 12

What are Van der Waals forces?

Answer 12

Non-specific, weak attractions between atoms, strong when large no of them exist

Question 13

When do hydrogen bonds occur?

Answer 13

When H is bonded to either O, N or F and a lone pair of electrons are present

Question 14

What is the difference between Van der Waals and hydrogen bonds?

Answer 14

Hydrogen bonds are stronger and permanent

Question 15

What are hydrophobic interactions?

Answer 15

Intra-polypeptide interactions which occur in an environment within proteins from which water is excluded

Question 16

What are disulphide bridges?

Answer 16

Strong covalent bonds between two cysteine residues

Question 17

When can disulphide bonds occur?

Answer 17

Common in extra-cellular proteins and can occur between, as well as, within a polypeptide

Question 18

What is quarternary protein structure?

Answer 18

The spatial arrangement of individual polypeptide chains in a multi-subunit protein

Question 19

What structures are disruption or destroyed during protein denaturation?

Answer 19

Both secondary and teritary structures

Question 20

Why does the primary structure remain the same after a denaturation process?

Answer 20

Denaturation reactions not strong enough to break peptide bonds

Question 21

What are some causes of denaturation of proteins?

Answer 21

Acids, heat, solvents

Question 22

What are the effects of denaturation?

Answer 22

Decreased solubility, altered water binding capacity, loss of biological activity, improved digestibility

Question 23

What enzymes cleave peptide bonds?

Answer 23

Peptidases

Question 24

What enzymes cleave internal bonds?

Answer 24

Endopeptidases

Question 25

What enzymes cleave one amino acid at a time?

Answer 25

Exopeptidases

Question 26

What enzymes cleave from the -COOH terminal?

Answer 26

Carboxypeptidases

Question 27

What enzymes cleave from the -NH2 terminal?

Answer 27

Aminopeptidases

Question 28

What are glycoproteins composed of?

Answer 28

Protein and carbohydrate

Question 29

What is an example of a glycoprotein?

Answer 29

Immunoglobulins

Question 30

Where does glycosylation occur?

Answer 30

In the ER and Golgi apparatus

Question 31

What does glycosylation have roles in?

Answer 31

Protein stabilisation, affects solublity, protein orientation, signalling and cell recognition

Question 32

How are glycoproteins formed?

Answer 32

Glycosylation whereby sugar molecule binds via amino acid to the protein

Question 33

What are lipoproteins?

Answer 33

Protein and lipids which are either covalently or non-covalently bonded together

Question 34

What is the function of lipoproteins?

Answer 34

Transport of water-insoluble fats and cholesterol in the body

Question 35

What is a metalloprotein?

Answer 35

A protein molecule with a bound metal ion

Question 36

What functions can a metalloprotein help with?

Answer 36

Enzymes, storage, signalling, transport

Question 37

How does haemoglobin transport O2?

Answer 37

Haem group at centre of each polypeptide chain binds one molecule of oxygen

Question 38

How many molecules of oxygen can one haemoglobin molecule bind?

Answer 38

Four

Question 39

What kind of binding means that a haemoglobin molecules takes not one, but four oxygens?

Answer 39

Co-operative binding

Question 40

Why does scurvy happen in relation to collagen?

Answer 40

Vitamin C needd to convert proline to hydroxyproline which is essential for stabilising crosslinks between chains and so a weaker collagen is produced

Question 41

What structures are lost with osteogenesis imperfecta?

Answer 41

Secondary and tertiary structures

Question 42

Why is a weaker and brittle collagen produced with osteogenesis imperfecta?

Answer 42

Glycine substituted, protein can no longer fold to form tight coil, reduced interacton between fibrils, loss of structure

Question 43

What happens when LDL receptor mutation?

Answer 43

Different possible effectors: no receptors, receptors can't bind LDL, receptors don't release LDL

Question 44

What kind of genetic disorder is Familial Hypercholesterolemia?

Answer 44

Autosomal dominant

Question 45

What causes Familial Hypercholesterolemia?

Answer 45

Mutation in LDL receptor gene meaning elevated LDL conc in blood

Question 46

What are effects of Familial Hypercholesterolemia?

Answer 46

Cholesterol deposition in skin, tendons and arteries and a risk of early CVD