Protein Structure

Question 1

What is the primary structure?

Answer 1

The sequence of amino acids

Question 2

What kind of bond is present between amino acids?

Answer 2

Peptide bond

Question 3

During a condensation reaction, what molecule is released?

Answer 3

H2O

Question 4

What is the secondary structure?

Answer 4

Folding of polypeptide chains. Determined by primary structure due to polar and non-polar side chain interactions

Question 5

What different shapes are present in secondary structure?

Answer 5

α-helix: H bonding within chain
ß-sheet: interchain H bonds, either parallel or antiparallel
random coil: in-between helix and sheet

Question 6

What is the tertiary structure?

Answer 6

The 3D structure of a protein. The way in which individual secondary elements pack together within a protein

Question 7

What does a common structure indicate?

Answer 7

A common function

Question 8

Why do some proteins have multiple domains?

Answer 8

Multiple complex cellular functions

Question 9

What is the quaternary structure?

Answer 9

Interactions between individual proteins in a multimeric complex

Question 10

Examples of protein modification

Answer 10

glycosylation, phosphorylation, lipid modification, proteolysis, disulphide bridges

Question 11

Disulphide bridges form between…

Answer 11

Cysteine amino acids in proteins

Question 12

What kind of proteins is glycosylation mainly used on?

Answer 12

Extracellular proteins

Question 13

What are lipid modifications in proteins used for?

Answer 13

Binding proteins to membranes

Question 14

Protein phosphorylation/dephosphorylation is mainly used for…

Answer 14

Regulation. Switching on/off

Question 15

4 structural types of transmembrane proteins

Answer 15

Single-pass, multi-pass, ß-barrel, amphipathic helix

Question 16

Single pass type 1 membrane protein?

Answer 16

Protein spanning the membrane once, with its N-terminus on the extracellular side of the membrane and removal of its signal sequence - E.g. T cell surface glycoproteins

Question 17

Single pass type 2 membrane protein?

Answer 17

Protein spanning the membrane once, with its N-terminus on the cytoplasmic side of the membrane - Transmembrane domain located close to N-terminus and it functions as an anchor - E.g. Tumor Necrosis Factor

Question 18

Difference between N-terminus on single pass type 1 and 2 membrane proteins

Answer 18

Type 1 has its N-termins on the extracellular side

Type 2 has its N-termins in the cytoplasmic side

Question 19

What is the N-terminus?

Answer 19

Refers to the start of an amino acid chain. The free amine group -NH2

Question 20

What is the C-terminus?

Answer 20

Refers to the end of a polypeptide chain. The free carboxyl group - COOH

Question 21

What type of lipid modifications bind proteins to cytosolic side of membrane?

Answer 21

Acylation

Question 22

2 types of glycosylation modifications?

Answer 22

• N-linked attachment via asparagine - O-linked attachment via hydroxyl group of serine/threonine

Question 23

What forms the basis of blood groups?

Answer 23

Glycosylation

Question 24

What do kinases do?

Answer 24

Phosphorylates

Question 25

What do phosphatases do?

Answer 25

Dephosphorylates