Protein Structure & Function

Question 1

What type of reaction creates peptide bonds? And where does it occur?

Answer 1

Condensation reaction between the carboxylic and amino group

Question 2

Which amino acid is the most HYDROPHOBIC?

Answer 2

Isoleucine

Question 3

Which amino acid is the most HYDROPHILIC?

Answer 3

Arginine

Question 4

What does a POSITIVE value indicate on a hydropathy index?

Answer 4

A polypeptide most likely to be found in the membrane

Question 5

TRUE OR FALSE?
Polypeptide chains are planar?

Answer 5

True

Question 6

TRUE OR FALSE?
Alpha helices have one positive angle and one negative angle?

Answer 6

False.
They have 2 negative angles

Question 7

TRUE OR FALSE?
Beta pleated sheets have one positive angle and one negative angle?

Answer 7

True

Question 8

Which amino acids do Zinc Finger Motifs require?

Answer 8

2x Cysteine
2x Histidine

Question 9

What amino acids are required for catalytic sites on enzymes?

Answer 9

• Serine
• Asparagine
• Histidine

Question 10

What interactions contribute to the stabilisation of the protein molecule?

Answer 10

• Hydrophobic Ionic Interactions
• Hydrogen bonding
• Van der Waals forces

Question 11

What function(s) does Phosphorylation usually modulate?

Answer 11

Regulation

Question 12

What function(s) does Glycosylation usually modulate?

Answer 12

• Folding
• Stability
• Regulation

Question 13

What function(s) does Acetylation usually modulate?

Answer 13

Regulation

Question 14

Which amino acids have a phosphate group added to them during Phosphorylation?

Answer 14

• Serine
• Threonine
• Tyrosine

Question 15

What function(s) does Hydroxylation usually modulate?

Answer 15

Regulation

Question 16

What function(s) does Methylation usually modulate?

Answer 16

• Regulation - epigenetics

Question 17

Which amino acids are involved in Hydroxylation?

Answer 17

• Lysine
• Asparagine

Question 18

TRUE OR FALSE?
Every AA residue is essential for function?

Answer 18

False.
Every AA contributes towards the final structure, every residue is NOT essential for function

Question 19

What percentage of human proteins are polymorphic?

Answer 19

20-30%

Question 20

Where do cells acquire the molecules and ions they need?

Answer 20

Extracellular Fluid (ECF)

Question 21

What is a Chemical Gradient?

Answer 21

A difference in solute concentrations across a membrane

Question 22

What is an Electrical Gradient?

Answer 22

A difference in potential/charge across a membrane

Question 23

What is Resting Potential?

Answer 23

Static membrane potential

Question 24

What is an Action Potential?

Answer 24

Rapid rise and fall in membrane potential causing similar cells to depolarise

Question 25

What ions flow in and out of a cell during an Action Potential?

Answer 25

* INWARDS - Na+ * OUTWARDS - K+

Question 26

What AA sequence is found in the signature motif of K+ channels?

Answer 26

* Threonine * Valine * Glycine * Tyrosine * Glycine

Question 27

Which technique was mostly used for Ion Conductance measurements?

Answer 27

Patch Clamping - single channel recordings

Question 28

What shape is the Bacterial KcsA Channel?

Answer 28

V shaped tetramer

Question 29

How many residues does the Bacterial Kcs Channel have?

Answer 29

158

Question 30

How many subunits does the Bacterial Kcs Channel have?

Answer 30

Four identical subunits

Question 31

What is in the middle of the membrane of the the Bacterial Kcs Channel?

Answer 31

Hydrated K+

Question 32

What THREE segments make up the subunit structure of the Bacterial Kcs Channel?

Answer 32

1. Selectivity Filter 2. Cavity / Lake 3. Internal Pore

Question 33

What amino acids make up the Selectivity Filter for K+ channels?

Answer 33

TVGYG * Four layers of carbonyl atoms (VGYG) * One layer of hydroxyl atoms (Thr)

Question 34

How many binding sites does the Selectivity Filter have for dehydrated K+?

Answer 34

4

Question 35

How many coordination sites do K+ ions have?

Answer 35

8 sites occupied by H20 molecules

Question 36

Which negatively charged amino acids are at the K+ ion channel entrance?

Answer 36

Glu and Asp

Question 37

What amino acids are on each voltage sensor of the ion channel?

Answer 37

4 Arg

Question 38

How does ion channel inactivation occur?

Answer 38

N-terminal ball plugs the pore from the cytoplasmic side