protein structure and function

Question 1

How do we get our essential amino acids?

Answer 1

they come from food in our diet

Question 2

How do we get our non-essential amino acids?

Answer 2

they are made by the body from the essential amino acids or from the breakdown of proteins

Question 3

How are peptide bonds formed?

Answer 3

• generated by peptidyl transferase
• condensation to form covalent bond

Question 4

Describe how alpha helixes look

Answer 4

• spiral
• side chains face outwards

Question 5

How are alpha helixes formed?

Question 6

Describe how beta pleated sheets look

Answer 6

• flat structure
• side chains extended above and below beta sheet

Question 7

How are beta sheets formed?

Answer 7

hydrogen bonds form between carbonyl groups and an amino acid of neighbouring chain

Question 8

What are two other possible secondary structures?

Answer 8

• loops and turns
• random coils

Question 9

What is a coiled coil?

Answer 9

• 2 or 3 alpha-helixes wind around each other forming a coiled coil
• e.g keratin or collagen

Question 10

Is the folding process energetically favorable or not ?

Answer 10

it is energetically favourable

Question 10

Finish this sentence: Proteins spontaneously fold into a 3 dimensional….

Answer 10

conformation of the lowest free energy

Question 11

What are molecular chaperones?

Answer 11

proteins that bind to the partially folded polypeptide chains and assist them in folding

Question 12

How do chaperones help?

Answer 12

• do not change 3D structure
• speed up folding process
• prevent protein aggregation
• reduct non-productive intermediates

Question 13

What are the two types of molecular chaperones ?

Answer 13

• heat shock proteins
• chaperonins

Question 14

What are post translational modifications?

Answer 14

processing events resulting from proteolytic cleavage or the covalent addition of a modifying group

Question 15

What is phosphorylation?

Answer 15

addition of a phosphate to specific amino acids regulating the activity of the protein

Question 16

What is glycosylation?

Answer 16

addition of carbohydrates to specific sites on the protein

Question 17

What is ubiquitination?

Answer 17

addition of ubiquitin can target the protein for destruction by the proteasome

Question 18

What are the symptoms of cystic fibrosis due to?

Answer 18

• single deletion of amino acid phenylalanine at position 508
• mutant CTFR protein becomes stuck in endoplasmic reticulum leading to reduced chloride conductance out of cells

Question 19

What does CTFR stand for (in cystic fibrosis)?

Answer 19

Cystic Fibrosis Transmembrane conductance Regulator

Question 20

What is Alzheimer’s Disease characterised by?

Answer 20

progressive memory loss and cognitive decline

Question 21

What is alzheimer’s caused by

Answer 21

• misfolding of amyloid beta (form tightly packed beta sheets)
• causing amyloid beta plaques and tau
• causes intracellular neurofibrillary tangles

Question 22

What determines how the protein folds?

Answer 22

the distribution of hydrophobic and hydrophilic side chains along the backbone

Question 23

What are the 3 types of post-translational modifications?

Answer 23

• phosphorylation
• glycosylation
• ubiquitination