Proteins 2 - w2

Question 1

What is the globular hemeprotein only functioning as O2 storage?

Answer 1

myoglobulin

Question 2

What is the structure of myglobulin?

Answer 2

single polypeptide chain (monomer)

Question 3

How many a-helices does myoglobin have?

Answer 3

eight

Question 4

Where does the heme in myoglobin attach to?

Answer 4

the nonpolar AA in the interior of the chain

Question 5

Which histidine residue binds Fe2+?

Answer 5

proximal histidine

Question 6

What is the name of the porphyrin ring surrounding the Fe2+ in heme?

Answer 6

Protoporphyrin IX

Question 7

What atoms of the pyrrole ring bind to the iron?

Answer 7

NITROGEN!

Question 8

What is the quaternary structure of hemoglobin?

Answer 8

tetramer (2a and 2B)

Question 9

What 2 structures make up hemoglobin (a holoprotein)?

Answer 9

heme (prosthetic group) and globin (apoprotein)

Question 10

What happens when O2 binds to heme?

Answer 10

without oxygen: Fe2+ is loosely attached to nitrogen

with oxygen: conformational change, pulling Fe2+ into the ring

Question 11

How does 2,3 BPG/DPG influence O2 binding to heme?

Answer 11

it decreases O2 affinity by binding to deoxy-HB not oxy-Hb. it helps in unloading of O2 into tissues

Question 12

What is the Bohr effect regarding CO2?

Answer 12

more CO2 in tissues -> lowers pH –> decreases Hb affinity for O2 and favours unloading

Question 13

Which hemoglobin is present in developing fetuses?

Answer 13

HbF (2 y chains instead of 2 B chains, raises affinity for O2)

Question 14

Which hemoglobin is an indicator for glycemic control in diabetes mellitus?

Answer 14

HbA1C

Question 15

What is the pathophysiology of sickle cell disease (HbS)?

Answer 15

point mutation that replaces glutamic acid with valine

Question 16

What makes up about 30% of the protein mass of the body?

Answer 16

collagen

Question 17

What is the structure of collagen?

Answer 17

three polypeptide alpha chains (not helix) that form to make a super helix; every third AA is glycine

Question 18

What bonds stabilize collagen chains?

Answer 18

inter-chain hydrogen bonds

Question 19

What is the most common order of amino acids in collagen?

Answer 19

glycine - PROLINE - hydroxyproline/hydroxylysine (posttransl hydroxyl of either)

Question 20

What are the do the first three types of collagen do?

Answer 20

forms fibrils, widely distributed in skin, blood vessels, etc

Question 21

What does nonfibrillar collagen (type 4) do?

Answer 21

provides a meshwork in basement membrane

Question 22

Damage to type 4 collagen causes what?

Answer 22

glomerular diseases in the kidney

Question 23

Why is hydroxylation of proline and lysine important in collagen synthesis?

Answer 23

adding OH allows the different chains to make hydrogen bonds

Question 24

What type of bonds occur at the terminals of procollagen?

Answer 24

disulfide bonds

Question 25

Where does pre-procollagen formation occur?

Answer 25

rough endoplasmic reticulum

Question 26

What are the two co-factors for the hydroxylation of proline and lysine?

Answer 26

vitamin C and ascorbic acid-dependent

Question 27

What causes scurvy (bleeding gums and bruising)?

Answer 27

vitamin C deficiency causes impaired hydroxylation of proline and lysine (affects triple helix formation)

Question 28

What is the disease that causes hyperelasticity of the skin and arterial rupture due to fibrillary collagen defects?

Answer 28

Ehler’s Danlos syndrome

Question 29

What is the brittle bone disease?

Answer 29

osteogenesis imperfecta

Question 30

What causes osteogenesis imperfecta?

Answer 30

replacement of glycine with bulkier AA (in type 1 collagen)