Chapter 5 - Protein Function

Question 1

Give 2 fibrous proteins and an description.

Answer 1

Collagen – tough, high tensile strength fibers
Elastin - relaxed, rubber-like, stretchable fibers

Question 2

Give two examples of fibrous and globular proteins.

Answer 2

Fibrous: Collagen and elastin
Globular: Myoglobin and hemoglobin

Question 3

Describe collagen structure.

Answer 3

Collagen is a tough, high tensile strength fiber. Consists of 3 polypeptide chains forming a left-handed triple helix stabilized by interchain H-bonds, with a repeating sequence of Gly-X-Y.

Question 4

What are the main non-standard amino acids? Contribute what to the collagen structure?

Answer 4

The main non-standard amino acids are hydroxyproline and hydroxylysine, which contribute to its stability and are created by hydroxylation of proline and lysine residues.

Question 5

What are the major types of collagens?

Answer 5

Type I, II, III, IV, VIII, IX and XII

Question 6

Where is Type I distributed?

Answer 6

Found in tendons, cornea, and skin, it provides high tensile strength.

Question 7

Where is Type II distributed?

Answer 7

Found in cartilage, especially in joints.

Question 8

Where is Type III distributed?

Answer 8

Present in blood vessels and skin, offering more distensible properties.

Question 9

Where is Type IV distributed?

Answer 9

Forms the basement membrane in tissues.

Question 10

Where is Type VIII distributed?

Answer 10

Contributes to the network structure of the cornea.

Question 11

Where is Type IX and XII distributed?

Answer 11

These are fibril-associated collagens, binding to the surface of collagen fibrils and linking them to the extracellular matrix (ECM)

Question 12

What are the functions of myoglobin?

Answer 12

Myoglobin functions as an oxygen carrier and reservoir in skeletal and cardiac muscle, storing oxygen for use during muscle activity.

Question 13

What are the functions of hemoglobin? Where is hemoglobin?

Answer 13

Hemoglobin, found in red blood cells, transports oxygen from the lungs to tissues and returns carbon dioxide to the lungs for exhalation.

Question 14

Hemeprotein allosteric effectors include what? (3)

Answer 14

Hemeprotein allosteric effectors include the partial pressures of oxygen and carbon dioxide, pH of environment, and the availability of 2,3-bisphosphoglycerate.

Question 15

Describe the 3 factors’ impacts on hemeprotein oxygen-dissociation curves.

Answer 15

pO2: Higher partial pressure of oxygen increases hemoglobin’s oxygen affinity, shifting the oxygen-dissociation curve to the left.
pCO2: Increased CO2 decreases oxygen affinity (Bohr effect), shifting the curve to the right, promoting oxygen release in tissues.
2,3-BPG: This molecule binds to deoxygenated hemoglobin, reducing its oxygen affinity, which also shifts the curve to the right and facilitates oxygen unloading

Question 16

What is Scurvy?

Answer 16

A genetic disease caused by a vitamin C deficiency, which disrupts the hydroxylation of proline and lysine in collagen, preventing proper interchain hydrogen bonding and collagen fibril crosslinking.

Question 17

What is osteogenesis imperfecta?

Answer 17

Osteogenesis imperfecta, also known as brittle bone disease, is a genetic disorder resulting from mutations in type I collagen genes, leading to bone fragility and frequent fractures. With Type I being mild and Type II being the most severe, often causing perinatal death.

Question 18

What is Hgb S disease?

Answer 18

Sickle cell anemia is a point mutation in the β-globin gene, where glutamate is replaced by valine. Causes hemoglobin to polymerize into fibers in the deoxygenated state, distorting red blood cells into a sickle shape, leading to blockages, pain, and reduced life expectancy.