Week 4 Biochem

Question 1

Collagen is an example of a _____ protein that exhibits a tightly wound _____ structure.

Answer 1

1. Fibrous

2. Triple helix

Question 2

Globular proteins are considered highly water soluble because _______.

Answer 2

They have:

1. Polar AA Side Chains facing OUT
2. Non-polar side chains interiorly (hydrophobic core)

Question 3

______ is considered the prosthetic group for Hemoglobin.

Answer 3

Heme

Question 4

Define the structure of Heme:

Answer 4

A porphyrin ring (4 cyclic rings containing nitrogen) with a ferrous (Iron in the 2+ state –> Fe2+) ion in the center.

Question 5

What 2 forces hold the heme group of myoglobin to its structure?

Answer 5

1. Histidine forms a covalent bond to Fe2+.

2. Hydrophobic Interactions with the porphyrin ring.

Question 6

What is the importance of the Fe2+ being buried deep inside the porphyrin ring of heme in myoglobin?

Answer 6

It ensures that oxygen only travels through the globular protein and is released as O2, not superoxide.

Question 7

Sperm whale myoglobin is identical to _______ in humans. But what is different between the two structures and why is it remarkable?

Answer 7

1. Beta-Globin
2. The Primary Sequence is very different, but the few CONSERVED amino acids are able to give the same shape and function.

Question 8

The _____ histidine of hemoglobin is covalently bonded to the heme group, while the ______ histidine is free to act as a buffer for pH and a/b-dimer linkage.

Answer 8

1. Proximal

2. Distal

Question 9

Cooperative Binding:

Answer 9

O2 acts as an ALLOSTERIC regulator of its own binding to Hb because binding of one molecule of O2 increases Hb’s affinity for more O2 binding.

Question 10

Bohr Effect:

Answer 10

Describes how Hb responds to changing pH by changing its O2-affinity.

Question 11

2,3-BPG acts to ______ the O2 affinity of Hb, therefore it is considered to be a ________ of Hb.

Answer 11

1. Decrease

2. Negative Allosteric Regulator

Question 12

4 Allosteric Regulators of Hb:

Answer 12

• pO2
• pCO2
• pH
• 2,3-BPG

Question 13

Titration of a strong acid with a strong base yields __________.

Answer 13

The formation of Salt Water (Salt + H20) at the equivalence point of pH=7.

Question 14

A ______ Ka implies a stronger acid, while a _____pKa implies a stronger acid ________.

Answer 14

1. Higher Ka = Stronger

2. Lower pKa = Stronger

Question 15

When titrating a weak acid with a strong base, the pKa is the pH range at which ________.

Answer 15

50% dissociation has occurred

i.e. [HA] = [A-] ….AND….[weak acid] = 1/2[strong base]

Question 16

The buffer range is seen at ________.

Answer 16

(+/-) 1 pH unit from the pKa

Question 17

The pKa of Acetic Acid is ________.

Answer 17

pH = 4.75

Question 18

Titratable Acidity for weak acids is _______ compared to strong acids.

Answer 18

The same