Biochem. L3 Protien Stuctures

Question 1

1.Explain the 4 levels of structural organization of proteins and their significance for protein function.

Answer 1

• Primary structure: protein sequence
• Secondary structure: localized substructure in proteins
• Tertiary structure: three-dimensional structure of the protein ( creates specific pockets on the protein, which are essential for the function of protiens)
• Quaternary structure: association between polypeptide chains( -Cooperativity between Hemoglobin subunits increases oxygen binding.)(-increases the stability of the protien.)( regulates the activity of proteins)

Question 2

2.Explain how heat shock proteins can aid protein folding.

Answer 2

• Hsp 70 binds (like gum balls on a rope) to prevent premature protein folding until protein synthesis is completed.
• Hsp60 folds protein by using energy from ATP. provides a template for folding. ( looks like the washer drum)

Question 3

3.Differentiate among mechanisms that lead to protein. denaturation/aggregation.

Answer 3

1. Mutations
2. Proteloytic cleavage ( fragmentation of proteins)
3. Oxidative damage (by reactive oxygen species)
4. Altered environmental conditions

Question 4

4.Associate structural abnormalities of specific proteins with characteristic diseases.

Answer 4

1. Mutations : Creutzfeld-Jacob Diseases,prion disease
2. Proteloytic cleavage ( fragmentation of proteins): aggregation/precipitation of various misfiled protein fragments produced by proteolytic cleavage. lead to organ failure (Amyloidsis, alzheimer’s disease ( precipitation of beta-amyloid protiens)
3. Oxidative damage (by reactive oxygen species) : proteins ( hemoglobin) in red blood cells are damaged by oxygen radicals.protiens are denatured and precipitate in the cells.
4. Altered environmental conditions:
   - Extreme pH disrupts hydrogen bonds and ionic interactions
   - Increased temp. unfolds proteins
   - non-aqueous environment denature protiens ( Exposure by skin or ingestion to organic solvents)

Question 5

5.Explain the structural differences between myoglobin and hemoglobin.

Answer 5

Myoglobin:

• Oxygen Storage molecule in skeletal and heart muscle
• Is a tertiary structure, has on pocket for a 1 heme group which binds to one oxygen group.

Hemoglobin:

• Oxygen transport molecule in red blood cells.
• is a quartinary structure it has 4 pockets that bind to 4 heme molecules and bind one by one to an oxygen because binding to oxygen is cooperative
• composed of 2 alpha and 2 Beta subunits. ( non covalent bonds hold them together.)

Question 6

6.Distinguish between the oxygen saturation curves of myoglobin and hemoglobin.

Answer 6

• When O2 pressure is low O2 bind stronger to myoglobin than to hemoglobin.
• when O2 pressure is high hemoglobin picks of oxygen cooperatively.

Question 7

7.Differentiate among the mechanisms used by allosteric regulators to alter oxygen binding of hemoglobin.

Answer 7

see professor????

Question 8

9.Explain how carbon-monoxide affects oxygen binding of hemoglobin and alters the oxygen saturation curve.

Answer 8

-High CO2 concentration leads to increased proton concentration.
-CO2 direct binding to Hb stabilizes the deoxy form.
( co2 reacts with terminal group, not heme group)
- affinity is lowered ( heme group - o2) if co2 is high

Question 9

10.Differentiate between the oxygen saturation curves of fetal and adult hemoglobin.

Answer 9

• HbF has a higher affinity(stronger attachment ) than HbA ( B/C has lower affinity to 2,3-BPG.
• The higher O2 affinity of HbF helps transfer o2 form mom to the fetus.

Question 10

11.Associate abnormal levels and/or composition of blood hemoglobin with medical conditions.

Answer 10

-Sickle cell anemia (HbS):mutated β-chain
-Hemoglobin C disease (HbC):mutated β-chain
-Hemoglobin SC disease (HbSC)
mutated β chain
-Methemoglobinemia
oxidation of Fe2+ to Fe3+
-β-Thalassemias
decreased β-chain production
-α-Thalassemias
decreased α-chain production

Question 11

12.Differentiate among hemoglobinopathies based on their molecular mechanisms.

Answer 11

• sickle cell anemia Mutated Beta-Chain ( Hb down.)
• Methemoglobinemia: oxidations of Fe2+ instead of Fe3+
• α-Thalassemias:decreased α-chain production,Heinz bodies(Hb is down, Hb H up, Hb bart is up)
• β-Thalassemias:decreased β-chain production. Total Hb down Hb F up, HbA2 up