Hemo-Myoglobin

Question 1

Where are plasma proteins manufactured, and what type of proteins are not manufactured there?

Answer 1

The liver except for immunoglobulins.

Question 2

What elevated protein indicates hepatic tissue damage?

Answer 2

Alanine aminotransferase (ALT)

Question 3

What is an isozyme?

Answer 3

They catalyze the same reaction but have different physical properties.

Question 4

What is the significance of creatine kinase (CK) and it having 3 isozymes?

Answer 4

The 3 different isozymes are located in different tissues. Elevated levels of a certain isozyme can suggest tissue damage. So the ratio of these isoenzymes to one another can help identify the tissue. More specifically, it can help identify an MI.

Question 5

What are the biomarkers that are important in detecting an MI, and describe the manifestation.

Answer 5

Creatine Kinase (CK) isozyme in heart and Troponin. This enzyme, and protein, are elevated after an MI, and peak at about 24-36 hours after an MI, but then return to normal after about 5 days. This information can help pinpoint if and when an MI occured.

Question 6

Why can gel electrophoresis of plasma proteins be helpful clinically?

Answer 6

The ratios of plasma protiens can help identify certain disease.

Question 7

What is the cause of Kwashiorkor disease in children?

Answer 7

Protein malnutrition. Albumin acts as an osmotic regulator, cannot be made because there is a lack of essential amino acids. Fluid builds up in tissues as a result, especially in abdomen (ascites).

Question 8

Hemoglobin and myoglobin are in what type of proteins?

Answer 8

Globular

Question 9

What is “Heme”?

Answer 9

Heme acts as a prosthetic group in hemeproteins. Its made in the liver and erythrocyte producing cells of bone marrow. Its comprised of a Protoporphyrin ring IX + Fe ion.

Question 10

What is the role of Heme in Hemoglobin and Myoglobin

Answer 10

Reversible binds oxygen.

Question 11

Give a basic description of the Myoglobin molecule.

Answer 11

One polypeptide, mainly alpha-helices, and one heme group.

Question 12

Give a basic description for Hemoglobin.

Answer 12

• Four subunits with hydrophobic, and ionic links (salt)
• Four heme groups

Question 13

What is a prosthetic group?

Answer 13

A coenzyme permanently associated with an enzyme.

Question 14

In terms of oxygen bindind, what is the difference between myoglobin and hemoglobin?

Answer 14

• Myoglobin = oxygen storage protein in muscle
• Hemoglobin = oxygen-carrier protein in blood

Question 15

Think about the subunits of hemoglobin; how many oxygen molecules can a hemoglobin carry?

Answer 15

4 because hemoglobin has 4 subunits and 4 heme groups.

Question 16

How does myoglobin function with oxygen, or what’s its purpose?

Answer 16

Binds, stores, and releases O2 with changes in O2 concentration in the sarcoplasm of skeletal muscle & heart.

Question 17

Describe the role of hemoglobin with NO.

Answer 17

NO is a potent vasodilator. Hemoglobin reversible binds NO, and delivers it to the vessel wall

Question 18

Describe the dissociation curves of myoglobin and hemoglobin.

Answer 18

• Myoglobin has hyperbolic curve
• Hemoglobin has sigmoidal curve

Question 19

Describe the change in hemoglobin dimers upon the binding of Oxygen.

Answer 19

• Hemoglobin is a tetramer. Before oxygen binds (known as taut, or T state) it has two dimers that are ionically bound (weak), and the two other subunits are hydrophobically bound (strong). (deoxyhemoglobin)
• Oxygen begins to bind and some of the ionic bonds between dimers break resulting in the relaxed, or R state (this is known as oxyhemoglobin)

Question 20

Describe how pH affects the binding affinity of oxygen and hemoglobin.

Answer 20

ph is an allosteric effector. Decreasing the pH causes a decrease in oxygen affinity, and a shift to the right on the dissociation curve. This means that a decrease in pH requires a HIGHER pO2 to get the same O2 saturation.

Question 21

Describe how hemoglobin transports CO2. How does it affect the oxygen-dissociation curve?

Answer 21

Hb transports CO2 as a carbamate in the form of a carbaminohemoglobin. CO2 stabilizes the T form of Hb (deoxy form), and causes a shift to the right of the dissociation curve.

Question 22

What is the affect of CO on the binding of O2 to Hb? (also what happens to dissociation curve?)

Answer 22

CO binds tightly to Hb but reversibly. It also causes a shift to the R state for Hb. This means that Hb binds oxygen much more tightly, and has an impaired release to tissues. CO shifts O2/Hb dissociation curve to the left.

Question 23

What is the effect of BPG on Hb?

Answer 23

BPG is an allosteric effector. BPG (2,3-biphosphoglycerate) has high affinity to the T form of Hb. Binding of BPG to Hb lowers the affinity to oxygen, which promotes release of oxygen. This is represented by a shift to the right on the dissociation curve.

Question 24

Give a basic description of the O2 binding to Hb of these states:

• High pO2
• High pCO2
• Low pH
• BPG

Answer 24

• High pO2 strengthens O2 binding
• High pCO2 weakens O2 biding
• Low pH weakens O2 binding
• BPG weakens

Question 25

What is glycation? What is a the most abundant and clinically relevant example?

Answer 25

The non-enzymatic addition of a sugar to a protein. Hemoglobin A (HbA) binds glucose forming HbA1c, which is elevated in diabetes mellitus.

Question 26

In what scenario might you see 2,3-biphosphoglycerate (BPG) levels rise, and why?

Answer 26

BPG lowers affinity of Hb to O2. Thus, increasing the affinity at lower pO2. In a scenario of hypoxia (such as anemia, smoking, high altitude), BPG will increase to allow O2 to bind to compensate for a lower pO2.