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Elements of Medicine > Myoglobin and Hemoglobin > Flashcards

Myoglobin and Hemoglobin Flashcards

1
Q

majority of cell proteins, soluble in water

A

globular proteins

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2
Q

Hydrogen bonding acts to _________ the highly polar N-H bonds and C=O of the secondary structure

A

neutralize

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3
Q

Globular protein structure is stabilized by what three things?

A

Hydrogen bonds, ionic interactions, and disulfide bonds (least common)

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4
Q

What are some functions of globular proteins?

A

storage of ions (myoglobin which stores the majority of the body’s iron in ferritin), transport (hemoglobin and oxygen), antibodies, muscle contraction (actin/myosin), enzymes

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5
Q

T/F. Ligands or globular proteins are held irreversibly.

A

False

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6
Q

If a protein has multiple subunits, and a ligand binds leading to a conformational change in the other subunits, this is _______________.

A

cooperativity (can be positive or negative)

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7
Q

What quality of proteins make myoglobin and hemoglobin unique?

A

Unlike other protein side chains which lack an affinity for oxygen, myoglobin and hemoglobin evolved to contain organometallic compounds that can carry oxygen

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8
Q

What makes iron suitable for oxygen carrying?

A

Easily oxidized but doesn’t form free radicals like other transition metals

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9
Q

What is the purpose of having a globular protein surround the heme?

A

The protein protects the iron from becoming oxidized early

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10
Q

How do myoglobin and hemoglobin compare in relation to oxygen binding affinity?

A

Myoglobin binds oxygen with higher affinity so even at low pO2 levels

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11
Q

Although myoglobin and hemoglobin have similar functions, their ______ _______ are completely different.

A

primary structures

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12
Q

What is the missense mutation that leads to sickle cell anemia?

A

E6V

Mutation of glutamate to valine at the sixth amino acid position

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13
Q

Protoporphyrin IX containing a bound iron atom is called a _____.

A

heme

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14
Q

With oxygen binding, does the iron shift closer to the proximal or distal His?

A

proximal

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15
Q

The _____ His forms a coordination complex with the iron.

A

proximal

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16
Q

Why are there hydrophobic amino acids (Val and Phe) surround the heme group?

A

Prevent polar molecules from entering and oxidizing the Fe

17
Q
  1. What are the two states hemoglobin can be found in?

2. Which state forms in low pH and why?

A
  1. T and R state
  2. T state forms in low pH. High concentration of hydrogen ions leads to the protonation of the His 1446 at the C term of beta. The His-H forms a salt bridge with an Asp 94 residue. This makes the hemoglobin have a lower oxygen affinity.
18
Q

Salt bridges and 2,3- BPG stabilize _____ state.

A

T

19
Q

Positive cooperativity is recognized by a ______ binding curve when graphed.

A

sigmoidal

20
Q

What can you add to patient blood to encourage release of oxygen?

A

2,3- BPG

21
Q

How does the pH difference between the lungs and the tissues make oxygen transport more effective?

A

Tissues have lower pH because actively metabolizing tissues releasing hydrogens and carbon dioxide. Lungs have higher pH. In lungs, the R state is more common allowing Hb to pick up oxygen. Once Hb travels throughout the body, comes into contact with acidic tissues. Protonation of His occurs, forcing Hb into T state and leading to dropping off oxygen.

22
Q

How does 2,3- BPG stabilize the T state?

A

binds to positive residues in Hb

23
Q

CO wants to bond as a triple bond, but the ________ histidine group blocks the linear fashion in the pocket

A

E7

24
Q

Heme can also bind this molecule, which stimulates tissues to relax and blood to flow

A

nitric oxide

25
Q

What is the enzyme found in placental cells and RBCs that helps convert 1,3-BPG (by product of glycolysis) to 2,3 BPG?

A

2,3 BPG mutase
Explanation: in RBCs, helps release oxygen for people in high altitudes. In placenta, helps release oxygen to baby from mother.

26
Q

In tissues, Hb binds NO instead of one of the four oxygens. Why does this happen?

A

NO is a vascular smooth muscle relaxer. Allows for easier flow of oxygen into tissues.

27
Q

EPAS1 up regulation is found in what populations?

A

Tibetans. Increased forearm blood flow compared to low altitude dwellers

28
Q

Methemoglobin is Hb with _____ instead of ____. This reduces the ability to carry oxygen. Newborns that are given too much NO have a blue tinge because ____ binds ____ better than it binds oxygen.

A

Methemglobin is Hb with Fe 3+ instead of Fe 2+. This reduces the ability to carry oxygen. Newborns that are given too much NO have a blue tinge because Fe 3+ binds cyanide better than it binds oxygen.

29
Q

Which enzyme can reverse the methemoglobin to hemoglobin? Deficiency of this enzyme can cause what?

A

NADH- methemoglobin reductase

cyanosis

30
Q

NADH- methemoglobin reductase is found _____ less in newborns, making them extremely susceptible to methemoglobinemia.

A

50%

31
Q

Methemoglobinemia can be caused by what things?

A

Deficiency in NADH- methemoglobin reductase, too much NO as infants, reactive oxygen species/inherited defects

32
Q

Fetal hemoglobin, _________, has a stronger affinity for oxygen, and it extracts hemoglobin from the mothers blood

A

HbF

33
Q

Why does HbF become useless postpartum?

A

The high oxygen affinity prevents release at tissues

34
Q

What is HbA1c?

A

Glycated Hb

35
Q

What creates the sickled appearance of RBCs in HbS?

A

E6V mutation leads to a compilation of hydrophobic valines on the outside of the protein. The Hb is “sticky” and hydrophobic regions group together, curving inward

36
Q

T/F. Individuals with sickle cells should live at high altitudes

A

False. Increases sickling and they already have lower oxygen affinity

37
Q

How is silencing BC11A a possible treatment for sickle cell?

A

Increase production of HbF

38
Q

Hemoglobin C, changes E6K, and leads to what disease

A

mild hemolytic anemia

Explanation: mild because changing polar AA to polar AA.

Elements of Medicine (10 decks)

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