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Biochem 1 (CHEM 441A) > Ch. 6 > Flashcards

Ch. 6 Flashcards

1
Q

What are the structural differences between myoglobin & hemoglobin?

A
  • Myoglobin: single polypeptide chain with 1 heme group
  • Hemoglobin: 4 polypeptides with 2 alpha and 2 beta subunits
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2
Q

What is fractional saturation?

A

The fraction of protein binding sites that are occupied

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3
Q

What is the formula for fractional saturation?

A

[protein-ligand complex]/[protein-ligand complex]+[protein]

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4
Q

What is the Bohr effect?

A

pH and CO2 dependence of oxygen binding

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5
Q

Where is 2,3-bisphosphoglycerate?

A

RBCs

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6
Q

What does 2,3-bisphosphoglycerate do?

A

Traps hemoglobin the the T state and acts as a negative effector

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7
Q

Where are positive regulators graphed?

A

To the left

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8
Q

How does 2,3-BPG affect oxygen binding?

A

Binding of 2,3-BPG to a secondary site inhibits binding of O2 to the primary sites

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9
Q

Where does 2,3-bisphosphoglycerate bind?

A

Between the 2 beta subunits

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10
Q

Why does 2,3-BPG prefer to bind to the T state of Hb?

A

R state of Hb has a smaller central cavity

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11
Q

What stabilizes the binding of 2,3-BPG to the beta subunits?

A

Ionic interactions between 2,3-BPG and 3 positively charges residues on each beta subunit

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12
Q

What is the effect of amino acid differences between adult and fetal hemoglobin?

A
  • Reduces the affinity of 2,3-BPG for the α2γ2 complex (fetus) compared to its affinity for the normal adult α2β2 complex
  • Decrease in 2,3-BPG affinity facilitates transfer of O2 from the mom’s Hb to the fetal Hb because fetal Hb can get more O2 if more Hb molecules are in the R-state (high-affinity)
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13
Q

List membrane proteins.

A
  • Membrane receptor proteins
  • Membrane-bound metabolic enzymes
  • Membrane transport proteins
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14
Q

What do membrane receptor proteins do?

A

Signal transduction

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15
Q

What do membrane-bound metabolic enzymes do?

A

Involved in redox reactions and ATP synthesis

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16
Q

Whta do membrane transport proteins do?

A

Facilitate the movement of polar molecules across the hydrophobic membrane

17
Q

What are the types of transport/transporters?

A

Passive and active

18
Q

What are the shapes of transport graphs?

A
  • Linear (simple diffusion and facilitated diffusion through a CHANNEL)
  • Hyperbolic (facilitated diffusion through a CARRIER and active transport through a carrier)
19
Q

How do you calculate free energy of transport?

A
20
Q

What is the structure and function of aquaporins?

A
  • Tetrameric protein complexes
  • Transport water molecules across a hydrophobic membrane
21
Q

What is primary active transport?

A

Uses the hydrolysis of ATP to drive molecules across membranes against their concentration gradient

22
Q

What is secondary active transport?

A

Uses the energy available from a downhill electrochemical gradient for one molecule to co-transport a second molecule against an uphill electrochemical gradient

23
Q

What is an ATP pump?

A
  • Na+/K+ pump
  • Exports Na+
  • Imports K+
  • Energy from ATP hydrolysis causes a conformational change in the protein that allows it to mediate Na+ and K+ transport against their concentration gradients
24
Q

What is an ATP binding cassette?

A

An active membrane transport protein that uses energy from ATP hydrolysis to drive large conformational changes and pump molecules across the membrane

25
Q

How do you use hydropathy plots to predict which portions of a protein cross a membrane?

A
  • Plot delta G against residue number
  • Positive delta G: hydrophobic
  • Negative delta G: hydrophilic
26
Q

Practice question: The heme group attached for myoglobin and hemoglobin provides 4 nitrogen atoms that are bond to iron. What are the other 2 atoms that bind to iron?

A

Proximal histidine and oxygen

27
Q

Practice question: What 2 molecules are involved in the Bohr effect and hemoglobin?

A

CO2 and protons

28
Q

Practice question: What describes the structure of hemoglobin?

A

All alpha helices with quaternary level of structure

29
Q

Practice question: What is moved into the plane of the heme ring when oxygen binds?

A

Fe

30
Q

Practice question: The fetal hemoglobin saturation curve would be ___.

A

In between the myoglobin binding curve and the adult hemoglobin curve

Biochem 1 (CHEM 441A) (12 decks)

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