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Biocheem > Lecture 18 > Flashcards

Lecture 18 Flashcards

1
Q

How does CO2 affect oxygen release?

A

It promotes the release of oxygen

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2
Q

How do salt bridges effect the deoxy form of Hb?

A

They stabilize the deoxy form

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3
Q

What three things stabilize the deoxy from of Hb?

A

H+, BPG and salt bridges

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4
Q

What is a function of a protein determined by?

A

It’s structure

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5
Q

What substitution occurs with sickle cell anemia?

A

In the beta chain Glu6 is replaced is with valine

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6
Q

How does the substitution of glutamine for amino effect Hb?

A

It causes Hb molecules to aggregate into long polymers/fibres because a small hydrophobic surface patch is exposed

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7
Q

What is Fetal Hemoglobin responsible for?

A

Circulation of oxygen within a fetal bloodstream

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8
Q

What is the ranking of affinity for O2 of each hemoglobin?

A

Adult Hb < Fetal Hb < Mb

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9
Q

What are the four subunits of Fetal Hemoglobin?

A

It has two alpha and two gamma subunits

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10
Q

What are the gamma subunits in fetal Hb similar to?

A

The adult Beta subunit

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11
Q

What is the His143 in adult Hb substituted with in Fetal Hb?

A

The histidine is replaced with serine

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12
Q

What is the His143 involved in with adult Hb?

A

The binding of BPG

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13
Q

What is the difference between the Serine in fetal Hb instead of His 143 in adult Hb binding to Hb?

A

The serine has lower affinity of binding to BPG which means there is increased binding affinity for oxygen in Fetal hb

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14
Q

What is the main difference between fetal Hb and adult Hb?

A

Fetal Hb has a serine instead of a histidine meaning that it has less affinity to bind to BPG which is a negative allosteric effector. Because fetal Hb has less affinity for BPG it has higher affinity for O2

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15
Q

Which direction does fetal Hb shift the graph?

A

Shift left because it has a higher affinity for oxygen

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16
Q

Why are histidines used a lot?

A

Because it has a pka close to 7

17
Q

What does His F8 (Proximal Histidine) do?

A

Binds to heme and coordinates the iron atom to prevent it from being oxidized. It also ensures the heme is strongly bound within the binding site

18
Q

What does His E7 (Distal Histidine) do?

A

It forms an H bond with O2 and increases the specificity of O2 for oxygen and diminishes carbon monoxide affinity

19
Q

What do the changes in protonation state in the central cavity or at the subunit interface do to the histidines?

A

They can lead to changes in how they bind to BPG or how they stabilize the T state

20
Q

What is the Bohr effect about?

A

The pH dependance of O2 binding

21
Q

How does low pH effect BPG?

A

It increases BPG binding

22
Q

What is the equation of Nitrogen fixation?

A

N2 + 3H2 ➡️ NH3

23
Q

What are enzymes involved in?

A

Increasing reaction rates

24
Q

What are the two ways a reaction can be accelerated by?

A
  • Adding heat

* Adding a catalyst (enzyme)

25
Q

What is a catalyst?

A

Something that increases the rate but is not ultimately consumed in the process of the reaction

26
Q

What are enzymes usually made of?

A

Proteins but they are sometimes RNA

27
Q

What types of proteins are enzymes usually?

A

they are globular proteins

28
Q

What portion of a reaction do enzymes effect?

A

The kinetics

29
Q

What is the specificity of enzymes?

A

They are very specific, they don’t propagate side reaction

30
Q

What suffix do enzymes usually end with?

A

-ase

31
Q

How does the name of an enzyme generally describe the process?

A
  • Substrate name (or product name)

* Chemical reaction

32
Q

What does changing the shape of an enzyme do?

A

Regulates it by changing its function

33
Q

What is required of the energy for a reaction to occur?

A

A reaction will only process if the free energy of the products is less than the free energy of the reactants

34
Q

What is the equation for the energy of a reaction?

A

Grxn + Gp - Gr

35
Q

What happens when Grxn is negative?

A

The reaction is exergonic and thermodynamically favorable (spontaneous)

36
Q

What effects how rapidly a reaction occurs?

A

There is some kind of barrier between the starting and end state

37
Q

What is a transition state?

A

A third state in a reaction with its own energy that must be considered

Biocheem (38 decks)

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