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Biochem 200 > Protein Function > Flashcards

Flashcards in Protein Function Deck (35):
1

Which protein that we studied is a monomer?

Myoglobin

2

Which protein that we studied is a oligomer?

Hemoglobin

3

What is the major function of hemoglobin?

Binds to oxygen in the lungs and releases it in the tissues.

4

What is the major function of myoglobin?

Binds oxygen in muscle

5

What ability of proteins does the function heavily depend on?

Ability to bind to other small molecules REVERSIBLY

6

The ______ the affinity of Y for X the more XY we will have at any [] of X or Y.

Greater

7

What is Kd?

The concentration of ligand that gives 50% binding.

8

A small Kd =

high affinity

9

The structure of myoglobin is...

153 amino acids, 8 alpha helices + loops and a heme prosthetic group.

10

Where does heme fit perfectly in myoglobin?

Hydrophobic pocket between E and F.

11

Heme is...

circular and planar

12

Fe2+ in heme can form how many coordination bonds?

6

13

How is the porphyrin ring in heme held in place?

Hydrophobic interactions and coordination bond between Fe2+ and HisF8.

14

What is the main function of HisF8 (proximal)?

Permanently attach heme to global.

15

Where does oxygen bing to the heme group in myoglobin?

the 6th coordination position.

16

Oxygen always bonds at an angle, true of false?

True

17

Which His helps prevent oxidation of Fe2+?

HisE7 (distal)

18

Binding sites are designed precisely to optimize binding...

Specificity and affinity

19

Which His allows specificity for oxygen binding at the heme?

HisE7

20

Myoglobin has a _____ plot.

Hyperbolic

21

Does myoglobin have quaternary structure?

No, only tertiary.

22

How many subunits does hemoglobin have?

4

23

How many O2 can Hb bind?

4

24

Define conservative substitutions.

Minor effects on structure

25

Define critical substitutions.

Can change structure and therefore function

26

Hyperbolic curve is indicative of...

constant affinity

27

Sigmoidal curve is indicative of...

cooperative binding affinity

28

Hemoglobin has a _________ plot.

Sigmoidal

29

Sigmoidal oxygen binding curve means...

Cooperative process, necessary for efficient O2 delivery, reflects a change in binding affinity

30

How does Hb change its affinity for oxygen?

Conformational change

31

What are the two states of Hb?

Tense (low affinity, more salt bridges) and relaxed (high affinity, less salt bridges)

32

What is allostery?

The binding of a ligand at one site on a protein affects the binding of ligands at other sites.

33

What is homoallosteric?

Binding of the effector affects further binding of the SAME compound

34

What is heterosteric?

Binding of the effect affects further binding of a DIFFERENT compound

35

Oxygen is a _______ activator of Hb.

homoallosteric