Lecture 11

Question 1

What is myoglobin?

Answer 1

An oxygen storage protein in tissue which holds O2 until it is required

Question 2

What is the primary structure of myoglobin?

Answer 2

About 150 amino acids

Question 3

What is the secondary structure of myoglobin?

Answer 3

8 Alpha helices labelled A-H and connecting loops

Question 4

What is the tertiary structure of myoglibin?

Answer 4

Globin fold that generates a hydrophobic pocked where the haem binds to the HisF8

Question 5

What is the quaternary structure of myoglobin?

Answer 5

Monometric, a single polypeptide chain

Question 6

What is the haem?

Answer 6

Four pyrrole rings linked together in a plane. Central Iron with six coordinate bonds with four to the N of the haem (pyrrole rings), one to the N of the HisF8 and one to O2

Question 7

Is the binding of O2 to the Fe2+ reversible or irreversible?

Answer 7

Reversible

Question 8

What gives the haem its red colour?

Answer 8

The molecular electronic orbitals

Question 9

How can we quantify dissolved molecules?

Answer 9

Through spectroscopy

Question 10

What is spectroscopy?

Answer 10

A measure of how well light is transmitted through a solution

Question 11

What type of light is used in the spectrometer?

Answer 11

Monochromatic light

Question 12

What is the Beer-Lambert Law?

Answer 12

The conversion from absorbance to concentration

Question 13

How does the spectroscopy of the globins measure the binding of O2?

Answer 13

Shape of the spectrum differs with colour and the chemical nature of solute.

Question 14

Is the globin protein coloured or colourless?

Answer 14

Colourless, but has UV absorbance

Question 15

What colour is the oxyhaemoglobin?

Answer 15

Bright red

Question 16

What colour is the deoxyhaemoglobin?

Answer 16

Dull red

Question 17

How does the O2 binding to the haem differ its structure?

Answer 17

HisF8 binds to Fe out of plane; when O2 binds in the 6th position, it brings the Fe into plane; creating a planar shape.

Question 18

What is the effect of the additional histidine residue?

Answer 18

Binds to the O2 and slightly weakens the bond, distorting it and making the O2 more easily reversible

Question 19

What is the structure of Haemoglobin?

Answer 19

A tetramer that has 4 globin proteins, normally 2 alpha and 2 beta which associate together non-covalently

Question 20

How many haems is there in haemoglobin?

Answer 20

Four, allowing the bonding of four O2 molecules

Question 21

How does the binding of O2 alter the shape of haemoglobin?

Answer 21

Each additional O2 added makes a more conformational change, attracting the binding of the remaining O2

Question 22

What is haemoglobin?

Answer 22

An oxygen delivery protein for tissue and therefore must acquire it in the lungs, bond to oxygen must be weaker in order to release at the right time

Question 23

What type of curve reflects myoglobins function?

Answer 23

Hyperbolic curve

Question 24

What type of curve reflects haemoglobins function?

Answer 24

Sigmoidal curve

Question 25

What is the saturation of myoglobin?

Answer 25

Saturated with O2 at low partial O2 pressures

Question 26

What is the saturation of haemoglobin?

Answer 26

Only becomes saturated in the lungs, where there is very high partial O2 pressure

Question 27

What is Co-operativity?

Answer 27

Binding events in which the Binding Affinity of a molecule to an interaction partner is influenced by a preceding binding event

Question 28

What are the two states of co-coperativity?

Answer 28

T-state and R-state

Question 29

What is the T-state?

Answer 29

Tense state, low O2 affinity

Question 30

What is the R-state?

Answer 30

Relaxed state, high O2 affinity

Question 31

What are the similarities between haemoglobin and myoglobin?

Answer 31

Oxygen binds to iron of haem, shifts from dull to bring red allows monitoring of O2 binding, Oxygen-bound form has subtle change in haem (planar)

Question 32

What are the differences of myoglobin and haemoglobin respectively

Answer 32

Storage molecule in tissue vs transport molecule to tissue monomer vs tetramer Tight, hyperbolic binding vs weak, sigmoidal binding

Question 33

What is allostery?

Answer 33

the condition of an enzyme in which the structure and activity of the enzyme are modified by the binding of a metabolic molecule at a site other than the chemically active one.

Question 34

What are the features allostery

Answer 34

It can occur in monomeric or multiple subunit proteins/enzymes Involves regulators or post-translational modifications away from the active site can be linked with co-operativity

Question 35

What are the features of cooperativity

Answer 35

Require multiple interacting subunits Generates a sigmoidal binding curve shifts binding affinity to a physiological relevant concentration