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BIOC192 2024 > Lecture 11 > Flashcards

Lecture 11 Flashcards

1
Q

What is myoglobin?

A

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

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2
Q

What is the primary structure of myoglobin?

A

About 150 amino acids

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3
Q

What is the secondary structure of myoglobin?

A

8 Alpha helices labelled A-H and connecting loops

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4
Q

What is the tertiary structure of myoglibin?

A

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

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5
Q

What is the quaternary structure of myoglobin?

A

Monometric, a single polypeptide chain

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6
Q

What is the haem?

A

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

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7
Q

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

A

Reversible

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8
Q

What gives the haem its red colour?

A

The molecular electronic orbitals

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9
Q

How can we quantify dissolved molecules?

A

Through spectroscopy

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10
Q

What is spectroscopy?

A

A measure of how well light is transmitted through a solution

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11
Q

What type of light is used in the spectrometer?

A

Monochromatic light

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12
Q

What is the Beer-Lambert Law?

A

The conversion from absorbance to concentration

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13
Q

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

A

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

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14
Q

Is the globin protein coloured or colourless?

A

Colourless, but has UV absorbance

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15
Q

What colour is the oxyhaemoglobin?

A

Bright red

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16
Q

What colour is the deoxyhaemoglobin?

A

Dull red

17
Q

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

A

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

18
Q

What is the effect of the additional histidine residue?

A

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

19
Q

What is the structure of Haemoglobin?

A

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

20
Q

How many haems is there in haemoglobin?

A

Four, allowing the bonding of four O2 molecules

21
Q

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

A

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

22
Q

What is haemoglobin?

A

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

23
Q

What type of curve reflects myoglobins function?

A

Hyperbolic curve

24
Q

What type of curve reflects haemoglobins function?

A

Sigmoidal curve

25
Q

What is the saturation of myoglobin?

A

Saturated with O2 at low partial O2 pressures

26
Q

What is the saturation of haemoglobin?

A

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

27
Q

What is Co-operativity?

A

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

28
Q

What are the two states of co-coperativity?

A

T-state and R-state

29
Q

What is the T-state?

A

Tense state, low O2 affinity

30
Q

What is the R-state?

A

Relaxed state, high O2 affinity

31
Q

What are the similarities between haemoglobin and myoglobin?

A

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)

32
Q

What are the differences of myoglobin and haemoglobin respectively

A

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

33
Q

What is allostery?

A

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.

34
Q

What are the features allostery

A

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

35
Q

What are the features of cooperativity

A

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

BIOC192 2024 (25 decks)

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