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A Level Biology > Haemoglobin and oxygen dissociation curves > Flashcards

Haemoglobin and oxygen dissociation curves Flashcards

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1
Q

Describe the structure of haemoglobin

A

Quaternary structure
4 polypeptide chains
Each polypeptide chain contains haem group
Containing iron ion fe2+ which combines with oxygen

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2
Q

How many oxygen molecules can each haem group combine with ?

A

1 oxygen molecule

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3
Q

How many molecules of oxygen can each haemoglobin carry

A

4 oxygen molecules

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4
Q

What happens to haemoglobin at the lungs

A

In the lungs there is high pO2 so haemoglobin has a high affinity for oxygen

Oxygen readily loads with haemoglobin
This is done by oxygen joining to haemoglobin to form oxyhemoglobin
Hb + 4O2 —-> HbO8

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5
Q

What is the partial pressure of oxygen ?

A

A measure of oxygen concentration

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6
Q

The greater the concentration of dissolved oxygen in cells are. The ——— the partial pressure is

A

Higher

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7
Q

Haemoglobin affinity for oxygen varies depending on what ?

A

The partial pressure of oxygen

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8
Q

What happens to haemoglobin when there is :
Low pO2
High pO2

A 
Low pO2 -
Oxyhaemoglobin unloads its oxygen 
Haemoglobin has low affinity for oxygen 
(Releases oxygen rather than combining with it)
Less saturated with o2

High pO2
Oxygen loads onto haemoglobin to form oxyhaemoglobin
Haemoglobin has high affinity for oxygen
(It will more likely readily combine with oxygen than release it)
Haemoglobin saturated with O2`

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9
Q

What happens to oxygen at respiring cells

A

When cells respire they use up oxygen
Low pO2
Oxygen readily unloads from haemoglobin

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10
Q

What do dissociation curves show ?

A

How saturated haemoglobin is with oxygen at any particular partial pressure

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11
Q

Why is it that when pO2 is high haemoglobin has a high saturation of oxygen and when pO2 is low haemoglobin has low saturation of oxygen

A

Haemoglobin has high affinity for oxygen so it’ll readily combine with oxygen.

Haemoglobin has low affinity for oxygen so it releases oxygen rather than combine with it

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12
Q

At the lowest point of the graph:

Why is it difficult for the haemoglobin to combine with the 1st oxygen molecule

A

Due to the shape of the haemoglobin

4 polypeptides of haemoglobin are closely united

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13
Q

Why is the dissociation curve s shaped

A
  1. At the lowest point of the graph
    Haemoglobin has low affinity for oxygen - slow increase in saturation as pO2 increases
    As 1st oxygen molecule combines with haemoglobin
    - shape alters , more subunits exposed to oxygen, makes it easier for other o2 molecules to join
    -haemoglobin has higher affinity for oxygen (loads quickly)
  2. Rate of saturation increases as pO2 increases (shallow gradient)
  3. After 3rd molecule - haemoglobin saturated
    Harder for 4th molecule to bind as majority of sites occupied
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14
Q

When the curve is steep (2nd stop) a small chnage in the pO2 can cause a

A

Big change in amount of oxygen carried by Hb

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15
Q

Why does haemoglobin rarely achieves 100% saturation of oxygen ?

A

It’s very difficult for 4th oxygen molecule to bind

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16
Q

Why do different haemoglobin molecules have different affinities for oxygen ?

A

Different haemoglobin molecules have different sequences of amino acids
Slightly different shapes

17
Q

Haemoglobin gives up its oxygen more readily at ——- partial pressures of co2

A

Higher

18
Q

What is the purpose of haemoglobin having lower affinity for O2 at higher pco2

A

So more oxygen will readily unload into respiring tissues

Rapid respiration

19
Q

What does carbon dioxide actually do ?

A 
High pco2 lowers pH because dissolved co2 is acidic 
This causes Haemoglobin to change shape 
Reduced affinity for oxygen 
More oxygen unloaded 
More oxygen for muscle and tissues 
Dissociation curve shifts to the right
20
Q

What does a shift to the left

A

Left - haemoglobin has higher affinity for oxygen
More oxygen is readily loaded at the lungs at lower pO2
Dissociates less readily
Advantageous to organisms living under ground, high altitudes or foetuses

21
Q

What does the curve shifting to the right mean ?

A

Haemoglobin has reduced affinity for oxygen
Oxygen is more readily unloaded to respiring cells at higher partial pressure
Associates (readily unloads) less

22
Q

What is bohr effect

A

The greater the co2 conc the more readily the haemoglobin can unload

23
Q

What type of haemoglobin does organisms that live in environments with low conc of oxygen

A

Haemoglobin with higher affinity for oxygen

Curve to the left

24
Q

What type of haemoglobin do organism who are very active and have high oxygen demand

A

Haemoglobin with lower affinity

Curve to right

25
Q

What other factors affect the affinity for hb

A

Increasing temp

Decrease in ph

26
Q

Why is the pO2 in placenta low

A

Mothers blood travels to the lungs to the placenta

Blood loses oxygen along the way

27
Q

What is the foetal haemoglobin like and what is the advantage of this

A

Has higher affinity for oxygen

More oxygen loaded
At lower pressure
Oxygen can move from mother to foetus

28
Q

Why after birth, the foetus haemoglobin being replaced by adult haemoglobin an advantage

A

Lower affinity for oxygen
At high pressure
More oxygen can readily be unloaded to respiring muscles and tissues

29
Q

What is the effect of a low partial pressure at high altitude of air on percentage saturation of hb ?

A

It will be lower

30
Q

At high altitude the partial pressure in air decreases
Lowers pO2 breathed into lungs
What will body do short term and long term

A

Heart rate increases
Breathing rate increases
Deeper breaths

Long term - produce more red blood cells

31
Q

Explain what happens to haemoglobin in high altitudes

A

High altitudes have lower partial pressure of o2
Higher saturation
Enough o2 supplied to cells and tissues

32
Q

Explain the difference cue between haemoglobin of small animals and larger animals

A

Larger mammals - curve more to left
Higher affinity for oxygen
Steeper

Small animals-
Need more respiration 
Curve to the right 
High sa to vol ratio
Lose heat
33
Q

What does temp do ?

A

Curve to the right
Decreased affinity
More readily unload

34
Q

What is myoglobin ?

A

Like haemoglobin but with only one haem group
It is found in muscle cells
Acts as oxygen reserve
So muscle cells can avoid anaerobic respiration

35
Q

What does myloglobin have ?

A

A very high affinity for oxygen even at low partial pressure

Oxyhaemoglobin will only dissociate at very low partial pressure

A Level Biology (16 decks)

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