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A level Biology - Unit 3 > Haemoglobin > Flashcards

Haemoglobin Flashcards

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1
Q

What is the most specialised role of the blood?

A

The transport of oxygen from the lungs to cells of the body by erythrocytes.

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2
Q

How are erythrocytes specialised?

A

Biconcave shape- max SA and helps squeeze through narrow capillaries.
No nucleus- max amount of Hb and limits life to 120 days.

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3
Q

What is Haemoglobin?

A

The red pigment in red blood cells that carries oxygen. It also gives RBC their colour.

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4
Q

What type of molecule is haemoglobin?

A

A very large globular conjugated protein.

Made up of 4 peptide chains.

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5
Q

What is formed when oxygen binds to haemoglobin?

What is the equation for this?

A

Oxyhaemoglobin.

Hb + 4O2 ==> Hb(O2)4

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6
Q

Are the oxygen levels in the cells low or high when they reach the capillaries in the lungs?

A

Low

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7
Q

How is a steep concentration gradient created between the inside of erythrocytes and air of alveoli?

A

It is created by the low oxygen level in the RBC compared to the high oxygen levels in the air of the alveoli in the lungs.

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8
Q

What is positive cooperativity?

A

When one oxygen molecule binds to a haem group, the molecule changes shape, making it easier for the next oxygens to bind.

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9
Q

How is the steep concentration gradient maintained (between the alveoli and the cells)?

A

A steep conc. gradient stays until all the haemoglobin is saturated with oxygen.

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10
Q

Is the concentration of oxygen lower in the body cells or in the erythrocytes when the blood reaches the body tissues from the lungs?

A

Lower in the body cells

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11
Q

What is partial pressure?

A

The concentration of a chemical when it is one of a mixture of gases.

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12
Q

What is on the axis of an oxygen dissociation curve?

A

Percentage saturation of haemoglobin in the blood is plotted against the partial pressure of oxygen.

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13
Q

What do oxygen dissociation curves represent?

A

They show the affinity of haemoglobin for oxygen.

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14
Q

Why does a small change in partial pressure of oxygen in the surroundings make a significant difference to the saturation of haemoglobin with oxygen?

A

Because when the first molecule of oxygen attaches to haemoglobin, it changes shape so oxygen can be rapidly added to haemoglobin.

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15
Q

Why does the curve level out at the highest partial pressure of oxygen?

A

All the haem groups are bound to oxygen so the haemoglobin is saturated and cannot take up any more.

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16
Q

What happens at high partial pressures of oxygen in the lungs?

A

Haemoglobin in RBC is rapidly loaded with oxygen.

Hb picks up oxygen more easily.

17
Q

What happens at low partial pressures of oxygen in the respiring tissues?

A

Oxygen is released rapidly from the haemoglobin to diffuse into the cells.
Hb does not carry as much oxygen.

18
Q

What happens to the oxygen in the blood when you aren’t very active?

A

Only about 25% of the oxygen is released into the body cells.

19
Q

What is the Bohr Effect?

A

At higher partial pressures of carbon dioxide, haemoglobin gives up oxygen more easily.

20
Q

Why is the Bohr effect important in the body?

A

Because as a result;

1) in active tissues with high pCO2, Hb gives up its oxygen more readily.
2) in the lungs where pCO2 is low, oxygen binds to Hb molecules easily.

21
Q

How does a fetus get the oxygen it needs?

A

Oxygenated blood from the mother runs close to the deoxygenated fetal blood in the placenta.

22
Q

Does fetal haemoglobin have a higher or lower affinity for oxygen than adult haemoglobin?

A

Higher

23
Q

If fetal haemoglobin had the same affinity for oxygen as the mother, what would be the case?

A

Little to no oxygen would be transferred to the blood of the fetus.

24
Q

Fill in the blanks.

As the proportion of CO2 …………… , the oxygen dissociation curve for Hb moves to the …………….. .

A

increases

right

25
Q

Is the curve for fetal Hb to the left or right of the adult Hb curve?

A

to the left of

26
Q

Carbon dioxide is transported from the tissues to the lungs in three ways. What are they?

A

1) Dissolved in the plasma
2) Combined with amino groups in Hb to form carbominohaemoglobin
3) Converted into hydrogen carbonate ions in the RBC

27
Q

Which way is the majority of carbon dioxide transported to the lungs?

A

In the form of hydrogen carbonate ions (HCO3-)

28
Q

What is the equation of the formation of carbonic acid in the red blood cells?

A

CO2 + H2O ===> H2CO3

29
Q

What does carbonic acid dissociate into and what is the equation for this?

A

Dissociates into hydrogen carbonate ions and hydrogen ions.

H2CO3 ===> H+ + HCO3-

30
Q

What enzyme is there high levels of in the red blood cells that catalyses the reaction between CO2 and water to give carbonic acid?

A

Carbonic anhydrase

31
Q

What happens to the negative hydrogen carbonate ions in the erythrocyte?

A

They diffuse out of the erythrocyte down a concentration gradient.

32
Q

What moves into the RBC once HCO3- ions diffuse out, to maintain the electrical balance of the cell?

A

Chloride ions

33
Q

What is the process called when HCO3- leaves the cell and Cl- enters the cell?

A

Chloride shift.

34
Q

How is a steep conc gradient kept to allow more carbon dioxide to enter the erythrocyte?

A

By converting carbon dioxide into HCO3- ions.

35
Q

When does carbonic anhydrase turn carbonic acid back into water and carbon dioxide?

A

When the blood has reached the lungs where there is a low conc of CO2.

36
Q

What happens to the H+ ions in the red blood cell?

A

Haemoglobin acts as a buffer and accepts H+ ions to form haemoglobinic acid.

37
Q

How does carbon dioxide leave the cell to enter the lungs to then be exhaled out of the body?

A

HCO3- ions go back in the RBC
They react with H+ ions to form more carbonic acid
This is broken down by carbonic anhydrase
Free carbon dioxide is released
This CO2 diffuses into the lungs.

A level Biology - Unit 3 (10 decks)

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