cie a level biology - gas exchange

8/17/2019 CIE A level Biology - Gas Exchange

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The gross structure of the human gas exchange system


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Plan diagrams of the structure of the walls of the trachea, bronchi,

bronchioles


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Cartilage: provides support and prevents the tubes collapsing when the air pressure

inside them is low.

Ciliated epithelium: found lining the trachea, bronchi and some bronchioles. Single

layer of cells including cilia and goblet cells

Cilia: sweep mucus upwards towards the mouth → prevent dust particles and bacteria

reaching the lungs.


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Goblet cells: secrete mucus → trapping dust particles and bacteria.

Smooth muscle: found in the walls of the trachea, bronchi and bronchioles. This type of

muscle can contract slowly but for long periods without tiring. When it contracts, it

reduces the diameter of the tubes. During exercise it relaxes, widening the tubes somore air can reach the lungs.

Elastic fibres are found in the walls of all tubes and between the alveoli.

Stretching → alveoli and airways expand to contain more air

Recoiling → reducing volume of alveoli, expelling air more eciently

Gas exchange at the alveolar surface

- The air inside an alveolus contains a higher

concentration of !, and a lower concentration of

"!, than the blood in the capillaries.

- This blood has been brought to the lungs in the

pulmonary artery, which carries deoxygenated

blood from the heart.

- ! therefore diffuses from the alveolus into the

blood capillary, through the thin walls of the

alveolus and the capillary. "! diffuses from the

capillary into the blood.

The diffusion gradients for these gases are maintained by:

# breathing movements (inhaling and exhaling), which draw air from outside

the body into the lungs, and then push it out again → maintains high

concentration of ! and low concentration of "! in the alveoli

# $ood blood supply: bringing deoxygenated blood % carrying awayoxygenated blood.

# Short distance of diffusion: single layer of s&uamous epithelium 'alveoli(

and single layer of endothelium 'capillaries(# )arge surface area to volume ratio# *any alveoli

S!"#$G

"omponent ofsmo+e

ffect Signs %Symptoms

Disease


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Tar Stic!s to the surface ofbronchioles → paralyses cilia

"ontains carcinogens

"oughingreathlessness

ncreases chanceof infection

"hronic bronchitismphysema

"ancer

"arbonmonoxide inds irreversibly to /bDamage lining of arteries reathlessness0atigue "/DStro+e

1icotine - 2ddictive 'releases dopamine(

- Stimulate nervous system" Reduces diameter of arteriole →less blood to extremities

- 3eleases adrenaline- ncreases blood pressure %heart rate

- ncreases li+elihood of bloodclotting

Di44iness

"raving

/igh blood pressure

"/DStro+e

Effects of smo%ing on the gas exchange system

Chronic obstructive pulmonary disease (COPD)

This is a condition in which a person has chronic bronchitis and emphysema. t can be

extremely disabling.

Chronic bronchitis

# "ilia paralysed % *ore mucus

secreted# #ucus builds up → bloc! alveoli →

gas exchange more dicult (greater

di$usion distance between the air in the

alveoli and the blood in the capillaries).

# *ucus traps bacteria, causing

infection and inflammation of the trachea,

bronchi and bronchioles 'bronchitis&

# The mucus stimulates persistent

coughing, which can damage the tissues in

the walls of the airways, ma+ing them

stiffer and the airways narrower.

Emphysema

# Smo+ing causes inflammation in thelungs.


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# %ncreases numbers of white blood cells → secrete chemicals that damage

elastic &bres.

# 2lveoli become less elastic and burst, resulting in larger air spaces.# This reduces the surface area available for gas exchange.

Lung cancer

"arcinogens cause mutation in the genes of the lung cells.

Some of these mutated cells begin to divide uncontrollably, forming tumour 'cancer(

)ung cancer can spread to other part of the body 'metastasis( because there is a good

supply of blood in the lungs

Effects of smoking on the cardiovascular system

# 1icotine stimulates the nervous system.# /igh heart rate and blood pressure# 2rteries become damaged due to high blood pressure# 'hite blood cells gather build"up plaues and blood clots

# *lood clot brea!s, preventing blood passing through → stro!e, heart attac!

# The loss of elasticity in an artery or arteriole also ma+es it more li+ely that

the vessel will burst when high-pressure blood

pulses through.


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'E(#E) *+EST#!$S

GS E-C.$GE

/ large, thic%0walled blood vessel lies alongside a bronchus1

)hich row names the vessel and describes its contents2

3 The diagram shows part of the wall of a bronchus in cross0section1


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4 The table shows the presence or absence of ciliated epithelium and goblet

cells in airways1

)hich row describes a bronchiole2

5 Two airways each have smooth muscle in their walls, but only one has

cartilage1

)hat are the airways2


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alveolus and bronchus

6 alveolus and trachea

C bronchiole and bronchus

7 bronchus and trachea

8 The mucus secreted into the airways is a solution of the glycoprotein mucin1

)hich statement about mucin contains a mista%e2

"arbohydrate chains ma+e mucus stic+y enough to trap dust particles.

6 *ucus is secreted by goblet cells by the process of endocytosis.

C "arbohydrate chains are added to protein in the $olgi apparatus of goblet cells.

7 *ucus is moved over the surface of the airways by the action of ciliated cells.

9 carbon dioxide molecule dissociates from haemoglobin and diffuses along

the shortest path into an alveolus1

ssuming that the molecule diffuses through a gap in a capillary wall, how

many phospholipid bilayers did the molecule pass through2

!6 5

C 6

7 7

)hat maintains the diffusion gradient for the diffusion of oxygen out of an

alveolus2

/ binding of oxygen with haemoglobin to form oxyhaemoglobin

3 blood flow bringing a new supply of red blood cells

4 increased surface area of red blood cells as they are forced through narrow capillaries

5 complete replacement of the air in the alveolus with each breath

8, ! and 5 only

6 8, ! and 6 only

C ! and 5 only

7 5 and 6 only

; )hat are the adaptations of an alveolus for its role in gas exchange2


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/ very thin epithelial walls

3 close contact of walls and capillaries

4 walls with elastic fibres which recoil after stretching, to help force air out

5 stiff walls to prevent collapse of the alveolus when breathing out

8, ! and 5 only

6 8, ! and 6 only

C 8 and ! only

7 5 and 6 only

< )hich event occurring at an alveolus does not re=uire a red blood cell2

carbon dioxide dissociates from carbaminohaemoglobin

6 carbon dioxide is formed from hydrogencarbonate ions

C carbon dioxide diffuses from the blood into an air space

7 oxygen binds with haemoglobin to form oxyhaemoglobin

/> easurements of an adult?s breathing show that at rest:

# the volume of air in a single breath is 799cm5# 579 cm5 of each breath reaches the alveoli# !799 cm5 of air remain in the lungs after breathing out.

)hich is not a correct conclusion from these measurements2

2bout one sixth of the air in the lungs is replaced by breathing out and then in.

6 2lmost one third of each breath does not reach a gas exchange surface.

C )arge changes in the composition of the air in the alveoli do not occur.

7 The volume of air in the alveoli after breathing in is 5.9dm5

S!"#$G

/ Tar in cigarette smo%e contains carcinogens and is mostly deposited in the

bronchi1

)hat is the effect of these carcinogens2

cause mutations in bronchial epithelial cells

6 destroy the cilia in the bronchi

C stimulate goblet cells to produce more mucus


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7 reduce the diameter of the bronchi

3 )hich component of tobacco smo%e binds with haemoglobin to form

carboxyhaemoglobin2

carbon monoxide

6 carcinogens

C nicotine

7 tar

4 )hat is not a symptom of emphysema2

alveoli burst

6 alveoli lose elastic fibres

C bronchi are bloc+ed by tumours

7 the total surface area of the alveoli is reduced

5 Two lifelong cigarette smo%ers, - and @, both have persistent coughs1 - also

has difficulty breathing out and @ is getting much thinner1 Arom these

symptoms it is possible that:

has bronchitis and ; has emphysema.

6 has emphysema and ; has chronic obstructive pulmonary disease.

C has chronic obstructive pulmonary disease and ; has lung cancer.

7 has lung cancer and ; has bronchitis.

8 6oth carbon monoxide and nicotine are absorbed into the blood from tobacco

smo%e1

)hat describes their effects on the body2


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9 )hat is the se=uence of events leading to atherosclerosis2

/ blood clot forms at site of pla&ue

3 phagocytes attracted to site of damage

4 low density lipoproteins transport cholesterol to artery

5 damage to the lining of an artery

8 atheroma builds up and brea+s through the endothelium

+ → → - → → /

6 → - → / → + →

C → → - → / → +

7 / → + → → → -

)hich of the following explains the increased ris% of stro%e, caused by

smo%ing tobacco2

" increases the blood pressure and increases the chance of a blood vessel in the

brain bursting.

6 "arcinogens increase the blood pressure and increase the chance of a blood vessel in

the brain bursting.C 1icotine increases the chance of a blood clot bloc+ing a blood vessel in the brain.

7 Tars increase the chance of a blood clot bloc+ing a blood vessel in the brain.

; )hich observation is experimental evidence that smo%ing tobacco causes

lung cancer2

*ost people who develop cancer are smo+ers.

6 Death rates from lung cancer are highest in people who smo+e more than !7

cigarettes per day.

C )ung cancer was a rare disease until smo+ing became common in the !9th century.

7 When substances extracted from tar in cigarette smo+e were painted onto the s+in of

mice, the mice developed tumours.

< )hich dietary factors increase the ris% of coronary heart disease2

high inta+e of fruit and vegetables

6 high inta+e of saturated fat and cholesterol

C low inta+e of sodium chloride and alcohol


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7 moderate inta+e of unsaturated fat

/> )hat would not form part of an effective screening programme for C.72

screening for high blood pressure

6 screening for high cholesterol

C monitoring heart rhythms

7 screening blood samples for bacterial infection

nswers to gas exchange =uestions

/1

31 6

41 C

51 C

81 6

91 6


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1

;1

1 7

nswers to smo%ing =uestions

/1

31

41 C

51 C

81

91 C

1 C

;1 7

1 7

cie a level biology - gas exchange

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