LUNGS / GAS EXCHANGE

infection of lungs with Mycobacterium tuberculosis result in range of

symptoms.

symptoms

severe breathing problems,

a persistent cough

coughing up blood.

A tubercle =

solid mass of dead tissue, macrophages + bacteria

Using information in the photograph and your knowledge of gas exchange

surfaces, suggest why this infection can result in these symptoms.

(4)

alveoli

destroyed by tubercle

tubercle reduced

SA of lungs

gas exchange reduced, less O2 to blood ==>

breathing problems

coughing due to irritation / removing dead tissue

blood coughed,

due to damage of lung / blood vessel

Give one difference

between structure of a capillary + structure

of a vein?

(1 mark)

capillary wall = one cell thick

vein wall = thicker

capillary no valves + muscles

These gases will diffuse at different rates.

15% oxygen

5% carbon dioxide

8% oxygen

7% carbon dioxide

Alveolus

Capillary

Using info in diagram,

explain difference in the rate of diffusion of gases?

(2 marks)

O2 diffuses > quickly than CO2

diff concentration gradients

higher conc

gradient for O2.

law represented by following formula.

Rate of diffusion = proportional to surface area × difference in concentration /length of diffusion pathway

Using info given in question + own knowledge, explain

how rapid gaseous exchange takes place in a mammal?

(5)

larger surface area provided by alveoli

larger surface area provided by capillary network

concentration gradient maintained by ventilation

concentration gradient maintained by mass flow

small diffusion pathway because alveoli =

thin walls

capillaries thin walls +

one cell thick

Hb / RBC carry 02

Using info in graph,

compare types of antibiotics + combinations of antibiotics that Mycobacterium tuberculosis resistant to in 2006 with 2007?

(3 marks)

bacteria resistant

to fewer antibiotics + in

2006 than 2007

both years are resistant strains to streptomycin

/ INH + rifampicin + ethambutol / INH

resistant strains to INH + rifampicin

in 2006 but not in 2007 ;

resistant strains to {ethambutol /

rifampicin} in 2007

but not in 2006

% of strains of Mycobacterium tuberculosis resistant to antibiotic INH increased during three years.

Suggest how natural selection could resulted in this increase?

(3)

bacteria

= mutation in DNA

resistance

presence of INH acts as selection pa

ALLELE / not gene

for resistance passed on

bacteria divide by binary fission

increasing allele frequency

more resistant bacteria

Suggest how hospitals

could prevent increase in percentage of strains

of Mycobacterium tuberculosis resistant to antibiotics?

(2)

educating patients about taking antibiotics /

taking the full course of antibiotics

hand washing / screening /

appropriate antibiotics given

Describe +

explain how lungs of a mammal are adapted for rapid gas

exchange.

(5)

alveoli = one cell thick

walls of capillaries + endothelium = one cell thick

short diffusion distance

alveoli covered with capillaries

large surface area provided by capillaries / alveoli

conc gradient maintained by ventilation / breathing

lots of RBC, oxygen

combines with Hb,

Daphnia =

circulatory system with heart

--> pumps blood into cavities

surrounding organs.

photograph below shows location of heart in Daphnia

i)

Suggest how heart of Daphnia enables organs to carry effective

gas exchange?

(2 marks)

pumps blood

carries 02

blood moving maintains

conc gradient

mass flow

organs have ==>

large SA to volume ratio

in mammals,

blood passes through heart

twice for each circulation of body.

Suggest

how type of circulation enables mammals

to carry out effective gas exchange?

(3 marks)

one side of heart

transports blood to lungs

other side transports to body

lower blood pa to lungs

higher blood pa to body

seperation of

oxygenated + deoxygenated blood

maximises supply of 02 to body cells

need for good supply of 02 in mammals

maintaining conc gradient

(b)

Explain why people with cystic fibrosis have breathing difficulties?

(4 marks)

thicker mucus

blocks trachea + airway

cilia unable to move

mucus out lungs

reduced flow of 02 to alveoli

reduced conc gradient for 02 / C02 in alveoli

loss of surface area

reduced gaseous exchange

Give two structural differences between cellulose + starch?

(2 marks)

alpha glucose in starch

beta glucose in cellulose;

starch / amylopectin} can be branched /

cellulose only a linear molecule

starch contains two types of molecule, cellulose

only one ;

Suggest how Buffenstein and Horsby introduced

cancer-causing genes into cells

from naked mole rats?

(3 marks)

(cancer causing) gene identified / eq ;

2. gene {cut / isolated / eq} from DNA / eq ;

3. using a {restriction / eq} enzyme / eq ;

4. gene in {vector / named vector} ;

5. mechanism for getting {gene / vector} into host

cells (of naked mole rats)

we had to breathe the 'rank air' found in the tunnels of naked mole rats, it would

leave us 'gasping for air'

.

Describe how mechanism involved in control of breathing rate in humans would respond to 'rank air'?

(5)

air = higher CO2 content

CO2 level in blood increases

pH of blood falls

change detected by chemo receptors in

carotid artery + aorta in medulla

ventilation centre in medulla

sends more impulses along neurones

to intercostal muscles + diaphragm

cause increased ventilation rate /

increased

rate of breathing