Exchange And Transport

Question 1

Why is diffusion through outer membrane slow in multicellular organisms

Answer 1

Some cells are deep in the body so large diffusion pathway

Difficult to exchange enough substances to large volume through small outer surface

Question 2

Counter current flow

Answer 2

Blood flows through lamellae in one direction and the water flows over in opposite direction ( maintain favourable conc. gradient)
Conc. of oxygen always higher in water than blood

Question 3

Gill structure and adaptation

Answer 3

Water enters through fish mouth and leaves over the gills
Gill made of gill filament which increases SA
Gill filament covered in lamellae which increase SA
Lamellae have blood capillaries which move any absorbed gas and have thin surface

Question 4

Gas exchange in insects

Answer 4

Have air filled pipes called trachea, air moves to trachea via spiracles
Oxygen travels done the conc gradient towards cells
Trachea branch off into smaller tracheoles which have thin permeable walls and go to individual cells
CO2 moves down conc gradient towards spiracles to realise into atmosphere
Use rhythmic abdominal moments to move air in and out of spiracles

Question 5

Stomata

Answer 5

Allow gas in and out, controlled by guard cells

All cells close to stomata so short diffusion path way

Question 6

Interconnected air spaces

Answer 6

Increase the surface area of mesophyll layer so has can move around mesophyll cells

Question 7

Spongy mesophyll layer

Answer 7

Large surface are of mesophyll cells for max diffusion

Site of gaseous exchange needed for photosynthesis

Question 8

Water conservation in insects

Answer 8

Have rigid exoskeleton, chitin and water proof cuticle
Have small SA:Vol
Open and close spiracles

Question 9

Water conservation in plants

Answer 9

Water enters the guard cell making them turgid opening stomatal pore
Leaves covered in waxy cuticle

Question 10

Xerophytes

Answer 10

Layer of hairs on epidermis to trap moist air around stomata (lower WP)
Rolled leaves with stomata inside to protect from wind (traps water vapour)
Reduced number of stomata

Question 11

Journey of air

Answer 11

Air enters the trachea
Trachea splits into two bronchi, one for each lung
Bronchus then branch into bronchioles
Bronchioles end in alveoli

Question 12

Inspiration

Answer 12

External intercostal muscles and the diaphragm relax moving the rib cage up and outwards and the diaphragm flattens increasing volume of thoracic cavity
Pressure in thoracic cavity decreased so air moves down trachea

Question 13

Expiration

Answer 13

External intercostal muscles and diaphragm relax moving the rib cage down and and inwards and the diaphragm becomes curved
Volume of thoracic cavity decreases causing air pressure to increase and air forced out

Question 14

Forced expiration

Answer 14

The external intercostal muscles relax and the internal intercostal muscles contract pulling the ribcage further down

Question 15

Alveoli

Answer 15

300 million in each lung and gsve 70m2 surface area
Alveolar epithelium is only one cell thick
O2 diffuses out alveolar and capillarity endothelium into haemoglobin in blood

Question 16

Pulmonary ventilation

Answer 16

Overall flow of air into lungs in 1 minute

=tidal volume X breathing rate

Question 17

Expiratory reserve volume

Answer 17

Volume of maximal exhalation after normal exhalation

Question 18

Residual volume

Answer 18

Volume remaining in the lungs after maximal exhalation

Question 19

Inspiratory reserve volume

Answer 19

Additional volume that can be inhaled after inhalation of tidal volume

Question 20

Vital capacity

Answer 20

Maximum volume of exhalation after lungs are maximally filled

Question 21

Tuberculosis

Answer 21

When infected by TB immune system builds tubercles, WBC fight infection scarring tissue
Reduced tidal volume so breath faster to get enough oxygen
Symptoms: persistent cough, coughing blood, chest pain, short breath and fatigue

Question 22

Pulmonary fibrosis

Answer 22

Formation of scar tissue in lungs (result of infection or asbestos)
Scar tissues is thicker and less elastic so reduction in amount of oxygen diffusion and less lung expansion
Symptoms: shortness of breath, dry cough, chest pain, fatigue and weakness

Question 23

Asthma

Answer 23

Allergens stimulate WBC in bronchi which release histamine which makes muscles around bronchioles contract
Airflow reduces so less oxygen enters alveolis
Symptoms: difficulty breathing, wheezing, tight chest, coughing

Question 24

Emphysema

Answer 24

Caused by smoking or long term exposure air pollution
Foreign particles become trapped in alveoli causing inflammation attracting phagocytes
Phagocytes produce enzyme that breaks down elastin and leads to destruction of alveoli walls
Symptoms: bluish skin, chronic cough, wheezing shortness of breath