Gas Exchange

Question 1

Pulmonary ventilation equation (volume of air breathed in or out in one minute)

Answer 1

Tidal volume (volume of air breathed in per breathe at rest) x breathing rate (number of breaths per minute)

Question 2

Ventilation mechanism of a fish and structure of gills for efficient gas exchange

Answer 2

Many lamellae, secondary lamallae
Counter current system of blood and water, equilibrium never reached, concentration gradient maintained across entire lamallae
Large number of capillaries, maintains gradient by removing oxygen
Thin epithelium of capillaries
Pressure changes (opening and closing mouth) to bring in more water/ maintain gradient

Question 3

Insect gas exchange system

Answer 3

Spiracles, trachea, tracheoles
Spiracles allow diffusion of oxygen/ oxygen diffuses though trachea/ tracheoles
Tracheoles are highly branched so large surface area for exchange
Tracheole walls are thin so short diffusion pathway/ tracheoles enter cells so short diffusion pathway
Tracheole permeable to oxygen/air
Cuticle/chitin/exoskeleton impermeable so reduce water loss
Spiracles can close so no/less water loss/ spiracles have valves so reduced water loss
Hairs around spiracles reduce water loss
Rhythmic abdominal movements

Question 4

Gas exchange in leaves of dicotyledonous plants (mesophyll and somata)

Answer 4

Mesophyll cells have large surface area
Stomata can open and close to balance between regulating water loss and gas exchange

Question 5

Layers of leaf

Answer 5

Waxy cuticle
Upper epidermis
Palisade mesophyll tissue
Spongy mesophyll
Lower epidermis
Waxy cuticle

Question 6

Adaptations of leaf

Answer 6

Broad
Palisade layer has lots of chloroplasts
Upper epidermis is transparent
Xylem and phloem form network of vascular bundles which provide less with water for photosynthesis and take away glucose produced and add support
Epidermal tissues covered with waxy cuticle to reduce water loss by evaporation
Lower epidermis has lots of stomata
Spongy mesophyll tissue contain air spaces which increase rate of diffusion of gases into and out of the leaf’s cells

Question 7

Plant adaptations to extreme environments (heat)

Answer 7

Small leaves/ spines instead of leaves to reduce surface area for water loss by evaporation
Curled leaves/ hairs to reduce air flow
Thick waxy cuticles
Thick fleshy stem to store water
Fewer stomata/only open at night
Stomata sunken in pits

Question 8

Insects controlling water loss

Answer 8

Close spiracles using muscles
Waterproof waxy cuticle
Tiny hairs around spiracles

Question 9

Mechanism of breathing in

Answer 9

Diaphragm contracts and flattens
External intercostal muscles contract and rib cage moves up and out
Volume increase and pressure decrease in thoracic cavity (to below atmospheric pressure)
Active process

Question 10

Mechanism of breathing out

Answer 10

Diaphragm relaxes and moves up/becomes curved again
External intercostal muscles relax and rib cage moves down and in
Volume decreases, pressure increases in thoracic cavity (to above atmospheric pressure)
Passive process

Question 11

Forced expiration

Answer 11

External intercostal muscles relax and internal intercostal muscles contract, pulling the rib cage further down and in
Antagonistic muscles

Question 12

Tidal volume

Answer 12

Volume of air in each breath

Question 13

Ventilation rate

Answer 13

Number of breaths per minute

Question 14

Forced expiratory volume

Answer 14

Maximum volume of air that can be breathed out in one second
Bronchioles

Question 15

Forced vital capacity

Answer 15

Maximum volume of air it is possible to breathe out forcefully out of the lungs after a deep breath in
Lungs

Question 16

The volume of water passing over the gills increases if the temperature of the water increases. Suggest why

Answer 16

Increased metabolism/ respiration/ enzyme activity
Or
Less oxygen dissolved in water

Question 17

A rise in the temperature of water decreases the amount of oxygen dissolved in the water. As the water temperature rises, the rate of ventilation in a fish also rises. Explain the advantage of this

Answer 17

Metabolic rate/ respiration increases with an increase in temperature so more oxygen is required
To provide same amount of oxygen, need to have more water flowing over gills

Question 18

Reduced elasticity of the lungs causes breathing difficulty. Explain how

Answer 18

Alveoli/ lungs won’t inflate/ deflate fully/ reduced lung capacity
Breathing out particularly affected, no longer passive
Reduces conc grad

Question 19

Describe the difference in the composition of gases in inhaled and exhaled air and explain how these differences are caused

Answer 19

Inhaled air contains more oxygen than exhaled air
Exhaled contains more carbon dioxide than inhaled
When air is inhaled into the alveoli, oxygen diffuses down its concentration gradient into the capillaries while carbon dioxide in blood returning to lungs from body diffuses down its concentration gradient from the capillaries to alveoli
Inhaled air contains less water vapour
Relative amount/ percentage of nitrogen also changes
Water vapour diffuses from moist surface pf mouth and lungs

Question 20

People who have been fire breathers for a longtime often find they cannot breath out properly, explain why

Answer 20

Inhaled mist causes scar tissue (fibrosis) to form
Scar tissue is thicker and less elastic
Elastic recoil reduced

Question 21

In coeliac disease, the cilia are damaged. Although people with this disease can digest proteins, they have low concentrations of amino acid in their blood
Explain why

Answer 21

Reduced surface area so less absorption
Membrane bound enzymes less effective so proteins not digested
Cell membranes damaged so fewer/ less effective carrier/ channel proteins
Carrier/ channel proteins damaged so less absorption

Question 22

Describe how humans breathe in and out

Answer 22

Diaphragm contracts and flattens
External intercostal muscles contract amd rib cage moves up and out
Volume increase in thoracic cavity to below atmospheric pressure
Diaphragm relaxes and moves up
External intercostal muscles relax and ribcage moves down and in
Volume decrease and pressure increase in thoracic cavity to above atmospheric pressure

Question 23

Describe how the structure of the insect gas exchange system:
Provides cells with sufficient oxygen
Limits water loss

Answer 23

Spiracles, trachea, tracheoles
Spiracles allow diffusion of oxygen or diffusion of oxygen through trachea/ tracheoles
Tracheoles are highly branched so large surface area for exchange
Tracheole walls thin so short diffusion pathway to cells or highly branches so short diffusion pathway or tracheoles enter cells so short diffusion pathway
Tracheole permeable to oxygen/ air
Cuticle/ chitin/ exoskeleton impermeable so reduces water loss
Spiracles can close so no/ less water loss or spiracles have valves (same reasoning)
Hairs around spiracles reduce water loss