Gas Exchange Flashcards
For gas exchange to be effective the SA:V ratio must be…
Large
The larger the organism gets….
…the SA to volume ration decreases
How do you calculate SA:V ratio
Calculate surface area by length x width
Calculate volume length x width x height
Do surface area divided by volume
What is Fick’s law
Rate of diffusion = surface area x concentration gradient
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Diffusion distance
What makes a good exchange surface
Large surface area
Large concentration gradient
Thin exchange surface
To limit water loss insects may have….
Waterproof covering
Small surface area to volume ratio to minimise area over which water is lost
Describe the movement of oxygen through the insect
Oxygen enters the insect through spiracles and into the tracheae. Sporades close
Oxygen diffuses through the tracheae into the tracheoles down a conc gradient
Oxygen is delivered directly to the respiring tissues
Why is it good that spiracles can open and close
To control any water loss by evaporation
When do spiracles open
When CO2 level increase
What are tracheae
Network of tubes supported by strengthened rings
Provide tubes full of air so that diffusion is fast
Tracheoles
Small tubes with THIN walls so that the diffusion distance is reduced
Highly branched so that there is a large surface area
Gas exchange in fish
Each fish has 4 gills each side of its head
Water moves in through the mouth and out through the gills
Gills have finger like projections called gill filaments
Each filament has many lamellae at 90 degrees to increase surface area
Structure of a leaf
Cuticle
Upper epidermis cells
Palisade mesophyll cells
Spongy mesophyll cells
Stomata air space
Lower epidermis cell
Guard cell
Stoma
Adaptations of leaf for gaseous exchange
Flat - gives larger surface area to volume ratio
Many stomata - pores to allow air to move in and out of leaf
Air spaces in leaf so short distance between mesophyll cells and air
Adaptations of plants to reduce water loss
Guards cells close the stomata at night to reduce water loss
Less co2 required due to lack of sunlight for photosynthesis
Upper and lower surfaces have a waxy cuticle
Adaptions of xerophytic plants to reduce water loss
Reduced amount of stomata - less surface area for water loss
Stomata in pits - reduced conc grad
Hairs to trap water vapour - reduced conc grad
Rolled leaves - reduced conc grad
Leaves reduced to spines - less surface area for water loss
Thick waxy cuticles - increased diffusion distance
How does oxygen move through the insect?
- Oxygen diffuses in through the spiracles;
- Spiracle closes;
- Oxygen moves through the trachea into the tracheoles;
- Oxygen delivered directly to the respiring tissues;
Explain three ways in which an insect’s tracheal system is adapted for efficient gas exchange.
- Tracheoles have thin walls so short diffusion distance to cells
- Highly branched tracheoles so short diffusion distance to cells
- Highly branched tracheoles so large surface area
4.Tracheae provide tubes full of air so fast diffusion
Describe and explain the advantage of the counter-current principle in gas exchange across a fish gill.
- Water and blood flow in opposite directions;
- Maintains diffusion/concentration gradient of oxygen OR Oxygen concentration always higher (in water);
- (Diffusion) along length of lamellae/filament/gill/capillary
A fish uses its gills to absorb oxygen from water. Explain how the gills of a fish are adapted for efficient gas exchange.
1 Large surface area provided by many lamellae over many gill filaments;
2 Increases diffusion/makes diffusion efficient;
3 Thin epithelium/distance between water and blood;
4 Water and blood flow in opposite directions/countercurrent;
5 (Point 4) maintains concentration gradient (along gill)/equilibrium not reached;
6 As water always next to blood with lower concentration of oxygen;
7 Circulation replaces blood saturated with oxygen;
8 Ventilation replaces water (as oxygen removed);
Describe the gross structure of the human gas exchange system and how we breathe in and out.
- Named structures – trachea, bronchi, bronchioles, alveoli;
- Above structures named in correct order OR Above structures labelled in correct positions on a diagram;
- Breathing in – diaphragm contracts and external intercostal muscles contract;
- (Causes) volume increase and pressure decrease in thoracic cavity (to below atmospheric, resulting in air moving in);
- Breathing out - Diaphragm relaxes and internal intercostal muscles contract;
- (Causes) volume decrease and pressure increase in thoracic cavity (to above atmospheric, resulting in air moving out);
Describe how carbon dioxide in the air outside a leaf reaches mesophyll cells inside the leaf. (4)
- (Carbon dioxide enters) via stomata;
- (Stomata opened by) guard cells;
- Diffuses through air spaces;
- Down diffusion gradient;
Explain why plants grown in soil with very little water grow only slowly
- Stomata close;
- Less carbon dioxide (uptake) for less photosynthesis/glucose production;
Explain the advantage for larger animals of having a specialised system that facilitates oxygen uptake
Larger organisms have a smaller surface area to volume ratio
Overcomes long diffusion pathways
How do lungs provide an efficient gas exchange surface in human
They have short diffusion distance and a large surface area
What is the trachea
Tube like structure that carries air from the mouth to the lungs
Bronchi
The trachea spilts into two bronchi as it enters the lungs, which allows air to travel to the left and right lung
Bronchioles
Bronchi further divide into smaller branches called bronchioles. These then supply the alveoli with air
How are alveoli adapted for good gas exchange
Many alveoli so Large surface area
Rich blood supply so maintains a large concentration gradient
Alveolar squamous epithelium is one cell thick so thin diffusion distance
Mechanism of breathing when inhaling
External intercostal muscles contract
Pulls the rib cage up and out
Diaphragm contracts and pulls down
Volume increases
Pressure in lungs is LOWER than atmospheric pressure
Air moves into the lungs DOWN a pressure gradient
Mechanism of breathing when exhaling
Internal intercostal muscles contract
Diaphragm relaxes and moves up
Volume decreases
Pressure increases
Air movies out of the lungs down a pressure gradient
How does the oxygen get into the red blood cells
Oxygen passes through the squamous epithelial cell of alveoli
Then through the endothelial cell of the capillary
And then combines with red blood cell
