Gaseous Exchange Flashcards
What are 4 key features of exchange surfaces essential for rapid exchange?
- large surface area : volume ratio
- thin to allow short diffusion pathway
- selectively permeable
- maintain strap concentration gradient
What is surface area : volume ratio?
The surface area of an organism divided by its volume, expressed as a ratio or decimal.
What happens to the SA:V as the organism increases in size?
The SA:V ratio decreases
What is the exoskeleton of an insect made from?
A hard fibrous material called chitin.
What is the purpose of chitin exoskeleton?
It provides protection and a lipid layer to prevent water loss.
Impermeable to gas so not a good exchange surface.
How do insects exchange gases?
They have a tracheal system (network or tube)
What is tracheae?
Microscopic air filled pipes that are held open by rings of chitin.
What is the purpose of chitin in tracheae?
To prevent the collapse of the air filled tubes
What are tracheoles?
Smaller tubes that branch off the trachea and extend deep into the abdomen, carrying oxygen directly to respiring cells and removing carbon dioxide.
What is the diffusion difference like between the tracheoles and the body cells?
Short diffusion pathway
What are spiracles?
Valve like openings that run the length of the abdomen (pores)
What is the purpose of spiracles?
Oxygen and carbon dioxide in and out via spiracles
Trachea attach to the spitacles
How do gases move into the tracheal system?
- concentration/diffusion gradient
- contraction of muscles around the tracheal system
- ends of tracheoles fill with water
How does the concentration/diffusion gradient enable gases to move in the tracheole system?
As cells respire, they use oxygen in the ends of tracheoles, this causes oxygen to move down the concentration gradient and more atmospheric air enters the tracheal system
How does the contraction of muscles around the tracheal system enable gases to move in the tracheal system
As abdominal muscles contract and relax they squeeze the trachea/tracheoles, speeding up the movement of gas in and out
How does the ends of tracheoles filled with water enable gases to move in the tracheal system?
- during high/intense activity muscle cells respire anaerobically (as O2 levels are low) this produces lactic acid in muscle cells.
- this lowers the water potential of cells and causes water to move from tracheoles into cells by osmosis
- This decreases volume in tracheoles so more air is drawn in
- Also speeds up diffusion of gases as gases diffuse faster in air than in water.
What are adaptations of insects for efficient diffusion?
Large number of tracheoles = large surface area
Tracheoles are thin and short distance between spiracles and tracheoles leads to short diffusion pathway
Use of O2 and CO2 production = steep diffusion gradient
Adaptations of insects to prevent water loss?
Small SA:v ratio where water can evaporate
Chitin- waterproof exoskeleton
Spiracles - where gas enters + water evaporates can open and close to reduce water loss (muscular sphincter)
What is the word equation for respiration?
Oxygen + glucose —> carbon dioxide + water + ATP
What are the purposes of guard cells in a plant?
They open and close the stomata to allow gases to diffuse in/out
How do guard cells open and close?
When they become turgid they bow outwards opening the stomata
When they become flaccid they shrink/shrivel closing the stomata
What are plants adaptations for gaseous exchange?
- Flat to provide a large surface area for the absorption of light/gases
- Stomata pores allow gas to diffuse in and out with a short diffusion pathway
- Mesophyll air space increase surface are for gas exchange and provide a short diffusion pathway
- Epidermis : transparent to allow light absorption
- Guard cells open and close stomata to reduce water loss
What is a xerophyte?
Plants that are adapted to live in areas where water is limited
Name some adaptations which a xerophyte.
- Hairy leaves
- Thick waxy cuticles
- Rolled leaves
- Sunken stomata
- Spines
Why do some xerophytes have a thick waxy cuticle?
They are impermeable so less/no water can escape
Why do some xerophytes have rolled leaves/sunken stomata/hairy leaves?
It traps a region of still air which becomes saturated with water vapour leading to high water potential. this causes a low water potential gradient, by maintaining humidity to prevent water loss
How do spines affect water loss?
Reduce the surface area for evaporation and transpiration
What are the similarities between gas exchange in plants and insects?
Obtain gases they need from air by diffusion down a concentration gradient.
Movement of gases controlled by pore like structure (spiracles/stomata)
What are the differences between gas exchange in plants and insects?
Insect deliver air to cells via a system of tubes that are not present in a leaf
Insect muscle contractions can assist with the movement of air.
How does water enter a fish?
Water is taken in through the mouth and forced out over the gills. They do this by increasing the volume of their mouth to reduce pressure and force out the water.
Where do fish extract oxygen from the water?
Gills are located within the body behind the head in a fill flap. They are made of gill filaments with gill lamellae on their surface at right angles
Describe counter current flow.
Blood flows through gill lamellae in the opposite direction to water flowing over the surface.
How is counter current flow beneficial for fish’s gas exchange
Water always meets blood at a lower concentration which maintains the concentration gradient along the whole gill lamellae surface.
Describe what parallel flow is?
Blood flows through the gill lamellae in the same direction to water flowing over the gills.
Why is parallel flow bad for fish’s gas exchange
Equilibrium is reached half way across the gill lamellae so no net movement of oxygen into the blood.
Why is it easier to extract oxygen from air
Water is more dense than air so requires more energy to push water back out.
What are the two different types of fish?
Bony
Cartilaginous
How do cartilaginous fish do gas exchange?
They have no ventilation mechanism so have to keep swimming in order for oxygenated water to flow over their gills (parallel flow)
RAM VENTILATION
How do bony fish do gas exchange?
Use a ventilation mechanism and counter current flow in gill lamellae
Name all the structures associated with human gas exchange?
- Epiglottis
- larynx
- Trachea
- Lungs
Bronchi - Bronchioles
- Diaphragm
- pleural / chest membrane
- Pleural cavity
- Internal / external intercostals
- Ribs
What type of process is inspiration?
- active
What type of process is expiration
Passive
Describe the process of inspiration.
Ribs move up and out
External intercostals contract
Internal intercostals relax
Diaphragm contracts and flattens
This increases the volume of the thoracic cavity which cause a decline in pressure below atmospheric air
Leading to air being drawn into the lungs
