Paper 1 - Sa Vol And Gas Exchange Flashcards
Gill structure of a fish
- Lots of gill filaments = large SA
- Lots of lamellae = large SA
- Wall of lamellae (epithelium) is one cell thick and the capillary wall (endothelium) also are only one cell thick = short diffusion pathway
- Each lamellae has a capillary bed = rich blood supply - maintains conc gradient
Countercurrent system
Blood flows through the lamellae in one direction and water flows over them in the opposite direction → maintains a steep conc gradient between water and blood along the whole length of gill lamellae
Describe how a leaf is adapted for gas exchange
- Thin shape of leaf = large surface area and short diffusion pathway
- Cells of the spongy mesophyll layer are loosely packed = interconnecting air spaces - large SA
- Many small pores (stomata) isn’t far from cell = short diffusion pathway
Adaptation of the alveoli
300 million alveoli in each lung (so 2 lungs = 600 million) → large diffusion area = rapid diffusion
Wall of each alveolus is 0.3um thick - shorter distance = faster rate of diffusion
Each alveolus is covered by a dense network of capillaries - pumping of blood maintains concentration gradient
Elastic tissue in walls - can stretch to fill lungs with air when inhaling and the recoil when breathing out to expel the CO2 air
Describe what happens when inhaling
External intercostal muscles contract
Ribs move up and out
Diaphragm muscles contract
Diagphragm lowers
Volume of chest increases
Pressure decreases
Air rushes in the lungs
Describe what happens when exhaling
External intercostal muscles relax
Ribs move down and in
Diaphragm muscles relax
Diaphragm is raised
Volume of chest decreases
Pressure increases
Air rushes out of the lungs
What is pulmonary ventilation ?
A measure of the amount of air that’s moved into the lungs in 1 minute
PV = tidal volume x ventilation rate
Structure of insects
Spiracles - gases enter and exit through diffusion, reduces water loss opening and closing and having protective hairs
Trachea - have circular bands of chitin to increase the amount of gas that can diffuse along them
Tracheoles - smaller tubes without chitin in a epithelium
Muscles - contract = mass movement of air in and out of trachea, maintaining conc gradient
Waterproof skeleton made of chitin
More information on tracheoles
- Extend all the way into the muscles to deliver oxygen directly to tissue
- Lots of them (highly branched) = large surface area
- Thin permeable walls = short diffusion pathway
- Water in the ends moves out during exercise by osmosis = increased SA for gas exchange = faster diffusion
Explain what the term affinity means
How easily oxygen will load onto haemoglobin
Explain the direction the curve moves in the Bohr shift, and why this is useful during exercise
The curve moves to the right which lowers the affinity of the Hb = more oxygen will unload to the cells/tissues = more respiration and muscle can continue contracting
Explain the direction the curve moves if an animal is at altitude and why is this useful
The curve moves to the left - Hb has higher affinity for oxygen = more oxygen can load onto Hb at low partial pressure
Explain why small animals have a curve further to the right
High metabolic rate to release heat - replaces heat lost due time large SA:V - curve moves to right = lower affinity for Hb so more oxygen will unload to cells/tissues = more respiration
Explain why a foetus has a curve further to the left compared to the mother
The foetal Hb will have higher affinity for oxygen - oxygen unloaded from mothers Hb will load onto the foetal Hb
Explain how xerophytes are adapted to prevent water loss
- Leaf rolled up - traps air inside
- Thick waxy cuticle - reduces water evaporation from the surface
- Trapped air in the centre with a high water potential
- Hair on lower surface reduce movement of air
- Stomata in pits to trap air with moisture close to the stomata
