Exchange and Transport Flashcards
What maintains the diffusion gradient of gases in + out of a cell?
Mitochondria have lowest conc of O2 + highest conc of CO2
Why do large organisms have internalized gas exchange systems?
They have small surface area to volume ratio
Why don’t small organisms have internal exchange systems?
Have a large surface area to volume ratio
What three ways do insects minimize water loss?
- Waterproof shell
- Small surface area
- Close spiracles
How does Oxygen reach the cells of an
Insect?
- enter into spiracle
- diffuses through trachea + tracheoles down conc gradient
- abdominal muscles contract for ventilation of air to maintain conc gradient
How is diffusion kept efficient between the tracheoles + surrounding cells?
Every cell very short distance from tracheoles
Describe the two main structures in fish gills
Gill filaments + lamellae on them
What is countercurrent flow?
Water flows in opposite direction to blood in the gill lamellae
What is the purpose of the gill lamellae?
Increase surface area for gas exchange
How is a steep diffusion gradient maintained in fish?
Ventilation of oxygen
Mass transport of O2 carried away from gills by blood
Explain how the countercurrent flow creates a diffusion gradient across the whole length of the gill lamellae
- O2 blood meets water that has max O2 = diffusion
- no O2 blood meets water that still has some O2 left = diffusion
What would happen if the blood + water flowed in the same direction across the gill lamellae?
Gas exchange reaches equilibrium + diffusion only occurs across part of gill lamellae
Why is countercurrent flow important in the gas exchange in fish?
Maintains a concentration gradient for diffusion across the whole length of gill lamellae
What is the purpose of the tracheoles?
Thin + permeable walls = short diffusion distance to surrounding cells
Oxygen still diffuses into the leaf when it is dark, why?
It’s constantly being used by cells in respiration
Why are the diffusion gradients maintained in the leaf?
Mitochondria respiring + chloroplasts photosynthesis
How does the structure of the leaf allow for efficient gas exchange?
- Cells close to external air, flat leaf
- diffusion in gas spaces = quicker than in water
Why does the leaf have no specialized gas exchange system?
Large surface area to volume ratio
What adaptations does a leaf have for rapid diffusion?
- thin + flat = SA + cells not far from external air
- stomata on underside of leaf
- interconnecting air spaces in mesophyll
What do plants do to control gaseous exchange and water loss?
Guard cells close stomata
What two factors determines whether a large organism has an internalized gas exchange network?
- if the SA:V ratio is small
- how active organism is
What are 3 features of transport systems in large organisms?
- Blood to carry materials
- Tubular vessels that contain blood + distribute
- Valves to ensure movement in one direction
Why does the oxygenated blood return back to the heart from the lungs instead of just circulating round the rest of the body?
Low pressure after lungs = too slow
Why do the substances + gases in the blood need to be delivered to cells in mammals quickly?
Mammals have a high body temp => high metabolism
What basic structure of layers do all arteries, arterioles and veins have + what is the purpose of each layer?
- tough outer layer: pressure
- muscle: contract
- elastic: stretch/recoil, pressure
- endothelium: friction
- lumen: carries blood
Which vessel carries out exchange of material?
Capillaries
How do the proportions of an artery differ to veins and relate to its function?
- thicker muscle layer than veins = constrict blood flow to arterioles
- thicker elastic layer than veins = stretch + recoil + smooth/high pressure smooth
- thick wall = pressure bursting
- no valves = high pressure
How does the structure of an arteriole differ to an artery + link to its function?
- thicker muscle layer: vasoconstriction
- thinner elastic layer: pressure is lower
How does the structure of a vein link to its function?
- thin muscle layer: carrying blood away from tissues
- thin elastic layer: pressure too low
- thin wall: flattened easily = aid flow of blood
- valves: prevent back flow
How does the structure of the capillaries link to their function?
- endothelium layer = short diffusion distance
- branched = SA
- narrow diameter = permeate tissues
- narrow lumen = blood cells flat
- spaces in endothelial = white blood cells escape
Name 3 substances tissue fluid contains
Amino acids, glucose, oxygen
What is hydrostatic pressure?
- Pressure created by the blood moving from the arteries, arterioles, to capillaries
- forces tissue fluid out of blood
What two forces oppose the movement of tissue fluid out of the capillaries?
- hydrostatic pressure of tissue fluid
- lower water potential of blood (few proteins)
What type of filtration occurs at the arteriole end of the capillary?
Ultrafiltration (large molecules left in blood)
Why does tissue fluid return to the venous end of the capillary?
- lower hydrostatic pressure inside capillary than surrounding tissue fluid
- low water potential because of many proteins in blood = gradient = osmosis
How is the composition of the tissue fluid different when it returns to the capillaries?
CO2 + waste materials from cells
What two forces move the tissue fluid through the lymphatic system to the heart?
Hydrostatic pressure + contraction body muscles
Why don’t red blood cells + plasma proteins move out of the capillaries?
Too large
