Gas Exchange Flashcards
What is gas exchange ?
The process by which oxygen reachers cells and carbon dioxide is removed from them
How does gas exchange occur in unicellular organisms like amoeba ?
Extremely large surface area to volume ratio
Gas exchange occurs across the whole surface
Permeable membrane allows diffusion of gas
Specialised gas exchange organs are not required
Diffusion is sufficient to meet the oxygen requirements of the organism
How does gas exchange work in simple multicellular organisms like flatworm?
These organisms have a flattened shape to overcome the problem of an increase in size
This increases their surface area to value ratio and so no cells in the body is far from the surface (short diffusion pathway ) so there is no need for specialised gas exchange organs
They exchange gases directly with the environment via diffusion .
Diffusion across the permeable membrane is sufficient to meet the oxygen requirements of the organism
How is the simple multicellular earthworm undergo gas exchange ?
Developed a tubular shape and it’s restricted to damp environment
Worms secrete mucus to keep the cells of the body surface moist to allow gases to dissolve and diffuse
They have an elongated shape to provide a large surface area to volume ratio
They exchange gases directly with the environment by diffusion across the moisture surface. Blood vessels are close to the body surfaces so gas can diffuse in and out of the blood and then across the cells covering the body surface.
Blood circulate in the vessels this maintains a concentration gradient for diffusion of oxygen into the cells and carbon dioxide out
Blood contains haemoglobin to carry oxygen to body cells
What happens as organisms get larger?
The surface area to volume ratio decreases
Diffusion across body surface is insufficient to provide enough oxygen for organism to survive
Larger organisms are more metabolic active so higher demand of oxygen
Diffusion pathway across body surface is too large and rate of diffusion is too slow
Multicellular organism and needs specialised gas exchange surfaces
They also need a method of circulation to distribute the gases around the body
In order to achieve the maximum rate of diffusion, what should all gas exchange surfaces have?
Thin shorter diffusion pathway
Moist gases dissolve and diffuse
Permeable to gases
Large surface area for diffusion of oxygen and carbon dioxide
Additional features that increase efficiency of gas exchange in organisms with a circulatory system ?
Extensive blood supply and blood circulate to maintain a diffusion gradient
Respiratory pigment like haemoglobin increase the oxygen carrying capacity of the blood
How does air diffuse in to insects?
Add diffusers into the insect through paired holes called spiracles
The spiracles lead to a system of branched lined chitin air tubes called trachea
Why is it important that the spiracles can open and close like valves?
Oxygen needs to diffuse through the spiracles into the trachea and CO2 needs to diffuse out
To reduce water loss
To reduce heat loss from inside the insect
Where does gas exchange take place in insects?
End of tracheal’s are fluid filled and are close to muscle fibres. This fluid is the interface where gas exchange occurs.
It helps to improve efficiency of gas exchange because oxygen dissolves in the fluid and when muscles contract is fluid is drawn into muscle cells
What are the advantages of the tracheal system?
Oxygen is supplied directly to tissues
No respiratory pigment is needed
Oxygen diffusers faster in air than blood
Spiracles closed to reduce water loss
What are the limitations of insect tracheal system?
In larger organisms, the number and length of tracheal tubes needed with significantly increase the organisms weight
The tracheal may become too long for diffusion
Summarise cartilagineous fish
They have a skeleton made entirely of cartilage
They nearly all live in seawater
Just behind the head on each are five gill clefts which open at gill slits
Water is taken into the mouth and is forced through the gill slits where the floor of the mouth is raised
Gas exchange involves parallel flow, i.e. the blood in the capillaries circulate in the same direction as water flowing over the gills
Summarise bony fish
They have an internal skeleton made of bone
Girls are covered with a flap called the operculum
Summarise ventilation when water flows in
The mouth opens
The operculum closes
The floor of the buccal of cavity is lowered
The volume of the buccal cavity increases
The pressure of the buccal cavity decreases
The direction of the water flow is in the buccal cavity from a low to high pressure gradient
Summarise ventilation in fish when water moves out
Mouth closes
operculum opens
Floor of buccal cavity rises
Volume of buccal cavity decreases
Pressure in buckle cavity increases
Direction of water flow is out of the operculum from a high to low pressure
Describe the structure of the gills of bony fish
On the Gill arch there are many filaments which provide a large surface area for gas exchange
On each gill filament there are gill lamellae blood circulate through lamellae creating a concentration gradient
Each Gill is made from a single arch
Summarise countercurrent flow
Deoxygenated blood is brought from the body cells
Oxygenated blood returned to body
Water flows in the opposite direction to the blood flow over Gill plates
The epithelium of gill lamellae is one cell thick which provides a short diffusion distance
Each gill lamellae has an extensive blood capillary network in Gill plates. This allows oxygen to diffuse from the water into the blood across the entire length of the gill lamellae
Describe countercurrent graph
O2 concentration gradient is maintained across the entire length of the lamellae
02 diffuses from the water into the blood across the entire length of the gill lamellae
As water always has a higher concentration than blood
Blood becomes more highly saturated with oxygen
Describe parallel flow graph
O2 concentration gradient not maintained across the entire length of gill lamellae
O2 diffuses from water into blood until equilibrium is reached
Blood becomes less saturated with O2
Describe gas exchange in amphibian larvae
They live in water and have gills for gas exchange
Gas exchange in adult amphibians
When active gas exchange surface is lungs
When inactive gas exchange surface is diffusion across the moist surface
Why are the rings of cartilage around the trachea?
It allows slight expansion and contraction of the trachea
So more air can go into alveoli
C shape prevents airways from collapsing during inspiration where pressure is low
Why are there goblet cells that line the trachea?
Goblet cells produce and secrete mucus trap microorganisms
Cilia will then waft to move the mucus up and out of the trachea
