SB8a - What are all the chemical reactions in your body known as?
SB8a - What must happen to waste products in your body?
They must be excreted so that they don't cause any problems
SB8a - What are some examples of waste products in your body?
- Carbon dioxide
SB8a - What are some examples of substances that your body takes in?
- Amino Acids
SB8a - Through what process do most substances move around the body?
SB8a - What do diffusion surfaces have to be like?
- Thin: So particles don't have to diffuse far
- Large surface area: More room to allow particles to diffuse through
SB8a - Why does blood need to continue flowing for substances to continue moving?
- Oxygen and glucose diffuses out and carbon dioxide diffuses in at a certain point
- The blood then continues to flow
- This means that concentration gradient at the diffusion point is maintained
- This allows diffusion to continue happening
SB8a - Why do multi-cellular organisms need transport systems?
Transport systems are needed to take substances towards the centre of the body as diffusion from the outside to the centre of the body would take too long
SB8a - What is the circulatory system made of?
- The heart
- A network of fine capillaries
SB8a - How do you calculate surface area : Volume ratio?
Surface area ÷ Volume
SB8a - Why does SA:V ratio affect rate of diffusion?
A higher surface area means more area through which particles can diffuse, but a larger volume takes longer to be filled up
SB8a - Why can't cells be infinitely large?
- As cells get bigger, their SA:V ratio gets smaller.
- This means it will take longer and longer for substances to enter the cell
SB8a - What adaptation do the lungs have?
- The lungs have millions of aveoli which increase the surface area while maintaining the volume.
- This increases the SA:V ratio increasing rate of gas exchange
SB8a - What adaptations do alveoli have?
- One cell thick wall allowing for easy diffusion
- Large SA:V ratio due to its shape
SB8b - What is 1dm3 equal to?
SB8b - How do you calculate concentration?
mass of solute (g) / volume of solution (dm3)
SB8b - How does concentration gradient affect rate of diffusion?
The steeper the concentration gradient (Greater the difference in concentration) the higher the rate of diffusion due to a larger net movement of particles in the same time
SB8b - What is the relationship between concentration gradient and rate of diffusion?
They have a linear directly proportional relationship
rate of diffusion ∝ concentration difference
SB8b - How does surface area affect rate of diffusion?
- A higher surface area means that particles have more area to pass through.
- This means that more particles can move through a membrane at one time.
- This increases the overall rate of diffusion but doesn't change the speed at which particles move
SB8b - What is the relationship between surface area and rate of diffusion?
rate of diffusion ∝ surface area
SB8b - How does the thickness of the membrane affect rate of diffusion?
- A thicker membrane means that particles have a longer distance to travel.
- This means that the rate of diffusion will be slower
SB8b - What is the relationship between thickness of membrane and rate of diffusion?
rate of diffusion ∝-1 thickness of membrane
rate of diffusion ∝ 1 ÷ thickness of membrane
SB8b - What is Fick's law?
Fick's law shows the relationship between the three factors that affect rate of diffusion.
SB8c - What are the jobs of each of the components of the circulatory system?
- Heart: Pumps blood around the body
- Arteries: Take blood away from the heart
- Capillaries: Fine networks taking blood to and through tissue
- Veins: Takes blood back to the heart
SB8c - What are the adaptations of arteries?
- Narrow lumen (tube)
- Thick elastic and muscle fibres
- This helps it withstand high pressures
- Recoil due to elasticity helps the blood continue to be pumped
SB8c - What are the adaptations of capillaries?
- Capillaries have very narrow lumen (tubes) as they are carrying very little blood
- They have walls only 1 cell thick to allow for faster diffusion
SB8c - What are the adaptations of veins?
- Valves to ensure blood flows in one direction
- Thin walls as pressure is low
- Wide lumen (tube) to reduce pressure
SB8c - Why are valves only necessary in veins?
- Arteries have blood flowing at a high pressure and this ensures blood flows in the right direction
- This is helped by the elasticity
- Veins have blood flowing at a low pressure and so blood isn't forced to travel in the right direction
- Valves ensure blood flows in the correct direction
SB8c - How do valves work?
- Valves are like one way doors
- Skeletal muscles help blood move along the veins
- When blood is flowing in the correct direction, valves are open
- When muscles are relaxed, blood can easily flow in the wrong direction
- The moment any blood starts to flow in the wrong direction, the valves close, stopping blood from flowing this way
SB8c - What is another word for red blood cells?