Exchange- Size and Surface Area Flashcards
What do cells need to take in?
Oxygen (for aerobic respiration) and nutrients
What do cells need to excrete?
Waste products like carbon dioxide and urea
Why do most organisms need to stay at the same temperature?
Heat needs to be exchanged
What determines how easily the exchange of substances is?
The organism’s surface area to volume ratio
How do you calculate volume?
Length x width x depth
How do you calculate surface area?
Calculate areas of faces and add together
What do all organisms need to exchange?
Needs to supply all cells with substances such as glucose and oxygen for respiration and needs to remove waste products from each cell to avoid damage
How are substances exchanged in single-celled organisms?
Substances can diffuse into or out of cell across cell surface membrane
What is the speed of diffusion in single-celled organisms?
Quick because of the small distances the substance have to travel
What is the speed of diffusion in multicellular organisms?
Slow
Why is the rate of diffusion slow in multicellular organisms?
- Some cells are deep within the body and there’s a big distance between them and the outside environment
- Larger animals have a low surface area to volume ratio so it’s difficult to exchange enough substances to supply a large volume through a small outer surface
What do multicellular organisms need?
Specialised exchange organs rather than using straightforward diffusion to absorb and excrete substances and an efficient system to carry substances to and from their individual cells (mass transport)
What does mass transport usually refer to in mammals?
The circulatory system
What does the circulatory system carry around the body?
Glucose and oxygen in blood, hormones, antibodies and waste like CO2
What does mass transport in plants involve?
The transport of water and solutes in the xylem and phloem
