Transport in Animals (Edexcel GCSE Combined Science: Biology): Flashcards
Exam code: 1SC0
1/120Still learning
Know0
Exchange of substances
Was this flashcard helpful?
Cards in this collection (12)
Exchange of substances
The movement of substances (such as oxygen, carbon dioxide, water, dissolved food molecules, mineral ions and urea) between an organism and its environment, across the cell membrane.
Exchange surface
A specialised surface in a multicellular organism that maximises the exchange of materials, e.g. the lungs and alveoli or the small intestine and villi.
Name the three transport processes organisms use to exchange substances across the cell membrane.
Diffusion, osmosis and active transport.
Why don't unicellular organisms (e.g. amoeba) need transport systems?
They have a large surface area to volume ratio, so the distance from the surface to the centre is very small. Diffusion, osmosis and active transport across the cell membrane happen fast enough to meet the organism's needs.
Why do large multicellular organisms need exchange surfaces and transport systems?
Their surface area to volume ratio is small and the distance from surface to centre is large, so diffusion, osmosis and active transport alone cannot happen fast enough to meet the organism's needs.
Name the main transport systems found in animals and in plants.
Animals: the blood and circulatory system.
Plants: the xylem (carries water and mineral ions from roots to shoots) and the phloem (carries sugars and amino acids to where they are needed).
Give two examples of exchange surfaces in animals and what each is used for.
The lungs and alveoli for gas exchange.
The small intestine and villi for absorption of digested food.
Give two examples of exchange surfaces in plants and what each is used for.
Roots and root hairs, where mineral ions and water are absorbed.
The leaves, for gas exchange.
What two key properties make an exchange surface efficient?
A large surface area to increase the rate of transport, and a barrier that is as thin as possible to give a short diffusion path.
How do animals help maintain steep concentration gradients at exchange surfaces?
A large network of blood vessels moves substances towards or away from exchange surfaces, and gas exchange surfaces are well ventilated.
Unicellular organisms have a large to volume ratio, so substances can be exchanged across the cell membrane fast enough by .
surface area / diffusion
Large multicellular organisms have a relatively surface area to volume ratio, so they need surfaces and transport systems.
small / exchange
Sign up to unlock flashcards
or