Biology 3.1
some topis from B3.1
- Created by: PortiaDowd
- Created on: 17-11-12 14:24
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- Biology 3.1
- Dissolved Substances
- Osmosis
- The movement of water through a partially permeable membrane into a solution with low water concentration
- Partially permeable membrane
- stops solute molecules getting through because they are too large
- allows water molecules through
- Partially permeable membrane
- The movement of water through a partially permeable membrane into a solution with low water concentration
- Dissolved substances move by
- Diffusion
- The mixing of two substances through the natural movement of their particles from a high concentration to a low concentration
- Active Transport
- the movement of substances against a concentration gradient; requires energy
- Diffusion
- Osmosis
- Osmosis and cells
- When the concentrations of the solutions inside and outside a cell are different, it causes water to move into or out of the cell by osmosis
- Osmosis will gradually dilute the more concentrated solution. for example, water moves from the soil into a plants root hair cells by osmosis, along a concentration gradient.
- Active Transport
- Substances are sometimes absorbed against a concentration gradient i.e. in the opposite direction to the normal distribution. This.....
- requires energy from respiration
- is known as active transport
- Active transport allows cells to absorb sugar and ions, which can pass through cell membranes, from very dilute solutions
- Plants absorb ions from very dilute solutions in the soil by active transport.
- In humans, sugar can be absorbed from the intestine and from the kidney tubules by active transport
- Substances are sometimes absorbed against a concentration gradient i.e. in the opposite direction to the normal distribution. This.....
- Exchanging Materials
- Many organ systems are specialised for exchanging materials. features that make exchange surfaces efficient include
- being thin, providing a short diffusion path
- Being vantilated (in animals) for gas exchange.
- a large surface area
- having an efficient blood supply (in animals)
- The larger and more complex an organism is, the more difficult it is to exchange materials. Exchange surfaces in organisims are adapted to maximise their effectiveness.
- In humans
- alveoli increase the surface area of the lungs
- Villi increase the surface area of the small intestine
- In humans
- Many organ systems are specialised for exchanging materials. features that make exchange surfaces efficient include
- Dissolved Substances
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