Cell biology- HF
- Created by: Former Member
- Created on: 16-06-18 17:44
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- Cell Biology
- SA:V ratio
- A way of describing how close every internal part is to the surface
- Surface area/ volume
- A low ratio means parts of the objects are large way from edge
- Heat energy takes longer to enter or escape
- A high SA:V ratio means parts of the objects are a short distance from the edge
- Heat energy takes short times to enter or escape
- Diffusion
- The movement of molecules from an area of High Conc, to an area of Low Conc
- Diffusion either happens to substances in liquids or in gases
- The steeper the concentration, the more likely the particles are to diffuse down the conc.
- The larger the surface area, the more particles can diffuse at once
- Temperature can affect rate of diffusion- the more kinetic energy, the particles spread out quicker
- Cells
- Take in glucose and oxygen
- Remove waste products that are needed somewhere else in body. EG. CO2
- Movement of materials in and out of cell via cell membrane can be by diffusion
- Small Organisms
- Diffusion across body surface is sufficient- less than 0.5mm
- Large SA
- Body or cell surface acts as exchange surface
- Surface exchange
- Needs- SA:V ratio is insufficient Exchange distances are too great
- To overcome this- Specialised exchange surface and efficient transport system
- Adaptations
- Animals- Small intestines Mammal lungs Fish Gills
- Plants- roots and leaves
- Diffusion in humans
- Lungs- oxygen for respiration
- Adaptations- Large SA thin linings of aveoli and capillaries moist membranes
- Gut- amino acids and starch break down protein
- Lungs- oxygen for respiration
- Osmosis
- Movement of water from an area of high conc. to an area of low conc. through a partially permeable membrane
- we need a balance of solutes for a cell to work properly
- Isotonic- when the conc of solutes in solution are same as internal conc
- Hypertonic- when conc of solutes outside is higher than conc inside cell
- If the cell becomes too concentrated, cell will shrivel and die
- Hypotonic- when conc is higher inside cell than outside
- If cell becomes too dilute, it will shrivel and die
- Plants need fluid around cell to be hypotonic. Cells are turgid.
- SA:V ratio
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