Cell Transport
Osmosis
Facilitated Diffusion
Active Transport
rthgrethr
- Created by: Ramisha
- Created on: 05-12-14 11:28
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- Transport in and out of cells
- Diffusion
- The net movement of molecules or ions from a region where they are more highly concentrated to one where their concentration is lower
- Rate of Diffusion
- Difference Concentration Gradient
- Area of which diffusion takes place - Surface Area
- Thickness of exchange surface
- Temperature: Higher temp, particles bounce and spread more quickly
- Ficks Law-Proportional to: (Surface area X Difference in Conc) / Length of Diffusion Path
- Down a concentration gradient
- Passive
- Energy requirement: Kinetic energy of particles
- Types of particles moved across membrane: Lipid soluble, small, non-polar molecules
- Examples
- Lungs: O2 diffuses from air into blood, C02 diffuses out
- Gills: O2 diffuses from water into blood
- Leaves: CO2 diffuses into palisade cells
- Active Transport
- movement of molecules or ions into or out of a cell from a region of lower conc to an area of higher conc using energy and carrier molecules
- Metabolic energy in the form of ATP needed
- Carrier proteins act as pumps
- Selective process - specific substances transported
- Hydrolysis of ATP: ATP binds protein - split into ADP and phosphate. Protein changes shape
- Co-transport of glucose, Sodium-potassium pump
- Na ions removed cell, K ions in cell
- Ions and medium-sized molecules
- uses carrier proteins (pumps)
- Osmosis
- The net movement of water molecules from a region of higher water potential to a region of lower water potential across a partially permeable membrane
- solute attracts water
- Partially permeable plasma only allows water molecules across - not solute
- Highest water potential=0= pure water
- lower water potential= more negative
- units kilopascals (kPa)
- lower water potential= more negative
- Down water potential gradient
- Energy required: Kinetic energy of particles
- Moves water molecules across membrane
- Facilitated Diffusion
- Passive Process - relies on the inbuilt kinetic energy of diffusing molecules
- Types of particles moved across membrane: Ions and medium sized molecules (e.g) glucose
- Down concentration gradient
- Transport proteins at specific points
- Protein Channels (ions)- hole through middle, some specific/some non-spcific, some open all time/ some gated channels which open and close
- Carrier proteins (glucose) - medium sized molecules, change in shape
- Stops when equilibrium reached
- Diffusion
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