2 - MZH - Transport across membranes Flashcards
List the 4 basic exchange mechanisms?
Diffusion
Osmosis
Active transport
Bulk tranksport (cytosis)
Define diffusion
The net movement of particles from a a region of high conc to a region of low conc (down a conc gradient) across a partially permeable membrane
Define Osmosis
The net movement of water molecules through a partially permeable membrane from a solution of less negative water potential to a solution of more negative water potential
What is water potential?
Geatest value and what is it?
What is it always?
The pressure exterted by water
0 (pure water)
Value is always negative
Name the 2 different types of diffusion and their differences
Simple diffusion - Diffusion in the absence of a barrier.
Facilitated diffusion - Diffusion across membranes. Involves particles passing through the phospholipid bilayer
Facilitated diffusion? Example?
- -Diffusion across membranes down a conc gradient.*
- Hydrophilic (not lipid soluble) molecules can’t directly diffuse through so they pass through a channel or a carrier protein.
There’s ion channels which are formed by proteins with a central pore and can be open or closed to regulate the flow of ions.
- Passive process (no ATP required)
- Involves the conformational change of carrier proteins (not in channel proteins!)
E.G Aquaporins
Simple diffusion?
- -Movement of lipid soluble (hydrophobic) substances across the phosphoipid bilayer.*
- Passive process (No ATP required).
Name the types of bulk transport.
What is it?
The transport of larger molecules. Called CYTOSIS.
Non passive process. Requires ATP.
Exocytosis - Movement of things out of the cell via vesicles that are formed at the golgi apparatus, they move towards the plasma membrane and the contents of the vesicle are then released outside of the cell.
Endocytosis - Transporting materials into the cell. There’s 2 types: Phagocytosis (for solids) and Pinocytosis (for liquids)
What is special about membranes with protein transport molecules?
The molecules are selectively permeable as most protein transport molecules are specific to one molecule or ion
Conditions for max diffusion rate?
Example of something that has adapted to satisfy these things?
Minimum possible thickness of exchange sufaces
Maximum surface area
Steep conc gradients
Gas exchange in the alveoi in the lungs
Active transport?
- -The movement of particles across a partially permeable membrane where they’re less concentrated to where they are more concentrations (up the conc gradient).*
- Non passive process (Requires ATP)
- Includes conformational change of carrier proteins.
- Allow cells to buils up stores of a substance which would otherwise be spread out by diffusion e.g. uptake of glucose by liver cells
How are processes that use active transport slowed down or even halted?
- Low Temperatures reduce enzyme activity, reduces rate of respiration, reduce production of ATP. Need ATP for the process.
- Lack/absence of oxygen, reduce rate of respiration, reduce production of ATP.
- Use of metabolic poisons (enxyme inhibitors), reduce/halt enzyme activity, reduce/halt respiration, reduce/halt production of ATP. Example = Cyanide
Direction of travel for water potential?
What do solute molecules do to water potential?
Less negative to more negative
Solute molecules lower water potential
Symbol for water potential and it’s units?
kPa (kilo pascals) or mPa (mega pascals)
What is a:
Hypotonic solution
Isotonic solution
Hypertonic solution
Hypotonic solution - Lower solute potential
Isotonic solution - Same solute potential
Hypertonic solution - Higher solute potential
Describe what happens to a plant and animal cell when palced in a:
Hypertonic solution
Isotonic solution
Hypotonic solution
Animal:
Hypertonic solution - Shriveled
Isotonic solution - Normal
Hypotonic solution - Lysed
Plant:
Hypertonic solution - Plsmolyzed
Isotonic solution - Flaccid
Hypotonic solution - Turgid
