F211-Transport Across Membranes Flashcards
What 4 factors determine the rate of diffusion?
1~The concentration gradient-the steeper the gradient, the quicker the rate of diffusion.
2~Temperature-high temp=more kinetic energy so faster diffusion.
3~The surface area- greater the SA, faster the diffusion.
4~Type of molecule or ion diffusing-larger molecules need more kinetic energy to move so they diffuse more slowly. Non-polar molecules diffuse more easily than polar molecules because they are soluble in the non polar phospholipid tails.
What 6 ways can molecules be transported through the plasma membrane?
~diffusion ~osmosis ~facilitated diffusion ~active transport ~endocytosis ~exocytosis
Define Diffusion
This is the NET movement of molecules from a region of high concentration to a region of low concentration down a concentration gradient until they are in a state of dynamic equilibrium.
What molecules can diffuse through the membrane via diffusion?
Oxygen (non polar)
Carbon Dioxide (polar but small)
Water (polar but small)
Define Facilitated Diffusion
The passage of molecules from an area of high concentration to an area of low concentration across the membrane through a carrier or channel protein.
What molecules can transport through the membrane via facilitated diffusion?
Large polar molecules - such as Glucose and Amino Acids Charged ions (Na+ of Cl-)
Define Osmosis
Osmosis is the passive moment of water molecules from a region of high water potential to a region of low water potential through a partially permeable membrane
What is water potential?
The tendency of water molecules to move from one place to another. Some molecules collide with the membrane as they move around at random. This will exert a pressure on the membrane.
What is the highest water potential?
0kPa
Define Hypertonic Solution
A hypertonic solution has a lower (more neg) water potential (water moves out)
Define Hypotonic Solution
A hypotonic solution has a higher (less neg) water potential (water moves in)
Define Isotonic Solution
An isotonic solution has fb exams water potential
Define Incipient Plasmolysis
Incipient Plasmolysis is when the cytoplasm of a plant cell just begins to shrink away from the cell wall. 50% of cells will be plasmolysed when the mean solute potential equals the water potential of the external solution.
What happens when an animal cell is places in a Hypotonic Solution?
Water enters by osmosis, the cell bursts which is called Lysis
What happens when an animal cell is places in an Isotonic Solution?
Water movement is equal, the cell stays the same
What happens when an animal cell is places in a Hypertonic Solution?
Water moves out of the cell by osmosis, the volume decreases, the membrane shrinks which is called Crenation
What happens when a Plant cell is placed in a Hypotonic Solution?
Water enters by osmosis, the cell becomes Turgid
What happens when a Plant cell is placed in an Isotonic Solution?
Water movement is equal, the cell stays the same
What happens when a Plant cell is placed in a Hypertonic Solution?
Water leaves by osmosis, the cell shrivels which is called Plasmolysis
Define Facilitated Diffusion
The passive net movement of molecules from a region of high concentration to a region of a lower concentration gradient through a channel or carrier transport protein
Suggest why different red blood cells haemolyse at different salt concentrations?
All cells can have slightly different water potentials
Define Active Transport
This is the movement of substances across the membrane from an area of low concentration to an area of high concentration against the concentration gradient
What does Active Transport require?
Specific carrier proteins and Energy in the form of ATP
Cells which have active transport occurring may have Microvilli to increase the surface area, why?
They do this so more carrier proteins are available for active transport
Cells which have active transport occurring may have many mitochondria, why?
This is for energy-it provides aerobic respiration - provides ATP for ATPsynthase
What is Bulk Transport?
Moving large quantities of material in or out of a cell with the requirement of energy
What are the two types of bulk transport?
Exocytosis - material out of cell Endocytosis - material into cell
What are the two types of endocytosis? And what do they mean?
Phagocytosis-takes in solid molecules&forms a vesicle
Pinocytosis-takes in solutes and forms a vesicle
Define endo/exocytosis
The bulk movement of molecules into or out if a cell
