Biological Membranes Flashcards
What is active transport
Transport of molecules or ions against a concentration gradient. Requires additional energy, usually in the form of ATP.
What is allostery
Where binding of a molecule at one site triggers a change in shape of the protein
What’s cholesterol
Steroid that inserts between the fatty acid tails of the phospholipids and regulates the fluidity of a membrane
What does crenated mean
When an animal cell is placed in a solution of low water potential, water leaves the cell by osmosis down the water potential gradient, causing the cell to shrivel up.
What is Cytolysis
When an animal cell is placed in a solution with a high water potential (e.g. pure water), water enters the cell by osmosis down the water potential gradient, rupturing its cell surface membrane. (Termed haemolysis in red blood cells)
What’s endocytosis
The inward transport of large quantities of molecules through the cell surface membrane. This requires an input of energy in the form of ATP
What’s exocytosis
The outward transport of large quantities of molecules through the cell surface membrane. This requires an input of energy in the form of ATP
What’s facilitated diffusion
Transport of molecules or ions across a membrane down a concentration gradient that require a transport protein (channel or carrier) to cross the membrane
What is meant by the term flaccid
Plant cell in an isotonic solution that has lost its turgidity or a plant tissue in which the plant cells are plasmolysed
What’s the fluid mosaic model
Current model for the structure of membranes
What are hormones
Chemicals released by endocrine glands which acts as chemical signalling molecules
What does hydrophilic mean
A molecule able to associate with water as it possesses a charge which interacts with the dipoles on water molecules
What does hydrophobic mean
A molecule not able to associate with water as it is uncharged. It repels water
What is incipient plasmolysis
The point at which water leaving a plant cell by osmosis shrinks the protoplast so much that it no longer exerts any pressure on the cell wall.
What’s osmosis
A specialised form of diffusion where water molecules move from an area of higher water potential to one of lower water potential - down the water potential gradient - through a partially permeable membrane
What is meant by partially permeable
Able to let some molecules or ions pass through and not others
What is phagocytosis
‘Cell-eating’. Uptake of large quantities of sold materials by endocytosis.
What’s a phospholipid
Specialised lipid molecule containing a phosphate group, two fatty acids and glycerol. Forms a bilayer that is the structural basis of membranes.
What’s pinocytosis
‘Cell-drinking’. Uptake of large quantities of solutes in solution by endocytosis
What’s plasmolysis
When a pant cell is placed in a solution of low water potential, water leaves the cell by osmosis, causing the protoplast to shrink, pulling the plasma membrane away from the cell wall.
What’s a protoplast
Cell contents inside plasma membrane
What’s meant by selectively permeable
Presence of transport proteins determines which molecules can be transported across
What’s a tonoplast
The membrane surrounding the vacuole in a plant cell.
What’s meant by turgid
When a plant cell is placed in a solution of low water potential, water enters by osmosis and the protoplast pushes against the cell wall.
What is water potential
Measure of the tendency of water molecules to move from one region to another. Affected by solute concentration and any external applied pressure.
Always a negative value measured in kilopascals (kPa) and given the symbol
Ч.
