Cell Membrane Flashcards
What is the cell membrane?
Thin barrier separating the inside of the cell (cytoplasm and organelles) from the outside environment
What is the cell membrane for?
Protection, transport, shape/structure and for communicating and signalling
What is the fluid mosaic model?
The cell membrane consists of embedded proteins that shift and flow with a layer of phospholipids.
What are the 5 types of cell membrane proteins?
1) Receptor
2) Recognition
3) Enzymes
4) Attachment
5) Transport
What do receptor proteins do?
Trigger cell activity when a molecule outside binds to a protein
What do recognition proteins do?
Allow cells to recognise one another
What do enzyme proteins do?
They catalyze chemical reactions on the inner surface of membranes
What do attachment proteins do?
They anchor membrane to internal framework and external surface of neighbouring cells
What do transport proteins do?
Regulate the movement of hydrophilic molecules via membrane
How many routes are there for movement across membranes and what are they?
4
1) Passive Transport
2) Active Transport
3) Endocytosis
4) Exocytosis
How many types of passive transport are there? What are they?
Three
1) Diffusion
2) Facilitated Diffusion
3) Osmosis
What is diffusion?
A form of passive transport involving movement of molecules from high to low concentration.
What is facilitated diffusion?
A form of passive transport. Require assistance of transport or channels that form pores or carrier proteins that require shape changes like glucose.
What is Osmosis?
Movement of water from high to low concentration over a semi-permeable membrane.
What can affect osmosis?
Tonicity - relative solute concentration of two environments separated by a semi-permeable membrane.
1) Isotonic Solution - Retains shape as salt and water content are equal
2) Hypertonic Solution - water leaves = shrinks
3) Hypotonic Solution - water comes in = bursts
What is active transport?
Movement of substances against the concentration gradient aka pumps
Whats an example of active transport?
The sodium-potassium pump (more potassium inside the cell, less sodium outside). Requires energy,
What is endocytosis?
The movement of large volumes into cells via vesicle formation and it requires ATP
How many types of endocytosis are there and what are they called?
Three;
1) Pinocytosis
2) Receptor-Mediated Endocytosis
3) Phagocytosis
What is Pinocytosis?
A form of endocytosis. Cell drinking.
How does pinocytosis occur?
The cell membrane invaginates enclosing extracellular fluid and then the vesicle pinches off and brings its contents into the cell
How does receptor-mediated endocytosis occur?
A form of endocytosis where ligand binds to a receptor protein in the cell membrane, the ligand-receptor complex moves into a clathrin-coated pit invaginates and the vesicle pinches off.
What is receptor-mediated endocytosis?
The uptake of molecules vias coated pits
What is phagocytosis?
A form of endocytosis. “Cell eating” - uptake of large particles. Bacteria or cell debris bind to cell receptors that form a phagosome vesicle and pinch off.
What is exocytosis?
Regulates biological events like neurotransmitter and hormone release delivering proteins etc to the plasma membrane.
What can easily pass through cell membranes?
Lipids
