A1 Cell Membranes And Transport Flashcards
What do phospholipids consist of?
Two hydrophobic fatty acid chains and a phosphate group which is hydrophilic joined together by a glycerol.
What can phospholipids form?
A phospholipid bilayer, cell membranes are made up of this
What do cell membranes consist of?
Hydrophilic heads, hydrophobic tail, cholesterol, intrinsic protein, extrinsic protein, glycolipid, glycoprotein
Membranes are… P… P…
Partially permeable
What does the fluid mosaic model describe?
The arrangement and movement of the molecules that make up a cell membrane.
What does fluid describe in the fluid mosaic model?
Fluid- phospholipids (and proteins) are free to move sideways
What does mosaic describe in the fluid mosaic model?
Proteins have a scattered arrangement within the bilayer
What is a phospholipid?
A lipid molecule that has a polar, hydrophilic head and a non polar, hydrophobic tail. They form the main component of cell membranes.
What is the role of cholesterol in a cell membrane?
Fluidity and stability
What are glycolipids?
Phospholipids with carbohydrates attached
What is the role of glycolipids?
Cell signaling and direction
What is the role of intrinsic proteins in the cell membrane?
Some act as carriers to transport water- soluble molecules across the membrane. Others act as enzymes.
What is the role of extrinsic proteins in the cell membrane?
Cell signalling, cell recognition, enzymes receptors
What is the role of membranes within cells?
Compartementalisation:
1. separate organelles content from cell cytoplasm 2. provides large surface area for aerobic respiration 3. contains digestive enzymes 4. where some reactions take place
What is the role of membranes on the surface of cells?
- separate cells components from external environment 2. transport of materials 3. contain enzymes for reactions 4. has antigens to recognise cells as their own 5. receptors for chemical signals
Describe the cell signalling process
- one cells releases a messenger molecule e.g a hormone 2. this molecule travels to another target cell e.g in the blood
- the messenger molecule is detected by the cell because it binds to the receptor on the target cell’s cell membrane 4. the cell then responds to the messenger molecule by a change in activity
Describe diffusion
The passive movement of molecules from an area of high concentration to an area of low concentration across a partially permeable membrane through a phospholipid bilayer
Factors that can affect the rate of diffusion?
Temperature, concentration gradient, surface area, thickness of exchange area
What is the type of molecule that can diffuse through the bilayer?
Lipid soluble ones, small and non polar molecules e.g oxygen, very small polar molecules e.g water
Describe facilitated diffusion
The passive net movement of substances from an area of high concentration to an area of low concentration down a concentration gradient across the membrane via carrier or channel proteins
What are channel proteins?
Proteins that provides corridors that allows a specific molecule or ion to cross the membrane
What are carrier proteins?
A protein that transports substances across a cell membrane
Factors affecting the rate of facilitated diffusion
The concentration gradient, temperature, the number of channel or carrier proteins
What is exocytosis?
The process by which a substance is released from the cell through a vesicle that transports the substance to membrane to let the substance out
What is osmosis?
The movement of water from an area of higher water potential to an area of lower water potential, down a water potential gradient across the phospholipid bilayer
What is active transport?
The active movement of ions or polar molecules from a lower concentration to a higher concentration using a carrier protein. This movement against the concentration gradient requires energy from ATP.
What are the types of molecules that are actively transported by carrier proteins?
Large, polar molecules, ions
What could inhibit active transport?
Anything that inhibits respiration and therefore ATP production e.g cyanide
Describe endocytosis
A process in which a cell takes material into the cell by infolding of the cell membrane
What is phagocytosis?
A type of endocytosis and is how white blood cells called phagocytes engulf and digest bacteria.
