Karteikarten
Cell Membranes
Karten in diesem Stapel (20)
- 1How thick is the phospholipid bilayer?7 nanometers
- 2What are the major roles of the cell membrane?1. Separating cell contents from the outside environment
2. Separating cell components from the cytoplasm.
3. Cell recognition and signalling
4. Holding components of metabolic pathways in place
5. Regulating transport of materials in and out of cells - 3What is the cell membrane made up of?The Fluid Mosaic Model:
- Phospholipid bilayer
- Cholesterol molecules
-Protein molecules
- Glycolipids
-Glycoproteins - 4Phospholipid bilayerDue to its hydrophilic head and hydrophobic tails the phospholipids arrange themselves in a bilayer. The centre of the bilayer is hydrophobic so the membrane acts as a barrier to polar substances.
- 5CholesterolCholesterol is a type of lipid present in almost all cell membranes, more cholesterol makes a membrane less fluid and more rigid.
- 6Protein moleculesProtein molecules control what enters and leaves the cell. They can take the form of channel proteins (passive) or transport proteins (active - require ATP).
They are also involved in cell signalling, when a molecule binds to a protein a chemical reaction is triggered. - 7Glycolipids and GlycoproteinsStabilise the cell membrane by forming hydrogen bonds with surrounding water molecules. Site of binding for drugs, hormones and antibodies, and act as antigens. They also act as receptors for cell signalling.
- 8How cell signalling worksA cell releases a messenger molecule (e.g. a hormone), this molecule travels to another cell where it binds to a receptor, this brings about a response.
- 9The role of receptors in cell signallingMembrane bound proteins act a receptors for messenger molecules. Messenger molecules will only bind to receptor proteins with complementary shapes.
- 10Drugs and cell membranesDrugs also work by binding to receptors, they do this in order to either bring about a response or inhibit the receptor, stopping a response.
- 11The cell membrane below 0°CThe membrane is very rigid, but the protein molecules denature which increases permeability, ice crystals can form and pierce the membrane increasing permeability when it thaws.
- 12The cell membrane from 0-45°CThe membrane is partially permeable as phospholipids can move, as temperature increases the phospholipids gain more kinetic energy making the membrane more permeable.
- 13The cell membrane at temperatures above 45°CThe phospholipids begin to melt increasing permeability, the protein molecules denature, also increasing permeability.
- 14Definition of diffusionThe net movement of particles from an area of their high concentration to an area of their low concentration down a concentration gradient.
- 15What changes the rate of diffusion?The steepness of the concentration gradient
The thickness of the exchange surface
The surface area to volume ratio - 16Definition of osmosisThe net movement of water molecules from and area of their high water potential to an area of their low water potential across a partially permeable membrane down a water potential gradient.
- 17EndocytosisThis is the bulk transport of materials into a cell. The substance is surrounded by a plasma membrane which forms a vesicle. This is a process often used by phagocytes.
- 18ExocytosisThis is the bulk transport of materials out of the cell. Vesicles produced by the golgi apparatus move towards the plasma membrane, merging with it and releasing the contents to the outside environment.
- 19Carrier proteinsInvolved in facilitated diffusion, a large molecule binds to the carrier protein. The protein changes shape allowing the molecule to be released on the other side of the membrane.
- 20Channel proteinsThese form pores, allowing small charged particles to pass through.
Informationen
- Beschreibung
- AS Level Biology (Unit 1) Karteikarten am Cell Membranes, erstellt von Aylin Laity am 26/12/2014.
- Erstellt von
- Aylin Laity
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- 3
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