Plasma cell membrane Flashcards
What is the plasma membrane function ?
- Act as a barrier between the cell and the environment – they control what moves into and out of the cell. The plasma membrane is partially permeable so it lets some substance through but not others.
- Cell recognition – glycoproteins on the plasma membrane act as antigens, telling the immune system that the cell is not a foreign pathogen.
- Cell communication – receptors on the plasma membrane bind to hormones or other chemicals released by other cells.
What are the functions of intracellular membranes ? Facc
- Compartmentalises the cell – internal membranes act as a barrier between organelles and the cytoplasm, allowing them to function more efficiently by keeping enzymes and molecules in one place.
- Form vesicles to transport substances around the cell.
- Control what moves into and out of organelles – intracellular membranes are partially permeable.
- Act as the site of chemical reactions – for example, thylakoid membranes inside chloroplasts are where photosynthetic reactions take place.
What is the fluid mosaic model ?
Fluid mosaic model
* The structure of the plasma membrane is made up of a bilayer of phospholipids with proteins and cholesterol interspersed throughout the structure.
* The fluid mosaic model is used to describe the arrangement of molecules in the membrane - ‘fluid’ because the phospholipids are constantly moving around and ‘mosaic’ because protein molecules are scattered throughout the phospholipids like tiles in a mosaic
What are the components of the cell membrane ?
- Phospholipids
- Glycoproteins
- Glycolipids
- Cholesterol
- Intrinsic proteins
- Extrinsic proteins
What is a phospholipid ?
- Phospholipids ( creates a bilayer) : consist of a hydrophilic head group which faces the intracellular / extracellular fluid and two hydrophobic tails which point towards each other, away from water. They are the main component of the plasma membrane and form a barrier to anything which is not lipid-soluble (such as ions and glucose).
**What is a Glycoprotein ? **
- These are proteins with sugar molecules attached. They act as recognition sites and antigens - antigens are like little ‘flags’ on the surface of our cells which allows our body to detect which cells are our own and which cells are foreign.
What is a Glycolipid ?
- These are phospholipids with sugar molecules attached. They have a similar function to glycoproteins - they also act as recognition sites and antigens. They also increase membrane stability by forming hydrogen bonds with water molecules.
What is cholestrol?
- Cholesterol: cholesterol is a lipid which slots in between the phospholipid tails, pushing them closer together. It regulates the stability and fluidity of the plasma membrane.
What are Intrinsic proteins ?
- Intrinsic proteins: these are proteins which span both bilayers of the plasma membrane. They act as channels or carrier proteins to transport water-soluble molecules.
What are Extrinsic proteins ?
- These are proteins which are found on the surface of the plasma membrane. They usually function as enzymes and catalyse chemical reactions inside the cell.
What are the factors affecting the membrane permeability ?
- Temperature
- PH
- Solvent concentration
**Explain solvent concentration **
-The more easily the phospholipid bilayer is dissolved, the more permeable the membrane is.
- Solvent concentration can be controlled by using the same solvent at the same concentration for each trial.
Explain temperature
-Higher temperatures increase the fluidity of the membrane, increasing its permeability.
- Using a water bath can help keep temperature constant.
Explain PH
-pH affects the protein structure in the cell membrane.
-Buffer solutions can be used to control the pH.
**What’s is cell signalling ? **
- When cells communicate to each other
- Cell signalling starts when one cell releases a messanger molecule this molecule travels to another cell and is detected by the membrane and it binds to a receptor, the binding triggers a change in the cell.
