Plasma Membranes Flashcards
Define: plasma membrane
a selectively (semi/differentially) permeable membrane that surrounds cells and most organelles that separates their contents from the external environment. It containing a phospholipid bilayer and associated proteins.
Define: external environment
blood plasma and extracellular fluid
Does the plasma membrane surround organelles?
most
How big is the plasma memrbane? how can they be seen?
8 nanometres, with transmission electron microscope.
2 components of the plasma membrane?
Phospholipids and proteins
Describe the phospholipid bilayer (4 parts!)
Phospholipids, WHICH CAN INTERACT WITH WATER, containing:
-> Hydrophilic heads, containing a phosphate group
-> Hydrophilic tails which INTERACT POORLY WITH WATER, containing 2 fatty acid chains that are liquid at HBT
Arranged into a phospholipid bilayer, with hydrophilic heads facing aqueous solutions as they are ok to sit near the water, and hydrophobic tails facing inwards as they don’t mix with water
Define: integral proteins
FUNDAmental components of the plasma membrane that are embedded into the plb
Define: transmembrane proteins
when oart of a protein is exposed on both sides of a membrane.
What are glycoproteins/lipids?
Carbohydrate group attached to a protein/lipid
Define: peripheral protein
proteins anchored to the exterior of the plasma membrane through bonding with lipids or are indirectly associated with the plasma membrane through interaction with integral proteins
Are peripheral or integral proteins easier to separate from the plb?
peripheral
What does the fluid mosaic model propose?
- Plasma membranes surround all cells and many organelles
- Plasma membranes are very flexible and can change shape, because the fatty acid chains are liquid at human body temperature (fluid)
- Plasma membranes are studded with proteins (mosaic)
4 purposes of the plasma membrane?
- active and selective boundary
- denotes cell identity
- some proteins are receptor molecules, receiving signals from outside the cell
- enables transport
How is the plasma membrane an active and selective boundary?
Controls when, what and how much of a substance passes through it; enables cells (and organelles) to maintain conditions that are unique from outside of the memrane
How does the plasma membrane denote cell identity?
Glycoproteins act as cell surface markers (including antigens etc); each cell type has a different combination of surface markers.