Unit 2 - Plasma membranes Flashcards
State 4 functions of plasma membranes
Options:
- recognition of other cells
- separates cell contents from the outside (barrier between cells and its environment)
- controls the passage of materials in and out
- allow cell communication
- phagocytosis
- cell to cell attachment
State 4 functions of membranes inside cells
Options:
- isolates DNA
- acts as an intracellular transport system
- compartmentalises reactions
- can be the site of chemical reactions
- ribosomes attach
- protection from lysosomes
- forms vesicles
Define compartmentalisation
The formation of separate membrane-bound areas
Why is compartmentalisation useful in cells?
- incompatible reactions occur within the cell
- isolates reactions making them more efficient
- allows reaction conditions to be maintained (e.g chemical gradients)
- protects cell components
Define partially permeable
A membrane that allows some substances to cross but not others
Define cell signalling
A complex system of intercellular communication
Define phospholipid bilayer
- arrangement of phospholipids found in cell membranes
- the hydrophilic phosphate heads form the inner and outer surface of a membrane ,
- sandwhiching the fatty acid tails to form a hydrophobic core
Why are membranes referred to as having a ‘fluid-mosaic structure’ ?
- the phospholipids are able to move freely relative to each other (fluid)
- the proteins embedded in the bilayer vary in shape, size, and position (mosaic)
Define glycoprotein
Extrinsic membrane proteins with attached carbohydrate molecules of varying lengths and shapes
Define glycolipid
Cell-surface membrane lipids with attached carbohydrate molecules of varying lengths and shapes
Define phospholipid
Modified triglycerides, where one fatty acid has been replaced with a phosphate group
What are channel proteins?
Membrane proteins that provide a hydrophilic channel through a membrane
What are receptor proteins?
Extrinstic glycopoteins that bind chemical signals, triggering a response by the cell
What are carrier proteins?
Membrane proteins that play a part in the transport of substances through a membrane
What is the approximate width of an animal cell plasma membrane?
7nm