Cell Membranes Flashcards
Function of membranes: permeable?
Controls what enters and leaves the cells
Function of membranes: separate compartment from cytoplasm?
Specific metabolic reactions can take place within them
Function of membranes: internal transport system?
E.g. endoplasmic reticulum
Function of membranes: isolation?
Isolate enzymes that might damage cells e.g. lysosomes
Function of membranes: surface?
Provide surface on which reactions can occur e.g protein synthesis
What are membranes made out of?
Phospholipids- arranged in a bilayer
What molecules can easily pass through the membrane?
Small, uncharged, non-polar molecules
Why are membranes referred to as a fluid mosaic model?
Fluid- not fixed movement
Mosaic- mixed pattern
Functions of phospholipids: permeability?
Form water impermeable barrier to polar substances- makes it selectively permeable
Functions of phospholipids: permeable to allow what molecules through?
Non-polar molecules
Functions of phospholipids: different concentrations?
Allows cell to maintain different concentrations either side
Functions of phospholipids: fluid?
Makes membrane fluid to fuse with other membranes/make vesicles
Why is a cell membrane referred to as a fluid mosaic model?
Fluid- not fixed movement
Mosaic- mixed pattern
What happens if there is too little/too much cholesterol?
Too much = too rigid
None = too fluid
What is the structure of cholesterol?
Hydrophobic tails
Hydrophilic heads
Where do the cholesterol molecules fit?
Between the phospholipid bilayer - orientated the same way
Head out, tail in
Is cholesterol hydrophobic or hydrophilic?
Hydrophobic to prevent the loss of water
Is cholesterol hydrophobic or hydrophilic?
Hydrophobic
Function of cholesterol: movement?
Reduce movement of other molecules
Function of cholesterol: fluidity?
Makes the membrane less fluid at high temperatures
Function of cholesterol: tissues?
Helps cells attach to one another and form tissues
Function of cholesterol: strength?
Adds strength to the molecule
Where do proteins span across?
The whole membrane
What do proteins help the cell do?
Stuck together
What does intrinsic mean?
Inside the bilayer
What does extrinsic mean?
Outside the bilayer
What is a glycolipid?
A carbohydrate covalently bonded to a lipid
What does a glycolipid act as?
A cell-surface receptor
What does a glycolipid add?
Stability
Are glycoproteins extrinsic or intrinsic?
Extrinsic- they are on the outer surface of the cell membrane with carbohydrate chains attached
What are glycoproteins?
Cell- surface receptors- specifically for hormones and neurotransmitters
Where are the carbohydrate chains found in the glycoproteins?
Found on the outer phospholipid monolayer- the carbohydrate chains also project out into fluid in the cell
