4.1 - Structure Of The Cell Surface Membrane Flashcards
1
Q
Why are phospholipids important components of cell-surface membranes?
A
Form a bilayer consisting of:
- hydrophilic heads (point outwards/attracted to water)
- hydrophobic tails (point inwards/repels water)
2
Q
What are the function of phospholipids in the membrane?
A
- allow lipid-soluble substances to enter + leave the cell
- prevent water-soluble substances entering + leaving the cell
- makes membrane flexible + self-sealing.
3
Q
What are the functions of proteins in the membrane?
A
- provide structural support
- act as channels transporting water-soluble substances across membrane
- allow active transport across membrane through carrier proteins
- form cell-surface receptors for identifying cells
- act as receptors (e.g. hormones)
4
Q
What are the functions of cholesterol in the membrane?
A
- dec lateral movement of other molecules including phospholipids
- make membrane less fluid at high temps
- prevent leakage of water + dissolved ions from cell
5
Q
What are the function of glycolipids in the membrane?
A
- acts as recognition sites
- help maintain stability of membrane
- help cells attach + so form tissues
6
Q
What are the functions of glycoproteins in the membrane?
A
- act as recognition sites
- help cells attach to others + so form tissues
- allows cells to recognise others, e.g lymphocytes recognise an organisms own cells
7
Q
Why don’t many molecules freely diffuse through the cell surface membrane?
A
- not soluble in lipids so can’t pass through phospholipid layer
- too large to pass through channels in membrane
- same charge as protein channels so repelled (even if small enough)
- polar so difficult to pass through non-polar tails in phospholipid bilayer
8
Q
Why is the cell surface membrane structure knows as the Fluid - mosaic model
A
- fluid: proteins can move freely through lipid bilayer
- mosaic: proteins embedded in phospholipid bilayer vary in size, shape + pattern
