Cell Surface Membrane Flashcards
What is cell membrane made of ?
- phospholipids bilayer
- protein
- cholesterol
-glycolipids - glycoproteins
Fluid Mosaic model
- fluid gives membrane a flexible structure that can constantly change shape = bec. Individual phospholipids can move
- mosaic = bec. Proteins embedded in phospholipids vary in shape and size
Phospholipids bilayer
- hydrophilic heads point outside of the cell membrane = attracts water
- hydrophobic tail of fatty acids point inwards = repels water
Functions of phospholipids bilayer
- allow lipid soluble in/ out of cell membrane
- prevent water soluble in/out cell membrane
- make membrane flexible and self sealing
Extrinsic proteins
-embedded in phospholipids bilayer
- in surface of bilayer
Functions of extrinsic proteins
- give mechanical strength to membrane
- join with to form glycoproteins/ lipids as cell receptors e.g.hormones
Intrinsic proteins
- involved in transport of molecules across membranes
- span across one side of bilayer to other
Functions of channel proteins
- form tubes that fill with water = enable water soluble ions to diffuse
Functions of carrier proteins
- bind with large molecules e.g. glucose + amino acids and change shape to transport to other side of membrane
Cholesterol
- occur in phospholipids bilayer
- very hydrophobic = prevent water loss and dissolved ions from the cell
Limit movement of fatty acids tails = prevent membrane goes to rigid
Functions of cholesterol
- reduce lateral movement of other molecules
- maintain fluidity at high temperature
- strengthen bilayer by interaction with other hydrophobic tails
Functions of glycolipids
- act as cell receptors
- help maintain stability of membrane
- help cells to attach to one another to form tissues
- allow cell recognition of one another
Functions of glycoproteins
- act as cell receptors
- help cells to attach one another to form tissues
- allow cell recognition
What type of molecules cannot pass through partial permeable membrane ?
- too large e.g. glucose
- not soluble in lipids = can’t pass through bilayer
- same charge as protein channels will repel
- electrically charged (polar)= cannot pass through hydrophobic tails (non polar)
E.g. what are 2 advantages of giving results as a ratio (2)
- easier to draw comparison
- discs may had different starting masses
E.g. explain how taking editorial readings can improve reliability of results ? (2)
- so anomalies can be identified
- a mean value can be calculated
Factors affecting membrane’s permeability (4)
- high temperature
- extreme PH
- proportions of saturated and unsaturated fatty acids
- use of ethanol or detergent as solutions = dissolve phospholipid
How does temperature and PH affect permeability ?
High temp= phospholipid gain more KE = move more = membrane structure more fluid = more gaps to let pigments diffuse out, also denatures transport proteins = substances easily diffuse out
Extreme PH = denatures proteins = diffusion of substances quicker out
How does saturated or unsaturated FA affect membrane permeability ?
- more unsaturated C=C = the phospholipid tails are not straight = causes more gaps in between = pigments can diffuse out easily
- C—C bond saturated = tails lined more straight = no gaps to allow pigments diffuse out
