Cell Surface Membrane

Question 1

What is cell membrane made of ?

Answer 1

• phospholipids bilayer
• protein
• cholesterol
  -glycolipids
• glycoproteins

Question 2

Fluid Mosaic model

Answer 2

• 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

Question 3

Phospholipids bilayer

Answer 3

• hydrophilic heads point outside of the cell membrane = attracts water
• hydrophobic tail of fatty acids point inwards = repels water

Question 4

Functions of phospholipids bilayer

Answer 4

• allow lipid soluble in/ out of cell membrane
• prevent water soluble in/out cell membrane
• make membrane flexible and self sealing

Question 5

Extrinsic proteins

Answer 5

-embedded in phospholipids bilayer
- in surface of bilayer

Question 6

Functions of extrinsic proteins

Answer 6

• give mechanical strength to membrane
• join with to form glycoproteins/ lipids as cell receptors e.g.hormones

Question 7

Intrinsic proteins

Answer 7

• involved in transport of molecules across membranes
• span across one side of bilayer to other

Question 8

Functions of channel proteins

Answer 8

• form tubes that fill with water = enable water soluble ions to diffuse

Question 9

Functions of carrier proteins

Answer 9

• bind with large molecules e.g. glucose + amino acids and change shape to transport to other side of membrane

Question 10

Cholesterol

Answer 10

• 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

Question 11

Functions of cholesterol

Answer 11

• reduce lateral movement of other molecules
• maintain fluidity at high temperature
• strength bilayer by preventing

Question 12

Functions of glycolipids

Answer 12

• 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

Question 13

Functions of glycoproteins

Answer 13

• act as cell receptors
• help cells to attach one another to form tissues
• allow cell recognition

Question 14

What type of molecules cannot pass through partial permeable membrane ?

Answer 14

• 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)