BIOLOGICAL MEMBRANES (2.1.5)

Question 1

describe the function of the plasma membrane

Answer 1

• partially permeable membrane between cell and environment
• involved in cell recognition (immune system)
• involved in cell communication/cell signaling

Question 2

describe the functions of membranes within cells

Answer 2

• divide cell into compartments (makes the organelles functions more efficient)
• can form transport vesicles of substances within cells (e.g. proteins to Golgi Apparatus)
• site of chemical reactions

Question 3

state the 6 components of the membrane

Answer 3

• phospholipids
• channel proteins (intrinsic)
• carrier proteins (intrinsic)
• glycoproteins (extrinsic)
• glycolipids
• cholesterol

Question 4

state and explain the function of phospholipids in the membrane

Answer 4

• arrange themselves into a bilayer
• phosphate hydrophilic head face outwards, towards water on either side of membrane
• hydrophobic tails face inwards

Question 5

what substances does the bilayer allow through and why?

Answer 5

• stops water-soluble substances (e.g. ions, polar molecules) through, due to its hydrophobic centre
• allows lipid-soluble substances (e.g. vitamins) to dissolve and pass directly through

Question 6

describe the structure of a phospholipids

Answer 6

• hydrophilic, polar phosphate head
• 2 hydrophobic, non-polar fatty acid tails

Question 7

describe and explain the role of intrinsic proteins

Answer 7

• span both bilayers of the plasma membrane
• due to hydrophobic amino acids on outside, allowing them to interact with hydrophobic phospholipid tails
• channel proteins lined with hydrophilic R groups allowing the diffusion of polar molecules down the concentration gradient