Lipids and Membranes M2

Question 1

Outline the role of cholesterol in the phospholipid bilayer

Answer 1

they fit in between phospholipid lipid molecules, causing them to pack more tightly together. More fluid at low temperature and more rigid at high temperatures.

Question 2

State two functions of membranes within the cell.

Answer 2

1. the nuclear envelope allows mRna to be secreted, but DNA is to large to pass through. 2. membrane in the mitochondria holds reactants for respiration together.
2. the inner membrane increases the surface area for number of enzymes present

Question 3

Describe the structure of phospholipids.

Answer 3

one molecule of glycerol, two fatty acids and 1 phosphate group, 2 ESTER BONDS

Question 4

Describe the structure of a triglyceride.

Answer 4

one molecule of glycerol and three fatty acids, 3 ESTER BONDS

Question 5

Explain how cell surface membranes contribute to the process of cell signalling.

Answer 5

1. release of signal cells by EXOCYTOSIS 2. GLYCOPROTIENS have receptors, that is SPECIFIC and COMPLEMENTRY. 3. the attachment of a signal cell causes a change in the cell. 4. cell surface membrane allows the entry of some signal molecules

Question 6

Explain the difference between a saturated fatty acid and an unsaturated fatty acid.

Answer 6

a saturated fatty acid tail does not have a double bond whereas an unsaturated does.

Question 7

Roles of lipids in living organisms (lipid functions)

Answer 7

hormones like steroids. protection of vital organs. hydrolyse to water. hair/skin oils. insulation ie myelin sheath. membranes. high energy yield

Question 8

Solubility of Lipids

Answer 8

Insoluble in water so therefore do no affect osmotic potential

Question 9

Emulsion test in seeds

Answer 9

1. CRUSH a sample of the seeds 2. add 2cm3 of ETHANOL, stir and mix well. 3. Pipette distilled WATER into the sample with ethanol and mix well. 4. If a positive result will form an emulsion and go CLOUDY WHITE

Question 10

Functions of the plasma membrane

Answer 10

Cell recognition. Partially permeable barrier. Transport of key molecules. Cell signalling.

Question 11

Red blood cell- isotonic, hypertonic, hypotonic

Answer 11

isotonic - normal cell inside=outside, hypertonic - cell BURST, due to weak membrane, outside>inside. hypotonic - SHRIVELLED, inside>outside

Question 12

Plant cell- isotonic, hypertonic, hypotonic

Answer 12

isotonic - normal cell, inside=outside. hypertonic - turgid, due to tough cellulose walls. hypotonic - flaccid, inside>outside

Question 13

Describe the structure of a plasma membrane

Answer 13

1. contain carrier/channel protein. 2. hydrophilic region facing outward, a hydrophobic region facing inwards.
2. chloresteral in between bilayers 4. Extrinsic and intrinsic proteins

Question 14

Name the components of the cell surface membrane.

Answer 14

phospholipids, proteins, glycoproteins, cholesterol and glycolipids

Question 15

water potential

Answer 15

pure water = water potential zero. Adding solutes cause water [potential to decrease and become more negative

Question 16

osmosis

Answer 16

the net movement of water particles from an area of high water potential to an area of low water potential down a water potential gradient until equilibrium, across a partially permeable membrane

Question 17

What is the fluid mosaic model

Answer 17

FLUID - represents parts that can move freely. MOSAIC - refers to various proteins distributed through the bilayer

Question 18

Membrane receptor

Answer 18

proteins in the membrane act as receptors for messenger molecules. receptor proteins have specific shapes, complementary shapes bind with them. Drugs works by binding to receptors and triggering a response, receptor allows drugs to target specific cells

Question 19

factors affecting the membrane permablity/structure

Answer 19

temp decrease = perm decrease, no energy, becomes rigid and does not move. temp increase = perm increase, more kinetic energy, more movement until denataring occurs. Solvent increase = perm increase, some solvents dissolve lipids so it loses its structure.