1.1 biological molecules lipids

Question 1

What is a triglyceride?

Answer 1

-The most common types of lipid
-A molecule composed of one glycerol molecule and three fatty acids

Question 2

What type of bonds are used to join fatty acids to a glycerol molecule?

Answer 2

ester bonds

Question 3

What two molecules make up lipids?

Answer 3

glycerol and fatty acids

Question 4

What two groups are fatty acids made of?

Answer 4

organic molecules which have a -COOH carboxyl group attached to a long hydro-carbon tail.

Question 5

characteristics of lipids

Answer 5

-contains C,H, and O, much higher proportion to carbon than oxygen
-non polar compounds so insoluble in water
-soluable in organic solvants
-generally hydrophobic
-do not form polymers

Question 6

What characterises a saturated fatty acid?

Answer 6

-have no double bonds between neighbouring carbon atoms in the hydrocarbon tail however do only have single carbon atoms (normally found in animals)
-tend to be solid at room temperature.
-form straight chains and molecules align readily

Question 7

What characterises an unsaturated fatty acid?

Answer 7

-have double bonds between neighbouring carbon atoms in the hydrocarbon chain
-monounsaturated have one double bond-polyunsaturated have two or more double bonds (normally found in plants and solidifies at room temperature)
-cannot align uniformly

Question 8

phosolipids

Answer 8

form bilayers with the hydrophobic tails pointing inwards (away from water) and phosphate head faces outwards (towards aqueous surroundings)The phospholipid bilayer forms the basis of all cell membranes.The phosphate group is polar and therefore soluble in water.

Question 9

What molecules form a phospholipid?

Answer 9

A glycerol-phosphate head (hydrophilic) and two fatty acid chains (tails) (hydrophobic)

Question 10

Comparing triglycerides and phospholipids

Answer 10

Triglycerides
-3 fatty acid tails
-No phosphate group
-Non polar (completely hydrophobic) Phospholipids

Phosphate group
-2 fatty acid tails
-Polar head is hydrophilic, fatty acid tails are hydrophobic

Question 11

What risks are attributed to high intake of fat in our diet?

Answer 11

smoking, lack of exercise and ageing increase risk of heart disease (due to raised cholesterol levels leading to atheroma in arteries)

Question 12

functions of lipids

Answer 12

• energy storage
• thermal insulator
• protection
• metabolic water source
• waterproofing
• low density and buoyancy
• nerve transmission
• steroid and cholesterol
• cell membrane formation

Question 13

Energy reserve (store) in plants and animals

Answer 13

Triglycerides store twice as much energy as the same mass of carbohydrates, making it an efficient method of storage (In animals fat is stored under the skin and around organs, in plants triglycerides are stored as oils in seeds)

Question 14

thermal insulator

Answer 14

When stored under the skin it acts as a thermal insulator which reduces heat loss.

Question 15

protection

Answer 15

Fat is often stored around delicate organs such as the kidneys.

Question 16

metabolic water source

Answer 16

Triglycerides produce a lot of metabolic water when oxidised. This is essential for desert animals such as the kangaroo rat which never drinks water and survives on metabolic water from its fat intake

Question 17

waterproofing

Answer 17

Fats (being non-polar) are insoluble in water and are important in land organisms such as insects where the waxy cuticle reduces water loss. Leaves also have a waxy cuticle to reduce water loss by evaporation from the leaf surface.

Question 18

low density and buoyancy

Answer 18

Fat has a fairly low density and helps animals such as polar bears float in water; it increases their buoyancy. Seeds which store oils can also be easily dispersed as they are light.

Question 19

nerve transmission

Answer 19

Triglycerides form the myelin sheath which surrounds the axon of nerve cells (neurones) in vertebrates; the myelin sheath seeps up nerve transmission.

Question 20

steroids and cholesterol

Answer 20

Steroids, which include the sex hormones (testosterone and oestrogen), are lipids. They have a ring structure rather than a long chain structure.main function is cell signalling + as components of all membrane

Question 21

cell membrane formation

Answer 21

Phospholipids form a bilayer which is the basis of all cell membranes. The phospholipid bilayer allows for the transport of non-polar molecules across cell membranes by simple diffusion.