Lipids

Question 1

Lipids

Answer 1

Known as fats (solids) and oils (liquid)
Contain oxygen, hydrogen and carbon 
Lipids are non polar 
Lipids are non soluble in water 
Complex molecules called macromolecules

Question 2

Difference between macromolecules and polymers

Answer 2

Macromolecules are built from large molecules whilst polymers consist of repeating molecules

Question 3

Triglycerides

Answer 3

Compound made up of one glycerol molecule (alcohol) and 3 fatty acids (carboxylic acid)

• Hydroxyl groups interact forming an Ester bond and three water molecules
• condensation process is called esterification
• When triglycerides are broken down, 3 water molecules are needed

Question 4

Saturated fatty acid

Answer 4

Fatty acid chains have no double bonds present between the carbons
All the carbon atoms form the max number of bonds with the hydrogen atoms

Question 5

Unsaturated fatty acids

Answer 5

A fatty acid with double bonds between some of the carbon atoms is called unsaturated
One double bond = monounsaturated
Two double bonds = polyunsaturated
Presence of double bonds causes molecule to kink/bend and therefore cannot pack closely together
Makes them liquid at room temperature = oils

Question 6

Unsaturated vs saturated fatty acids

Answer 6

Plants contain unsaturated triglycerides (oil) and these tend to be healthier in the human diet than saturated triglycerides (solid fats)
Research suggest that excess saturated fats can lead to coronary heart disease
Excess of any fat can lead to obesity and put a strain on the heart

Question 7

Phospholipids structure

Answer 7

Modified triglycerides
Contains phosphorus, carbon, hydrogen and oxygen
Inorganic phosphate ions (PO4,-3) are found in the cytoplasm of every cell
Phosphate ions have extra electrons and so are negatively charged, making them soluble in water
One of the fatty acid chains in the triglyceride molecule is replaced with a phosphate group to make a phospholipid

Question 8

Phospholipid charges

Answer 8

They have non polar tail (fatty acid chains)and a charged head (phosphate group)
Non-polar tails = hydrophobic
Charged heads = hydrophilic

Question 9

How do phospholipids interact with water molecules

Answer 9

When interacting with water, they form a layer on the water with the phosphate heads in the water and the fatty acid tails sticking out
Called surface active agents/ surfactants

Question 10

Phospholipid bilayer

Answer 10

Two layered sheet formation
Hydrophobic tails pointing to the centre of the sheet protected from the water by the hydrophilic heads
Plays a key roles in forming membranes
Able to separate an aqueous environment in which cells usually exist from aqueous cytosol within cells

Question 11

Sterols

Answer 11

Steroid alcohols
Type of lipid found in cells
NOT FATS OR OILS
complex alcohol molecule based on a 4 carbon ring structure with OH group on one end
OH group is polar and hydrophilic so rest of the molecule is hydrophobic

Question 12

Cholesterol

Answer 12

Type of sterol
Body manufactures it in the liver and the intestines
Has important role in the formation of cell membranes
Positioned between the phospholipids with the OH group at the edge of the membrane
Adds to the stability of the cell membrane
Regulates fluidity by keeping membranes fluid at low temps and stopping them becoming too fluid at high temps
Vitamin D, sterol hormones and bile are all manufactured using cholesterol

Question 13

Roles of lipids

Answer 13

Biological roles due to polar nature:

• membrane formation + creation of hydrophobic barriers
• hormone production
• electrical insulation necessary for impulse transmission
• water proofing EG birds’ feathers, plant leaves

Long term energy storage roles stored unter the skin and around vital organs providing:

• there mal insulation to reduce heat loss
• cushioning in order to protect vital organs
• buoyancy for aquatic animals