▪️🔹1.1 Lipids -Chemical Elements

Question 1

What do lipids contain?

Answer 1

Carbon, hydrogen and oxygen, less oxygen than carbon and hydrogen (in proportion)

Question 2

What makes lipids insoluble in water

What do lipids dissolve in?

Answer 2

The fact they are non-polar compounds

They dissolve in organic solvents such as propanone and alcohols

Question 3

What from triglycerides?

Answer 3

Combination of one glycerol molecule (stays the same) and three fatty acid molecules (these component can vary)

Question 4

How to the fatty acids joint to glycerol?

Answer 4

By condensation reactions where 3 molecules of water are removed and water bonds are formed between the glycerol and fatty acids

Question 5

Describe why phospholipids have one end soluble and one end insoluble

Answer 5

-One end of a phospholipid has lots of oxygen atoms which interacts with water and is hydrophilic (polar head of the molecule)
-fatty acid tails do not have any oxygen atoms and don’t interact with water so they are hydrophobic (non-polar)
(LOOK AT DIAGRAM)

Question 6

What are waxed?

What temperature do waxed melt at?

Answer 6

Waxes are lipids that melt above 45 degrees

Question 7

Name a role of waxes

Answer 7

Waterproofing role In animals (insect exoskeleton) and the leafs outer cuticle

Question 8

What makes a fatty acid saturated?

Answer 8

When the hydrocarbon chain has only single carbon-carbon bonds

Question 9

When is a fatty acid unsaturated

What does this cause

Answer 9

When any of the carbon-carbon bonds is not a single bond

This causes a kink in the fatty acid chain

Question 10

What does the kink in a fatty acid chain cause

Answer 10

Causes the molecules to not align uniformly, meaning the lipid does not solidify :: unsaturated lipids are oils

Question 11

What are plant lipids usually?

Answer 11

Usually unsaturated e.g olive oil and sunflower oil

Question 12

What does mono-unsaturated mean?

What does polyunsaturated mean?

Answer 12

There is one carbon-carbon double bond (mono)

There are many carbon-carbon double bonds (poly)

Question 13

Name the roles of phospholipids

Answer 13

• biological membranes

- electrical insulation (around nerve cells)

Question 14

Name the roles of triglycerides

Answer 14

• energy reserves in both plants and animals
• thermal insulation (stored under the skin to insulate against heat loss in cold or heat gain when hot)
• protection (fats stored around delicate organs such as kidneys, protecting against damage)
• metabolic water (water released during chemical reactions in the body)

Question 15

Name a test to identify fats and oils

Answer 15

The emulsion test,
Add ethanol to a sample (dissolves lipids) and shake with equal volume of water
They form a cloudy white emulsion

Question 16

Name the 2 main causes of heart disease

Answer 16

• fatty deposits in the coronary arteries (artherosclerosis)
• High blood pressure (hypertension)

Question 17

What happens when food has been absorbed into the small intestine?

Answer 17

Lipids and proteins combine to make lipoproteins which travel around the body in the blood stream

Question 18

What happens if a persons diet is high in saturated fats?

Answer 18

Low density lipoproteins (LDL) build up as atheroma in the coronary arteries, restricting blood flow and oxygen delivery to the heart, if the vessel is completely blocked a heart attack occurs

Question 19

What happens if a persons diet has a high proportion of unsaturated fats?

Answer 19

The body makes more Hugh density lipoprotein (HDL) which carries harmful fats away to the liver for disposal.
The higher the HDL:LDL in a persons blood the lower the risk of cardio-vascular disease

Question 20

Suggest why plants store energy as lipids

Answer 20

• lipids contain twice as much energy as carbohydrates

- lipids are osmotically inert :: don’t effect the water potential of cells

Question 21

Through which part of the membrane would a lipid soluble molecule pass?

Answer 21

Through the lipid tail of phospholipids in the bilayer