Core Concepts: Lipids

What three biological molecules do lipids contain?

What three biological molecules do lipids contain?

Carbon, Hydrogen and Oxygen

What unique component do phospholipids have?

Phosphorus

True/ False: Lipids dissolve in water

False: They are non-polar + do not dissolve in water

Lipids dissolve in nonpolar substances. True/False?

True - i.e other lipids

Why are lipids suited as energy storage/sources?

1 gram of fat provides twice as much energy as the same mass of carbohydrates

Give 5 functions of lipids

• Protects the delicate internal organs like the kidneys

• Oxidation of triglycerides produces metabolic water- cools camels down

• Phospholipids are a key component in cell membranes

• Leaves have a waxy cuticle layer to reduce water loss

• Fats are poor conductors of heat meaning they retain body heat

What makes up a triglyceride?

Glycerol + 3 fatty acids

Describe the features of a fatty acids have

• Long molecules

• Polar hydrophilic end + non-polar hydrophobic tail

What are saturated fatty acids?

Fatty Acids in which all carbon atoms are joined by single bonds in the hydrocarbon chain (SATURATED WITH HYDROGEN)

Describe 2 features of saturated fatty acids

• Straight chains

• High melting points

Why do saturated fatty acids have a high melting point?

This is because the fatty acid tails are straight and can pack closely together. Stronger forces of attraction can form which means more energy is needed to break the bonds and melt the fat

At room temperature, saturated fatty acids are _____

Fats

What are unsaturated fatty acids?

Fatty acids where not every carbon is saturated with hydrogens - there must be one or more double bonds

What are unsaturated fatty acids with more than one double bond called?

Polyunsaturated fatty acids

At room temperature, unsaturated fats are_____

Oil

Why do unsaturated fatty acids have low melting points?

The double bonds make the fatty acid tails less straight so they cannot pack as closely together. The forces of attraction between the fatty acids are weaker, so less energy is needed to break the bonds and melt the fat

Describe the formation of triglycerides

• 1 molecule of glycerol joins with 3 fatty acid molecules to form a triglyceride

• This happens in a condensation reaction

• A water molecule is removed and an ester bond is formed

Are triglycerides polymers?

No (duh) - they are made of only one glycerol and 3 fatty acids which have different structures

What is the structure of phospholipids?

• 1 molecule of glycerol

• A hydrophilic phosphate head

• 2 hydrophobic fatty acid chains

Describe a phospholipid bilayer

• The hydrophilic phosphate groups are attracted to water molecules in the cytoplasm and outside the cell.

• The hydrophobic tails are repelled by water molecules turn away from water in the cytoplasm and outside the cell

What is meant by membrane fluidity?

How easy it is for the cell membrane to move

How do phospholipids affect the fluidity of membranes?

• Phospholipids where only saturated fatty acids are present are the least fluid

• Phospholipids where only unsaturated fatty acids are present are the most fluid

What are the two main causes of heart disease?

fatty deposits on the inner wall of the coronary artery (atherosclerosis) and hypertension

Name 3 contributing factors to heart disease

• Diet - high in saturated fats

• Smoking

• Lack of exercise

What happens to lipids and proteins after they’ve been absorbed into the small intestine?

They become lipoproteins which travel around the body in the bloodstream

If a diet is high in saturated fats…

• LDL builds up + causes harm

• Atheroma (fatty material) is deposited in the coronary arteries

• This restricts blood flow + oxygen delivery to the heart

• This causes angina + may cause a heart attack

If a diet is high in unsaturated fats…

• Makes more HDL

• This carries away harmful fats to the liver for disposal

The higher the HDL : LDL ratio, the lower their risk of heart disease

What is polyunsaturated fat?

An essential fat that we must get from food because our bodies cannot produce it. It lowers LDL (bad cholesterol)

Where is polyunsaturated fat found?

Omega-3 in fish

What is monounsaturated fat?

‘Healthy Fat’ - lowers LDL and maintains HDL

Where is monounsaturated fat found?

Olive oil, nuts and avocado

What is Trans fat?

By-product of processing healthier fats to give them a longer shelf life. Raises LDL (bad cholesterol) and lowers HDL (good cholesterol).