Core Concepts: Lipids

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).