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).