Carbohydrates and lipids

**Four** — this lets carbon build chains, branches and rings.

Each carbon forms **four covalent bonds** and bonds to itself and other elements, so it builds a huge variety of molecule shapes.

A very large molecule built from **many smaller repeating subunits** (e.g. a polysaccharide, protein or nucleic acid).

A single small subunit that can be joined to others to build a larger molecule (e.g. glucose, an amino acid).

A large molecule made of **many monomers** joined together (e.g. starch).

A reaction that **joins two subunits** and **releases one water molecule (H₂O)**.

A reaction that **uses one water molecule (H₂O)** to break a bond and split a molecule into two subunits.

**Condensation** — it joins monomers and removes water.

**Hydrolysis** — it adds water to split the bonds.

**Anabolic** — it builds larger molecules from smaller ones.

**Catabolic** — it breaks larger molecules into smaller ones.

One **water molecule is released** (removed) each time a bond forms.

One **water molecule is used** (added) to break each bond.

They are macromolecules built from **smaller subunits joined by condensation**, releasing water.

'**Hydro**' = water, '**lysis**' = splitting — splitting a molecule using water.

A **single sugar unit** — the **monomer** of a carbohydrate (e.g. glucose, fructose, galactose).

A sugar made of **two monosaccharides joined together** (e.g. maltose, sucrose, lactose).

**C₆H₁₂O₆**.

Molecules with the **same chemical formula** but a **different arrangement of atoms**.

The **direction of the -OH group on carbon 1**: it points **down** in alpha-glucose and **up** in beta-glucose.

A reaction that **joins two molecules** together and **releases a molecule of water** (H₂O).

A reaction that **adds water** to **break a bond** — the reverse of condensation.

A **glycosidic bond**.

The disaccharide **maltose** **and** a molecule of **water**.

**Glucose + glucose**.

**Glucose + fructose**.

**Glucose + galactose**.

It is **small and soluble in water**, so it dissolves in the plasma and is carried around the body.

It is the **main respiratory substrate** — it is broken down in respiration to release energy (ATP).

A large molecule (polymer) made of **many monosaccharides** joined together.

**Glucose** — a monosaccharide.

**Starch** (energy store in plants), **glycogen** (energy store in animals), **cellulose** (structural support in plant cell walls).

**Alpha-glucose**.

**Beta-glucose**.

**Alpha-glucose** chains that are **coiled (helical) and lightly branched**.

**Alpha-glucose** chains that are **highly branched** (even more than starch).

**Beta-glucose** in **long, straight, unbranched chains** that hydrogen-bond into **fibres**.

It is a **large/compact glucose polymer** (lots of energy), **insoluble** (no effect on osmosis), and **branched** (many ends for fast glucose release).

It does **not dissolve**, so it does **not affect the cell's water balance** (osmosis) and stays as a store.

Branches give **many free ends**, so glucose can be **added or removed quickly** by hydrolysis when energy is needed.

Straight **beta-glucose** chains **hydrogen-bond** side by side into strong **fibres**, which support the **plant cell wall**.

It provides **structural support** — its fibres strengthen the **cell wall**.

We lack the enzyme to break its **beta-glucose** links, so it passes through as dietary **fibre**.

**Condensation** — each link **releases one water molecule (H₂O)**.

**One glycerol** joined to **three fatty acids**.

A small **3-carbon** molecule with **three —OH (hydroxyl) groups**; it forms the **backbone** of a triglyceride.

A long **hydrocarbon chain** ending in a **—COOH (carboxyl) group**, which is where it joins the glycerol.

An **ester bond**.

**Three** — one for each of the three fatty acids.

**Condensation** — it forms the ester bonds and **removes water** (one H₂O per bond, three in total).

**Hydrolysis** — it **adds water** (three H₂O) to break the three ester bonds.

**One glycerol** and **three fatty acids**.

Its carbon chain has **only single C–C bonds** — it holds the **maximum** hydrogen and the chain is **straight**.

Its chain has **one or more C=C double bonds**, which put a **kink** in the chain.

Look for a **C=C double bond** (and a **kink**) in the carbon chain.

Their **kinked chains** cannot pack closely together, so they stay **liquid**.

**Saturated** fats are usually **solid** (e.g. butter); unsaturated are usually **liquid oils** (e.g. olive oil).

**Three** — one per ester bond formed by condensation.

The **triglyceride** — one **glycerol** joined to **three fatty acids**.

In **adipose tissue** — fat-storage cells under the skin and around organs.

About **twice** as much energy **per gram**.

Their long **fatty-acid tails** contain many energy-rich **C–H bonds** and little oxygen.

**Insoluble** — the fatty-acid tails are **hydrophobic** (water-repelling).

Fat does not dissolve in the cell or draw water in by **osmosis**, so large amounts can be stored without upsetting the cell's water balance.

**Water-repelling** — a non-polar part that does not mix with or dissolve in water.

Animal tissue made of **fat-storage cells**; it stores triglycerides and forms an **insulating layer** under the skin.

**Thermal insulation** (slows heat loss) and **protection / cushioning** of organs.

Glucose has many polar **–OH groups** that attract water; a triglyceride's tails are **non-polar / hydrophobic**, so they do not.

**Lipid** (triglyceride fat) is the long-term, high-capacity store; **carbohydrate (glycogen)** is the short-term, quick store.

It holds lots of energy and carries no extra water, so it stores the **same energy for less mass**.

The energy-storage lipid: one **glycerol** molecule joined to **three fatty acids**.

**Pair it with its reason** — e.g. insoluble BECAUSE hydrophobic; high energy BECAUSE many C–H bonds.

A lipid made of **one glycerol, two fatty acids and a phosphate-containing head**.

Having **both a hydrophilic (water-loving) part and a hydrophobic (water-fearing) part** in the same molecule.

**Water-loving** — attracted to and mixes with water.

**Water-fearing** — does not mix with water; repelled by it.

The **phosphate group** (with the glycerol) — it is **polar**, so it is attracted to water.

The **two fatty-acid tails** — they are **non-polar**, so they are repelled by water.

Because the **same molecule** has a **hydrophilic head AND hydrophobic tails**.

By **condensation reactions** that join the fatty acids and phosphate to glycerol, **releasing water (H₂O)**.

Both use one glycerol, but a phospholipid has **2 fatty acids + a phosphate head**, while a triglyceride has **3 fatty acids and no phosphate**.

They **self-arrange into a bilayer**: hydrophilic heads face the water on both sides, hydrophobic tails tuck into the middle.

The **cell (plasma) membrane** — the boundary around every cell.

**Inwards**, towards the middle — away from the water on both sides.

A **triglyceride** (fully hydrophobic) or **glucose** (fully hydrophilic) — each is only one or the other.

**Glycerol** — the fatty-acid tails and the phosphate head all attach to it.