Topic 2 -BIOLOGICAL MOLECULES - In Progress

Topic 2

Describe the features of a Carbohydrate.

• Cells use Carbohydrates as a source of Energy and a way of Storing energy.

• The source of energy is usually small, simple Sugars such as Glucose.

• Plants can store this in the form of Starch, whilst Animals store it as Glycogen.

• Carbohydrates are made of three elements: Carbon, Hydrogen, and Oxygen.

• Carbohydrates are organised into different groups based on their size.

Define Carbohydrates.

Carbohydrates are a group of substances used as both energy sources and structural materials in organisms.

Identify and Define the three main groups of Carbohydrates.

1. Monosaccharides.

   • These are simple sugars.

2. Disaccharides.

   • These are ‘double sugars’, formed from two Monosaccharides.

3. Polysaccharides.

   • These are large molecules formed from many monosaccharides.

Identify the two different types of Monosaccharides.

1. Pentose Sugars.

2. Hexose Sugars.

Give two examples of important Pentose Molecules.

1. Ribose.

2. Deoxyribose.

Name the three most important Hexose Molecules.

1. Glucose.

2. Galactose.

3. Fructose.

Define Glucose.

Glucose.

• Glucose is an abundant and very important Monosaccharide. It contains 6 carbon atoms so it is a Hexose sugar.

• Its general form is C6H12O6.

Identify the two different structures of Glucose.

1. Alpha-Glucose.

2. Beta-Glucose.

Describe the structure of Alpha-Glucose. (Image)

Describe the structure of Beta-Glucose. (Image)

Describe the structure of Galactose.

• Not as soluble as Glucose.

• Produces Glycolipids and Glycoprotein.

Describe the structure of Fructose.

• Very soluble and sweet.

• Main sugar in fruit and nectar.

Describe a Disaccharide and give the three examples.

• Disaccharides are made up of two Monosaccharides joined together by a Glycosidic bond.

1. Maltose.

2. Sucrose.

3. Lactose.

Describe the structure of Maltose.

Formula:

• a-Glucose + a-Glucose.

• Joined by an Alpha 1-4 Glycosidic bond.

Found in:

• Germinating Seeds.

Describe the structure of Sucrose.

Formula:

• a-Glucose + Fructose.

• Joined by an Alpha 1-4 Glycosidic bond.

Found in:

• Sugar Cane (Table Sugar).

Describe the structure of Lactose.

Formula:

• a-Glucose + B-Glucose.

• Joined by a Beta 1-4 Glycosidic bond.

Found in:

• Milk.

Define Condensation Reaction.

A Condensation Reaction occurs in order to form a glycosidic (covalent) bond between two monosaccharides.

• In a condensation reaction, water is removed to form the bond.

Define Hydrolysis Reaction.

A Hydrolysis Reaction is an opposite reaction to split disaccharides into monosaccharides (water is put in).

Describe the features of a Polysaccharide.

• Large.

• Insoluble.

• Suitable for storage (Glycogen) or structural support (Cellulose).

• Examples: Glycogen, Cellulose, and Starch.

Describe the structure of Starch.

• Made up of chains of a-Glucose, and is a polysaccharide.

• Found in plants.

• There are two types of Starch:

  → Amylose.

  → Amylopectin.

Describe the structure of Amylose.

Made up of 1-4 glycosidic bonds, this causes the molecule to coil into a spiral.

Describe the structure of Amylose.

A branched polymer of a-Glucose made from a combination of 1-4 glycosidic bonds and 1-6 glycosidic bonds.

Describe and Explain the features of Starch that make it a good Storage molecule.

1. Insoluble in water, so does not affect water potential.

2. Branched/coiled, so makes molecules more compact.

3. The polymer of a-glucose so provides glucose for respiration.

4. Branched so more ends for fast breakdown/enzyme action.

5. Large molecule, so cannot cross the cell membrane.

Describe the structure of Glycogen.

• Chains of a-Glucose monosaccharides.

• Has 1-4 and 1-6 glycosidic bonds.

• Only found in Animals and Bacteria.

• Major Carbohydrate storage product of animals (stored in small granules in muscles and liver).

Describe the structure of Glycogen related to function.

• Insoluble → No osmosis or diffusion.

• Compact → Stored in a small space.

• More highly branched → More ends can be acted on simultaneously by enzymes and more rapidly broken down to form a-glucose monomers.

Describe the structure of Cellulose.

• Made up of chains of B-glucose monosaccharides linked by glycosidic bonds.

• 1-4 glycosidic bonds.

• Straight, unbranched chains that run parallel to one another, allowing hydrogen bonds to form cross-linkage between adjacent chains.

  → Many hydrogen bonds strengthening cellulose.

Describe the structure of Cellulose related to function.

• Long/straight unbranched chains of B-glucose.

• Hydrogen bonding.

• To form (micro/macro) fibrils.

• Provides rigidity and strength.

Describe the features of a Lipid.

• Contains Carbon, Hydrogen and Oxygen.

• Does not make polymers.

• Ester bonds.

• Insoluble in water.

• Soluble in organic solvents.

• Proportions of Oxygen to Carbon and Hydrogen is smaller than in Carbs.

• Two main groups of Lipids:

  → Triglycerides (fats and oils).

  → Phospholipids.

Describe the role of Lipids.

• Source of energy: When oxidised provides less than twice the energy as the same mass of carbs (and releases valuable water).

• Waterproofing: Insoluble in water.

• Insulation: Slow conductors of heat (retain body heat) and electrical insulators in myelin sheath around nerve cells.

• Protection: Stored around organs.