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Ocr Topic 3 Bio Molecules

The document covers key concepts in biological molecules, including monomers and polymers, carbohydrates, lipids, proteins, water properties, and inorganic ions. It explains the structure and functions of various biomolecules, such as the formation of carbohydrates from monosaccharides and the role of proteins in biological processes. Additionally, it highlights the importance of water and inorganic ions in biological systems.

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11 views2 pages

Ocr Topic 3 Bio Molecules

The document covers key concepts in biological molecules, including monomers and polymers, carbohydrates, lipids, proteins, water properties, and inorganic ions. It explains the structure and functions of various biomolecules, such as the formation of carbohydrates from monosaccharides and the role of proteins in biological processes. Additionally, it highlights the importance of water and inorganic ions in biological systems.

Uploaded by

qwerty2005
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© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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OCR A Level Biology A – Topic 3: Biological Molecules

1. Monomers and Polymers

 Monomers: Small, basic molecular units (e.g., monosaccharides, amino acids,


nucleotides).
 Polymers: Large, complex molecules composed of long chains of monomers joined
together.
 Polymerization: The process of joining monomers to form a polymer through
condensation reactions, which release water molecules.
 Hydrolysis: The breakdown of polymers into monomers by the addition of water.

2. Carbohydrates

 Monosaccharides: Simple sugars like glucose, fructose, and galactose.


o Glucose: Exists in two isomers—α-glucose and β-glucose.
 Disaccharides: Formed by condensation reactions between two monosaccharides.
o Examples:
 Maltose = glucose + glucose
 Sucrose = glucose + fructose
 Lactose = glucose + galactose
 Polysaccharides: Large carbohydrates formed from monosaccharides.
o Starch: Energy storage in plants; composed of amylose (unbranched) and
amylopectin (branched).
o Glycogen: Energy storage in animals; highly branched structure.
o Cellulose: Structural component in plant cell walls; composed of β-glucose
units forming straight chains linked by hydrogen bonds.

3. Lipids

 Triglycerides: Composed of one glycerol molecule and three fatty acids; formed via
condensation reactions creating ester bonds.
o Saturated fatty acids: No double bonds between carbon atoms.
o Unsaturated fatty acids: One or more double bonds; can be monounsaturated
or polyunsaturated.
 Phospholipids: Similar to triglycerides but one fatty acid is replaced by a phosphate
group; essential components of cell membranes.
 Cholesterol: A lipid molecule that helps maintain fluidity and stability of cell
membranes.

4. Proteins

 Amino Acids: Building blocks of proteins; contain an amino group (-NH₂), a


carboxyl group (-COOH), and a variable R group.
 Peptide Bonds: Formed between amino acids through condensation reactions.
 Protein Structure:
o Primary: Sequence of amino acids.
o Secondary: Folding into α-helices and β-pleated sheets via hydrogen bonding.
o Tertiary: 3D structure formed by interactions between R groups (e.g., ionic
bonds, disulfide bridges).
o Quaternary: Complexes of multiple polypeptide chains.
 Functions: Enzymes, hormones, antibodies, structural components.

5. Water

 Properties:
o Polarity: Uneven distribution of charge allows hydrogen bonding.
o Cohesion: Attraction between water molecules; important for transport in
plants.
o High Specific Heat Capacity: Buffers temperature changes.
o Solvent: Dissolves ionic and polar substances.
o Density: Ice is less dense than liquid water; insulates aquatic habitats.

6. Inorganic Ions

 Roles:
o Hydrogen ions (H⁺): Determine pH.
o Iron ions (Fe²⁺): Component of hemoglobin.
o Sodium ions (Na⁺): Involved in nerve impulse transmission.
o Phosphate ions (PO₄³⁻): Component of DNA and ATP.

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