Biology mock

1. Water as the medium for life (A1.1.01)

Life originated in water, and it continues to be the environment where most biological processes occur due to its unique properties such as solvency and thermal stability.

2. Hydrogen bonds in water (A1.1.02)

Water molecules are polar due to uneven electron sharing (oxygen is more electronegative). This polarity causes hydrogen bonds to form between molecules, giving water its unique properties.

3. Cohesion of water molecules (A1.1.03)

Cohesion arises from hydrogen bonding, allowing water to move under tension in xylem (plants) and enabling surface tension, which supports organisms like water striders.

4. Adhesion of water (A1.1.04)

Water adheres to polar or charged surfaces (e.g., plant cell walls), enabling capillary action, which is vital for water transport in plants.

5. Solvent properties (A1.1.05)

Water dissolves hydrophilic substances, facilitating metabolic reactions and nutrient transport in organisms. Hydrophobic molecules do not dissolve, maintaining cell membrane integrity.

6. Physical properties and aquatic habitats (A1.1.06)

Water’s buoyancy, viscosity, and high specific heat capacity make it ideal for aquatic life. For example, the black-throated loon relies on buoyancy for swimming, while the ringed seal benefits from water's thermal stability.

7. Extraplanetary origin of water (A1.1.07)

Earth's water likely came from asteroids. Gravity and suitable temperatures allowed its retention, enabling life to evolve over billions of years.

8. Search for extraterrestrial life and water (A1.1.08)

The presence of liquid water is considered a key indicator of potential life. Planets in the "Goldilocks zone" (habitable temperature range) are prime candidates for exploration.

Carbohydrates

9. Carbon’s chemical properties (B1.1.01)

Carbon's ability to form four covalent bonds allows the creation of diverse molecules, including long chains and rings crucial for life.

10. Macromolecule production (B1.1.02)

Condensation reactions join monomers (e.g., glucose) into polymers like polysaccharides, releasing water in the process.

11. Hydrolysis of polymers (B1.1.03)

Polymers are broken into monomers by adding water, critical for digestion and energy release.

12. Monosaccharides form and function (B1.1.04)

Simple sugars like glucose are soluble and energy-rich. Their stability and transportability make them vital for metabolism.

13. Polysaccharides as energy storage (B1.1.05)

Polysaccharides like starch (plants) and glycogen (animals) store energy efficiently due to their compact, branched structures.

14. Structure of cellulose (B1.1.06)

Cellulose is a structural polysaccharide in plants. Its beta-glucose monomers form straight chains, cross-linked by hydrogen bonds for strength.

15. Glycoproteins and cell recognition (B1.1.07)

Glycoproteins, like ABO blood antigens, are essential for cell recognition and immune responses.

Lipids

16. Hydrophobic properties (B1.1.08)

Lipids, including fats and steroids, are nonpolar and insoluble in water, making them ideal for energy storage and membrane formation.

17. Triglycerides and phospholipids (B1.1.09)

Triglycerides are formed by glycerol and three fatty acids. Phospholipids include two fatty acids and a phosphate group, forming cell membranes.

18. Fatty acid types (B1.1.10)

Saturated fatty acids lack double bonds (solid at room temp). Unsaturated fats have double bonds, reducing their melting points.

19. Triglycerides in energy storage (B1.1.11)

Triglycerides store energy densely and provide insulation, crucial for maintaining body temperature in cold environments.

20. Phospholipid bilayers (B1.1.12)

Phospholipids are amphipathic (hydrophilic heads, hydrophobic tails), forming bilayers that make up cell membranes.

21. Steroids and membrane passage (B1.1.13)

Nonpolar steroids like testosterone and oestradiol easily pass through membranes due to their hydrophobic nature.

Unit 1.2: Proteins, Enzymes, Metabolism

Proteins

22. Amino acid structure (C1.1.01)

Amino acids have a central carbon atom bonded to an amino group (-NH2), a carboxyl group (-COOH), a hydrogen atom, and a variable R group. The R group determines the properties of the amino acid.

23. Condensation of amino acids (C1.1.02)

Amino acids link through peptide bonds in condensation reactions, forming polypeptides. A water molecule is released in the process.

24. Levels of protein structure (C1.1.03)

o Primary structure: Linear sequence of amino acids.

o Secondary structure: Alpha-helices or beta-pleated sheets formed by hydrogen bonds.

o Tertiary structure: 3D folding due to R-group interactions.

o Quaternary structure: Multiple polypeptide chains combine (e.g., hemoglobin).

25. Globular vs. fibrous proteins (C1.1.04)

o Globular proteins (e.g., enzymes, hormones) are compact and soluble.

o Fibrous proteins (e.g., collagen, keratin) are long, insoluble, and structural.

26. Protein denaturation (C1.1.05)

Proteins lose their structure and function under extreme temperatures or pH changes due to bond disruption.

27. Proteins as hormones and enzymes (C1.1.06)

Hormones like insulin regulate blood glucose. Enzymes catalyse biochemical reactions by lowering activation energy.

Enzymes

28. Active sites and specificity (C1.1.07)

Enzymes have specific active sites that bind to substrates, following the "lock-and-key" or "induced fit" model for specificity.

29. Enzyme-substrate complex (C1.1.08)

When substrates bind to the enzyme's active site, an enzyme-substrate complex forms, facilitating the reaction.

30. Effect of temperature (C1.1.09)

Enzymes have an optimal temperature. Higher temperatures increase activity until denaturation occurs.

31. Effect of pH (C1.1.10)

Each enzyme has an optimal pH range. Deviations can disrupt ionic bonds, altering active site shape and reducing function.

32. Enzyme concentration and activity (C1.1.11)

Increasing enzyme concentration enhances reaction rates until substrate availability becomes limiting.

33. Cofactors and prosthetic groups (C1.1.12)

Some enzymes require non-protein helpers:

o Cofactors: Inorganic ions (e.g., Zn²⁺ for carbonic anhydrase).

o Prosthetic groups: Permanent, non-amino acid groups (e.g., heme in hemoglobin).

34. Inhibitors of enzymes (C1.1.13)

o Competitive inhibitors bind to the active site, blocking substrates.

o Non-competitive inhibitors bind elsewhere, altering enzyme shape.

Metabolism

35. Anabolic and catabolic pathways (C1.1.14)

o Anabolism: Builds complex molecules from simpler ones (e.g., protein synthesis).

o Catabolism: Breaks down molecules to release energy (e.g., glycolysis).

36. Enzyme regulation in pathways (C1.1.15)

Metabolic pathways are regulated by feedback mechanisms where products inhibit earlier steps (e.g., feedback inhibition in ATP production).

37. Energy coupling (C1.1.16)

Cells couple exergonic reactions (release energy) to drive endergonic reactions (require energy) using ATP as the intermediary.

38. ATP as energy currency (C1.1.17)

ATP stores and transfers energy for cellular processes by hydrolysis of its high-energy phosphate bonds.

Unit 2.1: The Cellular Life

2.1.1: Cell Structure

1. Cells as the Basic Structural Unit of Life (A2.2.01)

o Cell Theory:

 All living organisms are made of one or more cells.

 The cell is the basic unit of life.

 All cells arise from pre-existing cells.

o Nature of Science (NOS):

 Predictions based on theories, such as the discovery of new organisms, can be deduced from cell theory.

2. Processes of Life in Unicellular Organisms (A2.2.07)

o Unicellular organisms perform all life functions independently, including:

 Homeostasis: Maintaining internal balance.

 Metabolism: Chemical reactions for energy.

 Nutrition: Intake and processing of nutrients.

 Movement: Locomotion or internal transport.

 Excretion: Removal of waste products.

 Growth: Increase in size or mass.

 Response to Stimuli: Reacting to environmental changes.

 Reproduction: Producing offspring.

3. Structures Common to All Cells (A2.2.04)

o Essential components:

 DNA: Genetic material for heredity.

 Cytoplasm: A watery medium for biochemical reactions.

 Plasma Membrane: A lipid-based barrier controlling entry and exit of substances.

4. Prokaryote Cell Structure (A2.2.05)

o Key features:

 Cell wall: Provides structure and protection.

 Plasma membrane: Regulates material transport.

 Cytoplasm: Contains enzymes and ribosomes.

 Naked DNA: Circular and not enclosed in a nucleus.

 70S ribosomes: Sites of protein synthesis.

o Example: Gram-positive bacteria like Bacillus.

5. Eukaryote Cell Structure (A2.2.06)

o Key features:

 Plasma membrane: Encloses a compartmentalized cytoplasm.

 80S ribosomes: Larger than prokaryotic ribosomes.

 Nucleus: Contains DNA organized into chromosomes with histones, surrounded by a double membrane with pores.

 Organelles: Mitochondria, ER (smooth and rough), Golgi apparatus, lysosomes, vacuoles, etc.

 Cytoskeleton: Composed of microtubules and microfilaments.

6. Organelles and Their Functions (B2.2.01)

o Not organelles: Cell wall, cytoskeleton, and cytoplasm.

o Examples of organelles and advances in their study:

 Ultracentrifugation: Enabled isolation and analysis of organelles.

 Cell Fractionation: Helped in studying specific functions.

7. Advantages of Compartmentalization (B2.2.03)

o Benefits:

 Concentrates enzymes and substrates.

 Separates incompatible reactions.

o Examples:

 Lysosomes: Contain hydrolytic enzymes.

 Phagocytic vacuoles: Digest engulfed material.

8. Differences in Eukaryotic Cells (A2.2.08)

o Variations between animal, fungi, and plant cells:

 Cell walls: Present in plants and fungi, absent in animals.

 Vacuoles: Large central vacuoles in plants, smaller in animals.

 Chloroplasts: Present in plants, absent in animals and fungi.

 Centrioles: Found in animal cells.

 Flagella and cilia: Present in some animals and protists.

9. Atypical Cell Structures in Eukaryotes (A2.2.09)

o Examples:

 Aseptate fungal hyphae: Multinucleated filaments.

 Skeletal muscle fibers: Multinucleated.

 Red blood cells: Lack nuclei.

 Phloem sieve tubes: Lack nuclei for efficient transport.

2.1.2: Microscopy

10. Microscopy Skills (A2.2.02)

o Practical skills:

 Prepare temporary mounts, stain tissues, measure cell sizes, and calculate magnification.

 Create scale bars and take microscopic images.

o NOS: Instruments allow quantitative observation.

11. Developments in Microscopy (A2.2.03)

o Advances include:

 Electron microscopy: High resolution.

 Freeze fracture: Reveals membrane structures.

 Cryo-electron microscopy: Studies molecules at cryogenic temperatures.

 Fluorescent stains: Highlights specific structures.

12. Cell Types and Structures in Micrographs (A2.2.10)

o Identify structures in light and electron micrographs, such as:

 Prokaryotes: Nucleoid, ribosomes, and cell walls.

 Eukaryotes: Nucleus, mitochondria, chloroplasts, ER, etc.

13. Drawing and Annotating Micrographs (A2.2.11)

o Students should create detailed, annotated diagrams of:

 Organelles (nucleus, mitochondria, chloroplasts).

 Cell structures (cell wall, plasma membrane, etc.), including their functions.

2.1.3: Cell Specialization

14. Cell Size as an Aspect of Specialization (B2.3.05)

o Examples:

 Small (red blood cells).

 Large (neurons).

15. Surface Area-to-Volume Ratios (B2.3.06)

o Limitations: Larger volume requires more nutrients, but surface area limits exchange rates.

o NOS: Use models (cubes) to study these relationships.

16. Adaptations for Increased Surface Area (B2.3.07)

o Examples:

 Flattening: Increases surface area for exchange.

 Microvilli: Found in intestinal cells.

17. Differentiation and Specialization (B2.3.01, A2.2.13)

o Differentiation depends on gene expression influenced by gradients in early embryos.

18. Stem Cells (B2.3.02, B2.3.04)

o Properties: Divide endlessly and differentiate.

o Types:

 Totipotent: Form all cell types.

 Pluripotent: Form most cell types.

 Multipotent: Restricted to specific tissues.

19. Stem Cell Niches (B2.3.03)

o Examples:

 Bone marrow: Produces blood cells.

 Hair follicles: Promotes regeneration.