Eukaryotic vs Prokaryotic Cells

Biology Paper 1

• Biology studies life from cellular units to complex organisms.

Eukaryotes and Prokaryotes

• Eukaryotes have a true nucleus where DNA is enclosed by a nuclear membrane.
• Eukaryotes possess specialized organelles like mitochondria, endoplasmic reticulum, and chloroplasts.
• Prokaryotes lack a nucleus; genetic material resides in a nucleoid region.
• Prokaryotes have simpler internal structure without membrane-bound organelles.
• Eukaryotes are generally larger and more complex than prokaryotes.
• Prokaryotes are typically unicellular like bacteria and archaea, possessing circular DNA.
• Eukaryotes can be unicellular or multicellular.
• Eukaryotes likely evolved from prokaryotic ancestors through endosymbiosis, such as the acquisition of mitochondria.
• Escherichia coli is a prokaryote, whereas human fibroblast cells are eukaryotes.

Animal and Plant Cells

• Animal cells have a flexible plasma membrane and organelles like lysosomes and centrosomes.
• Animal cells do not have a cell wall but possess a complex cytoskeleton.
• Plant cells have a rigid cell wall (cellulose), central vacuoles, and chloroplasts for photosynthesis.
• Only plant cells have chloroplasts.
• Plant cells have a rigid cell wall for shape/support, unlike animal cells that rely on the extracellular matrix and cytoskeleton.
• Simplified Plant Cell Diagram: [Cell Wall]-[Plasma Membrane]-[Chloroplasts, Vacuole, Nucleus, Mitochondria]
• Simplified Animal Cell Diagram: [Plasma Membrane]-[Nucleus, Mitochondria, Ribosomes, Lysosomes]
• Leaf cells use chloroplasts to convert sunlight to sugar; animal (muscle) cells use mitochondria for energy during contraction.

Specialized Cells

• Cells differentiate to perform specific tasks efficiently.
• Red Blood Cells (Erythrocytes) lack nuclei and most organelles to maximize space for hemoglobin to transport oxygen.
• Nerve Cells (Neurons) have dendrites/axons enabling electrical signal transmission over long distances.
• Root Hair Cells extend from plant roots, increasing the surface area for water and mineral uptake.

Mitosis

• Mitosis is a cellular reproduction mechanism that produces daughter cells that are genetic copies of the parent cell.
• Prophase: Chromatin condenses into visible chromosomes; the nuclear envelope disintegrates.
• Metaphase: Chromosomes align along the metaphase plate.
• Anaphase: Sister chromatids separate and move to opposite poles.
• Telophase: Nuclear membranes reform around the two sets of chromosomes.
• Understanding the sequence and function of phases is key for mitosis.
• Skin cells use mitosis to replace cells shed from the surface.

Stem Cells and Therapeutic Cloning

• Stem cells are undifferentiated with the ability to form various cell types.
• Therapeutic Cloning: Creates cells genetically identical to a donor with potential in medicine for tissue/organ regeneration.
• Applications include repairing nerve damage or heart tissue after injury and treating diseases like Parkinson's or spinal cord injuries.
• Research focuses on generating neurons from embryonic stem cells for patients with neurodegenerative conditions.

Membrane Transport: Osmosis, Diffusion, and Active Transport

• Membrane transport is essential for maintaining homeostasis in cells.
• Diffusion: Passive movement of molecules from high to low concentration.
• Diffusion Rate Equation: Rate ∝ 1/(Distance)².
• Osmosis: A special case of diffusion, where water moves across a semi-permeable membrane.
• Active Transport: Molecules move against a concentration gradient using energy (ATP).
• Plant roots absorb minerals through active transport.

The Digestive System

• The digestive system breaks down food into small molecules for bloodstream absorption.
• Mouth: Mechanical breakdown starts here.
• Stomach: Hydrochloric acid and pepsin secreted for protein digestion.
• Small Intestine: enzymatic digestion happens here; enzymes like amylase/lipase break down carbohydrates and fats.
• Enzyme Activity Equation (Simplified): Rate of Reaction ∝ 1/Time Taken (T)
• Absorption of simple sugars in the small intestine provides quick energy to cells.

Heart and Blood Vessels

• The circulatory system transports oxygen, nutrients, and waste products.

• Heart: A muscular pump is divided into chambers.

• Blood Vessels: Arteries (carry blood away), Veins (carry blood to heart), and Capillaries (exchange sites).

• Flow Equation: Q = v × A

  • (Q) is flow rate.
  • (v) is the velocity of blood.
  • (A) is the cross-sectional area of the blood vessel.

• Blood flow dynamics are critical in analyzing conditions like hypertension or coronary artery disease.

Photosynthesis and Respiration

• Photosynthesis and respiration are complementary processes that manage energy flow in living organisms.
• Photosynthesis Equation: 6CO₂ + 6H₂O + light energy → C₆H₁₂O₆ + 6O₂
• Chloroplasts in plant cells convert light energy into chemical energy (glucose).
• Cellular Respiration Equation: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + energy (ATP)
• Cellular respiration occurs in mitochondria of eukaryotic cells, breaking down glucose to produce ATP (energy).
• During the day, photosynthesis produces sugars, and respiration uses those sugars for cellular activities.

Chemistry Paper 1

• Chemistry explores matter's composition, structure, properties, and changes, from atomic theory to chemical bonds/reactions.

Atomic Structure and Isotopes

• Atoms are composed of subatomic particles.
• Protons: Positively charged, located in the nucleus.
• Neutrons: Neutral charge, located in the nucleus.
• Electrons: Negatively charged, orbit the nucleus.
• Isotopes are atoms of the same element with different numbers of neutrons.
• Relative Atomic Mass Calculation: Relative Atomic Mass = [Σ (Isotope Mass × Abundance)] / 100; For example, Chlorine has 2 main isotopes (Cl-35 and Cl-37) with an average atomic mass of ~35.5.

Development of the Periodic Table

• The periodic table organizes based on atomic numbers and properties.
• Plum Pudding Model (Thomson): Electrons are embedded in a positive "soup."
• Rutherford Model: A dense nucleus with electrons orbiting.
• Bohr Model: Electrons are in specific energy levels.
• Modern periodic tables group elements by shared properties (metals, nonmetals, metalloids).
• Noble gases (Group 0) are inert due to their full valence electron shells.

Bonding: Ionic, Covalent, and Metallic

• Chemical bonds hold atoms together in compounds.
• Ionic Bonding: Electrons transfer from metals (e.g., sodium) to nonmetals (e.g., chlorine).
• Ionic bonding results in oppositely charged ions (Na+ and Cl-) attracting.
• Example: Sodium chloride (NaCl)
• Covalent Bonding: Atoms share electrons for stability.
  • Nonpolar Covalent: Equal sharing (e.g., O₂).
  • Polar Covalent: Unequal sharing (e.g., H₂O).
• Example: Water (H₂O), oxygen exerts a stronger pull over electrons.
• Metallic Bonding: Delocalized electrons move freely among metal ions.
• Metallic bonding has high electrical conductivity and malleability.
• Copper (Cu) is used in electrical wiring due to metallic bonding.

Chemical Reactions and Energetics

• Chemical reactions rearrange atoms where energy is absorbed or released.
• Endothermic: Absorbs energy (ΔH > 0); for example, melting ice absorbs heat.
• Exothermic: Releases energy (ΔH < 0); for example, combustion of methane (CH₄ + 2O₂ → CO₂ + 2H₂O, ΔH ≈ -891 kJ/mol).

Reaction Stoichiometry

• Balancing Equations is essential for mass conservation and mole-to-mole relationships.
• Example: 2H₂ + O₂ → 2H₂O
• Use the mole concept along with Avogadro's number (6.022 × 10²³) to correlate atoms to moles.

Laboratory Investigations and Practical Work

• Practical experiments reinforce theoretical concepts.
• Measuring Temperature Changes: Used in reactions to determine enthalpy changes.
• Electrolysis: Passing an electric current through a solution, studies ionic movement.
• Purification Techniques: Recrystallization can obtain pure substances.
• Rate of substance dissolving indicates reaction kinetics and solubility principles.

Physics Paper 1

• Physics studies the forces and energy influencing matter and motion, circuit dynamics, thermal properties, and atomic models.

Energy: Kinetic, Potential, and Beyond

• Energy is the capacity to do work, existing in multiple forms and stored in various ways.

• Kinetic Energy: Eₖ = (1/2)mv²

  • m is mass.
  • v is velocity.

• Example: A 10 kg object moving at 3 m/s has Eₖ = (1/2) * 10 * 3² = 45 J.

• Gravitational Potential Energy: Eₚ = mgh

  • g is the acceleration due to gravity
  • h is the height.

• Example: A 5 kg mass raised 4 m has Eₚ = 5 * 9.8 * 4 ≈ 196 J.

• Energy is never created or destroyed, only transformed.

• A pendulum transforms potential energy (highest point) into kinetic energy (lowest point).

Electricity and Circuitry

• Electricity is the flow of electric charge, driven by differences in voltage (potential difference).
• Ohm’s Law: V = I × R
  • V is voltage.
  • I is current.
  • R is resistance.
• For a circuit with 2 A and 10 Ω: V = 2 * 10 = 20 V.
• In Series Circuits: Current is the same, and voltage divides.
• In Parallel Circuits: Voltage is the same, and current divides.
• Resistors in series: Rtotal = R1 + R2 + ...
• Resistors in parallel: 1/Rtotal = 1/R1 + 1/R2 + ...
• National Grid: An extensive network combining series and parallel elements to distribute electricity efficiently.

Thermal Energy: Specific Heat Capacity and Latent Heat

• Understanding heat involves knowing how substances store and transfer energy.

• Specific Heat Capacity: E = mcΔT

  • m is mass.
  • c is the specific heat capacity.
  • ΔT is the change in temperature.

• For example, to raise 2 kg of water (c ≈ 4200 J/kg°C) by 10°C, the energy required is E = 2 * 4200 * 10 = 84,000 J.

• Latent Heat: Energy absorbed/released during a phase change at constant temperature.

• Latent Heat Equation: E = mL (L is the latent heat of fusion, vaporization, etc.).

• Melting 1 kg of ice needs ~334,000 J (using the latent heat of fusion for water).

Atomic Structure and Nuclear Radiation

• Physics converges with chemistry analyzing the structure of atoms and radiation.
• Bohr Model: Electrons orbit the nucleus in fixed paths with defined energy levels.
• Quantum View: Electron probability clouds are described rather than fixed orbits.
• Nuclear Radiation Types:
  • Alpha Particles: Helium nuclei, low penetration.
  • Beta Particles: High-speed electrons; moderate penetration.
  • Gamma Rays: High-energy electromagnetic waves; high penetration.
• Understanding radiation impacts nuclear physics and medical applications.
• Radioactive decay of Carbon-14 is used in radiocarbon dating.

Laboratory Investigations in Physics

• Hands-on experiments solidify understanding.
• Investigating Heat Transfer uses calorimetry to measure specific heat capacities.
• Measuring Resistance uses multimeters and varying wire lengths to verify Ohm's law.
• Circuit Building: Series/parallel circuits explore voltage/current division.
• Heating a substance measures its temperature change over time to understand thermal capacity.