Biology Class Quiz

Cell Biology

Eukaryotes vs. Prokaryotes: Eukaryotic cells are complex, containing a nucleus and organelles, while prokaryotic cells are simpler, lacking a nucleus and organelles; DNA is free in the cytoplasm. Prokaryotes have plasmids, a cell wall, and smaller ribosomes.
Animal vs. Plant Cells: Common structures include nucleus, cytoplasm, cell membrane, mitochondria, and ribosomes. Plant cells uniquely have a cell wall, chloroplasts, and a large permanent vacuole.
Cell Specialization: Cells adapt specific features to perform a particular function. Examples include: sperm cells (tail for swimming, mitochondria for energy), nerve cells (long axon for signal transmission), and root hair cells (large surface area for water and mineral absorption).
Cell Differentiation: Cells develop specific features to perform their function, primarily in early animal development and throughout plant life.
Microscopy: Magnification is the enlargement of an image relative to the object (Magnification = Image size ÷ Real size). Light microscopes have lower resolution and magnification, allowing observation of living specimens, while electron microscopes offer higher resolution and magnification but can only view non-living samples.
Cell Division: Mitosis is a process of cell division responsible for growth, repair, and asexual reproduction. The cell cycle includes DNA replication, mitosis (prophase, metaphase, anaphase, telophase), and cytokinesis (cytoplasm division).
Stem Cells: Undifferentiated cells that can divide and differentiate into specialized cells. Embryonic stem cells are pluripotent (can differentiate into any cell type), while adult stem cells are multipotent (limited to certain cell types).
Cell Transport:
Diffusion: Movement of particles from a high to low concentration (e.g., oxygen diffuses into cells).
Osmosis: Movement of water from a dilute solution to a concentrated solution through a semi-permeable membrane (e.g., water into plant roots).
Active Transport: Movement of substances against a concentration gradient using energy (e.g., mineral ions absorbed by root hair cells).

Bioenergetics

Photosynthesis: Plants convert light energy into chemical energy stored in glucose (6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂). This occurs in chloroplasts containing chlorophyll.
Photosynthesis Factors: Photosynthesis rate depends on light intensity, carbon dioxide concentration, and temperature. A limiting factor limits the rate of the process, like the availability of light, CO₂ or temperature. Enzymes speed up reactions, but denature at high temperatures.
Photosynthesis Glucose Uses: Glucose made in photosynthesis is used for respiration, stored as starch, converted into cellulose (cell walls), combined with nitrates (proteins) and/or converted to fats/oils.
Respiration: The process of breaking down glucose to release energy. Aerobic respiration (C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + energy) requires oxygen, while anaerobic respiration (different products depending on the organism) does not.
Exercise Response: Exercise leads to increased heart rate for faster oxygen transport; increased breathing for more oxygen; anaerobic respiration, lactic acid buildup, and oxygen debt if oxygen demand exceeds supply.
Metabolism: The sum of all chemical reactions in an organism, including the conversion of glucose, formation of lipids, and breakdown of excess proteins.

Atomic Structure

Atoms, Elements, and Compounds: Atoms are the smallest unit of an element, retaining chemical properties. Elements are pure substances of only one atom type. Compounds are formed from multiple elements chemically combined in fixed proportions.
Mixtures: Mixtures are combinations of substances without chemical bonds, separated by physical methods (e.g., filtration, distillation, crystallisation, chromatography).
Atomic Theory Development: Key discoveries include Dalton's indivisible spheres, Thomson's “plum pudding” model (electrons within a positive sphere), Rutherford's nucleus, and Bohr's electron shells.
Subatomic Particle Charges: Protons (+1), neutrons (0), and electrons (-1) carry these charges.
Atom Size and Mass: Atoms are approximately 0.1 nanometers in size and subatomic particles vary in mass; protons (1), neutrons (1), electrons (approximately 1/2000).
Relative Atomic Mass: Relative atomic mass (Ar) is the weighted average mass of isotopes of an element compared to 1/12th the mass of a carbon-12 atom.

Chemical Changes

Acids with Metals: Acids react with metals to produce a salt and hydrogen gas (Acid + Metal → Salt + Hydrogen). Salts formed from different acids have different names (e.g., chlorides, sulfates, nitrates).
Neutralization: The reaction between an acid and a base to produce a salt and water (Acid + Base → Salt + Water).
Soluble Salts: Soluble salts are made by reacting an acid with a suitable base, carbonate, or metal, then filtering and evaporating the solution.
pH Scale: The pH scale measures the concentration of hydrogen ions (H⁺); acids have pH below 7, neutral solutions are 7, and alkalis have a pH above 7.
Strong and Weak Acids: Strong acids fully ionise in water (hydrochloric), weak acids only partially ionise (e.g., ethanoic).
Electrolysis: Using electricity to break down a substance; electrolytes are electrically conductive liquids containing ions.
Electrolysis of Molten Compounds: Positive ions move to the cathode (reduction) and negative ions to the anode (oxidation).
Electrolysis for Metal Extraction: More reactive metals like aluminum are extracted from ores via electrolysis of molten compounds.

Electricity

Circuit Symbols: Symbols represent circuit components in diagrams (e.g., cell, resistor, lamp).
Electric Charge and Current: Electric charge (measured in coulombs (C)) causes force in an electric field. Current (measured in amperes (A)) is the flow of electric charge (Current = Charge ÷ Time).
Current, Resistance, and Potential Difference: Resistance (ohms (Ω)) opposes current flow, potential difference (volts (V)) is energy transferred per unit charge. Ohm's Law: Voltage = Current x Resistance.
Resistors: Fixed resistors have constant resistance, variable resistors can be adjusted (e.g., dimmer switch). Thermistors' resistance decreases with temperature; LDR's decrease with light intensity.
Series vs. Parallel Circuits: Series circuits have the same current throughout, shared potential difference; parallel circuits have split current, same potential difference across branches.
Domestic Uses and Safety: Plugs contain live (brown), neutral (blue), and earth (green/yellow) wires; circuit breakers prevent overheating/fires due to high current.
Mains Electricity: UK mains electricity is 230V, 50Hz.
Power: Power (watts (W)) is calculated as Voltage x Current.
Energy Transfer: Energy transferred (joules (J)) = Power x Time.
National Grid: Distributes electricity; step-up and step-down transformers regulate voltage to reduce transmission losses.