General Science Study Guides

Photosynthesis is the endothermic reaction inside plant and algal chloroplasts that converts light energy into chemical energy stored in glucose. Understanding how the light-dependent reactions on the thylakoid membranes supply ATP and NADPH to the light-independent Calvin cycle in the stroma, alongside how light intensity, CO₂, and temperature act as limiting factors, covers the core exam questions on this topic.

Aerobic cellular respiration breaks down glucose through four linked stages: glycolysis in the cytoplasm, followed by the link reaction, the Krebs cycle, and oxidative phosphorylation via the electron transport chain inside the mitochondria. Learning where each stage occurs, what enters and leaves, and how reduced NAD and FAD drive ATP synthesis makes every exam question on respiration straightforward.

Mitosis and meiosis are the two types of nuclear division in eukaryotic cells. Mitosis involves 1 division that produces 2 genetically identical diploid daughter cells for growth and tissue repair, whereas meiosis involves 2 divisions (meiosis I and II) that produce 4 genetically distinct haploid gametes for sexual reproduction.

Published in 1687, Newton's three laws of motion form the foundation of classical mechanics across GCSE and A-Level Physics. They relate the forces acting on a body to its state of motion: equilibrium when resultant force is zero (First Law), acceleration proportional to resultant force via F = ma (Second Law), and equal and opposite interaction pairs between two bodies (Third Law).

The supply and demand model explains how prices and quantities are determined in a competitive market. Demand shows the quantity buyers are willing and able to purchase at each price, supply shows the quantity firms are willing and able to offer, and the intersection of the two curves establishes the market equilibrium price and quantity.

The global hydrological (water) cycle is a closed system in which water continuously circulates between the oceans, atmosphere, and land without any water entering or leaving the planet. Solar energy drives evaporation and transpiration into the atmosphere, while condensation and gravity return water to the surface as precipitation, infiltration, and river runoff.