MATSEC SEC Biology: Core Concepts and Exam Application
What this domain tests
MATSEC SEC Biology covers the whole secondary biology course. Structured and extended-response questions ask you to recall facts, interpret data, and link structure to function. Core areas include cell structure and transport, enzymes, nutrition and digestion, gas exchange, transport systems, respiration, photosynthesis, homeostasis, reproduction, inheritance, ecology, and human impact on the environment. Command words matter: state needs a brief fact, describe needs features or a sequence, explain needs a mechanism or reason, and compare needs both similarities and differences.
Core rules and concepts
- Cells: eukaryotic cells have a nucleus and membrane-bound organelles; prokaryotic cells do not. Exchange surfaces are effective when thin, moist, and have a large surface area to volume ratio.
- Transport: diffusion moves particles down a concentration gradient; osmosis is water movement across a partially permeable membrane from higher to lower water potential; active transport uses ATP to move substances against a gradient.
- Enzymes: globular proteins that lower activation energy. They are specific, and high temperature or extreme pH changes their active site shape, denaturing them.
- Energy: photosynthesis stores light energy as chemical energy: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂. Aerobic respiration releases energy: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O.
- Inheritance: alleles are alternative forms of a gene; genotype is the allele combination, phenotype is the visible characteristic. Use a Punnett square for monohybrid crosses.
Worked example
A monohybrid cross is made between two heterozygous tall pea plants, Tt × Tt. Each parent produces T and t gametes. The Punnett square gives TT, Tt, Tt, tt. TT and Tt are tall, while tt is short, so the expected phenotype ratio is 3 tall : 1 short. The probability of a short offspring is 1/4, or 25%. The reasoning is shown by separating gametes, combining them randomly, and interpreting genotype with dominance.
Traps that cost marks
Do not say osmosis moves sugar or salt - it moves water. Do not write that respiration and photosynthesis are opposites without naming energy release versus energy storage. Do not confuse genotype with phenotype. Always give units in calculations and use a table for comparisons.