BMA Long Course key terms

The process by which green plants use sunlight, water and carbon dioxide to make glucose and release oxygen. It happens mainly in leaves, inside structures called chloroplasts, and it is the base of most food chains.

The green pigment inside chloroplasts that absorbs light energy for photosynthesis. It captures mainly red and blue light and reflects green light, which is why most leaves look green to us.

A small oval structure found in plant cells that contains chlorophyll and carries out photosynthesis. It has its own DNA and is thought to have originated from free-living bacteria taken inside a host cell long ago.

The chemical breakdown of glucose inside cells to release energy, carbon dioxide and water. Aerobic respiration needs oxygen and yields far more energy than anaerobic respiration, which occurs without oxygen and produces substances such as lactic acid or ethanol.

A protein that speeds up a specific chemical reaction in living things without being used up. Each enzyme has an active site shaped to fit its substrate, and its activity depends strongly on temperature and pH.

The movement of water molecules through a partially permeable membrane from a region of higher water concentration to one of lower water concentration. It explains water uptake by plant roots and the wilting of plants in salty soil.

The net movement of particles from an area of higher concentration to an area of lower concentration, driven by random motion. It needs no energy input and explains gas exchange in the lungs and the spread of smells through air.

Cell division that produces two genetically identical daughter cells, each with the same chromosome number as the parent. It is used for growth, repair and asexual reproduction, and it differs from meiosis, which makes sex cells.

A special type of cell division that halves the chromosome number and produces four genetically different gametes. Crossing over and independent assortment during meiosis create variation, which is important for evolution and inheritance.

A thread-like structure of DNA and protein found in the nucleus, carrying genes in a fixed order. Humans have 46 chromosomes in body cells, arranged as 23 pairs, with one chromosome of each pair inherited from each parent.

A short section of DNA that codes for a particular protein or trait. Genes are passed from parents to offspring, and different versions of the same gene, called alleles, can produce different characteristics such as blood group.

Terms describing how alleles interact. A dominant allele shows its effect even when only one copy is present, while a recessive allele shows its effect only when two copies are present. This explains ratios in simple genetic crosses.

Genotype is the combination of alleles an organism carries for a trait, while phenotype is the observable characteristic that results. Two organisms can share a phenotype yet have different genotypes, for example a pure tall pea plant and a hybrid tall one.

The acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass, written as F = ma. It links force, mass and acceleration and is the basis for solving most motion problems.

The tendency of an object to resist any change in its state of rest or uniform motion. It depends only on mass, so a heavier object is harder to start moving and harder to stop once moving.

The product of an object's mass and its velocity, measured in kilogram metres per second. Momentum is a vector quantity, and in a closed system the total momentum before and after a collision stays the same.

Work is done when a force moves an object through a distance, measured in joules. Power is the rate of doing work, measured in watts, so a machine that does the same work in less time has greater power.

The principle that energy cannot be created or destroyed but only changed from one form to another. In a falling object, potential energy converts to kinetic energy, though some energy may be lost as heat through friction.

For a conductor at constant temperature, the current through it is directly proportional to the potential difference across it, written as V = IR. Resistance is measured in ohms and depends on the material's length, thickness and temperature.

The rate of flow of electric charge past a point in a circuit, measured in amperes. Conventional current is taken as flowing from the positive terminal to the negative terminal, opposite to the actual flow of electrons.

In a series circuit components are connected in one loop, so the same current flows through each and voltages add. In a parallel circuit components sit on separate branches, so voltage is shared equally while currents add.

The bending of light as it passes from one transparent medium into another of different optical density, caused by a change in speed. It explains why a straw looks bent in water and how lenses form images.

The bouncing back of light when it strikes a surface. For a plane mirror the angle of incidence equals the angle of reflection, and the image formed is virtual, upright and the same size as the object.

A curved piece of transparent material that refracts light to form an image. A convex lens converges light and can form real images, while a concave lens diverges light and forms only virtual, diminished images.

The amount of substance containing exactly 6.022 x 10^23 particles, known as Avogadro's number. One mole of any substance has a mass in grams equal to its relative atomic or molecular mass.

The mass of one mole of a substance, expressed in grams per mole. It is found by adding the relative atomic masses of all atoms in the formula, so the molar mass of water is about 18 grams per mole.

The number of particles in one mole of a substance, approximately 6.022 x 10^23. It allows chemists to convert between the mass of a sample and the actual number of atoms or molecules it contains.

The simplest whole-number ratio of atoms of each element in a compound. For example, the empirical formula of glucose is CH2O, while its molecular formula, C6H12O6, shows the actual number of atoms.

An acid releases hydrogen ions in water and turns blue litmus red, while a base accepts hydrogen ions or releases hydroxide ions and turns red litmus blue. They neutralise each other to form a salt and water.

A scale from 0 to 14 measuring the concentration of hydrogen ions in a solution. Values below 7 are acidic, 7 is neutral, and above 7 is alkaline; each unit represents a tenfold change in acidity.

The reaction between an acid and a base that produces a salt and water. It is used in everyday life, for example treating indigestion with antacids or adding lime to reduce the acidity of soil.

A chart arranging elements in order of increasing atomic number so that elements with similar properties fall into the same group. Metals sit on the left, non-metals on the right, and group number relates to outer electrons.

The number of protons in the nucleus of an atom, which identifies the element. In a neutral atom it also equals the number of electrons, and it determines the atom's position in the periodic table.

The combining power of an element, equal to the number of electrons it gains, loses or shares to complete its outer shell. Valency is used to work out the formula of a compound, such as NaCl or H2O.

An equation that is true for all values of its variables, such as (a + b)^2 = a^2 + 2ab + b^2. Identities are used to expand brackets, factorise expressions and simplify calculations quickly.

An equation of the form ax^2 + bx + c = 0 where a is not zero. Its roots can be found by factorisation, completing the square or the quadratic formula, and the discriminant b^2 - 4ac tells how many real roots exist.

Writing an expression as a product of simpler expressions, for example x^2 - 9 = (x - 3)(x + 3). It is a key tool for solving equations, simplifying fractions and finding the roots of polynomials.

A ratio of two sides of a right-angled triangle, such as sine, cosine or tangent. For an angle, sine is opposite over hypotenuse, cosine is adjacent over hypotenuse, and tangent is opposite over adjacent.

In a right-angled triangle, the square of the hypotenuse equals the sum of the squares of the other two sides, written a^2 + b^2 = c^2. It is used to find unknown lengths and distances between points.