Cell Biology explores the structure and nature of cells and how they develop. Cells are the basic unit of all forms of life. In this section we explore how structural differences between types of cells enables them to perform specific functions within the organism. These differences in cells are controlled by genes in the nucleus
An organelle that controls the cell and contains the genetic information.
A layer around the cell which helps control substances entering and leaving the cell.
The material within a living cell where the majority of chemical reactions take place.
A cell structure found in green plants that contains chlorophyll for photosynthesis.
A layer lying outside the cell membrane that provides structure to plant, fungi and bacteria cells.
Single cells of bacteria and Archaeans with DNA found in a loop not enclosed in a nucleus.
Cells from eukaryotes that have a cell membrane, cytoplasm, and genetic material enclosed in a nucleus.
When cells or tissues become adapted to carry out their specific function.
Cell division that results in genetically identical diploid cells.
The process whereby water moves from an area of high concentration to an area of low concentration through a semi-permeable membrane.
Unspecialised body cells (found in bone marrow) that can develop into other, specialised cells that the body needs.
The process used by all organisms to release the energy they need from food.
The movement of substances from a dilute solution to a more concentrated solution against a concentration gradient, requiring energy from respiration.
Biological catalysts, usually proteins.
Students will consider information based on the following: The concept of energy emerged in the 19th century. The idea was used to explain the work output of steam engines and then generalised to understand other heat engines. It also became a key tool for understanding chemical reactions and biological systems. Limits to the use of fossil fuels and global warming are critical problems for this century. Physicists and engineers are working hard to identify ways to reduce our energy usage.
Energy associated with an object because of its position or the arrangement of the particles of a system.
Energy an object has because of its movement; kinetic energy is greater for objects with greater mass or higher speed.
The energy needed to raise the temperature of 1kg of a substance by 1⁰C.
Useful output energy transfer divided by the total input energy transfer – may be expressed as a percentage or as a decimal.
A source of energy that can be replaced or reused over a short time.
A source of energy used by humans that will eventually run out.
A fundamental principle of physics: energy cannot be created or destroyed, only stored, transferred or dissipated. This means that the total energy of a closed system is constant.
In physics, any regularly recurring event, such as surf coming in toward a beach, that can be thought of as a disturbance moving through a medium. Waves are characterized by wavelength, frequency, and the speed at which they move.
A wave that oscillates perpendicular to the axis along which the wave travels. Electromagnetic waves are transverse waves, since the electric and magnetic fields oscillate at a right angle to the direction of motion.
Running lengthwise rather than across.
Students will learn about how: The periodic table provides chemists with a structured organisation of the known chemical elements from which they can make sense of their physical and chemical properties. The historical development of the periodic table and models of atomic structure provide good examples of how scientific ideas and explanations develop over time as new evidence emerges. The arrangement of elements in the modern periodic table can be explained in terms of atomic structure which provides evidence for the model of a nuclear atom with electrons in energy levels.
The smallest particle of a chemical element that can exist.
A substance made out of only one type of atom.
Pure substances made up of two or more elements strongly joined together.
The combination of different compounds that are not chemically combined.
Small positive particle found in the nucleus of an atom.
Small negatively charged particle within an atom that orbit the nucleus.
A small particle which does not have a charge and found in the nucleus of an atom.
A charged particle (can be positive or negative).
Atoms with the same number of protons but different numbers of neutrons.
A concise way of expressing information symbolically using mathematical or chemical formulae.
A chemical bond between two ions of opposite charges.
Bonds between atoms where some of the electrons are shared.
The bond between close-packed metal ions due to delocalised electrons.
Electrons which are free to move away through a collection of ions – as in a metal.
A force between different molecules.
The particle model is widely used to predict the behaviour of solids, liquids and gases and this has many applications in everyday life. It helps us to explain a wide range of observations and engineers use these principles when designing vessels to withstand high pressures and temperatures, such as submarines and spacecraft. It also explains why it is difficult to make a good cup of tea high up a mountain! This builds on from understanding of states of matter, then looking at latent heat of fusion and then pressure
A very tiny object such as an atom or molecule, too small to be seen with a microscope.
A way to think about how substances behave in terms of small, moving particles.
The ratio of force to surface area, in N/ m2 , and how it causes stresses in solids.
The basic “building block” of an element which cannot be chemically broken down.
The emission of energy as electromagnetic waves or as moving subatomic particles, especially high-energy particles which cause ionization.
Small positive particle found in the nucleus of an atom.
A small particle which does not have a charge and found in the nucleus of an atom.
A small negatively charged particle within an atom that orbit the nucleus.
Simple particle theory is developed in this unit to include atomic structure and bonding. The arrangement of electrons in atoms can be used to explain what happens when elements react and how atoms join together to form different types of substances.
Substances that have simple molecular, giant ionic and giant covalent structures have very different properties. Ionic, covalent and metallic bonds are strong. However, the forces between molecules are weaker, eg in carbon dioxide and iodine. Metals have many uses, when different metals are combined alloys are formed. Shape memory alloys have a range of uses. There are different types of polymers with different uses. Nanomaterials have new properties because of their very small size.
A chemical bond between two ions of opposite charges.
Bonds between atoms where some of the electrons are shared.
The bond between close-packed metal ions due to delocalised electrons.
Electrons which are free to move away through a collection of ions – as in a metal.
A force between different molecules.
A molecule that can be bonded to other identical molecules to form a polymer.
Very large molecules with atoms linked to other atoms by covalent bonds.
Formed when two metals, or a metal and a non-metal are mixed together to form a substance with different useful properties.
Very small particles on the nanoscale.
The condition a material is found in, can be one of four states: solid, liquid, gas or plasma.
Ionising radiation is hazardous but can be very useful. Although radioactivity was discovered over a century ago, it took many nuclear physicists several decades to understand the structure of atoms, nuclear forces and stability. Early researchers suffered from their exposure to ionising radiation. Rules for radiological protection were first introduced in the 1930s and subsequently
improved. Today radioactive materials are widely used in medicine, industry, agriculture and electrical power generation.
Made up of two protons and two neutrons (the same as a helium nucleus). Positively charged. Stopped by paper or skin. Has a range in air of a few cm. Highly ionising.
The number of protons in an atom (also the same as the number of electrons in the neutral atom but this isn't the definition - if asked what atomic number represents, mention protons!)
Radiation that is around us all of the time. It comes from both natural sources (e.g. rocks, cosmic rays from space) and man - made sources (e.g. fall out from nuclear weapons testing and nuclear accidents)
A fast moving electron given out by the nucleus (a neutron turns in to a proton and gives out an electron). Negatively charged. Stopped by a few mm of aluminium. Can travel about 1 m in air. Less ionising than alpha particles.
The unwanted presence of radioactive atoms either on or in an object (including humans!) These atoms could decay which could cause harm.
Electromagnetic radiation given out by the nucleus. It travels as a wave (is not a particle). Is uncharged. Has an unlimited range in air. Can be reduced by thick lead or concrete.
The time it takes for the number of radioactive nuclei in a sample to halve or the time it takes for the count rate/activity of a sample to fall to half its initial value.
An atom becomes a positive ion if it loses one or more electrons. An atom becomes a negative ion if it gains one or more electrons.
Process of exposing an object to nuclear radiation. The object itself does not become radioactive e.g. sterilising surgical instruments
Isotopes of the same element have the same number of protons but different numbers of neutrons.
The number of protons and neutrons in the nucleus.
Particles found in the nucleus that have no electrical charge (they are neutral).
Positively charged, found at the centre of the atom. Contains protons and neutrons. Most of the mass of an atom is found here.
This early model suggested that an atom was a ball of positive charge with electrons embedded in it (think chocolate chip muffin!)
Positively charged particles found in the nucleus of an atom.
A random process by which an unstable nucleus changes to become more stable. It does this through the emission (giving out) of an alpha particle, a beta particle and/or a gamma ray.
In this section we will learn about the link between the digestive system and the respiratory system. In each case they provide dissolved materials that need to be moved quickly around the body in the blood by the circulatory system. Damage to any of these systems can be debilitating if not fatal. Although there has been huge progress in surgical techniques, especially with regard to coronary heart disease, many interventions would not be necessary if individuals reduced their risks through improved diet and lifestyle. We will also learn how the plant’s transport system is dependent on environmental conditions to ensure that leaf cells are provided with the water and carbon dioxide that they need for photosynthesis.
Bacteria are microscopic living organisms, usually one-celled, that can be found everywhere. They can be dangerous, such as when they cause infection, or beneficial, as in the process of fermentation (such as in wine) and that of decomposition.
A bacterium, virus, or other microorganism that can cause disease.
Any of a group of unicellular, multicellular, or syncytial spore-producing organisms feeding on organic matter, including moulds, yeast, mushrooms, and toadstools.
Spread from one person or organism to another, typically by direct contact.
Increase or cause to increase greatly in number or quantity.
A process in living organisms involving the production of energy, typically with the intake of oxygen and the release of carbon dioxide from the oxidation of complex organic substances.
The process by which green plants and some other organisms use sunlight to synthesize nutrients from carbon dioxide and water. Photosynthesis in plants generally involves the green pigment chlorophyll and generates oxygen as a by-product.
A simple sugar which is an important energy source in living organisms and is a component of many carbohydrates.
A colourless, odourless reactive gas, the chemical element of atomic number 8 and the life-supporting component of the air.
Energy changes are an important part of chemical reactions. The interaction of particles often involves transfers of energy due to the breaking and formation of bonds. Reactions in which energy is released to the surroundings are exothermic reactions, while those that take in thermal energy are endothermic.
Electrolysis uses an electric current to separate substances in solution based on charge. This has many applications in industry.
The minimum amount of energy for particles to collide with in order for a successful reaction to occur.
An endothermic reaction is one that takes in energy from the surroundings so the temperature of the surroundings decreases. In an endothermic reaction, the energy needed to break existing bonds is greater than the energy released from forming new bonds.
An exothermic reaction is one that transfers energy to the surroundings so the temperature of the surroundings increases. In an exothermic reaction, the energy released from forming new bonds is greater than the energy needed to break existing bonds.
Reaction profiles can be used to show the relative energies of reactants and products, the activation energy and the overall energy change of a reaction.
Students will consider information based on the following: The chemistry of carbon compounds is so important that it forms a separate branch of chemistry. A great variety of carbon compounds is possible because carbon atoms can form chains and rings linked by C-C bonds. This branch of chemistry gets its name from the fact that the main sources of organic compounds are living, or once-living materials from plants and animals. These sources include fossil fuels which are a major source of feedstock for the petrochemical industry. Chemists are able to take organic molecules and modify them in many ways to make new and useful materials. The Earth’s atmosphere is dynamic and forever changing. The causes of these changes are sometimes man-made and sometimes part of many natural cycles. In order to operate sustainably, chemists seek to minimise the use of limited resources, use of energy, waste and environmental impact in the manufacture of products.
The envelope of gases surrounding the earth or another planet.
Fuel such as coal, wood, oil, or gas provides energy when burned. Compounds in the body such as glucose are broken down into simpler compounds to provide energy for metabolic processes.
Return (material) to a previous stage in a cyclic process; re-use.
Able to be maintained at a certain rate or level.
In physics, the ability to do work. Objects can have energy by virtue of their motion (kinetic energy), by virtue of their position (potential energy),
The presence in or introduction into the environment of a substance which has harmful or poisonous effects.
A substance which has a molecular structure built up chiefly or completely from a large number of similar units bonded together, e.g. many synthetic organic materials used as plastics and resins.
A covalent bond, also called a molecular bond, is a chemical bond that involves the sharing of electron pairs between atoms.
Cracking is the process whereby complex organic molecules such as kerogens or long chain hydrocarbons are broken down into simpler molecules such as light hydrocarbons,
Waves may be either transverse or longitudinal.
In a transverse wave the oscillations are perpendicular to the direction of energy transfer. The ripples on a water surface are an example of a transverse wave.
In a longitudinal wave the oscillations are parallel to the direction of energy transfer. Longitudinal waves show areas of compression and rarefaction. Sound waves travelling through air are longitudinal.
The maximum displacement of a wave from its undisturbed (equilibrium) position.
The angle between the incident ray and normal
The angle between the reflected ray and normal.
An object will appear black if it absorbs all wavelengths of radiation incident on it.
Reflection from a rough surface that results in scattering.
Transverse waves that transfer energy from the source of the waves, to an absorber. They form a continuous spectrum of different frequencies and all travel at the same speed in a vacuum.
The number of waves passing a given point in a second. It is the inverse of the wave’s period.
The unit of frequency.
Humans can hear sounds in the frequency range of 20Hz to 20kHz.
A type of radiation that all objects emit and absorb. The hotter an object is, the greater the infrared radiation it emits in a given time.
Radiation that can cause the mutation of genes and cause cancer. X-rays and gamma rays are both forms of ionising radiation.
Used for satellite communications and for cooking food.
The normal is an imaginary reference line that is constructed perpendicular to a boundary at the point that the wave intercepts it.
Used for television and radio signals. They can be produced by oscillations in electrical circuits.
Reflection from a smooth surface, in a single direction.
Waves with oscillations that are perpendicular to the direction of travel/energy transfer.
Used in energy efficient lamps and for sun tanning.
The only type of electromagnetic radiation that our eyes can detect. It is used for fibre optic communications.
The speed at which energy is transferred through the medium. It is equal to the product of the wave’s wavelength and frequency.
The distance from a point on one wave to the same point on the adjacent wave (ie. peak to peak or trough to trough).
An object will appear white if it emits all wavelengths equally.
Up to the end year test will include revision of topics so far. Students will apply key scientific approaches to different investigations that include mathematical skills. After the end of year students will be asked to consolidate areas of weakness identified in the exam.