Master Cambridge A Level Biology — all the way to A*

Covers the structure, properties, and biological roles of all major macromolecules tested on the 9700 syllabus.

Builds understanding of cell ultrastructure, membrane biology, and the mechanisms cells use to move substances.

Explores enzyme kinetics and the two major metabolic pathways that underpin all cellular energy transformations.

Covers DNA replication, gene expression, inheritance patterns, and the biotechnological applications examined at A2.

Covers the key animal and plant physiological systems assessed in both AS and A2 components of the 9700 syllabus.

Covers population ecology, biodiversity, natural selection, and classification as tested in the A2 syllabus.

Builds the experimental, statistical, and command-word skills needed to maximise marks across all assessed components.

All organisms are composed of cells. Knowledge of the structure and function of cells underpins much of
biology. The fundamental differences between eukaryotic and prokaryotic cells are explored and provide
useful biological background for the topic on Infectious diseases (Topic 10). Viruses are introduced as non
cellular structures, which gives candidates the opportunity to consider whether cells are the basic unit of life.
The use of light microscopes is a fundamental skill that is developed in this topic and applied throughout
several other topics of the syllabus.

This topic introduces carbohydrates, lipids and proteins: organic molecules that are important in cells. Nucleic
acids, another class of biological molecule, are covered in Topic 6. All of these molecules are based on the
versatile element carbon. This topic explains how carbohydrates, lipids and proteins, which have a great
diversity of function in organisms, are assembled from smaller organic molecules such as glucose, amino
acids, glycerol and fatty acids.
The emphasis in this topic is on the relationship between molecular structures and their functions. Some
of these ideas are continued in other topics, for example, the functions of haemoglobin in gas transport in
Transport in mammals (Topic 8), phospholipids in membranes in Cell membranes and transport (Topic 4) and
antibodies in Immunity (Topic 11).
Life as we know it would not be possible without water. Understanding the properties of this extraordinary
molecule is an essential part of any study of biological molecules. Some of the roles of water are in this topic,
others are in Topics 4, 7, 8, 12, 13 and 14.

Enzymes are essential for life to exist. The mode of action of enzymes and the factors that affect their activity
are explored in this topic. Prior knowledge for this topic is an understanding that an enzyme is a biological
catalyst that increases the rate of a reaction and remains unchanged when the reaction is complete.
There are many opportunities in this topic for candidates to gain experience of carrying out practical
investigations and analysing, interpreting and evaluating their results.

The fluid mosaic model, introduced in 1972, describes the way in which biological molecules are arranged to
form cell membranes. The model continues to be modified as understanding improves of the ways in which
substances cross membranes, how cells interact and how cells respond to signals. The model also provides
the basis for our understanding of passive and active movement of molecules and ions between cells and
their surroundings, cell-to-cell interactions and long-distance cell signalling.
Investigating the effects of different factors on diffusion, osmosis and membrane permeability involves an
understanding of the properties of phospholipids and proteins covered in Biological molecules (Topic 2).

When body cells reach a certain size they divide into two cells. Nuclear division occurs first, followed by
division of the cytoplasm. The mitotic cell cycle of eukaryotes involves DNA replication followed by nuclear
division. This ensures the genetic uniformity of all daughter cells.

Nucleic acids have roles in the storage and retrieval of genetic information and in the use of this information
to synthesise polypeptides. DNA is the molecule of heredity and is an extremely stable molecule that cells
replicate with great accuracy. The genetic code explains how the sequence of nucleotides in DNA and
messenger RNA (mRNA) determines the sequence of amino acids that make up a polypeptide. In eukaryotes
this involves the processes of transcription in the nucleus to produce mRNA, followed by translation in the
cytoplasm to produce polypeptides.

Flowering plants do not have compact bodies like those of many animals. Leaves and extensive root systems
spread out to obtain the light energy, carbon dioxide, mineral ions and water that plants gain from their
environment to make organic molecules, such as sugars and amino acids. Transport systems in plants move
substances from where they are absorbed or produced to where they are stored or used.

As animals become larger, more complex and more active, transport systems become essential to supply
nutrients to, and remove waste from, individual cells. Mammals are far more active than plants and require
much greater supplies of oxygen. This is transported by haemoglobin inside red blood cells.

The gas exchange system is responsible for the uptake of oxygen into the blood and the excretion of carbon
dioxide. An understanding of this system shows how cells, tissues and organs function together to exchange
these gases between the blood and the environment.

The infectious diseases studied in this topic are caused by pathogens that are transmitted from one human
host to another. Some, like Plasmodium that causes malaria, are transmitted by vectors, but there are many
other methods of transmission, such as through water and food or during sexual activity. An understanding
of the biology of the pathogen and its mode of transmission is essential if the disease is to be controlled and
ultimately prevented.

An understanding of the immune system shows how cells and molecules function together to protect the
body against infectious diseases and how, after an initial infection, the body is protected from subsequent
infections by the same pathogen. Phagocytosis is an immediate non-specific part of the immune system,
while the actions of lymphocytes provide effective defence against specific pathogens.

Energy is a fundamental concept in biology. All living organisms require a source of cellular energy to drive
their various activities. All organisms respire by using enzyme-catalysed reactions to release energy from
energy-rich molecules such as glucose and fatty acids and transfer that energy to ATP. ATP is the universal
energy currency of cells. In eukaryotes, aerobic respiration occurs in mitochondria.
The practical activities in this topic give opportunities for candidates to plan investigations, analyse and
interpret data and evaluate experimental procedures and the quality of the data collected.

Photosynthesis is the energy transfer process that is the basis of nearly all life on Earth. It provides energy
directly or indirectly to all the organisms in most food chains. In eukaryotes, the process occurs within
chloroplasts. Candidates should apply their knowledge of plant cells from Cell structure (Topic 1) and leaf
structure from Transport in plants (Topic 7) while studying photosynthesis. Various environmental factors
influence the rate at which photosynthesis occurs.
The practical activities in this topic give opportunities for candidates to plan investigations, analyse and
interpret data and evaluate experimental procedures and the quality of the data that they collect.

Cells function most efficiently if they are kept in near optimum conditions. Cells in multicellular animals are
surrounded by tissue fluid. The composition of tissue fluid is kept constant by exchanges with the blood as
discussed in the topic on Transport in mammals (Topic 8). In mammals, core temperature, blood glucose
concentration and blood water potential are maintained within narrow limits to ensure the efficient operation
of cells. Prior knowledge for this topic includes an understanding that waste products are excreted from the
body and an outline of the structure and function of the nervous and endocrine systems. In plants, guard
cells respond to fluctuations in environmental conditions and open and close stomata as appropriate for
photosynthesis and conserving water.

All the activities of multicellular organisms require coordinating, some very rapidly and some more slowly. The
nervous system and the endocrine system provide coordination in mammals. Coordination systems also exist
in plants.

Genetic information is transmitted from generation to generation to maintain the continuity of life. In sexual
reproduction, meiosis introduces genetic variation so that offspring resemble their parents but are not
identical to them. Genetic crosses reveal how some features are inherited. The phenotype of organisms is
determined partly by the genes that they have inherited and partly by the effect of the environment. Genes
determine how organisms develop; gene control in bacteria gives us a glimpse of this process in action.

Selection and evolution

Classification systems attempt to order all the organisms that exist on Earth according to their characteristics
and evolutionary relationships with one another. There are opportunities in this topic for candidates to observe
different species in their locality and assess species distribution and abundance. Fieldwork is an important
part of a biological education because it provides opportunities to appreciate and analyse biodiversity, and to
study the interactions between organisms and their environment. The biodiversity of the Earth is threatened
by human activities and climate change. Conserving biodiversity is a difficult task; individuals, local groups,
national and international organisations can all make significant contributions. Candidates should appreciate
the threats to biodiversity and consider some of the steps taken in conservation, both locally and globally.

The discovery in the early 1950s of the structure of DNA by Watson and Crick, supported by the work of
Franklin, Wilkins and Chargaff, and discoveries since, have led to many applications of genetic technology in
areas of medicine, agriculture and forensic science. This topic relies heavily on prior knowledge of DNA and
RNA structure and protein synthesis from the topic on Nucleic acids and protein synthesis (Topic 6).
Candidates will benefit from carrying out practical work using electrophoresis, either with DNA or specially
prepared dyes used to represent DNA.