Biology Year 12

Biological Molecules

You will get to grips with the very basic molecules of life. Each quiz takes you through the structure of each monomer, the structural differences between them, and how they join together to become biological polymers.

We start with Carbohydrate Structure, looking first at the Monosaccharides;Alpha and Beta Glucose, and how through condensation reactions, they can be joined together by glycosidic bonds to make disaccharides. From here we test your knowledge of the structural differences, and resulting differences in the properties of the polysaccharides : Amylose, Amylo-pectin, Cellulose and Glycogen.

Lipid structure, and the structural differences between saturated and unsaturated fatty acids is tested here along with Ester linkages ( or bonds).

Protein structure again starts with the monomers; Amino Acids. The quiz tests your knowledge of the carboxyl group and the amino group, and the differing R groups. It tests your ability to identify a peptide bond, and how the order of amino acids dictates the ensuing secondary, tertiary and quaternary structures of proteins.There are two quizzes on Enzymes, and what factors affect enzyme function In these quizzes you will apply your knowledge of protein structure and be able to interpret graphs.

The structure of DNA ( and its single stranded relative RNA) is also tested in this unit; looking at Nucleotide structure, and phosphodiester bonds. In this unit there is also a quiz looking at the fine detail of DNA replication; understanding the role of each enzyme, where it attaches, and which direction it moves in. You are also tested on the evidence of Semi Conservative Replication.

Lastly there is a quiz testing your understanding of the role of inorganic ions such as sodium and phosphate. Building up to  the structure and  role of ATP. The importance of water is the last little section in this quiz , finishing off knowledge which will support every aspect of your A Level understanding from now on.

Biological Molecules

Cells

In this unit of A Level Biology: Cells, we start by testing your knowledge of Eukaryotic Organelles. Extending on from the basics learnt at GCSE, this quiz expects you to be able to identify and give the detailed function from the familiar Nucleus, through to the newly introduced Golgi Body and Smooth Endoplasmic Reticulum.

The next quiz then looks at Prokaryotic structure. Focusing predominantly on Bacteria, this quiz looks at the differences between Prokaryotes and Eukaryotes; particularly looking at DNA and Binary Fission.

Your mathematical skill is tested in Magnification , with your ability to convert units, understand Order of Magnitude, and work out the magnification and Actual size of images shown. Following on from this, Microscopes and Fractionation tests your understanding of the difference between Scanning and Transmission Electron microscopes. It also, applies your knowledge of the technique of Cell fractionation, where centrifugation at different speeds is used to separate out organelles.

Eukaryotic Cell division is tested in the Mitosis quiz. Where you need to be able identify Prophase, Metaphase, Anaphase and Telophase. You also need to understand the role of Interphase in the Cell Cycle.

Two quizzes are dedicated to the Plasma Membrane. You will need to know the structure of the Phosopholipid Bilayer,and  how that relates to function. How different molecules can pass across the Membrane, is also tested and again links into other units further on in A Level Biology.

Lastly we look at the Immune response : both the cellular response via T cells, and the Humoral response via B cells. The role of antibodies is tested both with in the Immune Response, but also in a second quiz on Monoclonal Antibodies.

Cells

Exchanges of Substances with the Environment

In this unit we get our first taste of Physiology in A Level biology – and start to look at how the body functions and systems with-in organisms.

We pick up from GCSE looking at Surface Area to Volume ratio, and adaptations of this that allow organisms to survive; for example,  at different temperatures. Surface area also links into the gaseous exchange systems in humans, insects, fish and plants. Understanding of the human gaseous exchange system also requires understanding and interpreting data on diseases which affect it.

Mass Transport means the movement of substances around a multicellular organism. In many organisms this takes the form of a circulatory system. In this unit, we look at Haemoglobin, and  oxygen dissociation curves. You need to be able to describe the effect of partial pressure of oxygen on haemogoblin’s affinity for oxygen. You also need to be able to describe the Bohr effect, and apply your knowledge to what may be unfamiliar species such as lugworms.

In terms of gross anatomy, at A level several major arteries such as the aorta, pulmonary and renal arteries need to be identified, and more importantly the structural differences between arteries, veins and capillaries. The structures of the heart also need to be identified, all be it in much the same level as higher GCSE. The cardiac cycle is extended from GCSE, looking at interpreting pressure changes , and calculating cardiac output and stroke volume. Cardiovascular disease data must be interpreted, including; atheroma, and thrombus formation.

Mass transport in plants has two separate routes:transpiration for water via xylem, and mass flow for organic substances via phloem.  Once again, GCSE is extended to looking at cohesion -tension in the xylem, and translocation via mass flow hypothesis in plants. In the Mass Flow  Hypothesis, changes in water potential caused by the formation of soluble substances (like glucose) cause pressure changes, which push the solutes towards ‘sinks’ where the solute concentration is lowered.

Exchanges of Substances with the Environment

Genetic Variation and Information

In this unit, we start off with DNA and RNA as the genetic molecules from unit 1, this time  identifying differences between prokaryotic and eukaryotic DNA, and chromosome structure. Extending from GCSE, we look at protein synthesis and the process of  transcription. This is the use of RNA polymerase to make complementary pre-mRNA from a coding section of DNA. The pre-mRNA contains introns, which are then spliced out to form the shorter mRNA. Translation then occurs in the ribosome. Here, we meet a new clover shaped polynucleotide : transfer RNA. tRNA  has  anticodons on the bottom loop, complementary to the codons on the mRNA, and specific amino acids on the top. The ribosome has space for 3 tRNA.s to dock, and join together the amino acids to form a polypeptide.

Genetic variation can occur due to mutation or meiosis. A few simple mutations to the base sequence of DNA are discussed here ( there are more in Unit 8), along with independent segregation and ‘crossing over’ of chromatids in the first phases of meiosis. This genetic variation is then applied to Natural Selection. Students need to be able to differentiate between directional and stabilising selection.

Phylogenetic classification uses evolutionary origins as a way of grouping organisms into a hierarchy. The different organisms can be grouped by biochemical similarity . The most obvious of this is the sequence of DNA, which is obviously linked to the primary structure of key proteins.

In this unit, students are also expected to develop maths skills , including calculation of means and standard deviation, and understanding what standard deviation represents.  Although, standard deviation will not be need to be calculated in the AQA exam.

Genetic Variation & Information