Biology AS Cambridge

Compare prokaryotes and eukaryotes, outlining membrane-bound organelles, nucleus, DNA, histones, and ribosome differences; explore cell walls, capsules, plasmids, and viral structures.

Examine organelles from rough and smooth endoplasmic reticulum to Golgi and lysosomes, and analyze mitochondria with cristae and endosymbiotic origins, plus chloroplasts, photosynthesis, and Calvin cycle.

explore animal and plant cell structure, cell membranes, organelles, transport, energy production, and protein processing, including mitochondria, endoplasmic reticulum, Golgi, and chloroplasts.

Enzymes act as biological catalysts with substrate specificity, explained by lock-and-key and induced-fit models, and are modulated by inhibitors, activation energy, concentrations, temperature, and pH.

Explore competitive and non-competitive enzyme inhibition, including reversible and irreversible types, with end-product inhibition, and learn how Km and Vmax reveal enzyme affinity and maximum rate.

Investigate enzyme catalysis using liver homogenate and hydrogen peroxide, observing oxygen bubbles, and analyze how temperature, pH, substrates, and inhibitors shape enzyme activity and regulation.

Plot enzyme data, calculate mean rates, and interpret line of best fit while exploring substrate concentration, temperature, pH, inhibitors, and protease applications.

Explore the phospholipid bilayer and fluid mosaic membrane, with integral and peripheral proteins, cholesterol, and glycocalyx, that create a selectively permeable barrier for transport and signaling.

Explore the cell membrane structure and transport, including diffusion, facilitated diffusion via channel and carrier proteins, voltage-gated channels, osmosis, water potential, and active transport mechanisms.

Explore cell membrane signaling, from receptor binding and G protein activation to second messenger cascades that amplify signals and regulate processes like transcription and secretion.

Explore mitosis in the somatic diploid cell cycle, detailing chromosome structure with chromatin, histones, nucleosomes, chromatids, centromere and kinetochore, and contrast with meiosis and haploid gametes.

Explore mitosis stages—prophase, metaphase, interphase, and telophase—covering chromatin condensation, centrosome replication, and spindle formation. Watch chromatids align and separate, nuclei reform, and cytokinesis finishes cell division.

Understand the DNA nucleotide structure, sugar-phosphate backbone, and anti-parallel strands, and semi-conservative replication, then follow transcription and translation from RNA to protein by ribosomes.

Explore transcription and translation, from DNA unwinding to messenger RNA synthesis and ribosome-guided protein assembly. Explain how codons, anticodons, start and stop signals, and sickle cell mutation affect polypeptide formation.

DNA replication and protein synthesis are explored through transcription and translation, detailing RNA polymerase, messenger RNA, transfer RNA with anticodons, ribosomes, start and stop codons.

Learn how plants transport water and minerals via xylem and phloem, driven by transpiration pull and mass flow, with leaves, stems, roots, and key tissues like endodermis and cambium.

Explore how water moves from soil to leaves via root hairs and apoplastic and symplastic routes through xylem, via transpiration pull, cohesion, and adhesion, and how phloem transports sap.

Explore phloem transport: companion cells load sucrose into sieve elements to drive active mass flow from source to sink, contrasting with xylem's passive transport.

Examines transport in plants, detailing xylem and phloem structure and function. Discusses tissue distribution in root and stem, root hair cells, and key adaptations.

Examine gas exchange efficiency from trachea to alveoli, including warming and cleaning air, and note smoking's link to COPD and lung cancer.

Learn to use a respirometer with potassium hydroxide to measure maggots' oxygen consumption, including equilibration, temperature control, and reading changes. It also explains measuring carbon dioxide by a water setup.

Explain differences between inspired, alveolar, and expired air in oxygen and carbon dioxide, and discuss diffusion, concentration gradients, goblet cells, cilia, and smoke's impact on gas exchange.

Learn how pathogens cause infectious diseases and how direct, indirect, and vector transmission shapes prevention, with cholera, malaria, and AIDS as examples.

Describe how HIV, a retrovirus with reverse transcriptase, infects T helper cells, transmits through fluids, and progresses to AIDS with opportunistic infections, while antibody testing and antiretroviral therapy slow progression.

Explore how bacteria develop antibiotic resistance via mutations and plasmids, with vertical and horizontal transmission, penicillin limits in tuberculosis and methicillin-resistant Staphylococcus aureus, and antibiotic sensitivity testing.

Explore external barriers such as skin, nasal hairs, hydrochloric acid and blood clotting, then examine internal immunity with phagocytes, lymphocytes, antibodies, memory cells, and primary and secondary responses.

Explore white blood cells, neutrophils, B and T lymphocytes, and concepts of active versus passive immunity, vaccines, herd immunity, antigenic variation, and monoclonal antibodies.