A Level Biology Revision Notes

Comprehensive A Level Biology revision notes providing information and assistance for all UK examination boards (AQA, OCR, Edexcel) as well as international curriculum (CIE).

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The Biological Importance of Water

The biological importance of water is due to its unique properties, such as its high polarity, ability to form hydrogen bonds, and high heat capacity, which make it essential for a variety of biological processes, including maintaining cellular structure, regulating temperature, and facilitating metabolic reactions. Keep reading for more detailed A-level Biology revision notes Introduction …

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The Lungs

The lungs are the primary organs of respiration in humans and are responsible for the exchange of oxygen and carbon dioxide between the air and the bloodstream, as well as regulating the pH of the blood through the excretion of carbon dioxide. Keep reading for more detailed A-level Biology revision! The Respiratory System in Humans …

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Organelles Working Together

Various functions within eukaryotic cells depend on organelles working together, such as the mitochondria producing ATP for energy, the endoplasmic reticulum synthesizing and modifying proteins for export, and the Golgi apparatus packaging and directing these proteins to their final destinations. Keep reading for more detailed A-level Biology revision! Summary For example: Let’s imagine you are …

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Nucleic Acids

Introduction Nucleic acids are the biomolecules that are essential for every form of life present on the earth. They are present in all organisms from small viruses and bacteria to large and complex animals like humans and whales.  The word nucleic acid is used collectively for DNA and RNA. Nucleic acids range in size from …

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Cell Division – Mitosis and Meiosis

Cell division – mitosis and meiosis. Mitosis produces two identical daughter cells with the same number of chromosomes as the parent cell. Meiosis produces four genetically diverse haploid daughter cells with half the number of chromosomes as the parent cell. Keep reading for more detailed A-level Biology revision! Living organisms are characterized by their ability …

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Eukaryotic Cellular Division Process

Eukaryotic cellular division, or mitosis, is a highly regulated process involving a series of steps, including DNA replication, chromosome segregation, and cytokinesis, which results in the formation of two identical daughter cells with the same genetic material as the parent cell. Keep reading for more detailed A-level Biology revision! Summary Read more about Replication and …

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Enzymes

Enzymes are biological catalysts that accelerate chemical reactions in living organisms by lowering the activation energy required for a reaction to occur, and are essential for maintaining cellular processes such as metabolism, DNA replication, and protein synthesis. Keep reading for more detailed A-level Biology revision! Summary Read more about Enzyme Mechanism of Action Properties of …

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Crossing Membranes

Crossing membranes is a critical biological process for the transport of molecules and ions across cellular barriers, and can occur through various mechanisms, including diffusion, facilitated diffusion, active transport, and endocytosis/exocytosis. Keep reading for more detailed A-level Biology revision! Summary Substances are transported to and from cells by the following methods: Passive transport This is …

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Cell Structure

Cell structure refers to the various components that make up a cell, including the plasma membrane, cytoplasm, organelles, and genetic material, which work together to maintain the integrity of the cell and carry out essential functions required for life. Keep reading for more detailed A-level Biology revision! Summary The Cell wall Cells of plants, algae, …

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Cell Signaling

Cell signaling is the process by which cells communicate with one another through the transmission of signals, such as hormones or neurotransmitters, which can activate various signaling pathways within cells and modulate gene expression and other cellular responses. Keep reading for more detailed A-level Biology revision! In order to respond to changes in their immediate …

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