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AQA GCSE Biology

GCSE · AQABiology42 โน้ต ใน 8 โฟลเดอร์, 147 KB

โน้ตทบทวน 42 รายการ สร้างโดย cookie แบ่งเป็น 8 ส่วนตามหัวข้อของหลักสูตร

Notes for AQA GCSE Biology (8461), in folders for the seven topics of the specification in its order, with the ten required practicals in the topics they belong to. A last folder covers working scientifically and the maths skills the course uses. Higher-tier content is marked where it sits. Delete any folder or note your course leaves out once the notes are yours.

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มีอะไรอยู่ข้างใน

  • Cell biology
    • Cells and specialisation4 KB
    • Microscopy and magnification5 KB
    • Cell division and stem cells3 KB
    • Culturing microorganisms5 KB
    • Diffusion and exchange surfaces3 KB
    • Osmosis and active transport4 KB
  • Organisation
    • Enzymes5 KB
    • Digestion and food tests3 KB
    • The heart, lungs and blood vessels4 KB
    • Blood and coronary heart disease3 KB
    • Health, lifestyle and cancer4 KB
    • Plant tissues, transpiration and translocation5 KB
  • Infection and response
    • Pathogens and communicable diseases3 KB
    • Human defences and vaccination3 KB
    • Antibiotics, painkillers and new drugs3 KB
    • Monoclonal antibodies2 KB
    • Plant disease and defences3 KB
  • Bioenergetics
    • Photosynthesis5 KB
    • Respiration, exercise and metabolism3 KB
  • Homeostasis and response
    • The nervous system and reflexes4 KB
    • The brain and the eye3 KB
    • The endocrine system and negative feedback2 KB
    • Blood glucose and diabetes3 KB
    • Body temperature and water balance4 KB
    • Hormones in reproduction4 KB
    • Plant hormones3 KB
  • Inheritance, variation and evolution
    • Sexual and asexual reproduction and meiosis3 KB
    • DNA, the genome and protein synthesis3 KB
    • Genetic inheritance and inherited disorders4 KB
    • Variation, evolution and natural selection3 KB
    • Selective breeding, genetic engineering and cloning4 KB
    • Darwin, Wallace and Mendel4 KB
    • Evidence for evolution3 KB
    • Classification2 KB
  • Ecology
    • Communities, adaptations and competition3 KB
    • Food chains and sampling4 KB
    • Trophic levels and biomass transfer3 KB
    • Cycling materials and decomposition4 KB
    • Biodiversity and human impact4 KB
    • Food security and food production3 KB
  • Working scientifically and maths skills
    • Investigations and evaluating data5 KB
    • Maths skills for biology4 KB

โน้ตรายการแรก

Cell biology / Cells and specialisation

All living things are made of cells, and the cells of plants, animals and bacteria share some features while differing in others. Knowing which structure does which job lets you explain why a particular cell looks the way it does.

Eukaryotic and prokaryotic cells

Plant and animal cells are eukaryotic cells. Each has a nucleus that holds its genetic material, as well as a cell membrane and cytoplasm. Prokaryotic cells are the bacteria, and they are far smaller. A bacterial cell has a cell wall outside its membrane and no nucleus; its DNA is one loop lying free in the cytoplasm, and it may also carry one or more little rings of extra DNA called plasmids.

FeatureEukaryotic cellProkaryotic cell
Sizelargermuch smaller
Genetic materialin a nucleusa single DNA loop, free in the cytoplasm
Plasmidsnoneone or more may be present
Cell wallcellulose in plants, none in animalspresent

Structures in animal and plant cells

The parts found in most animal cells are a nucleus, cytoplasm, a membrane, mitochondria and ribosomes. Plant cells commonly have those too, with chloroplasts and a large permanent vacuole full of cell sap in addition. A plant or algal cell is also enclosed by a cellulose cell wall.

StructureWhat it does
Nucleuscontains the genetic material (DNA in chromosomes) and controls the activities of the cell
Cytoplasma watery gel where most chemical reactions take place, and where the other structures sit
Cell membranecontrols which substances pass into and out of the cell
Mitochondriathe site of aerobic respiration, which transfers the energy the cell needs
Ribosomeswhere proteins are made
Chloroplastscontain chlorophyll, which absorbs light for photosynthesis, so they are found in the green parts of plants
Permanent vacuolefilled with cell sap, it helps keep the cell firm and stores dissolved substances
Cell wallmade of cellulose, it strengthens the cell and stops it bursting when water enters
Plasmida small ring of DNA in a bacterial cell, often carrying extra genes

A cell that carries out a lot of respiration, such as a muscle cell, contains many mitochondria. A cell in the palisade layer of a leaf has many chloroplasts. Linking a structure to its function in this way is how you explain why a cell is suited to its job.

Specialised cells

A cell is specialised when its structure is adapted for one particular job. In animals the standard examples are sperm, nerve and muscle cells, and in plants root hair, xylem and phloem cells.

CellAdaptationsHow they help
Sperm cella tail; a streamlined head holding the nucleus and an enzyme-filled tip; many mitochondria in the middle sectionthe tail moves the cell towards the egg, the enzymes help it get through the egg's outer layer, and the mitochondria supply energy for swimming
Nerve cellvery long, with branched endings and an insulating sheath around the fibreit carries electrical impulses over long distances and connects with many other cells
Muscle cellcontains protein fibres that can shorten, and many mitochondriathe fibres contract to produce movement, using energy from respiration
Root hair cella long, thin extension that reaches into the soil; a large vacuolethe extension gives a large surface area for taking up water and mineral ions
Xylem cellhollow, with walls strengthened by lignin, and no end walls between neighbouring cellsforms a continuous tube that carries water and minerals up the plant and supports it
Phloem cellelongated cells joined end to end, with pores in the end wallsdissolved sugars can pass from one cell to the next

Cell differentiation

As an organism develops, its cells differentiate to form different types of cell. In doing so a cell acquires the sub-cellular structures it needs for its job, and it has then become specialised.

In animals most cells differentiate early in development, so later in life dividing is largely for repair and replacement. Many plant cells stay able to differentiate for the whole of the plant's life, which is why a plant can go on producing new roots, shoots and leaves.

Differentiation matters because a multicellular organism needs many different cell types working together. A single kind of cell could not carry impulses, contract, absorb water and make gametes as well as cells that have each become specialised for one task.

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