National Year 10 Biology
Chapters: 4
1. 4.1 Cell biology
4.1.1 Cell structure · 4.1.2 Cell division · 4.1.3 Transport in cells
- The Cell: Basic Unit of Life – Every living thing is made of cells. Robert Hooke first saw cells in cork in 1665. Cells are prokaryotic (no true nucleus, like bacteria) or eukaryotic (true nucleus). Plant cells have a cell wall, chloroplasts and a big vacuole; animal cells do not. Each organelle has a job. Water enters and leaves cells by osmosis. Cells make new cells by mitosis (growth) and meiosis (sex cells).
- Cell Division: How One Cell Becomes Two (or Four) – All living things grow because their cells divide. Every cell comes from another cell (cell theory). Before dividing, a cell copies its chromosomes. Mitosis gives 2 identical cells with the same chromosome number, used for growth and repair. Meiosis divides twice and gives 4 cells with half the chromosomes, used to make sex cells.
- Membrane Transport: How Things Get In and Out of a Cell – The cell membrane is a thin double layer of fat-like molecules with proteins in it. It lets some substances through and stops others (selectively permeable). Diffusion moves particles from high to low concentration with no energy. Facilitated diffusion does the same through protein channels. Osmosis is the diffusion of water through a partially permeable membrane. Active transport uses ATP and a protein pump to move particles from low to high concentration. Very large things enter and leave in bubbles (endocytosis and exocytosis).
2. 4.2 Organisation
4.2.1 Principles of organisation · 4.2.2 Animal tissues, organs and organ systems · 4.2.3 Plant tissues, organs and systems
- Tissues: Plant and Animal Tissues – A tissue is a group of similar cells that do one job together. Cells form tissues, tissues form organs, organs form organ systems and systems form an organism. Plants have dividing meristematic tissue and non-dividing permanent tissue, including xylem (water up) and phloem (food both ways). Animals have epithelial, connective, muscular and nervous tissue. Bones, muscles and joints need good posture, exercise and food rich in calcium.
- Human Body Systems – Your body is organised in levels: cells make tissues, tissues make organs, organs make organ systems, and all systems together make you, the organism. Each system has a main job: skeletal (frame), muscular (movement), circulatory (transport), respiratory (gas exchange), digestive (food), excretory (waste), nervous and endocrine (control), immune (defence), integumentary (skin, hair, nails) and reproductive. No system works alone: during exercise the muscles, heart, lungs and nerves all change together to keep the inside of the body steady (homeostasis).
3. 4.3 Infection and response
4.3.1 Communicable diseases · 4.3.2 Monoclonal antibodies (Biology only) (HT) · 4.3.3 Plant disease (Biology only)
- Infectious Diseases: How Germs Spread and How We Stop Them – An infectious (communicable) disease is caused by a tiny living thing called a pathogen: a bacterium, virus, fungus or protist. It passes from one person to another through air, water and food, touch, or a vector such as a mosquito. The body fights back with skin, mucus, stomach acid and white blood cells. Vaccines train the immune system in advance. Hand washing, clean water, cooking food well, mosquito nets and staying home when sick all cut the spread.
- Monoclonal Antibodies – An antibody is a Y-shaped protein that fits one antigen only. Monoclonal antibodies are many copies of one exact antibody, made by one clone of cells. Scientists inject a mouse with an antigen, take its antibody-making lymphocytes, and fuse them with fast-dividing tumour cells to make hybridoma cells. A hybridoma divides into a clone that makes lots of the same antibody. These antibodies are used in pregnancy tests, in labs and hospitals to measure chemicals and find pathogens, to locate molecules such as clots or cancer cells, and to carry drugs to cancer cells. They are very specific but can cause side effects and are costly.
- Plant Diseases and Plant Defences – Plants get ill too. Signs of disease include stunted growth, spots on leaves, rotting areas, growths, malformed stems or leaves, discoloured patches and visible pests. Causes include pathogens (viruses, bacteria, fungi), insects such as aphids, and lack of mineral ions: low nitrate stunts growth, low magnesium turns leaves yellow (chlorosis). A disease is identified using a guide or website, a lab test, or a test kit with monoclonal antibodies. Plants defend themselves with physical barriers (waxy cuticle, cellulose cell walls, bark), chemical defences (antibacterial chemicals, poisons) and mechanical defences (thorns and hairs, drooping leaves, mimicry).
4. 4.4 Bioenergetics
4.4.1 Photosynthesis · 4.4.2 Respiration
- Life Processes and Photosynthesis – Life processes are the jobs every living body must keep doing to stay alive: nutrition, respiration, transport and excretion. Green plants do nutrition by photosynthesis: using sunlight and chlorophyll, they turn carbon dioxide and water into glucose and give out oxygen.
- Respiration: Aerobic, Anaerobic and the Human Lungs – Respiration is the breakdown of food, usually glucose, inside cells to release energy, stored as ATP. With oxygen (aerobic) glucose is fully broken into carbon dioxide and water and gives much energy; without oxygen (anaerobic) it gives little energy and makes ethanol (yeast) or lactic acid (muscles). Our lungs bring oxygen to the blood through millions of alveoli.