Biology🩷

• Cell


  The basic unit of structure and function in living things
• All organisms are made of cells
• All new cells are produced by division of existing cells
• Microscope


  Magnifies cells to show a number of features clearly
• Organelles


  The structures found inside the cell
• Micrometre (μm)


  A small unit used to measure the size of cells and cellular structures
• A typical animal cell is about 25 μm in diameter, much smaller than plant cells
• Structures found in both plant and animal cells and their functions

  • List to be provided
• Bacteria have a wide variety of shapes and sizes, and are microscopic single-celled organisms (1000x smaller than a plant cell)
• Characteristics of bacterial cells

  • Cell wall made of peptidoglycan (murein)
  • Partially permeable cell membrane
  • Cytoplasm containing glycogen granules
  • Ribosomes for protein synthesis
  • Prokaryotic cells lacking a nucleus
  • Circular or loop of chromosomal DNA floating in the cytoplasm
• Plasmids


  Small rings of DNA floating in the cytoplasm that contain extra genes advantageous to the host, such as antibiotic-resistance genes
• Some bacteria also have a flagellum or several flagella that allow them to move, and a slime capsule for protection in harsh conditions
• Specialised cells


  Cells capable of carrying out specific functions, with structural features adapted to suit those functions
• Differentiation


  The process by which a cell becomes specialized for a particular function
• Examples of specialised cells


  • List to be provided
• Levels of organisation


  • List to be provided
• Magnification


  The process of enlarging the image of a small object to make it appear larger
• The best unit to use for magnification is usually the millimetre (mm), but when viewing specimens under a light microscope, the unit of measurement is the micrometre (μm)
• When doing calculations, all measurements must be in the same units, and it is best to use the smallest unit of measurement shown in the question
• Light microscope


  An optical instrument used to magnify an image of a tiny object that is not visible to the human eye
• Parts of a compound microscope

  • List to be provided
• Diagram showing how to place the coverslip
• Characteristics of living organisms

  Movement<|>Respiration<|>Sensitivity (Irritability)<|>Growth<|>Reproduction<|>Excretion<|>Nutrition
• Aerobic respiration


  Glucose + oxygen = carbon dioxide + water + energy
• Anaerobic respiration


  Occurs in the absence of oxygen
• Breathing


  The physical process in which air is taken in and out of the body
• Sensitivity (Irritability)


  The ability to detect and respond to changes in the internal or external environment
• Stimulus


  A change in the environment
• Senses


  Used by animals for sensitivity (irritability)
• Growth


  A permanent increase in size and dry mass by an increase in cell number or cell size or both
• Irreversible


  A permanent increase in size
• Development


  An increase in complexity e.g. development of breasts and widening of hips in girls and deepening of voice and broadening of shoulders in boys during adolescence
• Excretion


  The removal of the waste products of metabolism and substances in excess of requirements
• Excretion


  • Carbon dioxide is excreted as a waste product of respiration by living organisms
  • Excess salts are excreted by kidneys and passed out in urine
• Egestion


  The passing of undigested food in the form of faeces out of the body through the anus: it is not a form of excretion
• Characteristics of organisms


  • Movement
  • Respiration
  • Sensitivity (Irritability)
  • Growth
  • Reproduction
  • Excretion
  • Nutrition