1.2

• Eukaryotic cells


  Cells that carry specific functions
• Centriole


  • Found in eukaryotic cells
  • Organises microtubules during cell division
• Nucleus


  • Contains DNA
  • Surrounded by nuclear envelope
  • Contains chromatin and nucleolus
• Organelles


  • Found in the cytoplasm
  • Membrane-bound
  • E.g. plants have chloroplasts
• Mitochondria


  The powerhouse of the cell, producing ATP through aerobic respiration
• Chloroplasts


  • Found in photosynthetic plants
  • Site of photosynthesis
  • Contain thylakoid membranes and stroma
• Endoplasmic reticulum


  • System of interconnected flattened sacs (cisternae)
  • Rough ER has ribosomes, smooth ER lacks ribosomes
• Ribosomes


  Organelles that assemble proteins during translation
• Golgi body


  • Stack of curved cisternae
  • Modifies and packages proteins into vesicles for export
• Lysosomes


  • Contain digestive enzymes
  • Digest worn out organelles and foreign material
• Centrioles


  • Organise microtubules to form the spindle during cell division
• Vacuole


  • Large central vacuole in plant cells
  • Provides structural support and stores chemicals
• Cell wall


  • Provides strength and support to plant cells
  • Allows transport of water and molecules
• Prokaryotic cells lack a true nucleus and membrane-bound organelles
• Viruses lack cytoplasm, organelles and chromosomes, only have a core of nucleic acid and protein coat
• Cells can be measured from electron micrographs using a formula
• Levels of organisation


  • Single-celled organisms carry out all life processes in one cell
  • Multicellular organisms have specialised cells that form tissues and organs
• Main types of tissue in mammals


  • Connective
  • Muscle
  • Epithelial
• Connective tissue


  • Supports, connects or separates different tissues and organs
  • Cells are contained in an extracellular fluid or matrix
• Muscle tissue


  • Skeletal muscle - powerful contraction for locomotion
  • Smooth muscle - rhythmic contraction in internal organs
  • Cardiac muscle - rhythmic contraction of the heart
• Epithelial tissue


  • Covers and lines the body
  • Cells sit on a basement membrane
  • Examples: simple cuboidal, columnar, squamous
• Organs and organ systems

  Groups of organs working together with a particular role