Cell structure

• Mitochondria


  Organelles where aerobic respiration occurs
• Cell Theory


  New cells are formed from other existing cells and the cell is a fundamental unit of structure, function and organisation in all living organisms
• Ribosomes


  Involved in protein synthesis, made of a large and small subunit constructed from rRNA and protein, occur in two different sizes - 70s in prokaryotes and 80s in eukaryotes
• Endoplasmic reticulum


  • A series of flattened sacs - double membraned cisternae leading on from the nuclear envelope
  • Rough ER - covered in ribosomes for protein synthesis, cisternae then transport the protein
  • Smooth ER - synthesis and transport of lipids
• Golgi body


  • Modifies and packages proteins, produces secreting enzymes, secretes carbohydrates, produces glycoproteins, transports and stores lipids, forms lysosomes and digestive enzymes
• Cell wall


  • A structure made from cellulose microfibrils and pectin, fully permeable for the transport of substances, provides strength to the plant, communicates through the cell wall via plasmodesmata
• Vacuole


  Contains cell sap and is surrounded by the tonoplast membrane
• Centrioles


  Only found in animal cells, 2 cylinders of microtubules that form the spindle in cell division
• Nucleus


  Contains chromatin (DNA coiled with protein) that codes for protein synthesis, surrounded by a double membrane nuclear envelope with pores
• Nucleolus


  Where rRNA and ribosomes are made
• Animal and plant cells are eukaryotic. They contain membrane-bound organelles, DNA is found within a nucleus, cell walls are made of cellulose, ribosomes are 80s and aerobic respiration occurs within mitochondria.
• Mitochondria


  • Cylindrical in shape for a large surface area and reduced diffusion distance, inner membrane is folded into cristae which have stalked particles involved in ATP synthesis, cristae increase the surface area for ATP synthesis
• The presence of 70s ribosomes and DNA in both mitochondria and chloroplasts suggests they were once free-living cells engulfed by ancient bacteria and therefore a symbiotic relationship was developed with them.
• Chloroplasts


  • Contain thylakoid membranes with chlorophyll that trap light energy for photosynthesis
• Magnification


  How many times bigger the drawn image is than the actual size
• Bacteria are prokaryotic cells. They contain no membrane-bound organelles.
• Differences between prokaryotes and eukaryotes

  • Prokaryotes: DNA free in cytoplasm, Ribosomes 70s, Peptidoglycan cell wall, Mesosome for aerobic respiration
  • Eukaryotes: DNA in nucleus, Ribosomes 80s, Cellulose cell wall, Mitochondria for aerobic respiration
• Viruses


  Not a living thing, no cytoplasm or organelles, injects genetic material into a living cell which then creates more virus particles
• Viruses are too small to be seen under a light microscope. Light microscopes can magnify up to x2000 but the ones in school are likely to have a maximum magnification of x400 or x1000. Electron microscopes have a much higher magnification of over x100,000 and better resolution.
• Calibrating the microscope


  Line up eyepiece graticule and stage micrometer, count how many eyepiece units fit into stage units, calculate size of each eyepiece unit, convert to micrometres, remove stage micrometer and observe specimen, draw image with clear lines and label structures
• Cell


  The basic unit of life
• Tissue


  A group of cells with the same structure and function working together
• Types of epithelial tissue

  • Cuboidal - simplest, one cell thick, e.g. PCT kidney
  • Columnar - elongated, can have cilia e.g. trachea
  • Squamous - flattened e.g. alveolar walls
• Types of muscle tissue

  • Skeletal - striated (striped), voluntary, attached to bones for locomotion
  • Smooth - spindle-shaped cells, no stripes, involuntary e.g. skin and digestive tract
  • Cardiac - heart muscle, striated, short fibres, contracts without nerve stimulation, does not tire
• Connective tissue


  Separates tissues and organs, contains elastic and collagen, includes blood, bone and cartilage
• Organ


  A group of tissues working together to perform a particular function
• Organ system


  A system of organs working together with a particular role
• Organism


  All the systems working together forming a discrete individual