Organisms

• Cell


  • Very small
  • Large organisms contain millions of cells
  • Some multicellular
  • Some unicellular
  • Made from existing cells
  • New cell formed when a fully grown cell divides
• Animal cell


  • Cell (surface) membrane
  • Large permanent vacuole
  • Small/no temporary vacuole(s)
• Plant cell


  • Cell (surface) membrane
  • Large permanent vacuole
  • Small/no temporary vacuole(s)
  • Cell wall
• Bacterial cell


  • Cell wall made of peptidoglycan or murein
  • Partially permeable cell membrane pressed tightly against inside of cell wall
  • Cytoplasm
  • Ribosomes
  • No nucleus
  • No mitochondria
  • No chloroplast
  • Plasmids
• To see cells clearly, you need to use a microscope
• Light microscope


  Used in school
• Electron microscope


  Used for research of small cell structures
• Photomicrograph


  A photograph taken using a light microscope
• Electron micrograph


  A picture taken with an electron microscope
• Cell (surface) membrane


  • Found around the outside of cells
  • Very thin layer of protein and fat
  • Controls what moves into and out of the cell
  • Partially/selectively permeable
  • Allows some molecules and ions to pass through and others not
  • Separates content of cell from environment
  • Pressed tightly against inside of cell wall in plant cells
• Cell wall


  • Not present in animal cells
  • Surrounds plant cells
  • Made mainly of cellulose
  • Cellulose is a polysaccharide that forms fibres which criss-cross over one another to form a very strong covering to the cell
  • Helps to protect and support the cell
  • Prevents cells from bursting
  • Fully permeable, allows very large molecules to go through
• Cytoplasm


  • Clear jelly-like fluid
  • Nearly all water
  • Contains substances dissolved in it, especially proteins
  • Site where different metabolic reactions take place
• Vacuole


  • Fluid-filled space inside cell
  • Surrounded by own membrane
  • In plant cells: large permanent, contain cell sap, help keep shape
  • In animal cells: small temporary, also called vesicles, contain solutions
• Nucleus


  • Where genetic information is stored
  • Genetic info kept on chromosomes
  • Inherited from organism's parents
  • Made of DNA
  • Info on DNA determines kind of proteins made in the cell
  • Chromosomes are very long and thin, cannot easily be seen even using an electron microscope
  • When cells divide, chromosomes become short and thick and can be seen with a good light microscope
• Chloroplasts


  • Site of photosynthesis
  • Contains chlorophyll, a green pigment
  • Absorb energy from sunlight and use it to make food by photosynthesis
  • Mostly found in plant cells, never in animal cells
  • Often contain starch grains made by photosynthesis
  • Animal cells never contain starch grains, but rather glycogen
• Mitochondria


  • Found in almost all plant and animal cells
  • Parts of the cell where aerobic respiration happens
  • Energy released from glucose
  • The more mitochondria present, the more energy the cell needs (e.g. muscle cells packed full of mitochondria)
• Ribosomes


  • Tiny structures in almost all animal and plant cells
  • So small can only be seen with electron microscope
  • Site of protein synthesis
• Bacterial cell


  • Always have a cell wall made of peptidoglycan or murein
  • Help support the cell and stop it from bursting if taking up a lot of water
  • Partially permeable cell membrane pressed tightly against inside of cell wall
  • Controls what enters and leaves the cell
  • Have cytoplasm and ribosomes, same functions as in plant and animal cells
  • Do not have mitochondria or chloroplasts
• Bacterial cell DNA


  • No nucleus
  • Prokaryotic (no nucleus) cells
  • No chromosomes
  • Have circular DNA, sometimes called bacterial chromosome, with instructions for making proteins
  • Often have one or more smaller circles of DNA called plasmids, used for genetic modification
• Differences between cell types

  • Animal cell
  • Plant cell
  • Bacterial cell
• Cell


  • Basic structural and functional unit of all known living organisms
  • Smallest unit of life
  • Building blocks of life
  • All living cells consist of one or more cells - up to trillions (different types and functions)
  • Contain smaller organelles (cell structures)
  • Perform various functions - metabolism, productions, transportation and secretion of substances
  • All cells are made from pre-existing cells by means of cell division
• Specialised cells


  • Multicellular organisms have millions of cells
  • Not all cells are alike
  • Human cells have same features found in most animal cells
  • Most cells have a particular function to perform
  • Structure is modified to help carry out that function
  • Same is true for plant cells, they have slightly different structures that relate to their specific functions
• Tissues


  • Group of similar cells working together to perform a particular function
  • E.g. layer of cells lining the stomach, make enzymes to help digest food
  • Stomach also contains other tissues like muscle tissue to make the wall move and churn food
  • Plant tissues include epidermis and palisade tissue to carry out photosynthesis
• Organ


  Group of different tissues working together to perform a particular function
• Organ system


  Group of organs performing several closely related functions
• Different organs of the human body

  • 78 organs divided into 13 major organ systems
  • 5 vital organs: heart, brain, lungs, kidneys, liver
  • Skin is the largest organ, protects body from outside harm
  • Heart pumps blood to every part of the body
  • Torso houses many of the body's organs
  • Liver has to detoxify the body
  • Kidneys excrete excess substances and urea
  • Lungs breathe in oxygen and out carbon dioxide
• Different organs of plants

  • Roots, stems and leaves
  • Reproductive organs variable, angiosperms have flowers, seeds and fruits, conifers have cones
• Different organ systems of the human body

  • Nervous
  • Circulatory
  • Digestive
  • Muscular
  • Skeletal
  • Respiratory
  • Integumentary (skin, hair, nails, sweat and oil glands)
  • Lymphatic
  • Endocrine
  • Urinary/excretory
  • Reproductive
• Different organ systems of plants

  • Reproductive
  • Shoot
  • Root
• Image size (I)


  • Actual size (A)
  • Magnification (M)
  • Always use mm
  • Convert between mm and μm
  • All numbers always in the same units
  • Magnification always written with X in front of the answer
• I = 40 mm


  A = 8 mm