topic 1- cell biology

• all living things are made of cells
• cells can either be prokaryotic or eukaryotic
• what are eukaryotic cells

  plant and animal cells
• what are prokaryotic cells

  bacteria cells
• what is a eukaryote

  an organism made up of eukaryotic cells
• what is a prokaryote

  a prokaryotic cell
• the different parts of a cell are subcellular structures
• what subcellular structures do most animal cells have


  nucleus

  cytoplasm

  cell membrane

  mitochondria

  ribosomes
• the nucleus contains genetic material that controls the activities of the cell
• the cytoplasm is a gel like substances where most chemical reactions happen. it contains enzymes that control these chemical reactions.
• the cell membrane holds the cell together and controls what goes in and out
• the mitochondria is where most of the reactions for aerobic respiration takes place. respiration transfers energy that the cell needs to be able to work.
• ribosomes are where proteins are made in the cell
• plants usually have all the subcellular structures an animal cell aswell as a couple more
• what additional subcellular structures do plant cells have

  cell wall

  permanent vacuole

  chloroplast
• a cell wall is made of cellulose, it supports and strengthens the cell.
• the permanent vacuole contains cell sap, a weak solution of sugar and salts.
• chloroplasts is where photosynthesis occurs which makes food for the plants. they contain a green substances, called chlorophyll, which absorbs light for photosynthesis
• prokaryotic cells are much smaller than eukaryotic
• subcellular structures of a bacteria cell

  cytoplasm

  cell membrane

  cell wall

  a strand of DNA

  plasmids
• plasmids are small rings of DNA
• light microscopes allow us to see individual cells and large subcellular structures, such as the nucleus
• electron microscopes use electrons instead of light to form an image
• electron microscopes have a much higher magnification and higher resolution than light microscopes
• electron microscopes allow us to see more smaller things in more detail, such as internal structures of mitochondria and ribosomes
• what is the magnification formula

  magnification = image size / real size
• if you want to look at a specimen under a light microscope, you need to put it on the microscope slide first
• Prepare a microscope slide to view onion cells

  1. Add a drop of water to the middle of the clean slide

  2. Cut up an onion and separate it into different layers, use tissue to peel off the epidermal tissues from the bottom of one of the layers

  3. Using tweezers, place the epidermal tissue into the water on the slide

  4. Add a drop of iodine solution (iodine solution is a stain, stains are used to highlight objects in a cell by adding colour to them)

  5. Place a cover slip on top (stand the cover slip upright on the slide, next to the water droplet, then carefully tilt and lower it so it covers the specimen, try not to get any bubbles because they will obstruct your view)
• how to use a light microscope to look at prepared slides

  1. clip the slide you prepared onto the stage
  2. select the lowest powered objective lens
  3. use the coarse adjustment knob to move the stage up to just below the objective lens
  4. look down the eyepiece. use the coarse adjustment knob to move the stage downwards until image is roughly in focus
  5. adjust the focus with the fine adjustment knob, until you get a clear image of what's on the slide
  6. if you need to see the slide with greater magnification, swap to a higher powered objective lens and refocus
• cells differentiate to become specialised
• as cells change they develop different subcellular structures and turn into different types of cells. this allows them to carry out specific functions.
• most differentiation occurs as an organism develops
• in most animal cells, the ability to differentiate is lost at an early stage, after they become specialised
• plant cells never lose the ability to differentiate
• how are sperm cells specialised for reproduction

  the function of the sperm is to get the male DNA to the female DNA. it has a long tail and streamlined head to swim to the egg. there is lots of mitochondria in the cell to give it the needed energy.

  it also carries enzymes on its head to digest through the eggs cell membrane
• the cells that differentiate in mature animals are mainly used for repairing and replacing blood, such as skin or blood cells
• how are nerve cells specialised for rapid signalling

  the function of the nerve cells is to carry electrical signals from one part of the body to another. these cells are long and have branched connections at their ends to connect to other nerve cells and form a network throughout the body.
• how are muscle cells specialised for contraction

  the function of a muscle cell is to contract quickly. these cells are long and carry a lot of mitochondria to generate energy needed for contraction
• how are root hair cells are specialised for absorbing water and minerals

  root hair cells are on the surface of plant roots, which grow into long 'hairs' that tick out into the soil. this gives the plants a big surface area for absorbing water and mineral ions from the soil.
• how are phloem and xylem cells specialised for transporting substances

  phloem and xylem cells form phloem and xylem tubes, which transports such as food and water around plants. to form tubes, the cells are long and joined end to end. xylem cells are hollow in the centre and phloem have very few subcellular structures so that stuff can flow through them