B1.1 (cell structures)

• what are structures inside the cell known as?

  Subcellular structures
• what are the 2 main types of cell?


  Eukaryotic and prokaryotic
• what are eukaryotic cells?


  They contain genetic material in a nucleus, they are complex and relatively large, between 10 and 100 micrometers.
• give an example of eukaryotic cells?

  plant and animal cells
• what are prokaryotic cells?


  They do not contain a nucleus, instead the genetic material floats in the cytoplasm. They are simple cells, and typically smaller than eukaryotic cells. most have a size between 1 and 10 micrometers
• give an example of a prokaryotic cell?

  Bacterial cells
• what are typical features of a eukaryotic cell?


  A nucleus, cytoplasm, a cell membrane and mitochondria
• what does the nucleus do?


  Controls the activity inside the cell, contains the genetic material (arranged as chromosomes) which determines the appearance or function of the cell and contains instructions to grow new cells or organisms
• what do mitochondria do?


  They are where respiration happens, protein molecules known as enzymes enable glucose and oxygen to react together which causes vital energy to be transferred to the organism
• what is the cell membrane?

  A selective barrier that controls which substances pass in and out of the cell, the membrane also contains receptor molecules
• what is the cytoplasm?

  a jelly-like substance, chemical reactions that keep the cell alive happen here
• what subcellular structures do plants cells contain that animal cells do not have?

  Cell wall, vacuole and chloroplasts
• what do chloroplasts do?

  They contain green chlorophyll which transfers energy from the sun to the plant as light which is then used in photosynthesis, chloroplasts are only in the green parts of plants
• what does the vacuole do?

  Full of cell sap, a watery solution of sugar and salts. it helps to keep the cell rigid and support the plant and keep it upright
• what does the cell wall do?

  It surrounds the cell, it is made of a tough fibre called cellulose. it makes the wall rigid and supports the cell
• describe bacteria


  The smallest living organisms, they are unicellular (just consist of one cell) but each cell can still carry out the seven life processes
• what are the seven life processes?

  movement, reproduction, sensitivity, growth, respiration, excretion and nutrition
• What does one dot on an agar plate actually show?

  A bacterial colony of millions of bacteria
• describe prokaryotes


  Single celled organisms without a nucleus and most are bacteria
• give 3 examples of prokaryotes

  1, escherichia coli (e coli) which causes food poisoning

  2, streptococcus bacteria which causes sore throats

  3, streptomyces bacteria, found in soil and the streptomycin antibiotic comes from this bacteria, it kills many other disease causing bacteria
• What do prokaryotic cells contain?

  cytoplasm, cell membrane, genetic material and cell wall
• what is the cell wall in prokaryotic cells made from?

  Peptidoglycan which holds the cell together and protects it
• what does genetic material do?

  It floats freely in the cytoplasm, there is one long strand of DNA called the bacterial chromosome which is normally circular
• what do bacterial cells all contain?

  a cell membrane, cell wall and genetic material
• what do some bacterial cells contain that others dont?

  flagella, pili, slime capsule, plasmid
• what are flagella?


  Tail like structures that allow the cell to move through liquids
• what are pili?


  Tiny hair like structures that enable the cell to attach to structures such as the cells that line your digestive tract, pili are also used to transfer genetic material between bacteria
• what is the slime capsule?


  A layer outside the cell wall, it protects a bacterium from drying out and from poisonous substances, it also helps bacteria to stick to smooth surfaces
• what is a plasmid?


  A circular piece of dna that is used to store extra genes, these genes arent used for every day survival but can help in times of stress , this is where antibiotic resistance genes are normally found
• what are 2 differences between plant and animal cells?

  Plant cells have a cell wall, animal cells do not

  plant cells have 1 large vacuole where animal cells have multiple smaller vacuoles
• what do you use a light microscope to do?

  To observe small structures in detail
• how does a light microscope work?

  It passes light through an object placed on a slide on the stage, then through 2 glass lenses, the lenses magnify the object so that when you view it through the eyepiece, you see it in more detail
• what are the 2 lenses on a microscope called?


  Objective lens and eyepiece lens
• Steps to observe cells through a microscope

  1. Move the stage to its lowest position

  2. Select the objective lens with the lowest magnification

  3. Place the slide with cells on it on the stage

  4. Raise the stage to its highest position and make sure the glass does not touch the lens

  5. Lower the stage slowly using the coarse focus knob until you see your object (it may be blurred)

  6. Turn the fine focus knob slowly until the object comes into full focus

  7. To see cells in greater detail, switch to a higher magnification objective lens without moving the stage, use the fine focus knob to bring the object into clear focus again
• what is the total magnification?

  Total magnification = eyepiece lens magnification x objective lens magnification
• why do scientists stain cells?

  Many cells are colourless, so scientists stain them to make them easier to observe, some stains colour the whole cell while others highlight specific subcellular structures
• what are the 3 common stains?

  Methylene blue, iodine and crystal violet
• what does methylene blue do?

  Makes it easier to see the nucleus of an animal cell
• what does iodine do?

  Makes it easier to see plant cell nuclei
• what does crystal violet do?

  Stains bacteria cell walls