Cell Biology

• What is the function of the nucleus?

  contains genetic material that controls the activities of the cell
• What is the function of the cell membrane?


  controls what enters and leaves the cell and also supports the cell
• What is the function of the cell wall?


  made of cellulose which strengthens and supports the cell
• What is the function of the chloroplasts?


  where photosynthesis takes place and contains chlorophyll which absorbs the light needed for photosynthesis to take place
• What is the function of the mitochondria?


  where most of the reactions for aerobic respiration takes place - energy transfer
• What is the function of the ribosomes?


  proteinsynthesis
• What is the function of the cytoplasm?


  where most of the chemical reactions take place - contains enzymes that control these reactions
• What is the function of the vacuole?


  contains cell sap - a weak solution of sugar and salts
• what are the similarities and differences between an animal cell and a plant cell?

  • both eukaryotic cells and both contain a nucleus, mitochondria, ribosomes, a cell membrane, cytoplasm
  • plant cells have a cell wall, chloroplasts and a vacuole and animal cells do not
• what is the difference between a light microscope and a electron microscope?

  • light microscopes allow you to see individual cells and large sub-cellular structures whereas electron microscopes have a much higher resolution and magnification so you can see smaller structures in more detail like mitochondria and chloroplasts - even ribosomes and plasmids
• what does RESOLUTION mean?

  the ability to distinguish between two points - a higher resolution = a sharper image
• what is the equation for magnification?

  magnification = image size/real size
• what is the conversion of mm to micrometres to nanometres?

  mm -> micrometres = x1000

  micrometres -> nanometres = x1000
• what is the practical for preparing a slide?

  • add a drop of water to the middle of a clean slide
  • cut up an onion and place a small bit of epidermis tissue onto the water on the slide
  • add a drop of iodine solution to the epidermis tissue and place a cover slip over ensuring there are no air bubbles there to constrict the view of the cells
• why do we use iodine solution?

  it is a stain which stains the tissue and highlights objects in a cell by adding colour to it
• how do you ensure there a no air bubbles on the slide?

  when placing the cover slip on top, carefully tilt and lower it onto the specimen
• label the parts of the light microscope.

  A - eyepiece

  B - high and low power objective lense

  C - stage

  D - fine adjustment knob

  
• How do you use a light microscope to view the cells?

  • clip slide onto the stage and select the lowest-powered objective lens
  • use the coarse adjustment knob to move stage up just above the objective lens
  • look down eyepiece and use the coarse adjustment knob to move the stage downwards until image is roughly in focus
  • adjust the focus using the fine adjustment knob until you get a clear image
• how should you draw your observations from a microscope?

  • with a pencil - label, unbroken lines
• what is differentiation?


  the process in which a cell changes to become specialised for its job
• how are sperm cells specialised for reproduction?

  • long tail and streamlined head to help it swim to the egg
  • lots of mitochondria in the cell to provide the energy needed
  • carries lots of enzymes in its head to digest through the egg cell membrane
• how are nerve cells specialised for rapid signalling?

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

  • function is to contract quickly
  • long so they have space to contract and contain lots of mitochondria to generate energy needed for contraction
• how are root hair cells specialised for absorbing water and minerals?

  • cells on the surface of plant roots which grow into long hairs that stick out into the soil
  • gives the plant a large surface area for absorbing water and mineral ions from the soil
• how are phloem and xylem specialised for transporting substances?

  • transport substances such as food and water around the plant - cells are long and joined end to end
  • xylem cells are hollow in the centre and phloem cells have very few sub-cellular structures so substances can flow through them
• what is a chromosome?

  a chromosome is a coiled up length of DNA which carry a large number of genes which control characteristics
• describe the process of growth and replication.

  • dna is spread out in long strings and the cell grows and increases the amount of sub-cellular structures such as mitochondria
  • the DNA duplicates so there is one copy for each new cell to form X-shaped chromosomes
• describe the process of mitosis.

  • once the cells contents have been copied then the chromosomes line up down the middle and cell fibres pull them apart to opposite sides of the cell
  • membranes form around the new sets of chromosomes and these become the new nuclei of the cells - nucleus divides
  • the cytoplasm and cell membrane divide to form two identical daughter cells that contain exactly the same DNA
• describe the process of binary fission.

  • circular dna and plasmids replicate, the cell gets bigger and the circular dna moves to opposite sides of the cell
  • cytoplasm begins to divide and new cell walls begin to form
  • cytoplasm divides and two daughter cells are produced each with one copy of the circular DNA but with a variable copies of the plasmids
• how do you find the mean division time?

  the average amount of time it takes for one bacterial cell to divide
• how do you grow bacteria in the lab *practical*?

  • hot agar jelly is poured into shallow plastic dishes called petri dishes
  • when the jelly is cooled and set, use inoculating loops to transfer microorganisms to the culture medium
  • keep the dish in 25 degrees conditions to allow the microorganisms to multiply
• how could you investigate the effect of antibiotics on bacterial growth?

  • place paper discs soaked in different types of antibiotics on the agar plate that has an even covering of bacteria - leave space in between
  • antibiotic should diffuse and antibiotic-resistant bacteria should continue to grow around the discs but bacteria inside will die
  • use a control - a discs soaked in water and not an antibiotic
  • leave plate for 48 hours at 25 degrees
  • the more effective the antibiotic the larger the inhibition zone is
• how do you ensure there is so contamination?

  • any equipment should be sterilised before use to kill any unwanted bacteria - inoculating loop passed through a flame
  • petri dish lid should be taped on to stop microorganisms from the air getting in
  • petri dish stored upside down to stop drops of condensation falling on the agar surface
• what is a stem cell?

  an undifferentiated cell which can divide to produce lots of undifferentiated cells which can be used in medicine and research as they can be grown in a lab to produce clones
• where are stem cells found?

  in early human embryos and in adults bone marrow and other specific areas like that
• how could stem cells be able to cure many diseases?

  • transfer stem cells from a healthy person to replace faulty blood cells in a sick person
  • could make insulin-producing cells for people with diabetes
  • could make nerve cells for people paralysed by spinal injuries
• what is therapeutic cloning?


  a type of cloning - an embryo could be made to have the same genetic information as the patient so the stem cells would also have the same information therefore reducing the risk of the body rejecting them
• what are the risks of using stem cells in medicine?

  stem cells could become contaminated in the lab by other microorganisms which could be passed onto the patient making them sicker.
• why might some people be against stem cell research?

  • people believe that human embryos shouldn't be used for experiments but others think that curing existing patients is more important than the rights of embryos
  • in some countries it is banned - it is allowed in the UK as long as it follows strict guidelines
• how can stem cells produce identical plants?

  • can be used to produce clones of whole plants quickly and cheaply
  • can be used to grow more plants of rare species to prevent them being wiped out
  • can be used to grow crops of identical plants that have desired features for farmers - disease resistant