Cell biology

• What are eukaryotes and what do they contain?

  Cells were the DNA is enclosed in a nucleus

  Cell membrane, cytoplasm, nucleus
• What are prokaryotes


  DNA is not enclosed in a nucleus - bacterial cells
• Where is DNA stored in prokaryotes and what do they contain

  Single loop of DNA and plasmids

  Also contain cell membrane, cell wall and cytoplasm
• mm to um?

  um to nm?

  x1000
• Nucleus function


  Contains DNA
• Cytoplasm function


  Where chemical reactions take place
• Cell membrane function?


  Controls what can enter and leave the cell
• Mitochondria function


  Where aerobic respiration takes place
• Ribosomes function


  Protein synthesis
• 3 differences between plant cell and animal cells

  Plant cells contain vacuoles, cell walls and chloroplasts
• Chloroplast function


  Contains chlorophyll which absorbs light energy for photosynthesis
• Cell wall function


  Made from cellulose and strengthens the cell
• Vacuole


  Contains cell sap and helps cell keep its shape
• Specialised cell


  A cell that is adapted for a certain specific function (job). - undergoes differentiation
• Sperm cell - adaptations and job

  To join with the ovum

  Contain half the DNA

  Have a long tail to swim and is streamlined

  Contains lots of mitochondria

  Contain enzymes so they can digest through the outer layer of the ovum
• Nerve cells - adaptations and job

  Send electrical impulses around the body

  Contain a long axon to carry impulses to one part of the body to another

  Axon contains myelin to speed up transmission of nerve impulses

  Dendrites to give bigger SA
• Muscles cells and adaptations

  They contract

  Contain protein fibres

  Have lots of mitochondria so they have energy to contract
• Root hair cell adaptations

  Root hair increases surface area

  Dont contain chloroplasts as they are underground
• Xylem cells - job and adaptations

  Carry water and minerals from roots to leaves

  Have thick walls containing lignin to provide support

  End walls are broken down so water can flow easily

  No internal structures - easy to flow
• Phloem cells - job and adaptations

  Carry dissolved sugars up and down the plant

  Have sieve plates so sugars can pass

  Connected to companion cells which provide the cell with energy
• How to prepare a slide?

  1. Pipette a drop of water onto slide

  2. Use tweezers to place a thin section of specimen on top of droplet.

  3. Add a drop of stain so internal structures are easier to see

  4. Add a cover slip - remove bubbles
• Microscope practical steps


  Place the slide on the stage and use the clips to hold it in place

  Use the lowest power objective lens

  Turn the coarse focusing lens until the objective lens almost touches the slide

  Look down through the eyepiece and turn the coarse focusing knob until the cell comes into focus

  Use the fine focusing dial to bring cells into focus
• Total magnification? (2)


  eyepiece lens x objective lens

  image size/actual size
• How does bacteria divide and how often is it carried out

  binary fission

  Once every 20 mins as long there is enough nutrients and the temp is suitable
• Number of bacteria =

  2 to the power of number of rounds of division
• Culturing Microorganisms


  Sterilise petri dishes, broth and agar to get ride of unwanted pathogens

  Sterilise inoculating loop with bunsen burner

  Transfer bacteria onto the plate

  Attach the lid with tape to stop the lid from falling and stop pathogens from entering

  Place it upside in an incubator so stop moisture from dripping down onto the bacteria

  Leave it for few days at 25 degrees celcius
• Effect of antibiotics on bacterial growth

  Clean bench with disinfectant to kill pathogens

  Sterilise inoculating loop with bunsen burner

  Open a sterile agar gel plate near a bunsen burner plate

  Use the loop to spread bacteria evenly on the plate

  Place sterile filter paper containing antibiotic onto the plate

  Incubate at 25 degress
• Zone of inhibition equation

  pi r squared
• What is mitosis


  Cell division that generates new cells for growth and repair. The division of one cell into two genetically identical daughter cells
• First stage of mitosis (interphase)

  The DNA duplicates

  Cell grows and copies mitochondria and ribosomes
• Second stage of mitosis

  One set of chromosomes is pulled to each end of the cell and the nucleus divides
• Third stage of mitosis

  Cytokinesis - cytoplasm and cell membrane divide forming two identical cells
• What is mitosis used for

  growth, repair, asexual reproduction
• Stem Cells


  undifferentiated cells that have the potential to become any type of cells
• Where they are found in plants

  Meristems
• Where they are found in adults

  Bone marrow
• What stem cells can be used to treat

  Used to treat leukemia

  The existing bone marrow is destroyed via radiation

  They then receive a transplant

  These divide and form new bone marrow
• Problems with BM transplants

  Donor must be compatible with patient

  Viruses could be passed
• Therapeutic cloning


  An embryo is prdouced with the same genes as the patient
• How does T cloning work

  Stem cells can be transplanted into patient without being rejected

  Once inside the stem cells differentiate to replace non working cells