2.1 Cell Structure

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a) What is the use of microscopes and what are the 3 different types of microscopes used?

Magnify small cells and organisms for observation

  • Light

  • Scanning electron

  • Transmission

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a) What type of observations are made with the 3 types of microscopes?

Light:

  • whole cells and tissues

Transmission:

  • organelles within the cell

Scanning:

  • objects at certain depth within cell

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a) What is the differences between the three microscopes?

Light:

  • View live specimen

  • Magnification: x1500

  • Resolution: 200nm

  • 2D

Transmission:

  • View dead specimen

  • Magnification: x100,000

  • Resolution: 0.2 nm

  • 2D

  • In black and white

Scanning;

  • View dead specimen

  • Magnification: x500,000

  • Resolution: 3-10nm

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What is the name of another microscope and its features?

Laser confocal microscope:

  • View live specimen

  • Coloured

  • 3D

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b) How do you prepare microscope slides?

  1. Use a sharp blade

  2. Cut thin slices of tissue, then pick the thinnest slice

  3. Place on the microscope slide

  4. Stain before placing cover slip over the specimen about to view

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What piece of equipment do you use when measuring a cell under a microscope?

Eyepiece graticule:

  1. Calibrate graticule to the stage micrometre

  2. Work out the number of division per graticule

  3. Measure the diameter of cell 3 times and create an average

  4. Use the calibrated units to calculate diameter

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What are the four types of mounts/ preparations?

Wet mount:

  • Specimen suspended in liquid like water and cover slip placed at angle

Dry Mount:

  • Cover slip placed directly

  • Used for plant cells

Squash Slide:

  • Specimen squashed between two slides

  • Used for root hair cells

Smear mount:

  • Using a drop of sterilised water or saline water

  • Used for blood cells or cheek

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How do you use different objective lens to focus specimen?

  • By switching it from thee lowest lens to the highest

  • using the fine focus for a clearer image

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Why is it crucial to place coverslip at an angle?

To avoid air bubbles

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c) What is the use of staining ?

  • To increase contrast

  • Organelles can be views easily and better

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Name some stains and what organelles you can view?

Sudan III - Lipids

Acetic Erisin - Chromosomes

Iodine - Starch

Mythlene Blue - Cytoplasm

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e) What is the magnification formula and how can you change it?

Magnification= Image size / Actual object

Image size = magnification * actual object

Actual objects = Image size / Magnification

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f)What is the definition of magnification and resolution?

Magnification: is how many times larger the image size is compared to the actual size

Resolution: ability to distinguish two different points

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g) What are the features of the eukaryotic cells and function?

Both cells (Animal and Plant):

Nucleolus:

  • Contains genetic material

Nuclear envelope:

  • Contain nuclear pores - help large molecules pass through

  • Double membrane

RER:

  • Contains ribosomes

  • Specifically the membrane holds ribosomes and allows mRNA to fuse with ribosomes

Ribosomes:

  • Site of protein synthesis

  • No membrane

SER:

  • Site of where lipids are formed

Golgi Apparatus:

  • Stores, modifies and packages complex molecules which leave and enter in vesicles

  • Vesicles move using microtubles

Lysosomes:

  • Contain digestive enzymes to breakdown waste products

Mitochondria:

  • Site of aerobic respiration - produces ATP

  • Cytoplasm = matrix

  • Inner layer of membrane = cristae

Plasma Membrane:

  • Controls what enters and leaves cell

Plants:

Chloroplasts:

  • Photosynthesis occurs in thylakoids specifically where energy and enzymes are kept

  • Stacks of thylakoid = grana

Cell Membrane:

  • Made of cellouse

Permanent Vacuole:

  • Contains tonoplast which is a membrane filled with cell sap

Cell Wall:

  • Pores = plasmodesmata

  • Connects two cells together

Amylose:

  • Contains starch grains

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What are the main differences between Prokaryotic and Eukaryotic?

  • Unicellular

  • No membrane bound organelles

  • Contains DNA plasmid rings instead of nucleus or DNA enclosed in nucleus

  • Contains flagella

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i) What is the interactions between cells to create protein?

  1. mRNA copies instructions from the gene within the nucleus - Transciption

  2. Leaves the nucleus through the pores within the nuclear envelope - Transalation

  3. Travels to the RER and attaches to the ribosome, ribosomes reads instructions - makes proteins

  4. Protein released in a vesicle sent to golgi where it is modified, packaged and stored ready to be released

  5. Pinched off and sent to cell surface membrane

  6. Vesicle fuses with CSM and opens up to release to the body

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j) What is the importance of the cytoskeleton

  • Provides mechanical stability

  • Allows cell movement

  • Holds organelles in place

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