The Structure of Cells and Microscopy

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  • Created by: Curlot
  • Created on: 22-09-14 17:26

Seperating Cells from their Organelles

  • Cell tissue is cut up and kept in isotonic solution.
  • The tissue is then broken down in a homogeniser to release the organelles
  • It is spun in an ultracentrifugue
  • Heaviest sediemnt falls the bottom and the supernantant is removed
  • Process is repeated for Mitochondria, Lysosomes and Ribosomes.
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Lysosomes

These are formed when Vesicles by Golgi contain enzymes like protease and lipease. They isolate potentially harmful enzymes from the cell. Functions are...

  • Break down material from Phagocytic (White Blood Cells)
  • Releas enzymes (Exocytosis)
  • Digest worn out organelles so useful chemials are made.
  • Complete break down of dead cells
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Ribosomes

Small cytoplasmic granules in all cells, they are either in cytoplasm or with Rough Endoplasmic Reticulum. 80s type. They have 2 subunits each containing ribosomal DNA and protein up to 25% of a cell and are important for protein synthesis.

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Endoplasmic Reticulum

3D system of sheet like membranes in the cytoplasm. It's continuous with the outer membrane.

Rough ER -> have ribosomes on the outer have large surface area for gylcoprotein & protein synthesis.

Smooth ER -> no ribosomes, tubular in appearance. They synthesise, store and transport lipids and carbohydrates.

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Golgi Apparatus

Consists of a stack of membrane of flattened stacks or cisternae. Proteins & lipids produced by ER are passed through and modified they

  • add carbohydrates to proteins = glycoprotein
  • produce secretory enzymes
  • secrete carbohydrates
  • transport modify & store lipids
  • from lysosomes
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Nucleus of a Eukaryotic Cell

The Nucleus contains the DNA and controls substances in and out of the cell

  • Envelope - double membrane that surrounds the nucleus
  • Pores- aloowspassage of large molecules
  • Nucleoplam - Jelly -like material bulks out the cell
  • Chrmatin - DNA found within the nucleoplam
  • Nucleous - Sphereical body within
  • Nucleoplasm - Manufactures ribsosomes
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Ribosomes

Rod Shaped between 1 and 10 micrometre in length made from...

  • A double membrane that surrounds and controls in and out.
  • Cristae are sehlf like extensions increasing the surface area for attaching enzymes that for respiration
  • Matrix contain protein, lipids and tiny amounts of DNA controlling the production of proteins
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KeyWords

Filtrate -> the solution that does not contain cell debris or broken cells

Homogenate -> a liquid that containsall cell contents due to it being broken

Isotonic -> solutions that posses the same amont of water as the cell

Organelle -> structure found within the cytoplasm of a cell

Sediment -> the heavy cell organisms found at the bottom of the tube

Supernatant -> the liquid left when suspended particles have been sperated .

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The Scanning Electron Miroscope

The SEM directs a beam of electrons onto the surface of a speciemen from above. A 3D image is produced as the electrons are scattered.

Advantages

  • 10x better reolving power than a light microscope
  • Any thickness specimen can be used
  • False colour ca be added

Limitations

  • The system is a vacuum, no living organisms can be looked at
  • The image is black and white
  • Lower resolution than TEM
  • Only a picture of the image is made
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The ransmission Electron Microscope

THe TEM consists of an electron gun that produces a beam of electrons it's focused by a condenser magnet. The beam is passed through. If the specimen image is dark the specimen is thick. It can be imaged by a photomicrograph.

Advantages.

  • Have a higher resolution than SEM
  • Short wavelength

Limitations

  • The system is a vacuum and cannot be used to look at living speciemens
  • The specimen has to be thin
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Magnifiation

The Magnification Equations.

Magnification = Image of specimen / actual object size.

Step 1

Write out the formula

Step 2

Gather the measurements

Step 3

Convert to m

Step 4

Do the Maths   

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