Cells

• What happens when the proteins in the Golgi Apparatus have been modified and packaged?

  Vesicles containing the final protein are pinched off from the maturing face.These vesicles either transport the protein around the cell or fuse with the cell surface membrane and release their contents outside the cell.

  
• What protein modifications take place in the Golgi Apparatus?

  1. Carbohydrate is added to form glycoproteins.2. Lipid is added to form lipoproteins3. Prosthetic groups are added4. Polypeptides are joined to form quaternary structures.5. The protein is packaged.
• Golgi Apparatus

  A series of flattened cisternae.Small vesicles enter and leave the Golgi Apparatus.Vesicles containing new protein pinch off the RER and coalesce to form the forming face of the Golgi Apparatus.

  
• Ribosomes

  Very small organelles, 30nm in diameter.Free in cytoplasm or attached to ERMade of a small and large subunit and of protein and rRNA.Can occur in groups called polyribosomes and these are hot spots for protein synthesis.

  
• SER

  Synthesises lipids e.g phospholipids.Detoxifies drugs and poisons.

  
• RER

  Originates from the nuclear envelopeAnchors the ribosomes where protein is made and then distributes the proteins through the netwotk of cisternae.Primary structure of a protein is made on the RER and the secondary and tertiary structures develop within the cisternae.Common in protein secreting cells.

  
• Endoplasmic Reticulum


  A membrane system throughout the cytoplasm.made of 3D membarne bound sacs called cisternae.Rough ER contains ribosomes and Smooth ER does not.

  
• How does the DNA code get from the nucleus to the ribosomes where protein is made.

  The code is transcribed on to mRNA which leaves the nucleus through nuclear pores in the nuclear envelope (double membrane)

  
• Function of nucleus


  Control centre of the cell.DNA codes for the making of proteins in the cytoplasm.
• Nucleolus

  Darker region in the nucleusContains the DNA that codes for ribosomal RNA.Makes ribosomes

  
• Two types of chromatin

  Heterochromatin, dark and densely packed.Euchromatin, lighter and loosely packed.
• Nucleus

  Largest organelleBetween 10-25µmContains DNA in chromosomesHistone proteins support and protect the DNAThe DNA and protein exist as a substance known as chromatin.Contains a nucleolus

  
• Eukaryotic cell features

  All have a nucleus, cell surface membrane, cytoplasm and organelles.
• Ultrastructure


  The detail of a cell when viewed through an electron microscope.
• Scanning Electron Microscope (SEM)


  Electrons are reflected off the surface of the specimen.Produces 3D surface features.

  
• Transmission Electron Microscope (TEM)

  Electrons pass through a very thin specimen.Images show internal slices of cells.

  
• Two types of electron microscope


  1. Transmission electron microscope2. Scanning electron microscope
• Light Microscope

  1. Specimens to be viewed can be living (EM uses a vacuum)2. There are none of the artefacts produced during the preparation of specimens for the electron microscope.3. Preparing specimens for viewing is not complicated.

  
• Advantages of the electron microscope

  Can see complex cell structures

  
• Magnification and resolving power of a light (school) microscope?

  Resolving power is 0.2µmMagnification is up to a few thousand
• Why do electron microscopes have such a high resolving power?

  This is because the electrom microscope uses electrons which have a much shorter wavelength than light.
• What is resolving power/resolution?


  The ability to see two adjacent points as distinct entities following magnification.
• Electron Microscope

  Uses electrons rather than light to produce images.Electron microscopes have a resolving power of 0.1nmHas a magnification in excess of 1 million.

  
• How many µm are in 1 mm?

  1000
• How many nanometres are in a micrometre?

  1000
• What is the standard unit for measuring cells?

  micrometre µm
• How do animal cells and plant cells differ under the light microscope?

  Animal cells are irregular and plant cells are more regular.Plant cells contain a cell wall, vacuole and may be rich in chloroplasts.

  
• What is a cell?


  The basic unit of living organisms

  
• How do prokaryotes and eukaryotes differ in microtubules?

  P.. not presentE.. spindle fibres and other microtubules present.
• How do prokaryotes and eukaryotes differ in plasmids?

  P..usually presentE.. not present
• How do prokaryotes and eukaryotes differ in cell walls?

  P..peptidoglycan cell wallsE.. Cellulose cell walls in plants, chitin cell walls in fungi and no cell walls in animals.
• How do prokaryotes and eukaryotes differ in Internal structure?

  P.. no complex organellesE.. many complex membrane bound organelles
• How do prokaryotes and eukaryotes differ with regards to ribosomes?

  P.. Small 70S E.. Large 80S
• How do prokaryotes and eukaryotes differ in DNA organisation

  P.. Circular and without histone proteinsE.. Linear and in chromosomes with histone proteins
• How do prokaryotes and eukaryotes differ in site of DNA

  P.. free in cytoplasmE.. in membrane bound nucleus
• How do prokaryotes and eukaryotes differ in size?

  Prokaryotes are usually less than 5um and eukaryotes are between 10-200um
• 8 Ways that prokaryotes and eukaryotes differ

  1. Size2. Site of DNA3. DNA Organization4. Ribosomes5. Internal structure6. Cell Walls7. Plasmids8. Microtubules
• Draw and label a bacteria

  
• Prokaryotic cells


  Do not have a nucleus or membrane bound organelles e.g bacteria
• Unique features of fungi

  Chitin cell wallMultinucleateOften exist as long elongated threads called hyphae.