Cell structure

• Nucleus contains nucleolus nucleoplasm and nucleur envelope

  Nucleoplasm contains chromatin for chromosomes

  Nucleur envelope Contains pores which allows mrna to leave the nucleus and nucleotides to enter
• Mitochondria is where aerobic respiration takes place, it has an outer membrane and inner membrane with cristae inside.
• Ribosome are made up of RNA and protein molecules they make proteins from amino acids
• Lysosomes contain digestive enzymes that break down waste material and old organelles
• Golgi apparatus modifies and packages proteins into vesicles ready to be transported out of cell or used by cell.
• Smooth endoplasmic reticulum synthesises steroids and lipids

  Rough endoplasmic reticulum makes ribosomal dna
• Vacuole contains storage site
• Matrix contains circular dna and 70S ribosomes

  In the mitochondria

  Double membrane forms to form cristae
• Inner membrane space contains a high concentration of hydrogen ions
• Thylakoid sacs contain chlorophyll pigments which absorb light energy
• In the chloroplasts the double membrane folds to form thylakoids
• An example of specialisation is the epethelial cells in the small intestine, they have microvili which have a large surface area for absorption of molecules

  Lots of mitochondria for aerobic respiration and atp
• A bacterial cell contains a cell wall make of more in 70S ribosomes a capsule, pilus a plasmid and a flagella
• key differences between a prokaryotic and eukaryotic cell:

  eukaryotes have

  Cell wall make of cellulose 80S ribosomes

  membrane bound organelles

  Dna is enclosed within the nucleus
• Prokaryotes have

  70S ribosomes

  Cell wall made of murein

  No membrane bound organelles

  Dna is bundled up
• Viruses are acellular, they have no cell surface membrane, no organelles and can’t respire and no metabolic reactions

  They enter living cells and multiply with the assistance of host cells
• All viruses have:

  Dna or rna

  A capsid which protects the genetic material

  Attachment protein which are complimentary to and bind to receptors in its specific host cell (they act like enzymes)
• Magnification is how much bigger the image is compared to the real structure
• Resolution is the ability to see two points as two points
• The electron microscope uses electrons instead of light waves to form an image.
• Electron microscopes use electromagnetic lenses to focus the beam onto the specimen and then onto a screen where the image is formed.
• Transmission Electron Microscope (TEM) - Uses high energy electrons that pass through the sample and create an image on a fluorescent screen. It has higher resolution than SEMs but lower magnification.
• Sem: scanning electron microscope

  Resolution isn’t as high as tem but higher than light microscope and it produces a 3D image but it’s only back and white
• Light microscope uses lenses to focus a beam of light and it has a low resolution but it can view live specimens and can see colours
• Stages of cell fractionation:

  Homogenisaction

  Grind in: cold so it reduces enzyme activity

  Isotonic so it prevents organelles from shrinking/bursting

  Buffer so it maintains ph and prevents denaturing

  Filtration: to filter out large debris but the organelles pass through

  Centrifugation: first low speed spin to give a pellet of the heaviest organelles, nucleus

  Then spin at high speed to get rid of the chloroplasts etc
• Mitosis

  Prophase- chromosomes condense from chromatin and become visible as 2 chjoined at the centromere

  The nucleur envelope and nucleolus disappear

  Metaphase- chromosomes line up at equator of the mitotic spindle attached to spindle by centromere

  Anaphase-chromosomes split as centromere divide as spindle fibres contracts, sister chromatids separate and are pulled to opposite poles of the cell by centromere first

  Telophase-chromosomes elongate and uncoil and then nuclear envelope reappear as two new nuclei are formed