Cell Structure

• resolution = the ability to distinguish between two points which are close together.
• magnification = how many times bigger the image of the specimen is compared to its actual real-life size.
• Why do light microscopes have poor resolution ?

  Due to the long wave length of light.
• Which microscopes can be used to view live specimen ?

  Light microscope and Laser scanning microscope
• What images are formed from a light microscope ?

  • colour
  • 2D
• Name 4 types of slide preparation for light microscopes ?

  • Dry Mount
  • Wet Mount
  • Smear slide
  • Squashed Slide
• When would you need to use a squash slide ?

  To view the chromosomes during mitosis in a root hair cell.
• When would you use a smear slide ?

  To view blood cells in a sample
• What other item is needed to calibrate a graticle?

  Stage Micrometer
• What is the need for staining ?

  It provides contrast to allow scientists to differentiate between otherwise very similar looking organelles and structures.
• Differential staining = using multiple different chemicals to stain different organelles different colours.
• Name two positively charged stains?

  Crystal Violet and methylene blue.
• Name a Negatively charged stain?

  Congo red.
• How do negatively charged stains work?

  The cytosol repels them so they cannot enter cells, hence they stain the background allowing the unstained cells to stand out.
• What does gram staining identify?

  Identify whether a bacteria is gram positive or gram negative
• Why do electron microscopes have high resolution?

  Beams of electrons have a short wavelength
• Disadvantages to electron microscopes ?

  • Expensive and not portable
  • Must be in vacuum
  • specimen must be dead
  • images only in black and white
• Features of Transmission electron microscope?

  • Electrons pass through specimen
  • Higher resolution than SEMs
  • Images 2D
• Features of Scanning electron microscope ?

  • Electrons bounce off specimen
  • 3D images produced
  • lower resolution than TEMs
• What images are produced from Laser scanning microscopes?

  • coloured
  • 2D or 3D
• How are images made from laser scanning microscopes ?

  High light intensity illuminates the specimen which is stained with fluorescent dye.
• Name 3 differences between prokaryotic and eukaryotic cells?

  1. no membrane bound organelles in prokaryotes
  2. smaller ribosomes, prokaryotic = 70s while eukaryotic =80s
  3. Dna not contained within a nucleus in prokaryotes
• What is a plasmid ?

  additional loops of DNA found in prokaryotes
• Name two functions of the capsule ?

  Protects bacteria from drying out and protects bacteria against the hosts immune system.
• How does the flagella work ?

  Rotates to allow bacteria to move.
• What organelles are involved in the production and secretion of proteins ?

  Rough Endoplasmic reticulum, vesicles, golgi apparatus, cytoskeleton and cell surface membrane.
• State the structure and function of plasma membranes ?

  Structure: phospholipid bilayer with other molecules embed within.

  Function:controls the entrance and exist of molecules into cell.
• What is the difference. between plant cell wall and fungal cell wall ?

  Plants are made from cellulose while fungals are made from chitin
• Name two double membrane bound organelles ?

  1. mitochondria
  2. chloroplasts
• Name a non-membrane bound organelle ?

  Ribosomes
• State the structure and function of ribosomes?

  Structure : two subunits of protein and rRNA

  Function: sight of protein synthesis/translation
• How is the mitochondria's structure adapted to its function?

  The mitochondria is an energy generation organelle. It's inner membrane (cristae) is coated in enzymes which catalyse the production of ATP, the cristae has many folds to increase its surface area and hence maximise the amount of ATP produced.

  In addition they have their own DNA and ribosomes to make enzymes needed in ATP production
• What is the space inside the mitochondria called ?

  Matrix
• What are lysosomes ?

  Specialised vesicles that contain powerful digestive enzymes to break down material.
• What is the structure and function of the golgi apparatus ?

  Structure: stack of membrane-bound sacs.

  Function : To process, modify and package proteins
• Why does the golgi's shape keep changing ?

  Vesicles are constantly fused together and pinched off.
• What is a vesicle ?

  A membrane 'bubble' that surrounds a protein.
• The processes of the golgi ?

  1. Receives the protein from ER.
  2. Modifies them using enzymes
  3. Packages the modified proteins into vesicles ready to be transported
  4. Directs them to another location e.g surface of cell ready to be secreted.
• What is the structure and functions of the smooth endoplasmic reticulum?

  Structure: series of flattened membrane-bound sacs called cisternae

  Function: synthesis and storage of lipids
• What is the structure and function of the rough endoplasmic reticulum?

  structure : flattened membrane-bound sacs studded with ribosomes

  function : site of protein synthesis and transports proteins made on ribosomes to the golgi.