Basic Components

• Properties of a light microscope.

  • Poor resolution due to long light wavelength.
  • Living samples can be used as light microscopes don’t operate under a vacuum.
  • A colour image can be produced due to selective absorption of light wavelengths.
• Properties of transmission electron microscopes (TEM).

  • High magnification.
  • High resolution due to electrons having shorter wavelength than visible light.
  • 2D image is produced as electrons pass through the specimen; so it must be thin.
  • Detectors detect charge not light and so produce a black and white image.
  • Some parts absorb electrons, making them appear darker.
• Properties of scanning electron microscope (SEM).

  • High magnification.
  • High resolution due to electrons having a shorter wavelength than visible light.
  • Electrons bounce off the surface and are scattered in different directions, forming a 3D image.
  • Detectors detect charge not light and so form a black and white image.
• Properties of laser scanning confocal microscopes (LSCM).

  • High resolution due to highly focused laser light that scans only a specific plane.
  • This laser light scans the object to create a 3D image that is reconstructed with a computer.
  • The specimen is usually tagged with a fluorescent dye so that it can be illuminated and picked up by the detector.
• What is magnification?

  How many times larger an image is compared to an object.
• What is resolution?

  The minimum distance between two objects, in which they can still be view as separate entities.
• Difference between light and electron microscope?

  The resolution of a light microscope is determined by light wavelength, while the resolution of electrons microscopes is determined by the wavelength of an electron beam.
• How do electrons microscopes work?

  An electromagnet is used to focus a beam of negatively charged electrons on the specimen, forming an image; air absorbs electrons so the specimen must be in a vacuum.
• What is the nucleus?

  A membrane bound organelle found in eukaryotic cells, containing the cells genetic material in the form of chromatin. It plays a key role in gene expression, DNA replication, transcription, and ribosome synthesis.
• What is the nuclear envelope?

  Double membrane structure that surrounds the nucleus and separates it from the cytoplasm, with fluid between the two layers; protecting the genetic material from the chemical reactions that occur in the cytoplasm.
• What are nuclear pores?

  Protein complexes in the nuclear envelope with channels through their centre that allow for the transport of molecules in and out of the nucleus.
• What is the nucleolus?

  The nucleolus is a small, sphere found within the nucleus of a cell, responsible for producing ribosomes and the site of rRNA production.
• What is nuclear-plasm?

  Granular, jelly material inside the nucleus of a cell, present between the two layers of the nuclear envelope.
• What are chromosomes?

  Chromosomes are thread-like structures made of DNA and proteins that carry genetic information in the form of genes.
• What are flagella?

  Whip-like appendages used for movement, and sometimes as a sensory organelle for chemical stimuli.
• What are cilia?

  Microscopic hair-like structures found on the surface of cells. They can be mobile which sweep substances, or stationary which are vital in sensory organs such as the nose.
• What are centrioles?

  Organelles involved in the production of spindle fibres and the organisation of chromosomes in cell division; they are made of microtubules and occur in pairs to form centrosome.
• What is the cytoskeleton?

  A network of protein filaments that provides structural support, maintains stability, and helps with cell movement; many organelles are bound to the cytoskeleton.
• What are microfilaments?


  Thin, thread-like structures made of actin protein subunits that forms a polymer, facilitating cell movement, shape stability, and mechanical strength.
• What are microtubules?

  Cytoskeletal structures made of tubin protein subunits that form scaffold structure to provide strength and support, form a track that motor proteins (dynein and kinesin) transport organelles along through cytoplasm, form spindle in division, and make up motile intra-cellular structures (cilia, centriole, undulipodia).
• What are intermediate filaments?

  Structural proteins that act as a mechanical stress absorber, anchor the nucleus, and extend between cell junctions to enable cell signalling.
• What is the smooth endoplasmic reticulum?

  A network of membrane-bound tubes and sacs mainly responsible for the synthesis and storage of lipids, steroids, and other molecules throughout the cell; both have folded membranes called cisternae.
• What is the rough endoplasmic reticulum?


  Network of membrane-bound tubes and sacs involved in protein synthesis, folding, and modification; they have folded membranes called cisternae, with ribosomes attached to the surface.
• What is the golgi apparatus?

  Organelle consisting of folded membrane cisternae, that are involved in processing, packaging, and distributing proteins and lipids in the cell. Once processed, they are packaged into membrane-bound secretory vesicles, which are sent to the cell surface where they fuse with the membrane and release their contents.
• What are vesicles?

  Small membrane-bound sacs that transport and store materials within cells.
• What are lysosomes?

  Organelles that contain digestive enzymes that break down waste materials and cellular debris; releasing enzymes outside of cell to destroy material (exocytosis), digesting worn out organelles for material reuse, and breaking down dead cells (autolysis).
• What is exocytosis and endocytosis?

  Vesicles fuse with the membrane and their contents are deposited into the extracellular or intracellular environment.
• What are mitochondria?

  Organelles responsible for ATP production, the site of aerobic respiration, and contain DNA code for the enzymes needed in respiration. It has a double membrane structure, with an inner cristae membrane. Its fluid centre is called the mitochondrial matrix and it contains a loop of mitochondrial DNA.
• What are ribosomes?

  Small cellular organelles responsible for protein synthesis, made up of two sub units of protein and rRNA; large ribosomes (80s) are found in eukaryotes, and small ribosomes (70s) are found in prokaryotes, mitochondria, and chloroplasts.
• What are chloroplasts?

  Organelles that are the site of photosynthesis; they are surrounded by a double membrane, contain thylakoids, and fluid filled stroma which contain enzymes for photosynthesis.
• What are thylakoids?

  Membrane-bound compartments in chloroplasts where photosynthesis takes place, consisting of folded membranes embedded with pigment.
• What is the cell wall?

  A rigid layer outside the cell membrane that provides support and protection. In plants it is made of microfibrils of the polymer cellulose, while in fungi it is made of chitin, a polysaccharide containing nitrogen.
• What is the plasma membrane?

  The outer boundary of a cell that controls the movement of substances in and out of the cell. It consists of a phospholipid bilayer, that has molecules embedded within and on the surface of it; such as proteins, cholesterol, and carbohydrates.
• Protein production and secretion.

  1. Polypeptide chains are synthesised on RER by ribosomes on outside.
  2. These chains move to the cisternae in the in RER and are packaged into vesicles to be sent to the golgi apparatus via the cytoskeleton.
  3. Here the proteins are modified and packaged again into vesicles.
  4. The secretory vesicles carry proteins to cell surface membrane, where it fuses and releases the protein by exotysosis.
• What are prokaryote?

  • Small organisms with no membrane bound organelles.
  • Contains smaller (70s) ribosomes.
  • Contains circular DNA in the cytosol (cell membrane fluid), and plasmid, a small DNA loop which carry few genes in various numbers.
  • Have a slimy layer of protein called a capsule, preventing bacteria drying out, and protects it against host immune system.
  • Has a flagella, a rotating tail that helps movement.
  • Has a peptidoglycan (murein) cell wall.
• What are eukaryote?

  • Larger organisms with membrane bound organelles.
  • Contains larger (80s) ribosomes.
  • All DNA is contained in the nucleus.
• What are ligands?


  Molecules or ions that bind to a central metal atom or ion.