Module 2 - Foundations in Biology

• What is a light microscope used for?


  Observing living and dead specimins
• What are the pros and cons of a light microscope?

  Pros: Cheap, portable, easy to use, can study living specimens. Cons: Limited magnification, poor resolution.
• What is a laser scanning confocal microscope used for?

  Creating a high resolution, high contrast image, at different depths of the specimen.
• What is a transmission electron microscope be used for?

  Observing the internal ultrastructure of cells under high magnification and resolution
• What is a scanning electron microscope used for?


  Viewing the surface of objets under high magnification and resolution
• What are the pros and cons of an electron microscope?

  Pros: Very high magnification and excellent resolution. Cons: specimen has to be dead, very expensive, very large, needs great skill and training to use.
• What is the difference between a transmission and an scanning electron microscope?

  TEM sends a beam of electrons through the specimen, the SEM bounces electrons off the surface.
• What is the difference between light and electron microscopes?

  Light uses lenses to focus a beam of light. Electron uses a beam of electrons, focused by magnets.
• What is an eye piece graticule?

  A small ruler fitted to a light microscope's eyepiece. It must be calibrated using a stage micrometer before being used to measure specimens.
• What is a stage micrometer?

  A millimeter long ruler etched onto a slide. it has 100 divisions, each of 0.01mm or 10 micrometers. It is used to calibrate the eyepiece graticule
• Why do we stain specimens?

  To provide more contrast, and make it easier to distinguish certain parts.
• What is differential staining?


  Using a stain to distinguish between either 2 different orgaisms, or between organelles of a specimin due to preferential absorbtion of stain.
• What is the formula to calculate magnification?

  Magnification = Image size / Actual size
• What is the formula to calculate actual object size?

  Actual size = Image size / Magnification
• How do we work out image size?


  Use a ruler and measure the image.
• What is magnification?


  A measure of how much larger the image of a specimen looks under the microscope
• What is resolution?

  The ability to distinguish between to adjacent individual points as separate.
• What are the maximum resolutions of the different microscopes?

  Light: 200nm; SEM: 10nm; TEM: 0.2nm.
• What is the maximum magnification of the different microscopes?

  Light: 1,500X; SEM: 100,000X; TEM: 500,000X.
• What are the main structures of all eukaryotic cells?

  Nucleus; nucleolus; cytoplasm; cytoskeleton; plasma membrane;mitochondria; Golgi apparatus; smooth endoplasmic reticulum; rough endoplasmic reticulum; ribosomes.
• What is the structure and function of the nucleus?

  Surrounded by a double membrane (the nuclear envelope). Contains chromatin (DNA wound around histones). Stores the human genome, controls the cell by providing instructions for protein synthesis.
• What is the structure and function of the nucleolus?

  Made of RNA, produces ribosomes.
• What is the structure and function of the nuclear envelope?

  A double membrane embeded with channel proteins forming pores. Separates the nucleus from the rest of the cell. Pores allow ribosomes and mRNA to leave the nucleus.
• What is the structure and function of the rough endoplasmic reticulum (RER)?


  A system of fluid filled membranes studded with ribosomes. Continuous with the nuclear membrane. Large surface area formed by folding, enables lots of protein synthesis. Proteins pinched off in vesicles transported to the Golgi apparatus.
• What is the structure and function of the smooth endoplasmic reticulum (SER)?

  A system of fluid filled membranes. No ribosomes. Contain enzymes for cholesterol, lipid and phospholipid synthesis.
• What is the structure and function of the Golgi apparatus?

  A stack of flattened membrane bound sacs. Vesicles from the RER join at the cis face. Here they are modified, by adding sugar to make glycoproteins, adding lipids to form glycolipids. Folding proteins into their 3D shape. Modified proteins are pinched off from the trans face into transport vesicles.
• What is the structure and function of the ribosomes?

  2 subunits, large and small. Made of rRNA . Proteins synthesised here.
• What is the structure and function of the mitochondria?

  Double membrane bound. Inner membrane folded into cristae within a fluid filled matrix. Contain own DNA and 70s ribosomes. Site of aerobic respiration.
• What is the structure and function of the lysosomes?

  Membrane bound sacs containing hydrolytic (digestive) enzymes. break down old organelles and foreign matter for reuse.
• What is the structure and function of the chloroplasts?

  Double membrane bound. Inner membrane forms flat discs filled with chlorophyll called thylakoids, in stacks called granum. These are surrounded by a fluid matrix called the stroma. Contain own DNA and 70s ribosomes. Site of photosynthesis.
• What is the structure and function of the plasma membrane?

  Phospholipid bilayer, cholesterol, proteins, glycoproteins, glycolipids. Separates cell contents from external environment. Controls what enters and leaves the cell. Identifies cell as self. Acts as a receptor for various chemicals. site of chemical reactions.
• What is the structure and function of the centrioles?

  Present in animals only. Two bundles of microtubules at right angles. Used as an anchor point to separate chromosomes during cell division. Form the basis of cilia.
• What is the structure and function of the cell wall?

  Present in plants and fungi only. Bundles of cellulose fibres in plants. Chitin in fungi. Provides support and strength, maintaining the cell's shape. prevents the cell from bursting when turgid. Permeable to allow solutions through.
• What is the structure and function of the flagella?

  9 pairs of microtubules surround 2 lone microtubules. A membrane covers the whole thing. Used for moving unicellular organisms around.
• What is the structure and function of the cillia?

  9 pairs of microtubules surround 2 lone microtubules. A membrane covers the whole thing. Present in great numbers. Move together in a wafting pattern to move single celled organisms. When present on tissues waft to move fluids such as mucus.
• Which structures are involved in the production of proteins?

  Nucleus; RER; transport vesicle; Golgi apparatus
• What is the structure and function of the cytoskeleton?

  Microfilaments made of actin - allow cell movement and cytokinesis. Microtubules made of tubulinsscaffold like structures to give cell shape. Intermediate fibres give mechanical strength, maintaining integrity.
• What do prokaryotic and eukaryotic cells have in common?

  Plasma membrane; cytoplasm; ribosomes; DNa and RNA
• What is different between prokaryotic and eukaryotic cells?

  Prokaryotes have no: Nucleus; centrioles; membrane bound organelles (mitochondria, chloroplast, RER, SER, Golgi apparatus). Prokaryotes also have: peptidoglycan cell wall; smaller ribosomes; naked loop of DNA; plasmids.
• How do prokaryotes divide?

  Binary fission