Chapter 2- cells

• Describe the gram staining technique

  Separates bacteria into two groups, gram positive and negative

  • Apply crystal violet to specimen
  • Then iodine (fixes the dye)
  • Wash dye with alcohol
  • Gram positive- retain crystal violet and appear blue or purple
  • Gram negative- lose the stain, then counter stained with safranin and will then appear red
• What is the acid fast technique used for?

  Identifying different species of mycobacterium from other bacteria. Lipid solvent used.
• Five differences between light and electron microscope

  • Light inexpensive to buy and operate, elec is not
  • Light requires no vaccum, elec does
  • Light, specimen can be living or dead, elec = dead
  • Higher resolution/magnification in elec than light
  • Light, natural colour of specimen, elec = black and white
• Name 2 positively and negatively charged dyes. What are they?

  Positively charged

  • Crystal violet
  • Methylene blue

  Attracted to negatively charged materials in the cytoplasm and stain them

  Negatively charged

  • Nigrosin
  • Congo red

  Repelled by negatively charged cytosol. Stay outside cells, leaving cells unstained so they stand out against unstained background (negative stain technique)
• what is differential staining? Give two examples

  • Distinguishes between two types of organisms that would otherwise be hard to identify.

  Gram stain- separates bacteria into gram positive and negative

  Gram positive:

  1. Crystal violet is applied
  2. Iodine fixes the dye
  3. Slide washed with alcohol
  4. Retain violet stain and appear blue/purple

  Gram negative back lose the stain (thinner cell walls), then they are stained with safranin (counterstain). Bacteria then appear red

  Acid fast- differentiates species of mycobacterium from each other
• Describe a laser scanning confocal microscope

  • High light intensity used to illuminate specimen treated with fluorescent dye
  • Produces coloured images
  • 3D
  • Very high resolution
  • Non invasive
• Describe mitochondria and it’s functions

  • Site of final stages of cellular respiration
  • Production of ATP allows it to release energy
  • Inner membrane folded to form Cristae
  • Fluid interior is matrix
  • Cristae contains enzymes used in aerobic respiration
  • Has its own DNA and can reproduce themselves
• Describe the role of vesicles

  Transport substances within and outside the cell
• Describe the role of lysosomes

  • Contain hydrolytic enzymes
  • Break down waste material in cells including old organelles
  • Break down pathogens
  • Responsible for apoptosis (cell death)
• Describe the roles of the cytoskeleton

  • Microfilaments- responsible for cell movement and contraction during cytokinesis
  • Microtubules- determine shape of cell, act as tracts for organelle movement. Form spindle fibres which segregate chromosomes during cell division
  • Intermediate fibres- provide mechanical strength and help maintain cells integrity
• describe the role of centrioles

  2 associates centrioles form centrisms, involved in assembly and organisation of spindle fibres during cell division
• Describe the role of flagella

  Enable cell motility
• Describe the role of cilia

  • Can be mobile or stationary
  • Stationary cilia have important function in sensory organs
  • Mobile cilia beat in rythmic manner, causing fluids (eg mucus) to move
• Describe the role of the smooth ER

  Synthesises, stores and transports lipids and carbs
• Describe the role of the rough ER

  Ribosomes bound to surface, responsible for synthesis and transport of proteins
• What are bacterial cell walls made of?

  Peptidoglycan