Cell structure

• how does a light microscope work?

  1. lenses focus rays of light and magnify the view of a thin slice of specimen
  2. different structure absorb different amounts of wavelength
  3. reflected light is transmitted to the observer via the objective lens and eyepiece
• Describe how a transmission electron microscope (TEM) work?

  1. pass a high energy
• describe how a scanning electron microscope?

  1. focus a beam of electrons onto a specimen surface
  2. reflects on the electrons and hit a collecting devices
• magnification definition 


  factor by which the image is larger than the actual specimen
• resolution definition 


  smallest separation distance at which 2 separate structures can be distinguished from one another
• what is the resolution and magnification of a optical?

  • magnification - x2000
  • resolution - 200nm
• what is the resolution and magnification of a TEM?

  Resolution: 0.5 nm Magnification: x 500,000
• what is the resolution and magnification of an SEM?


  resolution: 3-10 nm

  magnification: x 500,000
• Describe the structure of the nucleus?

  • surrounded by a nuclear envelope
  • nuclear pores allow substance to enter and exit
  • dense nucleolus made of RNA and proteins assembles ribosomes
• function of a nucleus

  • contains DNA coiled around chromatin into chromosomes
  • controls cellular process: gene expression determines specialisation and site of mRNA transcription, mitosis
• describe the structure and function of endoplasmic reticulum?

  Structure: Network of membranes with ribosomes (rough ER) or without ribosomes (smooth ER). Function: Rough ER involved in protein synthesis and transport, smooth ER involved in lipid synthesis and detoxification. (smooth ER) is lipid synthesis
• Describe the structure and function of Golgi apparatus?

  Structure: Flattened membrane-bound sacs (cisternae) stacked on top of each other. Function: Modifies, sorts, and packages proteins and lipids for transport within or outside the cell.
• Describe the structure and function of the ribosomes?
• describe the function and structure of ribosomes?


  Function: Protein synthesis Structure: Made of protein and RNA, composed of large and small subunits
• Describe the relationship between production and secretion of proteins?

  Ribosomes synthesis proteins that are attached to the rough endoplasmic reticulum. The golgi apparatus then modifies for secretion
• Describe the structure of a mitochondrion?

  • surrounded by double membrane
  • folded inner membrane forms cristae (site of the electron transport chain)
  • Fluid matrix = contains mitochondrial DNA, respiratory enzyme, lipids and proteins
• what is the function of mitochondria and the chloroplast?

  • mitochondria - site of aerobic respiration to produce ATP
  • chloroplast - site of photosynthesis to convert solar energy to chemical energy
• Describe the structure and function of a lysosome?


  Structure: Membrane-bound organelle containing digestive enzymes such as hydrolase enzymes Function: Breaks down waste materials, cellular debris, and foreign substances through the process of hydrolysis.
• Describe the structure and function of a plant cell wall?


  Structure: Rigid, outer layer composed of cellulose fibers and other polysaccharides.

  Function: Provides support, protection, and maintains cell shape.

  contains plasmodesmata form part of apoplast pathway to allow molecules between cells
• What are bacterial and fungal cell walls made of?


  bacterial - peptidoglycan (murien)

  Fungi - chitin
• Describe the structure and function of centrioles?


  Structure: Centrioles are cylindrical structures composed of microtubules arranged in a 9+0 pattern, meaning there are nine sets of microtubule triplets with no central microtubules. Function: Centrioles play a crucial role in cell division by organizing the microtubules that form the spindle apparatus. They also contribute to the formation of cilia and flagella in some cells.
• Describe the function and structure of the cell surface plasma membrane?

  • fluid mosaic (phospholipid bilayer)that contains intrinsic and extrinsic proteins
  • selectively permeable to regulate transport of substances
  • involved in cell signalling
• what is the role of cholestrol?

  steroid molecules that connects phospholipids and reduces fluidity
• what is the role of a glycoprotein?


  cell signalling, cell recognition, (antigens) and binding cells together
• describe the structure of chloroplast

  • vesicular plastid with double membrane
  • thylakoids - flattened discs stack to from grana
  • grana contains photosystems with chlorophyll
  • intergranal lamellae: tubes attach thylakoids in adjacent grana
  • stroma: fluid filled matrix
• what is the role of a glycolipid?

  cell signalling and cell recognition
• describe the structure and function of flagella?


  Structure: hollow helical tube made of protein Function: Movement or locomotion
• describe the structure and function of cilia?

  • hairlike strands on eukaryotic cells
  • move back and forth in a sweeping motion to move foreign substances
• why is the cytoskeleton important?

  • Provides mechanical strength
  • aids transport within cells
  • enables cell movement
• compare eukaryotic and prokaryotic cells?


  both have

  • cell membrane
  • cytoplasm
  • ribosomes
• features of eukaryotic cells

  • larger cells and multicellular
  • always have organelles and nucleus
  • linear chromosomes associated with histones
  • larger ribosomes
  • no capsule
  • no plasmids
  • always has a cytoskeleton
  • mitosis and meiosis (sexual and/or asexual)
• features of prokaryotic cells

  • small cells and not multicellular
  • no membrane bound organelles
  • circular DNA not associated with proteins
  • small ribosomes
  • binary fission (asexual reproduction always)
  • capsule, sometimes plasmids and cytoskeleton
• light microscopes

  • poor resolution due to the long wavelength of light
  • living samples can be examined and a colour image is obtained
• Transmission electron microscope

  • high magnification and resolution
  • electrons pass through the specimen to create an image
• scanning electron microscope

  • high magnification and resolution
  • electrons bounce off the surface of the specimen to create an image
• laser scanning confocal microscope

  • high resolution and 3D imaging
  • laser light is used to create an image
• Dry mount 


  when thin slices or whole specimens are viewed with just the coverslip on top e.g. plant tissue or hair
• wet mounts 


  when specimens are water is added to specimen before lowering the coverslip with a mounted needle to prevent air bubbles from forming. Aquatic organism could be viewed this way
• squash slides 


  wet mounts which you the push down the coverslip to squash the sample to ensure you have a thin layer to enable light to pass through

  this is used when creating root tip squash sample to view chromosomes
• smear slides 


  created using edge of another slide to smear the sample across another slide to create a smooth, thin, even coated specimen

  a cover slip is placed on top after smearing. This is used when examining blood cells in a blood sample