Module 2.1.1- Cell structure

• Advantages of light microscope


  -able to view living organisms

  -relatively inexpensive

  -easily available
• How to use an eyepiece graticule stage micrometer

  Stage micrometer usually consist of 100 divisions = 1mm so 1 division = 10micrometresLine stage micrometre with eyepiece graticule so for example if 50 stage micrometer divisions (known to be 500 micrometres 10x50) line up with the whole EPG (100 divisions) do 500/100= 5 micrometres= 1 EPG unit.

  
• What is the need to stain cells in microscopy


  To increase the contrast of cells so organelles can be viewed more clearly and identified
• Differential staining (2 types)


  Gram stain technique- separates bacteria into 2 types; Gram-positive and Gram-negative .Acid-fast technique- differentiate species of Mycobacterium from other bacteria
• List of rules for producing good scientific drawings

  - include a title

  - state a magnification

  - use a sharp pencil

  - use atleast 50% of the area provided

  - draw smooth continuous lines

  - no shading

  - no arrow heads

  - straight parallel label lines
• Magnification formula


  image size / actual size

  
• Magnification


  The number of times larger an image appears, compared with the size of the object.
• Resolution and magnification of a light microscope


  1500 x magnification

  50 - 200 nm
• Transmission electron microscope


  -allows you to see shapes and details of small organelles such as lysosomes, RER, mitochondria, ribosomes, Golgi apparatus, vesicles, and the nucleolus
• TEM resolution and magnification


  1,000,000 x magnification

  0.5 nm - 1 nm
• Scanning electron microscope (SEM)


  - 3D shape of a specimen with a great depth of field- surface features- 3-10 nm
• Resolution


  the ability to distinguish between 2 points and the level of detail that can be seen
• Light microscope vs Electron microscope

  Light: cheap, small and portable, simple, 2000x magnification, dead or alive.

  Electron: expensive, large, complex, over 500,000x magnification, dead
• Laser scanning confocal microscope

  -Uses laser beams to scan the specimen, which is usually tagged with the fluorescent dye.-the laser causes the dye to fluoresce. This light is then focused through a pinhole on to detector. The detector is hooked up to computer, which generates an image. The image can be 3-D.-The pinhole means that any out of focus light is blocked, so these microscopes produce a much clearer image and normal light microscope.-they can be used to look at objects of different depths in thick specimens

  
• Mitochondria


  site of aerobic respiration, producing ATP
• Function of smooth endoplasmic reticulum


  site of the transport, production and processing of lipids and carbohydrates
• Compare the difference between the cell wall of a prokaryote and plant cells


  prokaryote- peptidoglycan

  plant cells- cellulose
• Differences of a plant cell from animal cell

  Plant cells have:

  - permanent vacuole

  - cellulose cell wall

  - chloroplasts

  - starch grains

  - tonoplast

  - plasmodesmata

  
• Differences of an animal cell from a plant cell

  Animal cells have:

  - centrioles

  - glycogen granules
• Differences of prokaryotic cell from eukaryote


  Prokaryote cells have:

  - free naked circular DNA

  - smaller 70s ribosomes

  - non-membrane bound organelles

  - binary fission reproduction
• Differences of eukaryotic cell from prokaryotic

  Eukaryote cells have:

  - nucleus

  - nuclear envelope

  - membrane bound organelles

  - larger ribosomes

  - sexual or asexual reproduction
• Cytoskeleton


  - A network of fibers that holds the cell together

  - helps the cell to keep its shape

  - aids in movement with microtubules

  - cytoskeleton makes up cilia

  - allows for movement of cilia and undulipodia
• 3 components of cytoskeleton

  microfilaments

  - contractile fibres, responsible for cell movement and cell contraction during cytokinesis

  microtubules

  - determines shape of the cells, act as tracks for movement of organelles, forms spindle fibres

  intermediate fibres

  - give mechanical strength to cells and help maintain their integrity
• Golgi apparatus


  Receives proteins from the ribosomes on the RER. It processes proteins to make glycoproteins and repackages them into vesicles. It also make lysosomes, replenishes plasma membrane, and is part of lipid synthesis
• Nuclear envelope


  A double membrane that surrounds the nucleus in the cell

  Has nuclear pores to allow communication between the nucleus and cytoplasm
• Lysosomes


  contain hydrolytic enzymes for digestion of pathogens etc.can also be used to destroy cell in apoptosis
• Ribosomes


  Site of protein synthesis
• Chloroplasts


  Site of photosynthesis
• Extracellular protein production process

  1) nucleus contains gene for protein and is the site of transcription. ribosomes on RER are the site of protein synthesis (translation)

  2) protein transported in a transport vesicle to the Golgi apparatus, which then modifies it and repackages it as a secretory vesicle.

  3) vesicle moves along the cytoskeleton and fuses with the cell surface membrane by exocytosis
• Extracellular protein production process- diagram

  
• Rough Endoplasmic Reticulum


  System of internal membranes within the cytoplasm. Membranes are rough due to the presence of ribosomes. functions in transport of substances such as proteins within the cytoplasm
• Nucleolus


  Found inside the nucleus and produces ribosomes. Composed of proteins and RNA
• Site of aerobic respiration in prokaryotes


  Mesosome
• Centrioles


  component of the cytoskeleton of most eukaryotic cells, composed of microtubules two centrioles form a centrosome involved in the assembly and organisation of spindle fibres during cell division
• Flagella and Cilia


  Flagella enables motility of the cell

  Mobile cilia beat in a rhythmic manner for example to move along mucus in the trachea

  Stationary cilia present on the surface of many cells and have an important function in sensory organsCilia has a 9+2 arrangement

  
• Permanent vacuole (plant)


  Filled with cell sap to help keep the cell turgid maintaining a rigid framework. Surrounded by a membrane called the tonoplast
• Chloroplast


  organelle found in cells of plants and some other organisms that captures the energy from sunlight and converts it into chemical energy in photosynthesis

  fluid enclosed inside is called the stroma thylakoids (network of membranes) stacked together is called a granum