Chapter 3 Cells Flashcards
What are the properties of light microscopes?
-Beam of light is condensed to create the image.
-Poorer resolution due to light having a longer wavelength.
-Lower magnification
-Colour images
-Can view living samples.
What are the properties of electron microscopes?
-Beam of electrons is condensed, using an electromagnet, to create the image.
-Higher resolving power as the electrons have a shorted wavelength.
-Higher magnification
-Black and white images.
-Sample must be in vaccum, therefore non-living.
Why must samples be in a vacuum for an electron microscope?
As electrons are absorbed by air.
How does a transmission electron microscope work?
Extremely thin specimens are stained and placed in vacuum. Electron gun produces beam of electrons that pass through specimen. Some parts absorb electrons and appear dark..
How does a scanning electron microscope work?
Specimens do not need to be as thin. Electrons are beamed onto the surface and electrons are scattered in different ways depending on contours. Produces 3D image.
How do you convert from mm to micrometre?
X 1000
Why should cells be prepared in a cold solution?
To reduce enzyme activity. When cell is broken open enzymes are released which could damage the organelles.
Why should cells be prepared in an isotonic solution?
To prevent osmosis, as this could cause the organelles to shrivel or burst.
Why should cells be prepared in buffered solution?
To prevent damage to organelles.
What happens in homogenisation?
Cells must be broken open and this is done using a blender. Cells are blended in cold, isotonic and buffered solution.
The solution is filtered to remove the large cell debris.
What happens in ultracentrifugation?
-Centrifuge spins at high speeds and centrifugal forces cause pellets of most dense organelle to move to bottom of tube.
-Process is repeated at increasingly faster speeds removing supernatant each time, leaving behind the pellet.
What is the order of organelle fractionation?
Nuclei
Chloroplasts
Mitochondria
Lysosomes
Endoplasmic Reticulum
Ribosomes
Structure of nucleus
Nuclear envelope- Double membrane
Nuclear pores- allows mRNA to come out of nucleus.
Nucleoplasm - Granular jelly-like material
Chromosomes- protein bound, linear DNA.
Nucleolus- Small sphere inside inside which is site of rRNA production and makes ribosomes.
Function of Nucleus
Site of DNA replication and transcription (making mRNA)
Contains genetic code for each cell.
Structure of Endoplasmic reticulum.
Both smooth and rough have folded membranes called cisternae.
Rough have ribosomes on cisternae.
Function of RER
Protein synthesis
Function of SER
Synthesis and store lipids and carbohydrates.
Structure of Golgi Apparatus & Vesicles
Folded membranes making cisternae
Secretary vesicles pinching off from the cisternae.
Function of Golgi Apparatus
Add carbohydrates of proteins to form glycoproteins.
Produce secretory enzymes
Secrete carbohydrates
Transport, modify and store lipids.
Form lysosomes
Molecules labelled to indicate their destination.
Finished products are transported to cell surface in golgi vesicles where they fuse with the membrane and the contents in released.
Structure of lysosomes
Bags or vesicles of digested enzymes- can contain 50 different enzymes.
Function of lysosomes
Hydrolyse phagocytic cells
Completely break down dead cells (autolysis)
Exocytosis- release enzymes to outside of cell to destroy material
Digest worn out organelles for reuse of materials.
Structure of mitochondria
Double membrane
Inner membrane called the cristae
Fluid centre called mitochondrial matrix
Loop of mitochondrial DNA
Function of mitochondria
Site of aerobic respiration
Site of ATP production
DNA to code for enzymes needed in respiration
Structure of ribosomes
Small, made up of two sub units of protein and rRNA.
80s- large ribosome found in eukaryotic cells
70s- smaller ribosome found in prokaryotic cells, mitochondria and chloroplasts.
