Cells And Organelles Flashcards
What is resolution?
The ability to see/distinguish between 2 separate objects that are close together.
What is magnification?
The number of times larger the image is compared to the object
What is the magnification and resolution of a light microscope?
Magnification : 1000x - 2000x ( 1500x )
Resolution : 50nm - 200nm
What is the use of the light microscope?
To view cells and tissues
What is the magnification and resolution of a scanning electron microscope?
Magnification - 50000x - 500000x
Resolution - 0.4nm - 20nm
What is the use of scanning electron microscope?
Viewing the surface of cells and organelles ( surface view ) due to high resolution
Providing depth/3D structure
What is the magnification and resolution of a transmission electron?
Magnification : 300000x - 1000000 x
Resolution : 0.5nm - 1nm
What is the use of transmission electron?
Shows the ultrastructure ( detailing organelles )
What is the magnification and resolution of laser confocal microscope?
Magnification : 1000x - 2000x
Resolution - 50-200nm
What is the use of a laser confocal microscope?
A laser beam is focused at a specific depth, and used for living cells
Stained with a flourescent tag so you can see their movement
Can see different layers/depths within samples
Give examples of 2 stains
Methylene blue - for NUCLEUS - positively charge dye attracted to negatively charged materials in cytoplasm - stains RNA/DNA
Iodine - used to observe plant cells
What are the advantages of staining?
- increases contrast
- clearer image obtain
- more internal structure visible
- some organelles more visible, as they bind to stain
What are the advantages and disadvantages of SEM and TEM?
Advantages :
- Higher resolution
- SEM ( only ) is 3D and good for viewing surfaces
Disadvantages:
- have to use thin sections
- large and expensive
- must be trained to use it
- only can view dead specimens - sample must be dried and therefore dead, possibly affecting features of cell ( artefact )
- no colour for SEM and TEM
- TEM is 2d
What is advantages and disadvantages of light microscope?
Advantage :
- easy to use
- cheap
- can see living things
Disadvantage -
- low magnification and resolution
How do organelles work together in the production and secretion of proteins?
1) the nucleus produces mRNA, and thus leaves nucleus through nuclear pores
2) ribosomes, the site of protein synthesis, on the RER construct this into a protein
3) vesicle to transport the protein to the Golgi apparatus
4) Golgi modifies and repackages the protein into a vesicle
4) protein is moved using the cytoskeleton along microtubules - requires energy from ATP produced by mitochondria
5) moves to the the plasma membrane
6) fuses with the plasma membrane to release contents to outside by exocytosis
Compare eukaryotes and prokaryotes
Prokaryotes:
- smaller ( < 10nm )
- no nucleus
- naked DNA not associated with histone proteins
- no membrane bound organelles
- 70s ribosomes ( 18nm )
- single loop of DNA
- flagellum
- small circles of DNA ( plasmids )
- peptidoglycan cell wall
Eukaryotes :
- larger ( >19nm )
- nucleus
- DNA associated with histone proteins
- membrane bound organelles ( components of cell with specific functions )
- 80s ribosomes ( 22nm )
- some have flagellum with a 9+2 structure of microtubules
- cell wall is made up of chitin or cellulose
Describe the structure and function of the mitochondria
Double membrane - outer mitochondria membrane and inner mitochondrial membrane ( which has folds called cristae )
The inside is the mitochondrial matrix, which has enzymes for respiration
Function :
Aerobic respiration
How do you prepare a liquid specimen?
1) add a few drops to the sample using a pipette
2) cover the liquid with a cover slip and press down to remove air bubbles - place cover slip at an angle
3) wear gloves so no cross contamination between foreign cells
You should cut a thin layer of cells using forceps or scalpel
How do we calibrate a graticule?
As it has no fixed units, it must be calibrated with a stage micrometer ( engraved on a microscope slide ) or the measurements will be arbitrary.
You placed the graticule on the slide
m———-> Mm ——> micrometers ——->nm
X1000
X1000
X1000
What is the structure and function of the SER?
System of membranes enclosing fluid filled cavities ( cisternae ) continuous with nuclear membrane
Transport and synthesis of lipids
What is the structure and function of the RER?
Covered in ribosomes
- Folds and further processes proteins
- large SA for ribosomes to turn amino acids into proteins for protein synthesis
What is the structure and function of the Golgi apparatus?
Membrane-bound flattened sacs filled with fluid
Receives proteins from the ribosomes, modifies proteins and repackages proteins into vesicles
What is the structure and functions of chloroplasts?
It is surrounded by a double membrane made up of thylakoid stacks called grana. It is filled with a thick fluid called the stroma.
It carries out photosynthesis, where the chlorophyll absorbs light.
What is the structure and function of centrioles?
These are protein microtubules arranged into a hollow cylinder.
These are involved in the organisation of microtubules in the cytoskeleton, and these forms spindle fibres in prophase
In plant and animal cells
What is the structure and function of ribosomes?
These are two subunits that contain protein and rRNA, and these are made in the nucleolus.
This is wheee protein synthesis takes place.
What is the structure and function of lysosomes?
This is a round membrane bound vesicle produced by the GA.
This contains lysosomes, digestive enzymes, which destroy pathogens during phagocytosis.
What is the structure and function of cilia?
These are hair like extensions that are made from microtubules that moves substances across the cell surface ( by contraction ).
What is the structure and function of the cytoskeleton?
This is a network of microtubules and microfilaments.
This supports and maintains the shape of the whole cell
Mechanical strength
Movement of organelles
Movement of chromosomes and chromatids in cell division
Movement of cytoplasm in cytokinesis
Movement of RNA in protein synthesis
Can be used for changing the shape of the cell
Only in eukaryotic cells
What 2 processes rely on cytoskeleton for movement?
- movement of chromosomes and chromatids, organelles like centrioles, ribosomes etc
- cytokinesis
What is the smallest organelle?
Ribosomes
What are the 3 types of eukaryotic cells?
Animal, plant and fungal cells.
How does a nucleus look on a micrograph?
They are large and have a dark spot inside.
How are proteins packed?
DNA is packed with proteins known as histone proteins. Together we call it chromatin.
This means protein does not occupy space.
Why can light microscopes not see mitochondria?
Resolution is not high enough
Wavelength of light is too long
Why is cilia and flagella considered to be a part of the cytoskeleton?
They are maintained by microtubules
How does the cytoskeleton moves organelles/vesicles around the cell?
These attach to the cytoskeleton
Move by protein motors - dyneins and kinesins
What is the function of microtubules?
Moved chromosomes from the equator of the cell to the poles of cell in mitosis by attaching to the centrosome
Support cell shape
Organelle movement
Used as train tracks
Which microscopes produce coloured images?
Light microscope
Laser scanning confocal microscope
Why are wet mount slides used?
Used for live specimens
Eg aquatic animals
To prevent dehydration / distortion of tissue
How to conduct a wet mount sample
1) use pipette to add drop of water to slide
2) use tweezers to place specimen in water
3) tilt cover slip down onto specimen
4) to add the stain, place the stain at one edge of the cover slip and place paper towel next to it at opposite edge
5) paper towel will draw up stain under the slip through the specimen
Ways to improve experimental procedure when observing cells under light microscope ( i.e for eg measuring diameter )
Sharp blade used so slide is thin enough and individual cells can be seen
Thinnest slices to allow maximum light to penetrate through
Wet mount to prevent dehydration/distortion of tissue
Squash the slide - easier to see individual cells
Things to consider when using stain on sample + cover slip
Place your stain at the edge of the sample
Lower your cover slip at an angle
Use blotting paper to remove excess stain
Use more than one stain to increase contrast
Which microscopes produce 3D images?
Laser scanning confocal and SEM
Compare a laser confocal scanning microscope to a electron microscope
- lower resolution
- florescent tag on cells
- can see different depths of cells
- can see movement ( as can be used on living cells )
What is the importance of differential staining?
- identify cells
- identify organelles
- increase contrast
Why do RBC not require a stain but WBC do?
RBC have their own pigment so do not need stain to be seen
WBC need stain to be seen
Are ribosomes membrane bound? Where are they found?
No
Eukaryotic and prokaryotic cells
What occurs in the nucleus ( more specifically, nuceolus)?
Synthesis of RNA
What components are ribosomes made up of?
rRNA and protein
What is the membrane of a vacuole called?
Tonoplast
Evidence for endosymbiotic theory ( i.e concept that mitochondria and chloroplasts evolved from free living bacteria )
mitochondria contain ribosomes that are smaller than those found in the cell cytoplasm
mitochondria are a similar size to bacteria
mitochondria/chloroplasts have their own circular dna
What type of cell is an onion peel cell?
Eukaryotic
Implications of using a light microscope
If a light microscope is used to view a cell, then magnification will only be up to 1500x, the colour of the cell will be visible, and organelles such as mitochondria will not be visible. There will also be a wide field of vie
Why might a cell not taking up any stain?
Cells may not take up stain that needs to be taken up by active transport if they are dead or not respiring
Which organelles can be seen with TEM?
lysosomes, RER, mitochondria, ribosomes, Golgi apparatus, vesicles, and the nucleolus
How is bacteria adapted to sticking to cells lining the cut?
Bacteria are adapted to sticking to cells lining the gut as they have extensions of the plasma membrane called pilli that allow for binding/attachment, and they have glycoproteins in their cell membranes with a specific complementary shape so they can bind to receptors on human cells of the gut lining
Why can mitochondria vary in shape and size when looked under a microscope?
Mitochondria vary in shape and size when viewed under a microscope as mitochondria vary in shape and size as some may have just divided, as they may have been cut in different planes/angles, and potentially due to artefact formation (deformed during preparation of section)
Other evidences include :
length / size , similar to that of a bacterium ✓
contain (circular) DNA ✓
contain (70S / small / 20nm) ribosomes ✓
(may) have plasmids ✓
have double membrane ✓
How do plant and animal cells differ?
Plant cells differ from animal cells as they have a permanent vacuole, a cellulose cell wall, chloroplasts, starch grains/ amyloplasts, a tonoplast, and plasmodesmata. Animal cells differ from plant cells as they have centrioles and glycogen granules
Function of lysosomes
Lysosomes contain hydrolytic enzymes to break down worn out organelles, as well as foreign objects, toxins, and pathogens. They can also be used to destroy the cell in apoptosis
What are the means of cell division for yeast?
Budding
What type of cells are RBC and WBC?
Eukaryotic cells
Benefits of early eukaryotes having more mitochondria
1 would be able to respire aerobically ✓
2 (this) produces more ATP ✓
3 ATP needed for , active transport / cell division
/ protein synthesis / DNA replication ✓
4 more ATP allows faster metabolic , processes
/ reactions ✓
Functions of cytoskeleton in protein synthesis
movement of mRNA from nucleus to ribosome
✓
movement of polypeptides through the rER ✓
movement of vesicles from rER to Golgi ✓
movement of vesicles between cisternae of
Golgi (cis to trans face) ✓
movement of secretory vesicles from Golgi to
cell surface membrane✓
What type of cell are onion root cells? What features do the roots have and do not have?
Eukaryotic
Root cells of onion cells have :
- mitochondria
- cellulose cell walls
Do not have 70s ribosomes or chloroplasts
