Cell Ultrastructure Flashcards
What is the maximum magnification of a light microscope?
Up to 1500x in total
What limits the resolution of a light microscope?
The wavelength of visible light
Name two advantages of light microscopes
- Relatively cheap
- Wide range of alive specimens can be observed
Name the two ways of preparing a specimen for viewing under a light microscope?
- Staining
- Sectioning
Give 2 disadvantage of using a light microscope?
- Relatively low resolution doesn’t give detailed information
- Non-coloured specimens must be stained for specific organelles/molecules
Give 2 advantages of using an Electron microscope
- Produces detailed images of the structures INSIDE cells
- SEM produces detailed 3D images showing contour of cells
Give 2 disadvantages of using an Electron microscope
- Extremely expensive
- Samples must be dead and in a vacuum
State the magnification formula
Magnification = image size / object size
Give the definition of Magnification?
Number of times larger an image appears compared to the real size of the object
Give the definition of Resolution?
The ability to distinguish between two adjacent but separate points
Describe the structure of the nucleus (3)
- Surrounded by nuclear envelope
- Contain chromatin
- Nucleolus at the centre
What is the function of the Nucleus (3)
- Houses all of cells genetic material
- Chromatin consists of DNA and proteins
- Has instructions for making proteins
What is the Nucleolus?
Dense spherical structure inside the nucleus
What is the function of the nucleolus?
- Makes RNA and ribosomes
- These pass into cytoplasm and are the site of protein assembly
What is the structure of the nuclear envelope
- Surrounds nucleus
- It is 2 membranes with fluid between them
- Nuclear pores go through the envelope
What is the function of the Nuclear envelope?
The pores in the envelope allow passage of relatively large molecules
Describe the structure of the Rough Endoplasmic reticulum
- Flattened membrane sacs called cisternae
- Continuous with outer nuclear membrane
- Studded with ribosomes
Describe the function of the Rough Endoplasmic Reticulum
- Transports proteins made on attached ribosomes
- Some of these proteins are secreted from the cell
- Some are placed on the cell surface membrane
Describe the structure of the Smooth Endoplasmic reticulum?
- Flattened membrane sacs called Cisternae
- Continuous with outer nuclear membrane
- NO RIBOSOMES LIKE RER
What is the function of the Smooth Endoplasmic Reticulum?
Involved in essential lipid production
Describe the structure of the Golgi apparatus
A stack of membrane bound flattened sacs
What is the function of the Golgi apparatus?
- Receives proteins from the SER and modifies them
- Packages modified proteins into vesicles for transportation
- Some are then secreted from surface of the cell
Describe the structure of a Ribosome
- No outer membrane
- Tiny organelles
- Each consists of 2 sub units
Where in the cell are ribosomes found?
Some in the Cytoplasm, some bound to the RER
What is the function of Ribosomes?
- Site of protein synthesis in the cell
- Act as an assembly line where mRNA is used to assemble proteins from Amino Acids
Describe the structure of Mitochondria
- Spherical/sausage shaped
- Double membrane
- Membrane separated by a fluid filled space
- Highly folded inner membrane forms Cristae
- Central part called matrix
What is the function of Mitochondria
- Site of ATP production
- Powerhouse of the cell
Describe the structure of Lysosomes
- Spherical sacs
- Surrounded by single membrane
What is the function of Lysosomes?
- Contain powerful digestive enzymes
- Enzymes break down materials
Where are Chloroplasts found?
Plants and some protoctists
Describe the structure of Chloroplasts
- Double membrane
- Separated by a fluid filled space
- Continuous inner membrane with network of flattened membrane sacs called Thylakoids
Describe the structure of the Cell Surface Membrane
Continous outer membrane and cell receptors present on surface
What is the function of the cell surface membrane?
- Selectively permeable
- Controls exchange between cell and environment
- Receptors on cell surface allow for Endocytosis and Exocytosis
Describe the Structure of Centrioles
- Two bundles of Microtubules
- Small tubes of Tubulin protein fibres
Where are Centrioles found?
In a pair next to nucleus of animal cells
What is the function of Centrioles?
- Take part in cell division
- Form spindle fibres, moving chromosomes in cell division
Describe the structure of Flagella
- Extension sticking out from the cell
- Cylinder contains nine microtubules arranged in a circle
- Long
- Usually present in 1 or 2
What is the function of Flagella
- Acts as a ‘Tail”
- Enables movement
Describe the structure of Cilia
- Hair-like extensions
- Stick out from the cell surface
- Cylinder contains nine microtubules arranged in a circle
- Short
- Usually present in large numbers
What is the function of Cilia?
- ‘Hairs’
- Allow for movement of substances
What is a Cytoskeleton?
A network of fibres made from proteins
What are the two components of the Cytoskeleton?
Actin filaments and microtubules
What do the Actin filaments in the Cytoskeleton cause?
They move against each other causing the movement seen in WBC’s. They also move some organelles around within the cell
What are Microtubules made from?
Tubulin
What are Microtubules in the Cytoskeleton used to do?
To move microorganisms through a liquid, or waft a liquid past a cell
What is the role of the Cytoskeleton?
- Provide mechanical strength for the cell
- Aids transport within cell
- Enables cell movement
In what two ways does the Cytoskeleton aid transport within the cell?
- Movement of chromosomes during cell division
- Movement of vesicles from the ER to Golgi
What type of Ribosomes are present in Eukaryotes?
80s ribosomes
What type of Ribosomes are present in Prokaryotes?
70s Ribosomes
What are Prokaryote cell walls made out of?
Peptidoglycan
What are Eukaryote cell walls made out of?
Plants - Cellulose
Fungal - Chitin
How is DNA stored in Eukaryotes compared to in Prokaryotes?
In Eukaryotes = Stored as Chromosomes within nucleus
In Prokaryotes = DNA is free in Cytoplasm in a single loop and some other little loops called plasmids
Where does ATP production take place in Prokaryotes compared to Eukaryotes?
In Prokaryotes = In the cell surface membrane
In Eukaryotes = In the Mitochondrial Cristae
What type of respiration happens in Prokaryotic vs Eukaryotic cells?
In Eukaryotes = Strictly aerobic only
In Prokaryotes = Sometimes capable of anaerobic respiration
