Chapter 3- Cells Flashcards
- Definition of magnification
- equation for magnification
- The magnification of an object is how many times bigger the image is when compared to the object
- magnification = size of image / size of real object
Definition of resolution
the minimum distance apart that two objects can be in order for them to appear as separate items
Definition of cell fractionation
the process where cells are broken up and the different organelles they contain are separated out
what 3 conditions does the solution need to be in for cell fractionation to begin
- cold - to reduce enzyme activity
- same water potential - to prevent cells bursting or shrinking
- buffered so the pH doesn’t fluctuate
Name and describe the two stages of cell fractionation
+Homogenisation
- cells are broken up by a homogeniser which releases organelles from the cell.
- resultant fluid is called the homogenate which is then filtered to remove any complete cells or debris
+ Ultracentrifugation
- the process where the fragments in the homogenate are separated in a machine called a centrifuge
- the centrifuge spins at increasingly high speeds to separate different organelles
Describe the process of ultracentrifugation
- centrifuge is spun at low speeds where the heaviest organelle (nuclei) is forced to the bottom.
- the fluid at the top (supernatant) is removed leaving the sediment of nuclei
- the supernatant is transferred to another tube which is spun at a faster rate where the next heaviest organelle (mitochondria) is forced to the bottom
- the process continues in this way at increasingly higher speeds until everything from the cell is separated out
What are the two main advantages of electron microscopes compared to optical microscopes
- electron microscopes have a shorter wavelength than light so therefore can magnify and resolve objects far better
- as electrons are negatively charged, the beam can be focussed buy using electromagnets
Name a +’ve and 2 -‘ve of both:
1. TEM
2. SEM
1.
+‘ve - Has a higher resolving power up to 0.1 nm
-‘ve - the specimen must be extremely thin
-‘ve - the image may contain artefacts
- +’ve - specimen doesn’t need to be extremely thin
-‘ve - whole system must be in a vacuum
-‘ve a complex staining process is required
Name the parts of the ultrastructure of a eukaryotic cell
- nucleus
- mitochondria
- vacuole
- chloroplasts (in plants)
- ribosomes
- endoplasmic reticulum (RER and SER)
- cell wall (in plants)
- cell membrane
- Golgi apparatus
- lysosomes
Describe the structure of the nucleus in a eukaryotic cell
- most prominent feature in the cell
- controls the cells activities
- nuclear envelope
- nuclear pore ( allows passage of large molecules)
- nucleoplasm
- nucleolus
Describe the roles of:
1. RER
2. SER
- -provides a large SA for synthesis of proteins and glycoproteins
- provides a pathway for the transport of materials especially proteins throughout the cell - synthesis, store and transport lipids
- synthesis, store and transport carbohydrates
What is the cell organisation ladder
- organelle
- cell
- tissue
- organ
- organ system
- organism
Differences between a bacterial cell and an animal cell
- bacterial cells are far smaller
- bacteria have a murein cell wall
- bacteria contains 70’s ribosomes that are smaller than animals 80’s ribosomes
- have a circular strand of DNA that’s not membrane bound
Describe viruses
- acellular, non-living particles
- smaller than bacteria
- contain nucleic acids
- can only multiply in a living host cell
- capsids have attachment proteins which are essential to identify and attach to a host cell
Describe:
1. mitosis
2. meiosis
1.
- produces 2 daughter cells
- have the same number of chromosomes as the parent cell and each other
- produces 4 daughter cells
- have half the number of chromosomes of the parent cell
