Cells - Compleate Flashcards
What is resolution?
The degree to which it is possible to tell two different objects apart that are very close together.
what is magnification?
how much larger a image size is compared to the size of the object itself.
What is staining?
Coloured stains are chemicals that bind to chemicals on the specimen so the specimen can be see. some bind to specific cell surfaces, so if a certain colour is present, then the object or organelle can be named.
what colour does acetic orcein stain DNA?
Dark Red.
What stains bacterial cell walls in particular?
Gentian Violet.
What is sectioning?
When specimens are embedded In wax, so they can then be cut out it hour distorting the specimen’s structure (often used in soft tissue, I.e. Brain)
How does a decimetre relate to a metre?
A decimetre is one tenth of a metre and is equivalent to 0.1 m
(Dm)
How does a centimetre relate to metres?
A centimetre is one hundredth of a metre, and is equivalent to 0.01 of a metre. (Cm)
How does a millimetre relate to a metre?
A millimetre is one thousandth of a metre and is equal to 0.001 of a metre. (Mm)
How is a micrometer related to a metre?
It is a one millionth of a metre and is equivalent to 0.000 001 of a metre.
How is a nanometer related to a micrometer?
It is one thousandth of a micrometer
What is the resolution for the human eye?
100um (micrometers)
What is the resolution for a light microscope?
200 nm
What is the resolution for an electron microscope?
0.2 nm
What is the sum triangle for magnification?
Image size
_________________________
Actual size x magnification
What are the characteristics of living organisms?
M movement
R respiration
S sensitivity
N nutrition
E excretion
R reproductiob
G growth
What is a cell’s ultrastructure?
The detail of the inside of a cell, as revealed by an electron microscope.
How do electron microscopes work?
- generate a beam of electrons (with wavelength of 0.004nm)
- use magnets to focus beams
- electrons are not visible to human eye so image is projected onto screen
- resolution is 0.2 nm (500 000 more than human eye)
what is a greyscale image?
An image projected onto a screen or photographic paper because we cannot see electrons with the human eye.
Describe the TEM
The transmittion electron microscope:
- electron beam passes through thin sample
- pass through less dense parts more easily (so give contrast)
- 2D image with magnification of 500 000
what is the SEM?
- electrons hit specimen and ‘bounce off’ to produce a 3D image with magnification of x100 000
What are the advantages of using an electron microscope?
- resolution in 0.1nm (better than light)
- can produce detailed images (of organelles)
- SEM can produce 3D image
What are the limitations of an electron microscope?
- specimens have to be placed i a vacuum so electron don’t bouce off air
- v. expensive
- require high skill and training
What is division of labour?
Where each type of organelle has a specific role in the cell. They work together to ensure the survival of the cell.
what is the cytoskeleton?
a internal framework made up of a network of fibres made of protein that keep the cell’s shape
What are actin filaments?
Some of the fibres in the cytoskeleton are called actin filaments which are able to move against each other. They cause movement of organelles inside cells and cause movement of white blood cells?
What are microtubules?
Some fibres that make up the cytoskeleton. They are made out of the protein tubulin. they can be used to waft a microorganism through a liquid, or waft a liquid through a cell. This is how chromosomes and vesicles move.
What are undulipodia and cilia?
hair like extensions that stick out from the surface of the cell. made up of a cylinder that contains 9 microtubules arranged in a circle with two in the middle.
What is the difference between the undulipodia and cilia?
Undulipodium has a long whip like structure which can be used to move the whole cell (e.g. sperm cells). cilia use sweeping movements to move substances across the surface of cells.
What are vesicles and vacuoles?
vesicles are membrane bound secs found in cells that are used to carry substances around cells. In plants, the vacuole maintains cell stabikity as it is filled with water to provide turgidity.
What are cell walls?
Found in plant cells, these are on the outside of the cell membrane. they are made of cellulose (carbohydrate monomer made up of glucose subunits) which provide sieve like strands to make the wall strong. it is held rigid by the pressure on the inside of cell.
Describe the structure of the nucleus.
- the largest organelle
- when stained, there are dark patches called chromatin
- surrounded by nuclear envelope (two membranes with fluid inside)
- many nuclear pores going through nuclear envelope
- dense spherical nucleolus inside
What is the function of the Nucleus?
- Contains the cells genetic material
- Chromatin is DNA and proteins, some of which regulate cell activities
- when cells divide, chromatin has condenses into chromosomes
- The nucleolus contains RNA and ribosomes which pass into the cytoplasm and assemble proteins
Describe the structure of the Endoplasmic Recticulum
- Consists of cisternae (fattened, membrane bound sacs)
- Continuous with the outer nuclear membrane
- Rough ER is studded with ribosomes
- Smooth ER is not
What is the function of the ER?
- Rough ER transports proteins made on the attached ribosomes (some may be secreted by cell or placed on the cell surface)
- the Smooth ER makes lipids
Describe the structure of the Golgi apparatus
A stack of membrane bound, flattened sacs
What is the function of the Golgi apparatus?
It modifies a proteins from the ER (e.g. by adding sugar molecules)
It packages proteins in vesicles
some of these proteins may be secreted at the cell surface
Describe the structure of mitochondria
May be spherical or sausage shape
Two membranes filled with fluid - inner membrane folds to make cristae. the central part is called the matrix
What is the function of mitochondria?
- the site where ATPis made as all activities that use energy need ATP
Describe the structure of choloroplasts
- only in plant cells
- two membranes filled with fluid
- inner membrane is continuous, with and elaborate network of thylakoids (membrane bound sacs) a pile of which is called a granum
- Chlorophyll is present in thylakoid and intergranal membranes