A2.2 Cell Structure Flashcards
cell theory
Cells are the basic structural unit of all living organisms
cells can only arise from pre existing cells
smallest units of life
unicellular
consisting of a single cell
protists
eukaryotes consisting of single celled organisms
NOT plant animal or fungi
features common in all cells
NOT STRUCTURES
- Are surrounded by a membrane
- Contain genetic material
- Have chemical reactions occurring within the cell that are catalysed by enzymes
How do optical microscopes work
Light is directed through the thin layer of biological material that is supported on a glass slide
This light is focused through several lenses so that an image is visible through the eyepiece
optical microscopes
light
optical microscopes advantages
easy to use
cheaper
can observe dead or living in colour
cell movement can be studied
quick preparation
optical microscopes disadvantages
max magnification of 1500x
low resolving power
components of an optical (light) microscope are
The eyepiece lens
The objective lenses
The stage
The light source
The coarse and fine focus
graticule
small disc that has an engraved scale. It can be placed into the eyepiece of a microscope to act as a ruler in the field of view
calibrated
This is done by using a scale engraved on a microscope slide
By using the two scales together, the number of micrometers each graticule unit is worth can be worked out
Magnification general formula
magnification = image / real
electron microscope
in which a beam of electrons replaces light so the powers of magnification and resolution are corresponding much greater
advantages of electron microscope
magnification of 100000 x to 300000 x
disadvantages of electron microscope
expensive
cells have to be killed
no movement
has to be stained or dyed
preparation takes days
1 m in mm
1000 mm
1mm in um
1000 um
1 um in nm
1000 nm
1 cm in um
10000 um
resolution
amount of detail that can be seen
scale bar
straight line on the drawing or micrograph that represents the actual size before the image was enlarged
Qualitative data
non-numerical data such as colour and presence of structures which can also be determined using microscopes
quantitative observations
collection of data which are focused on numbers and values such as measurements of length, height, volume, or values of quantity and frequency
staining
chemicals that bind to structures within the sample and are used to make them show more clearly when viewed under microscope
iodine staining
starch - blue black
methylene blue
cell nuclei and DNA - stain blue
gram stain
divides nucleus into gram positive and negative
Gram-positive organisms - purple or blue
gram-negative organisms - pink or red
DNA
- The presence of DNA means that a new cell can be formed from an old cell, as genetic material is able to be stored and transferred
- DNA also controls the production of enzymes and other vital proteins within the cell
Cytoplasm
composed of mainly water with dissolved substances, such as ions - cytosol
cells chemical reactions take place within the cytoplasm
Plasma membrane
surrounds the cell and encloses all the cell contents
The membrane is responsible for controlling the interactions of the cell’s interior with the exterior
- Materials required by the cell are transported into the cell interior
- Waste substances are exported out of the cell to the surrounding environment
structures common to most prokaryotes
lack nucleus
70S ribosomes
DNA in a loop
Cytoplasm
Plasma membrane
Cell wall
Ribosomes
protiensynthesis
binding and reading of mRNA during translation to produce proteins
found freely or in RER
genetic material in prokaryotic cells
in the form of a “naked” single circular DNA molecule (not associated with proteins) located in the nucleoid and in smaller loops called plasmids
Plasmids
small loops of DNA that are separate from the main circular DNA molecule
- Plasmids contain genes that can be passed between prokaryotes (e.g. genes for antibiotic resistance)