1- cell structure Flashcards
1cm -> 10mm
how to get to micrometres, nm
x 1000
why are electron microscopes better resolution than light
- electron wavelength shorter than wavelength of light
x 250000 mag
(0.5nm res)
light
x1500 mag
magnification + resolution difference
mag: how many times image larger than original
res: smallest distance between 2 points where 2 points can be distinguished
-ve of electron microscope
- extremely expensive
- more elaborate sample prep required
- can’t observe live specimens bc sample needs to be dry+unmoving
- can’t observe colour since electrons are colourless
how to observe cells at high power
- locate specimen using low power objective lens
- focus using low power objective lens BEFORE high power objective
- only use fine focus with high power objective
Describe how a transmission electron microscope works to give a higher image resolution.
- electrons pass through thin specimen
- denser parts absorb more electrons
- denser parts appear darker
- so high res bc short wavelength
ALWAYS mention wavelength when talking abt resolution
-: of TEM
- must be in vacuum
- specimen must be very thin
- artefacts present
- complex staining method
Describe how to make a temporary mount of plant tissue when using an optical microscope.
- add drop of water to glass slide
- obtain thin section of plant tissue and place on slide / float on water drop
- stain with iodine in potassium iodide
- lower cover slip using mounted needle
Describe the function of the nucleus in non-dividing cells
- contains chromosomes/DNA/gene (coded info for DNA synth)
- contains sequence of bases in DNA
- site of transcription+translation
- makes ribosomes
cell wall material: prokaryotes, fungi, plants
murein, chitin, cellulose
vacuole
maintains pressure inside cell- turgidity
stores food reserves/waste
Roles of CSM
- selectively permeable barrier(between cytoplasm+external environment)
- receptors for cell signalling
- cell recognition with cell surface antigens
What are the key differences between prokaryotic and eukaryotic cells?
Prokaryotic cells: No nucleus, circular DNA, 70S ribosomes, few organelles, small (0.5–5µm).
Eukaryotic cells: Nucleus, linear DNA, 80S ribosomes, many organelles, larger (40µm)
function of Golgi Apparatus (lipid+protein)
processes+package: cisternae
store+transport: vesicles
synthesise lysosomes: specialised vesicles
function of lysosomes
contain hydrolytic enzymes to break down waste+old organelles
RER
Transports proteins, covered in ribosomes
SER (lipids+carbs)
Synthesises+stores lipids (cholesterol+steroids), no ribosomes
lysosomes
digest pathogens+break down waste
hydrolytic enzymes, surrounded by membrane to keep enzymes separate from cell
What is the evidence for the Endosymbiotic Theory?
(theory that mitochondria and chloroplasts originated as free-living bacteria that were engulfed by a larger cell)
Mitochondria and chloroplasts have their own DNA, double membranes, 70S ribosomes, and replicate like bacteria
cytoskeleton: made of
microfilaments, microtubules, and intermediate filaments
provides structure to cell
microfilaments
Made of protein actin.
Involved in cell movement and locomotion, such as crawling and muscle contraction
microtubules
Made of protein tubulin.
Form scaffold-like structure throughout the cell.
Form the main component of the mitotic spindle, used for cell division.
Act as tracks for intracellular transport of vesicles and organelles.
intermediate filaments
Maintain the position of organelles within the cell.
Responsible for the mechanical strength of certain tissues, such as the skin and hair.
CW
- supports cell
- prevents cell from bursting- can withstand osmotic pressure
- allows substance exchange between cells(plasmodesmata)
vacuole
cell sap(salts, sugars)
Helps to maintain pressure within the cell, which keeps the cell rigid and stops the plant from wilting
algal+fungal can be uni/multicellular
algal chloroplasts are diff shape
fungal cells dont have chloroplasts
prokaryote capsule
extra layer around CW
made up of polysaccharides, protects cells from attack by antibiotics or white blood cells
pili
hair-like structures attaching prokaryotic cells to other cells/surfaces
always present in virus (2)
genetic material: DNA/RNA (single/double)
capsid: layer of protein molecules surrounding+protecting genetic material
sometimes present
envelope (phospholipid)
glycoproteins (help viruses bind to host cells)
enzymes (allows them to convert RNA into DNA)
