2.1 cell structure Flashcards
light microscope
living samples
colour image
poor resolution due to long wavelength of light
transmission electron microscope
high magnification and resolution
stained and put in vacuum
electrons pass through specimen
parts of specimen absorb electrons so they appear darker
2D detailed image
scanning electron microscope
high magnification and resolution
electrons beamed onto surface and are scattered in different ways depending on contours
3D image
laser scanning confocal microscope
(fluorescent microscope)
high resolution
high light intensity
stained with fluorescent dye
3D imaging
laser light used to create image
as light is emitted from specimen it causes fluorescence
resolution
the minimum distance between two objects in which they can still be viewed as separate
magnification
how many times larger the image is compared to the object
optical microscope
determined by wavelength of light
electron microscope
determined by wavelength of the beam of electrons
electromagnet used to focus beam of e-
black and white image
why must an electron microscope be used in a vacuum?
electrons are absorbed by air
dry mount
thin slices or whole specimens viewed with just the coverslip placed on top
wet mount
water is added to specimen before lowering the coverslip with a mounted needle to prevent air bubbless
squash slide
wet mounts which you push down on the coverslip to squash the sample to ensure a thin layer for light to pass through
smear slide
using the edge of another slide to smear the sample across another slide to create a smooth, thin, even coated specimen then a coverslip placed on top of smear
eyepiece graticule
(light microscopes) scale on glass disc which is used to measure the size of objects you are viewing
how to calibrate eyepiece graticule
- line up stage micrometre and eyepiece graticule whilst looking through eyepiece
- count how many divisions on eyepiece graticule fit into one division on micrometre scale
- each division on micrometre is 10 micrometres, this can be used to calculate what one division on the eyepiece graticule is at that current magnification
formula for magnification
magnification = size of image/actual size
mm to micrometres
x 1000
differential staining
many chemical stains being used to stain different parts of a cell in different colours
Crystal violet and Methylene blue
positively charged
attracted to and satin negatively charged materials
Nigrosin and Congo red
negatively charged
cannot enter cells as cytosol repels them
creates stained background and unstained cells stand out
scientific drawing rules
pencil
title indicating specimen
magnification
annotate components
no sketching - only solid lines that do not overlap
do not shade in
cell-surface membrane (plasma membrane)
phospholipid bilayer which has embedded molecules and ones attached outside (proteins, carbohydrates, cholesterol)
CONTROLS entrance and exit of molecules
nucleus
- enclosed in double-membrane nuclear envelope with nuclear pores
- site of DNA replication and transcription (making mRNA)
- contains the genetic code for each cell
- site of ribosome synthesis
mitochondria
double membrane (inner = cristae)
fluid centre called mitochondrial matrix with loop of mitochondria DNA
- site of aerobic respiration
- site of ATP production
- DNA to code for enzymes needed in respiration
nucleolus
smaller sphere inside nucleus which is the site of rRNA production and makes ribosomes
chloroplasts (plant cells only)
surrounded by double membrane and contains thylakoids as well as fluid filled stroma containing enzymes for photosynthesis
SITE OF PHOTOSYNTHESIS
thylakoids
folded membranes embedded with pigment
found in chloroplasts
Golgi apparatus
folded membranes making cisternae
add carbohydrates to proteins to form glycoproteins, produce secretory enzymes, secrete carbohydrates, (transport, modify, store) lipids, form lysosomes, molecules labelled with their destination
vesicles
- secretory vesicles pinch off from cisternae
- finished products transported to cell surface in Golgi vesicles where they fuse with the membrane and the contents released
lysosomes
vesicles of digestive enzymes which:
hydrolyse phagocytic cells
completely break down dead cells (autolysis)
exocytosis - release enzymes to outside of cell to destroy material
digest worn out organelles for reuse of materials
cytoskeleton
network of fibres found within cytoplasm, consisting of microfilaments, microtubules, intermediate fibres which provide mechanical strength, stability and shape to the cell
many organelles are bound to the cytoskeleton
microfilaments
responsible for cell movement
microtubules
responsible for creating a scaffold-like structure
intermediate fibres
provide mechanical strength
centrioles
microtubules that occur in pairs to form centrosome, which are involved in the production of spindle fibre and organisation of chromosomes in cell division
flagella
whip-like structure useful for mobility and sometimes as a sensory organelle for chemical stimuli
cilia
hairlike projections that come out of cells, either stationary or mobile
stationary - important in sensory organs
mobile - help move substances in a sweeping motion
ribosomes
made up of protein and rRNA
site of protein synthesis
where are 80S and 70S ribosomes found?
80S - large ribosomes found in eukaryotic cells
70S - smaller ribosomes found in prokaryotic cells, mitochondria and chloroplasts
RER
folded membrane called cisternae
ribosomes on cisternae
function: protein synthesis
SER
folded membrane called cisternae
function: synthesis and store lipids and carbohydrates
cell wall
provide structural strength to the cell
plants - made of microfibrils of cellulose polymer
fungi - made of chitin, a nitrogenous polysaccharide
production and secretion of proteins
- polypeptide chains synthesised on RER
- polypeptide chains move to the cisternae in RER and packaged into vesicles to be sent on Golgi apparatus via cytoskeleton
- Golgi apparatus modifies and packages proteins into vesicles
- secretory vesicles carry proteins to cell surface membrane, where it fuses and releases the protein by exocytosis
prokaryotic cells
small, basic
cell wall: peptidoglycan and murein
no membrane-bound organelles
smaller ribosomes (70S)
DNA is not contained within nucleus
(plasmids, capsule around cell, flagella)
plasmid
small loops of DNA that only carry a few genes
occur in varying numbers
