2.1- cells and microscopes Flashcards
eukaryotic cells contain
membrane bound organelles
nucleolus
site of ribosome production
nucleus
- ALL eukaryotes except rbc
-contains CHROMATIN
-chromosomes are made of sections of linear DNA wound around proteins called histones
nuclear envelope
- double membrane surrounding nucleus
- contains nuclear pores which allow molecules (ribosomes, enzymes etc) to enter and leave the nucleus
prokaryotes contain (6)
- cell wall
- capsule
- plasmid
- flagellum
- pili
- ribosomes
preparation of solid slide for light microscope
- cut a thin (so light can pass through) section of tissue (scissors?) using a MICROTOME
- place on slide using forceps
- add a drop of stain
- add coverslip using MOUNTED NEEDLE at 45 degrees to avoid trapping air bubbles
equation for mag
image size = actual size * magnification
magnification
- factor by which the image is larger than the actual specimen
resolution(2)
- ability to distinguish between 2 objects close together
- level of detail
ribosomes
- in ALLLL CELLS
-foubd free in cytoplasm or in rough ER - made of PROTEINS and ribosomalRNA
- large subunit (which joins amino acids)
- small subunit (with mRNA binding site)
- translation here
80s ribosomes
- from 60 and 40 subunits
- eukaryotic cells
70s ribosomes
- prokaryotes, mitochondria, chloroplasts
- from 50 and 30 subunits
function of mitochondria
- site of aerobic respiration to produce ATP
-light microscope - has cristae-folds to increase SA
- matrix formed contains enzymes for aerobic respiration andDNA and ribosomes
cristae
folds of inner membrane in mitochondria; enable compartmentalisation
chloroplasts
- plant cells
- LARGER than mitochondria
-site of photosynthesis to convert solar energy to chemical energy
bacterial cell wall is made of?
peptidoglycan
fungal cell wall is made of?
chitin
cell wall
- structural support
- cellulose polysaccharide in plants
plasmodesmata
- threads of cytoplasm
- connect cytoplasm of neighbouring plant cells
flagellum
- hollow helical tube made of the protein FLAGELLIN
-made of microtubules - rotates to propel organism (usually unicellular)
cilia
- hair like projections made of microtubules
microvilli
- in specialised animal cells
- cell membrane projections
- increase SA of plasma membrane to increase rate of exchange if substances
role of cytoskeleton
- provide MECHANICAL STRENGTH to cells
- can change chape
- intracellular movement; forms tracks where organelles can move
- enables cell movement via cilia and flagella
SIMILARITIES euk and prok
- plasma membrane
- cytoplasm
- ribosomes
ribosomes eukaryote
LARGER : 80S
ribosomes prokaryote
SMALLER: 70s
how do prokaryotes reproduce
binary fission - ALWAYS asecual
how do eukaryotes reproduce
mitosis and meiosis, sexual and or asexual
plasma membrane
- ALL CELLS
-regulates movement of substances into and out of the cell - has receptor molecules which allow it to respond to chemicals eg hormones
- formed from phospholipid bilayer
plasma membranes are made of ?
lipids and proteins- phospholipid bilayer
function of lysosome
- contains digestive (hydrolytic) enzymes
- kept separate from cytoplasm by surrounding membran
- can be used to digest invading cells or break down worn out components
why do light microscopes have limited resolution?
- use light to form an image
- impossible to resolve 2 objects closer than half the wavelength of light
why do electron microscopes have higher resolution
- beam of electrons has a smaller wavelength than light
- so can resolve 2 objects v close together
TEM
- electromagnets to focus a beam of electrons
- electrons TRANSMITTED THROUGH the specimen
- denser parts appear darker as they absorb more electrons
TEM images adv
- high res
- can see internal structures
TEM disadvantages
- v thin sections
- dead specimens
- artefacts can be introduced
- black and white
SEM
- beam of electrons bounce OFF and are detected
- 3D images of SURFACE
advantages sem images
- thick specimens
- external 3D structure
disadvantages of SEM
- lower res
- dead
- b and w
differential staining
- use multiple dyes
- as diff stain for diff organelle
3 objective lenses
x4
x10
x40
preparation of liquid slide for light microscope
- use pipette to add a few drops of sample
- cover with a coverslip and gently press down to remove air bubbles
- wear gloves to prevent cross contamination of foreign cells
starting objective lens
- LOWEST power
- easier to find in field of view
- prevents damage if state too high
preventing dehydration of tissue?
- thin layers can dry quickly
- add a drop of water
how to calibrate graticule in eyepiece lens
use a stage micrometer
do chloroplasts need stains?
NO- naturally green
‘stain’ for TEM
- heavy metals
-eg gold - as they absorb electrons well
microtubules
- in all eukaryotes
-part of cytoskeleton
-made of alpha and beta tubules combines to form dimers, which join to protofilaments - 13 protofilaments = microtubule
centriole
- hollow fibres of microtubules
- make spindle fibres during cell division
- NOT in flowering plants and fungi
vesicle
membrane bound sac for transport and storage
large permanent vacuole
- in plant cels
- keep structure and turgor pressure
- surrounded by tonoplast (selectively permeable membrane)
Golgi body
- flattened sacs of membrane (cisternae)
- modifies proteins and lipids
- packages them into Golgi vesicles
smooth ER
- plant and animal
- production, processing and storage of LIPIDS (+carbs and steroids)
rough ER
- plant and animal
- surface covered in ribosomes
- processes proteins made by ribsomoes
- continuous with nuclear envelope
ONLY in animal not plant
- centrioles
- flagella/cilia
protein synthesis of PROTEINS THAT LEAVE
- transcription in nucleus, mRNA created
- mRNA leaves in a nuclear pore and attaches to a ribosome on RER
- TRANSLATION by ribosome
- cytoskeleton moves it in transport vesicles to Golgi body
- GB modifies and packages proteins into secretory vesicle
- cytoskeleton moves secretory vesicle to PM
- vesicles fuse with plasma membrane
- secreted by exocytosis
protein fibres in cytoskeleton
microtubules and microfilaments
microfilaments
- made of actin protein
- cause movement by moving against each other
microtubules
- made of tubular
- atp drives movement
plasmids
small loops of DNA
- contain genes that can be passed between proks
capsule
- prevents bacteria from drying out
hiw to find diaemeter of x using light micrscope
- eyepiece graticule
- use stage micrometer to calibrate (how many um in 1 epu)
- masure diamteter in epu
- use calibrated epu to calc diameter
- repeat and mean epu
TEM resolution
0.2nm
SEM resolution
10 nm
light microscope how do u know
- couldnt see plasmodesmata
- shape of organelle
need for stain
- provide contrast
- highlight and make components visible
- clearer image obtained
- organelles more visible as bind to stain
importance of differential stain
- see cells
- see organelles
- red blood cells always visible anyway
- CONTRAST
- can COUNT num of cells
thin slices
use a MICROTOME
- individual cells visible
endosymbiotic theory evidence
- nsmaller ribosomes
- similar siz to bacteria
- circular DNA
where are pili found
surface of prokaryotes
role of membrane in rough ER
- controls what enters rough er
- separates proteins from cytoplasm
- holds ribosomes in place
does yeast have a nucles
yes
why do the mitochondria look different
- vary in shape
- just divided
- cut at different angles
how does the cytoskeleton transport
- moves along microfilaments\tubule; provide pathways for movement
- uses ATP
- motor protein
