cell structure Flashcards
magnification defintion
the number of times larger an image appears compared to its actual size
resolution definition
the ability to distinguish between 2 separate points in an image
measure of clarity
microscopes allow us to ______ objects and therefore study organisms at a ______ level
magnify
cellular
magnification equation?
what is the total magnification?
eyepiece magnification x objective magnification
which type of microscope was the first to be developed?
light microscope
light microscope magnification range
4x to 2000x
light microscope resolution
200nm
3 advantages of using light microscopes
easy to section and stain specimen
easy to use
both dead and living samples can be viewed
chepa
path of light in a microscope
light from source travel through the specimen, through the objective lens, through the eyepiece lens, to your eye
eyepiece lens magnification and what does it contain?
x10
contains eyepiece graticule
turret function
rotates to bring the objective lenses into place
objective lenses powers/magnifications
low=x4
medium=x10
high=x40
stage function
where the microscopic slide is placed
condenser function
used to vary intensity of light reaching the object
fine focus function
used to focus high-power objective lens
coarse focus function
used to focus low and medium-power objective lenses
3 advantages of staining specimens to be viewed under a microscope
increases contrast in the slide
easier to distinguish between different organelles
stains bind to particular molecules e.g. toluidine blue binds to chromosomes, iodine solution binds to cellulose
what is Gram’s stain used for?
classifying bacterial species into 2 large groups: gram-positive and gram-negative
this helps doctors prescribe correct medicine
Gram’s stain steps
stain bacteria
fix colour
decolourise cells
apply counterstain
Gram’s stain colour
pink and purple
wet mounting meaning and steps
involves water/ stain
1)put a drop of water/stain onto specimen
2)lower a cover slip onto the specimen
dry mounting meaning and steps
does not involve any water/ stain
1)observe specimen on a slide
assume specimen is cut very thinly so light can pass through
a lot of biological tissue is transparent ; why is this a problem when using microscopy to view it and how can it be overcome?
would not show up clearly
stain specimen to increase contrast between cells/organelles and increase ability to distinguish between them
why must specimens be thin on a slide
light must be able to pass through the specimen
for clarity you want to be able to only see a single layer of cells
why should the refractive index of media when wet mounting be about equal to glass
if light is refracted too much or too little, the image is distorted
describe how a slide to show onion cells could be prepared
a layer of onion cells removed from epidermis using mounted needle/forceps
placed onto slide, ensuring it does not fold
stained with 1 drop of iodine solution
cover slip placed on at angle so no air bubbles form
ready to be viewed
why should a cover slip be placed onto a wet mount at an angle
it prevents air bubbles forming, which can distort the image
what is laser scanning confocal microscopy
a light microscope that sues lasers and fluorescence to create a 3D image of a sample
what type of image does laser scanning confocal microscopy form
a 3D image with depth selectivity
how does laser scanning microscopy differ from conventional light microscopy?
uses lasers instead of visible light
higher magnification
builds up image thorough computer which is 3D
higher resolution
how is an image formed in laser scanning confocal microscopy
laser beam is focussed onto a sample by mirrors. the sample, stained by fluorescent dyes, reflects the laser back through a pinhole to a detector. This is attached to a computer which builds up the image one pixel at a time.
what is laser scanning confocal microscopy used to observe and why
living organisms/species because it is non-invasive
you can watch a process taking place
what are the 2 types of electron scanning microscopy?
scanning electron microscopy (SEM)
transmission electron microscopy (TEM)
how does a scanning electron microscope work
electrons are fired at a specimen and bounce off the surface
these are detected by a compute and an image is built up
scanning electron microscopy magnification range
100x-100,000x
scanning electron microscopy resolution range
3-10nm
advantages of scanning electron microscopy
3D image formed
surface detail
how does a transmission electron microscope work
electrons are fired through a specimen
these are detected by a computer and an image is built up
transmission electron microscopy magnification range
100x-2,000,000x
transmission electron microscopy resolution range
0.2-1.0nm
disadvantages of electron microscopy
highly specialist training is required for use
complex slide preparation means artefacts can be produced so the image is distorted
electron beam can damage the specimen
specimens must be dead because the images are viewed under a vacuum so you cannot observe live processes
TEM is 2D
advantages of electron microscopy
3D for SEM
surface detail
high magnification and resolution, but TEM>SEM
advantages of laser scanning confocal microscopy
depth selectivity
3D image
observe living organisms and processes taking place
disadvantages of laser scanning confocal microscopy
limited magnification and resolution (not as high as electron microscopy)
success criteria for biological sketches
plain paper; use over half
single, clear, continuous line with a sharp pencil
no shading or colour
correct proportions
label lines in pencil with a ruler; start at structure, do not cross and are horizontal
horizontal labels
no arrowheads
title at top
scale bar in pencil with ruler at the bottom
what makes up a nucleus?
nucleolus
chromatin
nuclear envelope
nuclear pores
where is the nucleolus located?
in the centre of the nucleus
where is the chromatin located?
surrounds the nucleus
where is the nuclear envelope located?
surrounds the chromatin
what are the nuclear pores?
they are holes in the nuclear envelope
nucleolus structure and function
contains ribosomal RNA
ribosome and RNA synthesis
chromatin structure and function
loosely packed DNA
contains chromosomes
nuclear envelope structure and function
double membrane
compartmentalises the nucleus
regulates exchange between the nucleus and cytoplasm
some protein synthesis
nuclear pore structure and function
at regular intervals around the nuclear envelope
allow the mRNA, tRNA and rRNA out of the nucleus
nucleus structure and function
major cell containing chromatin (DNA and histones)
regulates cell activities
carries hereditary information
site of transcription
smooth ER structure and function
no ribosomes
tubular
intracellular single-membrane system
lipid, steroid hormone and phospholipid synthesis
lipid transport
rough ER structure and function
covered with ribosomes
cisternae
continuous with nuclear envelope
intracellular single membrane
transport and folding of proteins
protein synthesis at ribosomes
intracellular transport
mitochondrion structure and function
double membrane
inner membrane is folded into cristae
carries enzymes for respiration
matrix at centre
site of aerobic respiration to produce energy as ATP
Golgi apparatus structure and function
specialised smooth ER forming a stack of disc-shaped cavities (cisternae)
glycoprotein, polysaccharide and hormone synthesis
lysosome production
packaging and modification of proteins into vesicles (for storage in cell/ export)
microvilli structure and function
outfoldings of the plasma membrane
increase surface area for movement of molecules
plasma membrane structure and function
phospholipid bilayer
single membrane
selective barrier
retains cell contents
compartmentalises cell
controls what enters and leaves the cell
lysosome structure and function
single membrane-bound same of enzymes
spherical vesicles
intracellular digestion by hydrolytic enzymes
where are lysosomes abundant
phagocytes
centriole structure and function
rod-like structures containing microtubules
cell division in animal cells
produces spindle fibres in meiosis and mitosis
middle lamella structure and function
contains pectin
sandwiched between cellulose in cell wall
increases the rigidity of the cellulose cell wall
plasmodesma structure and function
pores linking plant cells
allow exchange of water and minerals between cells
starch grain structure and function
contain strach (polysaccharide of amylose and amylopectin)
compact
insoluble
storage of carbohydrate
cellulose cell wall structure and function
cellulose is composed of alternate beta glucose monomers (every other is rotated 180 degrees) to produce a straight chain, layered structure of cellulose microfibrils
freely permeable
maintains mechanical strength (holds shape of cell)
protection
ribosomes structure and function
small particles with complex structure. found on RER/in cytoplasm
2 subunits
protein synthesis (translation)
chloroplast structure and function
stoma
double membrane
grana (stacks of thylakoids)
contains chlorophyll and enzymes for photosynthesis
absorb light (photons) for photosynthesis
production of carbohydrates from simple raw materials (CO^2 & H2O)
cilia and flagella structure and function
fine hairs projecting from cell surface
9+2 arrangement of microtubules (2 central surrounded by 9 pairs)
cell locomotion
transport of extracellular materials
tonoplast structure and function
single membrane
surrounds the vacuole
exerts turgor pressure on the cellulose cell wall
cell sap structure and function
contains sugars and water
acts a store of food and waste materials
what do the tonoplast and cell sap make up together?
the vacuole
microfilaments structure and diameter
long, thin, flexible threads
5nm
microfilaments protein
actin
microfilaments functions
cell movement
cell division, because allows formation of plasma membranes around new daughter cells
contractile protein, so is used in muscle contraction
3 types of cytoskeleton
microfilaments
microtubules
intermediate fibres
microtubules structure and diameter
thick, cylindrical tubes which form tracks
25nm
microtubules protein
tubulin
microtubules functions
movement of organelles and/or vesicles around cell-> this requires motor proteins and ATP
9+3 arrangement in the centrioles -> spindle fibre formation in cell division
intermediate fibres structure and diameter
rope-like proteins that span the cell
variable diameter
intermediate fibres proteins
elastin
collagen
intermediate fibres functions
cell scaffolding
mechanical strength
therefore prevents cell from collapsing and hold organelles in place
centrioles structure
found where
9+3 microtubule structure
in animal cells
found in pairs near nucleus
centrioles function
produce mitotic spindle that separates chromosomes in cell division
what are centrioles found in? details…
pairs
1 member of each pair moves to opposite poles in cell division
are centrioles membrane-bound?
NO
flagella and cilia structure
9+2 arrangement (9 pairs with a central pair)
flagella location and function
attached to some bacteria and sperm cells
provide motility to cell, which requires ATP
cilia location, structure and function
found in airway lining
hair-like structures
work with GOBLET CELLS (produce mucus) to trap and waft bacteria/dust to the back of the throat
division of labour step by step with insulin as an example
insulin gene is transcribed in the nucleus
mRNA moves out of the nucleus through a nuclear pore and attaches to a ribosome
translation of mRNA produces a polypeptide chain
as polypeptide moves through the cisternae of the RER, it is folded into a 3D shape
polypeptide buds off the RER in a vesicle and moves towards the cis face of the Golgi apparatus via the microtubules (uses motor proteins and ATP)
as insulin moves through Golgi apparatus, it is modified and packaged into another vesicle, leaving the trans face
insulin moves to the plasma membrane in a vesicle and fuses with it
insulin is released by exocytosis
what is a polypeptide chain
a chain of amino acids joined by peptide bonds
what is exocytosis
the process of moving materials from within a cell to the exterior of the cell.
example of prokaryotic cell
bacteria
reproduction of prokaryotic cell
asexual
do prokaryotic cells have membrane bound organelles?
no
DNA of prokaryotic cells
circular chromosome and plasmids
cytoskeleton of prokaryotic cells
simple
size of ribosomes of prokaryotic cells
70s (smaller than eukaryotes)
do prokaryotic cells have cilia/flagella
some have flagella
what is a prokaryotic cell wall made of
murein
examples of eukaryotic cells
animal
plant
fungi
protoctists
do eukaryotic cells have membrane bound organelles?
yes e.g. nucleus, mitochondria
eukaryotic cells DNA
nucleus
eukaryotic cells cytoskeleton
complex cytoskeleton
eukaryotic cells ribosome size
80s (bigger than prokaryotes)
do eukaryotic cells have cilia/flagella
yes; both
eukaryotic cells cell walls?
plants have cellulose cell wall
fungi have chitin cell wall
eukaryotic cells reproduction?
sexual and asexual
5 differences between prokaryotic and eukaryotic cells
nucleus
membrane bound organelles
murrain cw/no,cellulose or chitin CW
70s ribosomes/80s ribosomes
looped,circular DNA/linear DNA
out of animal, plant and bacterial cells, which contain centrioles?
animal cells only
can plants and animal cells make glucose?
ONLY PLANT CELLS
how could a scientist use a light microscope to view cells on a prepared slide containing a blood sample?
firstly use the lower powered objective lens
use the coarse adjustment knob to bring the stage up
rotate the mirror so the light shines through the sample
look down the eyepiece and use the knob to focus the image
adjust the focus with the fine adjustment to get a clear image
greater magnification with a higher power so use turret to bring lens with a greater magnification into place if needed
why can cytoskeleton degradation lead to a lack of muscle control?
proteins may not be successfully carried to the muscle cells because a vesicle cannot be transported
nerve cells may lose strength and stability so break down
what does indirect stain do?
examples
only stains the background
carbol fuschin, india ink, picric acid
what does selective stain stain?
examples
stains particular part of specimen
malachite green, congo red, crystal viotel
what does direct stain stain
examples
only stains the specimen
methylene blue, safranin
what does differential stain stain
examples
stains the cell wall
grams stain, ziehl nelson stain
