2.1.1 CELL STRUCTURE Flashcards
Eukaryotic cells
-larger
-linear DNA
-has nucleus
-multicellular
-flagella made of micro tubes in 9+2 formation
-big ribosomes
-has introns AND exons
Prokaryotic cells
-smaller
-circular DNA
-no nucleus
-unicellular
-flagella (made of flaggelin) on helix
-small ribosomes
-no introns(only coding DNA)
Features of an animal cell
CELL SURFACE(PLASMA) MEMBRANE (lm+em) –>CILIA
CYTOPLASM(lm+em)
MITOCHONDIRA(lm+em)
LYSOSOMES(em)
(FREE FLOATING) RIBOSOMES(em)
ROUGH ENDOPLASMIC RETICULUM(em)
GOLGI APPARATUS(em)
SMOOTH ENDOPLASMIC RETICULUM(em)
VESICLES(em)
CENTRIOLES(lm+em)
NUCLEOLUS(lm)
NUCLEAR ENVELOPE(em)
NUCLEUS(lm+em)
FLAGELLA
Features of plant cells
CELL WALL (with plasmodesmata)
VACUOLE
CHLOROPLAST
cell wall
💪💪💪
description: rigid structure made up of cellulose. freely permeable. has plasmodesmata(channels for exchanging substances)
function: supports plant cells’ structure.
(permanent) vacuole
structure: single membrane, contains dissolved sugars and amino acids
function: energy source + temporary food storage
maintains turgidity in plants
cell surface (plasma) membrane
🚪🛎️📞
description: made up of lipids and proteins.
function: -regulates movement of substances in and out of cell.
-has receptor molecules that allow them to respond to chemicals.
nucleus
👷♂️🚦
structure: -separated from the cell contents by nuclear envelope with openings(nuclear pores)
-contains chromatin(made from DNA and proteins)
function: -controls protein synthesis, metabolism, cell division, and stores genetic info coded into DNA
nuclear envelope
double membrane with small
nuclear pores which control entry and exits of materials
nucleolus
produces ribosomes
composed of RNA and proteins
at least one in a nucleus
lysosome
💂💂🏻💂🏿
description:
-membrane bound with no clear structure
-contains digestive/hydrolytic enzymes i.r lysozymes
function: digestive enzymes that eat up invading cells or break down worn out cell components
ribosome
🥥🏭
description: free floating(no membrane), made of protein+RNA
function: site of protein synthesis
RER
📦📦🧑🏭
description: ribosome covered surface, system of folded membranes continuous in the nucleus with flattened sacs inside them increasing SA(cisternae)
function: site of synthesis and transportation for proteins and glycoprotein made in the ribosome into vesicles
SER
👴📦📦
description: same as RER with no ribosomes
function: synthesis, storage and transportation (in vesicles) of lipids and carbs
vesicles
👶🚪
description: small fluid filled sacs, membrane bound
function: transport substances between organelles in and out of cell (via plasma membranes)
golgi apparatus
👩👧📦
description: membrane bound, fluid filled flattened sacs (with vesicles at the edges)
function: modifies molecules transported from SER/RER to ensure they are transported to correct location i.e proteins and triglycerides
-makes lysosomes(vesicles with proteins in them)
mitochondrion
🏃♀️🏃♀️🏃♀️🏃♀️🏃♀️🏃♀️🤞
description: double membrane- inner one folded to form cristae(has matrix inside which contains respiratory enzymes)
function: site of aerobic respiration, production of ATP, large numbers and very active
centrioles
👩💼👨⚖️
description: small, hollow cylinders made up of microtubules
function: involved in separation of chromosomes/ organise spindle fibres during cell division
cilia
🌁🌁
description: small, hair like extensions found on surface membrane of some animal cells. CROSS SECTION- has an outer membrane and a ring of 9 pairs of protein microtubules inside with one pair in the middle
Function: microtubules used by the cell to move substances along cell surface(unicellular/single cell), beat rhythmically
flagellum
🚁🚁🚁
description: like cilia but tail like extensions and longer on eukaryotic cells. surrounded by plasma membrane and internally like cilia(two microtubules in the centre and 9 pairs around the edge) in eukaryotic cells
function: detects changes in cell’s environment
microtubules contract to make the flagellum move( theyre like motors that propel cell)
chloroplast
🥼
description: -small,flattened structure found in plant cells. -surrounded by a double membrane, filled with thylakoids(which are flattened sacs contain chlorophyll), to increase SA that are stacked to make grana.(they are linked up by lamallae)
function: site of photosynthesis (some of it in the grana and some in stroma which is a THICK FLUID and contains ribosomes ,DNA and starch grains)
-chlorophyll absorbs light for photosynthesis
bacteria cell structure
-DNA
-cell wall(made up of peptidoglycan)
-flagellum
-plasma membrane
-plasmids
-ribosomes
what is the cytoskeleton?
network of protein threads arranged as microfilaments(made up of actin and help move&contract during cytokinesis) and microtubules(made of tubulin and determine cell shape)
and intermediate fibres(give the cell strength)
function of cytoskeleton
-support organelles shape and stability
-holds organelles in place
-facilitates transport of organelles and materials. i.e movement of chromosomes
-makes up centrioles
-allows cells to change shape during endo/exocytosis
protein production
-made at ribosomes
-RER ribosomes make proteins attached to cell membrane
-free floating ones make proteins that stay in the cytoplasm
-RER folds and processes proteins
-then transported to golgi in vesicles where they are modified
-put in more vesicles to be transported around the cell.
specialised cells
-may have greater/fewer organelles
i.e leaf cells need many chloroplasts and sieve tubes have scarce organelles and are angular and hexagonal
functions of a light microscope
-sample is placed on a slide on the stage
-light is focused through a series of lenses on the eyepiece
-rotating objective lens changes the magnification of the image
(start with low power objective lens to locate items in the field of view)
2D image of cells&tissues
-mag= x1500
-res= 100
advantages of light microscope
-inexpensive
-portable
-simple sample prep
-living or dead specimens
function of a laser scanning confocal microscope
-specimen is stained with a dye
-laser in the microscope is moved across the specimen causing the dye to fluoresce and give off light
-the light is passed through a pinhole to the detector which generates a HIGH resolution
-2D or 3D image
advantages of lsc microscope
-simple sample prep
-living or dead specimens
-can see movement of living cells
disadvantages of lsc microscope
-low mag and res compared to electron
-expensive to buy
function of TEM
-detector picks up electrons transmitted through a specimen and focused to produce an image
-specimen is viewed in a vacuum to ensure the electron beams travel in a straight line.
-mag= x500 000
-res= 10.0
why can a higher res be achieved for TEM and SEM
electrons have a much smaller wavelength than light
disadvantages of TEM and SEM
-expensive to buy and operate
-large and needs installation
-complex sample prep
-risk of artefacts(objects that appear in the microscope that are not part of the sample i.e air bubbles)
-black and white images
-dead specimens
difference between SEM and TEM
-SEM beams electrons across surface of the specimen and images are collected via reflection of electrons whilst in TEM , electrons are transmitted through the spec to create an image
-SEM creates 3D images, TEM only creates 2D images
advantages of SEM
high res and mag
3D image
advantages of TEM
-high res and mag
-2D images obtained which show appearance of organisms
function of SEM
-detector picks up beam of electrons that are sent across surface of spec and reflected electrons are collected
-3D surface images
mag= x100 000
res= 10.0
when is dry mount used?
useful for observing thin and small objects i.e parts of insects, pollen, hairs
preparing dry mount spec
-slice spec into thin layer
-use tweezers to place it on the slide and put cover slip on top
when is wet mount used?
-when spec is wet or liquid i.e tiny aquatic organisms
preparing wet mount spec
-place small droplet of water on the slide
-place spec on top
-when inserting coverslip, stand it up straight and slower lower it tilted to prevent air bubbles
-add a stain to provide a contrast to distinguish between different structures in the sample
what is an eyepiece graticule?
transparent ruler that is fitted in the light microscope eyepiece lens which offers an arbitrary scale which can be compared to a unit of measure
-can calculate length of the object being viewed
(usually 1mm long with 100 units)
what is a stage micrometer?
scale fitted onto a coverslip that offers an accurate scale(units) with known divisons and is used to calibrate the value of the
eyepiece divisions at different magnifications.
(1mm long with 100 divisions)
how to calibrate the graticule
Set up the microscope to the required magnification to view the sample.
Place a stage micrometer on the stage.
Line up the two scales (the stage and eyepiece graticules) and count the number of divisions on the eyepiece graticule equivalent to each division
on the stage micrometre. calculate the length of one eyepiece division by ratio.
-convert answer to micrometers
what is magnification?
-how many times bigger an image viewed through a microscope is compared to the real object
magnification formula
size of image/size of object
what is meant by resolution?
the ability to see more detail/separate two objects
why do optical microscopes have low resolution?
-can catch bigger wavelength of visible light so can only show bigger organelles
why do election microscopes have a higher resolution?
-can detect smaller wavelengths of visible light so can see smaller organelles
electron vs optical microscopes
-electron has better magnification or better resolution
-optical can view living specimens and produce colour images
-optical AND sem allow for thick sample sections and easier sample prep which reduces the risk of artefact
-lscm AND sem allow for 3D while light andTEM allow for 2D images
-SEM and TEM both use vacuums
Conversions
cm= x10 = mm= x1000 = um= x1000 = nm
