2.1 Cell Structure Flashcards
what does the nucleus consist of
-nucleolus
-chromatin
-nuclear envelope
-nuclear pore
what is chromatin
genetic material
what is the structure of the nucleus
contains a nucleolus and chromatin and is surrounded by the nuclear envelope which contains nuclear pores
what is the nuclear envelope
a double membrane
what is the function of the nuclear envelope
separates the contents of the nucleus to the rest of the cells
what is the function of the nuclear pores
they enable RNA to leave the nucleus
what is the structure of the nucleolus
does not contain membrane around it and contains RNA
what is the function of the nucleolus
it creates ribosomes (where they are made)
describe the structure of the rough endoplasmic reticulum
system of membranes containing fluid filled cavities that are continuous with the nuclear membrane
- coated in ribosomes
describe the function of the RER
-involved in assembling amino acids into proteins
-intracellular transport system
describe the structure of the smooth endoplasmic reticulum
-system of membranes containing fluid filled cavities which are continuous with the nuclear membrane
-is not coated in ribosomes
describe the function of the SER
-contains enzymes that catalyse reactions involved w lipid metabolism
-involved w absorption, synthesis and transport of lipids
describe the structure of the Golgi apparatus
stack of membrane bound flattened sacks
describe the function of the Golgi apparatus
it is where proteins are modified and proteins are packaged in vesicles that are pinched off
describe the structure of the mitochondria
-can be spherical or rod shaped/branched
-surrounded by 2 membranes with a fluid filled space
-inner part is a fluid filled matrix
describe the function of the mitochondria
-site of ATP production during aerobic respiration
-self-replicating so can move easily
-abundant in cell where a lot of metabolic activity takes place
describe the structure of the vacuole
-surrounded by membrane (tonoplast)
-contains fluid
describe the function of the vacuole
-maintains cell stability
-helps support the plant
describe the structure of lysosomes
-small bags formed in the golgi
-surrounded by single membranes
-contain powerful hydrolytic (digestive) enzymes
describe the function of lysosomes
-keep digestive enzymes separate from the rest of the cell
-engulf old cell organelles and foreign matter
describe the structure of ribosomes
-small spherical organelles
-made of ribosomal RNA
-made in nucleolus
-some attach to the RER and some float free
what is the structure of the nucleolus
does not contain membrane around it and contains RNA
describe the function of ribosomes
-RER ribosomes synthesise proteins that will export out of the cell
describe the structure of centrioles
-2 bundles of microtubules at right angles to eachother
-microtubules arranged to form a cylinder
describe the function of centrioles
involved in mitosis
describe the structure of the cellulose cell wall
-made of bundles of cellulose fibres
-on outside of plasma membrane
describe the function of the cellulose cell wall
-provides strength and support
-maintains cell shape
-allows solutions to pass through
describe the structure of chloroplasts
-large organelles
-have an envelope
-inner membrane has stacks of flattened membrane sacs which contain chlorophyll
-contains loops of DNA
describe the function of chloroplasts
-site of photosynthesis
-water is split to supply hydrogen ions
describe the structure of cilia and undilipodia
-protrusions from the cell
-surrounded by cell surface membrane
-contain microtubules
-formed from centrioles
describe the functions of the cilia and undilipodia
-cilia beats and moves mucus
-all cell types have 1 cilium that act as an antenna which contains receptors and allows cells to detect signals about their environment
what does the cytoskeleton contain
-microfillaments
-intermediate fillament
-microtubules
-motor proteins
what are microfilaments
polymers of actin
describe the function of microfilaments
-give support and mechanical strength
-keep cell shape
-allow cell movement
what is the intermediate filament
made of a variety of proteins
describe the function of the intermediate filament
-stabilises tissues
-anchors the nucleus with the cytoplasm
what are microtubules
made of protein subunits (tubulin)
describe the function of microtubules
-provide shape and support
-form track for motor proteins
-made up cilia, undilipodia and centrioles
what are the motor proteins
-myosins
-kinesins
-dyneins
describe the functions of motor proteins
travel along the track of microtubules
where do we have ciliated epithelial cells
in our airways
what are protrusions in prokaryotes and eukaryotes
flagella in P
Cilia and undilipodia in E
how are cilia found
short in large numbers
how are undilipodia found
long and in singular structures
compare eukaryotes and prokaryotes
-E have a nucleus, P don’t
-E are larger cells, P are smaller
-E have centrioles, P don’t
-P have a less developed cytoskeleton, E has a more developed cytoskeleton
-E contain membrane bound organelles, P don’t
- P cell wall is made of peptidolycan, E is made of cellulose
-P have circular naked DNA which floats free in the cytoplasm, E DNA is histone wound and linear
What do some prokaryotic cells contain
-protective waxy capsule surrounding cell wall
-plasmids (small loops of DNA)
-flagella
-pili
how do prokaryotic cells divide
binary fission
what is the endosymbiont theory
that eukaryotic cells arose from prokaryotic cells
what does the endosymbiont theory suggest
that the mitochondria and chloroplast were created when the invaded prokaryotes’ plasma membrane folded inwards around the invading cell
describe how a protein is produced and secreted
-The DNA from the nucleus is copied into a molecule of mRNA via a process known as transcription
-The mRNA strand leaves the nucleus through a nuclear pore and attaches to a ribosome on the rough endoplasmic reticulum
-The ribosome ‘reads’ the genetic instructions contained within the mRNA and uses this code to synthesise a protein via a process known as translation
-The processed proteins are then transported to the Golgi apparatus in vesicles, which fuse with the Golgi apparatus, releasing the proteins
-The Golgi apparatus modifies the proteins, preparing them for secretion
-the molecules get packaged into vesicles and are pinched off the Golgi
-the vesicles move towards the cell surface membrane and fuse with it through exocytosis
define magnification
the number of times larger an image appears compared to the size of the object
define resolution
the ability to distinguish between two points. Allows you to see in greater detail
how to calculate magnification
size of image/size of real object
define the 4 types of microscope
Light microscope
laser scanning (confocal) microscope
scanning electron microscope (SEM)
transmission electron microscope (TEM)
how does a light microscope work
it creates a magnified image through the use of a series of glass lenses and a beam of light onto or through an object
describe a light microscope
magnification - x1500
resolution- 200nm (0.2um)
you can see whole cells and tissues
produces a 2D coloured image
describe advantages and disadvantages of light microscopes
ADS- cheap, easy to use, portable, can study whole living specimens
DISADS- low resolution and low magnification, specimen may be disfigured during prep and cannot see small structures
How does a laser scanning microscope work?
They use a laser light to scan an object point by point and assemble the pixel info into one image on a computer
describe a laser scanning microscope
magnification- x400 to x1000
resolution- 270nm
you can see an object at a certain depth within a cell
image is 3D and black and white
describe advantages and disadvantages of laser scanning microscopes
ADS- high resolution and high contrast, depth selectivity so it can focus on structures of different depths
DISADS- limited primarily to the limited number of excitation wavelengths available
How does a scanning electron microscope work?
It passes a beam of fast-travelling electrons over the specimen’s surface.
describe a scanning electron microscope
magnification -up to x200,000
resolution- 1-20nm
you can see the surface of almost any sample
image is 3D and black and white
describe advantages and disadvantages of a SEM
ADS-the resolution can be very low so you can see microstructures
DISADS- large and expensive and must be housed in a place free of electric or magnetic interference
How does a transmission electron microscope work?
It transmits a beam of electrons for an internal view of the specimen. Specimen must be chemically fixed and stained
describe a transmission electron microscope
magnification- x2,000,000
resolution - less than 1nm
You can see organelles
Image is 2D and black and white
describe advantages and disadvantages of a TEM
ADS- allows visualisation of internal structures
DISADS- large and expensive, requires special training to operate
How to calculate total magnification
ocular lens x objective lens
why should you stain a specimen
provides contrast, allows detail, identifies different organelles
what should you be aware of when using a light microscope
specimen is 3d but your looking at 2d version some structures may be absent or will appear as different shapes
which microscope allows you to view living cells
laser scanning microscope
what does iodine stain
cellulose in plant cell walls yellow, starch granules blue/black
what does methylene blue stain
cheek cells
what does acetic orcein stain
Binds to DNA and stains chromosomes dark red
What does eosin stain?
cytoplasm
what does Sudan red stain
lipids
what is an eye piece graticule
A small ruler fitted to a light microscope’s eyepiece
What is a stage graticule?
A precise measuring device. It is a small scale that is placed on a microscope stage and used to calibrate the value of eyepiece divisions at different magnifications.
what is always the magnification of a eyepiece lens
x10
