2.1.1 - cell structure Flashcards
formula of magnification
mag=image size/object size
structure of the nucleus
contains gentic info in the form of chromosomes
contains the nucleolus
surrounded by the nuclear envolope that contains pores
functions of the nucleus
controls cells activities (DNA has instructions to produce proteins)
synthesis of ribosomes - nucleolus makes ribosomal RNA
Substance can enter or leave the nucleus and cytoplasm via the nuclear pores
structure of the cell membrane
mainly made of lipids and proteins
functions of the cell membrane
controls movement of substances in and out of the cell
cell signalling - receptors can detect signals from other cells
structure of the mitochondria
contains an enzyme rich liquid called the matrix
contain the own DNA (mtDNA) and ribosomes
function of mitochondria
site of aerobis respiration and produces ATP
where are ribosomes found
free floating in the cytoplasm or attached to the rer
how many ribosomes does a eukaryotic cell contain
80S
structue of the ribosome
made of proteins and rRNA
consist of a large and small subunit
not surrounded by a membrane
funtion of ribosomes
site of protein synthesis and involved in the process of translation
structure of the golgi
contains fluid filles membrane bound sacs called cisternae
contains smaller vesicles
functions of the golgi
process and package lipids and proteins - carries out by the cisternae
store and transport lipids and proteins - done by vesicles
synthesise lysosomes
structure of the rer
contains cisternae that is covered with ribosomes
what happens at the RER
processing and folding of proteins
what happens at the SER
making and processing of lipids
what is the nucleolus
a very darkly stained area in the nucleus
what does the nucleolus do
contains DNA to make ribosomes
what is the cytosol
the soluble part left over when you remove the organelles form the cytoplasm
what does the cytosol consist of
mainly of water with dissolved substances such as amino acids
where are chloroplasts found
in some plant cells
how are the reactions in the chloroplast isolated from the rest of the cell
it is bound by 2 membranes - an envelope
do chloroplasts contain their own dna
yes
how many ribosomes do chloroplasts have
70S
why do chloroplasts contain chloropyll
for the light dependant reactions during photosynthesis
what is the granum
stacks of thylakoid inside the chloroplast joined together by intergranal lamellae
what is a lysosome
a spherical sac bound by a single membrane (0.5um diam) containing around 40-50 digestive (hydrolytic) enzymes
where are lysosomes made
golgi
what do lysosomes look like under an electron microscope
darkly stained with no clear features
what do lysosomes do
take in and digest material from the outside and inside and are involved in the self destruction of cells in the developmental process
what are cilia and flagella
long thin extensions from the surface of the cell that produce movement
where are cilia and flagella found
in some animal cells but rarely in plant cells
what is the difference between cilia and flagella
cilia are relatively short but found in large numbers but flagella are relatively long and occur in smaller numbers
cilia and flagella both contain microtubules arranged in what arrangement
9+2
how is movement produced by the cilia and the flagella
the microtubules slide against each other causing them to bend and straighten
where are centrioles found
only in animal cells
what is the structure of a centriole
consists of 2 microtubule bundles at right angles to each other
what are microtubules made of
tubulin protein subunits and they are arranged to form a cylinder
what is the function of centrioles
before a cell divides, centrioles replicate and move to the poles of the cell and form the spindle apparatus
what is the spindle apparatus made of
threads of tubulin (microtubules) which extend s from the poles of the cells
where is the cell wall found
only in plant cells
what is the cell wall made of
cellulose
what does the cell wall do
provides mechanical support and protection of the cell and prevents osmotic bursting of the cells
where is the vacuole found
it is absent or small in animal cells but large in plant cells
what is the enclosing membrane of the vacuole called
the tonoplast
why does the vacuole contain hydrolytic enzymes
to act as lysosomes during life and cause autolysis after death
what is magnification
The number of times larger an image appears compared to the size of an object
what is resolution
the level of clarity in an image
how does a light microscope work
the specimen is clipped onto the stage and the nosepiece is rotated to set a specific objective lens. The coarse and fine focusing knob are adjusted to get a clear image
where are light microscopes used
schools, colleges and research labs hospitals
advantages of light microscopes
relatively cheap
easy to use
portable
can be used to study whole living specimens
disadvantages of light microscopes
has a low mag and res
cant see some subcellular structures in detail
what is another name for laser scanning microscopes
conofocal microscope
how does a laser scanning microscope work
uses a laser light to scan an object point by point and assemble by computer to form one image
what is the laser scanning microscope used for
medicine and branches of biological research
advantages of laser scanning microscopes
can collect clear images
high resolution and contrast
can focus on different depths within the specimen
can be used to clearly observe whole living specimens as well as cells
disadvantages of laser scanning microscopes
need to be highly trained in order to use
how does a TEM microscopes work
specimen has to be dehydrated and stained. Beam of electrons passes through the specimen and form a 2D black and white image (electron micrograph)
advantages of a tem
- have a very high magnification and resolution
- high quality images
disadvantages of tem
- the image is not in colour and is in 2D
- large and very expensive
- need to be trained a lot to use
how does a sem work
electrons don’t pass through the specimen but cause secondary electrons to bounce off the specimens surface and be focused onto a screen giving a 3D image
advantages of a SEM
- gives a 3D colour image
- very high magnification and resolution
disadvantages of sem
- image is black and white but computer programmes can add false colour
- large and very expensive
- need to be trained a lot to use
what are stains
coloured chemicals that bind to molecules in or on the specimen to make it easier to see
what is differential staining
when some stains bind to specific structures
Methylene blue
an all purpose stain
acetic Orecin
binds to DNA + stains chromosomes dark red
Eosin
stains the cytoplasm
Sudan Red
stains lipids
Iodine in potassium iodide solution
stains cellulose in plant cell walls yellow and starch granules blue/black
functions of the cytoskeleton
- Maintaining the shape of the cell
- securing some organelles in specific positions
- allowing cytoplasm and vesicles to move within the cell
- enabling cells withing multicellular organisms to move
what are the 3 types of fibres within the cytoskeleton
microfilaments
intermediate filaments
microtubules
diameter of a microfilament
7nm
diameter of intermediate filaments
8-10nm
diameter of microtubules
25nm
what do microfilaments do
thicken the cortex around the inner edge of a cell and resist tension
which of the 3 fibres in the cytoskeleton can disassemble and reform quickly to allow the cell to change shape
microfilaments
microtubules
what do intermediate filaments do
hold organelles in place
have no role in cell movement as their role is purely structural
bear tension
what do microtubules do
- maintain cell shape by resisting compressive forces
- can disassemble and reform quickly like microfilaments
- help the cell resist compression, provide a track along which vesicles move through the cell
- pull replicated chromosomes to opposite ends of a dividing cell
what are microtubules made of
they are small hollow tubes with walls made from polymerised dimers of 2 globular proteins (a-tubulin and b-tubulin)
differences between prokaryotes and eukaryotes
- prokaryotic cells are much smaller than eukaryotic (around 100 to 1000 times smaller)
- Prokaryotes have 70S ribosomes but eukaryotes have 80S
- prokaryotes have a single circular DNA molecule free in the cytoplasm instead of a nucleus
- prokaryotic cells have plasmids, capsules and flagellum which eukaryotes don’t have
- prokaryotic cell division occurs via binary fission and my mitosis/meiosis in eukaryotes
