cells and immunity Flashcards
what does the nucleus do in a cell
contains genetic information needed for protein production and controls cell activities
what is chromatin made from and what does it form
a complex of DNA and histones that forms chromosomes
what does the nucleolus do
makes RNA which is made into ribosomes and moved out of the nucleus to the RER
what does the nuclear envelope do
double membrane which has nuclear pores to let relatively large molecules pass through
what is the structure and role of mitochondria
energy releasing cell
surrounded by a double membrane and the inner layers fold inwards to from cristae which projects into the matrix
the matrix contains enzymes needed for aerobic respiration.
there is also mitochondrial DNA and ribosomes in the matrix
what is the structure and role of the RER
consists of flattened membrane and they are studded with ribosomes.
it folds and processes proteins that have been made at the ribosomes
some of the proteins get secreted and some get put back onto the cell surface of the RER
what is the structure and role of the SER
consists of flattened membrane
synthesises and packages lipids
what is the structure an role of ribosomes
tiny organelles which can be found free in the cytoplasm or bound to the RER
consists of 2 subunits
is the site where proteins are made
what is the structure and role of the golgi apparatus
sack of fluid filled membrane bound flattened sacks
processes and packages new lipids and proteins also makes lysosomes
what is the role of Golgi vesicles
store lipids and proteins and transports them out of the cell`
what is the structure and role of lysosomes
spherical sacs surrounded by a single membrane
the Golgi vesicle contains digestive enzymes which digest cells and break down worn out cell components
what is the structure and role of centrioles
self-replicating organelles made up of microtubules and are only found in animal cells
they help organise cell division
what is the structure and role of microtubules
make up the cytoskeleton and are made up of tubulin o help provide support and movement of the cell
what are the structure and role of microvilli
cell membrane projections to increase the surface area for absorption
what is the structure and role of cilia
hair like projections made from microtubules to allow movement of substances over the cell surface
what is the structure and role of flagella
essential for the locomotion of individual organisms and are made of long microtubules
what is the structure and role of chloroplasts
small flattened scks surrounded by a double membrane
filled with liquid called stroma which contains sacks of thylakoid membranes containing chlorophyll called grana which are linked together by lamellae
photosynthesis happens in the grana and stroma
what is the structure and role of a vacuole
consist of a membrane called tonoplast filled with cell sap
maintains the pressure of the cell and keeps it rigid
what is the structure (in plants, fungi) and role of a cell wall how does it help with the transport of substances
in plants and algae - made of cellulose
in fungi it is made of chitin
provides structural support to help maintain the shape of the cell
there are pores within the cell wall called plasmodesmata which connects two cells together by their cytoplasm enabling the exchange and transport of substances
what is the role and structure of the plasma membrane
regulates movement of substances into and out of a cell
has receptor molecules allowing it to respond to chemical messengers and is made of a phospholipid bilayer
how is a red blood cell adapted for its function
they have a biconcave shape and do not contain a nucleus so there is as much space to transport oxygen as possible
how are neurons adapted for their function
have extensions called dendrites which allow communication with other neurons and a myelin sheath to insulate and speed up communication
how is a sperm cell adapted for its function
have the nucleus in the head containing half the normal number of chromosomes
has an enzyme called acrosome which is a digestive enzyme and helps break down the outer layer f the egg cell for fertilisation
has lots of mitochondria for movement
sometimes has a flagella to help with the locomotion of the cell
how are root hair cells adapted for their function
have thin walls so osmosis can happen quicker
mitochondria for active transport
a permanent vacuole to maintain the water potential of the cell
has a large surface area to increase absorption
how are xylem adapted for its function
have thickened outer walls strengthened with a substances called lignin
cells making up the xylem are virtually dead so water is allowed to flow freely
how are phloem adapted for their function
have very few subcellular structures allowing substances to flow easily
what is a tissue
a group of cells that work together to perform a particular function
what are the organelles a prokaryote has and what don’t they have
they have :
cytoplasm
ribosomes
cell wall
plasmids
capsules
flagellum
they dont have:
nucleus
membrane bound organelles
compare and contrast prokaryotic and eukaryotic cells
prokaryotic is smaller than eukaryotic
prokaryotic reproduces by binary fission and eukaryotic reproduces by mitosis or meiosis
DNA in prokaryotic is circular but in eukaryotic its linear
DNA in prokaryotic isn’t associated with histones but in eukaryotic it is
prokaryotic has no membrane bound organelles whereas eukaryotic has numerous types of membrane bound organelles
in prokaryotic the cell wall is made of murein in eukaryotic it is chitin or cellulose
what are the four structures of a virus
a nucleic acid core
a protein coat called a CAPSID
an envelope formed from the membrane of the host cell
attatchment proteins
what is magnification
how many times bigger the image is compared to the object
what is resolution
the ability to distinguish between 2 points
what conditions are needed for an electron microscope
vacuum
specimens are dead
what conditions are needed for a light microscope
no vacuum needed
specimens can be living or dead
compare and contrast electron and light microscopes
electron microscope
1. large and can b moved
2. vaccum needed
3. complicated sample prep
4. over 500,000 mag
5. 0.5 micrometers resolution
6. specimens are dead
7. uses electrons
light microscope
1. small and easy to move
2. no vacuum needed
3. easy sample prep
4. up to 2000 mag
5. 200 micrometers of resol.
6. specimens can be living or dead
7. uses light waves with long wavelength
what is an artifact
appear on the micrograph but aren’t part of the actual specimen normally are bubbles or dust.
compare and contrast TEM and SEM
TEM:
1. uses an electron gun to produce a beam that is focused onto the sample by an electromagnet
2. specimen needs to be as thin as possible so beam can pass through
3. gives resolution of up to 0.1 nanometers
SEM:
1. scans a beam of electrons across the surface of the spec. and electrons are scattered and gathered at the cathode ray tube
2. doesn’t need to be a thin sample as electrons are scattered by the specimen
3.can build up a 3D image by a computer
4. has a resolving power of around 20 nanometres
what is the equation for magnification
magnification= image size / actual size
what are the 3 steps in cell fractionation
- homogenisation
- filtration
- ultracentrifugation
describe homogenisation in cell fractionation
grinding the cells in a blender to break up the plasma membrane in a homogeniser and release organelles
the solution must be:
1. isotonic to prevent osmosis bursting cells
2. ice cold to reduce activity of enzymes that break down organelles
3. buffered to maintain pH o stop the denaturing of enzymes and proteins
describe filtration in cell fractionation
homogenised cell solution is filtered through a gauze to separate any large cell debris
describe ultracentrifugation in cell fractionation
cell fragments are poured into a tube and it is spun at a low speed and the heaviest organelles collect as a sediment and the supernatant is drained off and poured into another tube and spun at a higher speed and repeat
what is the usual order in cell fractionation or organelles
- nuclei
- mitochondria
3.chloroplast - lysosomes
- RER and SER
- ribosomes
what is the order of stages in mitosis
- interphase
- prophase
3.metaphas
4.anaphase - telophase
- cytokinesis
what happens in interphase
G1 phase cells makes RNA and enzymes and other proteins ad receives signal to divide
S phase when the DNA replicates
G2 phase is when the cell continues to grow and the new DNA that has been synthesised is checked and errors are usually repaired
what happens in prophase
- chromosomes condense and become visible
- sister chromatids are joined together at the centromere
- the two centrosomes move towards opposite poles
- spindle fibers begin to emerge from the centrosomes
- nuclear envelope breaks down
what happens in metaphase
- centrosome reach opposite poles
- spindle fibres continue to extend from centrosome
- chromosomes are lined up at the equator of the spindle s they are equidistant to the two centrosomes pole
- spindle fibre reach the chromosomes are attach to the centromeres
what happens in anaphase
- sister chromatids separate at the centromere
- spindle fibres begin to shorten
- the seperated sister chromatides are pulled to opposite poles by the spindle fibres
what happens in telophase
- chromosomes arrive at opposite poles and begin to decondense
- nuclear envelopes begin reform around each set of chromosomes the spindle fibres break down
what happens in cytokenesis
- cytoplasm divides forming two genetically identical cells
- in animals cleavage forms and separated the daughter cells in plants the cell plate forms at the site of the metaphase plate and the new daughters cells are separated