B1 - Cell Biology Flashcards
how are sperm cells specialised
long tail
streamlined head
mitochondria to provide energy
enzymes in head to digest through egg cell membrane
how are nerve cells specialised
long to cover distance
branched connections at the ends to connect to other nerve cells and form a network
how are muscle cells specialised
long so they have space to contract
lots of mitochondria to generate the energy needed
how are root hair cells specialised
they give the plant a bigger surface area for absorbing water and mineral ions
how are pholem and xylem cells specialised
xylem - hollow in the centre
pholem - very few subcellular structures
when do most animal cells differentiate
at a very early stage
in mature animals, what is cell division mainly restricted to
repair and replacement
what happens as a cell differentiates
it acquires different subcellular structures to enable it to carry out a certain function
how often do bacteria multiply by binary fission
every 20 mins given they have enough nutrients and suitable temp
what does the nucleus of each cell contain
chromosnes and dna
what do chromosones carry
genes
what are chromosones normally found in
pairs
describe the stages of the cell cycle
1 - grows and increases the number of sub cellular structures
describe the stages of mitosis
1 - grows and increases the number of sub cellular structures. the dna replicates to form 2 copies of each chromosones
2 - one set of chromosones is pulled to each end of the cell and the nucleus divides
3 - the cytoplasm and cell membrane divide to form 2 identical cells
when do organisms use mitosis
to grow or replace cells that have been damanged
what is a stem cell
an undifferenciated cell
what are stem cells from human embryos used for
cloned to differentiate into most different types of human cells
what are stem cells in bone marrow used for
to mainly make blood cells
what is the benifit of using meristem tissue
it can differentiate at any stage of the plants life
what conditions can be treated w stem cells
diabetes
paralysis
what is theraputic cloning
when the embryo is produced with the same genes as the patient
advantage of theraputic cloning
cannot be rejected by the patients body as they have the same genes
disadvatage of stem cell use
risks of trasfering viral infection
religious and ethical beliefs
what is diffusion
the net movement of particles from an area of higer concentration to lower concentration
what are factors which affect the rate of diffusion
the concentration gradient
temp
surface area
how are the lungs specialised to exchange materials
they have alveoli. alveoli have:
a huge surface area
moist lining for disolving gasses
thin walls
good blood supply
how are the villi adapted
they increase the surface area
single layer of surface cells
good blood supply
how are the leaves adapted
they have stomata.
flattened shape of the leaf increases the surface area
how are gills adapted
gill fillaments increase the surface area
lamallae increase the surface area
lots of blood capilliaries to speed up diffusion
thin surface layer of cells
what makes a good exchange surface
large surface area
thin membrane for a short diffusion path
efficient blood supply
being ventillated
define osmosis
the diffusion of water from a dilute solution to a concentrated solution through a partially permable membrane
what is active transport
moving substances from a dilite solution to a concentrated one, against the concentration gradient
what does active transport allow
mineral ions to be abosrbed into plant root hairs
sugar molecules to be absorbed from lower concentrations in the gut to the blood
