cell division Flashcards
what are the 3 stages of interphase ?
G1G0) s G2
what happens in G1
cells grow, transcription of genes, organelles duplicate, bio synthesis
what happens at S in interphase?
DNA replicates so that each chroma zone has 2 identical sister chromatids (a pair), genes replicate housekeeping then one in all cells
why is the S phase quick?
exposed DNA pairs are susceptible to mutation
what happens at G2 in interphase?
chemicals stimulate proteins that make chroma zones condense and will make the spindle form, cells grow
what happens during G0 phase of interphase?
a resting phase, apoptosis, differentiation, senescence
what are 4 purposes of a restriction points?
to prevent uncontrolled division, detect and repair damage to uv light, that the cycle cant be reversed and DNA is only replicated once
what is senesence?
when an aging cell has lost the ability to divide
what is apoptosis?
a programmed cell death
how is cell division helped to be regulated?
proto-oncogenes help regulate cell division by coding for proteins that help regulate cell growth and differentiation
how does a prokaryotic cell divide?
by binary fission, dna is replicated, 2 new loops of DNA are pulled to opposite ends of the cell and a cell wall forms, plasmids replicate
what is mitosis and what products does it make?
nuclear division that maintains the chromazone number the same. it produces genetically identical daughter cells which are diploid
what is mitosis used for in the body?
asexual reproduction, growth, tissue repair
what happens within cells in prophase?
chromazones condense (get shorter and thicker) as DNA supercoils,
nuclear envelope breaks down,
in animal cells only, centrioles separate to opposite ends of the cell,
tubulin threads form spindle fibres between centrioles
what happens during metaphase?
pairs of chromatids align along equator of cell and
spindle fibres are released and attach to the centromere of the chromazone
what is the centromere?
the point at which the 2 chromatids attach in a chromazone
what happens during anaphase?
spindle fibres retract and pull chromatids apart to the to poles, centromere goes first so it assumes a V shape
how do the spindle fibres get to the poles of the cell?
motor proteins walk along tubulin, hydrolysing ATP with every step taken
what happens during telophase?
chromazones at each pole lengthen and get thinner
spindle fibres disintergrate and nucleus reforms but are all still in 1 cell
what happens during cytokynesis?
cytoplasm splits in two because myosin and actin filament ring contact to cleave cell in two
describe what happens in plant cells during cytokynesis?
an end plate forms where equator of spindle was, new plasma membrane and cellulose cell wall are laid down either side of the end plate
what does meiosis produce?
4 haploid daugther cells that are geneticaly different to each other
state 2 mportantces of meiosis
increases genetic variation, produces haploid gametes which allow for sexual reproduction
state 4 ways meiosis increases genetic variation?
crossing over of non sister chromazones- in prophase 1
independant assortment= metaphase 1
mutations
random fusion of gametes
how does crossing over increase genetic variation?
non sister chramazones wrap around each other and swap sections so genes and alleles get shuffled
when does crossing over occur ?
prophase 1 initially
what is indpendant assortment?
when homologous pairs are arragnged randomly along equator of the cell
when does independant assortment happen ?
metaphase 1 and anaphase 2
how does independant assortment increase genetic variation?
homologous pairs get separated so one of each pair ends up in each daughter cell which creates a large number of possible combinations and therefore increases genetic variation
how does a haploid gamete create a diploid cell?
undergo fission with another haploid gamete and creates a further genetically different diploid cell which undergos mitosis to form and embryo
what are homologous chromazones?
one maternal and one paternal, they carry same genes
what is a non-sister chromatid?
when two different pairs chromazones cross their chromatids so the crossing is between 2 chromazones that are not the same as each other
why do multicellular organisms need differenciation in cells?
they have a small sa/vol ratio so most cells arnt in contact with external environment so oxygen and carbon dioxide cant diffuse in therefore a diverse range of cells are needed to do specific functions
state how cells differentiate ?
genes that are needed to carry out specific functions are switched on and genes that are not needed are switched off
what 3 things will happen to cell as a result of differentiation?
proportions of the organelles will differ from other cells,
shape of cell will change,
contents of cell will change
what is the function of erythrocytes?
to carry oxygen from the lungs to repiring cells
how does the stucture of erythrocytes link to the function? 3 points
they are very small, therefore have a high sa/v meaning oxygen can diffuse across all regions of cell.
they have a well developed cytoskeleton therefore is very flexible, this allows them to change shape and travel through narrow cappilarys.
most organells were lost at differenciation therefore allows room for haemoglobin to carry oxygen
what is the function of a neutrophil?
ingest invading pathogens by phagocytosis
how does structure of a neutrophil relate to its function?
has a multilobed nucleas due to flexibility, therefore it can get through capilaries and form cytoplasmic projections to engulf pathogens
large number of lysomomes, in order to digest invading pathogens by phagocytosis
what is the function of spermatozoa?
to fuse with ovum in reproduction, initiate development of the embryo, pass on paternal genes
how does the sructure of spermatozoa relate to its function?
head contains haploid nucleas to pass on genes.
acrosome contains digestive enzymes to digest the ovum outer layer.
mid-peice is packed with mitochrondria to release energy to propel the undulipodim
what is the scientific name of the sperms tail?
undulipodium
what is the function of epithelial cells?
move substance across the surface of tissue
how does epithelial cells structure relate to function ?
have cilli which beat in a co ordinated movement to move material along
what is a goblet cell?
secretes mucus to trap microoganisms and dust and preventing them from entering vital organs
what is a squamous epithelial cell?
flattened in shape on a basement membrane to provide a surface covering
how does the sructure of squamous epithleial cells relate to its function?
permeable to allow easy diffusion of gases, has a thin cross-section to reduce distance that substances diffuse across so it shortens the diffuion distance and speeds up diffusion
how are palisade cells adapted for photosynthesis?
long and cylindrical- can densly pack together with space between them for gases to circulate and diffuse into cells, it also allows light to penetrate deeper for max light absorbtion.
contain many chloraplasts - to maximise max light absorbtion for photosynthesis.
they contain cytoskeleton threads and motor proteins to move chloraplasts where sunlight is most intense
what is the function of guard cells?
control opening of stomata to regulate water loss and gas exchange
how do guard cells swell up?
the ATP produced by chlorplasts in the guard cells is used to activly transport potassium ions in from surrounding cells therefore lowering water potential and water will now enter in via osmosis so the cell is now turgid
how are guard cells suited for their function?
cellulose cell wall on outer edge is more flexible than the inner edge so that when swollen it creates a shape with a hole in the middle to allow gases through
what role do root hair cells play?
increase surface area for water and mineral ions to diffuse in, a smineral ions diffuse in, it will lower the water potential and cause water to enter.
they have carrier proteins to activley transport mineral ions into the cell
what is a tissue?
group of cells that work together to perform a specific function
what are the 4 types of animal tissue?
muscle, nervous, epithelial and connective
what is the general role of epithelial cells?
to line free surfaces
how are cells arranged in epithelial tissues ?
close together and form continous sheets, adjacent cells are bound together by lateral junctions and desmosomes
what type of surface can an epithelial cell have?
smooth, with cillia or microvilli
explain the length of the epithelial cell cycle
short cell cycle because they tend to be in places that is particularly abrasive so need to be replaced
what are cillia?
hair like projections which beat together to move substances
what are microvilli?
extensions of the cytoplasm at the end of the cell to increase surface area
what are the 5 functions of epithelial cells?
protection, absorbtion, filtration, excretion, secretion
give 3 examples of where epithelial tissues are found
bronchiols in lungs, small intestine and falopian tubes
what is the structure of connective tissue?
there is a matrix that separates living cells that make up the tissue. the matrix contains elastin and collogen and polysaccharides
what is the function of connective tissue?
to withstand forces in high pressured mechanical areas
where is connective tissue found?
blood, bone, cartilage, tendons, ligaments and skin
what are chondrocytes?
less active cells in cartilage that maintain the matrix
what are chrondroblasts?
immature versions of chrondrocytes that divide and secrete the extracellular matrix
when do chrondroblasts mature?
when the matrix has been synthesised
what are the 3 types of cartilage?
Hyaline, fibrous, elastic
where is hyaline cartalage found?
covers ends of long bones, joins ribs to sternum, forms C shaped rings of cartalage in tracea
where is fibrous cartilage found?
acts as a shock absorber discs between vertibrae and joints
where is elastic cartilage found?
in outer ear and epiglottis
what is the function of muscle tissue?
allow movement by contracting muscles
what is the structure of musle cells?
well vascuaralised,elongated and contain myofilaments made of actin and myosin they are fibres
what are the 3 types of muscle tissue?
skeletal, cardiac, smooth
what are skeletal muscles?
they are connected tissue sheets and joined to bone by tendons, they contract and move the bone
what is cardiac muscle?
makes up walls of the heart and allows heart to beat
what is smooth muscle?
makes up walls or components of the body
state 4 places smooth muscle is found
walls of intestine, blood muscles, uterus and urinary tracks
what are cambium cells?
meristemic cells that divide by mitosis into xylem or phloem cells
where are cambium cells found?
located between the xylem and phloem tissue in the stem and root
which edge of the cambium differenciates into xylem cells?
inner edge
which edge of the cambium differenciates into phloem cells?
outer edge
what is the structure and function of meristematic cells?
thin walls and a very small vacuole in order for them to divide easily and not many chloraplasts
what is the structure of a parenchyma cell?
thin walls and intercellular air space
what is the function of parenchyma cells?
it is a packing tissue that fills spaces between other spaces, storage and allows for gaseous exchange
what is the name of the cell like parenchyma but with chlorosplasts?
chlorenchyma
do parenchyma have chloraplasts?
no
do collenchyma have chloraplasts?
yes
do sclerenchyma have chloraplasts?
no
what is the structure of collenchyma?
thickened cornersand unevenly thick cellulose cell walls
what is the function of collenchyma?
strengthens vascular bundles and outer parts of stems and allows flexibilty
what is the structure of sclerenchyma?
evenly thick walls that are lignified and form a uniformed pattern
what is the function of sclerenchyma?
strengthen stems and add rigidity
what is a totipotent stem cell?
the cell that is found in the zygote which can differenciate into any body cell
what is a pluripotent stem cell?
stem cells are found in early stages of an embryo that are able to express all genes and divide by mitosis and differenciate into specialised cells
what is a multipotent stem cell?
an adult stem cell, it differenciates into one type of cell
what is a source of totipotent stem cells?
from the umbilical cord or placenta
what is a source of pluripotent stem cells?
can be harvested from unused embryos from IVF
how can stem cells be used for repairing damaged tissues ?
stem cells from bone marrow can be made to develop new tissue cells to treat diseases of the organ
what is an induced pluripotent stem cell?
developed in labs by reprogramming differenciated cells to switch on certain genes that are key for becaoming undifferenciated
how can stem cells be used to treat brain diseases?
stem cells directed to become nerve cells which would be used to repair spinal cord
what is a source of adult stem cells?
found in developed tissues that are already specialised (bone marrow)
how can stem cells be used for transplants?
stem cells used to produce a bioscaffold of an organ then a specific organ used for transplanting
how can stem cells be used for research into developmental biology?
stem cells used to create a human tissue then we can do research on it without the ethical issues of human participants
