2.6-the actual worst Flashcards
what are the phases of the cell cycle in order starting from mitosis?
M, G0, G1, S, G2
what happens in G0?
- resting phase triggered during early G1 at the restriction point
- cells may undergo apoptosis, differentiation, or senescence.
what is senescence?
the loss of a cell’s power of division and growth
what is apoptosis?
programmed cell death
what’s an example of a cell with no G0 phase?
epithelial cells
what’s an example of a cell which remains in G0 for a long time or forever?
neurones
what happens during G1?
cells grow
organelles duplicate
transcription (rna is made)
proteins+enzymes required for S phase are synthesised, including enzymes for DNA replication.
what are the 2 main checkpoints of the cell cycle?
G1/S (also called restriction)
G2/M
what happens in S?
DNA replicates
once cell enters this phase, it’s committed to finishing the cycle
chromosomes duplicated into sister chromatids
why is the S phase rapid?
the exposed DNA base pairs are more susceptible to mutagenic agents so it being quick reduces the chance of spontaneous mutations.
what genes get replicated first?
housekeeping genes- those which are active in every cell.
what genes get replicated last?
genes that are normally inactive in specific cells.
what happens in G2?
special chemicals ensure the cell is ready for mitosis by stimulating proteins that will be involved in making the chromosomes condense and in formation of the spindle.
cells grow
what is the purpose of the checkpoints?
- prevent uncontrolled division that would lead to tumors
- detect and repair damage to dna (e.g. UV light)
what are the purposes of mitosis?
1) asexual reproduction
2) growth
3) repair
what are the phases of mitosis?
prophase metaphase anaphase telophase (cytokinesis)
what happens during prophase?
nuclear envelope breaks down
centriole divides into 2 daughter centrioles which move towards the poles of the cell
dna supercoils-chromosomes shorten and thicken
spindle starts to form
what happens during metaphase?
pairs of chromatids attach to spindle threads at equator
attach by centromeres
what happens during anaphase?
centromeres split
motor proteins walk along the tubulin threads +pull each sister chromatid towards opposite poles
what happens during telophase?
separated chromosomes reach poles
new nuclear envelopes form
what happens during cytokinesis generally?
cell splits in 2 so each new cell has a nucleus
what happens during cytokinesis in animal cells?
plasma membrane folds inwards and ‘nips in’ the cytoplasm (they just yeet apart)
what happens during cytokinesis in plant cells?
end plate forms where equator of spindle used to be
new cell wall made from golgi vesicles
new plasma membrane forms either side
how does differentiation change cells?
proportions of different organelles differs
shape of cell changes
some contents of cell changes
how are erythrocytes adapted to carry out their function?
- v small, large sa/v ratio» more o2 can diffuse across surface easily
- flexible, well developed cytoskeleton» allow enthrocytes to change shape so they can twist and turn as they travel through narrow capillaries
- most organelles lost to differentiation-no nucleus, mitochondria, or ER, and v little cytoplasm» more space for haemoglobin
what does a haploid cell have?
1 set of chromosomes, represented by the symbol n.
what happens in prophase 1?
chromatin condenses+each chromosome supercoils.
nuclear envelope breaks down+spindle threads form from the centriole
chromosomes come together in their homologous pairs.
each member of the pair consists of 2 chromatids.
crossing over occurs where non-sister chromatids wrap around eachother and may swap sections so alleles are shuffled.
(DISGUSTANG)
what happens during metaphase 1?
pairs of homologous chromosomes, still crossed over, attach along equator of spindle-each attaches by a spindle thread to their centromere.
the homologous pairs are arranged randomly-independent assortment.
The way they line up in metaphase determines how they will segregate independently when pulled apart during anaphase.
what happens during anaphase 1?
the members of each pair of homologous chromosomes are pulled apart-motor proteins drag them along the tubulin threads of the spindle.
the crossed over areas are now separate from eachother, resulting in swapped areas of allele shuffling.
what happens during telophase 1 in animal cells?
2 nuclear envelopes form around each set of chromosomes, and the cell divides by cytokinesis. there is then a short interphase where the chromosomes uncoil.
each new nucleus has half the original number of chromosomes, each chromosome consists of 2 chromatids.
what happens during telophase 1 in plant cells?
SIKE they don’t have 1- most go straight from anaphase 1 to prophase 2.
what happens during prophase 2?
if the nuclear envelopes have reformed, they now break down.
the chromosomes coil and condense, each consisting of 2 non identical chromatids-because of the swapping over.
spindles form
what happens during metaphase 2?
the chromosomes attach, by their centromere, to the equator of the spindle.
the chromatid of each chromosome are randomly arranged-the way they will be arranged will determine how the chromatids separate during anaphase-independent assortment.
YOURE SO CLOSE
YOU CAN DO IT
what happens during anaphase 2?
centromeres divide
chromatids of each chromosome pulled apart by motor proteins that drag them along tubulin threads of the spindle, towards opposite poles.
therefore the chromatids are randomly separated.
what happens during telophase 2?
nuclear envelopes form around each of the 4 haploid nuclei.
what happens during telophase 2 in animals?
2 cells divide to give 4 haploid cells
what happens during telophase 2 in plants?
a tetrad of 4 haploid cells is formed.
how are sperms adapted to their function?
1) loads of mitochondria to carry out aerobic respiration-ATP provides energy for the undulipodium.
2) small, long, v little cytoplasm, thin-move easily
3) acrosome-specialised lysosome, releases enzymes that digest the outer covering of the ovum, allowing the sperm head to enter.
4) haploid male nucleus
what is a guard cell?
in leaf epidermis, cells that surround stomata.
what Is a palisade cell?
closely packed photosynthetic cells within leaves.
how are palisade cells well adapted to photosynthesis?
1) long and cylindrical-pack together closely but w/a little space for air to circulate -C02 in these air spaces diffuses into the cells.
2) large vacuole-so chloroplasts are positioned near the periphery of the cell, reducing diffusion distance for CO2.
3) many chloroplasts to carry out photosynthesis
4) cytoskeleton threads and motor proteins to move chloroplasts when sunlight intensity changes.
how are root hair cells adapted to their function?
- hair like projection greatly increases surface area for absorption of water and mineral ions
- root hair cells have special carrier proteins in the plasma membrane in order to actively transport the mineral ions in.
what are examples of tissues?
squamous and ciliated epithelia, cartilage,
muscle, xylem and phloem
what is a tissue?
group of cells working together to perform a specific function/set of functions.
what are the 4 main tissue types in the body?
1) epithelial
2) connective
3) muscle
4) nervous
what does epithelial tissue do?
lines surfaces in the body like the skin, gut, airways, blood vessels, heart chambers, and walls of organs.
what blood vessels supply the epithelial tissue?
SIKE none, they get nutrients from diffusion from tissue fluid in the underlying connective tissue.
what are epithelial cells like?
- some are smooth, some have cilia or microvilli
- short cell cycles-divide 2/3 times a day to replace worn or damaged tissue.
what are the functions of epithelial cells (processes)
- protection
- absorption
- filtration
- excretion
- secretion
what are chondroblasts?
immature cells in cartilage
what is a chondrocyte?
cell which has secreted the matrix of cartilage and become embedded in it.
what are the 3 types of cartilage?
1) hyaline
2) fibrous
3) elastic
what does hyaline cartilage do?
forms the embryonic skeleton, covers the ends of long bones in adults, joins ribs to the sternum, found in the nose, trachea, and larynx.
where is fibrous cartilage found?
discs between vertebrae
knee joint
where is elastic cartilage found?
outer ear, epiglottis
what are the3 types of muscle?
1) skeletal
2) cardiac
3) smooth
what do xylem vessels do?
carry water and minerals from roots to all parts of the plant
what do phloem vessels do?
transfer the products
what happens at prophase?
nuclear envelope breaks down dna supercoils centrioles move to opposite poles spindle forms nucleolus disappears
how can you tell a photo is anaphase?
if the chromosomes are Vs.
HOMOLOGOUS CHROMOSOMES are independently assorted in which stage?
metaphase 1
sister CHROMATIDS are independently assorted in which stage?
metaphase 2
what gets independently assorted in metaphase 1?
HOMOLOGOUS CHROMOSOMES
what gets independently assorted in metaphase 2?
sister CHROMATIDS
how is genetic variation produced?
crossing over independent assortment x2 mutation random fertilisation non disjunction having 2 parents (duh)
what is non disjunction?
when the spindle doesn’t work properly, so homologous chromosomes don’t separate, so one more/less chromosomes eg downs
what does random fertilisation mean ?
gametes produced aren’t genetically identical, and it’s random when fertilisation happens, so there is a large number of possible allele combinations.
how does a mutation cause genetic variation?
mutation-changes dna base sequence-dna checks don’t detect change-different proteins.
what does the amount of variation depend on in crossing over?
amount of variation depends on distance between crossover points.
what are the features of stem cells that aren’t shown in specialised cells?
(dont make sense but just learn them)
- can specialise to variety of cell types
- ability to continue dividing
how do xylem vessels form from stem cells?
- differentiation
- cell elongation
- ligninification
- end walls break down
what is the part of the cell cycle that’s not mitosis called?
interphase
how would you describe normal body cells?
diploid
how would you describe sex cells?
haploid
what are homologous chromosomes?
matching chromosomes containing the same genes at the same places.
what is the difference between tumour tissue and normal tissue?
a greater proportion of cells are dividing in the tumour
why is the p53 gene important?
triggers 2 main checkpoints of cell cycle-tumour suppressor gene
how does meiosis produce genetic variation?
crossing over-prophase 1
independent assortment in anaphase 1 and 2
random fusion w other gametes
how can cells differentiate?
proportions of organelles changes
shape of cell changes
contents of cell change
what is the diameter of an erythrocyte?
about 7.5 micrometers
what is a root hair cell?
epidermal cell of young root w long hair like projections
what are tight junctions?
network of proteins, seal adjacent epithelial cells in a narrow band just beneath their apical surface.
what do desmosomes do?
form links between cells, provide a connection between intermediate filaments of the cell cytoskeletons of adjacent cells-give strength to tissues
what’s the difference between microvilli and cilia?
microvilli are extensions of the plasma membrane and cilia are hair like organelles.
what does connective tissue consist of?
a non living extracellular matrix which separates the living cells within the tissue and enables it to withstand forces.
what does the non living extracellular matrix of connective tissue consist of?
proteins (collagen and elastin)
polysaccharides (eg hyaluronic acid which traps water)
what are examples of connective tissue?
blood bone cartilage tendons ligaments
what is the larynx?
voice box
what is the outer ear called?
pinna
what is the epiglottis?
flap that closes over larynx when you swallow
where is smooth muscle found?
walls of intestine, blood vessels, uterus,urinary tracts
what is epidermal tissue?
like epithelial tissue in animals but in plants.
what does epidermal tissue consist of?
flattened cells that apart from guard cells lack chloroplasts+form a protective covering over plants.
what are the functions of roots?
anchorage in soil
absorption of mineral ions and water
storage eg of carbs
what are the functions of the stem?
support
holds leaves up to expose them to sunlight
transport of water, minerals, glucose
storage eg of carbs
function of flower?
sexual reproduction
what is regenerative medicine?
process of replacing, engineering or regenerating human cells, tissues or organs to restore or establish normal function.
what are bone marrow stem cells used for?
in bone marrow transplants to treat diseases of the blood, eg sickle cell and leukaemia, and immune system eg SCID (severe combined immunodeficiency)
IF DAMAGED DNA IS DETECTED AT A CHECKPOINT DOES APOPTOSIS HAPPEN
NO IT TRIES TO FIX IT
WHAT HAPPENS IF DAMAGED DNA IS DETECTED AT THE G2 CHECKPOINT
CELL CYCLE HALTED + CELL TRIES TO REPAIR DAMAGE.
WHEN DRAWING SHIT IN THE EXAM REMEMBER:
CONTINUOUS LINES
RULED LABELS
LABEL THE BASICS (eg cytoplasm)
LABEL THE COLOURS
WHAT ARE THE ROLES OF MITOSIS IN MULTICELLULAR ORGANISMS OTHER THAN GROWTH AND REPAIR
1) ASEXUAL REPRODUCTION
2) DEVELOPMENT OF BODY PLAN
3) PROLIFERATION OF WHITE BLOOD CELLS
4) PRODUCING GAMETES FROM HAPLOID CELLS
5) PRODUCTION OF NEW STEM CELLS.
HOW DO YEASTS DIVIDE?
BUDDING
DO YEASTS HAVE NUCLEI
YES
DO YEASTS HAVE RIBOSOMES
YES
WHEN A CELL IS BECOMING XYLEM WHICH CELL WALLS DOES IT LOSE
THE END CELL WALLS APPARENTLY
WHAT ARE THE DIFFERENCES BETWEEN THE CELL WALLS OF NORMAL CELLS AND OF XYLEM CELLS?
thicker ;
lignified ;
contain (bordered) pits
HOW DOES INDEPENDENT ASSORTMENT INCREASE GENETIC VARIATION
produces large number of allele combos.
HOW DOES CROSSING OVER INCREASE GENETIC VARIATION
chromatids will have new combination of alleles ;
WHY DOES BARK HAVE AIR SPACES
TO ALLOW O2 TO DIFFUSE IN FOR AEROBIC RESPIRATION
WHY DOES MEOSIS NEED 2 DIVISIONS
to half CHROMOSOME NUMBER!
to separate both chromosomes and chromatids
what’s the word ending in ‘potent’ that adult stem cells are?
multipotent.
