what is the cell cycle a process of?
the process that all body cells in multicellular organisms use to grow and divide
what does interphase involve?
cell growth and dna replication
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what is the cell cycle a process of?
the process that all body cells in multicellular organisms use to grow and divide
what does interphase involve?
cell growth and dna replication
what does m phase involve
mitosis and cytokinesis
define mitosis?
nuclear division
define cytokinesis?
cytoplasmic division
what 3 separate growth stages is interphase separated into?
G1, S and G2
what is the cell cycle regulated by?
checkpoints
what do checkpoints help to ensure?
to ensure that it is ok for the cell cycle to continue
what is mitosis necessary for?
the growth of multicellular organisms and repairing damaged tissues
is mitosis sexual or asexual reproduction?
asexual reproduction
what division stages make up mitosis?
prophase
metaphase
anaphase
telophase
what process comes before mitosis in the cell cycle?
interphase
what happens at interphase?
the cell prepares to divide
its dna is unravelled and it is replicated
organelles also replicated so it has spare ones
atp content increases
what happens at prophase?
chromosomes condense and become visible
centrioles start moving to opposite ends of the cell forming a spindle
the nuclear membrane breaks down and chromosomes are free in the cytoplasm
what happens at the metaphase?
chromosomes attach to the spindle and line up along the middle of the cell
at the metaphase checkpoint the cell checks that all the chromosomes are attached to the spindle before mitosis can continue
what happens at anaphase?
the centromeres divide separating each pair of sister chromatids
spindles contract pulling chromatids to opposite ends of the cell
what happens at telophase?
the chromatids reach the opposite poles of the spindle
they uncoil and become long and thin again
they are now called chromosomes again
a nuclear envelope forms around each group of chromosomes so there are now 2 nuclei
what happens in cytokinesis?
the cytoplasm divides into 2 daughter cells which are genetically identical to the parent cell and eachother
how to view chromosomes under a microscope?
prepare a squash slide of plant root cells
this then makes chromosomes easier to see after they have been stained
how is a zygote formed insexual reproduction?
two gametes ( an egg and a sperm) join together at fertilisation to form a zygote
define meiosis?
a type of cell division that happens in the reproductive organs to produce gametes
define haploid cells?
cells with half the number or chromosomes
what 2 divisions does meiosis invlovle?
meiosis I and meiosis II
what 4 stages is meiosis split into?
prophase
metaphase
anaphase
telaphase
what stage does meiosis begin with?
interphase
what happens in the interphase?
dna unravels and replicates to form double armed chromosomes called sister chromatids
what happens in prophase I?
the chromosomes condense then get shorter
they arrange themselves into homologous pairs and cross over
centrioles move to opposite ends of the cell forming spindle fibres
nuclear envelope breaks down
what happens in metaphase 1?
the homologous pairs atatch o the spindle fibres by their centromeres
they line up across the centre of the cell
what happens in anaphase 1?
the spindles contract separating the homologous pairs
one chromosome goes to each end of the cell
what happens in telophase 1?
cytokinesis occurs
2 haploid daughter cells are produced
what happens in anaphase II?
the pairs of sister chromatids are separated
each new daughter cell inherits one chromatid from each chromosome
4 genetically different daughter cells are produced
these are gametes
in prophase 1 what takes place after the homologous pairs of chromosomes come together and pair up?
the chromosomes twist around each other and pair up
the chromosomes contain the same gene but have a different combination of alleles
define stem cells?
undifferentiated cells which can become specialised to carry out a particular function
how can stem cells in early embryos develop?
into any type of human cell
how can stem cells in adults develop?
into a limited range of human cells
what is the name of the process by which a stem cell becomes specialised for its job?
differentiation
what can stem cells be used for in humans?
to replace damaged cells
make new skin cells
make new blood cells
what can stem cells be used for in plants?
needed to make new shoots and roots throughout their lives
can differentiate into various tissue e.g phloem and xylem
what are erythrocytes also known as?
red blood cells
what are neutrophils also known as?
white blood cells
what can stem cells within bone marrow differentiate into?
blood cells
where are stem cells found in plants?
the meristems
how are neutrophils specialised for their function?
flexible shape allows them to engulf pathogens or foreign particles
lysosomes within their cytoplasm contain digestive enzymes to break down engulfed particles
how are erythrocytes specialised for their function?
biconcave disc shape provides a large surface area to volume ratio for gas exchange
no nucleus so more room for haemoglobin
how are epithelial cells specialised for their function?
cilliated epithelia in airways have cilia to beat particles away
squamous epithelia in lungs are very thin for efficient diffusion for gases
how are sperm cells specialised for their function?
flagellum to swim to egg
lots of mitochondria to provide energy to swim
acrosome contains digestive enzymes to enable sperm to penetrate surface of egg
how are palisade mesophyll cells specialised for their function?
how are root hair cells specialised for their function?
contain many chloroplasts to absorb lots of sunlight
thin walls so carbon dioxide can easily diffuse into the cell
large surface area for absorbtion
thin permeable cell wall for entry of water and ions
cytoplasm contains lots of mitochondria to provide energy for active transport
how are guard cells specialised for their function?
what are squamous epithelium cells and where are they found?
a single layer of flat cells lining a surface
found on alveoli and lungs
what are ciliated epithelium and where are they found?
a layer of cells covered in cilia
found on surfaces where things need to be moved
in trachea for instance where cilia waft mucus along
define muscle tissue?
bundles of elongated cells called muscle fibres
state the 3 different types of muscle tissue?
smooth muscle- found in lining of stomach wall
cardiac muscle- found in heart
skeletal muscle- you use to move
what is cartilage and where is it found?
a type of connective tissue found in the joints
also supports ears nose and windpipe
what are the 2 types of plant tissue?
xylem tissue
phloem tissue
function of the xylem?
transports water and minerals up the stem
supports the plant
function of phloem?
transport sugars around the plant and arranged into tubes
what do organs work together to form?
organ systems