cell division
interphase (cell cycle)
g1- protein synthesis, cells increase in size
s- dna is replicated
g2- cell continues to increase in size, energy stores are increased, duplicated dna is check for errors
mitotic phase (cell cycle)
mitosis- nucleus divides
cytokinesis- cytoplasm divides and 2 cells are produced
g0 phase (cell cycle)
when a cell leaves the cell cycle either temporarily or permanently
reasons: differentiation, damaged, age
g1 checkpoint
checks for:
cell size, nutrients, growth factors, DNA damage
g2 checkpoint
checks for:
cell size, DNA errors
mitosis + meisois
dna stays the same
dna halfs
prophase (mitosis)
chromosomes condense
spindle fibres form at the poles connecting the centrioles and centromeres
nucleolus and nuclear membrane break down
metaphase (mitosis)
spindle fibres pull chromosomes into position
chromosomes lineup along the equator (metaphase plate)
anaphase (mitosis)
spindle fibre shorten
centromeres split
chromosomes with only one chromatid move to opposite poles of the cell
telophase (mitosis)
spindles disappear
new nuclear envelope forms
chromosomes decondense
cytokinesis (mitosis)
animal- cytoplasm is pulled inwards forming a cleavage furrow, forming 2 new genetically identical daughter cells
plants- vesicles lineup on the metaphase plate, these vesicles fuse to form the new cell surface membrane
prophase I (meiosis)
chromosomes condense
nuclear envelope disintegrates
nucleolus disappears
spindle fibres reform
homologous chromosomes pair up forming bivalents
non-sister chromosomes entangle (chiasmata) the exchange DNA (crossing over) - first source of variation
metaphase I (meiosis)
homologous pears line up along the equator
the orientation of each homologous pair is random (independent assortment) - second source of variation
anaphase I (meiosis)
spindle fibres shorten separating the bivalents moving each chromosome in the homologous pair to the pole of the cell
telophase I (meiosis)
the chromosomes decondense
nuclear membrane reforms
cell undergoes cytokinesis
prophase II (meiosis)
chromosomes decondense
nuclear envelope disintegrates
nucleolus disappears
spindle fibers reform
metaphase II
chromosomes line up along the equator
independent assortment - third source of variation
anaphase II
spindle fibre shorten
centromeres split
chromosomes with only one chromatid move to opposite poles of the cell
telophase II
chromosomes decondense
nuclear membrane reforms
cell undergoes cytokinesis
erythrocyte (RBC)
flattened concave shape – large SA
reduced number of organelles - more space for haemoglobin
flexible - can fit through narrow capillaries
neutrophil (WBC)
multi-nucleated for production of antibodies
granular cytoplasm – lots of lysosomes
sperm cell
flagellem - swim
haploid – half genetic information
acrosome – contains enzymes to penetrate egg
mid-piece - lots of mitochondria
root hair cell
large SA - maximum absorption of water and mineral ions
lower epidermis of the leaf
contains guide cells which open and close stomata - allows H2O and O2 out and CO2 in
waxy cuticle - reduces water loss
squamous epithelium
thin tissues - cells are flat -> tissues only 1 cell thick
rapid diffusion (e.g. gas exchange)
ciliated epithelium
cells have cilia - waft mucus up trachea
goblet cells – release mucus to trap unwanted particles or pathogens
muscle
need to shorten (contract) to move bones
skeletal muscles
contains myofibrils - contain contractile proteins
totipotent (stem cells)
can become any type of cell
sourced from zygote within first 8-16 days
pluripotent (stem cells)
able to become all tissue types but not the whole organism
from the blastocyst (between embryos and fetus)
multipotent (stem cells)
can only become a small range of cells and tissue types
sorced from bone marrow