Cell: nucleus Flashcards
what is chromatin
highly extended and elaborate nucleoprotein fibres are called crhomatin
theyre like a network
tey contain dna and histone and non histone proteins and rna
what is chromosome
these are thread like structures formed during cell divison. condensed form of crhomatin
what is the chromatid
these are the arms of the chromosome
what is the centromere
it is the disc shaped primary constriction that divides the chromosome into two arms.
what are kinetochores
In the centromere region, there are two proteinaceous disks called kinetochores which are for attaching the chromosome to the spindle fibres during cell division.
what are satellites
a few chromosomes have non-staining secondary
constrictions at a constant location. This gives the appearance of a small
fragment called the satellite.
types of chromosomes
metacentric: centromere position at the centre hence dividing chromosome into to two equal arms on either end
sub metacentric: centromere position lslight above centre, hence forming one slightly shorter am and one slightly longer arm
acrocentric: centromere places very close to one end( much above the centre), to form a very short arm and a very long arm
telocentric: centromere placed at the terminal end forming one very long arm
what are cilia and flagellum
Cilia (sing.: cilium) and flagella (sing.: flagellum) are hair-like outgrowths
of the cell membrane. Cilia are small structures which work like oars,
causing the movement of either the cell or the surrounding fluid. Flagella
are comparatively longer and responsible for cell movement. The
prokaryotic bacteria also possess flagella but these are structurally
different from that of the eukaryotic flagella
what is the outer structure of flagellum
what do cilium and flagellum arise from
It consists of nuclear membrane. The central space/ core is called axoneme.
Both
the cilium and flagellum emerge from centriole-like structure called the
basal bodies.
what does axoneme consist of
It consists of microtubules radially arrranged in the form of 9 doublets in the periphery and 2 central microtubules, this is called the 9+2 array
9 doublets are connected by interdoublet bridges(linkers)
The central chromosomes are also connected by a bridge and encolsed in a protein sheath
how are the radial microtubules and central microtubules connected?
Each microtubule doublet is connnected to the central microtubules by means of radial spokes.
Dynein arms are present in one microtubule of each doublet which cause sliding movements to give rise to synchronous movement.
what are centrioles
centrioles are non membrance bound celll organelle which are placed in an apparatus called the centrosome. They centrioles are arranged perpendicular to each other, each having a cartwheel like structure. They are surrounded by amorphous pericentriolar
materials.
what is the microtubules of centrioles
made up of nine evenly spaced peripheral fibrils of tubulin protein. Each
of the peripheral fibril is a triplet.The adjacent triplets are also linked.
The central part of the proximal region of the centriole is also proteinaceous
and called the hub, which is connected with tubules of the peripheral
triplets by radial spokes made of protein.
what is the function of centriioo
The centrioles form the basal
body of cilia or flagella, and spindle fibres that give rise to spindle
apparatus during cell division in animal cells.
what are microbodies
membrane bound vesicles filled with enzymes which are involved in various metabolic pathways.
Peroxisomes: converts lipid into carbohydrate
Glyoxysomes: metabolism of hydrogen peroxide, using catalase
