cytoskeleton - cell bio

what is the cytoskeleton

the cellular skeleton within the cytoplasm

what is the function of the cytoskeleton at the tissue level

muscle movement

functions of the cytoskeleton at the cell level

cell shape, movement, adhesion, mitosis

functions of the cytoskeleton at the sub cellular level

intracellular movement of organelles

location of sub-cellular organelles

organising cell polarity

endocytosis/phagocytosis

types of protein filaments in cytoskeleton

actin filaments, microtubules, intermediate filaments

protein actin filaments are made from

globular protein actin

actin filaments structure

two intertwined chains of actin

actin filaments example of function

muscle contraction

microtubules type of protein they are made from

alpha and beta globular protein tubular

microtubules structure

hollow rigid tubes

microtubules example of function

maintain cell shape

intermediate filaments proteins formed from

vimentin, cytokeratin, desmin, nuclear lamin

intermediate filaments structure

rope like structures

intermediate filaments example of function

structural support

microtubules main function

maintains cell shape

cell motility

organelle movement

chromosome separation during cell division

what are microtubules made up of

heterodimers - alpha and beta tubulin

what polarity is the alpha-tubulin exposed end

negative

what polarity is the beta-tubulin exposed end

positive

relation between centrosomes and microtubules

centrosomes act as the primary organisers of microtubules in animal cells

example of microtubules continuously breaking down and reforming

the mitotic spindle that separates chromosomes during cell division

why do microtubules need energy

GTP hydrolysis controls growth

what can microtubules be disrupted by + example

anti-cancer drugs i.e. taxol freezes cytoskeleton so they are unable to divide

what is structural support in microtubules important for

maintaining celullar shape and serves as a track for the movement of vesicles, cytoplasmic particles and organelles

motor proteins function

move things along microtubules

kinesins

move towards plus end of the microtubule away from the centrosome

dyneins

move towards the minus end of the microtubule towards the centrosome

what is the structure of the head of kinesins and dyneins

globular ATP-binding heads which bind the microtubule

what does the tail of motor proteins interact with

cargo, often through other proteins

why do motor proteins need energy

hydrolysis of ATP drives a shape change that results in the motor protein and cargo 'walking' along the microtubule

what do desmosomes specialise in

cell-cell adhesion

functions of intermediate filaments

structural support

anchoring of nucleus and other organelles

formation of nuclear lamina

stable

ALS (amyotrophic lateral sclerosis)

not allowing for proper distribution for nerve cell therefore have accumulation of neurofilamenmts in motor neurons which can cause paralysing

progeria

premature aging due to defective nucelar lamina, meaning nuclei can’t sustain their functions

cell cortex position in the cell

highly concentrated just beneath the plasma membrane

functions of cell cortex

provide support and mechanical strength

functions of actin filaments

muscle contraction

cell locomotion

cytoplasmic streaming

maintenance of animal cell shape

intracellular transport

similarity between actin filaments and microtubules

similar polarity and assemble/disassemble in similar manner

differences between actin filaments and microtubules

actin filaments are thinner, shorter and more flexible than microtubules

what happens when myosin interacts with actin filaments

undergoes a conformational change that drags myosin chains along actin filaments

where can actin filaments be found

under the cell membrane for support

where can intermediate filaments be found

structural layer of the membrane, basal membrane

where can microtubules be found

microvilli, flagella

process of phosphorylation

using ADP and adding a phosphate to create ATP for kinesines and dyeniens to power mechanical movements along the microtubule