1.1 Cell Ultrastructure Flashcards
What is tissue?
consists of a combination of cells - often similar structure and origin - and an extracellular matrix (ECM) which work together to person a specialized function
how many tissue types are there in the human body?
4
what are the 4 tissue types in the human body?
muscle, nerve, epithelial, connective
put these in the correct order of size and place/order:
organ system, organ, differentiated cell types, organism, tissues
differentiated cell types, tissues, organ, organ system, organism
define limit of resolution.
the smallest distance at which 2 objects can be distinguished as 2 separate entities
what does multicellular state of a cell allow?
cells to differentiate and specialise so one cell may look very different from another
why can organelles be detected in an electron microscope and not light?
bcs electron has higher resolving power ∴ lower limit of resolution
state the relationship between limit of solution and wavelength
limit of resolution is proportional to the wavelength used by the microscope system
explain the reasoning behind why electron microscope has smaller limit of resolution compares to light microscopy
light microscope uses visible light (which has wavelength of 0.4-0.7 µm (micrometer)) and has theoretical limit of resolution of 0.2 µm, WHEREAS, em uses electrons (where at 100,000V, wavelength is 0.004nm aka 0.000004µm)
in electron microscopy, what does the wavelength depend on?
the accelerating voltage used
what is the limit of resolution of scanning electron microscopy (SEM)?
~10nm
what is the practical limit of resolution of transmission electron microscopy (TEM)?
~2nm for biological specimens
what is the difference between SEM and TEM?
SEM creates an image by detecting reflected or knocked-off electrons, while TEM uses transmitted electrons (electrons that are passing through the sample) to create an image. As a result,
compare SEM and TEM
TEM offers valuable information on the inner structure of the sample, while SEM provides information on the sample’s surface and its composition.
compare the complexity of eukaryotic cels and prokaryotic cells.
eukaryote are more complex than prokaryotes ∴ require segregation if their contents into different compartments to allow orderly completion of biochemical reactions that happen within them
how do eukaryotes compartmentalise?
numerous bilipid membranes that form an interconnecting network throughout the cell
what is the structure that all cell membranes have?
phospholipid molecules arranged as a bilayer
what is a property of phospholipids?
they are amphipathic
define amphipathic
a molecule which has both hydrophilic and hydrophobic parts
what happens to phospholipid in aqueous solution?
phospholipid molecules spontanouelsy form bilayers
what structure does phospholipid bilayer have under TEM?
trilaminate structure (2 hydrophilic, polar heads are a layer EACH and the inside hydrophobic tails are 1 layer)
what does the fluid mosaic model show?
many proteins float freely within the bilayer
2 examples of what the proteins do in the bilayer
some interact with the cytoskeleton, and many are conjugated with short polysaccharide chains and are said to be glycosylated
what is the outermost bounding membrane called and how big is it?
plasma membrane or plasmalemma and is ~9nm thick
what are the glycocalyx?
glycoproteins and glycoproteins projecting outwards from the plasma membrane
what are 7 functions of the plasma membrane?
- intercellular adhesion and recognition
- signal transduction
- compartmentalisation
- selective permeability
- transport of materials along cell surface
- endocytosis
- exocytosis
mnemonic to remember the 7 functions of plasma membrane?
sectise or silly Eleanor’s cat tore into sam’s ear
what does the nucleus contain?
DNA, nucleoproteins and RNA
what does the TEM show in the nucleus?
an electron-fence heterochromatin (where DNA and associated nucleoprotein is not active in RNA synthesis) and electron-lucent euchromatin (less condensed state so accessible for RNA synthesis)
what is the shape of the nucleus for both inactive and active cells?
inactive = small nuclei containing condensed heterochromatin
actively transcribing cells = relatively large nucleus containing more euchromatin
what cells are nucleus not present in?
erythrocytes (RBC), stratum corner cells (outermost layers of skin) and lens fibre cells
define nucleolus?
one or more electron-dense structures within nucleus
function of nucleoli (pl nucleolus)?
sites of ribosomal RNA synthesis for ribosome assembly, are prominent in actively biosynthetic cells (eg neurons)
what happens to ribosomal subunits for ribosome assembly?
exported from nucleus
when are nucleoli present?
during interphase ∴ disappear during cell division
define nuclear envelope
consisting of a double layer of membranes bounding the nucleus
what is on the outer layer of the nuclear envelope?
RER. the perinuclear cisterns between the inner and outer nuclear membrane is continuous with the RER
what does nuclear envelope contain?
nuclear pores
define endoplasmic reticulum
interconnecting membranes, vesicles and cistern (flattened sacs) that are continuous throughout the cytoplasm. literally “inside plasma network”
what is RER?
when ribosomes are attached to outer surface. it is extensive in cells actively synthesizing protein
what do the ribosomes on RER do?
generate proteins that associate w RER and are destined for export or for inclusion in lysosomes or cell membranes
what do free ribosomes in the cytoplasm do?
synthesized proteins destined for cytosol or mitochondria
what is SER?
when ER not associated with ribosomes. cistern not as flattened as RER, normally less extensive and distributed throughout the cytoplasm.
functions of SER?
primarily in lipid biosynthesis, steroid production, calcium storage (in muscle) and intercellular transport
what is Golgi apparatus?
saucer shaped stacks of cisternae
2 other names for Golgi apparatus?
Golgi complex, Golgi body
how is Golgi body formed?
vesicles bud off from RER and fuse with convex forming face of Golgi body
1 property of Golgi body?
have polarity ∴ proteins migrate from convex to concave part of stack
functions of Golgi?
sort, concentrate, package and modify proteins synthesized by RER
how are lysosomes made?
vesicles containing different proteins leave the maturing, concave face of Golgi
how do secretory vesicles work?
condense into secretory granules and release contains at the cell surface by exocytosis
define lysosome
membrane bound vesicle that contain powerful digestive/hydrolytic enzymes at pH 5
how many lysosome enzymes are known? name a few.
~40. nucleases, proteases, glycosideases, lipase, phosphatases, sulfates, phospholipases
property of lysosomal membrane proteins?
highly glycosylated for protection from these enzymes
where are primary lysosomes formed and what’s their shape?
generated by Golgi apparatus. highly diverse in shape, usually dense, spherical or oval
function of primary lysosomes?
fuse with endoxytosed, membrane-bound vesicles (eg: phagosomes, endoscopes) with autophagosomes or with excess secretory product to form secondary lysosomes in which contents are degraded
what are secondary lysosomes?
digestive vacuoles eg: phagolysosome
define autophagosomes.
defund organelles encircled by ER
what are residual bodies?
remnants of phagolysosomes that contain indigestible material (can form lipofuscin granules: imp. in aging, as age no. of granules ^)
what happens if residual bodies aren’t excreted by the cell?
remain as lipofuscin granules (which is a cellular characteristic of aging)
what are peroxisomes?
small (0.5-1um diameter) spherical, membrane bound organelles containing enzymes involved in oxidation of several substrates, particularly β-oxidation of very long chain fatty acids (C18 and above). contain granular matrix and are bound by single membrane
how do peroxisomes replicate and what’s 1 feature of it?
self replicating but have no genome of their own ∴ all their proteins must be imported
where are peroxisomes present?
all cells, especially kidney tubules and liver parenchymal cells that detoxify toxic molecules that enter enter bloodstream
function of peroxisomes?
major sites of oxygen use and H2O2 (hydrogen peroxide) production
how do peroxisomes produce H2O2?
break down organic molecules by the process of oxidation to produce hydrogen peroxide -> which is quickly converted to oxygen and water.
what is the equation of peroxisomes?
RH2 + O2 -> R + H2O2
what is the clinical function of peroxisomes?
produce cholesterol and phospholipids found in brain and heart tissue. A peroxisome protein is involved in preventing one cause of kidney stones.
define catalase
common enzyme found in nearly all living organisms exposed to oxygen (eg: bacteria, plants, and animals) which catalyzes the decomposition of hydrogen peroxide to water and oxygen
what does catalase do with H2O2?
uses H2O2 generated, to oxidise other substances including phenols, formic acid, formaldehyde and alcohol
catalase’s equation to oxidise alcohol?
CH3CH2OH + H2O2 -> CH3CHO + 2H2O
shape of mitochondria?
variable shape, from spherical to elongated oval shape
structure of mitochondria?
double membraned with inner membrane thrown into distinct folds (cristae) that are usually lamellar (although appear tubular in cells engaged in steroid synthesis)
function of mitochondria?
generation of energy-rich ATP molecules by oxidative phosphorylation
function of ATP?
store energy needed by cell
what are the substrates of ATP?
glucose and fatty acids
where is ATP found?
a lot found in liver and skeletal muscle cells ~2000 cells in liver
what does mitochondria matrix contain?
enzymes of Krebs and fatty acid cycles, DNA, RNA, ribosomes and calcium granules
state the replication of mitochondria
can divide autonomously bcs have their own genetic information
explain the relationship between mitochondria and bacteria
mitochondria DNA, ribosomes and division is similar to bacteria & endosymbiosis theory
explain the endosymbiosis theory
thought that mitochondria originate from bacteria that developed a symbiotic relationship with primordial eukaryotic cells in the distant past
what is the female lineage of mitochondria?
one inherits all their mitochondria from their mother
what is a cytoskeleton?
a complex, dynamic network of interlinking protein filaments present in the cytoplasm of ALL cells (incl bacteria and archaea) It extends from the cell nucleus to the cell membrane
main 3 components of cytoskeleton?
microfilaments (actin-based fibres, 5nm diameter), intermediate filaments (composed of diff proteins, 10nm in diameter) and microtubules (tubulin-based tubules, 25nm diameter)
role of cytoskeleton?
maintaining and/or changing cell shape.
4 things cytoskeleton provides?
- structural support for plasma membrane and cell organelles
- means of movement for organelles, plasma membrane and other cytosol constituents
- locomotor mechanisms for amoeboid movements (eg lymphocytes) and for cilia and flagella
- contractility in cells of specialized tissues (eg muscle)
give an example of a microfilament
a core of actin filaments allow intestinal microvilli to maintain their shape
what is the size of intermediate filaments?
10-12 nm diameter
what do intermediate filaments do in epithelial cells?
form a tough supporting meshwork in cytoplasm and are anchored to plasma membrane at strong intracellular junctions (desmosomes)
where are microtubules found?
sites where structures in cells are moved (eg in elongated cell processes such as nerve fibres, the mitotic spindle and the cores of cilia and flagella)
1 function of microtubules?
motor proteins (dynein and kinesin) can attach to organelles and move them along the microtubules (eg the movement of chromosomes along mitotic spindle), eg: neurotransmitters synthesized in the nerve cells are shuttles to the axon terminals via microtubule network
what are micortubules?
comprised of tubulin protein, specifically 13 α and β tubular subunits which wind together and polymerase to form the wall of the hollow protofilament.
structure of microtubules? it’s link to polymerization?
one face exposes β subunits ( + end) and other face exposes α subunits ( - end). polymerization can occur from both sides but is more rapid from + end.
in which types of cells are lysosomes generally most abundant?
phagocytic cells (eg macrophages)
what is autophagy?
process which malfunctioning cellular components are broken down for re-use
why is autophagy important in caner progression?
cancerous growth tend to be poorly vascularized. autophagy allows cancer cells to survive in low-nutrient environments by re-using cellular substrated
what is the brief cellular basis of tay-sachs disease?
a failure to breakdown membrane glycosphingolipids through the loss of hexosaminidase. leads to accumulation of gangliosides in nerve cells, leading to loss of cellular function
what are 5 features of autosomal recessive diseases?
- affects males and females in roughly equal proportions
- can skip generations
- people can be carriers of the disease
- both parents of an affected individual have to be carriers
- a child born to 2 carried has a 1/4 change of being affected
if theres family history of tay-sachs disease, what services could be offered to parents at earlier stage?
parental diagnosis (eg: chorionic villus sampling). genetic counseling prior to pregnancy.
what tissue has a brush border when seen under a microscope?
intestinal epithelia
what is a brush border?
a microvilli-covered surface of simple cuboidal and simple columnar epithelium found in different parts of the body
what is the size of microvilli?
1 micrometres (um) in length and ~90 nm in diameter
why are there different resolutions or microscopes?
resolution relates to the wavelength of the light/electrons that is being used. in light microscope, the wavelength is much larger than electron microscope
explain the resolution of light microscopes.
the range of visible light is going from 380nm to 700nm ∴ are limited by the physical properties of light itself
explain the resolution of electron microscopes.
the wavelength of electrons is much smaller and that is a function of the potential difference applied across the system. eg: at 100 kV in a typical e- microscope there is a wavelength of 0.004nm
why is there is a difference in the theoretical limits and practical limits of microscopy?
related to the actual physical constraints of the system itself: constraints of wavelength of light and of electrons themselves. BUT also relates to how thinly can cut a specimen and quality of lenses using
what is the limit of resolution of the human eye?
0.25mm
what is the practical limit of resolution of light microscope?
200nm
what is the practical limit of resolution of TEM?
0.1nm
what is the relative size (diameter) of mammalian cells?
10-100 um
what is the relative size of nucleus?
~6um
what is the relative size of mitochondrion?
~0.5-2 um
what is the relative size of ribosome?
~20-30nm
why can we see microvilli brush border with TEM but not LM?
bcs microvilli have diameter of ~90nm and ~1um in length and TEM practical limit of resolution is 0.1nm whereas LM practical limit of resolution is only 200nm
what do membranes allow?
compartmentalisation of every structure within the cell
where is plasma membrane found?
in every cell including prokaryotes
what are prokaryotes? give an example
cells without nucleus’. eg: bacteria
how are eukaryotic cells compartmentalized?
by internal membranes
what organelles does a eukaryotic cell contain?
nucleus, endoplasmic reticulum, Golgi apparatus, mitochondria, lysosome, cytosol, endoscope, peroxisome, free polyribosomes
why are organelles important for the functioning of the cell?
allow much more complex biochemical reactions to take place, allows individual cell biochemical conditions to exist within these areas. (eg: in lysosome theres low pH of 5 whereas cytosol has a neutral pH of 7) ∴ allowing specialized reactions to take place in cells themselves
what property dictates the function of the particular organelle? give an example
the area of membrane. eg: RER accounts for 60% of the total membrane of the cell ∵ it is the organelle responsible for producing proteins and protein production is important within any cell BUT especially for cells that secrete proteins as their function
what happens to phospholipid molecules when they are in oil?
spontaneously from a phospholipid monolayer and a micelle where oil is inside the circle and water is outside.
what happens to phospholipid molecules when they are in water? where are these present?
form a phospholipid bilayer which is the structure of the plasma membrane and all the internal double membranes of the organelles within a cell
what is the structure of a phospholipid?
there is a non polar tail and a polar head. it has a cis-double bond
what is the polar head of the phospholipid molecule composed of?
a glycerol, phosphate bridge and a nitrogenous compound (which varies between diff phospholipids). nitrogenous compound eg: choline, inositol
what does the nitrogenous base on the phospholipid head do? give an example. how is it attached?
it gives the phospholipid molecule its property, eg: cell signaling. it fuses onto the phosphate bridge.
what does a cis-double bond look like in a phospholipid?
a double bond which forms a kink in the tail of the phospholipid
why is the cis-double bond important?
it allows for movement within the membrane itself. if there was no double bond, there would be too much packing and the phospholipids would be too close together
what structure does the membrane have?
a phospholipid bilayer
what other components are there on the phospholipid bilayer?
carbohydrate chains linked to individual proteins to form glycoproteins, individual carbs that link to lipids to form glycolipids, integral proteins, peripheral proteins, cholesterol
what are the glycoproteins and glycolipids on the membrane collectively known as?
a glycocalyx
what is the role of extracellular glycolipids?
cell recognition, eg: blood group antigens
what do integral proteins form?
channels
describe the connectivity of peripheral proteins to the membrane?
loosely connected
what is the role of cholesterol in double membrane?
membrane fluidity
what is the polarity of cholesterol in double membrane?
amphipathic
what happens to the components of the plasma membrane within diff cells? give an example
they differ within different cells, eg: in myelin in neuron, 76% of myelin is composed of lipid whereas the membrane of mitochondria is composed of 76% protein
how does the components of myelin relate to its function?
myelin sheath is important for insulating the neuron and the insulting properties are provided by the lipid
how does the components of mitochondria membrane relate to its function?
the protein in the membrane of mitochondria assists in its function of ATP synthesis
what property is key to the fluid mosaic model?
fluidity
how is fluidity used/present in the double membrane?
there is a lateral movement of membrane components happening at high speed (single phospholipid might move from 1 side of bacterium membrane to the other membrane layer in less than a second, distance = 2 micrometres) but this doesnt happen often
what do cytoskeletal fibres do in the membrane?
interact with various proteins
how does function of the membrane relate to the region of the membrane?
different regions of plasma membrane have different functions
give 6 examples of different functions of plasma membrane.
- cell-cell adhesion in cell-adhesion molecule (CAM), CAM binds one cell to another (CAM of one binds to CAM of another)
- cell-cell communication (chemical or electrical comm., chemical messengers can be released and act upon adjacent cells or cells further away), happens on receptors within membrane
- gates ion channels important for maintenance of membrane potential
what is the role of enzyme in plasma membrane?
breaks down a chemical messenger and terminates its effect
what is the role of receptor in plasma membrane?
binds to chemical messengers such as hormones that are sent by other cells. does cell-cell communication, which is chemical or electrical (chemical messengers can be released and act upon adjacent cells or cells further away)
what is the role of gated ion channel in plasma membrane?
opens and closes to allow ions through only at certain times ∴ imp. for maintenance of membrane potential. absorbs and secretes ions
what is the role of cell-identify marker in plasma membrane?
a glycoprotein acting as a cell identity marker distinguishing the body’s own cells from foreign cells, cell-ECM interactions
what is the whole nucleus + nucleolus structure supported by?
a network fo intermediate filaments
what can ribosomes do on the RER once protein synthesis is completed?
bind or leave the RER, ∴ there is not a permanent structure
what is RER composed of?
cisternae (flattened membrane vesicle sacks) , cytosol, ribosomes (site of protein production)
where is RER found?
is abundant in biosynthetic cells (eg. pancreatic acinar cells) where basophilic RER stains strongly with basic dyes such as haematoxylin
what are ribosomes?
small, electron dense particles composed of a combination of rRNA and ~75 individual distant proteins
describe the physical structure of ribosomes.
a large 60s and small subunits 40s associate when bound to mRNA to catalase protein synthesis
why does 60s + 40s = 80s
bcs svedburg unit is unit of sedimentation not mass
what is the function of free polyribosomes?
synthesize structural, nuclear, peroxisomal or mitochondrial proteins destined to remain in the cell
what is the function of membrane bound ribosomes?
synthesize membrane and lysosomal proteins and proteins destined to be secreted
generally how does protein synthesis happen on the RER?
the ribosome come in membrane and dock with a receptor protein and synthesize the peptide which will tier into the lumen of the ER then ribosome disassociate with RER membrane
what is the structure of pancreatic acinar cells described as?
“berry-like cells”
what is the function of pancreatic acinar cell?
synthesize important enzymes such as lipase
where is SER found?
liver and mammary gland (involved in lipid biosynthesis), ovary, testic, adrenal gland (steroidogenesis) and in muscle for calcium sequestration
describe the structure of RER and SER.
endoplasmic reticulum cisternae create a continuous intracellular compartment
how do proteins move within the Golgi?
enter from the cis face and are processed then leave through the trans face and will either stay in the cell or be secreted through secretory vesicles
what are the 3 parts of the Golgi?
- the nuclear facing cis-face: received transport vesicles from SER and phosphorylates certain proteins
- the central medial Golgi: adds sugar residues to both lipids and peptides to form complex oligosaccharides
- trans Golgi network: performs proteolytic steps, adds sugar resides and sorts different macromolecules into specific vesicles which bud off trans face.
what is a property of Golgi vesicles?
have a specific coat protein which targets vesicles to the correct compartment
what 3 things can happen to the components after leaving the trans Golgi?
- trans Golgi involved in incorporation of new cell membrane
- form special cell vesicles (lysosomes)
- proteins can be secreted by exocytosis
what are the main types of cell vesicles?
- cell surface-derived endocytotic vesicles (reg: Pino- or phagocytotic vesicles)
- Golgi-derived transport and secretory vesicles
- ER-derived transport vesicles
- lysosomes
- peroxisomes
describe vesicles
complex, highly regulated interconnected system
what are lysosomes?
highly glycosylated membrane proteins which protect membrane from the action of hydrolytic enzyme. involved in digesting range of macromolecules: nucleic acids, proteins, lipids
how is the internal environment of lysosomes maintained?
pH of 5 is achieved by vacuolar ATPase bcs protons H+ are actively pumped across membrane into lysosome
how does lysosome work?
bacteria which needs to be destroyed will enter the cell by phagocytosis to form phagosome, then fuse with lysosome. molecules enter by endocytosis and process into a late endosome and fuse with lysosome. autophagy: ER engulf organelles to allow individual components to be reprocessed and repurposed
what is autophagy?
meaning ‘self-eating’, process whereby lysosomes breakdown non-functioning organelles
what is the process of autophagy?
organelles is engulfed by region of SER to form an autophagosome, which fuses with lysosome to form autolysosome
what happens to digested products in autophagy?
they are recycles
what is the aim of autophagy?
a normal homeostasis process for preventing the accumulation of damaged cellular components
give an example of autophagy
tumor cells used autophagy to recycle substrates
how is autophagy involved in cancer treatment?
the inhibition of autophagy is an anticancer strategy ∵ tumour cells = in an environment where starved of nutrients (hypoxic environment) and has limited supply of things it need to grow∴ use autophagy to recycle these components and grow
what is a phagolysosome?
aka endolysosome, when phagosomes and lysosomes fuse
what can happen if individual items dont get broken down (lysosomal storage disorders)?
result in pathologies like hurler syndrome: accumulation of German sulfate in lysosomes
what are signs of hurler syndrome?
frontal bossing, prominent eyes with hyper-telorism and depressed nasal bridge, gapped teeth, gingival hypertrophy, thickened tongue, mental retardation
what are lysosomal storage disorders (LSDs)?
defeats in hydrolytic enzymes stored in lysosomes which can lead to accumulation of residual bodies as substrates cannot be digested
what is the occurrence rate of LSDs (lysosomal storage disorders)?
individually rare but collectively may be as common as 1/7700 live births (27 disorders)
what are 2 examples of LSDs?
hurler syndrome, tay-sachs disease
what is tay-sachs disease?
rare autosomal recessive LSD
what is tay-sachs disease caused by?
mutation in HEXA gene encoding β-hexosaminidase A which leads to accumulation of membrane phospholipid GM2-gannlioside within nerve cells and impairment of neuronal sunction
what are symptoms for infantile, juvenile and chronic tay-sachs disease?
decreased muscle tone, increased reflected, seizures, visual disturbances
what are symptoms for late-onset tay-sachs disease?
motor difficulties, bipolar type psychological symtoms, “cherry red spot”
give an example of a peroxisomal disorder.
adrenoleukodystrophy: impaired β-oxidation of fatty acids resulting in abnormal lipid storage in brain, spinal cord and adrenal glands. leads to intellectual deterioration and adrenal failure
what are other names for adrenoleukodystrophy?
adrenomyeloneuropathy, childhood cerebral ALD, schilder-addison complex
what does mitochondria contain?
enzymes of Krebs cycle (citric acid cycle), oxidative phosphorylation and electron transport systems ∴ is major site of ATP synthesis
what is mitochondria?
double membrane organelle, 0.5-2um, inner membrane cristae project into mitochondrial matrix to increase surface area
properties of mitochondria
contain 16.5 kb (kilo bases) circular genome encoding 37 genes (which code for enzymes imp for Krebs cycle), have own translational machinery and undergo autonomous replication. DNA within mitochondria has maternal inheritance bcs in egg not spermatozoon
what functions is mitochondria important in?
apoptosis, calcium signalling and steroidogenesis
state the amount of mitochondria in cardiac muscle?
it has a lot of mitochondria bcs it has a high energy requirement
what is the structure of mitochondria in the sperm tail?
mitochondria is wrapped around the axoneme of sperm tail, provides ATP required for sperm to move
give an example of a mitochondrial disease.
Kearns-sayre syndrome
what is Kearns-Sayre syndrome?
rare neuromuscular disorder with onset usually before age of 20. progressive limitations of eye movements leading to complete immobility, accompanies by eyelid droop and cardiac condition defects
what causes Kearns-Sayre syndrome?
specific mutations in mitochondrial DNA
what is structure of microfilaments?
globular G actin that fuse together to form F actin (filamentous actin), double helix structure, are mainly cortical in distribution (found near cell membranes). 5nm diameter
give an example of intermediate filaments
keratin in hair and nails
what is the structure of microtubules?
tubular structure
roles of microtubules
form part of spindle fibers, cellular prod in flagella
give a property of microfilaments
dynamic: new G actin monomers are added at + end (powered by ATP) and removed from - end leading to “treadmilling”
role of microfilaments
mechanical stability, motility and contraction (in concert with myosin). provide structural support to microvilli
where are microfilaments found?
sits in cells cortex of periphery cell and sits within microvilli
structure of microfilaments when on cells under microscope
cortical appearance, cortical distribution
what are intermediate filaments?
heterogenous and cell-type specific
what are 2 properties of intermediate filaments?
are not associated with motor proteins and are not dynamic
role of intermediate filaments? give examples
primarily provide structural support for the cell, eg:
epithelial cells contain keratin
mesenchyme cells contain vimentin
muscle cells contain desmin
