Histology Cell Bio2

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2 major compartments of cell

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cytosol
organelles

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function of compartmentalization wi the cell

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makes metabolisms possible by the exchange of small molecules and their use in different functions

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where are proteins made?

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in the cytosol

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purpose of receptors

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allows specific recognition of proteins and other molecules to target cell. The hi degree of specificity of protein transport is crucial to the survival of thecell and the organism

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what is wi the nucleus?

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nuclear env
nuclear pores
chromatin
euchromatin
heterochromatin
nucleolus
nucleoplasm
nuclear lamina

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site of DNA/RNA syntheisis

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nucleus

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site of protein synthisis and int. metabolism

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cytoplasm

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ER

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ribosome bound to membrane surface for synthesis of integral protins and soluble proteins destined for secretion

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golgi apparatus

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modifies and transports lipids and proteins received from ER

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mitochondria

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generates ATP used to drive cellualar rxns

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lysomos

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has enzymes to degrade endocytosed macromolecules and particles

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peroxisomes

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has enzymes used in oxidative rxns

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major membrane bound organelles in animal cell

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nucleus
ER
golgi
lysosomes
endosomes
mitochondria
peroxisomes

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signal peptide

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aa sequence that direct the delivery of protein out of cytosol. If protein does NOT have signal peptide then it will remain in the cytosol

the signal peptides are recognized by receptors on specific organelles

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mechanism to move proteins between compartments

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gated transport
transmembrane transport
vesicular transport

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gated transport

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used to get proteins out of cytoplasm through pores in membrane

used to get NA out of nucleus through nuclear pores

(only between cytosol and nucleus)

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transmembrane transport

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gets proteins from cytosol directly across membranes into mitochondria,ER, peroxisome. (membrane bound organelle)

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vesicular transport

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transports vesicles proteins from one compartment to another

transports from Golgi, vescilces get pinched off and move along microtubles to their target organelles where they fuse w/the surface

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describe protein synthesis

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mRNA made from DNA in nucleus

mRNA goes into cytoplasm

ribosomes travel along mRNA and protein extends using tRNA to carry new AA to extend the AA

when stop codon reached complex disacciates and protein is released

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polyribosomes

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clusters of ribosomes on mRNA

appear in cell involved in lots of proteins synthesis

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site of RNA transcription and RNA splicing

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nucleus

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describe nucleur envelope

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2 membranes continuous w/the ER

inner and outer membrane sperated by perinuclear space

where the 2 membrane fuse they form nuclear pores

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chromatin

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chromosomes and histone proteins

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what are chromosomes composed of?

when are chromosomes highly dispersed in the cell?

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made of DNA

highly dispersed during interphase(nondividing stage)

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histones

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small conserved proteins complexed w/DNA

positively charged proteins that bind to negatively charged DNA in the nucleus

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2 types of chromatin

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heterochromatin
euchromatin

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heterochromatin

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highly condensed chromatin

darkly stained

DNA is inactive bc wound tightly around histone

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euchromatin

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less condensed chromatin

stains lighter

active chromatin bc open

contains gens that are transcribed into RNA

allows things to pass and merge w/nuclear pores

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difference between nuclear env inner and outer nuclear mem

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inner n. membrane has proteins that bind to nuclear lamina

outer membrane have ribosomes bound

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describe the breakdown of the nuclear env during cell divison and the reassembly

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nuclear lamins are phosphorylated and fragment into smaller groups for cell divison

after chromosomes move apart, the lamins are dephosphorylated and reaggregate forming envelopes around each chromosome

these envelopes fuse so that all the chromosomes are in a common env. to make a nucleus

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nucleolus

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dark staining region where ribosome synthesis occcurs by rRNA assembly

contains large loops of DNA that encode rRNA genes

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in what cells is nucleolus prominent

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motor neurons

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how are ribosomes made?

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proteins in cytosol get in nucleolus through pores and assemble with rRNA and form subunits which leave through pores

the subunits aggregate outside in cytosol to form ribosomes

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nuclear pores

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perforation in n.env

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nuclear pore complex

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comprised of proteins that form channel through which small mol. can pass

passage of large proteins requires specific receptor proteins located in the pore complex. they are actively transported across the n. env. and require nuclear localization signal to pass through n.pores

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how to proteins get through n. pores into the nucleus?

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n. import receptors bind to the prospective n. proteins. the complex binds and the pore opens and the n.protein and receptor get actively transported into the nucleus. the receptor is then exported back into the cytolplasm to be reused

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how does mitochondria change shape and move around cytoplasm?

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by associating w/microtubules

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purpose of matrix granules in mitochondrial matrix

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sequester calcium

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2 compartment of mitochondria

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matrix space- contains enzymes that metabolize pyruvate and fa to acetyl CoA and citric acid cycle enzymes that oxidize acetyl CoA

intermembrane space chemically equivalent to cytosol

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differing proteins in outer and inner mitochondrial membranes

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outer membrane contains transport proteins that are permeable to small molecules

inner membrane is highly covoluted foming infoldings called cristae
inner is impermeable to
ions.
inner contains respiratory
chain enz(ETC)

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summary of mitochondrial energy metabolism

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pyruvate and fa enter the mitochondrion and are broken down to acetyl Co A and then metabolized by citric acid cycle.

in the process of ox phos hi nrg e- from NADH are passed to O2 by respiratory chain in inner membrane making ATP by chemiosmotic mech.

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mitochondrial DNA

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encodes for 37 genes
all mitochondrial DNA is from maternal side

damage by free radicals contribute to aging

mutations cause serious illness

oxidative rxn can cause mutations in the DNA which can damage the cell

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what encodes mitochondrial proteins?

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mitochondrial proteins ae encoded by nuclear DNA and are transported into mitochondria by transmembrane transport using molecular chaperones to guide the proteins through channels and then refold them into their active configuration

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peroxisome

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membrane bound organelle that carries out oxidative rxn using molecular O2.

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enzymes in peroxisomes

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catalase and urate oxidase used to detox cmpds

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peroxisome core

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crystalloid core compose of urate oxidase (usually not in human)

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purpose of Oxidase and Catlase in peroxisomes

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oxidase uses molecular oxygen to remove hydrogen from organic substrates in oxidative rxn that produces hydrogen peroxide

Catalase uses the hydrogen peroxide generated to oxidize other substrates

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what organs is the prescence of peroxisomes very important?

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liver and kidney bc they are involved in detoxing poision cmpds.

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Zellweger syndrome

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autosomal recessive disease associated w/ absence of peroxisomes

fatal by age 6mos

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Rough ER

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site of production of transmembrane proteins and lipids

membrane has ribosomes attached (rough)

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Where are all proteins destined for secretion synthesized?

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on rough ER

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integration of proteins into rough ER membrane

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1.mRNA binds to ribosomes in cytosol then translation starts
2.proteins w/signal peptide sequence bind to signal recognition particle (SRP) which causes a pause in translation
3.the ribosome is directed to ER by SRP
4.The ribosome binds to ER and translation continues
5.Newly synthesized transmembrane proteins are translocated across ER membrane but are not released into lumen. Soluble protiens (which are destined to be secreted from cell or go to lysomes) pass into ER lumen. Proteins made in ER are sent to Golgi apparatus for post translation modificaion and to be directed to final destination

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smooth ER

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series of interconnected tubules

prominent in steroidogenic cell and hepatocytes

can sequester Ca which is used in cell signaling pathway

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what organelle is most abundant in cell that secretes steroid?

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smooth ER

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what structure/layer is present in thick skin and not in thin skin?

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stratum lucidum

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vesicular transport

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transport vessicles bud off from one compartment and fuse with another

both intramembranous proteins and soluble proteins are transported from RER to golgi this way

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how are proteins transported from RER to golgi?

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by vesicular transport

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golgi

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receives and modifies newly synthesized lipids and proteins from RER by vesicular transport

distrubutes proteins to other cellular compartments

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describe transport of proteins from RER to golgi

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proteins destined for secretory vessicles, plasma membrane, or lysomsomes enter the Golgi at the cis face and move through the Golge then exit at trans golgi.

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what mediates transfer of proteins from RER to golgi and between golgi compartments?

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transport vessicles

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lysosomes

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membrane bound vesicles containing hydrolytic enzymes

controlled digestion of macromolecules

have acid hydrolases that require acidic env.

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how does lumen of lysomsomes stay at acidic ph?

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by proton pump in membrane

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3 major pathways in cell that can lead to degradation of materials in lysosomes

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endocytosis
phagocytosis
autophagy

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endocytosis to form lysosomes

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material is taken up into cell by endocytosis is delivered into intracellualr compartments called endosomes

endosomes fuse with transport vessicles from golgi containing acid hydrolases to form lysosome

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degradation by phagocytosis

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specialized cells like macrophages and neutrophils engulf particulates to form phagosomes

the phagomsome is converted into lysosome by fusion w/lysosome or late endosome

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degradation by autophagy

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disposal of obsolete organelles of cell. autophagy occurs by enclosure of organelle by membrane derived from the ER which creates an autophagosome

the autophagosome fuses w/a lysosome or late endosome

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how to ID lysomsome

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its hard so incubated tissue w/ phophatase and lead ions. the acid phosphatase in the lysomsome produces lead ppt which is e-dense

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how are lysosomal proteins in golgi sorted?

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1.M6P added to lysosomal hydrolases in cis golgi
2.M6P grps of lysosomal hydrolases bind to M6P receptors in trans golgi
3.Transport vesicles bud off trans golgi
4.transport vesicles fuse w/late endosome
5.dissociation of lysomal hydrolase and M6P receptor
6.M6P receptor is recycles back to trans golgi

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lysomal storage diseases

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genetic diseases which cause deficiency of one of the acid hydrolases cause accumulation of material in cell causing severe cellular malfunction or cell death.

ex:sphingolipid storage disease are associated w/defects in sphingolipid catabolism, the enzymes for this are in lysosomes.

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Early Endosomes

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just beneath plasma membrane

proton pums in membrane maintain pH 6

material is endocytosed from plasma mem and forms vesicle which is tranpsoted to early endosome. early endosome travels into cell to give its contents to late endosome

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late endosome

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close to golgi and nucleus

more acidic then early endsome bc it accumulates more vessicles to lower its pH

gets material from golgi and early endosome

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what do golgi transport vessicles targeted to late endosmes contain?

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either acid hydrolases or proton pumps

when golgi vesscicles fuse w/late endosome they become lysosome

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endocytosis

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material is enclosed by invagination of plasma mem

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2 categories of endocytosis

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1.pinocytosis-ingestion of fluid (continuous)

2.phagocytosis-ingestion of large particles (require rec must be activate)

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receptor mediated endocytosis

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macromolecules in ECF bind to cell surface receptors

Clathrin binds to cytosolic side of receptors

Clathrin coated vesicles contain receptor macromolecue complexes bud off membrane and enter the cytolsol as coated vessicles. the vessicles shed their coats and fuse w/early endosomes

contents of the vesicles travel trhough endosomal comparments by vesicular transport

specific receptor proteins on vicle membrane determine the selectivity of transport visicle docking to other cellular compartments

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exocytosis

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secretory pathway

vesicular transport of material from trans golgi to cell surface.

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2 pathways that exocytosed material can take

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constitutive secretory pathway

regulated secretory pathway

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constiutive secretory pathwy

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default pathway

vesicle directly targeted to cell surface

occurs in all cells

continuous secretion of soluble proteins in ECF

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regulated secretory pathway

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protein storage in secretory vesicles

present in cells specialized for secreting products in response to specific extracellualr signals

stored in apical part of cell

if become large, vesicles are called storage vesicles

hormonal/neuronal signal stimulates cell to release vesicle contents to EXF by exocytosis

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cytoplasmic inclusions

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secretory granules

pigment granules

lipid

lipofuscin

glycogen

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secretory granules containing mucus

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goblet cells lining ep tissue

secret mucus by exoctosis to keep surface of ep protected

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pigment granules (melanosomes)

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membrane bound
contain melanin
protect DNA from UV iradation

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lipofuscin

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residual bodies in old cells: debris filled vacuoles in long lived cells (undegraded lysomal material)

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glycogen

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non membranous granles of glucose polymer

often around skeletal m.