organelles Flashcards
ER
anastomosing network of intercommunicating channels=cistern formed by continuous membrane. Some regions have polyrib some are smooth
smooth ER
- no polyr, not basophilic
- continuous w GER, less abundant
- cisternae more tubular, appear as interconnected channels w various shapes/sizes
- makes up sarcoplasmic ret
- F: phospholipid synthesis, transported by directed communication w rer by vesicles + phospholipid transfer proteins. Lipid+glycologen metabolism. detoxification through methylation, conjugation +oxidation. why smooth ER abundant in liver (neutralises toxic material alcohol+drugs). Also helps w calcium sequestration (remove Ca from other components to store and use for muscle contraction
GER
- extension from nuclear mem so has limitation
- parallel stacks oof flattened sacs= cisternae w ribosomal presence (extremely basophilic)
- F: protein+phospholipid synthesis, post-translational modifications. Assembly of multichain protein, glycosylation (covalent attach carbohydrate to protein). non functional proteins (genome?) ERAD endoplasmic reticulum-associated degradation goes back to cyto, conjugation to ubiquitin (assoc w proteosome which degrades this)
protein synthesis for rer membrane
- mrna -> cytosol through nuclear pore -> free subunits- ribosome->rer mem
- encode for specific n terminal signal seq (15-40aa seq)+ hydrophobic residues
- signal recognition particle binds signal seq to receptor of ER (inhibit elongation)+release polypeptide released to translocation channel. in lumen peptidase release signal seq=allow elongation to begin
- creates hydrophilic proteins. protein folding initiated by oligossac; binds to polypeptide using glycotransferase+calnecin (only binds after protein elongated to 2 glucose mol). after calnecin+oligos cleaved from folded protein. Released laterally into bilayer by peptidase form transmembrane protein w carboxylic acid on external and amino internally.
post-translational mod:
hydroxylation- oxidation reaction where C + H -carbon hydroxyl - needed to convert hydrophobic - philic
phosphorylation- covalent addition of PO4 to side chain using kinase (regulates protein activity by stimulating or inhibiting structure)
proteosome vs peroxisome
proteosome
- cylindrical w 4 stacks of rings (each have 7 proteins -protease). at both ends of cylinder has ATPase for degradation of protein not functional due to misfolded, oxidised amino or denatured. also removing proteins that no longer needed to stop activity).
- multiubiquitin formed (ubiquitin in every cell has 76 aa attached to it) through enzyme complexes that bind it to lysine of targeted protein. its recognized by proteosome+ unfolds it using ATP+degrade it to short peptides or aa.
peroxisome 0.5-1.2um
- single membrane, spherical w no nuclei
- F: FA degradation, enzyme degrade hydrogen peroxide. involved in reaction leading to cholesterol/bile acids.
- peroxidase- catalase decompose -H2O2>H20+O2 needed for breakdown of ethanol in liver+kidney (why abundant there); complements function of smooth ER+mitochondria- metabolism of lipids, b oxidation of fa (18C or more)
- forms: through growth+divison of preexisting OR budding of precursor vesicle in ER. enzyme of peroxisome synthesised in free polyr and has small signal seq at carboxyl terminus recognized by peroxisomal membrane= allow for protein to be imported
lysosomes
0.05-0.5, oval, maintain pH 4.5-5 (has proton pumps); azurophilic granules. 40 acid hydrolases (breakdown mol-protease[protein-aa] lipase [lipids-FA]glycosidade [carbs-monomer] nuclease [nucleic acid-nucleotides] )
- F: digest endocytotic mat+non functioning organelles through autophagy
1)material taken by endocytosis through pinocytosis or phagosome and fuse w lysosome.
2) activate proton pump, acidify content and digests it, now called heterolysosome. content released to cyto and stored as residual bodies, over time = lipofuscin
3) autophagy: membrane from smooth er fuse around material/organelle that needs to be removed= autophagosome which fuse w lysosome. digested product released to cyto
- autophagy enhance when secretory cells have accumulated (in high-stress situations-starvation)
formed: hydralase made in GER-> GA modified +packed + vaccum= lysosome. enzyme mannose-6-phosphate added to n linked oligosaccharide of hydrolase using phosphotransferase. in trans face of Golgi where receptor of m6p bind proteins+lead to pathway where lysosome becomes secretory
not well stained w H&E so use TOLUIDINE BLUE+ endothelial cells use FLUORESCENT DYE
GA
flattened vesicles=cisterns arranged parallel system. vesicles merge w cis region (revieves newly synthesized proteins from rer). trans (more tubular membrane structures) is where vesicles become larger, rounder where accumulates +condense material that bud off =exocytosis. OR used to create lysosomes or granules (vesicles but densely packed) . vesicles STAINS LIGHT.
F: post translational mod of proteins= glycosylation (covalently attach carb), sulphanation, hydroxylation, phosphorylation.
form: due to coat proteins. Clathrin helps regulate vesicular traffic. Anterograde mov in cis uses COP II, retrograde COP I. Golgins help w direct fusion of vesicle to cis using other binding proteins, receptors and enzymes to help.
zymogen granules is in pancreas contain digestive enzyme
mitochondria
0.5-1um, up to 10um in length, microtubules, double membrane w naked circular DNA
outer membrane high density of proteins compared to either, reduces fluidity
F: oxidation of FA, Ca store, genome codes for fraction of its proteins (also rely on nucleus) ; proteins transported using transferase. has porins allow pyruvate to enter=aerobic resp.
inner mitochondrial mem- folded into long crista project into matrix+ increase SA. has elementary particles help w oxidative phosphorylation
Matrix enzyme oxidise pyruvate. FA form co-A enzyme that is oxidised-> co2 as waste ruch mol to help w ETC
-chemiosmosis ATP using ATPase (multi-subunit 10um, globular complex, assoc w proton uptake, hydrophobic pathway allow H p go from high-low rotating the polypeptide in complex. mechanical energy stored in PO4 converts ADP+P to ATP
in ETC. Cytochrome =redox active proteins that convert fe2->fe3 co-factors. dehydrogenases oxidizes substrate by reducing electron acceptor NAD, flavoproteins involved in oxidation reaction and contain derivative of NA riboflavin FADH
Cytochrome c -> cytoplasm activate protease to degrade all cellular components= apoptosis
Mitochondrial granules divalent cation binding sites
Intermembrane space reg of resp and metabolic pathways: Proton accumulate for ATP production due to ETC Intercristal space DNA, RNA,tRNA, ribosomes+ enzymes for lipid and protein synthesis, and kreb cycle enzymes
Endosymbiotic theory:Bacterial dna due to aerobic prokaryotic living symbiotically w anaerobic eukaryote
inclusion of materials (intracellular materials)
accumulation of deposits of metabolite or deposits filled w micromol. considered non-motile and non-living part of cell-little none metabolic energy. No membrane.(in neuron cell body)
- glycogen granulocyte- aggregates of glycogen polymers filled w glucose. in cardiomyocytes, skeletal, heparinocytes and vaginal epithelial.
- fat droplets accumulation of lipids prominent in adipocytes, adrenal cortex cells and liver. F: lipids: repair+ replace damage done by membrane+store energy. Adipocytes produce hormones-steroids and elderly women sex hormones made here. OIL RED+SUDAN BLACK
- pigment deposits
1) exogenous pigments- form outside of cell (environment) dust +C.
2) endogenous pigments- (from cell)
melanocytes- melanin, dark brown pigment UV protect skin+eyes
lipofuchsin- accumulated of residual bodies from digested mat of lysosomes H&E, yellow-brown pigment in static/prominent cell population- cardiomyocytes/neurons. increases w age
bilirubin- yellow-orange bile pigment. excess amount=jaundice (yellow tint to skin, white of eyes when excess breakdown of rbc )
hemosiderin- composed of denatured ferratin+ iron. brownish pigment. formed by indigestible hb residues recognized in spleen or aged erythrocytes+ alveolar macrophages
nucleus
- Nucleus: membrane-limited compartment w/ the genome in eu cells
- Chromatin 1.8nm (DNA+histones) found in nucleus( heterochromatic/ euchromatic)
- Nucleolus: non-membranous structure w/ RNA, site of rRNA synthesis and cell cycle regulation contain 3 areas: fibrillar centres, pars fibrosa, and pars granulosa
- Nuclear envelope: inner + outer membranes w perinuclear cisterna in between has nuclear pores. outer membrane continuous w rRE
- has selectively permeable barrier between nuclear compartment + cyto enclosing the chromatin. Mediates the active transport of proteins, ribonucleoproteins, and RNAs
- Nucleoplasm: nuclear content other than chromatin and nucleolus
- Barr body in females: unexpressed X chromosome
- DNA follows a highly organized coiling pattern: double helix 2nm attached to 8 histones (2 copies of each H2A+B+H3+H4) wrap in DNA (150 base pairs)nucleosome 11nm). coils=chromatin fibril 30nm which are organized into loops 700nm and anchored to nuclear matrix (w densely packed w heterochromatin/euchromatin)
- Heterochromatin in 3 locations: marginal, karyosomes, nucleolar-associated? (near nuclear lamina)
- Euchromatin cant be observed under light microscope bc= metabolically active cells
- Outer nuclear membrane resembles ER membrane and continuous with rER membrane. Polyribosome attached to ribosomal docking protein on cytoplasmic part of nuclear mem.
- Inner nuclear membrane supported by rigid network of IF protein attached to nuclear lamina. which also has specific lamina receptors+ proteins bind to chromosome +secure attachment to nuclear lamina
- Nuclear lamina (thin e- dense IF layer) resides underneath the nuclear membrane
microscopic analysis of chromosomes- at metaphase where arrested due to colchine (disrupt microtubules). proccessing+ staining cells condensed chromosomes photographed w lighy microscope and =karyotype
PM
Eu cells have a membrane made of phospholipids, proteins, cholesterol, and oligosaccharide chains.
- The membrane is 7.5 to 10 nm wide and visible by TEM. Light can see glycoproteins and organelles.
- Phospholipids: amphipathic with two non-polar long-chain fatty acid tails and one charged polar head with a phosphate group.
- Membrane follows fluid mosaic model with integral proteins moving laterally but restricted by cytoskeletal components.
- Integral proteins have a lipid anchor and require detergents to be removed. Peripheral proteins can be removed with salt solutions.
- The membrane is asymmetrical with different lipid and protein distributions on both surfaces of the cell.
- The glycocalyx helps protect the cell by preventing pathogens from penetrating.
- Lipid rafts are concentrated areas of cholesterol and saturated FA that reduce lipid fluidity and often contain large, complex protein complexes involved in cell signalling and overall cell arrangement.
Fixated: membrane appears trilaminar because fixated with osmium tetroxide it bind to the polar heads ( has phosphate), + outer sugar chains + also the membrane proteins. Which will produce two dark outer lines that contrast with the light band (osmium free FA). can analyze this when you freeze fracture or Cairo????. freeze membrane and see integral proteins protruding the inner and outer membrane; peripheral and for the glycoproteins you can see it project only from the outer membrane which (specifically for like glycocalyx?)
F: 1) selective permeability controls what goes in and out of the cell.
2) provides physical barrier which protects the cellular components 3) supports the cell structure.
4)has electrochemical gradient that established and maintains the electrical charge across the plasma membrane.
5) communication through receptors that are able to recognize and respond to molecular signals.
PM transport
Osmosis is the movement of water molecules down its concentration gradient and requires aquaporin.
Facilitated diffusion moves solutes across the membrane against or along the concentration gradient using channels or carrier proteins that undergo a conformational change using ATP for transport.
- Pump transporters can be antiport or symport, with both products going in the same direction for symport (e.g., sodium and glucose) and products going in opposite directions for antiport (e.g., Na and H).
Simple diffusion moves solutes along the concentration gradient and doesn’t require proteins.
ABC transporters are common in multidrug resistance (MDR) and pump out drugs that kill tumors, increasing tumor resistance.
membrane transfer of vesicles
1) phagocytosis encloses larger molecules in the vacuole. Like cell eating.
- Endocytosis -cell takes in molecules and particles from its surroundings. There are two types of fluid phase endocytosis: pinocytosis and receptor-mediated endocytosis.Pinocytosis- formation of small invaginations in the cell membrane, which surrounds fluid or undigested material. These invaginations, 80 nm, can either fuse with lysosomes for digestion or with the membrane to transport extracellular material in a process called transcytosis.Receptor-mediated endocytosis uses integral proteins as receptors for hydrophobic molecules such as hormones, LDL, and ligands. The invagination process occurs in a coated pit, surrounded by the protein CLATHRIN, forming a coated vesicle containing the ligand. These vesicles fuse with endosomes (dynamic system of vesicles) are separated by acidic pH pumps, allowing for recycling of the receptor or transcytosis of the ligand. The process of endocytosis involves both early and late endosomes.
Exocytosis- bulk movement of substances out of the cell through the diffusion of vesicles with the PM, which is highly regulated by specific membrane proteins. triggered by Ca ions, and for protein secretion, there are two types: constitutive secretion where the product is secreted as soon as it is synthesized, and regulated secretion, which requires a specific signal for the response.
A multi-vesicular body can be formed by the accumulation of small vesicles, and they can either fuse with lysosomes for digestion or fuse with the plasma membrane and release the small vesicles outside of the cell as exosomes.
cell signaling
has many families of receptors that respond to the extracellular molecule/physical stimuli
1)Endocrine form of hormones and it travels throughout the whole body
2)Paracrine chemical mediator rapidly metabolizes right after it’s released. Only acts on local cells
a. Synapse special paracrine receptor because it effects adjacent cells. Or the neurotransmitter acts on adjacent cells by binding to a specific specialized contact, known as a synapse
3)Autocrine signal binds to a receptor in the same place that it was produced
4) Juxtacrine in embryonic tissue. And it’s where the signaling protein is a part of the membrane, and it acts on adjacent cells in direct contact
5) signaling receptors and it usually acts on neurotransmitters+ Hormones
6) Channel linked receptors open when the ligand binds to the receptor, allowing for the ions to diffuse in.
- G coupled receptors ion bind to G protein molecule on the membrane and it binds to GTP (activated). G Protein will leave the receptor and binds to an effector protein (ion channel/enzyme, increasing the conc of the secondary messenger-ADENYLCYCLASE cause protein kinase enzyme to active.
- enzymatic receptor-Protein kinase activates to phosphorylase other enzymes. hydrophobic molecules/ signals affect DNA transcription-hydrophobic signal, bind to carrier proteins in plasma + travel throughout body. Enters cell + diffuses in because it’s lipophobic. Bind to intracellular receptor protein and then in nucleus bind to a specific gene sequence/DNA sequence, which then increases the level of transcription.
