Maintaining of the high local concentration of the chemical components in one compartment – higher reaction rates Controlling the transport of intermediates among compartments is other effective regulation system of metabolic pathways, localized in more than one compartment Protection from the environment Protection from the “aggressive” compartment interior
Diffusion Assisted diffusion Active transport
Plasma membrane (plasmalemma) is biologic membrane separating inner parts of the cell from the environment. Plasma membrane is the surface of all cells and is selectively-permeable. This is the regulation part for the intake and excretion of the chemical substances. Composed of lipids (phospholipids, glycolipids and cholesterol esters) and proteins, participating in many cell processes as, for instance, cell adhesion, ion channels transport and cell signaling. Inner part contains specific sites, binding components of intercellular cytoskeleton. Organized in subcompartments – microdomains, rafts
Lipid rafts are small (10-200nm), heterogeneous, highly dynamic, sterol- and sphingolipid-enriched domains that compartmentalize cellular processes.
Cholesterol and sphingolipid-enriched membrane microdomains or platforms ◦ Cholesterol of double concentration ◦ Sphingomyelin concentration elevated by 50% Concentrate and segregate proteins within the membrane More ordered and tightly packed than surrounding bilayer Float freely in the surrounding membrane
Caveolae: small, flask- shaped invaginations of the plasma membrane enriched in caveolin Planar lipid rafts: found in neurons and enriched in flotillin Caveolin and flotillin recruit signaling proteins Signaling can be promoted or dampened
HIV virus ◦ Budding may occur from lipid rafts Influenza virus ◦ Raft-associated glycoproteins in envelope
DNA replication Transcription, synthesis of mRNA, tRNA, rRNA, ribosomes Surrounded by double membrane connected to ER Transport of cytosolic compounds (active and passive) only via nuclear pores Specialized subcompartments (nucleolus – ribosomes formation, DNA replication is localized etc.)
Two membranes – inner and outer are highly different in composition and enzymatic activity Matrix of the mitochondria (mitosol) exhibits different biochemical functions Majority of the mitochondrial proteins is coded in nucleolar DNA (and synthesized by free ribosomes in cytosol), but 13 mitochondrial proteins and some RNA are coded in circular mitochondrial DNA (mtDNA)
Synthesis of more then 90% ATP – oxidative phosphorylation (inner membrane) Heat production Apoptosis – inner mitochondrial pathway Oxidative decarboxylation of pyruvate (pyruvate dehydrogenase complex) ß-oxidation of fatty acids (shorter then 24-C) Kreb’s cycle - mitosol P450 - in inner membrane
Only ornithin transcarbamoylase is located in mitosol Carbamoylphosphate is synthetized in mitochondria from bicarbonate and ammonia, utilizing 2 ATP Citrullin is exported via antiport with ornithine
Proteosynthesis (rough ER = RER) Primal steps of polysaccharides chains synthesis (N-bound glycoproteins (RER)) Synthesis (smooth ER = SER) - phospholipids, triglycerides Cholesterol and steroids (SER) synthesis (on the surface) Hydroxylation of endogenous a exogenous compounds by cytochromes P450 (SER) Calcium ions storage (SER, sarcoplasmic reticulum) Connected with nucleolar envelope
Cooperates with endoplasmic reticulum Enzymatic postranslation protein modifications (glycosylation, sulfatation) Synthesis of new plasma membrane and participation in creation of primal lysosoms and peroxisoms
Intracellular digestion of intracellular, and extracellular compounds Lysosomal enzymes are hydrolases with maximal activity at pH 5 (inside of lysosoms) Hydrolysis of intracellular material – proteins nucleic acids, lipids together with organelles – autofagia Extracellular material is hydrolyzed after the transport into the cell by endocytosis (pinocytosis and phagocytosis) - heterofagia
1. Substances are in membrane enclosed vesicle 2. By fusion of the vesicle with primal lysosom secondary lysosom is formed 3. Lysosomal hydrolases digest the content of secondary lysosoms 4. Digested parts of the hydrolysate are transferred to cytosol for reuse 5. Non-digested material is accumulated in residual body and is excreted by exocytose 6. Remaining (nonexocytosed) residual bodies contain lipofuscin („age pigment“)
Produce or use hydrogen peroxide Differ in function and in number in different types of cell More then 50 types of enzyme catalyzing oxidative and reductive biosynthetic reactions oxidation of very long fatty acids chains (a- and b- oxidation) synthesis glycerolipids, glycerol ether lipids (plasmalogens) and isoprenoids enzymes for oxidation of D-aminoacids, 2-hydroxy acids and uric acid (uricase is absent at higher apes) catalase Known more then 25 perixosomes biogenesis disorders (Zellweger‘s syndrome = absence of peroxisomes and death occurs by age 6 months) Some xenobiotics induce peroxisom proliferation
Keeps phenotype (morphology) of the cell and participate in intracellular transport, cell mobility and cell division Is formed by microtubules, intermedial filaments and actin filaments (microfilaments)
diameter 25 nm and length from 200 nm to 25 mm Polymers of α- and β- tubulin dimmers, polymerized end to end to protofilaments. Protofilaments form hollow microtubules
diameter 10 nm Domain structure of IF is conserved. Each protein contains non-a-helix domain at N and C-ends, which frame a-helix domain of the „stick“ Basic unit of the intemedial filaments (IF) is dimmer Known more then 70 gens for six basic types(I - VI) IF : ◦ I a II - keratins (epithelial and higher) ◦ III – e.g. desmin (sarcomers of muscle cells) and vimentin (e.g. fibroblasts - correct localization of organelles ◦ V - nucleolar IF
The most dynamic part of cytoskeleton are microfilaments (actin filaments). Diameter is 6nm Formed by two linear polymers of actin subunits
Centrosom is organell, main organisation centre of microtubules and regulates cell cycle Centrosom is the cell region, forming microtubules Centrioles are important parts of centrosomes.
54% cell volume Many reaction chains are located in parts of cytosol glycolysis (NAD+/ NADH) PPP - pentosophosphate pathway (NADPH) glycogenolysis glycogenesis (synthesa glykogenu) biosynthesis of fatty acids (fatty acid synthase) synthesis of active saccharides Proteosynthesis support Forming „subcompartments“ with different enzyme concentrations-> many reactions are carried out only in certain parts of cytosol
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