Intracellular organelles and molecular Intracellular organelles and molecular mechanisms of organimechanisms of organizzation of ation of a a

eucareucaryyotic cellotic cell

Typical organelles in eucaryotic cells

Membrane-bounded compartments Membrane-bounded compartments

NucleusNucleus Endoplasmic Endoplasmic

reticulumreticulum Golgi apparatusGolgi apparatus LysosomesLysosomes EndosomesEndosomes MitochondriaMitochondria ChloroplastsChloroplasts PeroxisomesPeroxisomes

Advantages of Advantages of compartments:compartments:

Microenvironment for enzymes, Microenvironment for enzymes, cofactors and substratescofactors and substrates

More efficient course of More efficient course of chemical reaction due to a chemical reaction due to a reduced diffusion of moleculesreduced diffusion of molecules

Appropriate ionic milieu (pH, Appropriate ionic milieu (pH, redox potential etc)redox potential etc)

Separation of dangerous Separation of dangerous activities (proteolytic enzymes activities (proteolytic enzymes oxidative enzymes etc) oxidative enzymes etc)

How to study organelles:How to study organelles:

optical and electron microscopyoptical and electron microscopy

Saccharomyces cerevisiae. Cell size : 3-5 Saccharomyces cerevisiae. Cell size : 3-5 µµmm

Phase contrast microscope

ELM – freeze -fracturing

ELM - ultrathin section

How to study of organelles: How to study of organelles: differential centrifugationdifferential centrifugation

How to study of organelles: gradient How to study of organelles: gradient centrifugationcentrifugation

NucleusNucleus

Jaderný obal

Jadérko

Chromatin

Nuclear envelope

Nucleus

MitochondriaMitochondria

Compartments:Outer membraneMatrixIntermembranous space

Fluorescing mitochondria

Mitochondria – ultrathin section

ChloroplastsChloroplasts

Light microscope Electron microscope Flattened membrane vesicles acumulating to form grana

grana

Endoplasmic reticulumEndoplasmic reticulumflattened membrane cisternae flattened membrane cisternae rough ER – cisternal surface covered by ribosomes rough ER – cisternal surface covered by ribosomes smooth ER cisternal surface without ribosomessmooth ER cisternal surface without ribosomes

Function: rER- synthesis of proteins for secretory pathway sER – synthesis of lipids and steroids

Golgi apGolgi apppararaattususstacks of flattened cisternae withstacks of flattened cisternae with perifer periferal vesiclesal vesicles

Synthesis and packaging of molecules destined to be secreted from the cell

Vesicular transportVesicular transport: : secretory vesicles (dark blue) and endosomes (light blue)secretory vesicles (dark blue) and endosomes (light blue)

PeroxisomesPeroxisomessmall membrane-bounded vesicles that provide containers for small membrane-bounded vesicles that provide containers for reactions where a dangerously reactive hydrogen peroxide is reactions where a dangerously reactive hydrogen peroxide is generated and degraded.generated and degraded.

Arrangement of organelles in a liver cell (multipolar) and Arrangement of organelles in a liver cell (multipolar) and in a pancreatic cell (polar orientation)in a pancreatic cell (polar orientation)

Multipolar organization Polar organization

Cytoskeleton as a scaffoulding for Cytoskeleton as a scaffoulding for cell organelles cell organelles

Actin Microtubules Intermediate filaments

Topology of organelles in a typical eucaryotic cell: A cytoskeleton – a system of protein filaments (microtubules,actin filaments

and intermediate filaments) crisscrossing the cytoplasm and forming with other proteins a scaffolding for membrane organelles

The placement of organelles by microtubulesThe placement of organelles by microtubules

green- MT

blue – ER, yellow - GA

MT

ER

MT

GA

Amino acid sequences as signals for Amino acid sequences as signals for rrecognition or ecognition or attachment attachment

Attachment of Attachment of melanosomes to MT, melanosomes to MT, actin filaments and actin filaments and PMPM

Attachment of Attachment of vaculoles to actin vaculoles to actin cables via signal cables via signal

proteins and adaptorsproteins and adaptors

Microtubule-based transport and intra-cellular trafficking pathways.

Many intracellular trafficking pathways involve active and directed transport along the microtubule cytoskeleton. Microtubule-dependent trafficking in mammalian cells includes: (a,b,c) ER-to-Golgi transport, (d) TGN-to-ER transport and (e) lysosomal, (f,g) endosomal and (h) mitochondrial motility

Plectin molecules serve as linkers between intermediate Plectin molecules serve as linkers between intermediate filaments (orange), microtubules (red) and actin filaments (orange), microtubules (red) and actin filaments (yellow) filaments (yellow)

Key terms from the lectureKey terms from the lecture 1. Size of cells and organelles1. Size of cells and organelles2. Overview of eucaryotic cell organelles 2. Overview of eucaryotic cell organelles 3.Techniques of organelle separation and description 3.Techniques of organelle separation and description (microscopy, gradient centrifugation, differential (microscopy, gradient centrifugation, differential centrifugation centrifugation 4. Organelle description: nucleus, mitochondria, 4. Organelle description: nucleus, mitochondria, chloroplasts, chloroplasts, ER, GA,ER, GA, secretory vesicles, lysosomes, secretory vesicles, lysosomes, peroxisomesperoxisomes 5. Cytoskeletal components and localization of 5. Cytoskeletal components and localization of organellesorganelles6. How to prove co-localization of ER or GA with the 6. How to prove co-localization of ER or GA with the microtubulesmicrotubules