Cell structure, organels, cell types

Cell structure,
organels, cell types
BST
2
Cells
The smallest particles of protoplasm able the
independent existence
 Prokaryotic cell (nucleoid)

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Bacteria (0,1 till 15μm). The smallest are bacteria
Mycoplasma (and Ureaplasma) with cell diameter
approximatelly 0,1–0,3 μm (they have not cellular wall).
The biggest known bacteria is Thiomargarita namibiensis
(0,75 mm).
Archea (0,1-15 μm)
Cell
Eukaryotic cell (nucleus) – protozoa, plants,
fungi and animal
Man: 10-20μm (5-150μm)
Membrane
(we use also term
biological membrane, or
membrane unit)
Function: selective barrier,
maintance of gradients,
transfer of exitation, cell
recognition, communication
with enviroment, receptors
Thickness: 7,5 – 10 nm !
Membrane
specialization (apical,
basal, lateral)
Membrane:
Bilayer of phospholipids, proteins
Phospholipids - outside phosphatidyl-choline and
sfingomyeline
inside phosphatidylserine a
phosphatidylethanolamine
Cholesterol
Proteins (glycoproteins) – integral, superficial,
associated with membrane
Nucleus
Shape according to the cell shape
or specific (neutrophil)
Nuclear envelope –
two membranes and perinuclear space (cisterna)
(40-70nm), nuclear pores 70 nm
Karyoplasm (DNA, proteins) - euchromatin,
heterochromatin + nuclear veil
Bazophilic (stainable by haematoxylin) and
electron-dense → (heterochromatin)
Sex chromatin – Barr body
Nuclear lamina
Lamins – under the
nuclear envelope –
maintan shape
Progerie – mutation
of gene for lamin A
– defect of nuclear
envelope and
skelet (defect of
the nuclear shape
and mitosis)
Nuclear pore
Allow the contact between karyoplasm and
cytoplasm
Nuclear basket – nucleoporins8 proteins
8 filaments extend into the cytoplasm
Importins, exportins
3000-4000 pores per mammals nucleus
Nucleolus
Place for r-RNA
synthesis 1 µm
 Acrocentric
chromosomes – NOR
 Pars amorpha –
fibrilar centrum (Fc)
 Dense fibrilar
component (Dfc)
 Pars granulosa

Cytoplasm
Organels – membranous structures  Cell similar – mitochondria and chloroplast
– two membranes
 Superficial cell derived - endoplasmic
reticulum, Golgi complex, lysosomes,
granules and vacuoles
 Cytoskelet
 Inclusion
 Other structures - ribosomes,
proteasomes

Functional systems of
eukaryotic cells

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System for communication – membrane, receptors, signal
molecules, intercellular contacts
System for production – proteosynthesis: ribosomes, ER,
Golgi
System for the energy gain – mitochondrie
System for degradation - lysosomes, proteosomes
System for protection: stress proteins, peroxisomes, DNA
repair
System for movement –
 Cytoskeleton: microtubules, intermediate filaments,
microfilaments and molecular motors
 Organels – centriol, flagella, cilia
Systems for communication
Membrane
Free penetrable for small molecules – O2,
NO, CO2, small nonpolar molecules
Unpenetrable for big nonpolar and all polar
molecules

Ion channels and pumps
 Transporters
 Receptors
 Enzymes
 Adhesive molecules

System for production –
proteosynthesis
Ribosomes
 RER (Nissl
substance,
ergastoplasm)
 Golgi complex

System for production
Ribosomes – rRNA and proteins, 20x30nm,
Ribo+m RNA= polyribosomes
RER, rough endoplasmic reticulum (membrane
connected with nuclear envelope), segregation
of proteins for export, also posttranslation
modification
GA, Golgi complex cisternae and transport
vesicules and condensation vacuoles . GA
polarized: cis- (convex, near to RER), trans(concave, surface of maturation)
Proteosynthesis
Start of synthesis on ribosomes, signal
sequence + SRP (signal recognition
particle)→ SRP receptor on RER (transmembranous protein) – allows peptid
entrance into cisterna
 After splitting off the signal peptide –
release into the cisterna – folding,
glycosylation
 Membrane peptides stay connected in
membrane of RER

Proteosynthesis
Golgi complex –
transport, storage and posttranslation
modification + protein direction

Package and addressing of proteins - vesicles or
secretion granules
Lipid synthesis:
SER
 (Mitochondria with
tubular crests)
 RER and Golgi lipoproteins
 Lipid droplets
 Multi-lamellar
granules
(surfactant)

Smooth endoplasmic reticulum
Synthesis of lipids
Degradation of glycogen
Detoxication of xenobiotics
Sarcoplasmic reticulum – tubules and
cisternae – storage Ca++
Movement
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Microfilaments (6nm) actin – myofibriles, cellular
cortex, attachment into adhesive junctions (zonula
adherens and focal adhesion) , contractile ring
(cytokinesis)- (faloidin,cytochalazine)
Intermediate (12nm): cytokeratines, desmin, vimentin,
neurofilaments, glial fibrilar protein – typical for
specific cellular types – used as marker
Microtubules (25nm) - MTOC, subunit A and B tubulin
13 fibrils– 9x2 + 2 – kinocilia, 9x3 centrioles
(colchicin, taxanes)
Cellular cortex
Actin- globular G actin
polymerized to fibrilar F
actin
Myosin – molecular motor
– ATP breaking gives
energy for movement

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Movement of cells –
diapedesis
Cohesion
Microtubules
13 fibriles
 Alfa and beta
tubulin
 Dynamic instability
 Kinesin+
 Dynein
Centrosome: centriol,
centrosphere and
astrosphere.
Pair of centrioles
perpendicular to each
other (diplosome)
Mitotic spindle
Kinocilia
Energetic

Mitochondria
Beta oxidation of fatty acids
Citric cycle
Respiratory chain
Oxidative phosphorylation
ATP
Degradation
Lysosomes
size 0,05 – 0,5um
Intracellular digestion (hydrolysis) of the content that is
transported by endosomes
primary, secondary, rezidual bodies (pigment from wearing lipofuscin)
(2 protection again autodigestion: membrane and low pH are
necessary for activity of hydrolytic enzymes)
Arise from GA
Peroxisomes, 0,2 – 1um, sferic, bodies sourrounded by
membrane, contain oxidases for degradation of fatty acid, arise
of H2O2 (degrad. catalase) for detoxication of some xenobiotics,
for example ethanol
Lysosomes
Hydrolytic enzymes- active in acid pH
Acid phosphatase, RNAse, DNAse, protease, lipase
sulphatase, β-glucuronidase
Frequent in cells that are able to phagocytosis (neutrophiles,
macrophages)
In cells living long time – destruction of damaged organels –
undigested rest- lipofuscin (in neurones, kardiomyocytes)
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Protection
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Peroxisomes – contain aminooxidases, peroxidase –
break down hydrogen peroxide in water and oxygen
(liquidation of ROS)
HSP (chaperones)
Proteasome - ubiquitin
Microsomes - SER and cytochrome P450
(hepatocytes, kidney)
Inclusion
Reserve – lipid
droplets (adipocytes)
-glycogen – storage
of glucose –
granules in
hepatocytes and
mucsles
Pigments: melanin,
lipofuscin
Reparation and renewing
systems
Stem cells – part of
reparation systems
Limited reparation –
postmitotic cells – in
G0 phase– cardiac
and skeletal muscle,
neurones, cells of
cartilage

Stem cells
Totipotent – zygota and blastomeres
 Pluripotent – embryoblast
 Multipotent – also in adult (haemopoetic
cells)
 Unipotent – progenitor cells
 Precursor – it is not self-renewing

Types of eukaryotic cells
Epitheliocytes: cytokeratines,
neurofilaments – epithelial cells and neural
cells – intercellular contacts
 Mechanocytes: vimentin, desmin –
connective tissue and muscle –
intercellular tissue and attachment to it are
important
 Amebocytes – free movable cells –
lysosomes (blood cells)
 Gametes

Cell cycle

Length of cell cycle in man
 Blastomeres
(6-8 hours)
 Enterocyte (5-7 hours)
 Spermiogenesis (64 days- meiosis)
 Keratinocytes of epidermis (15 -30 days)
 Erythrocyte (120 days)
 Hepatocyte (1 year)
 Oocyte (up to 40 years)