The organelles of animal and plant cells are similar to each other except that __________ are present only in animal cells, and ___________ are present only in plant cells.

ORGANELLES

Animal and plant cells have organelles.

Organelles compartmentalize functions within the cell.

MITOCHONDRIAElectron micrographs of cells show

mitochondria as rod like structures.0.5μ,m-1 μm in diametre 7 μm in length

BIOMEDICAL IMPORTANCEINNER MEMBRANEComponent of electron transport

system.Impermeable to most ions and large

molecules e.g; H,Na,ATP,GTP ,Pyruvate,Citrate etc.

For transport special carriers are present e.g Adenine nucleotide carrier system(ATP-ADP Transport)

Complex II,Succinate dehydrogenase

Complex V,ATP Synthetase complex.

OUTER MEMBRANEPermeable to all ions

MatrixInclosed by inner mitochondrial

membrane.Contain enzymes of: Citric acid cycle β oxidation of fatty acids Amino acid oxidation Urea and heme synthesis

NADFADADP,PiMitochondrial DNACircular DNA,has information for 13

mitochondrial proteins and some RNAsMitochondrial cytochrome P450 system

P450 system is involved in the hydroxylation of cholesterol to steroid hormones(placenta,adrenal cortex,ovaries and testes)

Bile acid Synthesis (liver)Vitamin D formation(kidney)Mitochondria plays a key role in

aging.Cytochrome C component of ETC plays a main role in cell death and Apoptosis.

MITOCHONDRIAL DISEASES.Fatal infantile mitochondrial

myopathy and renal dysfunction.MELAS(Mitochondrial

encaphalopathy lactic acidosis and stroke)

Myoclonic epilepsy etc.

ENDOPLASMIC RETICULUM

BIOMEDICAL IMPORTANCEROUGH ERBiosynthesis of proteins.Special proteins called CHAPERONS

are present ,involved in proper folding of proteins.

Protein glycosylation

SMOTH ERSynthesis of lipids,cholesterol and

steroid hormones.Detoxification of endogeneous and

exogeneous substancesMicrosomal cytochrome P450

monoxygenase system(Xenobiotic metabolism)

Elongation of fatty acidsDesaturation of fatty acidsOmega oxidation of fatty acidsSynthesis of other

organelles ,peroxisomes and lysosomes in association with Golgi Apparatus.

_________ ___________GOLGI APPARATUS

Function: Packages, modifies, and transports materials to different location inside/outside of the cell.

Appearance: Stack of pancakes

Consists of a stack of curved saccules.

Receives protein and also lipid-filled vesicles from the ER, packages, processes, and distributes them within the cell or for export out of the cell (secretion).

Also encloses digestive enzymes into membranes to form lysosomes.

Golgi complex is the site for the formation of carbohydrate side chains of glycoproteins and mucopolysacchrides(GAGs)

It gives rise to acroblast of spermatozoa that is converted to acrosome.It contains lysosomal enzymes and proteinases invoved in the fertilization of ovum.

LYSOSOMESExtracellular digestion of both

intracellular and extracellular substances.

Single limiting membrane.Acidic pH 5.They have group of enzymes called

HYDROLASES.The enzymes destined to inter lysosomes has mannose at their ends,which change to manose 6 phosphate and enter into the lysosomes.

BIOMEDICAL IMPORTANCE

BONE REMODELING An osteoclast breaks the bone

matrix down into fragments by means of secreated acid and lysosomal hydrolases.It completes the breakdown by endocytosis and lysosomal digestion of the fragment.

THYROXIN PRODUCTION.

LIPOFUSCIN. Age pigment wear and tear pigment.DISEASES OF LYSOSOMESRelease of lysosomal enzymes in

response to ionizing rediations,some carcinogens,silca particles,dust,hypoxia,heat and certain drugs leading to cell death, mutaions in genome and malignancies.

Lysosomal storage diseases

PEROXISOMESFirst observed by electron microscopy in

animal cells (1950s), then in plant cells (1960s)

Christian deDuve (1965)Isolated from liver cells by centrifugationCalled them peroxisomes because they

generate and destroy H2O2

Single membrane

Roughly spherical0.2 - 1.7m

Composition varies

BIOMEDICAL IMPORTANCERich in enzymes.50 Enzymes have been demonstrated in

them.Proteins called PEROXINS are involved

in the various stages of their production.These are involved in the metabolism of

lipids i.e.plasmalogens,cholesterol.Involved in the β oxidation of very long

and branched chain fatty acids.Shortens the chain of cholesterol in the

formation of bile acids.

Peroxisomes are involved in the production and detoxification of H ₂O₂

PEROXYSOME PROLIFERATOR ACTIVATED RECEPTOR(PPARs).

PPARs α:expresses genes hepatic enzymes for β oxidation and formation of ketone bodies.

PPARsγ:express genes encoding for protein synthesis involved in lipid synthesis and storage in the fat cells.

PPARsδ:express genes encoding proteins of liver and muscles involved in the β oxidation of fatty acids and dissipation of free energy as heat.

Adrenoleukodystrophy: Deficiency in -oxidation of very long-chain fatty acids

Zellweger syndrome: Defect in protein import, giving rise to “ghost peroxisomes”

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An apparent amorphous mass enclosed by a nuclear envelope,Literally mean central core of the body or object.

Within:Chromosomes

ChromatinNuclear matrix

Fibrillar networkNucleoli

r-RNA and ribosomesNucleoplasm

Fluid of the nucleus

NUCLEUS

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The nuclear envelopeComponents:

Two cellular membranesBarrier to ions, solutes, macromolecules

Membranes fused to form poresComplex assemblies of proteins

Outer membraneRibosomesContinuous with RER

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Inner membraneBound to nuclear lamina

Filamentous networkNuclear lamina

Supports envelopeAttachment of chromatin

Nuclear lamina fibersProteins – lamins superfamily – Intermediate filaments of cytoplasm.

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The nuclear pore complex (NPC)Large numbers of proteins – synthesized in cytoplasm and transported into the nucleus

RNAs manufactured in nucleus – transported to cytoplasm

NPC is made up of about 50 proteins called nucleoporins.

Show both selective and non selective movements of ions and substances.

Larger proteins(RNA polymerases)need special mechanisms to move from cytoplasm into the nucleus.Signal system….

Expenditure of energy by GTP hydrolysis.RNA move from nucleus to cytoplasm

through these pores.

The nuclear envelopeComponents:

The nuclear pore complex (NPC)

Eukaryotic Nucleus - Structure

ChromatinRepresents substance of chromosomes.Each chromatid in a chromosome represents one

DNA molecule that occurs in a highly condensed form.

The nucleic acids present in the chromatin is mostly DNA but small ammount of RNA is also present.

Chromatin is a combination of DNA and protein.The most abundant proteins are histones(5

types),NUCLEOSOMES.Other proteins include enzymes like DNA and RNA

polymerases,Protins involved in the regulation of DNA transcription and replication.

Chromatin occurs in two forms, Euchromatin Stains lightly,partially or completely uncoiled,active transcription. Hetrochromatin Stains deeply,highly

coiled,generally inactive include noncoding regions,telomere and centromere.

Constitutive heterochromatinFacultative X chromosome inactivation, bar

b0ody.

NUCLEOLUSAlso called micronucleus.Nucleolonema,network of Strands containing RNA. Size varies depending upon the activity.

Nucleoli are formed around specific genetic loci called nucleolar organizing regions (NORs).

Consists of two parts. Fibrillar part.(site for rRNA

transcription).Genes for 28s,18s and 5.8s are located there.

Granular part.(assembly of ribosomal subunits takes place there).