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Chapter 1

An Overview of Cellsand Cell Research

Introduction

What is a Cell?

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There is a unity and diversity among present-ay ce s n terms o t e r evo ut on rom a

common ancestor.

Cells contain some basic properties that make

models.

The First Cell

Nucleic acids are capable ofdirecting their own self-rep cat on.

The RNA world is thought to

have been an early stage ofchemical evolution based onself-replicating RNAmolecules.

components of all present-day biological membranes,including the plasmamembranes of bothprokaryotic and eukaryoticcells.

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The Origin and Evolution of Cells

Prokaryotic cells (bacteria) lack a nuclear envelope.

Eu aryot c ce s ave a nuc eus n w c t e genet cmaterial is separated from the cytoplasm.

Eukaryotic Cells

Eukaryotic cells contain a variety of membrane-enclosed organelles within their cytoplasm.

Nucleus, Mitochondria, Chloroplast, ER, Golgi,Lysosome, Peroxisome, Cytoskeleton protein etc.

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Present-Day Prokaryotes

Archaebacteria were prevalent inrimitive Earth and often live in

extreme environments.

Eubacteria are a large group oforganisms (including commonforms of bacteria) that live in a widerange of environments, including

, ,

(e.g., human pathogens).

Cyanobacteria, the largest and mostcomplex prokaryote, synthesizes itsenergy from photosynthesis.

The Origin of Eukaryotes

Endosymbiosisone cell livinginside anotherma havehelped eukaryotic organellesto evolve.

Mitochondria and chloroplasts arethought to have evolved fromeubacteria living in larger cells.

It has been proposed that thegenome o eu aryotes arosefrom a fusion ofarchaebacterial andeubacterial genomes.

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Single Cell Eukaryotes

Yeasts are the simplest eukaryotes; more complex thanbacteria easts are much smaller and sim ler than thecells of animals or plants.

Saccharomyces cerevisiae Amoeba proteus

Multicellular Organisms

Human cells are organized intofive main tissue systems:epithelial tissue, connective

, , ,and muscle. Epithelial cells form sheets that cover

the surface of the body and line theinternal organs.

Connective tissues include bone,cartilage, and adipose tissue.

spaces between organs and tissues inthe body.

Blood contains red blood cells(erythrocytes) and white blood cells.

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Yeast

C. elegans

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Drosophila

Mammals

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Arabidopsis thaliana

Chapter 2

The Composition of Cells

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Introduction

Cells are capable not only ofself-replicationbut also of performing a wide range ofspecialized tasks (chemical & physical reactions)in multicellular organisms.

MacromoleculesThe chemical composition of cells and the properties of the moleculestherein are ultimately responsible for all cellular activities.

Water (70%), macromolecules (carbohydrates, proteins, lipids, nucleic.

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Carbohydrates The carbohydrates include simple sugars as well as

polysaccharides.

Monosaccharides are representative simple sugars with the

2 n.

A glycosidic bond links a small number of monosaccharidestogether to form an oligosaccharide.

Carbohydrates

Glycogen and starchare two commonpolysaccharides thatact as glucose storage

in animal and plantcells.

glucose molecules andis the principalstructural componentof plant cell walls.

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Lipids Lipids, key energy source,

are ma or com onents ofcell membranes, and playan important role in cellsignaling.

Fatty acids are the

simplest lipids and consistof long hydrocarbonchains.

Lipids Triacylglycerols (or fats) store fatty acids and consist of three fatty

acids linked to a glycerol molecule.

Phospholipids are the principal components ofcell membranesand consist of two fatty acids joined to a polar head group, and ah dro hobic tail.

Amphipathic molecules are part water-soluble and part water-insoluble.

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Cholesterol and steroid hormones

Steroid hormones, such asestrogens andtestosterone, arederivatives of cholesteroland act as signalingmolecules both within andetween ce s.

Nucleic Acids

Deoxyribonucleic acid (DNA) is one of the principalinformational molecules of the cell and is located in

.

Different types of ribonucleic acid (RNA) participate in

a number of cellular activities.

Messenger RNA (mRNA) carries information from DNAto the ribosomes.

osoma an trans er r an t ,respectively), are involved in protein synthesis.

DNA and RNA are polymers of nucleotides, whichconsist of purine and pyrimidine bases linked tophosphorylated sugars.

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Components of nucleic acids

-DNA consists of twopurines, adenine and

,pyrimidines, cytosineand thymine.

-RNA consists ofadenine, guanine,

,

in place of thymine.

-Differences bet.DNA & RNA.

All nucleotides have a common structure

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Native DNA is a double helix of

complementary antiparallel chains

Hydrogen bondingbetween complementarybase pairs (A-T or G-C)holds the twostrands together

Copyright (c) by W. H. Freemanand Company

Polymerization of nucleotides

Phosphodiester bonds formbetween the 5 phosphate of onenucleotide and the 3 hydroxyl ofanother.

Oligonucleotides are smallpolymers containing only a fewnucleotides.

Information in DNA and RNA isconveyed by the order of thebases in the polynucleotide chain.

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Proteins Proteins execute the tasks directed by the genetic

information of the cell.

The most fundamental property of proteins is their ability toact as enzymes, which catalyze nearly all the chemicalreactions in biological systems.

Polymers of 20 different amino acids form proteins.

Proteins The amino acids can be

grouped into four broadcategories, depending

their side chains.

Those with nonpolar sidechains

Those with hydrophobicside chains

Those with side chains thatcontain sulfur atoms

And, those with side chainsthat contain veryhydrophobic aromatic rings

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Proteins Peptide bonds join amino acids together.

Po ypept es are near c a ns o am no ac s, usua yhundreds or thousands of amino acids in length.

The defining characteristic of proteins is that they arepolypeptides with specific amino acid sequences.

Proteins Protein structure consists of four levels.

The primary structure is the sequence of amino acidsin the proteins polypeptide chain.

The secondary structure is the regular arrangement ofamino acids within localized regions of thepolypeptide.

An helix and a sheet are two types of secondarystructures.

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Proteins Tertiary structure is the third level and consists of the folding of

the polypeptide chain as a result ofinteractions between the sidechains of amino acids that lie in different regions of the primarysequence.

Quarternary structure is the ourth level and consists o theinteractions between different polypeptide chains in proteinscomposed of more than one polypeptide.

Cell Membranes

The structure of a cellmembrane functions to separatethe interior of the cell from itsenvironment and to define the

internal compartments ofeukaryotic cells, including thenucleus and cytoplasmicorganelles.

All cell membranes share acommon structural organization:bilayers of phospholipids withassociated proteins.

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Membrane Lipids Phospholipid bilayers forma stable barrier betweenwo aqueous compar men sand represent the basicstructure of all biologicalmembranes.

Lipids constituteapproximately 50% of the

.

Lipid bilayers behave as two-dimensional fluidity.

Cholesterol plays a distinctrole in determiningmembrane fluidity.

Membrane Proteins

Integra mem raneproteins

Peripheral membraneproteins

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Chapter 4

Fundamentals ofMolecular Biology

Flow of enetic information

Heredity, Genes and DNA

Gene Function

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Central Dogma :

Genetic information always flows from

DNA RNA Protein?

one gene-one enzyme -> one gene-one polypeptide

Central Dogma :

Genetic information always flows from

?

Reverse Transcriptionand reverse

Howard Temin and David Baltimore(1970)

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What We Are Doing With Cloned Genes!

Reverse & Forward Genetics

Chromosomes and their Behavior(diploid vs haploid)

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Haploids and diploids

A haploid organism has a single copy of eachchromosome and its phenotype is a consequence of that

A diploid organism has two copies of each chromosomeand thus two copies of each gene

The two copies of each gene may be the same or thecopies may be different. Different forms of each gene aretermed alleles

p o s t at carry ent ca a e es are terme

homozygous

Diploids that carry different alleles are termedheterozygous