Cell structure & its organisation

Cell Structure & its organization

By S.Kandhan ( M.tech) 1st year


• Anton Leeuwenhoek invented the microscope in the late 1600’s, which first showed that all living things are composed of cells. Also, he was the first to see microorganisms.


CELL

• Latin called CELLA “small room”• Cell biology • Robert Hooke in 1665,• Cells are the basic unit of all living things.• IF IT IS ALIVE, IT HAS CELLS!

The Cell: A Molecular Approach. 2nd edition.by j.coffer

http://en.wikipedia.org/wiki/Robert_Hooke


• In 1655, the English scientist Robert Hooke coined the term “cellulae” for the small box-like structures he saw while examining a thin slice of cork under a microscope.


Cell Theory

• In 1838 – 1839, German scientists Schleiden and Schwann, proposed the first 2 principles of the cell theory:– All organisms are composed of one or more cells.– Cells are the smallest living units of all living

organisms.• 15 years later, the German physician Rudolf Virchow

proposed the third principle: – Cells arise only by division of a previously existing

cell.


Cell divisions


Cell Characteristics

• Two major kinds of cells - prokaryotic cells and eukaryotic cells - can be distinguished by their structural organization.– Eukaryotic cells - Contain membrane-enclosed organelles,

including a DNA-containing nucleus– Prokaryotic cells - Lack such organelles

• The cells of the microorganisms called bacteria and archaea are prokaryotic.

• All other forms of life have the more complex eukaryotic cells


Multicellular Organisms– Some organisms consist of a single cells, others are

multicellular aggregates of specialized cells. – Multicellular Organisms exhibit three major structural levels

above the cell: • Similar cells are grouped into tissues• Several tissues coordinate to form organs• Several organs form an organ system.


Basic Cell Functions• Sensing and responding to changes in surrounding

environment• Control exchange of materials between cell and its

surrounding environment– Obtain nutrients and oxygen from surrounding

environment– Eliminate carbon dioxide and other wastes to surrounding

environment

• Perform chemical reactions that provide energy for the cell

• Synthesize needed cellular components


Visualizing Cells


Miscroscope


Types of microscope

• Optical microscopy• Electron microscopy• Scanning probe microscopy• Ultraviolet microscopy• Infrared microscopy• Digital holographic microscopy• Digital pathology (virtual microscopy)• Laser microscopy• Amateur microscopy

http://en.wikipedia.org/wiki/Microscopy











The Cell

Nucleus(contains DNA)

Eukar yotic cell

Prokar yotic cell

DNA(no nucleus)

Organelles

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http://homepage.smc.edu/Thomas%20Chen/My%20Documents/Bio3%20F05/DOCUME~1/Program%20Files/TurningPoint/2003/Questions.html


Prokaryotes EukaryotesOrganisms Monera (bacteria) All other

organisms

Size Very small (1 – 5 μm)

Much larger (10 – 100 μm)

Complexity Relatively simple Complex

Cell wall Usually present (contains peptidoglycan)

Sometimes present (lacks peptidoglycan)


Prokaryotes Eukaryotes

Plasma membrane

Always present Always present

Internal membranes

May contain infoldings of the plasma membrane but usually lack internal membranes

Complex system of internal membranes divides cell into specialized compartments


Prokaryotes EukaryotesMembrane-bound organelles

Absent Present

Ribosomes Smaller and free in the cytoplasm

Larger and may be bound to ER

Cytoskeleton Absent Present

Flagella Solid flagellin; rotate

Microtubules; bend


Prokaryotes Eukaryotes

Structure of genetic material

Single, naked, circular DNA molecule

Many linear chromosomes, each made of 1 DNA molecule joined with protein

Location of genetic material

In an area of the cytoplasm called the nucleoid

Inside a membrane-bound nucleus


Prokaryotic Cell


Prokaryotic cell


Peptidoglycan is a huge polymer of interlocking chains of identical peptidoglycan monomers.

Provides rigid support while freely permeable to solutes.

Backbone of peptidoglycan molecule composed of two derivatives of glucose:

- N-acetylglucosamine (NAG)- N-acetlymuramic acid (NAM)

NAG / NAM strands are connected by inter- peptide bridges.

Prokaryotes – Cell Wall

Image: Bonding structure peptidoglycan, Mouagip; Other Image Source UnknownFrom the Virtual Microbiology Classroom on ScienceProfOnline.com

http://en.wikipedia.org/wiki/File:Mureine.svg

http://www.scienceprofonline.com/virtual-micro-main.html

http://www.scienceprofonline.com/

Prokaryotes - Cell Wall Gram-Positive & Gram-Negative

Images: Sources UnknownFrom the Virtual Microbiology Classroom on ScienceProfOnline.com




Gram staining


Prokaryotes - Glycocalyx 2. ___________________

• Polysaccharides firmly attached to the cell wall.

• Capsules adhere to solid surfaces and to nutrients in the environment.

• Adhesive power of capsules is a major factor in the initiation of some bacterial diseases.

• Capsule also protect bacteria from being phagocitized by cells of the hosts immune system.

Image: Prokaryotic Cell Diagram: M. Ruiz, Other Images Unknown Source

From the Virtual Microbiology Classroom on ScienceProfOnline.comFrom the Virtual Microbiology Classroom on ScienceProfOnline.com


http://en.wikipedia.org/wiki/File:Average_prokaryote_cell-_en.svg




Prokaryotes - Endospores

Dormant, tough, non-reproductive structure produced by small number of bacteria.

Q: What is the function of endospores?

Resistant to radiation, desiccation, lysozyme, temperature, starvation, and chemical disinfectants.

Endospores are commonly found in soil and water, where they may survive for very long periods of time.

Image: Bacillus subtilis, SPO Science Image Library, Endospore stain from Dr. Ronald E. Hurlbert,

Microbiology 101 lab manualFrom the Virtual Microbiology Classroom on ScienceProfOnline.com

An endospore stained bacterial smear of Bacillus subtilis showing endospores as green and

vegetative cells as red.


http://www.scienceprofonline.com/microbiology/what-is-a-bacterial-endospore.html

http://www.slic2.wsu.edu:82/hurlbert/micro101/pages/101lab6.html




Flagella and Cilia

• Unicellular eukaryotic organisms, sperm of animals, algae and some plants• Cilia occur in large numbers on the cell surface.• Cilia work like oars:


• Flagella are longer and are usually limited to just one or few • the motor molecule

called dynein• basal body identical

to centriole• 9 doublets of outer

microtubules• one doublet of inner

microtubule

Flagellum


Cilium, cilia

• Short whip-like “appendage”– move material past

cell – linings of trachea &

bronchi

• similar to flagellum (longer) on sperm cell


Plasmid

• Extra chromosomal DNA•They have High copy number•They are used in Genetic Engineering


Metabolism of Prokaryote- Basic concept

• Definitions– Metabolism: The processes of catabolism and

anabolism– Catabolism: The processes by which a living

organism obtains its energy and raw materials from nutrients

– Anabolism: The processes by which energy and raw materials are used to build macromolecules and cellular structures (biosynthesis)


Bacterial Metabolism ☺

Exoenzymes: Bacteria cannot transport large polymers into the cell. They must break them down into basic subunits for transport into the cell. Bacteria therefore elaborate extracellular enzymes for the degradation of carbohydrates to sugars (carbohydrases), proteins to amino acids (proteases), and lipids to fatty acids (Lipases).


Aerobic respiration– Most efficient way to extract energy from

glucose.– Process: Glycolysis

Kreb Cycle Electron transport chain

– Glycolysis: Several glycolytic pathways– The most common one:glucose-----> pyruvic acid + 2 NADH + 2ATP


Anaerobic respiration

– Final electron acceptor : never be O2 Sulfate reducer: final electron acceptor is sodium

sulfate (Na2 SO4) Methane reducer: final electron acceptor is CO2 Nitrate reducer : final electroon acceptor is

sodium nitrate (NaNO3)

O2/H2O coupling is the most oxidizing, more energy

in aerobic respiration.

Therefore, anaerobic is less energy efficient.


Fermentation Glycosis:Glucose ----->2 Pyruvate + 2ATP + 2NADH

Fermentation pathwaysa. Homolactic acid F.

P.A -----> Lactic Acideg. Streptococci, Lactobacilli

b.Alcoholic F.P.A -----> Ethyl alcoholeg. yeast


Plant cell


Animal cell

Animal cell


Plasma membrane

• The cell membrane (also known as the plasma membrane or cytoplasmic membrane) is a biological membrane that separates the interior of all cells from the outside environment

Funtions>>>>>>……

http://en.wikipedia.org/wiki/Biological_membrane

http://en.wikipedia.org/wiki/Cytoplasm

http://en.wikipedia.org/wiki/Cell_(biology)

http://en.wikipedia.org/wiki/Extracellular_space


Membrane Function

• Internal membranes provide structural order for metabolism

• Form the cell's organelles• Compartmentalize chemical reactions


Fluid Mosaic Model of the PM

• A membrane is a mosaic– Proteins and other molecules are embedded in a

framework of phospholipids

• A membrane is fluid– Most protein and phospholipid molecules can

move laterally


Membrane Structure

Phospholipids are the major structural component of membranes.

Phospholipid


Membrane Structure

All membranes are phospholipid bilayers with embedded proteins.

Label the:

Hydrophilic heads

Hydrophobic tails

Phospholipid Bilayer


• Embedded in the bilayer are proteins– Most of the membrane’s functions are

accomplished by the embedded proteins. • Integral proteins span the membrane• Peripheral proteins are on one side or the other of the

membrane


Plasma Membrane Components

• Glycoproteins and glycolipids are proteins/lipids with short chain carbohydrates attached on the extracellular side of the membrane.


Fig. 5-1a

Cholesterol

Glycoprotein

Glycolipid

Carbohydrate ofglycoprotein

Phospholipid

Microfilamentsof cytoskeleton

Integrin


Fig. 5-1c

Messenger molecule

Activatedmolecule

Receptor


Fig. 5-1d


Transport of Substances Across the Plasma Membrane (PM)

1. Passive Transport – (Simple) Diffusion– Facilitated diffusion– Osmosis

2. Active Transport3. Bulk Flow

– Endocytosis– Exocytosis


Simple Diffusion

small, nonpolar molecules(ex. O2, CO2)

Polar molecules(ex. Glucose, water)

ions(ex. H+, Na+, K+)

LIPID-SOLUBLE WATER-SOLUBLE

LIPID-SOLUBLE


Facilitated Diffusion

Passive transport protein

Lower concentration

Higher concentration of

http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_facilitated_diffusion_works.html


Osmosis

• Osmosis – diffusion of water across a selectively permeable membrane

• Water moves from an area of _______ water concentration to an area of _____ water conc.– Is energy required ?

• Water travels in/out of the cell through aquaporins


Osmosis TermsConsider two solutions separated

by a plasma membrane.• Hypertonic

– solution with a relatively high concentration of solute• Hypotonic

– solution with a relatively low concentration of solute• Isotonic

– solutions with the same solute concentration


Osmosis and Plant Cells


Active Transporttell the story…

ATPATP P

ADP


Bulk Flow

• Vesicles are used to transport large particles across the PM.– Requires energy

• Types:– Exocytosis– Endocytosis

• Phagocytosis, pinocytosis, receptor-mediated


Vesicle forming

Endocytosis

Endocytosis can occur in three ways• Phagocytosis ("cell eating")• Pinocytosis ("cell drinking")• Receptor-mediated endocytosis


Vesicle

Fluid outside cell

Protein

Cytoplasm

Exocytosis


Cytoplasm

• Cytoplasm is the watery gel (Jello!) inside a cell….it’s goop! It holds the ORGANelles.


Cytoplasm

• The cytoplasm comprises cytosol – the gel-like substance enclosed within the cell membrane

• The cytoplasm is about 80% water and usually colorless

• metabolic pathways including glycolysis, and processes such as cell division

• granular mass is called the endoplasm• clear and glassy layer is called the cell cortex or

the ectoplasm

http://en.wikipedia.org/wiki/Cytosol

http://en.wikipedia.org/wiki/Cell_membrane

http://en.wikipedia.org/wiki/Metabolic_pathway

http://en.wikipedia.org/wiki/Glycolysis

http://en.wikipedia.org/wiki/Cell_division

http://en.wikipedia.org/wiki/Endoplasm

http://en.wikipedia.org/wiki/Cell_cortex

http://en.wikipedia.org/wiki/Ectoplasm_(cell_biology)


Vacuoles

• Vacuoles are spaces in the cytoplasm (gel) where food and chemicals are store

• Vacuoles are storage bubbles found in cells. They are found in both animal and plant cells but are much larger in plant cells

http://www.biology4kids.com/files/plants_structure.html


Cytoskeleton

• Protein "rods," filaments, and tubes running through cytosol

• Maintain or change shape of cell

• Move organelles

Vesicles• It is a small sac that surrounds material to be moved into or out of a

cell.• It is a small organelle within a cell, consisting of fluid enclosed by

a lipid layer membrane



Golgi apparatus

• It is organelle in the cell that is responsible for sorting and correctly shipping the proteins produced in the ER.

• The Golgi apparatus are stacks of membrane-covered sacs.

• They also package proteins to be moved out of the cell.


Golgi apparatus• Series of flat

membranous sacs• Modifies,

concentrates, & packages proteins for secretion, exocytosis

• Movement to plasma membrane

• Production of lysosomes.


Lysosomes are digestive compartments• membrane bounded sac of

hydrolytic enzymes

• enzymes hydrolyze in acidic

environment (pH 5) proteins,

polysaccharides, fats and nucleic

acids

• function is intracellular digestion of

food particles, smaller organisms and

organic components engulfing by

phagocytosis and own organic old

material by autophagy


Lysosomes• Membranous bags of

digesting enzymes,• Destroy particles taken

in by endocytosis and phagocytosis

• Remove and destroy worn out organelles

• Removal of excess cells & tissues– "cell suicide"

• Removal of bone matrix to release Ca+2


Peroxisomes

• Resemble lysosomes, but not from Golgi apparatus

• Enzymes oxidize toxins and remove free-radicals.


Centrioles

• Clusters of microtubules, usually paired near nucleus– Organize mitotic spindle– Bases (“motors”) of cilia

and flagella

• Pairs of microtubular structures• Play a role in cell division


Secretory vesicles

• Packages of chemicals for export (exocytosis)– hormones– digestive enzymes– sweat– mucus


The endomembrane system

Nuclear envelope, endoplasmic reticulum, Golgi apparatus, lysosoms, various

kinds of vacuoles and plasma membrane

• ER consist of a network of

membranous tubules and sacs

called cisternae

• ER is continuous with nuclear

envelope

• Smooth ER - cytoplasmatic

surface lacks ribosomes

• Rough ER – ribosomes are

attached to the cytoplasmatic side


Function of smooth ER – synthesis of lipids (phospholipids, steroids),

metabolism of carbohydrates (glycogen) and detoxification of drugs (barbiturates)

and poisons

Function of rough ER – secretion of proteins, glycoproteins

formation of transport vesicules to other components of endomembrane system

Golgi apparatus – sorting cell products, they are modified and stored (removes

sugar monomers and product diverse oligosaccharides)

two poles are reffered to as the cis face ad trans face


Endoplasmic reticulum (ER)

• Network of membranes enclosing spaces (cisternae) separate from rest of cytosol.


Endoplasmic reticulum (ER)

• Rough ER – Associated with

ribosomes – Production of

proteins for membranes or export (exocytosis, secretion).


Endoplasmic reticulum (ER)• Smooth ER

– NO ribosomes, membranes with integral proteins,

– Lipid metabolism & synthesis including steroid hormones,

– Absorption & transport of fats,– Enzymatic detoxification of drugs,

pesticides, etc. (natural & artificial),– Hydrolysis of stored glycogen to glucose,– Storage of Ca+2 ions in muscle cells.


Mitochondria

• in all eukaryotic cells• hundreds or thousands• two membrane, each is

phospholipid bilayer with a

unique collection of embedded

proteins

The outer membrane is smooth, the inner membrane is convoluted with infolding

called cristae

Intermembrane space

Mitochondrial matrix


Mitochondrion

• Generates most ATP– "power plant of the cell"

• Double membrane– outer smooth, sausage-

shaped– inner folded with

enzymes

• Contains own DNA, probably evolved from symbiotic bacteria


Ribosomes


Ribosomes• Very tiny

– invisible under light microscope

• Dense specks of ribosomal RNA• Free in cytoplasm or membrane-bound (ER)


Ribosomes

• Sites of protein synthesis – mRNA specifies sequence of amino acids – some proteins packaged in vesicles by ER


Nucleus

• Enclosed in nuclear envelope

• Residence of chromosomes, DNA

• Active in synthesis & export of RNA

• Directs protein synthesis, development of cell


The nucleus• Genes that control the eukaryotic

cells

• Nuclear envelope is a double

membrane, each membrane is

lipid bilayer with proteins

• perforation by pores

• chromatin – DNA, histons,

non-histon protein

• cell division – chromatin

condensate to chromosomes

• the nucleolus – synthesis of

ribosomes components


Nuclear Membrane

• The nuclear membrane allows substances to pass in and out of the nucleus.

• It surrounds the nucleus (the brain) like the turtle’s skull…protects it.


Chromosomes• Chromosomes are inside the nucleus and are

made of genes (DNA).• Genes decide the cells traits and activities (heart

cell, eye cell - such as color).


• The nucleus control protein synthesis by sending molecular messengers in the

form RNA – mRNA - messenger - TRANSCRIPTION

• is synthesized in nucleus according the DNA

• in ribosomes is genetic information translate into the primary structure of a

specific protein - TRANSLATION

• free ribosomes – suspended in the cytosol, function of protein in cytosol

• bound ribosomes are attached to outside membrane network called the

endoplazmatic reticulum;

make proteins destined into membrane and for export from the cell (secretion)


Chloroplast A member of plant organelles

family called plastids:

leukoplast

chromoplasts

chloroplasts

thylakoids

Inner membranous

system, outside of it

is stroma

• photosynthesis


Chloroplasts

• Chloroplasts are only in plant cells• They contain chlorophyll, which helps

make energy/food from sunlight• Chlorophyll is green in color.


Chloroplasts

• Derived form photosynthetic bacteria• Solar energy capturing organelle


Photosynthesis• Takes place in the chloroplast• Makes cellular food – glucose


Similarities

• Both contain:• Nucleus, Nuclear Envelope, Chromosomes-

which carry the genes or the DNA.• Cytoplasm• Mitochondria• Cell membranes


Differences• Plant cells have non-living rigid cell walls.• Plant cells contain chloroplasts which

contain chlorophyll, a green chemical needed for photosynthesis.

• Plant cells contain a large vacuole; animal cells never contain large vacuoles.

• Plant cells are regular in shape; animal cells are irregular in shape.


Major difference

Cell structure & its organisation

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