Cell structure & its organisation
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Transcript of Cell structure & its organisation
Cell Structure & its organization
By S.Kandhan ( M.tech) 1st year
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.
By S.Kandhan ( M.tech) 1st year
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
By S.Kandhan ( M.tech) 1st year
• 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.
By S.Kandhan ( M.tech) 1st year
By S.Kandhan ( M.tech) 1st year
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.
By S.Kandhan ( M.tech) 1st year
Cell divisions
By S.Kandhan ( M.tech) 1st year
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
By S.Kandhan ( M.tech) 1st year
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.
By S.Kandhan ( M.tech) 1st year
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
By S.Kandhan ( M.tech) 1st year
Visualizing Cells
By S.Kandhan ( M.tech) 1st year
By S.Kandhan ( M.tech) 1st year
Miscroscope
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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
By S.Kandhan ( M.tech) 1st year
The Cell
Nucleus(contains DNA)
Eukar yotic cell
Prokar yotic cell
DNA(no nucleus)
Organelles
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By S.Kandhan ( M.tech) 1st year
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)
By S.Kandhan ( M.tech) 1st year
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
By S.Kandhan ( M.tech) 1st year
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
By S.Kandhan ( M.tech) 1st year
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
By S.Kandhan ( M.tech) 1st year
Prokaryotic Cell
By S.Kandhan ( M.tech) 1st year
Prokaryotic cell
By S.Kandhan ( M.tech) 1st year
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
Prokaryotes - Cell Wall Gram-Positive & Gram-Negative
Images: Sources UnknownFrom the Virtual Microbiology Classroom on ScienceProfOnline.com
By S.Kandhan ( M.tech) 1st year
Gram staining
By S.Kandhan ( M.tech) 1st year
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
By S.Kandhan ( M.tech) 1st year
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.
By S.Kandhan ( M.tech) 1st year
By S.Kandhan ( M.tech) 1st year
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:
By S.Kandhan ( M.tech) 1st year
• 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
By S.Kandhan ( M.tech) 1st year
Cilium, cilia
• Short whip-like “appendage”– move material past
cell – linings of trachea &
bronchi
• similar to flagellum (longer) on sperm cell
By S.Kandhan ( M.tech) 1st year
Plasmid
• Extra chromosomal DNA•They have High copy number•They are used in Genetic Engineering
By S.Kandhan ( M.tech) 1st year
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)
By S.Kandhan ( M.tech) 1st year
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).
By S.Kandhan ( M.tech) 1st year
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
By S.Kandhan ( M.tech) 1st year
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.
By S.Kandhan ( M.tech) 1st year
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
By S.Kandhan ( M.tech) 1st year
Plant cell
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Animal cell
Animal cell
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By S.Kandhan ( M.tech) 1st year
By S.Kandhan ( M.tech) 1st year
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>>>>>>……
By S.Kandhan ( M.tech) 1st year
Membrane Function
• Internal membranes provide structural order for metabolism
• Form the cell's organelles• Compartmentalize chemical reactions
By S.Kandhan ( M.tech) 1st year
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
By S.Kandhan ( M.tech) 1st year
Membrane Structure
Phospholipids are the major structural component of membranes.
Phospholipid
By S.Kandhan ( M.tech) 1st year
Membrane Structure
All membranes are phospholipid bilayers with embedded proteins.
Label the:
Hydrophilic heads
Hydrophobic tails
Phospholipid Bilayer
By S.Kandhan ( M.tech) 1st year
• 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
By S.Kandhan ( M.tech) 1st year
Plasma Membrane Components
• Glycoproteins and glycolipids are proteins/lipids with short chain carbohydrates attached on the extracellular side of the membrane.
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Fig. 5-1a
Cholesterol
Glycoprotein
Glycolipid
Carbohydrate ofglycoprotein
Phospholipid
Microfilamentsof cytoskeleton
Integrin
By S.Kandhan ( M.tech) 1st year
By S.Kandhan ( M.tech) 1st year
Fig. 5-1c
Messenger molecule
Activatedmolecule
Receptor
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Fig. 5-1d
By S.Kandhan ( M.tech) 1st year
Transport of Substances Across the Plasma Membrane (PM)
1. Passive Transport – (Simple) Diffusion– Facilitated diffusion– Osmosis
2. Active Transport3. Bulk Flow
– Endocytosis– Exocytosis
By S.Kandhan ( M.tech) 1st year
Simple Diffusion
small, nonpolar molecules(ex. O2, CO2)
Polar molecules(ex. Glucose, water)
ions(ex. H+, Na+, K+)
LIPID-SOLUBLE WATER-SOLUBLE
LIPID-SOLUBLE
By S.Kandhan ( M.tech) 1st year
Facilitated Diffusion
Passive transport protein
Lower concentration
Higher concentration of
By S.Kandhan ( M.tech) 1st year
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
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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
By S.Kandhan ( M.tech) 1st year
By S.Kandhan ( M.tech) 1st year
By S.Kandhan ( M.tech) 1st year
Osmosis and Plant Cells
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Active Transporttell the story…
ATPATP P
ADP
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Bulk Flow
• Vesicles are used to transport large particles across the PM.– Requires energy
• Types:– Exocytosis– Endocytosis
• Phagocytosis, pinocytosis, receptor-mediated
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Vesicle forming
Endocytosis
Endocytosis can occur in three ways• Phagocytosis ("cell eating")• Pinocytosis ("cell drinking")• Receptor-mediated endocytosis
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Vesicle
Fluid outside cell
Protein
Cytoplasm
Exocytosis
By S.Kandhan ( M.tech) 1st year
By S.Kandhan ( M.tech) 1st year
Cytoplasm
• Cytoplasm is the watery gel (Jello!) inside a cell….it’s goop! It holds the ORGANelles.
By S.Kandhan ( M.tech) 1st year
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
By S.Kandhan ( M.tech) 1st year
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
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Cytoskeleton
• Protein "rods," filaments, and tubes running through cytosol
• Maintain or change shape of cell
• Move organelles
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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
By S.Kandhan ( M.tech) 1st year
By S.Kandhan ( M.tech) 1st year
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.
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Golgi apparatus• Series of flat
membranous sacs• Modifies,
concentrates, & packages proteins for secretion, exocytosis
• Movement to plasma membrane
• Production of lysosomes.
By S.Kandhan ( M.tech) 1st year
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
By S.Kandhan ( M.tech) 1st year
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
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Peroxisomes
• Resemble lysosomes, but not from Golgi apparatus
• Enzymes oxidize toxins and remove free-radicals.
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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
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Secretory vesicles
• Packages of chemicals for export (exocytosis)– hormones– digestive enzymes– sweat– mucus
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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
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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
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Endoplasmic reticulum (ER)
• Network of membranes enclosing spaces (cisternae) separate from rest of cytosol.
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Endoplasmic reticulum (ER)
• Rough ER – Associated with
ribosomes – Production of
proteins for membranes or export (exocytosis, secretion).
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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.
By S.Kandhan ( M.tech) 1st year
By S.Kandhan ( M.tech) 1st year
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
By S.Kandhan ( M.tech) 1st year
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
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Ribosomes
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Ribosomes• Very tiny
– invisible under light microscope
• Dense specks of ribosomal RNA• Free in cytoplasm or membrane-bound (ER)
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Ribosomes
• Sites of protein synthesis – mRNA specifies sequence of amino acids – some proteins packaged in vesicles by ER
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Nucleus
• Enclosed in nuclear envelope
• Residence of chromosomes, DNA
• Active in synthesis & export of RNA
• Directs protein synthesis, development of cell
By S.Kandhan ( M.tech) 1st year
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
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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.
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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).
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• 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)
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Chloroplast A member of plant organelles
family called plastids:
leukoplast
chromoplasts
chloroplasts
thylakoids
Inner membranous
system, outside of it
is stroma
• photosynthesis
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Chloroplasts
• Chloroplasts are only in plant cells• They contain chlorophyll, which helps
make energy/food from sunlight• Chlorophyll is green in color.
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Chloroplasts
• Derived form photosynthetic bacteria• Solar energy capturing organelle
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Photosynthesis• Takes place in the chloroplast• Makes cellular food – glucose
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By S.Kandhan ( M.tech) 1st year
Similarities
• Both contain:• Nucleus, Nuclear Envelope, Chromosomes-
which carry the genes or the DNA.• Cytoplasm• Mitochondria• Cell membranes
By S.Kandhan ( M.tech) 1st year
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.
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Major difference
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