cell structure and taxonomy
DESCRIPTION
Microbiology LectureTRANSCRIPT
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CELL STRUCTURE AND TAXONOMY
PowerPoint Presentation Prepared by Frances Rowena H. Mercado, MAED General Science
Microbiology and Parasitolgy - Chapter II
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What is a cell?
The fundamental living unit of any organism. Metabolism- refers to all of the chemical
reactions that occur within a cell. What are the importance of metabolism? Growth, reproduction and irritability. Mutation-accidental changes in the genetical
material.
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Cells are classified as…
Prokaryotes Do not have complex system of membranes and
organelles. Bacteria and Archaea
Eukaryotes More complex cells, containing true nucleus and
many membrane bound organelles. Algae, protozoa, fungi, plants, animals and
humans.
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Acellular and Cellular Microbes
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Relative Sizes of Microorganisms
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Eukaryotic Cell
eu=true; karyo=nucleus Have true nucleus, DNA is enclosed by a
nuclear membrane. 10X larger than most prokaryotic cells.
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Eukaryotic Animal Cell
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Eukaryotic Cell Structures
Cell Membrane Nucleus Cytoplasm Endoplasmic Reticulum Ribosomes Golgi Complex
Lysosomes and Peroxisomes
Mitochondria Plastids Cytoskeleton Cell Wall Flagella and Cilia
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Cell Membrane
Enclosed and keep the cell intact.
Composed of large molecules of proteins and phospholipids.
Like a “skin” Regulates passage of
substances in and out. Selective permeability
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Nucleus
Controls the functions of the entire cell.
“command center” 4 components:
Nucleoplasm Nuclear membrane Chromosomes Nucleolus
back
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Cytoplasm
Semifluid, gelatinous nutrient matrix
Contains the “organelles”
Organelles has highly specific functions which maintains the cells and allow it to properly perform its actvities.
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Endoplasmic Reticulum
Highly convoluted system of membranes that are interconnected to form a transport network tubules and flattened sacs within the cytoplasm. Rough ER Smooth ER
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Ribosomes
18 to 22 nm in diameter
consists of rRNA play important part in
protein synthesis free or attached in the
RER
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Golgi Complex
Stack of flattened, membranous sacs
Packages newly synthesized proteins into small, membrane-enclosed vesicles for storage within the cell or export outside the cell (exocytosis).
“packaging plants”
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Lysosomes and Peroxisomes
Lysosomes contain lysozyme and
other digestive enzymes phagocytosis and
autolysis
Peroxisomes where hydrogen
peroxide is both generated and broken down
found in mammalian liver cells
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Mitochondria
Where most of the ATP (energy carrying molecules) are formed by cellular respiration.
Energy is released from glucose molecules and other nutrients to drive other cellular functions.
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Plastids
Contains various photosynthetic pigments.
Chloroplasts- one type of plastid, contain a green, photosynthetic pigment called chlorophyll.
Found in plant cells and algae.
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Cytoskeleton
System of fibers present throughout the cytoplasm.
Strengthen, support and stiffen the cell, giving its shape. Microtubules- slender,
hallow tubules (tubulins). Microfilaments- Slender,
thread-like contractile structures which facilitate cell contraction.
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Cell Wall
External structures that provide rigidity, shape, and protection.
May contain cellulose, pectin, lignin, chitin and some mineral salts. Cellulose-
polysaccharide, present in algae and plants
Chitin- present in fungi and exoskeleton of arthropods.
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Presence or absence of cell wall in various types of cells.
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Flagella and Cilia
Flagella- relatively long, thin structure, the organelle of locomotion.
Cilia- tend to be more shorter (hair-like), thinner and more numerous
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Prokaryotic Cells
10X smaller than eukaryotic cells Very simple cells than eukaryotic cells Do not contain membrane-bound organelles Reproduce by binary fission Includes bacteria and archaeans
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Typical Prokaryotic Cell
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Prokaryotic Cell Structure
Cell Membrane Chromosome Plasmid Cytoplasm Cytoplasmic particles
Bacterial Cell Wall Glycocalyx Flagella Pili (Fimbriae) Endospores
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Cell Membrane
Enclose the cytoplasm Similar in structure and
function to the eukaryotic cell membrane.
Consists of proteins and phospholipids.
Selectively permeable
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Chromosome
Consists of a single, long, supercoiled, circular DNA molecule.
Serves as the control center of the bacterial cell.
Capable of replicating itself, guiding cell division, and directing cellular activities. A bacterial cell may contain
between 850 and 6,500 genes
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Plasmid
Small, circular molecules of double-stranded DNA that are not part of the chromosome.
May contain 10 to hundred genes
May or may not be present in bacterial cell.
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Cytoplasm
Semi-fluid, consists of water, enzymes, dissolved oxygen, waste products, essential nutrients, proteins and carbohydrates, and lipids.
No organelles.
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Cytoplasmic Particles
Many tiny particle in the bacterial cytoplasm.
Most of these are clusters of ribosomes- polyribosomes or polysomes.
Site of protein synthesis.
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Bacterial Cell Wall
Rigid exterior cell wall that defines the shape of bacteria.
Consist of a complex macromolecule known as peptidoglycan. Gram positive
bacteria- thick layer Gram negative
bacteria- thinner layer
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Gram Stain
The most widely used procedure for staining bacteria.
Developed over a century ago by Dr. Hans Christian Gram.
Bacteria are grouped as Gram-negative and Gram-positive
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Glycocalyx
Slimy, gelatinous material produced by the cell membrane and secreted outside the cell wall. Slime layer- not highly
organized and is not firmly attached to the cell wall.
Capsule- highly organized and firmly attached to the cell wall.
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Flagella
Thread-like, protein appendages that enable the bacteria to move.
Flagellated bacteria are said to be motile. monotrichous (A) lophotrichous (B) amphitrichous (C) peritrichous (D)
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Pseudomonas aeruginosa Spirillum
lophotrichous
amphitrichous
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Pili (Fimbriae)
Hair-like structures, most often observed on Gram-negative bacteria.
Kinds: Pili that enables transfer
of genetic material from one bacterial cell to another (conjugation).
Pili that enable bacteria to anchor themselves to surfaces.
E. coli fimbriae
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Endospores
Formed by a few bacteria when the environment is unfavorable for their survival.
Sporulation- process of forming endospore.
Resistant to heat, cold, drying and most chemicals. Bacillus thuringiensis with
terminal endospore.
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Sporulation
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The Discovery of Endospores
John Tyndall concluded that certain bacteria can be killed by simple boiling, while others cannot be killed.
Tyndallization Ferdinand Cohn called the
small bodies inside the bacteria “spores”.
He concluded that spores are heat resistant.
John Tyndall
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EUKARYOTIC CELLS
PLANT TYPE ANIMAL TYPE PROKARYOTIC CELLS
Biologic distribution All plants, fungi, and algae
All animals and protozoa All bacteria
Nuclear membrane Present Present Absent
Membranous structures other than cell membrane Present Present
Generally absent except for mesosomes and photosynthetic membranes
Microtubules Present Present Absent
Cytoplasmic ribosomes (density)
80S 80S 70S
Chromosomes Composed of DNA and proteins
Composed of DNA and proteins
Composed of DNA alone
Flagella or ciliaWhen present, have a complex structure
When present, have a complex structure
When present, flagella have a simple twisted protein structure; prokaryotic cells do not have cilia
Cell WallWhen present, of simple chemical constitution; usually contains cellulose
Absent Of complex chemical constitution, containing peptidoglycan
Photosynthesis Present Absent Present in cyanobacteria and some other bacteria
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Prokaryotic Cell Reproduction
Prokaryotic cells reproduce by binary fission.
One cell (parent cell) splits into half to become two daughter cells.
Before a prokaryotic cell can divide into half, its chromosomes must be duplicated.
Generation time- varies from one bacterial species to another (ex. E. coli, 20 mins.)
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Eukaryotic Cell Reproduction
Eukaryotic cell reproduce in a process called mitosis.
Mitosis the type of division that gives rise to daughter cells for the purpose of tissue growth, regeneration or asexual (vegetative) reproduction.
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Let’s Review….
INTERPHASE
PROPHASE
METAPHASE ANAPHASE
TELOPHASEMITOSIS
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Taxonomy
Taxonomy is the science of classification of living organism.
Consists of 3 but interrelated areas: Classification- arrangement of organisms into
taxonomic groups (taxa). Nomenclature- assignment of names Identification- process of determining whether
an isolate belongs to a taxa.
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Microbial Classification
Carolus Linnaeus- established the binomial nomenclature
genus + specific epithet Genus- capitalize the
first letter Specific epithet- not
capitalized
“sp.”- single specie, “spp.”- more than one specie
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Taxonomic Hierarchies Species- group of related organism/strains Genus- collection of related species Family- collection of similar genera Order- collection of similar families Class- collection of similar orders Phylum/Division- collection of similar
classes Kingdom- collection of similar
phyla/divisions Domain- collection of similar kingdoms
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The 5-Kingdom Classification
Founded in 1969 by Robert H. Whittaker.
Prokaryotes were placed in Kingdom Monera.
Eukaryotes were placed in the other 4 kingdoms (Animalia, Plantae, Protista, & Fungi).
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The Five-Kingdom Classification Scheme
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Modern Classification
In 1978, Carl R. Woese proposed elevating the three cell types to a level above kingdom, called DOMAIN
Cells are classified into three types: ARCHAEBACTERIA EUBACTERIA EUKARYA
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The Three-Domain Classification Scheme
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That’s All Folks!
Prepare for a long QUIZ next meeting!!