CELL STRUCTURE AND TAXONOMY

PowerPoint Presentation Prepared by Frances Rowena H. Mercado, MAED General Science

Microbiology and Parasitolgy - Chapter II

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.

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.

Acellular and Cellular Microbes

Relative Sizes of Microorganisms

Eukaryotic Cell

eu=true; karyo=nucleus Have true nucleus, DNA is enclosed by a

nuclear membrane. 10X larger than most prokaryotic cells.

Eukaryotic Animal Cell

Eukaryotic Cell Structures

Cell Membrane Nucleus Cytoplasm Endoplasmic Reticulum Ribosomes Golgi Complex

Lysosomes and Peroxisomes

Mitochondria Plastids Cytoskeleton Cell Wall Flagella and Cilia

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

Nucleus

Controls the functions of the entire cell.

“command center” 4 components:

Nucleoplasm Nuclear membrane Chromosomes Nucleolus

back

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.

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

Ribosomes

18 to 22 nm in diameter

consists of rRNA play important part in

protein synthesis free or attached in the

RER

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”

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

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.

Plastids

Contains various photosynthetic pigments.

Chloroplasts- one type of plastid, contain a green, photosynthetic pigment called chlorophyll.

Found in plant cells and algae.

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.

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.

Presence or absence of cell wall in various types of cells.

Flagella and Cilia

Flagella- relatively long, thin structure, the organelle of locomotion.

Cilia- tend to be more shorter (hair-like), thinner and more numerous

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

Typical Prokaryotic Cell

Prokaryotic Cell Structure

Cell Membrane Chromosome Plasmid Cytoplasm Cytoplasmic particles

Bacterial Cell Wall Glycocalyx Flagella Pili (Fimbriae) Endospores

Cell Membrane

Enclose the cytoplasm Similar in structure and

function to the eukaryotic cell membrane.

Consists of proteins and phospholipids.

Selectively permeable

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

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.

Cytoplasm

Semi-fluid, consists of water, enzymes, dissolved oxygen, waste products, essential nutrients, proteins and carbohydrates, and lipids.

No organelles.

Cytoplasmic Particles

Many tiny particle in the bacterial cytoplasm.

Most of these are clusters of ribosomes- polyribosomes or polysomes.

Site of protein synthesis.

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

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

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.

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)

Pseudomonas aeruginosa Spirillum

lophotrichous

amphitrichous

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

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.

Sporulation

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

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

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.)

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.

Let’s Review….

INTERPHASE

PROPHASE

METAPHASE ANAPHASE

TELOPHASEMITOSIS

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.

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

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

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).

The Five-Kingdom Classification Scheme

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

The Three-Domain Classification Scheme

That’s All Folks!

Prepare for a long QUIZ next meeting!!