Activity 1 - Cell Ultrastructure

Activity 1: CELL ULTRASTRUCTURE

Reporters (Group 1):Guillermo, Janina Suzette C.

Infante, Norelle Micah S.Larumbe, Jovet Emmanuel S.

What are cells?

• structural and functional unit of all living organisms

• sometimes called as the “building block of life”

• small compartments that hold the biological equipment necessary to keep an organism alive and successful

• living things may be single-celled or they may be very complex such as a human being.

• There are two basic types of organisms based on cell type: Prokaryotic and Eukaryotic

– Prokaryotic cells are divided into the domains Bacteria and Archaea.

– Eukaryotic cells make up the more familiar Domain Eukarya.

http://www.ncsu.edu/project/bio183de/Black/prokaryote/prokaryote1.html




Structural Similarities

PROKARYOTES

PROKARYOTESMainly divided into because of the Ribosomal RNA sequencing work of Carl Woese, Ralph Wolfe and co workers.

EUBACTERIA: Escherichia coli, Pseudomonas streptococcus, and Staphylococcus.

ARCHAEA: Methanogens, Halophiles and Thermacidophiles

• Prokaryotes are the smallest forms of life that can live independently.

• Most prokaryotes are tiny single cells, but some can form larger, multi-celled structures.

• The first life on earth consisted of prokaryotic cells.

• The most familiar prokaryotes are bacteria.

http://www.ncsu.edu/project/bio183de/Black/wrap/prokaryote_interactive/bacterial_size/bacterial_size.html


http://www.ncsu.edu/project/bio183de/Black/wrap/prokaryote_interactive/first_life/first_life.html


PARTS AND FUNCTION1. CELL WALL – The cell wall of bacteria protects the cell from osmostic shock and physical damage. In addition, it also confers rigiditiy and shape of bacterial cells.• Although bacterial cell walls all consist

of peptidoglycan, also known as murein or mucopeptide, they differ in certain properties in two groups of bacteria, namely gram-negative and gram-positive.

Cell wall is made up of GLYCOCALYX. These are polysaccharide layers in the bacterial cell that dictates PATHOGINECITY.

PARTS AND FUNCTION2. CYTOPLASMIC MEMBRANE - The cytoplasmic membrane encloses the cytoplasm. It regulates the specific transport of substance between the cell and the environment. The cytoplasmic membrane contains 2 main components: lipid and protein.• The lipid component of the bacterial cell is

phospholipid bilayer.• Hydrophilic heads and Hydrophobic tails

(saturated and unsaturated chains of fatty acids. • Membrane proteins are located in various

positions within the membrane, through specific interactions with phospholipid molecules.

PARTS AND FUNCTIONHow do bacteria store genetic information?Genetic information in bacteria is stored in the

sequence of DNA in two forms, that is (1) bacterial chromosome and (2) plasmid.

PARTS AND FUNCTIONBACTERIAL CHROMOSOME • Location: Within nucleoid

region , not surrounded by nuclear envelope.

• Component: Single, double stranded, circular DNA. Also contains RNA and proteins that take part in DNA replication, transcription and regulation of gene expression. DNA does not interact with protein histone.

• Information: Contain genes essential for cellular functions.

PLASMID• Location: In cytosol

of bacterial cells.• Number: From 1 to

several.• Size: Much smaller

than chromosomes.• Components: Single,

double stranded, circular DNA.

• Information: Contains drug resistant genes as well as heavy metal resistant genes. Not essential for growth and metabolism of bacteria.

PARTS AND FUNCTION5. RIBOSOMES – Important in protein synthesis. • TRANSLATION occurs in the ribosomes , in this

process nucleotide sequence of DNA is translated to specific amino acids of a protein.

• Ribosomes consists of RNA and proteins.• Bacteria cells contain 70S ribosomes

• Notes: S is Svedburg unit, which represents how rapidly particles or molecules sediment in an ultracentrifuge. The larger a substance, the greater its S value.

PARTS AND FUNCTION5. FLAGELLA – Locomotion or movement of bacteria. Most bacteria can locomote to different parts of their environment, which helps them to find new resources to survive.

Types of Flagella distribution• Monotrichous flagella: one flagellum, if it originates from

one end of the cell, it is called polar flagellum. Rapid swimming caused by the rotation of flagella.

• Peritrichous flagella: flagella surround the cell. Bundled peritrichous flagella give rise to slower forward motion than polar flagella.

Function of flagella• Chemotaxis: movement of bacteria toward or away from

chemical stimuli• Magnetotaxis: movement along the Earth's magnetic field.

Happen in magnetotatic bacteria, which contain magnetosomes including iron.

• Phototaxis: response to differences in light density. Bacteria swim to areas of particular light intensities.

PARTS AND FUNCTION7. INCLUSION BODY – Mineral storage of cell.

8. PILI • Structure: Short, thin, straight, hairlike

projections form surface of some bacteria. Composed of protein pilin, carbohydrate and phosphate. Pili are usually few.

• Function: Take part in adhesion of pathogen to specific host tissues. Sex pili are involved in genetic material exchange between mating bacterial cells.

9. ENDOSPORE - Tough, heat resistance structure that help bacteria

survive in adverse conditions.

EUKARYOTES

Eukaryotes• Eukaryotes have cells that are larger and more

complex in structure than prokaryotic cells.– Only a few prokaryotes have become as large as

eukaryotic cells.– The needs of a large, eukaryotic cell can be compared

to those of a factory.• Compartmentalization and an

endomembrane system allow eukaryotic cells to function efficiently.– Organelles serve as compartments within the cell and

the endomembrane system enhances organization and internal transport.

– Some prokaryotes have infolded membranes to provide limited compartmentalization, and a few may even utilize vesicles to concentrate enzymes or for internal transport.

Eukaryotes: Common Organelles

A. NUCLEUS• The nucleus controls cell functions through

transcription of DNA followed by protein synthesis.• Chromosomes within the nucleus consist of

chromatin which is DNA combined with proteins. – The chromatin is highly compacted to fit within the

nucleus; loosely compacted chromatin is called euchromatin.

– Chromosomes only become visible as distinct entities during cell division.

• The nuclear membrane contains pores; macromolecules can enter and leave the nucleus by this route.

• A dense region within the nucleus, called the nucleolus, synthesizes ribosomal subunits.


B. ENDOMEMBRANE SYSTEM(RER/SER -> GOLGI APPARATUS -> VESICLES ->

LYSOSOMES)Eukaryotic cells are characterized by an extensive system of internal membranes that perform important metabolic functions and regulate protein traffic within the cell. • The rough endoplasmic reticulum (RER) extends

throughout the cell and binds ribosomes.– It assists in the processing of proteins and sends them on to

the golgi apparatus. – It also serves as a membrane factory for the cell.

• The smooth endoplasmic reticulum (SER) does not bind ribosomes.– It produces many non-protein products, such as lipids and

steroid hormones.– It also stores calcium ions and plays a major role in

detoxifying harmful substances


ENDOMEMBRANE SYSTEM: GOLGI APPARATUS

• The golgi is a series of interconnected sacs that serve as a distribution center for proteins. – It receives proteins from the RER and often

completes the processing of carbohydrate groups/completes the glycosylation.

– It sorts each protein according to its destination, then sends the proteins on their way.

– It is a dynamic structure in which membranes are recycled.


ENDOMEMBRANE SYSTEM:SECRETORY VESICLE

• Once processed by the Golgi complex, secretory proteins and other substances intended for export from the cell are packaged in the secretory vesicle. The vesicle from the golgi region move to and fuse with the plasma membrane and discharge their contents to the exterior of the cell by the process of exocytosis


C. MITOCHONDRIA• Mitochondria are the power plants of the cell.

– They are quite numerous in most eukaryotic cells.– They transform food energy into ATP while consuming

oxygen and releasing carbon dixoxide. • Extracting usable energy from food is a three-step

process. – Glycolysis takes place in the cytoplasm and produces

pyruvate. – Pyruvate moves into the mitochondria and is converted to

acetyl-coA which enters the citric acid cycle. – During oxidative phosphorylation, energy is generated by

electron transport and stored in ATP. – An enzyme called ATP synthase acts as a molecular motor to

make ATP from ADP + P.


MITOCHONDRIA• Mitochondria are thought to have arisen as

endosymbionts of larger cells.– Mitochondria are similar in structure to those

bacteria that have infolded membranes.– Mitochondria contain their own DNA and replicate by

dividing.


D. CYTOSKELETON• The cytoskeleton consists of three types of

filamentous structures that form a 3-dimensional support network within the cytoplasm of eukaryotic cells. – Microfilaments (also called actin filaments) are solid

fibers with the smallest diameter.– Intermediate filaments are solid, but larger. – Microtubules are hollow rods with the largest

diameter. – Microfilaments and microtubules are dynamic

structures that can disassemble and reassemble.

CYTOSKELETON• Microfilaments and microtubules are

also involved in motility functions. – Microfilaments are responsible for

contraction and cell shape change in many cell types. • They form a contractile ring around the cell during

cell division.• They alter cell shape to generate cell movement over

a surface.• They interact with myosin to bring about muscle

contraction.


Eukaryotes: Plant Cells

Eukaryotes: Plant Cells• Plant cells have additional structures not found in

animal cells. • The cell wall is a supporting structure that

surrounds plant cells.– The cell wall is made of cellulose fibrils plus a few other

macromolecules, such as pectin. – Adjacent cells are connected by plasmodesmata that

extend through the cell walls. • The central vacuole stores a variety of molecules

and creates turgor pressure.• Plastids are organelles unique to plant cells.

– Chloroplasts are designed for photosynthesis.– Other kinds of plastids contain pigments or store starch.

Eukaryotes: Animal Cells


• Lysosomes are the "cleanup crews" of the cell.– They contain enzymes that digest

cellular debris and invading microorganisms.

– They also assist in disposing of defective or worn-out organelles.


• Peroxisomes are small membrane-bound compartments that contain peroxidase.– They perform several different

functions involving oxidation.– They produce their own membranes,

and sometimes replicate by splitting.


• The centrosome and centrioles assist in microtubule organization within the cytoplasm and serve as basal bodies for flagella and cilia.

References:• Madigan., M.T., Martinko., J.M., Stahl., D.A. and Clark.,

D.P. (2012). Biology of Microorganisms. 13 edition. Boston and London. Pearson.

• Atlas., R.M. (1995). Principles of Microbiology. 1st edition. London and New York. Mosby-Yearbook, Inc.

• Talaro., K and Talaro., A. (1993). Foundations in Microbiology. Wm. C. Brown Communication, Inc.

• Hogg., S. (2006). Essential Microbiology.Wiley.• www.micro.magent.fsu.edu/cells/bacteriacell.html

Activity 1 - Cell Ultrastructure

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