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MASON / Biology / BIOL 305 / What are the characteristics of the prokaryotic cell?

What are the characteristics of the prokaryotic cell?

What are the characteristics of the prokaryotic cell?


School: George Mason University
Department: Biology
Course: Microbiology
Professor: Polayes
Term: Fall 2017
Tags: Microbiology, Biology, prokarotes, eukaryote, cells, evolution, and organelles
Cost: 25
Name: Microbiology Chapter 4 Textbook Notes (BIOL 305)
Description: Functional Anatomy of Prokaryotic and Eukaryotic Cells
Uploaded: 02/03/2018
17 Pages 248 Views 2 Unlocks

Andrew Friedman

What are the characteristics of the prokaryotic cell?

BIOL 305-001

Microbiology Chapter 4 Notes: Functional Anatomy of Prokaryotic and Eukaryotic  Cells 

I.What is an overview of comparing prokaryotic and eukaryotic cells? • Eukaryotes and prokaryotes both had nucleic acids, proteins, carbohydrates  and lipids.

• Their membrane, cell wall structure, and the absence of organelles  distinguish prokaryotes from eukaryotes.

• Prokaryotes typically…

1. DNA is not enclosed in a membrane and is usually a single arranged  chromosome.

2. Their DNA is not associated with histones (special proteins found in  eukaryotes).

3. They generally lack organelles like nuclei, mitochondria, and chloroplasts. 4. Almost always contain peptidoglycan.

What is the definition of diplococci?

We also discuss several other topics like How does the skin provide protection to the internal organs?

5. Usually divide by binary fission, a simpler process than mitosis in  Eukaryotes.

• Eukaryotes typically…

1. DNA is found in the cell’s nucleus, which is separated from the cytoplasm  by a nuclear membrane.

2. DNA has chromosomal proteins histones and non-histones.

3. Have many membrane enclosed organelles.

4. Cell walls are simple when present.

5. Cell division involves mitosis. We also discuss several other topics like What behaviors cannot be directly observed?

II. The prokaryotic cell and its size, shape, and arrangement of bacterial cells • There are more bacteria than archaea.

• 99% of natural bacteria exist in biofilms (Shiny film of bacteria that adheres  to the surface).

• Bacteria may be spherical coccus, rod shaped bacillus, and spiral. • When cocci divide, they do so in many ways, as they look like ovals. 1. Diplococci: Remain in pairs.

What is the definition of streptococci?

2. Streptococci: Remain attached in chainlike patterns.

3. Tetrads: Divide in two planes and remain in four.

4. Sarcinae: Divide in three planes and remain attached in cube like groups of  eight.

5. Staphylococci: Divide in planes and form grape like structures. • Bacilli divide in a short axis and there are fewer groupings of bacilli than of  cocci.

1. Single bacilli: Single rods.

2. Diplobacilli: In pairs after division.We also discuss several other topics like What competes with the substrate for enzyme binding?

Andrew Friedman

BIOL 305-001

Microbiology Chapter 4 Notes: Functional Anatomy of Prokaryotic and Eukaryotic  Cells If you want to learn more check out What makes a voice unique?

3. Streptobacilli: Chains.

4. Coccobacilli: Look like cocci

• Bacillus: Bacterial shape.

• Bacillus: Specific genus.

• Spiral bacteria could have one or more twists, but never straight. • Vibrios: Curved rods.

• Spirilla: Helical shape and rigid bodies that use flagella to move.  • Spirochetes: Unlike spirilla, use axial filaments to move. Don't forget about the age old question of Is the interior of the pantheon original?
Don't forget about the age old question of What is the meaning of prokaryotic cells?

• Shape is determined by its heredity.

• Most are monomorphic: One shape

• Environmental conditions allow the identification to be more difficult. • Pleomorphic: Many more shapes than one.

III. What are the structures external to the cell wall?

• The structures external to the cell wall are glycocalyx, flagella, axial  filaments, fimbriae, and pili.

A. What is the glycocalyx?

• Glycocalyx: What most prokaryotes secrete on their surface; which is a  polymer that surrounds cells.

• Bacterial glycocalyx: Viscous polymer composed of polysaccharide,  polypeptide, or both.

• Capsule: Organized and firmly attached to the cell wall; bad for cells. • Slime Layer: unorganized and loosely attached to cell wall. • Capsules are bad for cells because it could prevent from being eaten from  phagocytosis.

• Extracellular polymeric substance (EPS): A glycocalyx that helps cells  attach to an environment and facilitates communication by attaching to  various surfaces in the environment.  

• Bacteria could grow on diverse surfaces.

• EX: Vibrio cholerae: Cause of cholera, produces a glycocalyx that helps it  attach to the cells of the small intestine.

B. What is the flagella?

• What propels bacteria.

• Atrious: No flagella.

• Peritrichous: Around the entire cell.

• Polar: One or both ends of the cell.

• Monotrichous: Single flagellum in one pole.

• Lophotrichous: Multiple flagella in one pole.

Andrew Friedman

BIOL 305-001

Microbiology Chapter 4 Notes: Functional Anatomy of Prokaryotic and Eukaryotic  Cells 

• Amphitrichous: Flagella at both ends of the pole.

• Three basic parts:

1. Filament: Outermost region containing protein flagellin arranged in several  chains that intertwine and form a helix around the hollow core.

2. Hook: Filament is attached to this, which consists of a different protein. 3. Basal body: Anchors the flagellum to the cell wall and plasma membrane;  composed of a central rod with a series of rings.

• Gram negative: Has rings in the outside attached to various proteins of the  cell wall and the inside anchored to the plasma membrane.

• Gram positive: Only had rings in the outside.

• The flagella rotates from the basal body either clockwise or  counterclockwise (Eukaryotes: Wavelike motion).

• They rotate depending of their generation of energy by forming a bundle that  pushes against the surrounding liquid.

• Motility: Ability of an organism to move by itself.

• Bacterium move in a one direction in a sequence called “run” or “swim”. • “Run”: Interrupted by random changes called “tumbles”.  

• “Tumbles”: Caused by a reversal of flagellar rotation.  

• Movement helps in going to or away from a favorable environment called  taxis.

• If signal is positive, called attractant, then bacteria moves toward stimulus  with many runs and a few tumbles.

• If negative, called repellant, tubules increase as bacteria moves away from  the stimulus.

• H antigen: Useful in distinguishing among serovars, or variations within a  species.

C. What are axial filaments?

• Example of spirochetes is Treponema pallidum, the cause of syphilis. • Spirochetes move by axial filaments or endoflagella.

• Axial filaments: Fibrils that arise at the ends of the cell beneath outer sheath  and spiral around the cell.

• Rotation of the filaments produces movement of the outer sheath that  propels it in spiral motion.

D. What is the fimbriae and pili?

• Many gram-negative bacteria contain proteins called pilin, which is divided  into two types, fimbriae and pili.

Andrew Friedman

BIOL 305-001

Microbiology Chapter 4 Notes: Functional Anatomy of Prokaryotic and Eukaryotic  Cells 

1. Fimbriae: Usually surrounds the entire cell or at opposite poles, in which it  allows bacteria to stick in the cells they touch.

• Involved in forming biofilms and other aggregations on the surfaces of  liquid, glass, and rocks. When fimbriae are absent, no disease occurs. 2. Pilli: Allows for motility and DNA transfer.

• Longer than fimbriae, about 1 or 2 per cell.

• Twitching motility: Pilus makes contact by extending to another cell and  retracts as pilin subunits are disassembled.

• It is called the grappling hook model for twitching motility in jerk  movements.

• Common bacteria that do this is Pseudomonas aeruginosa, Neisseria  gonorrhoeae, and some stains of E. coli.

• Gliding motility: Smooth gliding movement of myxobacteria.  • Travel in areas of low water content.

• Conjugation: The process of bringing bacteria allowing the transfer of DNA  from one cell to another.

• Conjugation sex pili: Conjugation of one bacterium called F+ cells  connected to another bacterium of the same or different species, and DNA  from F+ cell is transferred to another one.  

IV. What is the cell wall?

• Cell Wall: Around the cell that is very complex and maintains the shape of  the cell and serves as point of anchorage for flagella.

• Almost all prokaryotes have one and it helps protects the interior from  changes in the environment.

• Major function: To prevent the cell from rupturing when the water pressure  inside is larger than outside.

A. What is the composition and characteristics of the cell wall? • Cell walls contain peptidoglycan, which could be by itself or with other  substances.  

• Contains polypeptides and disaccharides that combine and form to protect  the cell.  

• Disaccharide portion is made glucose-related monosaccharides NAG (N.  acetylglucosamine acid) and NAM (N. acetylmuramic acid)

• Alternating NAM and NAG are in rows of 10 to 65 sugars to form a  backbone.  

• Polypeptides are the adjacent rows from disaccharides.

Andrew Friedman

BIOL 305-001

Microbiology Chapter 4 Notes: Functional Anatomy of Prokaryotic and Eukaryotic  Cells 

• Tetrapeptide side chains: Four amino acids attached to NAMs in the  backbone. Every structure of a polypeptide includes this.

• EX: Penicillin interrupts with the binding of the peptidoglycan rows and the  cell is greatly weakened and undergoes lysis, which is the rupture of the  membrane and cytoplasm loss.  

1. Gram-positive cell walls

• Consists of many layers of peptidoglycan.  

• Periplasmic space: Space between cell wall and plasma membrane of gram positive bacteria, containing granular layer, which lipoteichoic acid. • Teichoic acid: In gram-positive bacteria, in which it consists of an alcohol or  a phosphate.  

• Two classes of teichoic acid are lipoteichoic acid (spans peptidoglycan layer  and links to plasma membrane) and wall teichoic acid (Linked to  peptidoglycan layer).

• Since teichoic acid is negatively charged, they could regulate the movement  of cations into and out of the cell.  

• Teichoic acids assume a role in cell growth, preventing extensive wall  breakdown and maybe cell lysis.

• Another role is to identify gram-positive bacteria by lab tests. 2. Gram-negative cell walls

• Very few layers of peptidoglycan and an outer membrane.

• Periplasm: Gel like fluid in the middle of the periplasmic space of gram  negative bacteria b/t outer membrane and plasma membrane.

• Degradative enzymes and transport proteins.

• No teichoic acids.

• Outer membrane: lipopolysaccharides, lipoproteins, phospholipids. • (-) charge: avoid phagocytosis.

• Provides barrier from detergents, antibiotics, and dig. Enzymes. • Outer membrane allows nutrients to enter due to metabolism. • Porins: Proteins that form channels, allowing some substances to go in. • Allows disaccharides, peptides, amino acids, vitamin B12, and iron. • Lipopolysaccharide (LPS): Complex molecule made up of three parts: lipid  A, a core polysaccharide, and O polysaccharide.

• Lipid A: Top layer of outer membrane, released when gram-negative  bacteria die, functioning as endotoxin, being responsible for symptoms of  with infections of gram negative bacteria.

Andrew Friedman

BIOL 305-001

Microbiology Chapter 4 Notes: Functional Anatomy of Prokaryotic and Eukaryotic  Cells 

• Core polysaccharide: Structural role providing stability, containing unusual  sugars, being attached to lipid A.

• O polysaccharide: Made of sugar molecules extending outward of the core  polysaccharide, functioning as an antigen, useful for determining species of  gram negative bacteria.

• Examples: E. Coli, H. pylori, S. enterica.  

B. What are cell walls and the gram stain mechanism?

• Gram staining depends on gram positive or negative and the reaction to the  chemicals.

1. First, the bacteria gets heated.

2. First, crystal violet forms around both gram positive and negative. 3. Iodine then forms around large crystals with the dye too large to escape  through the cell wall.  

4. Alcohol: Dehydrates peptidoglycan of gram positive cells, making it more  impermeable to crystal violet iodine.

5. Alcohol: Dissolves outer membrane, leaving small holes in peptidoglycan,  which violet iodine diffuse.

6. Safranin (Counterstain): Used to make gram negative bacteria pink. • Both bacteria absorb it, but in gram positive, the pink is masked by violet.  C. What are atypical cell walls?

• Atypical cell wall: Either a very thin wall or no wall at all.

• Example: Mycoplasma and other related microorganisms.

• Mycoplasma: Smallest living microorganism that live outside host cells • Mycoplasma was mistaken as a virus.

• Mycoplasma does not contain cell walls

• Mycoplasma contain lipids called sterol, protecting them from lysis. • Mycoplasma contain pseudomurein. Similar to peptidoglycan, but contains  N-acetyltalosaminuronic acid instead of NAM, lacking D-amino acids found  in cell walls.

• Can’t be gram stained, but is gram negative, due to no peptidoglycan. 1. Acid Fast Cell walls

• Mycobacterium and pathogenic species of Nocardia contain high conc. of  mycolic acid, preventing uptake of dyes.

• Mycolic acid: Forms a layer outside of thin layer of peptidoglycan. • Held together by polysaccharide.

Andrew Friedman

BIOL 305-001

Microbiology Chapter 4 Notes: Functional Anatomy of Prokaryotic and Eukaryotic  Cells 

• Acid-fast bacteria can be stained with carbol fuchsin, which breaks through  cell wall, goes to cytoplasm and stops removal by washing with red alcohol. • Acid fast contain red color because it's more soluble in mycolic acid than  acid alcohol.

• If mycolic acid removed, it will stain gram-positive.

D. What happens when there is damage to the cell wall?

• If damage, there is not damage to the cell host, as the cell wall is different from eukaryotic cells.

• Lysozyme: Digestive enzyme that damages cell wall.  

• Lysozyme is active in gram positive, being vulnerable to lysis.  • Lysozyme catalyzes hydrolysis of the bonds b/t sugars in repeating  disaccharide “backbone” of peptidoglycan.

• Gram positive cell almost destroyed by lysozyme.

• Protoplast: Wall-less cell, spherical & capable of metabolism. • L forms: Irregular cell walls.  

• L forms develop and respond to penicillin and lysozyme.

• L forms either live and divide or return to walled state.

• Spheroplast: Spherical structure, with remaining cellular structure and  plasma membrane in gram negative cells.  

• In order for lysozyme to damage spheroplast, a substance called EDTA  (Ethylenediaminetetraacetic acid) weakens ionic bonds, and lysozyme enters  peptidoglycan.

• Osmotic lysis: When protoplasts and spheroplasts burst in pure water  solutions enlarging the cell, although it has a lower concentration of water. • Most gram negative resistant to penicillin because it forms a layer outside  that won’t allow it to go, also having fewer peptide bridges.  

V. What are the structures internal to the cell wall?

A. What is the plasma (cytoplasmic) membrane?

• Consists mostly of phospholipids and proteins, and some carbohydrates and  sterols.

• Less strong than eukaryotic plasma membrane.

• Mycoplasma: No cell wall.

1. Structure

• It is arranged in a lipid bilayer.

• Contains a hydrophilic polar head and hydrophobic nonpolar tail. • Peripheral Proteins: Away or inside of bilayer in which it functions as  enzymes for chemical reactions.

Andrew Friedman

BIOL 305-001

Microbiology Chapter 4 Notes: Functional Anatomy of Prokaryotic and Eukaryotic  Cells 

• Integral proteins: Inside membrane, and if completely in, its called  transmembrane proteins.  

• Glycoproteins: Proteins attached to carbohydrates

• Glycolipids: Lipids attached to carbohydrates.

• Both help lubricate the cell to cell interactions.

• Move freely through cytoplasm.  

• Fluid mosaic model: Arrangement of phospholipids and proteins. 2. Functions

• Selective permeability: Determine what go in or out of the cell. • Larger molecules generally cannot enter, but smaller ones could. • Plasma membranes are important for breakdown of nutrients and production  of energy.

• Chromatophores: Infoldings of the plasma membrane that extend into the  cytoplasm.  

• Mesosomes: Bacterial plasma membranes contain one or more irregular  folds.

3. Destruction of the plasma membrane by antimicrobial agents • Alcohols and quaternary ammonium compounds are agents that damage the  plasma membrane.  

B. How is the movement of materials across membranes?

• There are two kinds of processes: called Passive and active processes • Passive process moves from an area of high concentration to low  concentration.  

• Active process moves from high to low concentration against the  concentration gradient with ATP in use.

1. Passive processes

• No use of energy.

• The passive processes are called simple diffusion, facilitated diffusion, and  osmosis.

• Simple diffusion: The movement of molecules across the membrane with a  concentration gradient.

• Important for small materials to travel such as oxygen and CO2. • Facilitated diffusion: Movement of molecules through the transmembrane  protein.

• The proteins are called transporters or permeases.

• Nonspecific and usually allow small molecules that are too hydrophilic to  enter or exit the cell.

Andrew Friedman

BIOL 305-001

Microbiology Chapter 4 Notes: Functional Anatomy of Prokaryotic and Eukaryotic  Cells 

• There are enzymes called extracellular enzymes which turn large complex  enzymes into simpler ones.  

• Osmosis: Net movement of water from high to low concentration. • Travel through transmembrane proteins or simple diffusion by aquaporins,  functioning as water channels.

• Osmotic pressure: Pressure required to prevent movement of water  molecules into solution containing some solutes.

• Lysozyme and penicillin could damage the bacterial cell walls, causing it to  rupture.

• Isotonic: When the concentration of solute equal that found inside cell. • Hypertonic: Medium having high concentration than inside the cell. • Hypotonic: Medium having lower concentration than inside the cell. 2. Active processes

• Active transport: When the cell uses ATP to move substances through the  plasma membrane.

• Amino acids, Na, K, H, Ca, Cl, and simple sugars are transported. • They could go through passive, but this is against the concentration gradient. • Depends on transporter proteins.

• Group translocation: When the substance is chemically altered across the  membrane in only prokaryotes.

• Allows the cell to accumulate various substances even in low concentrations. • Uses high energy phosphate compounds like phosphoenolpyruvic acid (PEP)  for energy.

• Phagocytosis and pinocytosis does not occur in prokaryotic cells. C. What is the cytoplasm?

• Cytoplasm: Substance in the cell membrane.

• 80% is water and contains enzymes, carbohydrates, lipids, inorganic ions,  and many low molecular weight compounds.

• Thick, aqueous, and elastic.

• In prokaryotes, the major structures are nucleoids, ribosomes, and  inclusions.

• Cytoskeleton in prokaryotes is like eukaryotes, in which the components are  MreB and ParM, crestin and StsZ, which are similar to microfilaments,  intermediate filaments, and microtubules.

• Some aspects of the cytoskeleton include cell division, maintaining cell  shape, growth, DNA movement, protein targeting, and alignment of  organelles.

Andrew Friedman

BIOL 305-001

Microbiology Chapter 4 Notes: Functional Anatomy of Prokaryotic and Eukaryotic  Cells 

• Cytoskeleton not capable of cytoplasmic streaming.

D. What is the nucleoid?

• Nucleoid: Contains single, long, double stranded DNA called bacterial  chromosome.  

• Bacterial chromosome: Contains all of the cell’s genetic information. • Are not surrounded by a nuclear envelope and don’t have histones. • Chromosome is attached to the plasma membrane.

• Proteins in the plasma membrane are responsible for the replication of the  DNA and segregation of the new chromosomes to daughter cells during cell  division.

• Plasmids: Small double stranded DNA molecules.

• Plasmids may carry genes for activities like antibiotic resistance, tolerance  of toxic metals, production of toxins, & synthesis of enzymes.

• Plasmids can be transferred from one bacterium to another.

E. What are ribosomes?

• Ribosomes: Protein synthesis occurs.

• Cytoplasm contains tens of thousands of ribosomes.

• Two subunits containing a protein called rRNA (ribosomal RNA). • Prokaryotes and eukaryotes differ in number of proteins and RNA molecules  they contain, as prokaryotes are slightly smaller and less dense. • Letter S means Svedberg units, meaning it is measured by rate of  sedimentation during centrifugation.

• Prokaryotic ribosomes are 70S ribosomes (Small 30S subunit [1 molecule of  rRNA] and a large 50S subunit [2 molecules of rRNA]).

• There are antibiotics that interfere with protein synthesis such as  streptomycin and gentamicin that attach to the 30S subunit.

• Microbial cells could be killed while eukaryotic cells is unaffected. F. What are inclusions?

• Inclusions: Reserve deposits inside the cytoplasm.

• Accumulate nutrients and use it when deficient.

• Avoids increase in osmotic pressure that results if molecules were dispersed  in the cytoplasm.  

• Magnetosomes: Membrane enclosed organelles.

• Carboxysomes: Enclosed in protein complexes.

1. Metachromatic granules

• Metachromatic granules: Large inclusion that sometimes stain red with  certain dyes such as blue.

Andrew Friedman

BIOL 305-001

Microbiology Chapter 4 Notes: Functional Anatomy of Prokaryotic and Eukaryotic  Cells 

• Volutin: Stored inorganic phosphate in a prokaryotic cell able to be used  with the production of ATP.

• Found in algae, fungi, protozoa, and bacteria.

• Characteristic of Corynebacterium diphtheriae.  

2. Polysaccharide granules

• Contain glycogen and starch, and the presence is determined by use of  iodine, in which glycogen granules appear reddish brown and starch appear  blue

3. Lipid inclusions

• Lipid storage inclusions that are revealed by staining waves with fat soluble  dyes.

• Appear in Mycobacterium, Bacillus, Azotobacter, Spirillum, and more. 4. Sulfur granules

• Energy reserve in which the bacteria oxidizes sulfur and sulfur containing  compounds.

5. Carboxysomes

• Inclusions that use the enzyme ribulose 1,5-bisphosphate carboxylase  (RuBisC [no oxygen, so not RuBisCO])

• Enzyme is required for carbon fixation.

• Bacteria include nitrifying bacteria, cyanobacteria, and acidithiobacillus. 6. Gas vacuoles

• Gas Vacuoles: Hollow cavities found in prokaryotes, including many  aquatic ones.

• Consist of rows called gas vesicles

• Gas vacuoles maintain buoyancy, so they could receive sufficient amounts  of oxygen, light, and nutrients.

7. Magnetosomes

• Inclusions of iron oxide (Fe3O4) surrounded by invaginations of the plasma  membrane.

• Found in several gram-negative bacteria.

• Bacteria use magnetosomes to move bacteria downward until they reach an  comfortable attachment site.

G. What are endospores

• Endospores: “Resting cells” that are formed by gram positive bacteria when  nutrients are scarce.

• Endospores are dehydrated cells with thick cell walls and multiple layers. • Endospores can survive extreme environments when released.

Andrew Friedman

BIOL 305-001

Microbiology Chapter 4 Notes: Functional Anatomy of Prokaryotic and Eukaryotic  Cells 

• One gram negative bacteria called Coxiella burnetii, the cause of Q fever,  form endospore like features that resist heat and chemicals.

• Sporulation/Sporogenesis: The process of endospore formation. • Sporulation occurs when carbon or nitrogen source is scarce. • The process occurs as follows…

1. Spore septum isolates newly replicated DNA and small portion of  cytoplasm.

2. Plasma membrane starts to surround DNA, cytoplasm, and membrane,  having a double layered membrane.

3. Sore septum surrounds entire chromosome, forming forespore. 4. A peptidoglycan layer forms between membranes.

5. Spore coat forms outside the membrane, being responsible for resistance of  endospores from many harsh chemicals.

6. The endospore is made and freed from outer cell.  

• Endospore might be terminally (one end), subterminal (near one end), and  centrally (center) inside the vegetative cell.

• When endospore is matured, it breaks the cell wall, killing the cell wall,  freeing the endospore.

• Endospore contains organic acid called dipicolinic acid, accompanied by a  large number of calcium ions, protecting against DNA damage.

• Germination: When an endospore returns to its vegetative state. • Germination is triggered by heat

• : Germinants: Small triggering molecules  

• Examples of gerninants: Alanine and inosine.

• Endospores enzymes break down extra layers surrounding endospore, water  enters, and metabolism resumes.

• Process does not increase number of bacterial cells.

• Endospores could survive boiling water for several hours.

VI. The Eukaryotic cell

• Larger and more complex than prokaryotic cells.

VII. What is the flagella and the cilia?

• Flagella: Few long projections used to move the cell. EX: Euglena • Cilia: Numerous and short projections. EX: Tetrahymena

• Both are anchored to the plasma membrane by a basal body and contain  cytoplasm.

• Consist of a 9+2 array of microtubules (9 pairs of microtubules arranged in a  ring, and 2 in the center of a ring) Total= (9*2)+2= 20 microtubules.

Andrew Friedman

BIOL 305-001

Microbiology Chapter 4 Notes: Functional Anatomy of Prokaryotic and Eukaryotic  Cells 

• Microtubules: Long, hollow tubes made of tubulin.

• Flagellum in eukaryotes move in a wavelike/whip manner

VIII. What is the cell wall and the glycocalyx?

• Simpler than prokaryotic cells.

• Algae and all plant consist of polysaccharide cellulose.  

• In fungi, some contain cellulose, but most contain chitin, a polymer of NAG  (N-acetylglucosamine) units.

• Yeast contain glucan and mannan.  

• Protozoa have a flexible outer protein covering called a pellicle. • Glycocalyx: Layer of material containing sticky carbohydrates in which  covers the plasma membrane.

• Glycocalyx strengthens the cell surface, helps attach cells together, and  contribute to cell to cell recognition.

• Eukaryotic cells do not contain peptidoglycan, which matters because  antibiotics act against peptidoglycan and don’t affect eukaryotic cells. IX. What is the plasma (cytoplasmic) membrane?

• Very similar to prokaryotic cells.

• Eukaryotic membranes contain carbohydrates, which serve as attachment  sites.

• Eukaryotic membranes contain sterols, complex lipids. (Bacteria  mycoplasma is the only exception to having sterols).\

• Substances can cross the membrane by simple, diffusion, facilitated  diffusion, osmosis, or active transport.  

• Group translocation does not occur in eukaryotic cells.

• Eukaryotes have endocytosis, in which it takes in a small or large particle in  the cell.

• 3 types of endocytosis are phagocytosis, pinocytosis, and receptor mediated  endocytosis.

• Phagocytosis: Pseudopods engulfs particles in the cell.

• Pinocytosis: Plasma membrane folds inwards and engulfs extracellular fluid  in the cell.

• Receptor-mediated endocytosis: Ligands (molecule binding to a larger  molecule) binds to receptors, and membrane folds inwards. (Viruses enter  the cell like this).

X. What is the cytoplasm?

• Inside membrane and nucleus.

• Cytosol: Fluid portion of cytoplasm.

Andrew Friedman

BIOL 305-001

Microbiology Chapter 4 Notes: Functional Anatomy of Prokaryotic and Eukaryotic  Cells 

• Cytoskeleton: Small rods (microfilaments and intermediate filaments) and  cylinders (microtubules).

• Provide support, shape, and assistance in transporting substances in the cell.  • Cytoplasmic streaming: Movement of eukaryotic cytoplasm from one part  of the cell to another.

• Many enzymes in cytoplasmic fluid of prokaryotes are in organelles of  eukaryotes.

XI. What are ribosomes?

• Larger and denser than prokaryotic cells.  

• Eukaryotic ribosomes are 80S ribosomes (Small 40S subunit [1 molecule of  rRNA] and a large 60S subunits [3 molecules of rRNA] ).


• Free ribosomes are unattached to any structure in the cytoplasm, which  make proteins inside the cell.

• Membrane bound ribosomes make proteins for insertion in the plasma  membrane or for export in the cell.

• 10-20 ribosomes: Polyribosomes.

XII. What are organelles?

• Organelles: Structures with different shapes and function in eukaryotic cells A. What is the nucleus

• Nucleus: The largest structure in the cell that contains almost all of the DNA  in the cell. (Some DNA are found in mitochondria and chloroplasts) • Nuclear envelope: Double membrane that surrounds nucleus. • Nuclear pores: Tiny channels in the membrane that allow the nucleus to  communicate with the cytoplasm.  

• Nucleoli: Regions where RNA is being synthesized.

• Histones: One of many basic proteins along with non-histones that are in the  nucleus.

• Nucleosome: 165 base pairs of DNA and 9 molecules of histones. • Chromatin: DNA appearance when not producing.

• Chromosomes: When chromatin coils into shorter and thicker bodies. • Eukaryotes perform mitosis and meiosis.

B. What is the endoplasmic reticulum?

• ER: Network of flattened membranous sacs called cisternae. • Most eukaryotes contain 2 types of ER

• Both types of ER synthesize phospholipids

Andrew Friedman

BIOL 305-001

Microbiology Chapter 4 Notes: Functional Anatomy of Prokaryotic and Eukaryotic  Cells 

1. Rough ER

• Continuous with the nuclear membrane.

• Contains ribosomes.

• Proteins enter the cisternae for processing and sorting,

• Cisternae sometimes attach proteins and carbohydrates to form  glycoproteins.

2. Smooth ER

• Extends from rough ER to form a network of membrane tubules. • Contain enzymes that make it more diverse than rough ER.

• Synthesizes fats and steroids, such as estrogen and testosterone. C. What is a Golgi complex

• Golgi complex: The organelle that proteins synthesized by the rough ER has  to pass through in order to be transported through other regions. • Consists of 3 to 20 cisternae.

• Transport vesicle: Gets the proteins from rough ER and transports it to the  cistern of the golgi complex.

• Transfer vesicles: Vesicle that moves proteins from one cistern to another.  • Enzymes in cisternae modify proteins to form glycoproteins, glycolipids,  and lipoproteins.  

• Secretory vesicles: Vesicle that helps proteins leave the cisternae and  deliver to plasma membrane, where they leave by exocytosis.

• Storage vesicles: Where processed proteins leave the  

vesicles. EX: Lysosome

D. What are Lysosomes

• Formed from golgi complexes, have only a single membrane, and lack an  internal structure.  

• Contain 40 different kinds of enzymes that could break down molecules. E. What are vacuoles?

• Vacuole: Space in the cytoplasm enclosed by a membrane called a  tonoplast.  

• Serve as a temporary storage molecule for substances such as proteins,  sugars, organic acids, and inorganic ions.

• Could help bring in food into the cell.

• Many plant cells use vacuoles to store metabolic wastes.

• May take up water, allowing plant cells to increase in size.

F. What is a mitochondrion?

Andrew Friedman

BIOL 305-001

Microbiology Chapter 4 Notes: Functional Anatomy of Prokaryotic and Eukaryotic  Cells 

• Number varies depending on the cell.

• Has two membranes like plasma membrane.

• Outer membrane is smooth, but inner membrane is arranged in a series of  folds called cristae.  

• Matrix: Semifluid substance in the center of the mitochondrion. • Inner provides a lot of surface area for reactions to occur.

• Contain 70S ribosomes.

• Used in cellular respiration.

• Can reproduce by growing and dividing to two.  

G. What are chloroplasts?

• Chloroplast: Structure and contains enzymes and chlorophyll required for  the light gathering phases of photosynthesis.

• Chlorophyll is contained in thylakoids, and stacks of thylakoids are  granum.

• Contain 70S ribosomes, DNA, and enzymes involved in protein synthesis. • Capable of multiplying on their own.

H. What are peroxisomes?

• Similar to lysosomes, but smaller.

• Contain one or more enzymes that can oxidize various substances. • Contains enzyme catalase, which decomposes H2O2.

I. What is a centrosome?

• Centrosome: Region near the nucleus, in which its involved in the  formation of the mitotic spindle.

• Region consists of 2 areas: the pericentriolar area and a pair of centrioles. • Pericentriolar material: Region of cytosol with dense network of small  protein fibers.

• Centrioles: In the pericentriolar material, in which it has a 9+0 array of  microtubules (9 clusters of 3, and zero in the center).

XIII. How did the evolution of eukaryotes begin?

• 2.5 billion years ago, eukaryotes evolved.  

• Lynn Margulis: Endosymbiotic theory.

• When bacterial cells lose their cell wall and ate a small bacterial cell. • Nucleus was developed when the plasma membrane folded around the  chromosome.

• The nucleoplasm ingested aerobic bacteria, in which there was a symbiotic  relationship in which the the nucleoplasm supplied nutrients and the bacteria  provided energy for the nucleoplasm.

Andrew Friedman

BIOL 305-001

Microbiology Chapter 4 Notes: Functional Anatomy of Prokaryotic and Eukaryotic  Cells 

• Chloroplasts could have descended from the nucleoplasm.

• Eukaryotic flagella and cilia descended from symbiotic relationships  between plasma membranes and motile spiral bacteria called spirochetes.  • The same antibiotics inhibiting proteins synthesis in ribosomes in bacteria  also inhibit synthesis on ribosomes in mitochondria and chloroplasts. • There is evidence of the endosymbiotic theory based on the structure of the  organelles.

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