Chapter 3 Cell Structure and Function
How is bacterial DNA different from eukaryotic DNA?
*Bacterial chromosome are in the cytoplasm whereas human chromosomes are enclosed by a nuclear envelope which separates the chromosomes from the cytoplasm. *Bacterial chromosome are haploid having a single set of unpaired chromosomes. Human chromosomes are diploid. *Bacteria contains small, circular extra chromosomes called plasmids
Describe the structure, chemistry, and functions of the bacterial plasma membrane.
*The plasma membrane encloses the cytoplasm and is a lipid bilayer with peripheral and integral proteins (the fluid mosaic model). *The cell wall surrounds the plasma membrane and protects the cell from changes in water pressure. *The bacterial cell wall consists of peptidoglycan, a polymer consisting of NAG and NAM and short chains of amino acids. *The plasma membrane is selectively permeable. *Plasma membranes contain enzymes for metabolic reactions, such as nutrient breakdown, energy production, and photosynthesis. *Plasma membranes can be destroyed by alcohols and polymyxins.
Describe the archaeal cell wall and cell membrane. What are hami and what is their function?
*cell wall: present in most made of peptidoglycan *Cytoplasmic membrane: Present in all, phospholipids made with ester linkages in bilayer *Hami: present in some, used for attachment
What is the main function of the bacterial cytoskeleton? How does this compare/contrast to eukaryotic cytoskeletons?
*function in cell division, cell shape, separation of DNA molecules, and movement through environment *membrane bound organelle: nucleus, semiliquid portion called nucleoplasma and contains chromatin, ribosomal subunits made in nucleus surrounded by nuclear envelope with nuclear pores
What are plasmids? Are they essential to the cell?
*small circular DNA molecules found in many prokaryotic cells *non-crucial genes *may provide an advantage to the cells and be a means of natural selection
Why are bacterial capsules medically important?
. Capsules contribute to bacterial virulence (the degree to which a pathogen causes disease Capsules protect pathogenic bacteria from phagocytosis by the cells of the host.
1. Be able to fully explain the origin of modern day ukaryotes from ancestral prokaryotes. 2. What is the name and definition of this theory?
1. 2. Endosymbiotic Theory: Eukaryotes formed from the union of small aerobic prokaryotes with larger anaerobic prokaryotes *mitochondria evolved 1st *Chloroplast evolved through later event
1. Describe the purpose of membranous organelles and the endomembrane system 2. Describe the function of lysosomes. Lysozyme is present in these organelles; what does this enzyme digest? 3. All cells in the human body have lysozyme, but what cells have a high number of these organelles?
1. Membranous organelles: Compartmentalizes cell so that enzymatic reactions stay restricted to specific cell sections Endomembrane system: acts as the transportation and product processing section of eukaryotic cell *Endoplasmic reticulum *Golgi body *Lysosomes and vesicles 2.Lysosomes are organelles that contain digestive enzymes. They digest excess or worn out organelles, food particles, and engulfed viruses or bacteria. Lysosomes are like the stomach of the cell. 3.White blood cells have a high number of lysosomes
Know the key events involved in the formation of eukaryotic organelles. Can you place the following events in the correct order? _____ Ancestral prokaryote increases in size _____ Chloroplasts evolve in plants and algae _____ Infolding of cell membrane _____ Mitochondria evolve in ancestral eukarotes _____ Nucleus forms _____ Photosynthetic bacterium engulfed _____ Respiring bacterium engulfed Be able to explain the evidence that supports this theory.
1. Nucleus forms 2. In folding of cell membrane 3. Ancestral prokaryote increases in size 4. Respiring bacterium engulfed 5. Photosynthetic bacterium engulfed 6. Mitochondria evolve in ancestral eukaryotes 7. Chloroplasts evolve in plants and algae
What is different about acid-fast bacteria, archaea, and mycoplasmas in regards to cell walls?
Acid-fast bacteria: like gram-positive, waxy lipid (mycolic acid) bound to peptidoglycan, Mycobacterium, nocardia Mycoplasmas: lack cell walls, sterols in plasma membrane Archaea: wall-less or walls of pseudomurein (lack NAM and D-amino acids)
Application question: Why are mycoplasmas resistant to antibiotics like penicillin that interfere with cell wall synthesis?
Any antibiotic interfering with cell wall synthesis would not have an effect because mycoplasmas do not have cell wall.
Describe the different types of bacterial flagellar arrangements.
Bacteria can be atrichous (no flagella) or have different flagellar arrangements. Monotrichous: A single flagellum, usually at one pole (A) Lophotrichous: Two or more flagella at one or both poles (B) Amphitrichpus: A single flagellum at both ends of the organism (C) Peritrichous: Flagella over the entire surface (D) Polar: only on the ends or poles of the cell
How do bacteria move?
Bacteria move in response to stimuli (taxis) with flagella.
Describe the structure and general function of bacterial inclusions. Which inclusions would store phosphates? What is the function of gas vacuoles?
Bacterial inclusions hold reserve deposits of nutrients, some are surrounded by polypeptide metachromatic granules store phosphate gas vesicles provide buoyancy for some aquatic cyanobacteria
What is the difference between a capsule and a slime layer?
Capsules and Slime layer are types of glyococalyx's. Capsules are glycocalyx's made up of organized, repeating units of organic chemicals that are firmly attached to the cells surface. Capsules can sometimes prevent bacteria from being recognized by there host. Capsules make bacteria pathogens. A slime layer is a loose, water-soluble glycocalyx that is attached to the the cells surface and is used in helping cells attach to other surfaces.
Understand what is meant by cell morphology (shape + arrangement) of bacteria. Be able to distinguish cell morphologies if given a picture or a description.
Cell morphology identifies the shape, size, and arrangement of cells. 3 common shapes: bacillus (rod) coccus (sphere) spiral type (vibrio). Arrangement(refers to whether or not cells remain attached after binary fission): Diplo (paired) Strepto (chains) Staphylo (Grape-like clusters)
Describe the composition and function of the cytoplasm.
Cytoplasm is the fluid component inside the plasma membrane. The cytoplasm is mostly water, with inorganic and organic molecules, DNA, ribosomes, and inclusions. Cytoplasm contains molecules such as enzymes which are responsible for breaking down waste and also aid in metabolic activity.
Under what conditions do endospores form? Why are endospores important for medical microbiology?
Endospore formation is usually triggered by a lack of nutrients, and usually occurs in gram-positive bacteria. Endospores are important from a clinical viewpoint and in the food industry because they are resistant to processes that normally kill vegetative cells . Such processes include heating, freezing, desiccation, use of chemicals, and radiation.
Describe the structure of endospores and the processes of sporulation and endospore germination.
Endospores: resting structures formed by some bacteria, they allow survival during adverse environmental conditions. They consist of dehydrated core surrounded by cortex (peptidoglycan layer) and spore coat. Sporulation: the process of endospore formation. Endospore germination: the return of an endospore to its vegetative state
Describe the structure of the bacterial glyococalyx.
Glyococalyx: Gelatinous, sticky substance that surrounds the outside of the cell. It can be composed of polysaccharides, polypeptides, or both. It is used to help bacteria attach to different surfaces, prevent phagocytosis, and prevent the microbe from dehydration.
Be able to differentiate between the composition and structures of the gram-positive and gram-negative cell wall.
Gram Positive: Stain purple Thick layer of peptidoglycan Teichoic Acids Gram Negative: Stain pink Thin layer peptidoglycan Outer bilayer membrane contains phospholipids, proteins, and LPS: Lipid A
Which cell wall type has some added protection against chemicals like antibiotics and disinfectants?Why?
Gram negative bacteria have a unique outer membrane that help certain drugs from penetrating the cell. It has an outer membrane that is composed of 2 layers, the inne layer is made up of phospholipids and protiens. the outer layer is made of LPS.
Be able to distinguish simple diffusion, facilitated diffusion, osmosis, and active transport.
In simple diffusion molecules from a high concentration to low concentration In facilitated diffusion, substances are transported by transporter proteins across membranes from areas of high to low concentration. Osmosis is the movement of water from areas of high to low concentration across a selectively permeable membrane until equilibrium is reached. In active transport, materials move from areas of low to high concentration by transporter proteins, and the cell must expend energy.
Describe the structure and function of bacterial flagella.
Long whip like, longer & thicker than fimbrae and pili, there main function is to help bacteria move in response to stimuli (taxis). Made up of filament, hook, and basal body. Filament: outer part of flagella, made up of flagellin. Hook: attaches to the filament Basal body: made up of rods and pairs of rings, they anchor the flagella to the cell wall. Bacterial flagella rotate to "run" or "tumble" Flagella can vary in H antigen among different strains (serovars) of bacterias.
Describe the functions of mitochondria and chloroplasts.
Mitochondria: convert electron energy from cellular respiration into ATP Chloroplasts: *Site of photosynthesis *Convert solar energy to ATP that cell uses to make carbs *Only plants, algae, and some protozoa have them *both organelles have a double membrane and are highly folded
Describe the structure and function of the bacterial cell wall.
Most prokaryotes have a chemically complex external covering called a cell wall. Major structural component: *peptidoglycan Function: *main function is prevent bursting from osmotic pressure (lysis) *maintain the cell shape *helps in attachment *helps some cells resist antimicrobial drugs *used to differentiate gram + and gram - bacteria
Compare and contrast the following prokaryotic and eukaryotic structures: Glycocalyxes Cell walls Plasma membranes Flagella (do prokaryotes have cilia?) Cytoskeleton Ribosomes Genome (DNA)
PROKARYOTES Unicellular (1 entity), lack organelles, and contain a cell wall. The prokaryotic cell contains no membrane-bound organelles which are independent of the plasma membrane. The prokaryotic cell has no nucleus Smaller than a Eukaryotic Cell Prokaryotic ribosomes are composed of only three kinds of rRNA and about fifty kinds of protein. Prokaryotic cells have only one organelle: the ribosomes. EUKARYOTES: Eukaryotic cells have a true nucleus, bound by a double membrane. Eukaryotic DNA is linear Eukaryotic cells have membrane-bound organelles. Larger than prokaryotic cells A eukaryotic ribosome is composed of five kinds of rRNA and about eighty kinds of proteins. Eukaryotic has a nucleus, the control center of the cell. This is where the chromosomes (DNA) are stored in a double phospholipid membranes. The cytoplasm of eukaryotic cells is filled with a large, complex collection of organelles, many of them enclosed in their own membranes Eukaryotic cells are multicellular (also called animal cells), contain organelles, and lack a cell wall.
Describe the structure and function of pili.
Pili is a special type of fimbria that is longer than regular fimbriae and shorter than flagellum. Pili's main role is gene transfer (conjugation) and attachment.
Describe the structure and function of bacterial ribosomes. What type of ribosomes do eukaryotes have?
Prokaryote Ribosome: *site of protein synthesis *composed of 2 subunits,( large and small) made up of RNA and protein *smaller 70s *antimicrobial target Eukaryotic Ribosomes: *Larger than pro. 80s *membrane bound and attached to ER *make protein for export *surrounded by nuclear envelope containing nuclear pore
Prokaryotes use cellular respiration and photosynthesis, but they don't have mitochondria or chloroplasts. Where are the ETCs of these processes embedded in a prokaryotic cell? (hint: see objective #13)
Prokaryotes also produce ATP but the enzymes required for its production are attached to the cellular membrane that surrounds the cell. The cellular membrane can adjust and fold itself to promote ATP production through these enzymes when necessary. Prokaryotes can be either autotrophic or heterotrophic. Autotrophs can synthesize their own food for energy production whereas heterotrophs must consume food to use for energy production.
Compare and contrast prokaryotes to eukaryotes. What are the main features that distinguishes prokaryotes from eukaryotes?
Prokaryotes: No nucleus No membrane-bound organelles Smaller than eukaryotes Chemically complex cell walls Divide by binary fission Make up domains Bacteria & Archaea Peptidoglycan cell walls if bacteria Eukaryotes: Nucleus Membrane bound organelles Larger than prokaryotes May or may not have cell walls (chemically simple if present) Divide by mitosis (asexual) or meiosis (sexual) Make up domain Eukarya and include algae, protozoa, fungi, animals, and plants Polysaccharide cell walls Prokaryotes lack a nucleus. Eukaryotes have a nucleus
Differentiate the structure/movement of prokaryotic flagella from eukaryotic cilia and flagella.
Prokaryotic Flagella: Flagella are the complex, hairlike structure that extend through the cell surface. Flagella are composed of protein like flagellin, embedded in the cell envelope. They are responsible for motility and rotate like a screw to "run" or "tumble" Eukaryotic Flagella/Cillia: Cilia are short, slender, hair-like appendages extending from the surface of the cell. These are present in almost all eukaryotic cells. They play a significant role the cell and overall body development. Cilia are broadly divided into two types - Motile and Non-motile. Motile or moving cilia are mainly present in lungs, middle ear, and respiratory tract. These kind beat rhythmically. Their work is to keep the airways clear of mucus and dust, due to which it is easy to breathe freely and without any irritation. They are also helpful in the movement of the sperm.
Compare and contrast the structure/functions of bacterial and eukaryotic plasma membranes.
Same: phospholipid bilayer w/proteins Diff: eukaryotes contain carbs attached to proteins and sterols (steroid alcohols like cholesterol) not found in prokaryotes (except mycoplasma bacteria); they also move materials across plasma membrane by passive, active, and endocytosis processes (phagocytosis & pinocytosis)
Compare and contrast bacteria and archaea. Are archaea more closely related to bacteria or to eukaryotes? Explain.
Similarities: archaea and eubacteria are prokaryotes — single-celled organisms that do not have a nucleus or organelles. Glycocalyx: polypeptide or polysaccharide Differences: ARCHAEA: *Flagella: present in some, grow at base, rotate counterclockwise and clockwise *pili: none discovered *Fimbriae: proteinaceous, used for attachment & forming biofilms *cell wall: present in most made of polysaccharides (not peptidoglycan) or proteins *Cytoplasmic membrane: Present in all,membrane lipids made with either linkages, some have single lipid layer *Cytoplasma: cytosol contains circular DNA molecule & 70's ribosomes EUKARYOTES: *Flagella: present in some, grow at tip, rotate counterclockwise to run, rotate independently counter clockwise to cause tumbles *Fimbriae: proteinaceous, used for attachment, gliding motility & forming biofilms *Pili: present in some, proteinaceous, used in bacterial exchange of DNA *cell wall: present in most made of peptidoglycan *Cytoplasmic membrane: Present in all, phospholipids made with ester linkages in bilayer *Cytoplasma: cytosol contains circular DNA molecule & 70's ribosomes w/bacterial proteins *Hami: none Archaea are more closely related to eukaryotes, there ribosomal DNA is similar and they use a genetic code similar to eukaryotes
Describe the structure and function of axial filaments (endoflagella) and what bacterial group possesses them. How does this help these bacteria move through their environment? Are any of these bacteria pathogens?
Spirochetes are a bacteria that have a type of flagella called endoflagella. These are bundled together to form an axial filament. The axial filaments wrap around the cell body, connect both ends of the cell, and embed in the outer membrane. The attachment of the endoflagella to the cell causes spirochetes to rotate or cork screw as they move through the environment, allowing pathogens to invade human tissues.
Describe the structure and function of fimbriae.
Sticky bristle like projections that help bacteria attach to tissues and surfaces. Fimbriae is important in biofilms. Fimbriae have no role in bacterial motility or DNA transfer.
Describe the structure and function of the bacterial chromosome and where it is located in the cell.
The DNA of most bacteria is contained in a single circular molecule, called the bacterial chromosome Forms an irregularly shaped structure called the nucleoid, located in the cytoplasma
Describe the staining process that has to be used to stain endospores.
The Schaeffer-Fulton method (the most commonly used endospore-staining technique) uses heat to push the primary stain (malachite green) into the endospore. *Washing with water decolorizes the cell, but the endospore retains the green stain *cell is then counterstained pink with safranin. The resulting image reveals the shape and location of endospores, if they are present. *The green endospores will appear either within the pink vegetative cells or as separate from the pink cells altogether. *If no endospores are present, then only the pink vegetative cells will be visible.
What benefit does the cell wall provide in a hypotonic environment?
The cell wall will stop the flow of water making it rigid and prevent the cell from bursting (lysis).
Why are antibacterial drugs that target bacterial cell wall synthesis useful?
Without the cell wall, the bacteria will be susceptible to destruction by chemicals outside the plasma membrane (which is just inside the cell wall of bacteria), and it will not be able to survive. Animal cells do not contain cell walls, so these drugs will only harm the bacteria and leave the cells in the body unharmed
What are the four structures common to ALL cells (both prokaryotes and eukaryotes)? Do viruses possess any of these structures/processes?
cell membrane cytoplasma Ribosomes DNA Viruses contain DNA & can reproduce within a host.
Application question: The antibiotics clindamycin, erythromycin, and tetracycline all bind with the bacterial ribosome. Why would this kill these cells by stopping protein synthesis, but not affect the eukaryotic host cell (your cells)?
does it have to do with not having a cell wall?
What are the four processes common to living organisms?Do viruses possess any of these structures/processes?
growth reproduction responsiveness metabolism Viruses contain DNA & can reproduce within a host.
What happens to a cell in a hypertonic environment?
water will diffuse "out" from the cell and the cell will dehydrate and shrink and cellular metabolism will cease.
What happens to a cell in a hypotonic environment?
water will diffuse into the cell and the cell will begin to swell. This can of course lead to an explosion of sorts.
