microbiology exam 1

microbe types: bacteria

• prokaryotes

• single-celled (unicellular)

  • DNA present but not enclosed in nucleus

• peptidoglycan cell walls

  • some have walls, some don’t (ex: mycoplasma)

• divide by binary fission

• derive nutrition from organic or inorganic chemicals or photosynthesis

• may “swim” by using moving appendages called flagella

• can be beneficial, harmful (pathogenic), or harmless

• ex: E. coli, Staphylococcus

microbe types: archaea

• prokaryotes

• unicellular

• cell walls lack peptidoglycan or may lack cell wall entirely

• have unique membrane and cell-wall characteristics

• often live in extreme environments, but also in the human gut

  • ex: hot springs, very salty environments, human intestines, and animal intestines

• include methanogens, extreme halophiles, and extreme thermophiles

• not known to cause disease in humans

microbe types: fungi

• eukaryotes (distinct nucleus consisting of DNA surrounded by a nuclear membrane

• have cell walls made of chitin (tough, natural sugar polymer)

• absorb organic chemicals for energy

  • secrete enzymes that break down organic matter, then absorb nutrients

microbe types: yeast (fungi)

• unicellular

• reproduce by budding; asexual

  • small bud develops from parent cell and grows

    • daughter cell may:

      • separate from the parent

      • remain attached temporarily

• ex: Candida (genus)

  • can cause infections, particularly those with weakened immune system

microbe types: mold (fungi)

• multicellular

• consist of masses of mycelia, which are composed of filaments called hyphae

• sacs of mold spores

  • become air borne

  • spread to another location

  • develop into another mold colony

microbe types: protozoa

• eukaryotes

• unicellular with complex cell structures

• lack cell walls

• live in soil and water

• absorb or ingest organic chemicals

• most are motile via pseudopods, cilia, or flagella

• reproduce sexually or asexually

• most are free-living, some are photosynthetic

• some are parasitic (derive nutrients from a living host)

• ex: cyclospora

  • recent food borne outbreak

  • can contaminate produce and cause human disease

microbe types: algae

• eukaryotes

• can be unicellular or multicellular

• cellulose cell walls

• widely distributed in freshwater and saltwater

• use photosynthesis for energy → produce O₂ and carbohydrates

• important source of food for other organisms

• sexual and asexual reproduction possible

• not medically significant: not pathogenic to humans, but some can produce toxins

microbe types: viruses

• acellular infectious agents

• no cell structure; not cells

• extremely small

• consist of DNA or RNA core, not both

• core is surrounded by a protein coat called a capsid

  • coat may be enclosed in a lipid envelope

• no ribosomes

• can only replicate inside in a living host cell

  • inert outside living hosts

  • lack their own machinery for metabolism or reproduction

  • obligate intracellular parasites

microbe types: helminths

• parasitic worms

• eukaryotes

• multicellular animals

• not strictly microorganisms

• no cell walls

• flatworms = platyhelminths; roundworms = nematodes

  • some microscopic stages in their life cycles

• diagnosed by fecal matter

  • look for eggs and other microscopic structures associated with parasite

Robert Hooke

• 1665 - reported that life’s smallest structural units were composed of little boxes, or “cells”

• observed cork slices with a crude microscope

• marker the beginning of Cell Theory (all living things are composed of cells)

Antonie van Leeuwenhoek

• 1623-1673 - observed the first microbes

• Father of Microscope

• “animalcules” (bacteria, protozoa) viewed through magnifying lenses/simple microscopes

• observed microbes in rainwater, river water, other water samples, and fecal matter

Louis Pasteur

• 1861 - disproved Spontaneous Generation with S-shaped (swan-neck) flask experiment

• fermentation: showed that yeast and bacteria convert sugars into alcohol and acids; can occur in absence of oxygen

• pasteurization: developed gentle heat treatment to kill “spoilage” microbes in beverages

  • today, it is used for milk, cheese, eggs, beer, wine, and cider to keep food safe

• vaccine development: created the first artificial vaccines for rabies and anthrax

• Germ Theory: microorganisms causes diseases; certain infectious diseases are caused by specific microbes

Joseph Lister

• 1860s - developed the first aseptic technique

  • using phenol (carbolic acid) as an antiseptic to prevent surgical wound infections

  • washed his surgical tools in phenol to disinfect them = less death following surgery

• helped demonstrate that microorganisms cause surgical wound infections

Robert Koch

• 1876 - discovered that a bacterium Bacillus anthracis causes anthrax and provided the experimental steps, Koch’s postulates, to demonstrate that a specific microbe causes a specific disease

• developed methods for obtaining pure cultures

• modern microbiology recognizes exceptions; some microorganism cannot be easily cultured, some diseases have multiple causes, and ethical limitations prevent certain experiments

Edward Jenner

• 1979 - tried to protect patients from contracting Smallpox decades before Germ Theory

• observation: milkmaids, who were routinely exposed to Cowpox, a similar but much milder disease did not contract the deadly Smallpox

• to test if the Cowpox disease was offering protection against Smallpox, Jenner inoculated an 8 year old volunteer with cowpox pus from a milkmaid’s hand

• vaccination is derived from the Latin word vacca, meaning cow

• the protection is called immunity

Paul Ehrlich

• developed an early synthetic chemotherapeutic agent

• introduced a “magic bullet,” an arsenic-containing chemical called salvarsan, to treat syphilis with some success

• “magic bullet” - selectively targets a pathogen while causing less damage to the host

Alexander Fleming

• 1928 - observed that Penicillium fungus made an active ingredient (he named it penicillin) that inhibited the growth of Staphylococcus bacteria on a plate

• bacterial growth was inhibited → colonies were smaller or absent

• conclusion: mold was producing a substance that inhibited bacterial growth → Penicillin

• Penicillin has been used clinically as an antibiotic since the 1940s

Wendell Stanley

• first to isolate and characterize a virus

• 1935 - purified and crystallized the tobacco mosaic virus (TMV)

• showed that the TMV is composed of protein and RNA

• his work allowed scientists to study viruses chemically and structurally

Selman Waksman

• discovered streptomycin, the first effective antibiotic against tuberculosis

• studied sail microbes

How was spontaneous generation disproved?

• spontaneous generation - the hypothesis that life arises from nonliving matter; a “vital force” is necessary for life

  • ex: toads, snakes and mice could be born from nothing more than moist soil

• biogenesis - the hypothesis that cells are present in all living creatures and living cells arise only from preexisting living cells

How did Francesco Redi disprove spontaneous generation?

• put meat into containers

• maggots appeared when flies could reach the meat

• demonstrated that maggots came from flies, not spontaneously from meat

How did John Needham disprove spontaneous generation?

• heated nutrient broth

• microorganisms eventually appeared

How did Lazzaro Spallanzani disprove spontaneous generation?

• repeated Needham’s experiment

• boiled broth longer and sealed containers

• no microorganisms appeared

• suggested microorganisms came from the air

How did Louis Pasteur disprove spontaneous generation?

• air could enter, but microorganisms were trapped in the curved neck

• result:

  • no microbial growth when contamination was prevented

  • microbial growth occurred when microorganisms could enter

• conclusion: microbes did not spontaneously appear; came from other microbes/environmental contamination

  • supported biogenesis

importance of Koch’s Postulates

• series of criteria used to establish that a specific microorganism causes a specific disease

• steps:

1. the suspected pathogen is found in every case of the disease

2. the pathogen is isolated in pure culture

3. the isolated pathogen causes the same disease in a healthy, susceptible host

4. the same pathogen is re-isolated from the experimentally infected host

• provided experimental evidence connecting: specific microbe → specific disease

• do not work perfectly for every disease because:

  • some pathogens cannot be grown on artifical media

  • some disease can have multiple causes

  • some pathogens only infect humans

  • some pathogens cause multiple diseases

define human microbiome and human microbiota

• human microbiota - microorganisms that normally live in and on the human body

  • ex: bacteria on the skin, bacteria in the intestines, and microorganisms in the mouth

  • microorganisms that establish permanent colonies in or on the body without normally producing disease

• human microbiome - the broader microbial community associated with the human body, including the microorganisms and their genetic material and interactions

examples of how our normal microbiota benefit human health and daily body functions

• aid in the digestion and absorption of nutrients

• produce growth factors such as vitamins B and K

• can prevent growth of pathogenic microbes

• may help train the immune system to discriminate threats during the childhood

• influence brain development, mood, and behavior (via the gut-brain axis)

Beyond the human body, how do microbes impact out lives and society?

• biotechnology: the use of microbes for practical applications, such as producing foods and chemicals

  • food ex: vinegar, cheese, yogurt, alcoholic beverages

  • chemical ex: organic acids, ethanol, acetone, amino acids, vitamins

• bioremediation: use microbes to clean up pollutants

  • ex: oil spills, toxic waste, chemical spills, polluted water, contaminated soil

  • some bacteria use pollutants as energy sources or produce enzymes that break toxic substances down

two examples of biotechnology using recombinant DNA and two that do not

• recombinant DNA: DNA that has been artificially manipulated to combine genes from two different sources

• two ex. of using recombinant DNA:

  • human insulin

    • human insulin gene can be inserted into bacteria

    • the bacteria produce human insulin

  • hepatitis B vaccine

    • yeast can carry a gene for part of the hepatitis B virus

    • the yeast produces viral coat protein used in the vaccine

• two ex. of not using recombinant DNA:

  • traditional cheese production

    • microorganisms naturally carry out fermentation

    • no foreign gene needs to be inserted

  • traditional alcoholic fermentation

    • yeast naturally converts sugars into alcohol

    • no recombinant DNA is required

define taxonomy and know the taxonomic ranks

• taxonomy: the science of classifying and naming organisms

  • organisms are assigned to categories (taxa) to reflect evolutionary relationships and show the degree of similarity among organisms

• taxonomic ranks:

  • Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species

define binomial nomenclature

• developed by Carolus Linnaeus in 1735

• each organism has two names: the genus and the specific epithet (species)

  • italicized when typed or underline when written

    • the genus is capitalized; the specific epithet is lowercase

  • are “Latinized” and used worldwide

  • after the first use, scientific names may be abbreviated with the initial of the genus followed by the full name of specific epithet

what is the Three-Domain System based on? do viruses belong to a domain?

• based on similarity in sequences of rRNA genes

  • all organisms evolved from cells that formed over 3 billion years ago

  • the DNA passed on from ancestors is described as conserved

  • rRNA is a highly conserved molecule and is present in all cellular life

    • changes relatively slowly over evolutionary time → can compare rRNA sequences between organisms to determine how closely related they are

• viruses do not belong to a domain

  • three domains = bacteria + archaea + eukarya

Five-Kingdom System

1. Monera → prokaryotes

2. Protista

3. Fungi

4. Plantae

5. Animalia

• primarily based on observable characteristics (ex: morphology and nutrition)

• less commonly used

  • molecular evidence showed that prokaryotes are not evolutionary group

  • two distinct prokaryotic domains (bacteria + archaea), therefore, Three-Domain System better reflects evolutionary relationships

• this system placed prokaryotes in Monera, but later molecular biology showed that there are two distinct types of prokaryotes

aside from structural features, what are the fundamental differences between prokaryotes and eukaryotes?

Prokaryotes

• DNA: usually one circular chromosome

• ribosomes: 70S

• smaller cell size

• cell division: binary fission

• ex: bacteria archaea

• DNA location: nucleoid region

Eukaryotes

• DNA: organized into multiple chromosomes

• associated with proteins called histones

• 80S in cytoplasm

• larger cell size

• cell division: mitosis/meiosis

• ex: fungi, protozoa, algae, plants, animals

• DNA location: nucleus

describe the distinction between species and strains

• species - a population of cells with a high degree of genomic similarity

  • can contain multiple strains with different characteristics

• strains - a subtype of genetic variant within a single bacterial species

  • identifying strain can be important when:

    • investigating an outbreak

    • determining the source of an infection

    • comparing microorganisms from different patients

    • determining whether organisms are genetically related

  • strains of the same species can differ physiologically in significant ways without being considered a different species

chemical reactions

• a process in which one or more substances (reactants) are transformed into one or more different substances (products) through the breaking and forming of chemical bonds

• important for metabolism, including obtaining energy and building cellular materials

ionic bonds

• an attraction between ions of opposite charge that holds them together to form a stable molecule

• weaker ionic bonds are important in biochemical reactions such as antigen-antibody reactions

• ex: Na⁺ + Cl^- → NaCl

• one atom transfers an electron to another atom

covalent bonds

• a bond formed by two atoms that share one or more pairs of electrons

• stronger and more common in organisms than ionic bonds

• found in carbohydrates, lipids, proteins, and nucleic acids

• ex: CH₄ → carbon shares electrons with hydrogen atoms

hydrogen bonds

• relatively weak bond in which a hydrogen atom (positive) that is covalently bonded to one oxygen or nitrogen atom (electronegative) is attracted to another oxygen or nitrogen atom

• do not bind atoms into molecules, but serve as bridges between different molecules or different portions of the same molecule, for example, within proteins and nucleic acids, to stabilize the structures

• ex: H₂O → water molecules form hydrogen bonds with each other

What are the special properties of H₂O? What characteristic of water makes it a good solvent?

• excellent temperature buffer; high specific heat - resists rapid temperature changes

• excellent solvent

  • polar and ionic substances undergo dissociation n water, forming solutes in solutions

  • water’s polarity allows it to surround and separate ions and other polar molecules

• serves as a reactant or product in many reactions

  • participates in chemical reactions - important in many cellular reactions

  • provides a medium for biochemical reactions

• creates surface tension (to behave as it if has a thin elastic membrane on its surface)

  • water molecules attract each other through hydrogen bonds

• helps transport substances through organisms

functions of carbohydrates

• cellular energy sources

• serve as components of cell structures

  • ex: sugar in DNA and RNA, sugars in cell walls

  • some bacterial toxins (endotoxins) have a complex carbohydrate component (“polysaccharide in lipopolysaccharide)

• three main groups:

  • monosaccharides (ex: glucose, fructose)

  • disaccharides (ex: sucrose, lactose)

  • polysaccharides (ex: glycogen, starch)

functions of lipids

• dissolve in nonpolar solvents

• primary structural component of cell membranes

• energy storage

• some bacterial toxins have a lipid component

• major types:

  • simple lipids (ex: fats, oils, triglycerides)

    • contain glycerol and fatty acids; hydrophobic

  • phospholipids

    • glycerol, two fatty acids, and a phosphate group; amphipathic

  • steroids and sterols

    • cholesterol: part of plasma membranes that maintains membrane fluidity in animal cells

    • ergosterol: found in the plasma membranes of fungi

functions of proteins

• structural support, metabolism, transport, defense, signaling, regulating, and motion

• enzymes that speed up biochemical reactions

• transport proteins that move chemicals across membranes

• receptor proteins embedded in the cell membrane bind to specific external or internal signals

• flagella that aid in movement

• antibodies (immunoglobulins) that fight microbial infections

• some bacterial toxins (endotoxins) → produced inside then secreted out, can be both Gram (+) or Gram (-)

• structural components

  • viral capsids - proteins that surround/protect the viral genetic material

functions of nucleic acids

• carry genetic information

• include DNA and RNA

  • RNA - helps with processes involved in protein synthesis; mRNA, tRNA, rRNA (used in ribosomes, bacterial identification, and 3-domain classification system)

• consist of nucleotides (monomer unit)

  • five-carbon (pentose) sugar

  • phosphate group

  • nitrogen-containing base (adenine, guanine, cytosine, thymine [DNA], and uracil [RNA])

Why is ATP important?

• principal energy carrying molecule of all cells

  • stores energy released by some chemical reactions in high-energy bonds

  • provides energy by hydrolysis for reactions that require energy

• When ATP is hydrolyzed/broken down (ADP + phosphate + energy), released energy can be used for cellular processes

bacterial size

• recorded in micrometers

• most bacteria range from 0.2 to 2.0 micrometers in diameter and from 2 to 8 micrometers in length

• viruses range from 20 to 1000 nanometers in length, with most fall into a size range of 30-300 nanometers

How is total magnification calculated? Define the resolving power of a light microscope. What are the best magnification and resolution which can be achieved by light microscopes? Why do you add oil to the slide when using 100x objective?

• total magnification = objective lens * ocular lens

• resolving power/resolution - the ability of the lenses to distinguish two points or the ability to distinguish fine detail and structure

• best magnification: approx. 1,000-1,500x; best resolution: approx. 200 nm (0.2 micrometers)

  • increasing magnification beyond the useful range does not necessarily provide more detail because the microscope’s resolution limits how much detail can be seen

• immersion oil is used to keep light from refracting

  • glass → oil → objective: reduces the amount of light that bends away

How does immunofluorescence help identify a specific pathogen in a patient sample?

• fluorescent-antibody technique

• antibodies specific for a type of microbial pathogen are prepared and tagged with a fluorochrome

• these “fluorescent antibodies” are applied to a microscope slide bearing a specimen that may contain the pathogenic microbe

• if the pathogenic microbe is present, the fluorescent antibodies will adhere, causing the microbe to fluoresce when viewed with fluorescence microscopy

• provides a means of rapid and specific detection of pathogens in patient specimens

Depending on the type of electron microscope, it can magnify from 1,000X to 10,000,000X with nanometer or even sub-nanometer resolution. Electron microscopes differ from light microscopes since they use a beam of electrons instead of a beam of light. They also focus the electron beam with electromagnets whereas light beams are focused with glass lenses. Explain what kinds of cellular structures (internal vs. surface) each EM is best used to visualize.

• Transmission EM - a beam of electrons passes through ultrathin sections of a specimen, then through an electromagnetic lens, then focused by a projector lens

• Scanning EM - an electron gun produces a beam of electrons that scans the surface of an entire specimen

  • secondary electrons emitted from the specimen are transmitted to an electron collector, amplified, used to produce a 3D image on a viewing screen

What is the value of Gram Stain in medical microbiology?

• can be done to detect bacteria in clinical specimens

• often the first step in identifying an unknown bacterium

• can provide valuable information for treatment

• tells us:

  • bacterial shape and arrangement/morphology

  • Gram (+) and Gram (-)

  • relative amount of bacteria present

  • sample contains multiple types of bacteria

Why do bacterial cells need to be stained for best viewing even when they are magnified under a light microscope? Define acidic and basic dyes. Why does a simple stain commonly use a basic dye?

• helps increase contrast and visibility

• see bacterial size, shape, arrangement, and structures

• help with classification and identification

• acidic dyes: resistant to acid alcohol; negatively charged chromogen, so dye is repelled by bacteria and tends to stain the background instead

  • ex: Mycobacterium (causes TB), Nocardia

• basic dyes: positively charge chromogen, so dye adheres to the negative charge of the cell wall and nucleic acids

• simple stain is commonly uses a basic dye because bacterial cell are negatively charged, so they attract positively charged basic dye

functions of simple stain

to observe bacterial size, morphology, and arrangement

functions of Gram stain

• differential stain

• classifies bacteria into Gram-positive or Gram-negative

• are most consistent when used on young, actively growing bacteria

• differentiate bacteria based on cell wall characteristics

functions of acid-fast stain

• resistant to acid alcohol

• identify acid-fast bacteria

  • have a waxy cell wall containing mycolic acid, which makes them resistant to ordinary staining/decolorization

• most bacteria lose the primary stain, become colorless, and take up the counterstain; red/pink

functions of capsule stain

• detect capsules

• capsule/clear halo around the cell

• capsule contribute to protection, attachment, virulence, and avoidance of phagocytosis

functions of endospore stain

• detect endospores

• endospores in bacteria such as Bacillus and Clostridium

• endospores are dormant survival structures, not reproductive structures

functions of flagella stain

• detect flagella because they are too thin to be easily seen with an ordinary light microscope

What are the common bacterial shapes (morphology) and cellular arrangements of bacteria?

• coccus - spherical/round

• bacillus - rod-shaped

• coccobacillus - very short rods

• spiral - curved/spiral

  • vibrio - curved/comma-shaped rod

  • spirillum - rigid spiral-shaped cell

  • flexible, corkscrew-shaped cell

biofilms

• community of bacteria living together within a protective extracellular material

• bacteria can:

  • attach to surfaces

  • produce extracellular substances

  • communicate with each other

  • coordinate gene expression

  • share nutrients/resources

  • produce substances together that individual cells may not produce alone

• can be very resistant to antibiotics and disinfectants

How do bacterial capsules protect bacteria?

• capsule - neatly organized and firmly attached to the cell wall

• contributes to virulence

  • prevent phagocytosis → can make it hard for immune cells to engulf

  • contribute to adherence to surfaces → helps bacteria attach to host tissues and surfaces

• retain water and protects cells from desiccation (removal of moisture)

• can serve as a reserve of nutrition

• contribute to biofilm formation

• ex: Streptococcus pneumoniae

What role does a slime layer play in bacterial survival?

• slime layer - unorganized and loosely attached

• contributes to virulence

  • allows bacteria to adhere to various surfaces

  • extracellular polymeric substance (EPS) is critical for the formation of biofilms

    • provide significant protection to the bacteria within them

    • ex: Streptococcus mutans

• retain water and protects cells from desiccation

• can serve as a reserve of nutrition

What is bacterial taxis? Flagellar proteins such as flagellin are classified as which type of antigen?

• bacterial taxis - allows bacteria to move toward or away from stimuli

  • ex: chemotaxis → movement in response to chemicals; phototaxis → movement in response to light

• Flagella proteins are the H antigens

The body of a spirochete rotates like a corkscrew. What structure does the cell use?

• axial filaments/endoflagella

• located inside the periplasmic space

• anchored at one of a cell, beneath the outer sheath

Describe the major functions of fimbriae and the two types of pili.

• fimbriae

  • hairlike short, fine, and numerous appendages

  • allow for attachment

    • involved in the formation of biofilms

    • enable some bacteria to adhere to body surfaces

• pili

  • one or two projections, longer than fimbriae

  • common pili

    • involved in motility (gliding and twitching)

    • help with attachment

  • sex pili

    • used for conjugation (DNA transfer from one bacterium to another)

    • allows bacteria to make direct contact

    • can facilitate

Gram-positive

• a thick peptidoglycan (many sheets)

• contains teichoic acids

  • stabilize peptidoglycan

  • lipoteichoic acid links cell wall to the plasma membrane

  • carry a negative charge, regulate movement of cations

  • provide antigenic specificity

• alcohol dehydrates peptidoglycan

• CV - I complex do not leave during decolorization step

• purple

Gram-negative

• has an outer membrane (difference between positive and negative)

  • made of LPS, lipoproteins, and phospholipids

  • porins (proteins) form channels through membrane

    • allow the passage of small molecules and ions

• has a thin peptidoglycan layer

• has a periplasmic space

• Gram-negative pathogens are harder to treat partly due to their complex cell wall structure

• alcohol dissolves outer membrane and leaves holes in peptidoglycan

• CV - I washes out; cells are colorless

• Safranin added to stain cells

• pink/red

The peptidoglycan layer is a major component of the cell wall. It’s a polymer composed of N-acetylglucosamine (NAG), N-acetylmuramic acid (NAM) and a tetrapeptide side chain. Gram-positive organisms have a very thick peptidoglycan layer whereas Gram-negative organisms have a much thinner layer. What kinds of cross-links hold the adjacent strands together?

• polymer of a repeating disaccharide in rows:

  • NAG

  • NAM

  • short peptide chains

• adjacent peptidoglycan strands are held together by peptide cross-links between the tetrapeptide side chains

  • provides the bacterial cell wall with strength and rigidity

Gram-negative: outer membrane

• contains LPS

  • O polysaccharide portion functions as antigen (ex: E. coli O157:H7)

  • lipid A is a toxic component (endotoxin) embedded in the top layer

    • when Lipid A is released, it causes vasodilation, hypotension, septic shock, and can lead to death

• protects from phagocytosis and action of complement proteins (both are part of host defenses), and certain antibiotics and chemicals

Gram-negative: periplasmic space

• contains periplasm between the outer membrane and the plasma membrane

• contains many degradative enzymes and transport proteins

• where many metabolic processes take place

An acid-fast stain is a differential stain technique. It is used to stain bacteria in the genus Mycobacterium due to what component that surrounds its peptidoglycan layer?

• Mycobacterium has a cell wall containing a large amount of mycolic acid surrounding its peptidoglycan layer

• mycolic acid is a waxy lipid that makes the cell wall difficult to penetrate to ordinary staining/decolorization

Do bacteria in the genus Mycoplasma have cell walls? What component does it have in its plasma membrane?

• lack cell walls

  • no peptidoglycan

  • cell-wall-targeting antibiotics are ineffective against it

    • targeting peptidoglycan synthesis will not work against Mycoplasma

• sterols in plasma membrane may protect cell from lysis

Briefly describe the structure of the cell membrane.

• phospholipid bilayer that encloses the cytoplasm

  • hydrophilic head - faces water

  • hydrophobic tails - faces inward

• membrane proteins: peripheral proteins and integral proteins

  • transport

  • receptors

  • enzymatic activity

  • enzymatic production

• selectively permeable

• Fluid Mosaic model

  • proteins move freely for various functions

  • phospholipids rotate and move laterally

functions of plasma membrane

• selective permeability allows the passage of some molecules, but not others

• the site of the ETC and ATP synthase

  • contains various components that can include different types of enzymes, pigments, and other molecules for cellular respiration and ATP production

• performs photosynthesis in photosynthetic bacteria

What would happen to a bacterial cell placed in a hypotonic solution? In a hypertonic solution?

• hypotonic solution - solute concentration is lower outside than inside the cell; water moves into cell

• hypertonic solution - solute concentration is higher outside of cell than inside; water moves out of cell

  • can cause plasmolysis (cell membrane pulls away from the cell wall)

simple diffusion

• passive transport

• movement of a solute from an area of high concentration to an area of low concentration

• continue until molecules reach equilibrium

• ATP and protein not require

facilitated diffusion

• integral membrane proteins, known as transporters, serve as specific or nonspecific channels or carriers

• transport ions and larger molecules across a membrane down the concentration gradient

• no ATP required

osmosis

• the movement of water across a selectively permeable membrane from an area of higher water concentration to an area of lower water concentration

  • through lipid bilayer by simple diffusion

  • through aquaporins (water channels)

active transport

• requires a transporter protein and energy (ATP); goes against gradient

  • allow a cell to accumulate needed material

Why does the cell need to use ATP to move material across the cell membrane during active transport?

active transport moves substances against their concentration gradient which requires energy

What are the characteristics of bacterial chromosome and plasmid?

• bacterial chromosome - typically circular thread of double-stranded DNA that contains the cell’s genetic information

  • supercoiled and highly structured form

  • not enclosed within a nuclear envelope (membrane)

  • no associated histones

• plasmids - small circular DNA that separate from the chromosme

  • not located in the nucleoid

  • carry genes that may encode pili production, antibiotic resistance, production of toxins; noncrucial for survival

  • replicate independently of the chromosomal DNA

  • may be transferred to other bacteria

What advantage does an endospore provide to a bacterial cell that can produce one? Name 2 genera of bacteria that can make endospores and can also cause human disease.

• produced when environmental conditions are unfavorable, e.g., when nutrients are depleted

• resistant to desiccation, heat, chemicals, and radiation

  • survive in a dormant state for a long time

• Bacillus and Clostridium

Name one difference and one similarity between eukaryotic DNA, ribosomes, plasma membrane and flagella compared to those structures in a bacterial cell.

• DNA:

  • similarity: both store genetic information in DNA

  • difference: bacterial DNA is usually circular; eukaryotic nuclear DNA is linear

• ribosomes:

  • similarity: both make proteins

  • difference: bacteria have 70S ribosomes; eukaryotic cytoplasm has 80S ribosomes

• plasma membranes:

  • similarity: both have a phospholipid bilayer with proteins

  • difference: eukaryotic cells have more complex membrane systems/organelles; bacterial plasma membrane is also a major site of energy generation

• flagella:

  • similarity: both can use flagella for movement

  • difference: bacterial flagella are made mainly of flagellin and rotate; eukaryotic flagella have 9+2 microtubule arrangement and move by bending