Microbio Exam 1

Microbiology

The study of organisms that are too small to be seen with naked eye; special techniques are required to isolate and grow them

Microorganisms (microbes)

Organisms that are too small to be seen clearly with the naked eye and lack differentiated cells and distinct tissues

Prokaryotic Cells

Cells that lack a true, membrane-enclosed nucleus; Bacteria and Archaea are prokaryotic and have their genetic material located in a nucleoid

Eukaryotic Cells

cells that have a true, membrane-enclosed nucleus; they are typically larger and more complex than prokaryotes

Why have infectious diseases drooped off the top three leading causes of death in the United States over the past century?

Antibiotics, vaccines and improved public health efforts

Spontaneous generation

An early belief, now discredited, that living organisms could develop from nonliving matter

Which scientist disproved the theory of spontaneous generation?

Louis Pasteur

Koch’s Postulates

A set of rules used to prove that a specific microorganism causes a particular disease

True or False: All cells ave a cell membrane

True

True or False: All cells have a cell wall

False. Only certain prokaryotic and eukaryotic cells have a cell wall

Plasmids

Small pieces of extrachromosomal DNA that can carry antibiotic resistant genes or disease-causing genes.

True or False: Only eukaryotes have membrane-bound organelles.

True

Viruses

Infectious agent having a simple acellular organization with a protein coat and a nucleic acid genome, lacking independent metabolism, and reproducing only within living host cells.

Bacteria

The domain of life that contains prokaryotic cells with cell walls hat contain the structural molecule peptidoglycan; they have bacterial rRNA

Archaea

The domain of life that contains prokaryotic cells with cell walls that lack peptidoglycan; they have unique lipids in their membranes and archaeal rRNA (among may differences)

Eukarya

The domain of life that features organisms made of cells that have a membrane-delimited nucleus and differ in many other ways from prokaryotic cells; includes protists, fungi, plants, and animals

What are the four macromolecules?

Carbohydrates, lipids, proteins, and nucleic acids

What type of bond is formed when electrons are shared between the nuclei of two atoms so that they can fill their outer shells?

Covalent bond

Hydrogen bonding between water molecules (decreases/increases) he boiling point of a solution.

Increase

Water is an excellent solvent because of its ______ natrure.

polar

Enzymes (decrease/increase/do not change) the activation energy of a reaction.

Decrease

Condensation reactions are (anabolic/catabolic) pathways.

Anabolic

Which macromolecules accounts for the majority of the mass of a cell?

Protein

What type of linkage joins monosaccharides to form polysaccharides?

Glycosidic linkages

What type of linkage joins amino acids to form proteins?

Peptide bonds

Glycogen, chitin, cellulose, and starch are all made up of ____.

glucose

Fatty acids attach to the glycerol molecules in triglycerides via….

ester linkages

Fatty acids contain …

carbon and hydrogen

Saturated fatty acid

A fatty acid that consist of carbon molecules that are ‘saturated’ with bonds to hydrogen and thus do not have any double bonds

Unsaturated fatty acid

A fatty acid with at least one double bond

Amphipathic

Describes a molecule that has hydrophilic and hydrophobic regions or properties

what is an example of an amphipathic molecule?

Phospholipids

The nucleotide monomers of a single strand of DNA are held together via…

Phosphodiester linkages

Two strands of DNA and held together in a double helix structure by…

Hydrogen bonds

True or False: RNA’s only role in the body is for information storage

False. RNA also plays a role in structural support

Peptide bonds

The kind of bonds that link amino acids together in polypeptides or proteins

Primary Protein Structure

The amino acid sequence that makes up the backbone of the protein; held together by peptide bonds.

Protein Secondary Structure

Folding of the protein into characteristic shapes (such as alpha helices an beta-pleated sheets) due to hydrogen bonding

Protein Tertiary Structure

Folding of the Protein due to bonds between the variable side-chain groups; due to a number of interactions, including disulfide bridges and hydrophobic interactions

Protein Quaternary Structure

The highest level of protein structure formed by the combination of multiple polypeptide chains into functional units

Denaturation

A change in the folding or conformation of a protein due to an environmental change such as an increase in temperature or pH

Most proteins become functional when they have achieved ____ structure.

Tertiary

The average size of prokaryotic cells is about…

2 microns ( or 2 micrometers)

Which is smallest: viruses, prokaryotic cells, or eukaryotic cells?

Viruses

What are the two major categories of microscopy?

Light microscopy and electron microscopy

Resolution

The ability of a microscope to separate or distinguish between small objects that are close together

True or False: Electron microscopes produce images with greater magnification but poorer resolution than light microscopes.

False. They produce images with greater magnification and greater resolution.

Oil Emersion

A technique in which a drop of oil is placed between a slide and an objective lens to maximize the amount of light transmitted into the objective lens.

Refractive Index

A measure of how much a substance deflects a light ray from a straight path as it passes from one medium, such as glass, to another, such as air.

What are four types of light microscopes?

Bright-field microscopes, dark-field microscopes, phase-contrast microscopes, and fluorescence microscopes

Bright-field microscope

A microscope that illuminates the specimen directly with bright light and forms a dark image on a brighter background.

Dark-field microscope

A microscope that brightly illuminates the specimen while leaving the background dark

Phase-contrast microscope

A microscope that converts slight differences in refractive index and cell density unto easily observed differences in light intensity

Fluorescence microscopy

A type of microscopy that exposes a specimen to light of a specific wavelength and then forms an image from the fluorescent light produced; usually the specimen is stained with a fluorescent dye (fluorochrome)

Transmission Electron Microscope (TEM)

A microscope in which an image is formed by passing an electron beam through a specimen and focusing the scattered electrons with magnetic lenses

Scanning Electron Microscope (SEM)

An electron microscope that scans a beam of electrons over the surface of a specimen and forms an image of the surface from the electrons that are emitted by it

Confocal Scanning Laser Microscope (CSLM)

A light microscope in which laser derived light scans across the specimen at a specific level and illuminates one area at a time; stray light from other parts of the specimen is blocked out to give a three- dimensional image with excellent contrast and resolution

Wet mount

A technique for preparing slides that does not involve staining; a drop of liquid is placed on a slide, a specimen is placed in the liquid, a cover slide placed over the slide, and the slide is observed under a microscope.

Smear

A thin layer of cells attached to a microscope slide

Stain

A solution containing a solute called a chromophore, which gives the solution its color

Simple Staining

Staining a specimen with a single dye

Simple staining can provide information about cell…

morphology, size, and arrangement

Differential staining

Staining procedures that divide microbes into separate groups based on staining properties

Gram Stain

A differential staining procedure that divides bacteria into Gram-positive and Gram-negative groups based on their ability to retain crystal violet when decolorized with an organic solvent such as ethanol

What are the four steps involved in the Gram stain technique?

(1) Crystal violet; (2) Iodine; (3) Alcohol; (4) Safranin

Acid-fast Stain

A type of differential stain that uses a harsh acid treatment to identify mycobacteria, including the mycobacteria that causes tuberculosis and leprosy

Murein

Another name for peptidoglycan; the polysaccharide component of the bacteria cell wall

True or False: The components of the Electron Transport Chain are located along the bacterial cell wall

False. They are located along the bacterial membrane

Peptidoglycan is a polymer of two sugars. What are those two sugars?

N-Acetylglucosamine (NAG) and N-acetylmuramic acid (NAM)

Which aspect of the bacterial cell maintains the cell shape and protects against osmotic stress?

Bacterial cell wall

True or False: peptidoglycan is found in the cell membrane of bacteria only

False. Peptidoglycan is found in the cell wall, not the cell membrane

Teichoic acids

A substance found only in the cell walls of Gram-positive bacteria that provides additional rigidity to the cell

True or False: Some bacteria do not have cell walls.

True. For example, Mycoplasma is a bacteria genus that lacks cell walls.

True or False: Only Gram-negative bacteria have cell walls made of peptidoglycan.

False. Both Gram-positive and Gram-negative bacteria have cell walls made of peptidoglycan. However the cell walls of Gram-positive have many more layers than the cell walls of Gram-negative bacteria.

Which type of bacterial cell has an outer membrane?

Gram-negative bacteria

Lipopolysaccharides (LPS)

(also known as endotoxin.) The portion of the outer membrane of a Gram-negative bacteria that contains a highly toxic compound called lipid A.

Periplasmic Space

(also known as periplasm.) The space between the inner membrane and outer membrane of Gram-negative bacteria

Lysozyme

An enzyme produced by human cells in response to infection. It destroys celll wall sof pathogens.

Which is more susceptible to lysozyme: Gram-positive or Gram-negative bacteria?

Gram-positive bacteria

Which is more susceptible to the human complement system: Gram-positive or Gram-negative bacteria?

Gram-negative bacteria

Is it easier for penicillin to access the cell walls of Gram-positive or Gram-negative bacteria?

Gram-positive bacteria

Fluid-mosaic model

A model that describes the structure of a cell membrane. This model describes the cell membrane as a sea of proteins floating on or in a bed of loosely associated phospholipids.

True or false: Transmembrane proteins are peripheral proteins.

False. They are integral proteins (proteins that cross into the hydrophobic portion of the bilayer), not peripheral proteins (proteins that are loosely associated with the outside of the cell membrane).

Hopanoids

A steroid-like molecule that strengthens prokaryotic membranes, much like cholesterol does in eukaryotic membranes

True or False: The cell membrane regulates osmotic pressure

False. The cell wall regulates osmotic pressure

Capsule

A well-organized layer of polysaccharides and other materials that helps a bacterium resist the impact of phagocytic cells in a host’s immune system. It is difficult to remove

Slime layer

A loosely organized layer of polysaccharides and other materials that is more easily removed than the capsule layer

S-Layer

An extracellular portion of the cell envelope found in Bactria and in Archaea It consists of a protein or glycoprotein, and it has many functions.

Glycocalyx

A gelatinous, amorphous material found on the outside of many cells, which is involved in adhesion and makes the formation of biofilm possible

Fimbrae

Thin, short, hairlike appendages that cover the cell and are involved in attachment to surfaces.

Sex-pili

Long, thick appendages that are few in number; they are involved in the exchange of genetic information between bacterial cells

Flagellum

A lash-like appendage found in certain prokaryotic and eukaryotic cells; these are usually invisible with a light microscope, but flagellar staining techniques make them visible.

Chemotaxis

Occurs when a bacterial cell moves towards a chemical attractant or away from a chemical repellent

True or false: Cilia make tumble-and-run possible for bacteria

False. Flagella make this possible. Cilia are not found n prokaryotic cells.

Ensospore

A dormant form of a living bacterium, which can survive in harsh conditions that would otherwise be inhospitable to life.

Pleomorphic

Describes some bacterial cells, ability to change shape or size in response to environmental conditions

True or False: Lipopolysaccharides are found in Gram-negative bacteria but not Gram positive bacteria.

True.

True or False; The bacterial cell wall is made of murein.

True. (Murein is another name for peptidoglycan.)

True or False: S-layer are found in Archaea.

True..

True or False: Endotoxin is only found in the outer membrane of gram-negative bacteria.

True. Endotoxin is another name for lipopolysaccharide (LPS).