exam 1

learning objectives (unit 1 - lsn 1-5)

describe the contributions of Antoni van Leeuwenhoek to the field of microbiology

• originally a textile merchant - used lenses to inspect fabric quality

• created simple microscopes (did NOT create the first microscope)

• KNOWN FOR: discovering bacteria (tiny animals - animalcules) and documenting them

  • will be later called microorganisms

list and describe six groups of microorganisms and differentiate prokaryotic from

eukaryotic microorganisms

prokaryotes (no defined nucleus, usually smaller than eukaryotes): bacteria and archaea

eukaryotes (defined nucleus, usually larger than prokaryotes): fungi. protozoa, algae, and helminths

bacteria

• unicellular and lack nuclei

• much smaller than eukaryotic cells

• found anywhere moisture exists

• reproduces asexually

• peptidoglycan in cell walls

• some lack a cell well altogether

archaea

• unicellular and lack nuclei

• much smaller than eukaryotic cells

• found anywhere moisture exists

• reproduces asexually

• cell walls are made from different polymers

• lives in extreme environments (hot springs)

fungi

• eukaryotic (has membrane bound organelles)

• heterotrophic: obtains food from other organisms

• cell walls composed of chitin

molds

• multicellular

• grows as long filaments

• reproduce by sexual and asexual spores

yeasts

• unicellular

• reproduce asexually by budding

• some produce sexual spores

protozoa

• single-celled eukaryotes

• lack a cell wall

• animal-like nutrients needs and structure

• live freely in water or inside animal hosts

pseudopods: false feet, flowing extensions of cytoplasm (crawling movements)

cilia: many short, hair-like structures for swimming

flagella: few long, whip-like tails for propulsion

algae

vary widely in size, shape, pigmentation, and structure

• unicellular or multicellular

• photosynthetic (uses sunlight for food)

• simple reproductive structures

• classification: based on pigmentation and cell wall composition

helminths

compare and contrast the investigations of Redi, Needham, and Spallanzani

concerning spontaneous generation (life arising from nonliving matter)

Redi’s experiment

designed a direct test of spontaneous generation

• meat kept isolated from flies never developed maggots

• meat exposed to flies became infested with maggots

• maggots arose from fly eggs, not the meat itself

challenges Aristotle’s theory and case the first serious doubt on spontaneous generation

Needham’s experiment

tested spontaneous generation

• boiled beef gravy and plant infusions briefly (did not sterilize)

• sealed flasks with corks after boiling (cork is permeable to air)

  • microbes still appeared in sealed flasks

• life must arise from nonliving matter-possibly via a “life force”

results seemed to support Aristotle’s view - that microbes could arise from nonliving matter

Spallanzani’s experiment

challenged Needham’s conclusions

• boiled broth for one hour (sterilized)

• sealed flasks by melting the necks or using wax (not permeable to air)

• no growth unless flasks were exposed to air

strong evidence against spontaneous generation

showed that air exposure, not “life force” was necessary for microbial growth

describe the contributions of Louis Pasteur to the field of microbiology relative to

spontaneous generation

used swan-shaped necks to trap airborne particles

flasks left upright showed no microbial growth (outside air could not reach the flask)

when tilted, dust from the neck entered the broth, cloudy with microbes in 1 day

microbes came from the environment, not spontaneous generation

Louis Pasteur to the field of microbiology relative to fermentation

spoiled wine threatened the livelihoods of many grape growers, wine produces funded research to promote alcohol production and production and prevent spoilage during fermentation, cause of fermentation reactions become linked to the broader debate over spontaneous generation

• demonstrated that heating liquids could kill most microbes without ruining flavor

• developed the process of pasteurization

• founded the filed of industrial microbiology - intentional use of microbes to manufacture products

Eduard Buchner’s biochemistry

scientists still debated whether cells themselves were required for fermentation

• his experiment showed fermentation could occur without living cells

• demonstrated that enzymes (cell-free extracts) drive chemical reactions

proved biological reactions can occur outside cells

marked the beginning of modern biochemistry

Louis Pasteur to the field of microbiology relative to germ theory of disease

people believed that bad air (miasma) caused disease

• from Hippocrates

• claimed disease arose from “noxious air”

Pasteur proposed the germ theory of disease

Robert Koch provided experimental proof using isolated microbes

• showed that specific microorganisms cause specific diseases

• pathogens

list and describe the steps of the scientific method

observation: notice something unusual

question: ask a specific question based on the observation

hypothesis: propose a testable explanation

experiment: test the hypothesis through controlled experiments

distinguish between hypothesis and theory

hypothesis: a proposed explanation for a phenomenon, formulated as a testable statement that can be supported or refuted through experimentation and observation

theory: a well-substantiated explanation of some aspect of the natural world that is supported by a body of evidence and has withstood multiple tests through scientific methods

Describe Robert Koch’s contributions to the field of microbiology

• developed simple staining techniques

• created the first photomicrograph of bacteria

• took the first photograph of bacteria in diseased tissue

• devised methods for estimating bacterial numbers in solutions

• introduced steam sterilization of growth media

• popularized the Petri dish (invented by Julius Petri)

• refined lab transfer techniques for culturing bacteria

• recognized bacteria as distinct species

identify each of the four steps that compose “Koch’s postulates”

scientists lacked proof that microbes were responsible for specific diseases

• studied causative agents of disease (etiology - study of the cause of disease)

• demonstrated that a bacterium causes anthrax

• used microbial colonies to like individual microbes to particular diseases

1. suspected agent must be found in every case of disease and absent from healthy hosts

2. agent must be isolated and grown outside the hose (pure culture)

3. when the agent is introduced into a healthy, susceptible host, the host must get the disease

4. same agent must be re-isolated from the newly diseased host

formed the basis for linking specific microbes to specific diseases

apply basic chemistry concepts to the study of microbiology: atomic structure, isotopes, and electron configurations

atomic structure

• atomic number = number of protons (change this number = change the element)

• atomic mass = protons + neutron (atomic mass units - amu), electrons have no mass

isotopes = atoms with the same number of proton but different numbers of neutrons

electron configurations

• complex 3D shapes that describe where electrons most likely to be found

• orbitals represent spatial probability zones, not fixed paths

• valence = the ability of an atom to bond with others - lose, gain or share

apply basic chemistry concepts to the study of microbiology: molecules vs. compounds

molecule = two or more atoms held together by chemical bonds

compound = a molecule made of different elements

apply basic chemistry concepts to the study of microbiology: covalent bonding vs. ionic bonding

covalent bond = sharing a pair of electrons between atoms

ionic bond = formed when electrons are transferred (difference in electronegativity >, or equal to 2.0)

apply basic chemistry concepts to the study of microbiology: nonpolar vs. polar covalent bonds

nonpolar covalent bonds = electrons are shared equally, resulting in no charge (difference in electronegativity 0.0 - 0.4)

polar covalent bonds = electrons are shared unequally, pulled more toward one atom (difference in electronegativity 0.5 - 1.9)

apply basic chemistry concepts to the study of microbiology: hydrogen bonds

hydrogen bonds = electrostatic attractions between a partially positive hydrogen and a partially or fully negative atom (often O or N)

• weaker than covalent bonds - important in biological structures

  • stabilize 3D structures of large molecules

  • allow DNA strands to separate and rejoin during replication/transcription

give an example of a synthesis reaction, decomposition reaction, and exchange reaction

synthesis = a chemical process where two or more simple substances chemically bond to form a single, more complex product

decomposition = a chemical change where one complex compound breaks down into two or more simpler substances

exchange = a chemical reaction in which both synthesis and decomposition occur, chemical bones are both formed and broken, and chemical energy is absorbed, stored, and released

describe the properties of water: cohesion, adhesion, solvent, high specific heat capacity

cohesion = water molecules stick to each other

• caused by hydrogen bonding

• responsible for surface tension (why droplets form and bugs can walk on water)

adhesion = water molecules stick to other surfaces, especially polar or charged ones

• helps water cling to glass, plant tissue, and paper

• drives capillary actions (ex: water climbing a plant stem)

high specific heat capacity

• the amount of energy needed to convert 1 gram of liquid into gas

• high heat of vaporization due to hydrogen bonding

• helps regulate temperatures in ecosystems and our bodies

describe the properties of water: role of water in biochemical reactions

role of water in biochemical reactions

• dissolve many substances, especially ions and polar molecules

• water is polar, allowing it to surround and separate charged particles

  • solvent (water) = substance doing the dissolving

  • solute (ex: NaCl) = substance being dissolved

• universal solvent makes it essential for transport, metabolism, and cellular function

• solubility drives everything from blood chemistry to nutrient absorption

contrast acids, bases, and salts and explain the role of buffers relative to pH change

acids: releases H+ (protons) into solution)

• more H+ → lower pH (acidic)

base: either binds to H+ or releases OH-

• more OH- → higher pH (basic)

acids donate protons, bases accept them

pH is the power of hydrogen

buffers = resist sudden changes in pH by neutralizing small amounts of added acid or base

• ex: bicarbonate buffer system keeps blood pH around 7.4

• most biochemical reactions only work properly within a narrow pH range

• metabolism depends on maintaining a stable acid-base balance

• different animals have different pH tolerances (ex: 6.5-8.5)

list the four classes of biological macromolecules and understand their synthesis through dehydration synthesis reactions and breakdown through hydrolysis reactions

1. carbohydrates - quick energy and structural support

2. proteins - catalysts, cell structure, and signaling molecules

3. lipids - energy storage, membranes, and hormones

4. nucleic acids - genetic blueprints

   1. all macromolecules are organic - they contain carbon

functional group - hydroxyl

—OH

polar, forms H-bonds

alcohols, sugars

functional group - ether

—O—

links sugar units

disaccharides

functional group - ketone

C=O (internal)

reactive carbonyl

sugars

functional group - aldehyde

—CHO (terminal)

reactive carbonyl

sugars

functional group - carboxyl

—COOH

acidic, donates H+

amino acids, fatty acids

functional group - amino

—NH₂

basic, accepts H+

amino acids

functional group - ester

—COOR

hydrophobic linkage

fats, waxes

functional group - sulfhydryl

—SH

forms disulfide bridges

protein folding

functional group - phosphate

—PO₄

high energy, negative charge

ATP, nucleotides, phospholipids

functional group - methyl

—CH₃

hydrophobic, nonpolar

lipids, gene regulation

discuss the roles of carbohydrates in living systems

functions:

• ready energy (glucose, sucrose)

• long-term energy storage (starch and glycogen)

• form the backbone of nucleic acids (ribose and deoxyribose)

• can be converted to amino acids

• structural components (cellulose in plants and peptidoglycan in bacteria)

• involved in cell recognition and signaling (glycoproteins/glycolipids)

recognize the basic structure of carbohydrates

monosaccharides - single sugar units (glucose, fructose)

disaccharides - two sugars bonded together (sucrose, lactose)

polysaccharides - long chains of sugars (starch, cellulose, glycogen)

• glycosidic bond/linkage - bonds linking sugar

recognize the basic structure of carbohydrates (cont. OH configuration)

a-glucose - found in starch (digestible by humans)

• OH on 1st carbon is below the plate

b-glucose - found in cellulose (not digestible by humans)

• OH on 1st carbon is above the plate

N-acetylglucosamine

• modified monosaccharide used in peptidoglycan (bacteria cell walls) and chitin (fungi, arthropods)

cellulose

straight chains, linked by β-1,4 bonds → structural support (plants, fiber)

not digestible by humans

• branching increases energy accessibility

• linear structures increase stability and

strength

amylose (starch)

unbranched helical chains, linked by α-1,4 bonds → energy storage in plants

• branching increases energy accessibility

• linear structures increase stability and

strength

glycogen

highly branched chains, linked by α-1,4 and α-1,6 bonds → energy storage in animals

fast access to glucose

• branching increases energy accessibility

• linear structures increase stability and

strength

sketch and label the basic structure of a nucleotide - building blocks of nucleic acids

phosphate group

pentose sugar (ribose or deoxyribose)

nitrogenous base (A, T, G, C, or U)

nucleoside - sugar + base (no phosphate)

• linked into a polymer by phosphodiester bonds

DNA vs RNA

DNA:

• inheritance and genome stability

• long-term genetic storage

• deoxyribose sugar

• contains thymine

• antiparallel, complementary, 2 strands, stable (H on 2nd carbon)

RNA:

• protein synthesis, regulation, catalysis

• assists with gene expression, protein building, and sometimes acts as an enzyme

• ribose sugar

• contains uracil

• more reactive (OH on 2nd carbon), one strand

nitrogenous base - pyrimidines

cytosine, thymine (DNA), uracil (RNA)

nitrogenous base - purines

adenine, guanine

ATP vs ADP vs AMP

contains:

• ribose (sugar)

• adenine (nitrogenous base)

triphosphate - 3 phosphate groups

diphosphate - 2 phosphate groups

monophosphate - 1 phosphate group

ATP

• main short-term energy supply for cells

• energy is release when phosphate bonds of ATP are broken

• ATP supply is limited and must be replenished

sketch the basic structure of an amino acid

describe five general functions of proteins in living things

structure - keratin in skin and collagen in connective tissue

catalysis - enzymes accelerate chemical reactions

regulation - hormones and gene regulators (ex: insulin, repressors)

transport - channel and carrier proteins in cell membranes

defense and offense - antibodies, toxins, and complement proteins

label the four levels of protein structure and elucidate five different factors that promote protein folding and stability

hydrogen bonds: Bonds form between atoms in the polypeptide backbone and between atoms in different side chains

ionic bonds: bones form between oppositely charged side chains

hydrophobic effect: nonpolar amino acids in the center of the protein avoid contact with water

van der Waals forces: attractive forces occur between atoms that are optimal distances apart

disulfide bridge: a covalent bond forms between 2 cysteine side chains

understand the structures and functions of lipids - triglyceride

linking three fatty acids to a glycerol backbone

• long-term energy storage

• saturated (no double bonds) vs. unsaturated (double bonds - 1 or more)

  • unsaturated bond - cis H is on same side - creating a kink

  • trans - H is on opposite sides - creating an unsaturated fat similar to saturated fats

understand the structures and functions of lipids - phospholipid

phosphate group + organic molecule

hydrophilic head, hydrophobic tail

kinks in unsaturated tails increase membrane fluidity

understand the structures and functions of lipids - waxes

1 long-chain fatty acid

linked to 1 long-chain alcohol

bonded via ester bond

lack a hydrophilic head, unlike phospholipid - totally water-insoluble

found in plants, insects, and animals

• leaf cuticles to prevent water loss

• glossy fruits

• beeswax

waterproof barriers, flexible armor against desiccation and environmental damage

understand the structures and functions of lipids - steroids

cholesterol - nestle between phospholipids in membranes, helping maintain fluidity and stability

ridged ring structure interacts with fatty acid tails, reducing membrane permeability and preventing freezing or collapse

starting point for hormones - testosterone, estrogen, cortisol

are not chains, but rather rings = slip through membranes and bind to internal receptors, triggering targeted cellular responses

describe the four classes of biological macromolecules, understand their monomers, polymers, examples, and functions

REFER TO SLIDES