Ch. 3 Flashcards
Nutrients
Supply of monomers (or precursors of) required by cells for growth
Macronutrients
Nutrients required in large amounts
Micronutrients
Nutrients required in trace amounts
___ is required by all cells.
Carbon
Typical bacterial cell is ____% carbon
~50%
What is a major element in all classes of macromolecules?
Carbon
Heterotrophs use organic ___.
Carbon
Autotrophs use carbon ___.
Dioxide
Typical bacterial cell is ___ nitrogen.
13%
What is a key element in proteins, nucleic acids, and many more cell constituents?
Nitrogen
Phosphorus
Synthesis of nucleic acids and phospholipids
Sulfur
- sulfur-containing amino acids
- vitamins and coenzyme A
___ is required by enzymes for activity.
Potassium
Magnesium
- stabilizes ribosomes, membranes, and nucleic acids
- also required for many enzymes
___ helps stabilize cell walls in microbes and plays key role in heat stability of endospores.
Calcium
Sodium
Required by some microbes
Key component of cytochromes and FeS proteins involved in election transport
Iron
Growth factors
Organic compounds required in small amounts by certain organisms
Examples of growth factors
Vitamins, amino acids, purines, pyrimidines
___ are the most commonly required growth factors.
Vitamins
Vitamins mostly function as ___.
Coenzymes
Culture media
Nutrient solutions used to grow microbes in the laboratory
Defined media
Precise chemical composition is known
Complex media
Composed of digests of chemically undefined substances
Enriched media
Contain complex media plus additional nutrients
Selective media
Contain compounds that selectively inhibit growth of some microbes but not others
Differential media
Contain an indicator, usually a dye, that detects particular chemical reactions occurring during growth
Pure culture
Culture containing only a single kind of microbes
Contaminants
Unwanted organisms in a culture
When grown on solid media, cells form isolated masses called ___.
Colonies
Solid media are prepared by addition of a gelling agent called ___.
Agar
Pure culture techniques:
Streak plate
Pour plate
Spread plate
Metabolism
The sum total of all of the chemical reactions that occur in a cell
Catabolic reactions (catabolism)
Energy-releasing metabolic reactions
Chemorganotrophs
An organism that obtains its energy from the oxidation of organic compounds
Chemolithotrophs
An organism that can grow with inorganic compounds as electron donors in energy metabolism
Phototrophs
Organisms that use light as their source of energy
Heterotrophs
An organism that uses organic compounds as a carbon source
Autotrophs
An organism capable of biosynthesizing all cell material from CO2 as the sole carbon source
Catalyst
Substance that:
- lowers the activation energy of a reaction
- increases reaction rate
- does not affect energetics or equilibrium of a reaction
Enzymes
- biological catalysts
- typically proteins
- highly specific
- generally larger than substrates
- typically rely on weak bonds
- increase the rate of chemical reactions by 10^8 to 10^20 times the spontaneous rate
Active site
Region of enzyme that binds substrate
Catalysis depends on:
- substrate binding
- position of substrate relative to catalytically active amino acids in active site
Many enzymes contain small ___ ___ that participate in catalysis but are not substrates
Nonprotejn molecules
Prosthetic groups
- bind tightly to enzymes
- usually bind covalently and permanently
Coenzymes
- loosely bound to enzymes
- most are derivatives of vitamins
Energy from ___ reactions is used in synthesis of energy-rich compounds
Oxidation-reduction (redox)
Redox reactions occur in pairs
Two half reactions
Electron donor
The substance oxidized in a redox reaction
Electron acceptor
The substance reduced in a redox reaction
Redox reactions usually involve reactions between intermediates called ___
Carriers
Electron carriers are divided into two classes:
Prosthetic groups
Coenzymes
___ and ___ facilitate redox reactions without being consumed; they are recycled.
NAD* and NADH
Two reaction series are linked to energy conservation in chemoorganotrophs:
Fermentation and respiration
Fermentation
Substrate-level phosphorylation; ATP is directly synthesized from an energy-rich intermediate
Respiration
Oxidative phosphorylation; ATP is produced from proton motive force formed by transport of electrons
___ substance is both an electron donor and an electron acceptor.
Fermented
Glycolysis
A common pathway for catabolism of glucose
How many ATP are produced from glycolysis?
Two
Fermentation classified by products formed:
- ethanol
- lactic acid
- propionic acid
- mixed acids
- butyric acid
- butanol
Fermentation classified by substrate fermented:
- usually not glucose
- amino acids
- purines and pyrimidines
- aromatic compounds
___ ___ can carry out fermentation or respiration
Saccharomycetes cerevisiae
Fermentation occurs when conditions are ___.
Anoxic
Aerobic respiration
- oxidation using O2 as the terminal electron acceptor
- higher ATP yield than fermentations
Yeast can reproduce asexually by ___.
Budding
Electron transport systems
- membrane-associated
- mediate transfer of electrons
- conserve some of the energy released during transfer and use it to synthesize ATP
- many oxidation-reduction enzymes are involved in electron transport
NADH dehydrogenases
Proteins bound to inside surface of cytoplasmic membrane; active site binds NADH and accepts 2 electrons and 2 protons that are passed to flavoproteins
Flavoproteins
Contains flavin prosthetic group that accepts 2 electrons and 2 protons but donates the electrons only to the next protein in the chain
Cytochromes
- proteins that contain heme prosthetic groups
- accept and donate a single electron via the iron atom in heme
Electron transport system oriented in cytoplasmic membrane so that..
Electrons are separated from protons
Electron carries arranged in membrane in order of their ___ ___.
Reduction potential
The final carrier in the chain donated the electrons and protons to the..
Terminal electron acceptor
Proton motive force
Results in generation of pH gradient and an electrochemical potential across the membrane
ATP synthase
Complex that converts proton motive force into ATP; two components
Citric acid cycle
Pathway through which pyruvate is completely oxidized to CO2
Microorganisms demonstrate a wide range of mechanisms for generating energy:
- fermentation
- aerobic respiration
- anaerobic respiration
- chemolithotrophy
- phototrophy
Anaerobic respiration
The use of electron acceptors other than oxygen
Chemolithotrophy
Used inorganic chemicals as electron donors
- typically aerobic
- begins with oxidation of inorganic electron donor
Photophosphorylation
Light-mediated ATP synthesis
Photoautotrophs
Uses ATP for assimilation of CO2 for biosynthesis
Photoheterotrophs
Uses ATP for assimilation of organic carbon for biosynthesis
Phototrophy
Uses light as energy source
Hemolysis
Ability to break down red blood cells
Alpha hemolysis
Partial destruction of red blood cells
Beta hemolysis
Complete destruction of red blood cells
Gamma hemolysis
No destruction of red blood cells
Chocolate agar
Partially lysed red blood cells
Blood agar
5% sheep blood
Anabolic
Building of macromolecules
Catabolic
Brohydration of macromolecules
Strict aerobes
Require oxygen all the time
Strict anaerobes
Can’t be present with oxygen
Fabultative anaerobes
Grow with or without oxygen
