Micro M3 final flashcards

What is metabolism and how do anabolism and catabolism differ?

Metabolism is all cellular chemical reactions. Catabolism breaks down molecules and releases energy. Anabolism builds molecules and requires energy

How are catabolism and anabolism connected?

Catabolism supplies ATP and precursor metabolites that anabolism uses to synthesize macromolecules and cellular structures

What are enzymes and how do they work?

Biological catalysts that lower activation energy and speed up reactions without being consumed. Substrates bind to specific active sites and are converted to products

What factors influence enzyme activity?

Temperature, pH, enzyme and substrate concentrations, and inhibitors. Extreme heat or pH can denature enzymes and disrupt their active sites

What are cofactors and coenzymes?

Cofactors are nonprotein helpers required by some enzymes. Coenzymes are organic cofactors such as vitamin-derived molecules

Compare competitive and noncompetitive enzyme inhibition.

Competitive inhibitors compete with substrates for the active site. Noncompetitive inhibitors bind elsewhere and change enzyme activity

What is feedback inhibition?

The end product of a metabolic pathway inhibits an earlier enzyme to prevent unnecessary production

What is ATP and how is it produced?

ATP is the main immediate cellular energy carrier. Cells produce it through substrate-level phosphorylation, oxidative phosphorylation, or photophosphorylation

What are oxidation and reduction in metabolism?

Oxidation is loss of electrons and reduction is gain of electrons. Redox reactions transfer energy between molecules

What do NADH and FADH2 do?

They carry high-energy electrons from catabolic reactions to the electron transport chain

What are the three main stages of aerobic glucose respiration?

Glycolysis, Krebs cycle, and electron transport chain with chemiosmosis

What happens during glycolysis?

One glucose is split into two pyruvate molecules in the cytoplasm. Two ATP are invested and four produced for a net gain of two ATP plus two NADH

What happens between glycolysis and the Krebs cycle?

Pyruvate is converted to acetyl-CoA while releasing carbon dioxide and producing NADH

What happens during the Krebs cycle?

Acetyl-CoA is oxidized to carbon dioxide while producing NADH, FADH2, and ATP or GTP

How does the electron transport chain produce ATP?

Electrons pass through membrane proteins that pump protons. Proton flow through ATP synthase drives ATP production by chemiosmosis

Compare aerobic and anaerobic respiration.

Both use an electron transport chain. Aerobic respiration uses oxygen as the final electron acceptor while anaerobic respiration uses inorganic acceptors such as nitrate or sulfate

What are the products of complete aerobic glucose respiration?

Carbon dioxide, water, and ATP. Oxygen serves as the final electron acceptor

What is fermentation and how does it differ from respiration?

Fermentation uses organic molecules as electron acceptors to regenerate NAD+. It has no respiratory electron transport chain and usually produces only the two ATP from glycolysis

What are common fermentation products and applications?

Lactic acid or ethanol and carbon dioxide. Fermentation is used in foods and can help identify microbes through their metabolic products

How are lipids and proteins used for energy?

Lipids split into glycerol for glycolysis and fatty acids for beta oxidation into acetyl-CoA. Proteins split into amino acids that are deaminated and enter metabolic pathways

What is photosynthesis and where does it occur in microbes?

Light energy drives ATP production and carbon fixation into organic molecules. Photosynthetic eukaryotes use chloroplasts while bacteria use photosynthetic membranes

Compare photophosphorylation and oxidative phosphorylation.

Photophosphorylation uses light-driven electron transport to make ATP. Oxidative phosphorylation uses electrons from nutrient oxidation

What are the main anabolic processes in microbes?

Synthesis of carbohydrates, lipids, amino acids, proteins, and nucleotides using ATP and metabolic precursors

How do microbes regulate metabolic pathways?

Through enzyme inhibition, feedback inhibition, and control of enzyme production to conserve energy and materials

What does microbial growth mean and what is generation time?

Microbial growth means an increase in cell number. Generation time is the time required for a population to double

How does bacterial population growth occur?

Binary fission produces exponential growth under favorable conditions with populations doubling each generation

What are the four phases of a bacterial growth curve?

Lag phase is adjustment. Log phase is rapid division. Stationary phase has equal growth and death. Death phase has more deaths than divisions

Why is the log phase important?

Cells are metabolically active and divide rapidly. They are useful for experiments and often especially susceptible to antibiotics targeting growth

What causes stationary and death phases?

Nutrient depletion, waste accumulation, and unfavorable environmental conditions. Stationary phase balances births and deaths while death phase loses viable cells

What nutrients do microorganisms require for growth?

Carbon, hydrogen, oxygen, nitrogen, phosphorus, sulfur, water, minerals, and sometimes growth factors such as vitamins or amino acids

Compare autotrophs and heterotrophs.

Autotrophs obtain carbon from carbon dioxide. Heterotrophs obtain carbon from organic compounds

Compare phototrophs and chemotrophs.

Phototrophs obtain energy from light. Chemotrophs obtain energy from chemical compounds

What are the four major nutritional classifications of microbes?

Photoautotrophs use light and CO2. Photoheterotrophs use light and organic carbon. Chemoautotrophs use chemicals and CO2. Chemoheterotrophs use chemicals and organic carbon

Compare the five oxygen requirements of microbes.

Obligate aerobes require oxygen. Obligate anaerobes cannot tolerate it. Facultative anaerobes grow with or without oxygen but prefer it. Aerotolerant anaerobes tolerate oxygen without using it. Microaerophiles require low oxygen

Why is oxygen toxic to some microbes and how is it detoxified?

Reactive oxygen species damage cells. Enzymes such as catalase and superoxide dismutase detoxify harmful oxygen compounds

What does a positive catalase test indicate?

Bubbles appear when hydrogen peroxide is converted into water and oxygen gas by catalase

How are microbes classified by preferred temperature?

Psychrophiles prefer cold. Psychrotrophs can grow in refrigeration. Mesophiles prefer moderate temperatures. Thermophiles prefer heat. Hyperthermophiles prefer extreme heat

How does pH affect microbial growth?

Acidophiles prefer acidic conditions, neutrophiles prefer near-neutral conditions, and alkaliphiles prefer alkaline conditions. Extreme pH disrupts enzyme function

How do water availability and osmotic pressure affect microbial growth?

High solute concentrations draw water out of cells and inhibit growth. Halophiles require salt while halotolerant microbes tolerate it

What are inoculum, medium, culture, and pure culture?

Inoculum is the introduced sample. Medium supplies nutrients. Culture is microbes growing in medium. Pure culture contains one microbial type

Why is aseptic technique important in culturing?

It prevents contamination of cultures and protects the accuracy of experiments and identification

Compare broth, solid agar, and semisolid media.

Broth supports growth in liquid. Solid agar allows isolated colonies. Semisolid media can test motility or support organisms needing reduced oxygen

Compare defined and complex media.

Defined or synthetic media have precisely known chemical compositions. Complex media contain ingredients such as extracts whose exact compositions vary

Compare selective, differential, and enriched media.

Selective media inhibit some microbes while permitting others. Differential media reveal biochemical differences. Enriched media support fastidious organisms with additional nutrients

What does blood agar demonstrate?

It is an enriched and differential medium that supports growth and distinguishes alpha, beta, and gamma hemolysis

How do streak plates and pour plates isolate microorganisms?

Streak plates progressively dilute cells across agar using an inoculating loop. Pour plates mix diluted samples with molten agar to form separated colonies

What is a colony-forming unit or CFU?

A viable cell or group of cells capable of forming one visible colony on suitable culture medium

How do serial dilutions and viable plate counts measure microbial growth?

Samples are diluted and plated. Colonies are counted and corrected for dilution and plated volume to estimate viable CFU per mL

Compare direct microscopic counts and electronic cell counters.

Microscopic counts rapidly count cells in a measured volume. Electronic counters rapidly detect cells or particles. Neither necessarily distinguishes live from dead cells

Compare direct and indirect microbial growth measurements.

Direct methods count cells or CFUs using plates, microscopy, filtration, or electronic counters. Indirect methods estimate growth through turbidity, biomass, or metabolic activity

When should plate counts, membrane filtration, and turbidity measurements be used?

Plate counts estimate viable culturable cells. Membrane filtration concentrates microbes from dilute liquids. Turbidity rapidly tracks dense liquid cultures but does not distinguish living from dead cells