Microbiology Exam2

What are essential nutrients?

Substances a microorganism must obtain to grow and survive.

What are the six major elements needed by microbial cells?

Carbon, hydrogen, oxygen, nitrogen, phosphorus, and sulfur.

What is the function of carbon in a bacterial cell?

Builds organic molecules such as carbohydrates, lipids, proteins, and nucleic acids.

What is the function of nitrogen in a bacterial cell?

Needed to make proteins and nucleic acids.

What is the function of phosphorus in a bacterial cell?

Needed for ATP, DNA, RNA, and phospholipids.

What is the function of sulfur in a bacterial cell?

Needed to make certain amino acids and proteins.

What are macronutrients?

Nutrients required in relatively large amounts for cell structure and function.

What are micronutrients?

Nutrients required in very small amounts, often to help enzymes function.

Give examples of microbial trace elements.

Zinc, manganese, cobalt, molybdenum, nickel, and copper.

What is the difference between macronutrients and micronutrients?

Macronutrients are needed in larger amounts; micronutrients are needed in tiny amounts.

What is a photoautotroph?

An organism that uses light for energy and carbon dioxide as its carbon source.

What is a chemoautotroph?

An organism that obtains energy from chemicals and carbon from carbon dioxide.

What is a photoheterotroph?

An organism that uses light for energy and organic compounds for carbon.

What is a chemoheterotroph?

An organism that obtains energy and carbon from organic compounds.

What does photo mean in microbial nutritional classifications?

Light is the energy source.

What does chemo mean in microbial nutritional classifications?

Chemicals are the energy source.

What does auto mean in microbial nutritional classifications?

Carbon comes from carbon dioxide or another inorganic carbon source.

What does hetero mean in microbial nutritional classifications?

Carbon comes from organic compounds.

What is a saprobe?

An organism that obtains nutrients from dead or decaying organic matter.

What is the role of saprobic microorganisms in nature?

They decompose dead material and recycle nutrients into the environment.

What is diffusion?

Movement of particles from higher concentration to lower concentration.

What is osmosis?

Movement of water across a selectively permeable membrane toward the side with higher effective solute concentration.

What is the main difference between diffusion and osmosis?

Diffusion moves particles; osmosis specifically moves water across a selectively permeable membrane.

What happens to a cell in an isotonic solution?

Water moves in both directions equally, so there is no net water movement.

What happens to a cell in a hypotonic solution?

Water enters the cell because the surrounding solution has a lower solute concentration.

What happens to a bacterial cell in a hypertonic solution?

Water leaves the cell, which may cause the cytoplasm to shrink away from the cell wall.

What is plasmolysis?

Shrinking of the cytoplasm away from the cell wall after water leaves a cell.

What does hypo mean when describing a solution?

Lower solute concentration outside the cell, causing water to tend to enter.

What does hyper mean when describing a solution?

Higher solute concentration outside the cell, causing water to tend to leave.

What does iso mean when describing a solution?

Equal or approximately equal solute concentrations.

What are two types of passive transport?

Simple diffusion and facilitated diffusion.

What is simple diffusion?

Movement of substances down their concentration gradient without direct energy use.

What is facilitated diffusion?

Movement down a concentration gradient through membrane transport proteins without direct energy use.

What are three types of active transport?

Primary active transport, secondary active transport, and group translocation.

What is primary active transport?

Transport that directly uses an energy source, such as ATP, to move substances across a membrane.

What is secondary active transport?

Transport that uses energy stored in an ion gradient to move another substance.

What is group translocation?

Transport in which a substance is chemically modified as it enters the cell.

What is the difference between passive and active transport?

Passive transport does not directly require energy; active transport requires an energy source.

What is a psychrophile?

A microorganism adapted to cold environments that grows best at very low temperatures.

What is a psychrotroph?

A microorganism that can grow at refrigerator temperatures but usually grows best at warmer temperatures.

What is a mesophile?

A microorganism that grows best at moderate temperatures.

What is a thermophile?

A microorganism that grows best at high temperatures.

What is a hyperthermophile?

A microorganism that grows best at extremely high temperatures, often 80 degrees Celsius or above.

How do microorganisms adapt to cold temperatures?

They modify membrane lipids, produce cold-active enzymes, and use protective molecules.

How do microorganisms adapt to high temperatures?

They use heat-stable proteins and enzymes, stable membranes, and molecules that protect DNA and proteins.

What is an obligate aerobe?

A microorganism that requires oxygen for growth.

What is a facultative anaerobe?

A microorganism that grows with or without oxygen but usually grows better with oxygen.

What is an obligate anaerobe?

A microorganism that is harmed or killed by oxygen.

What is an aerotolerant anaerobe?

A microorganism that tolerates oxygen but does not use it for energy production.

What is a microaerophile?

A microorganism that requires oxygen at lower concentrations than those found in normal air.

What does catalase do?

Breaks hydrogen peroxide into water and oxygen.

What does superoxide dismutase do?

Converts harmful superoxide into oxygen and hydrogen peroxide.

What does peroxidase do?

Helps break down hydrogen peroxide using an electron donor.

What is an acidophile?

A microorganism that grows best in acidic conditions.

What is a neutrophile?

A microorganism that grows best near neutral pH.

What is an alkaliphile?

A microorganism that grows best in alkaline conditions.

What is a halophile?

A microorganism that grows best in high-salt environments.

What is a barophile or piezophile?

A microorganism adapted to high pressure.

What is mutualism?

A relationship in which both organisms benefit.

What is commensalism?

A relationship in which one organism benefits and the other is not significantly affected.

What is parasitism?

A relationship in which one organism benefits while harming its host.

What is competition between microorganisms?

A relationship in which organisms compete for limited resources such as nutrients or space.

What is amensalism?

A relationship in which one organism is harmed while the other is not significantly affected.

What is synergism?

A relationship in which organisms cooperate to produce a combined benefit.

What is a biofilm?

A community of microorganisms attached to a surface and surrounded by a self-produced protective matrix.

What is the extracellular polymeric substance matrix in a biofilm?

A protective material made of substances such as polysaccharides, proteins, and extracellular DNA.

Why are biofilm microbes often difficult to eliminate?

Their protective matrix and altered growth conditions can increase resistance to antimicrobials and immune defenses.

What is quorum sensing?

Chemical communication that allows microbes to coordinate activities according to population density.

What is binary fission?

Asexual reproduction in which one bacterial cell divides into two daughter cells.

What are the main steps of binary fission?

DNA replication, chromosome separation, cell elongation, septum formation, and cell separation.

What is doubling time?

The time needed for a microbial population to double in number under specific conditions.

What is exponential growth?

Growth in which a population repeatedly doubles, producing an increasingly rapid increase in cell number.

What is the formula for exponential microbial growth?

Final cell number equals starting cell number multiplied by 2 raised to the number of generations.

What happens during the lag phase of bacterial growth?

Cells adjust to their environment and prepare for division, with little increase in cell number.

What happens during the log phase of bacterial growth?

Cells divide rapidly at a relatively constant rate.

What happens during the stationary phase of bacterial growth?

Cell production roughly balances cell death because nutrients become limited and wastes accumulate.

What happens during the death phase of bacterial growth?

More cells die than are produced, causing viable cell numbers to decrease.

What is a culture-based method of measuring bacterial growth?

Viable plate count, which measures colony-forming units.

What is a non-culture-based method of measuring bacterial growth?

Direct microscopic counting, which counts cells without requiring colony growth.

What does CFU stand for?

Colony-forming unit, an estimate of viable microorganisms capable of producing colonies under the conditions used.

What is metabolism?

The sum of all chemical reactions occurring in a cell.

What is catabolism?

Breakdown of larger molecules into smaller molecules, often releasing usable energy.

What is anabolism?

Building larger molecules from smaller molecules, requiring energy.

What is the difference between catabolism and anabolism?

Catabolism breaks molecules down; anabolism builds molecules up.

What is an enzyme?

A biological catalyst that speeds up a chemical reaction without being permanently consumed.

What is a substrate?

The substance on which an enzyme acts.

What is an enzyme's active site?

The region where the substrate binds and the reaction occurs.

What is an enzyme-substrate complex?

The temporary combination formed when a substrate binds to an enzyme.

What is activation energy?

The energy barrier that must be overcome for a chemical reaction to begin.

How do enzymes speed up reactions?

They lower activation energy without changing the reaction's overall energy difference.

What is a cofactor?

A nonprotein helper, such as a metal ion, needed by certain enzymes.

What is a coenzyme?

An organic helper molecule that assists an enzyme, often derived from a vitamin.

What is an apoenzyme?

The protein portion of an enzyme without its required helper molecule or cofactor.

What is a holoenzyme?

The complete enzyme consisting of an apoenzyme and its required helper.

What do oxidoreductases do?

Catalyze oxidation-reduction reactions involving electron transfer.

What do transferases do?

Transfer functional groups between molecules.

What do hydrolases do?

Break chemical bonds by adding water.

What do lyases do?

Add or remove groups without using hydrolysis or oxidation-reduction.

What do isomerases do?

Rearrange atoms within a molecule to form an isomer.

What do ligases do?

Join molecules together, usually using energy.