62 Questions
What process reduces CO2 to generate complex, organic cell constituents?
Autotrophy
Which type of microorganisms can use both organotrophy and autotrophy to gain carbon?
Mixotrophs
What do chemoorganoheterotrophs obtain energy and carbon for biomass from?
Organic compounds
What role do cyanobacteria play in the Earth's marine food chain?
They fix carbon and form the base of the food chain
Which metabolic process involves obtaining energy from the catabolism of organic compounds and through light absorption?
Photoorganotrophy
What does the suffix "-trophy" refer to in biology?
Acquisition of nutrients
What is the electron source in organo-trophy?
Organic molecules donate electrons
How is energy stored in the form of an electrical potential across the membrane known?
Membrane potential
What do nitrogen-fixing bacteria convert nitrogen gas (N2) into?
Ammonium ions (NH4+)
Which process uses nitrate and related inorganic forms of nitrogen as terminal electron acceptors for certain electron transport chains?
Denitrification
What are the six macronutrients required by microorganisms?
Carbon, nitrogen, phosphorus, hydrogen, oxygen, and sulfur
What is the recycling process that involves two counterbalancing kinds of metabolism?
The carbon cycle
What is the role of micronutrients in cells?
They are essential components of enzymes or cofactors
What is the main difference between heterotrophy and autotrophy?
Heterotrophy breaks down multicarbon nutrients to carbon dioxide, while autotrophy reassembles CO2 molecules into multicarbon nutrients
What is the function of cations in microorganisms?
They serve as cofactors for specific enzymes or act as regulatory signaling molecules
What is the term for environments that lack oxygen?
Anaerobic
What is the class of anaerobes that can grow with or without molecular oxygen?
Facultative anaerobes
What is the process called when microbes gain energy only through fermenting carbohydrates in an oxygen-free environment?
Fermentation
What is the term for the membrane proteins and lipids used by some microbes to extract intrinsic energy from electrons?
Electron transport system
What is the term for the process involving the movement of electrons along an ETS and the generation of proton motive force if the electron donor is from an organic source?
Respiration
What differentiates facultative anaerobes from aerotolerant anaerobes?
Facultative anaerobes can grow with or without oxygen and have both fermentation and respiratory potential, while aerotolerant anaerobes use only fermentation to provide energy
What allows aerotolerant anaerobes to grow in air (containing oxygen) while retaining fermentation-based metabolism?
Contain superoxide dismutase and catalase (or peroxidase) to protect them from ROS
What is the primary benefit of oxygen for aerobes?
It serves as a terminal electron acceptor to extract energy from nutrients
Why do some microorganisms become microaerophilic?
As a result of possessing decreased levels of superoxide dismutase and/or catalase
What is the process of breaking down complex food into small molecules that can be digested called?
Catabolism
What is the main role of our gut microbiome in relation to the food we eat?
To break down complex foods into small molecules
Why do many of our gut microbes use enzymes that our bodies don't have?
To catabolize food molecules more efficiently
What is the term for obtaining energy from inorganic reactions?
Lithotrophy
Which type of microorganisms can use light absorption to gain energy and build biomass solely from CO2?
Photoautotrophs
What is the term for the process of obtaining energy from electron transfer between chemicals?
Chemotrophy
Which metabolic process involves obtaining energy from the catabolism of organic compounds and through light absorption?
Chemoorganotrophy
What is the term for microorganisms that use preformed organic compounds for biosynthesis?
Heterotrophs
What is the term for the process that involves obtaining energy from the catabolism of organic compounds and through light absorption?
Photosynthesis
What do exothermic reactions release?
Heat
What determines how much energy is potentially available to do work in a biochemical reaction?
DeltaG
What is the term for environments that lack oxygen?
Anaerobic
What is the electron source in organotrophy?
Organic molecules
What is the main role of lignin in trees and woody plants?
Structural support
What is the main difference between fermentation and respiration?
Fermentation breaks down large molecules into smaller products, while respiration transfers electrons to an electron acceptor
Which of the following can human enzymes digest?
Starch
What is the process by which carbohydrates are broken down to monosaccharides?
Hydrolysis
What happens to the electrons removed from food in the process of respiration?
They are transferred to an inorganic electron acceptor
During mixed-acid fermentation, what is favored at low pH?
Ethanol and lactate
Which molecule serves as the 'lego block' of metabolism?
Acetyl-CoA
What is the key component of metabolism in bacteria and mitochondria, directing sugar catabolism into respiration?
Pyruvate dehydrogenase complex (PDC)
Which process removes CO2 from pyruvate, generating acetyl-CoA?
The tricarboxylic acid (TCA) cycle
Which pathway produces 2 ATP and 2 NADH from glucose breakdown?
Embsen-Meyerhof-Parnas (EMP) pathway
What term is used for organisms that are capable of utilizing light to generate ATP, but also incorporate preformed organic compounds for biosynthesis?
Photoheterotrophs
What metabolic process involves the capture of light by chlorophyll or another photopigment?
Phototorphy
What is the term for metabolism in which chemical electron donors yield energy through an Electron Transport Chain (ETC)?
Respiration
Which term describes the reduction of oxidized forms of nitrogen for energy yields?
Dissimilatory denitrification
What is the primary electron acceptor in anaerobic respiration?
Metal cations
What is the main difference between dissimilatory denitrification and assimilatory reduction of nitrate?
The end product of the process
What is the process called when hydrogen is used as an electron donor and carbon dioxide is reduced to methane?
Methanogenesis
What is the term for the process of oxidation of inorganic electron donors to acquire energy?
Lithotrophy
Which group of microorganisms specifically oxidizes methane, nitrite, or sulfate to gain energy from single-carbon compounds?
Methanotrophs
What is the process called when microorganisms obtain carbon skeletons by CO2 fixation or by breaking down compounds formed by other organisms?
Autotrophy
What must the organism's genome maintain in order to support biosynthesis?
DNA encoding all the enzymes that catalyze biosynthetic pathways
How do microbes regulate their biosynthesis at the levels of transcription and translation of enzymes?
By controlling the relative investment in energy yielding reactions versus energy-spending reactions
Where is the full Calvin cycle found?
In bacteria and chloroplasts
Which organisms are believed to generate the majority of the oxygen gas in Earth's atmosphere?
Cyanobacteria
How do facultatively anaerobic purple bacteria, including sulfur oxidizers and photoheterotrophs, obtain carbon?
Through the Calvin cycle
Test your knowledge on the essential nutrients required by microorganisms and the role of macronutrients in microbial growth and metabolism.
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