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Microbes can grow under a wide range of ______ concentrations.
solute
The availability of water affects the growth of all ______.
cells
Higher ______ concentration leads to lower water activity.
solute
A hypotonic solution has a ______ extracellular solute concentration.
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An isotonic solution has the same ______ concentration in and out.
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A hypertonic solution has a ______ extracellular solute concentration.
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Molecular chaperones help to ______ damaged proteins.
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Lipids in membranes are stabilized with ______ linkage instead of ester.
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Enzymes ___________________ are catalase positive.
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Superoxide dismutase (SOD) breaks down ___________________ into oxygen and water.
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Microbes that grow in extremely high temperatures are called ___________________.
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The bacterium ___________________ is a source of Taq Polymerase.
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Microbes that grow in temperatures between 20-45°C are called ___________________.
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High temperature disrupts membranes, denatures ___________________ and DNA.
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Microbes that grow in low temperatures are called ___________________.
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Catalase breaks down ___________________ into water and oxygen.
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Halophile microorganisms require high ______ to grow
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Osmotolerant microorganisms can grow over a wide range of ______
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Xerophile microorganisms grow best at low ______
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Microbes survive in highly concentrated environments by using ______ solutes
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Examples of compatible solutes include potassium chloride, betaken, and some ______ acids
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Osmotolerant microorganisms, such as Staphylococcus, are ______ tolerant
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Cronobacter microorganisms thrive in ______ conditions
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Mannitol Salt Agar is used to select for ______-tolerant microorganisms
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What type of transport does not require energy and relies on a gradient from higher to lower concentrations?
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What is the primary function of active transport in microbes?
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What is the name of the primary active transport mechanism that uses ATP to move substances across the cell membrane?
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What is the key difference between primary and secondary active transport?
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What type of transport uses membrane carrier proteins to facilitate the movement of molecules across the cell membrane?
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What is the name of the process that involves the movement of molecules across the cell membrane without the use of energy?
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What is the term for the movement of molecules against their concentration gradient using energy from the proton gradient?
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What is the name of the process that involves the transport of molecules across the cell membrane coupled with a chemical reaction, such as group translocation?
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What is the main function of Uptake ABC transporters in bacterial cells?
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What is the primary mechanism of Multidrug Efflux pumps in bacterial cells?
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What is the energy source used in Secondary Active Transport?
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What is the role of the phosphotransferase system in bacterial cells?
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How do microbes acquire iron, a essential nutrient, from their environment?
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What is the difference between catabolism and anabolism in cellular metabolism?
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What is the primary function of siderophores in microbial cells?
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What is the importance of enzymes in cellular metabolism?
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How does an enzyme lower activation energy to increase the rate of reaction?
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In oxidation-reduction reactions, what is the direction of electron movement?
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What is the significance of redox reactions in metabolism?
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What is the definition of oxidation in the context of redox reactions?
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In redox reactions, what is the term for the substance that loses electrons?
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Rhizobium is in ______ with plants
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Azotobacter is ______ living in soil
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Passive transport does not require ______ energy
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Facilitated diffusion is a type of ______ transport
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ABC transporters are found in all ______ of life
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Food must enter the cell ______ membranes
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Active transport moves nutrients ______ the concentration gradient
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The more negative the ______ the better the donor.
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Half reactions are written as: Acceptor + #e -> ______.
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Couples with more negative ______ will donate e- to couples with more positive E0.
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The Electron Tower shows the ______ potential of various redox couples.
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Freely diffusible electron carriers include ______ and NADP+.
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Membrane-bound electron carriers include flavoproteins, cytochromes, and ______.
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The reduced forms of freely diffusible electron carriers, such as NADH and ______, are the reducing power of the cell.
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Membrane-bound electron carriers are important components of ______ Transport Chains.
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Metabolism involves ______ reactions and electron carriers.
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In ______ reactions, electrons move from donor to acceptor.
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Oxidation is the removal of ______, while reduction is the addition of ______.
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The substance oxidized is the ______, and the substance reduced is the ______.
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Oxidation-reduction reactions can result in ______ release, which can be used to form ATP.
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Redox reactions often involve the transfer of ______ and ______ (H atom, example: NAD+/NADH).
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Study Notes
Enzymes and Microbial Growth
- Enzymes catalyze chemical reactions, with Catalase being an example of an enzyme that breaks down hydrogen peroxide (H2O2) into water and oxygen.
- Superoxide dismutase (SOD) is another enzyme that converts superoxide ions into hydrogen peroxide and oxygen.
Microbial Growth Temperature
- Microbes can grow under a wide range of temperatures, including:
- Hyperthermophiles: 85-113°C (e.g. Thermus aquaticus, source of Taq Polymerase)
- Thermophiles: 45-85°C (e.g. Thermus aquaticus)
- Mesophiles: 20-45°C (e.g. Escherichia coli)
- Psychrophiles: 0-20°C (e.g. Chlamydomonas)
Microbial Adaptation to High Temperature
- High temperatures can disrupt membranes, denature proteins and DNA, but thermophiles adapt by:
- Using solutes to maintain cellular structure and function
- Producing heat-shock proteins to stabilize cellular components
Solute Concentration and Water Activity
- Microbes can grow under a wide range of solute concentrations, which affects water activity (aw)
- Halophiles require high salt concentrations to grow
- Osmotolerant microbes grow over a wide range of aw (e.g. Staphylococcus, salt tolerant)
- Xerophiles grow best at low aw (e.g. Cronobacter, grows in dry conditions)
Microbial Survival in Concentrated Environments
- Microbes survive in highly concentrated environments by using compatible solutes (e.g. potassium chloride, betaine, some amino acids)
Microbial Nutrition
- Microbes require a supply of raw materials and nutrients to obtain energy and construct new cellular components
- Nutrients are substances used in biosynthesis and energy release, and are required for growth
- 95% of the microbial cell dry weight is made up of a few major elements
Microbial Response to Stress
- Microbes respond to stress by:
- Stabilizing proteins through increased hydrogen and covalent bonds, and molecular chaperones
- Stabilizing DNA by synthesizing proteins to coat it
- Stabilizing membranes by using lipids with ether linkages instead of ester linkages
Types of Microbes
- Rhizobium: in symbiosis with plants
- Azotobacter: free-living in soil
Acquiring Nutrients
- Rapid growth of microbes presents challenges in acquiring nutrients
- Food must enter cells at high rates, across membranes, in a selective fashion, and often against a concentration gradient
- Passive and active transport systems are used to acquire nutrients
Passive Transport
- No energy required
- Requires a gradient from high to low concentrations
- Facilitated diffusion: uses membrane carrier proteins
- Passive diffusion: only for small molecules and certain gases
Active Transport
- Energy-dependent
- Moves nutrients against a concentration gradient
- Uses ATP or proton motive force
- Two types: primary and secondary
Primary Active Transport
- ATP-binding cassette (ABC) transporters
- Found in all domains of life
- Can move substances in or out of cells
- Uptake ABC transporters: move nutrients in
- Export ABC transporters: move substances out, also known as multidrug efflux pumps
Secondary Active Transport
- Uses potential energy of ion gradients
- Example: Lac permease
- Electron transport generates a proton gradient, which can be used to do work
Active Transport: Group Translocation
- Example: phosphotransferase system in bacteria
- Nutrient is chemically altered
- Energy from phosphoenolpyruvate attaches to sugars
- Phosphoenolpyruvate is a key intermediate in glycolysis
Iron Uptake
- Problem: little free iron available, often in insoluble form (ferric iron, Fe3+)
- Solution: microbes release siderophores to acquire Fe
- Siderophore-Fe complex is then transported into cells, often using ABC transporters
Introduction to Metabolism
- Metabolism: all chemical reactions in a cell
- Catabolism: breakdown of complex molecules into smaller ones with release of energy for anabolism
- Anabolism: reactions that build cells
Metabolism Requirements
- Metabolism requires a flow of energy (capacity to do work) and the participation of enzymes
- Enzymes increase local concentrations of substrate and orient substrates properly for reactions to proceed
Metabolism Involves Oxidation-Reduction (Redox) Reactions and Electron Carriers
- Electrons move from donor to acceptor
- Utilize carriers
- Redox reactions can result in energy release, which can be used to form ATP
Oxidation-Reduction Reactions
- Oxidation: removal of electrons
- Reduction: addition of electrons
- Substance oxidized is donor, substance reduced is acceptor (pair = redox couple)
- Often involve not just the transfer of electrons but also an electron and proton (H atom)
Reduction Potential (E0)
- Measures the tendency of a donor to lose electrons
- More negative E0 indicates a better donor, while more positive E0 indicates a better acceptor
Half Reactions and Redox Couples
- Half reactions are written as: Acceptor + #e -> Donor
- A redox couple (or pair) consists of an acceptor and a donor
- Couples with more negative E0 will donate electrons to couples with more positive E0
The Electron Tower
- The electron tower shows the energy released when electrons move from a donor to an acceptor
- The greater the difference in E0, the more energy is released
Electron Carriers in Redox Reactions
- Electron carriers can be divided into two classes: freely diffusible and membrane-bound
- Freely diffusible carriers, such as NAD+ and NADP+, are found in the cytoplasm and provide reducing power to the cell
- Membrane-bound carriers, such as flavoproteins, cytochromes, and quinones, are important components of electron transport chains
Acquiring Nutrients
- Rapid growth of microbes presents challenges in acquiring nutrients
- Nutrients must enter the cell at high rates, across membranes, in a selective fashion, and often against a concentration gradient
- Both passive and active transport systems are used to acquire nutrients
Passive Transport
- No energy is required for passive transport
- Passive transport requires a gradient from high to low concentration
- Examples of passive transport include passive diffusion and facilitated diffusion
Active Transport
- Energy is required for active transport
- Active transport moves nutrients against a concentration gradient
- ATP or proton motive force is used to drive active transport
- There are two types of active transport: primary and secondary
ABC Transporters
- ABC transporters are a type of primary active transport
- They use ATP to drive the transport of nutrients across the membrane
- ABC transporters are found in all domains of life and can move substances in or out of cells
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Description
This quiz explores the role of enzymes in catalytic reactions, including the actions of superoxide dismutase and catalase. Test your understanding of these biochemical processes.
