Chapter 6 Flashcards
Edward Buchner
- German chemist
- Showed that crushed yeast cells could convert sugar to ethanol and CO2
Two fundamental tasks microbial cells need to accomplish to grow:
- They must continually synthesize new parts- such as cell walls, membranes, ribosomes, and nucleic acids.
- Cells need to harvest energy and convert it to a form that can power the various energy- consuming reactions, including those used to make new parts.
Metabolism
The sum of all chemical reactions in a cell.
Involves processes that transform energy; cells take energy of one form and convert it into another.
Biofuels
Fuels made from renewable biological sources such as plants and organic wastes.
Cheesemakers add ______and ____ species to milk. Also, what do they do?
Cheesemakers add Lactococcus and Lactobacillus species to milk because the metabolic wastes of these bacteria contribute to the flavor and texture of various cheeses.
Bakers, brewers, Vintners and distillers use the yeast ____________. What does it do?
Bakers, brewers, vintners and distillers use the yeast Saccharomyces cereviseae to make bread, beer, wine and distilled spirits.
Why is microbial metabolism medically relevant?
Microbial metabolism is also medically relevant because reactions unique to bacteria are potential targets for antimicrobial medications.
Metabolism can be separated into what two components:
- Catabolism
- Anabolism
Catabolism
Is the set of chemical reactions that degrade compounds, releasing their energy.
Cells capture that energy and use it to make ATP
ATP
The energy currency of the cell
Anabolism
AKA biosynthesis
Is the set of chemical reactions that cells use to synthesize and assemble the subunits of macromolecules, using ATP for energy.
What is Anabolism also known as
Biosynthesis
What are the subunits of macromolecules
- amino acids
- nucleotides
- monosaccharides
- fatty acids
What is ATP made during catabolism used for:
Anabolism
Precursor metabolites
Some of the compounds produced during catabolism
Precursor metabolites
Some of the compounds produced during catabolism
They are chemicals that link catabolic and anabolic processes. They can either be broken down to generate energy in the form of ATP (via catabolism) or used to make certain subunits of macromolecules (anabolism)
Energy
Is the capacity to do work
What forms does energy exist as:
- Potential energy
- Kinetic energy
Potential energy
Is stored energy
What are some various forms potential energy can be stored
- chemical bonds
- a rock on a hill
- water behind a dam
What are some various forms potential energy can be stored in
- chemical bonds
- a rock on a hill
- water behind a dam
Photosynthetic organisms
Harvest the energy of sunlight, using it to power the synthesis of organic compounds from CO2.
By doing so, they convert the kinetic energy of photons to the potential energy of chemical bonds.
Photons
Particles that travel at the speed of light.
Chemoorganotrophs
Obtain energy by degrading organic compounds; they then use some of that energy to make other organic compounds.
They take potential energy of certain chemical bonds and use it to create other ones.
Chemoorganotrophs rely on the metabolic activities of what organisms?
Because chemoorganotrophs depend on a constant source of organic compounds, they generally rely on the metabolic activities of photosynthetic organisms.
Free energy
The energy available to do work
Free energy (from a biological perspective)
This is the energy released when a chemical bond is broken.
In what scenario is energy released?
If starting compounds have more free energy than the products, energy is released.
Exergonic reaction
If the starting compounds have more free energy than the products, energy is released. This is called exergonic reaction.
Endergonic reactions
If the products have more free energy than the starting compounds, the reaction requires an input of energy and is endergonic.
How does the number of steps in a given reaction affect the amount of free energy
The change in free energy for a given reaction is the same regardless of the number of steps involved.
Ex; converting glucose to CO2 and water in a single step releases the same amount of energy as degrading it in a series of steps.
Metabolic pathway
Series of sequential chemical reactions that are a part of metabolism.
The series of chemical reactions that convert a starting compound to an end product.
Types of metabolic pathways
- Linear
- Branched
- Cyclical
Essential components of metabolic pathways
- Enzymes
- ATP
- The chemical energy source
- Terminal Electron acceptor
- Electron carriers
Enzyme
Is a molecule (usually a protein) that functions as a biological catalyst, speeding up the conversion of one substance, the substrate, into another, the product.
Substrate
- Substance on which an enzyme acts to form products.
- Surface on which an organism will grow.
How do reactions occur without enzymes
Without enzymes, energy yielding reactions would still occur, but at rates so slow they would be insignificant.
How does an enzyme work in a chemical reaction?
An enzyme catalyzes a chemical reaction by lowering the activation energy.
Activation energy
Initial energy required to break a chemical bond.
The energy it takes to start a reaction.
What does ATP stand for
Adenosine triphosphate
What is ATP composed of:
The molecule is composed of ribose, adenine, and three phosphate groups arranged in a row.
ATP
Is the main energy currency of cells, serving as the ready and immediate donor of free energy.
Hydrolysis of the bonds between its phosphate groups can be used to power endergonic (energy consuming) reactions.
How do cell produce “energy currency” or ATP?
Cells produce energy currency by using energy to add a phosphate group to ADP forming ATP.
What does ADP stand for?
Adenosine diphosphate
ADP
Molecule that accepts an inorganic phosphate generating ATP.
How is the energy currency spent?
That energy currency is spent by removing the phosphate group, thereby releasing energy and converting the molecule back to ADP.
When do cells produce ATP?
Cells constantly produce ATP during exergonic reactions of catabolism and the use it to power endergonic reactions.
What kind of reactions are ATP used for?
Cells use ATP to power endergonic reactions.
Chemoorganotrophs use two different processes to make ATP:
- Substrate level phosphorylation
- Oxidative phosphorylation
Substrate level phosphorylation
Synthesis of ATP using energy released in an exergonic (energy-releasing) chemical reaction during the breakdown of the energy source.
Oxidative phosphorylation
The energy of a proton motive force drives the addition of phosphate to ADP; the reaction is catalyzed by an enzyme called ATP synthase.
Proton motive force
Is the form of energy that results from the electrochemical gradient established by electron transport chain.
From of energy generated as an electron transport chain moves protons across a membrane to create a chemiosmotic gradient.
How do photosynthetic organisms generate ATP
Photophosphorylation
Photophosphorylation
Similar to oxidative phosphorylation
Synthesis of ATP using the energy of proton motive force created by harvesting radiant energy.
How do cells obtain energy used to make ATP?
Cells remove electrons from glucose or another low electron affinity chemical, and donate them to a molecule such as O2 that has a higher affinity.
Energy source
the chemical that serves as the electron donor
Compound that a cell oxidized to harvest energy; also called an electron donor.
Terminal electron acceptor
Chemical that is ultimately reduced as a consequence of fermentation or respiration.
Chemical that ultimately accepts electrons
How do cells remove electrons from the energy source
Cells remove electrons from the energy source through a series of oxidation reduction reactions or redox reactions.
Oxidation reduction reactions
Chemical reactions in which one or more electrons are transferred from one molecule, atom or ion to another; one substance in the reaction becomes oxidized.
Oxidized
Refers to loss of electrons
What occurs during redox reaction
The substance that loses electrons is oxidized by the reaction; the one that gains electrons is reduced.
What occurs during redox reaction
The substance that loses electrons is oxidized by the reaction; the one that gains electrons is reduced.
Reduced
Refers to the gain of electrons
Dehydrogenation
The removal of a hydrogen
Is an oxidation
Hydrogenation
The addition of a hydrogen atom
Is a reduction
How can the relative amount of energy to be gained by oxidizing be predicted?
The relative amount of energy to be gained by oxidizing a particular energy source can be predicted by considering the electron affinities of both the energy source and the terminal electron acceptor; the greater the difference in affinities, the more energy released.
How can the relative amount of energy to be gained by oxidizing be predicted?
The relative amount of energy to be gained by oxidizing a particular energy source can be predicted by considering the electron affinities of both the energy source and the terminal electron acceptor; the greater the difference in affinities, the more energy released.
Electron carriers
Molecules cells use to shuttle electrons; they readily accept and then donate electrons
Three types of electron carriers:
- NAD+/NADH
- NADP+/NADPH
- FAD/FADH2
What do reduced electron carriers represent
Reducing power
Why do reduced electron carriers represent reducing power?
Because they can easily transfer their electrons to another chemical that has a higher affinity for electrons.
By doing so, they not only reduce the recipient molecule, they also raise its energy level.
Precursor metabolites
Serve as carbon skeletons from which subunits of macromolecules can be made.
They are metabolic intermediates that can be either used to make the subunits of macromolecules or oxidized to generate ATP
Precursor metabolite pyruvate can be converted to what three amino acids?
- Alanine
- Leucine
- Valine
What is the referred energy source of many cells
Glucose
What two purposes does glucose serve when E.coli grows in glucose salts medium
- Glucose is the energy source
- The starting point from which all cell components are made-including protein, lipids, carbohydrates and nucleic acids
What happens when E.coli cells degrade glucose molecules
When E.coli cells degrade glucose molecules , the pathways they use release energy and also form a dozen or so precursor metabolites.
What two things can happen to precursor metabolites made in catabolism?
- Can be further oxidized to release energy
- It can be used in biosynthesis.
What is the preferred energy source of many cells?
Catabolizing of glucose
Two key sets of processes for catabolism of glucose
- Oxidizing glucose molecules or generate ATP, reducing power (NADH,FADH2, and NADPH), and precursor metabolites
- Transferring the electrons carried by NADH and FADH2 to the terminal electron acceptor, which occurs as part of cellular respiration or fermentation.
What are the three key metabolic pathways called together?
Central metabolic pathways
What do the central metabolic pathways DO together?
The three key metabolic pathways they central metabolic pathways together oxidize glucose to CO2, as described by the equation
Glucose + 6O2 —> 6CO2 + 6 H20
Are the central metabolic pathways catabolic or anabolic
The pathways are catabolic, but the precursor metabolites and reducing power they generate can also be diverted for use in biosynthesis.
Because central metabolic pathways can have dual roles what are they also known as
Amphobolic pathways
What are the three central metabolic pathways include:
- Glycolysis
- Pentose phosphate pathway
- Tricarboxylic acid (TCA) cycle
Glycolysis
Splits glucose and gradually oxidizes it to form two molecules of pyruvate.
Provides the cell with a small amount of energy in the form of ATP, some reducing power, some reducing power, and six precursor metabolites.
Some microbial cells use an alternative series of reactions (Entner-Doudoroff pathway) that generates a slightly different set of intermediates and end products.
What does Glycolysis provide the cell with:
Provides the cell with:
- a small amount of energy in the form of ATP
- some reducing power
- six precursor metabolites
Instead of glycolysis, some cells use an alternative series of reactions called:
Entner-Doudoroff pathway is a pathway
Pentose phosphate pathway
Also breaks down glucose
Its primary role is to produce compounds used in biosynthesis, including two precursor metabolites as well as reducing power in the form of NADPH.
A product of the pathway feeds into glycolysis
Tricarboxylic acid (TCA) cycle is also known as:
Citric Acid Cycle
Krebs Cycle
What occur just before the TCA cycle?
A single reaction called the transition step converts the pyruvate from glycolysis into acetyl-CoA. One molecule of CO2 is released as a result.
TCA cycle
TCA cycle accepts the 2-Carbon acetyl group from the transition step, ultimately oxidizing it to release two molecules of Co2.
Of all the central metabolic pathways, which steps produced the most reducing power
Transition step coupled with the TCA cycle together generate the most reducing power of all the central metabolic pathways; they also produce three precursor metabolites and ATP.
What can the reducing power accumulated during the oxidative steps be used for?
In cellular respiration to generate ATP by oxidative phosphorylation.
Cellular respiration
Involves transferring the electrons taken from glucose to the electron transport chain (ETC), which ultimately donates them to a terminal electron acceptor.
Electron transport chain
- The ETC uses the electrons to generate a proton motive force- a form of energy cells use to make ATP by oxidative phosphorylation.
Proton Motive Force
- a form of energy cells use to make ATP by oxidative phosphorylation
Aerobic respiration
- O2 serves as the terminal electron acceptor.
Anaerobic respiration
Uses a molecule other than O2 as a terminal electron acceptor.
Fermentation
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How are enzymes named?
The name of an enzyme usually reflects its function and ends with the suffix -ase.
Active site
Site on an enzyme to which the substrate binds; also known as the catalytic site
What happens when the substrate binds to the active site of enzyme?
The binding of the substrate to the active site causes the shape of the flexible enzyme to change slightly. This mutual interaction, or induced fit, results in a temporary intermediate called an enzyme-substrate complex.
Enyzme-Substrate Complex
when the substrate binds to the active site causing the shape of the enzyme to change slightly. This results in a temporary intermediate called an enzyme substrate complex.
Mechanism of Enzyme Action
- The substrate is held within the enzyme-substrate complex in a specific orientation so that existing bonds are destabilized, and new ones can easily form, lowering the activation energy of the reaction.
- The products are then released, leaving the enzyme unchanged and free to combine with new substrate molecules.
