VBS 2032: CH 6 LearnSmart
Fermentation
A cell has only a limited number of electron carrier molecules. During glycolysis, if electrons are not removed from NADH, the cell soon runs out of available NAD+, and the breakdown of glucose ends. This presents a problem for cells that lack a suitable terminal electron acceptor for the electron transport chain or that cannot respire. The solution to this problem is called:
More than a thousand
A cell will usually contain about how many different enzymes?
Consider a cell converting glucose into CO2 and water with the release of energy. This is an example of what type of metabolism, and the reactions themselves are considered to be what?
Catabolism; exergonic
denature
Consider the effects of temperature on enzyme activity. If the temperature is too high, proteins will _______ and no longer function.
oxidized; reduced
Each type of the major electron carriers is referred to by two different abbreviations (NAD+/NADH, NADP+/NADPH, and FAD/FADH2). The first of each pair refers to the ____ form and the second of each pair refers to the _______ form.
donor; acceptor
In the figure, compound X donates electrons to compound Y. Therefore, compound X is the electron ________ and compound Y is the electron ___________. - X is oxidized by the reaction, and Y is reduced by the reaction
Model for eukaryotic cells
Metabolic pathways of organism such as E. Coli
Identifying markers
Products characteristic of specific microbes
oxidation
The TCA cycle completes the __________ of glucose
Photophosphorylation
The sun's radiant energy and an electron transport chain create a proton motive force that drives the addition of Pi to ADP
glycolysis; pentose phosphate; Krebs
The three central metabolic pathways that gradually oxidize glucose to CO2 are ____________, the ____________ pathway, and the ____________ cycle.
Microorganisms can grow a variety of organic compounds other than glucose, including polysaccharides, proteins, and lipids. How do they accomplish this?
They break these macromolecules down into appropriate precursor metabolites that are then introduced into central metabolism or used in biosynthesis
Competitive inhibition
sulfa drugs
Tricarboxylic acid cycle (TCA cycle)
Oxidizes an acetyl group to release two molecules of CO2; generates some ATP and precursor molecules and the most reducing power of all the central metabolic pathways
lipids, carbohydrates, proteins, and nucleic acids
Consider the picture representing metabolism in E. Coli growing in a medium that contains only glucose and a few inorganic salts. The four outputs to the sides represent different anabolic pathways involved in the biosynthesis of 4 types of biological macromolecules necessary for cellular structures. These four biological macromolecules are:
substrate; product
Enzyme function as biological catalysts, accelerating the conversion of one substance, the ________, into another, the _______
All the following accurately describe enzymes EXCEPT:
Enzymes provide energy to help reactions proceed more rapidly
Non-competitive inhibition by regulatory molecules
allosteric regulators
non-competitive inhibition by enzyme poisons
mercury
2 ATP are generated
During the transition step of central metabolism, all of the following occur EXCEPT:
Which of the following correctly describe some of the forms of energy represented in this photograph?
- Electrical energy generated by the hydroelectric dam as it captures the energy from moving water. - Potential energy of the water behind the dam - Kinetic energy of the photons that make up sunlight
Substrate-level phosphorylation
Energy released in an exergonic reaction is used to power the addition of Pi to ADP
True
T or F: Change in free energy for a give reaction is the same regardless of the number of steps involved
False
T or F: The sole function of glucose for cells growing in a glucose-salts medium is as an energy source
Which of the three central metabolic pathways generate a modest amount of ATP via substrate-level phosphorylation?
TCA cycle and glycolysis
Glycolysis
Splits glucose and gradually oxidizes it to two molecules of pyruvate; generates some ATP and reducing power plus six precursor metabolites
Free energy is best defined as
the energy available to do work
Oxidative phosphorylation
Energy from exergonic reactions is used to create a proton motive force that drives the addtion of Pi to ADP
Which of the following are true statements about what happens to glucose inside a cell?
- Glucose can be used in catabolism to yield energy, to the precursor metabolites generated from its breakdown can be used in anabolism - Some glucose might be oxidized to CO2, generating the maximum amount of ATP - Some glucose might enter glycolysis, only to be siphoned off as a precursor metabolite for biosynthesis
Which of the following accurately describe fermentation?
- NAD+ is regenerated from NADH by the transfer of electrons to pyruvate or a derivative - Glucose is broken down via glycolysis - Fermentation does not involve the tricarboxylic acid (TCA) cycle
In addition to glucose, which of the following organic compounds can serve as energy sources for microbes?
- Polysacchardies - Proteins - Fatty acids - Disaccharides - Lipids - Monosaccharides
Recall the E. Coli. can grow in glucose-salts medium, which contains only glucose and a few inorganic salts. This means the glucose is serving what 2 purposes in the cell?
- Starting point from which all cell components are made - Energy source
What are the two fundamental tasks that all cells must accomplish to grow?
- Synthesize new parts - Harvest energy to power reactions
Which of the following explain why a cell might undergo fermenation?
- The cell has a limited number of electron carrier molecules that must be regenerated for glycolysis to continue - The cell might lack the pathways for respiration, so fermenation might be the only option - The cell might not have the appropriate terminal electron acceptor available for respiration
Oxidative phosphorylation, the mechanism by which cellular respiration uses the NADH and FADH, genereated in glycolysis, the transition step, and the TCA cycle to synthesize ATP, involves what two steps?
- The electron transport chain generates a proton motive force - ATP synthase uses the energy of the proton motive force to drive the synthesis of ATP
Which of the following are true about glycolysis?
- The pathway splits glucose and oxidizes it to form two molecules of pyruvate - The pathway provides the cell with a small amount of ATP, some reducing power, and six precursor metabolites
In contrast to an endergonic reaction, which of the following accurately describe an exergonic reaction?
- The reaction releases energy as it proceeds - The starting compounds have more free energy than the products
Which of the following correctly describe the transition step and the tricarboxylic acid (TCA) cycle?
- The transition step converts the pyruvate from glycolysis into acetyl-CoA - The TCA cycle oxidizes a 2-carbon acetyl group to release two molecules of CO2 - Together they generate the most reducing power of all the central metabolic pathways
Consider two different processes for converting glucose to CO2 and water. In the first, the glucose is burned (literally, as in a fire); in the second, the glucose is converted in a series of multiple steps in a cell. Which of the following statements correctly describes the free energy in these two approaches?
The changes in free energy is the same regardless of the number of steps involved
active site
The critical site of an enzyme to which a substrate binds by weak forces is called
Targets of antimicrobial drugs
Metabolic processes unique to prokaryotes
Which of the following correctly describe respiration?
- Electrons extracted from glucose are transferred to the electron transport chain - The electron transport chain uses the electrons to generate a proton motive force that can be used to generate ATP
Cellular respiration; Fermentation
Glucose catabolism encompasses two key processes: (1) oxidizing glucose molecules to generate ATP, reducing power, and precursor metabolites; and (2) transferring the electrons carried by NADH and FADH2 to the terminal electron acceptor. The second process, transfer of electrons, is accomplished by which of the following?
In order for cells to obtain energy, they remove electrons from an energy source and ultimately donate them to the terminal electron acceptor. What does this tell us about the electron affinity of the energy source and the terminal electron acceptor?
The energy source has a lower affinity for electrons, and the terminal electron acceptor has a higher affinity for electrons
ATP
The main energy currency of cells is
glycolysis
The primary pathway used by many organisms to convert glucose to pyruvate is
Comparing the 2 drawings showing an interaction between a substrate and an enzyme, identify the substrate, the enzyme-substrate complex, the enzyme, and the active site of the enzyme.
1 = enzyme 2 = substrate 3 = active site 4= enzyme-substrate complex
Consider the figure showing the formation and breakdown of ATP. Fill in the labels of the figure by matching the terms with their correct number
1. ATP 2. Energy released drives anabolic reactions 3. ADP 4. Energy used comes from catabolic reactions
Place the following steps in correct order to show how the spatial arrangement of electron carriers in a bacterial electron transport chain helps explain how protons are shuttled from one side of the membrane to the other.
1. An electron carrier (NADH + H+) donates electrons to a hydrogen carrier, which also picks up protons 2. The hydrogen carrier passes electrons to a carrier that only accepts electrons 3. Because the electron carrier only accepts electrons, the protons are released to the outside of the cell 4. A proton motive force is set up as protons are moved from the inside of the cell to the outside
Consider the illustration of a metabolic pathway. Match the labels with their appropriate locations. Assume a sequential order of letters, i.e., enzyme a would come before enzyme b
1. Starting compounds 2. Enzyme a 3. Intermediate a 4. Enzyme b 5. Intermediate b 6. Enzyme c 7. End product
Rank the following energy-generating processes form greatest energy yield at the top to least energy yield at the bottom
1. aerobic respiration 2. anaerobic respiration 3. fermentation
Electronegative
An atom that has a greater affinity (attraction) for electrons than another is described as more _______ than the other.
Pentose phosphate pathway
Breaks down glucose, although primary role is production of NADPH and two precursor metabolites for use in biosynthesis
oxygen
In aerobic respiration, ______ serves as the terminal electron acceptor
Cheese
Metabolic wastes of Lactococcus and Lactobacllius species contributing to flavor and texture
Catabolism
The set of chemical reactions that degrade compounds, releasing their energy
Anabolism
The set of chemical reactions that synthesize and assemble the subunits of macromolecules
Transition
The step that links glycolysis to the TCA cycle is called the _________ step
Metabolism
The sum total of chemical reactions in a cell
Other than generating some ATP via the substrate-level phosphorylation steps of glycolysis, what critical role do the additional steps of fermentation accomplish?
They consume excess reducing power in order to regenerate NAD+ so that it can accept electrons to keep glycolysis going
Certain intermediates of catabolic pathways, called precursor metabolites are important because:
they serve as carbon skeletons from which subunits of macromolecules can be made
Oxidative phosphorylation and photophosphorylation are similar in that both processes:
use an electron transport chain to set up a proton motive force used to generate ATP
Most chemoorganotrophs, like the one shown in the figure, depend on the metabolic activities of photosynthetic organisms. Consider the forms of energy represented in the figure, and match each type of energy with the correct description
Kinetic energy = Photons of sunlight Chemical energy = Organic compounds
Biofuels
Microbial breakdown of corn stalks, sugar cane, or wood into ethanol
Which of the following best describes the conversion of energy from one form to another illustrated in the picture?
The potential energy of water stored behind the dam is converted to kinetic energy of moving water, which is converted to electrical current.
metabolic
The series of sequential chemical reactions in a cell that converts a starting compound to an end product is called a ____ pathway
When a cell processes glucose or other organic molecules through its central metabolic pathways, it does so to generate what 3 critical things?
- ATP, reducing power, precursor metabolites
