Exam 2 Review
With respect to their synthesis, how are amino acids typically grouped?
By structurally related families that share common biosynthesis pathways
True or false: There is a standard antimicrobial procedure available from the Centers for Disease Control and Prevention (CDC) that can be used for all different microorganisms under any condition.
False
_______ does not actually destroy microbes or inhibit their growth but instead removes them physically from samples.
Filtration
What happens to an organism if it lacks one or more enzymes in a given biosynthetic pathway?
It must have the end product provided from an external source.
Which of the following combinations of molecules is produced during the light-dependent reactions of photosynthesis and used in the light-independent reactions?
NADPH and ATP
Which of the following use moist heat to destroy microbes?
Pressurized steam Pasteurization Boiling
What enzyme binds to a DNA promoter region to initiate transcription?
RNA polymerase
Consider the use of low temperature storage for the preservation of food. Which of the following are accurate statements?
Refrigeration inhibits the growth of many pathogens and spoilage microorganisms by slowing or stopping critical enzyme reactions. Psychrotrophic and some psychrophilic microorganisms can grow at refrigeration temperatures.
Which of the following are true statements about what happens to glucose inside a cell?
Some glucose might enter glycolysis, only to be siphoned off as a precursor metabolite for biosynthesis. Glucose can be used in catabolism to yield energy, or 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.
______ destroy all microbes, including viruses and endospores.
Sterilants
Consider the figure showing the relationship between catabolism and anabolism. Which side shows catabolism, and which side shows anabolism?
The left side shows catabolism, and the right side shows anabolism.
A sterile object is free of ______.
all viable microorganisms and viruses
The figure illustrates a type of regulation used by cells to rapidly control certain key enzymes. The arrow labeled "1" points to the site, and the arrow labeled "2" points to the site.
allosteric active
The process by which chemolithoautotrophs and photoautotrophs incorporate CO2 into organic compounds is called
carbon fixation
High pressure (130,000 psi) is thought to kill microbes by altering their ______.
cell membranes proteins
In general, the chromosome of a bacterial cell is a _______ DNA molecule that is replicated _______.
circular; bidirectionally from one origin of replication
Enzymes involved in essential metabolic pathways, such as glycolysis, are usually ______.
constitutive
Consider the effect of temperature on enzyme activity. If the temperature is too high, proteins will _____ and no longer function.
denature
Radio waves, X-rays, microwaves, UV light and gamma rays are all examples of ______.
electromagnetic radiation
The most highly resistant microbial structure is the bacterial
endospore
Hydrogen sulfide is produced as a result of certain types of anaerobic respiration. Some chemolithotrophs can then use this as a/an ______.
energy source
Choosing the correct antimicrobial procedure depends on many factors including ______.
environmental conditions composition of item type and number of microbes
All of the following accurately describe enzymes EXCEPT ______.
enzymes provide energy to help reactions proceed more rapidly
The straining of a fluid or air through a membrane to trap microorganisms is known as
filtration
Fats, the most common simple lipids, are broken down by lipases into their component ______.
glycerol and fatty acids
Match the examples given to the type of method used to control microbial growth. Instructions
heat treatment, filtration, irradiation = physical method of control antimicrobial chemical = chemical method of control
Disinfectants that destroy all viruses and vegetative organisms but not endospores are referred to as ______-level disinfectants.
high
Eukaryotic cells can regulate the levels of mRNA by destroying specific RNA transcripts through a process known as RNA _____
interference
Although generally less reliable than heat, germicidal chemicals are especially useful for treating ______.
large surfaces heat-sensitive items
Microorganisms that are free living are ______ to chemical disinfectants than microorganisms in a biofilm.
less resistant
Soap generally does not destroy most microbes, but it aids in their ______.
mechanical removal
Washing hands with plain soap and water works by ______ removing microbes.
mechanically
The electron transport chain is a cluster of membrane-embedded electron carriers that accept electrons from the coenzymes _______ and _______ and then pass these electrons along the chain.
nadh fadh2
A long stretch of DNA that potentially codes for a protein is called a(n)
open reading frame
The mechanism by which cellular respiration uses reducing power generated in glycolysis, the transition step, and the TCA cycle to synthesize ATP is ______ phosphorylation
oxidative
When selecting an appropriate chemical disinfectant, it is important to realize that the death rate is significantly influenced by ______.
pH temperature
Heat treatment, irradiation and filtration are examples of ______ used to control microorganisms.
physical processes
A high-solute environment damages microbial cells by causing ______.
plasmolysis
When boiling or pasteurizing a sample, microorganisms are destroyed because their ______.
proteins are irreversibly denatured
RNA contains the sugar _____, which differs from its DNA counterpart by possessing _____ oxygen atom.
ribose; one more
The main effect of low temperature storage is to ______.
slow the activity of microbes
Following treatment to remove all viable microorganisms, including viruses, an object is considered to be
sterilization
As part of cellular respiration, a membrane-bound enzyme called ATP _______ uses energy from a proton-motive force to add a phosphate group to ADP.
synthase
The number of cells in a culture will most influence the ______ necessary to kill them.
time
Alternative sigma factors allow cells to directly control ______.
transcription
is the process of decoding the information carried by mRNA to synthesize a protein.
translation
Identify each of the following by the most precise descriptive term as either a cofactor or coenzyme: magnesium: ______ ; NADP+: ____ ; zinc: ______
cofactor coenzyme cofactor
A surgical scalpel is rated as a ______ instrument because it penetrates skin and mucous membranes and therefore must be sterile.
critical
A common dry heat sterilization method used in the microbiology laboratory is ______.
flaming the inoculating loop
A ______ is a sequence of nucleotides that usually codes for one functional protein.
gene
The series of sequential chemical reactions in a cell that converts a starting compound to an end product is called a _____ pathway
metabolic
The analysis of the total microbial genomes in an environment is a field known as _____
metagenomics
The enzymes of the tricarboxylic acid cycle are found in the ______ matrix in eukaryotes and in the in _____ prokaryotes.
mitochondrial cytoplasm
A concentrated culture of cells will take ____ time to kill than a dilute culture of the same organism.
more or longer
Eukaryotic mRNA is first synthesized as an immature transcript called ___-_____. It has to be processed significantly before it forms mature mRNA.
pre mrna
The act of delaying spoilage is ______.
preservation
High- processing (HPP) is used to decrease the number of microbes in food while maintaining the color and flavor.
pressure
Information is passed from the environment into the cell by a process known as signal ___
transduction
True or false: The risk of developing a fatal infection after surgery has substantially decreased since the late 19th century because modern hospitals now have procedures in place to avoid microbial contamination.
true
All DNA nucleotides contain the same deoxyribose and phosphate group, but different
bases
A new field has emerged which employs the power of computers to store, retrieve, and analyze DNA sequence data called ______.
bioinformatics
Although the pentose phosphate pathway is used by cells to break down glucose, it is particularly important because of its contribution to ______.
biosynthesis
In addition to yielding energy, catabolic pathways generate carbon intermediates that can be used in anabolic pathways for the biosynthesis of macromolecules. These carbon skeletons are called
precursor metabolites
All of the following are examples of means by which microorganisms can respond to changing environmental conditions EXCEPT ______.
production of different ribosomes
Medical instruments are classified into three categories according to their risk for transmitting pathogens. These are: critical instruments, ______ instruments, and _____ instruments.
semicritical noncritical
All of the following are examples of electromagnetic radiation EXCEPT ______.
sound waves
True or false: Choosing which germicide to use is not that complicated since we only consider how effective it is against the target microbes.
false
True or false: The Calvin cycle is a two-step linear pathway that photosynthetic organisms use to fix carbon dioxide
false
How do aqueous solutions of alcohol usually affect microbes?
by damaging lipid membranes by denaturing proteins
Controlling microbial growth is important in which of the following scenarios?
-Caring for an open wound -Manufacturing of food products -Preparing a patient for surgery
If the theoretical maximum ATP yield in prokaryotes from oxidative phosphorylation is 34 ATP for a single glucose molecule, what is the total ATP gain when substrate-level phosphorylation is included?
38 ATP
If both glucose and lactose are present in a medium, why is the lac operon not transcribed?
Cells preferentially use glucose and only use lactose if the glucose is depleted.
Match the type of enzyme inhibition on the left with the example of an inhibitor on the right.
Competitive inhibition = Sulfa drugs Non-competitive inhibition by regulatory molecules = Allosteric regulators Non-competitive inhibition by enzyme poisons = Mercury
The molecule that encodes all the instructions needed to produce a cell's components is ______.
DNA
What is the active site of an enzyme?
The critical site to which a substrate binds by weak forces.
What is one disadvantage of using heat treatment to sterilize plastic items?
The items may melt.
Microorganisms can grow on 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.
Which of the following are reasons an organism might use fermentation?
They lack an electron transport chain. A suitable inorganic terminal electron acceptor is not available.
For each six-carbon molecule of glucose that enters glycolysis, how many molecules of pyruvate are made, and how many carbon atoms does each pyruvate have?
Two molecules of pyruvate, each with three carbon atoms.
Proteins are hydrolyzed by proteases, enzymes that break the peptide bonds between ____ ____ subunits
amino acid
Aqueous solutions of alcohol at a concentration of ______ are more effective than 100% alcohol.
60-80%
Considering the general equation that describes photosynthesis, the rate of the process would be most influenced by the availability of _______ in the atmosphere.
CO2
In order to form lipids, how are fatty acids and glycerol synthesized?
Fatty acid chains are assembled from 2-carbon acetyl groups from the transition step; the precursor to glycerol comes from glycolysis.
_______ is a physical means used for destroying or removing microorganisms.
Filtration
Which of the following are physical ways to remove or destroy microbes?
Filtration Incineration Autoclaving Ultraviolet radiation
______ provides an alternative to heat for sterilization and disinfection, but the process damages some types of plastics.
Irradiation
Some microorganisms can alter characteristics of certain surface proteins, allowing them to avoid detection by the host's immune system. This phenomenon is called ______.
antigenic variation
It is often difficult to choose which germicide to use because often the most effective options ______.
are not the safest
Germicidal chemicals ______.
are often poorly understood with regards to mechanisms of action usually react irreversibly with proteins, DNA, cytoplasmic membranes, or viral envelopes
Nucleotide subunits of DNA and RNA are composed of three units: a 5-carbon sugar, a phosphate group, and a nucleobase. They are initially synthesized ______.
as ribonucleotides that can be converted to deoxyribonucleotides by replacing the 2' hydroxyl group with a hydrogen atom
Which four of the following microbial groups are the most resistant to chemical control methods?
bacterial endospores nonenveloped viruses Mycobacterium species protozoan cysts and oocysts
Why is regulation of gene expression important?
A cell does not need all of its encoded proteins at the same time.
In photosynthesis, what do the light reactions, or light-dependent reactions, accomplish?
They capture radiant energy and convert it to chemical energy in the form of ATP.
Microorganisms that can grow on polysaccharides and disaccharides first break these down to glucose or precursor metabolites that can then enter into the pathway of _____ to be oxidized
glycolysis
Adding sorbic, propionic, and benzoic acid to foods affects ______ of microbes.
cell membrane function
Adding preservatives such as benzoic acid to food is important because ______.
it inhibits growth of many bacteria and mold
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 as part of which of the following?
cellular respiration fermentation
Salting and drying decrease the availability of water in food, resulting in an environment that is ______ relative to microbes, thereby preventing their growth.
hypertonic
Chemicals called ______ are used to prevent the growth of undesirable organisms in foods and beverages.
preservatives or additives
