Chapter 5 Flashcards
Plant cell walls consist mainly of _____.
cellulose
Cellulose is a
polysaccharide that is a major component of the tough walls that enclose plant cells.
The characteristic that all lipids have in common is that _____.
none of them dissolves in water.
Almost all the covalent bonds in lipids are nonpolar, causing their
solubility in water to be extremely low.
Lipids are
hydrophobic substances.
Palm oil and coconut oil are more like animal fats than are other plant oils. Because they _____ than other plant oils, they may contribute to cardiovascular disease.
contain fewer double bonds
Evidence suggests that a diet high in saturated fats may contribute to
human cardiovascular disease.
Some regions of a polypeptide may coil or fold back on themselves. This is called _____, and the coils or folds are held in place by _____.
secondary structure … covalent bonds
Secondary structure is the
localized folding and/or coiling of the primary structure of a polypeptide. It results from hydrogen bonding between atoms of the polypeptide backbone.
A dehydration reaction (or condensation reaction) is the process in which _____.
water molecules are produced as a polymer is formed from monomers
Monomers are joined together in a
reaction in which two molecules are covalently bonded to each other through the loss of a water molecule; this is called a condensation reaction or, specifically, a dehydration reaction.
A hydrophobic amino acid R group (side group) would be found where in a protein?
on the inside of the folded chain, away from water
Hydrophobic R groups are
nonpolar. By orienting within the folded chain they associate with other nonpolar R groups or side chains and avoid coming into contact with water.
Sucrose is formed when glucose is joined to fructose by a(n) _____.
glycosidic linkage
Glycosidic linkages join
simple sugars to form polysaccharides.
The flow of genetic information in a cell goes from _____.
DNA to RNA to protein
The information in DNA is transcribed into
RNA and then translated into protein.
The building blocks or monomers of nucleic acid molecules are called _____.
nucleotides
A nucleotide is a
nucleic acid monomer consisting of a nitrogen base, a pentose sugar, and a phosphate group.
Nucleotides joined together by covalent bonds are called
phosphodiester linkages and form nucleic acid molecules.
The four main categories of large biological molecules present in living systems are _____.
proteins, nucleic acids, polysaccharides, and lipids
CHECK AND MAKE SURE THIS IS RIGHT??)
Which polymers are composed of amino acids?
Proteins
Proteins are composed of
amino acids joined together.
Which of the following are attached to the central carbon atom in an amino acid?
A carboxyl functional group,
A side chain (“R group”)
and An amino functional group
Which is not attached to the central carbon atom in an amino acid?
An oxygen
The central carbon atom in an amino acid is bonded to
an amino functional group, a carboxyl functional group, a side chain, and hydrogen.
Which part of an amino acid is always acidic?
Carboxyl functional group
The carboxyl group (COOH) contains two oxygen atoms that tend to pull electrons away from the hydrogen atom, so
this group tends to lose a proton and is acidic.
Which monomers make up RNA?
Nucleotides
Nucleotide monomers make up
nucleic acids.
Which of the following statements about the formation of polypeptides from amino acids is true?
A bond forms between the carboxyl functional group of one amino acid and the amino functional group of the other amino acid.
A hydroxyl group is removed from the carboxyl group of one amino acid and hydrogen is removed from the amino group of the other amino acid, allowing
a bond to form between the two groups.
Enzymes in the digestive tract catalyze
hydrolysis reactions.
Enzymes in the digestive tract break down food molecules, which is
a process that occurs by hydrolysis.
The linking of monomers involves the
removal of water
Which molecule is not a carbohydrate?
Lipid
A lipid is a
hydrophobic polymer, not a carbohydrate.
Some molecules that are carbohydrates are
Glycogen
Cellulose
and
Starch
Monosaccharides
can be classified according to the spatial arrangement of their atoms.
Peptidoglycan is a
polysaccharide found only in bacteria.
Which complex carbohydrate contains only a-1, 4-glycosidic linkages?
Amylose
Cellulose’s function
structural component of plant cell walls
Cellulose is the
main structural component of plant cells walls
Which polysaccharide contains a modified monosaccharide?
Peptidoglycan
The N-acetylglucosamine and N-acetylmuramic acid units that make up peptidoglycan are composed of
modified glucose monomers.
Glycogen is
a polysaccharide found in animals
Animals store energy in the form of
glycogen
glucose + glucose —> _____ by _____.
maltose + water … dehydration synthesis
Maltose is the disaccharide formed when
two glucose molecules are linked by dehydration synthesis.
Which of these is a source of lactose?
milk
Lactose is the sugar found in
milk
Which of these is a polysaccharide?
cellulose
_____ is the most abundant organic compound on Earth.
cellulose
Cellulose is a
component of plant cell walls, and is the most abundant organic compound found on earth
Lactose, the sugar in milk, is a
disaccharide, because it can be split into two monosaccharides.
A simple sugar is composed of equal parts carbon and water, which gave rise to the general name of any sugar as a
carbohydrate
A carbohydrate that yields many monosaccharides when hydrolyzed is a
polysaccharide
A monosaccharide cannot be
hydrolyzed any further
Which is not a lipid?
RNA
RNA is a
nucleic acid.
Which of these are lipids?
phospholipid
steroids
cholesterol
wax
The fatty acid tails lack
double bonds
Phospholipids are composed of
a phosphate group, a glycerol, and fatty acids
Which of these is rich in unsaturated fats?
olive oil
Olive oil is a
plant oil, and most plant oils are rich in unsaturated fats
A function of cholesterol that does not harm health is its role _____.
as a component of animal cell membranes
Cholesterol is an important component of
animal cell membranes
Defensive proteins are manufactured by the _____ system.
immune
The immune system is involved in protecting the body against invasion by
foreign objects.
Proteins are polymers of
amino acids
What type of bond joins the monomers in a protein’s primary structure?
peptide
The amino acids of a protein are linked by
peptide bonds
Alpha helices and beta pleated sheets are characteristic of a protein’s
secondary structure
The secondary structure of a protein results from _____.
hydrogen bonds.
Electronegative oxygen and nitrogen atoms leave hydrogen atoms with partial positive charges.
Tertiary structure is NOT directly dependent on _____.
peptide bonds
Peptide bonds link together the amino acids of a protein’s
primary structure
Secondary structures describes the
alpha-helices and beta-sheets that are formed by hydrogen bonding between backbone atoms located near each other in the polypeptide chain.
Tertiary structure is
achieved when a protein folds into a compact, three-dimensional shape stabilized by interactions between side-chain R groups of amino acids
Primary structure is
the sequence of amino acids in a protein
Quaternary structure is
the result of two or more protein subunits assembling to form a larger, biologically active protein complex.
The tertiary and quaternary structures of proteins—how they fold into their overall three-dimensional shapes, and how different protein subunits come together to interact—both ultimately depend on the
primary structure, the sequence of amino acids in the proteins. A different sequence of amino acids will lead to different secondary structures and a different shape of the overall protein.
If a strand of DNA has the nitrogen base sequence 5’-ATTTGC-3’, what will be the sequence of the matching strand?
3’-TAAACG-5’
Adenine pairs with
thymine
Guanine pairs with
cytosine
If a DNA double helix is 100 nucleotide pairs long and contains 25 adenine bases, how many guanine bases does it contain?
75.
100 nucleotide pairs are a total of 200 nucleotides. Because of base pairing, if there are 25 adenine there must also be 25 thymine. This leaves 200–50 = 150 nucleotides to be divided evenly between guanine and cytosine.
The two strands of a DNA double helix are held together by _____ that form between pairs of nitrogenous bases.
hydrogen bonds
Nitrogenous base pairs are joined by
hydrogen bonds
A nucleotide is composed of a(n) _____.
phosphate group, a nitrogen-containing base, and a five-carbon sugar
Which structure is not a component of a nucleotide?
Sulfhydryl Oxygen group
Which structures are components of a nucleotide?
pentose
nitrogen-containing base
phosphate group
Nucleotide structure
The nitrogenous base is bonded to the sugar.
The sugar can either be ribose or deoxyribose
The sugar is bonded to the phosphate group.
The phosphate group is bonded to the sugar.
Guanine and uracil are examples of
nitrogenous bases.
Adenine, thymine, and cytosine are examples of
nitrogenous bases
Guanine, Uracil, Adenine, Thymine, and cytosine
examples of nitrogenous bases
Which linkage forms the backbone of a nucleic acid?
A sugar-phosphate linkage
In DNA’s structure
The nucleic acid strands in a DNA molecule are oriented antiparallel to each other.
The 5’ end of one strand in a DNA molecule is oriented opposite the 3’ end of the other strand, making the strands
antiparallel.
What is the complementary DNA sequence to 5’ ATGCATGTCA 3’?
5’ TGACATGCAT 3’
The nucleic acids DNA and RNA are made from chains of
nucleotides
Nucleotides consist of three components:
a five-carbon sugar (either ribose or deoxyribose), a nitrogenous base attached to the sugar’s 1’-carbon, and a phosphate group attached to the sugar’s 5’-carbon.
Components of Nucleotides (Nucleotide building blocks)
phosphate ribose deoxyribose purine pyrimidine
All of the genetic material in all living organisms is made from these basic building blocks of nucleotides.
nucleotides.
Thymine and deoxyribose occur
exclusively in DNA
Adenine, guanine, cytosine, and phosphate occur in
both DNA and RNA
Uracil and ribose occur
exclusively in RNA
DNA is used for
storage of genetic information.
The presence of deoxyribose as the sugar in DNA makes the molecule
more stable and less susceptible to hydrolysis.
The 2’-oxygen on the ribose found in RNA makes RNA
much more susceptible to breakdown.
It is important that mRNA be easily broken down, to ensure that
the correct levels of protein are maintained in the cell.
Three possible components of a DNA molecule
deoxyribose, phosphate group, thymine
DNA and RNA have similar structures:
a pentose sugar with a nitrogenous base and a phosphate group.
DNA and RNA differ in the
type of pentose sugar each possesses (DNA has deoxyribose; RNA has ribose) and in one base (DNA has thymine; RNA has uracil).
In a DNA sequence, the purine adenine always pairs with the
pyrimidine thymine
In a DNA sequence, the purine guanine always pairs with the
pyrimidine cytosine.
The base pair adenine-cytosine occurs
very rarely in nature. It only happens during a mutation event. When the DNA is replicated, one of the two daughters will contain a guanine-cytosine base pair in the location of the mutation, and the other daughter will contain an adenine-thymine base pair.
What is the function of fimbriae?
They are used to attach the cell to its substrate or to other prokaryotes.
Fimbriae are
hair-like projections that aid in attachment. They are also known as attachment pili to distinguish them from the pili used in conjugation.
How does the large amount of genetic variation observed in prokaryotes arise?
They have extremely short generation times and large populations.
They can exchange DNA with many types of prokaryotes by way of horizontal gene transfer.
The short generation times and large population sizes in most prokaryotic species, coupled with their ability to exchange genes, helps to
increase genetic variability beyond what we would expect in asexually reproducing organisms.
Genes for the resistance of antibiotics are usually located _____.
on plasmids
Bacteria that live around deep-sea, hot-water vents obtain energy by oxidizing inorganic hydrogen sulfide belched out by the vents. They use this energy to build organic molecules from carbon obtained from the carbon dioxide in seawater. These bacteria are _____.
chemoautotrophs
chemoautotrophs use
inorganic molecules (in redox reactions) for energy, and carbon dioxide for carbon.
Obligate anaerobes are
poisoned by O2.
Some obligate anaerobes live exclusively by fermentation; others extract chemical energy by anaerobic respiration, in which substances other than O2 accept electrons at the “downhill” end of electron transport chains.
Bacteria reproduce through
binary fisson. During binary fission, the DNA in the bacterial chromosome is replicated, and one copy is passed to each daughter cell. Although plasmids (small, circular DNA molecules separate from the main bacterial chromosome) are not shown in the figure, any plasmids in a bacterial cell are also replicated and passed to each daughter cell during binary fission. Mutations that arise during DNA replication are one source of genetic variation in bacterial populations. The rapid reproduction and large sizes of many bacterial populations can yield considerable genetic variation despite a low mutation rate.
Gram-positive bacteria
- alcohol rinse does not remove crystal violet.
- have a thick peptidoglycan layer
- appear purple have Gram staining
Gram-negative bacteria
- alcohol rinse easily removes crystal violet
- have a thin peptidoglycan layer
- appear pink after Gram staining
- have an outer membrane as part of their cell wall structure
Both gram-positive bacteria and gram-negative bacteria
have a plasma membrane
Gram staining is a technique for
classifying bacteria based on differences in the structure of their cell walls.
_____ are surface appendages that allow a bacterium to stick to a surface.
Pili
Pili enable bacterial cells to
stick to a surface
What is the function of a bacterium’s capsule?
protection
Where is a bacterial cell’s DNA found?
nucleoid region
Bacteria lack a nucleus so
their DNA is found in the nucleoid region.
In a bacterium, where are proteins synthesized?
ribosomes
Ribosomes are involved in the
manufacture of polypeptides (proteins).
What name is given to the rigid structure, found outside the plasma membrane, that surrounds and supports the bacterial cell?
cell wall
The cell wall is a
rigid supporting structure
The _____ is the bacterial structure that acts as a selective barrier, allowing nutrients to enter the cell and wastes to leave the cell.
plasma membrane
The plasma membrane is
selectively permeable
The structure that regulates the passage of material into and out of this bacterial cell is
the plasma membrane
Beginning within the nucleus, the first step leading to the synthesis of a polypeptide is _____.
transferring of information from DNA to messenger RNA
Transcription is the
first of the two main steps of protein synthesis.
Pancreatic cells, which secrete a large amount of digestive enzymes, are labeled with radioactive leucine and then chased for several hours with nonradioactive leucine. Photographic emulsions are prepared at different times during the chase. Where would the black spots appear on an emulsion prepared 3 hours after the pulse?
Exterior of the cell.
Black spots would appear on the exterior of the cell after 3 hours, indicating that the proteins had been secreted from the cell.
What path does a protein in the secretory pathway take, starting from its site of synthesis?
Rough ER, Golgi apparatus, secretory vesicles, plasma membrane
Proteins are
synthesized in the rough ER, modified in the Golgi apparatus, and carried in secretory vesicles to the plasma membrane, where they are secreted.
During a pulse-chase experiment, photographic emulsions were prepared at different times during the chase, and radioactive spots were detected at the following times and locations: 5 minutes: rough ER; 10 minutes: Golgi apparatus; 40 minutes: endosomes; 70 minutes: lysosomes; 140 minutes: lysosomes. Which of the following conclusions can be drawn from these results?
The final destination of the proteins was the lysosome.
This conclusion can be drawn from the results, since the radioactive spots were last detected at the lysosome, which is not a secretory vesicle.
What scientific hypotheses can be tested by a pulse-chase experiment?
Movement of molecules through a cell over time
Pulse–chase experiments allow for the tracking of molecules in a cell over time.
Which organelle plays a role in intracellular digestion?
lysosome.
The prefix “lyso-“ means decomposition.
The pathway of secretory proteins
Proteins that are secreted from a eukaryotic cell must first travel through the endomembrane system. As they are being synthesized, secretory proteins enter the lumen of the endoplasmic reticulum. From the ER, vesicles transport these proteins to the Golgi, where they are sequentially modified and concentrated in a cis-to-trans direction. Secretory vesicles bud from the Golgi and move along cytoskeletal filaments to eventually fuse with the plasma membrane, secreting their protein cargo. Each of these transport steps requires specialized proteins to ensure that the cargo is sent to the proper location and is able to fuse with the target membrane.
The cilia and flagella of eukaryotic cells are composed of _____.
microtubules
Eukaryotic cilia and flagella are composed of
microtubules.
Prokaryotes thrive (live)
almost everywhere, including places too acidic, salty, cold, or hot for most other organisms
Most prokaryotes are
microscopic, but what they lack in size they make up for in numbers
Prokaryotes are divided into two domains:
Bacteria and archaea
Domain Archaea
things live in extreme environments
Domain bacteria
things live in regular environments
Earth’s first organisms were likely
prokaryotes.
been around the longest.
Most prokaryotes are
unicellular, although some species form colonies
Most prokaryotic cells are much smaller than
eukaryotic cells
Prokaryotic cells have a
variety of shapes
The three most common shapes of prokaryotic cells are
spheres (cocci)
rods (bacili)
and
spirals (spirilla)
An important feature of nearly all prokaryotic cells is their
cell wall
which maintains cell shape, protects the cell, and prevents it from bursting in a hypotonic environment
Eukaryote cell walls are made of
cellulose or chitin
Bacterial cell walls contain
peptidoglycan, a network of sugar polymers cross-linked by polypeptides
Archaea contain
polysaccharides and proteins but lack peptidoglycan
scientists use the Gram Stain to
classify bacteria by cell wall composition
Gram-positive bacteria have
simpler walls with a large amount of peptidoglycan
Gram-negative bacteria have
less peptidoglycan and an outer membrane that can be toxic
Gram-positive bacteria
turn purple.
have a cell wall with only a peptidoglycan layer. and the peptidoglycan layer is bigger than gram-negative bacteria.
And then it has a plasma membrane underneath
Gram-negative bacteria
turn pink.
have a cell wall that has an outer membrane and a smaller layer of peptidoglycan.
and then a plasma membrane underneath.
many antibiotics target
peptidoglycan and damage bacteria cell walls
gram-negative bacteria are more likely to be
antibiotic resistant.
not good to get.
A polysaccharide or protein layer called a capsule covers
many prokaryotes
Some prokaryotes have fimbriae, which
allow them to stick to their substrate or other individuals in a colony.
They are like hairy looking extensions.
Pili (or sex pill) are longer than
fimbriae and allow prokaryotes to exchange DNA
In a heterogeneous environment, many bacteria exhibit
taxis, the ability to move forward or away from a stimulus
Chemotaxis is the
movement toward or away from a chemical stimulus
Most motile bacteria propel themselves by
flagella scattered about the surface or concentrated at one or both ends
Flagella of bacteria, archaea, and eukaryotes are
composed of different proteins and likely evolved differently
Prokaryotic cells usually lack
complex compartmentalization (They dont have membranes on the inside. no nucleus)
Some prokaryotes do have
specialized membranes that perform metabolic functions.
These are usually infoldings of the plasma membrane
The prokaryotic genome has less DNA than the
eukaryotic genome
Most of the genome consists of a
circular chromosome
The chromosome is not surrounded by a membrane; it is located in the
nucleoid region
Some species of bacteria also have similar rings of DNA called
plasmids
There are some differences between prokaryotes and eukaryotes in
DNA replication, transcription, and translation.
These allow people to use some antibiotics to inhibit bacterial growth without harming themselves.
DNA is a big circularish piece in a part which is called the
nucleoid region
Prokaryotes reproduce quickly by
binary fission and can divide every 1-3 hours.
they reproduce really fast
Key features of prokaryotic reproduction
they are small
they reproduce by binary fission
they have short generation times
Prokaryotes have short generation times which means
it doesn’t take a lot of time to mature as bacteria
Many prokaryotes form metabolically inactive
endospores, which can remain viable in harsh conditions for centuries
Prokaryotes short generation time allows them to
evolve quickly.
For example, adaptive evolution in a bacterial colony was documented in a lab over 8 years.
Prokaryotes are not “primitive” (simple) but are
highly evolved.
They are good at what they do.
Prokaryotes have
considerable genetic variation.
Three factors that contribute to Prokaryote’s genetic diversity
Rapid reproduction
Mutation
Genetic recombination
Prokaryotes reproduce by
binary fission, and offspring cells are generally identical
Mutation rates during binary fission are
low, but because of rapid reproduction, mutations can accumulate rapidly in a population
High diversity from mutations allows for
rapid evolution
Genetic recombination
the combining of DNA from two sources, contributes to diversity.
genetic recombination- mixing DNA from different types of bacteria?
Prokaryotic DNA from different individuals can be brought together by
transformation
transduction
conjugation
Movement of genes among individuals from different species is called
horizontal gene transfer
Transformation is when
floating around bacterial cells pick up other DNA and pick it up
A prokaryotic cell can take up and incorporate foreign DNA from the surrounding environment in a process called
transformation
Transduction is
the movement of genes between bacteria by bacteriophages (viruses that infect bacteria)
transduction is when
it takes bacterial DNA and puts it into another DNA with the help of a virus that moves it from one to another.
Transduction-virus picking up DNA and moving it
Conjugation is
the process where genetic material is transferred between prokaryotic cells
In bacteria,
the DNA transfer is one way
A donor cell attaches to a recipient by a
pilus, pulls it closer, and transfer DNA
A piece of DNA called the
F Factor is required for the production of pili
F Factor
plasmid
R plasmids
carry genes for antibiotic resistance.
pieces of DNA that tell you how to resist antibiotics
Antibiotics kill sensitive bacteria, but
not bacteria with specific R plasmids
through natural selection,
the fraction of bacteria with genes for resistance increases in a population exposed to antibiotics.
Antibiotic-resistant strains are becoming more common.
Prokaryotes can be categorized by how they obtain energy and carbon
phototrophs
chemotrophs
autotrophs
heterotrophs
Phototrophs
obtain energy from light
Chemotrophs
obtain energy from chemicals
Autotrophs
require CO2 as a carbon source
Heterotrophs
require an organic nutrient to make organic compounds
Energy and carbon sources are combined to give four major modes of nutrition
photoautotrophy
chemoautotrophy
photoheterotrophy
chemoheterotrophy
We are
chemoheterotrophs.
We get energy from chemicals and require an organic nutrient to make organic compounds?
Prokaryotic metabolism varies with respect to
O2
Obligate aerobes
require O2 for cellular respiration.
have to have it to live
Obligate anaerobes
are poisoned by O2 and use fermentation or anaerobic respiration.
Can’t live with oxygen.
Facultative anaerobes
can survive with or without O2.
Doesn’t matter if they have oxygen or not.
Ex. yeast.
Nitrogen is essential for the
production of amino acids and nucleic acids.
Prokaryotes have to get
nitrogen
Prokaryotes can metabolize nitrogen in
a variety of ways
In nitrogen fixation,
some prokaryotes convert atmospheric nitrogen (N2) to ammonia (NH3)
Cooperation between prokaryotes allows them to use environmental resources they could not use as
individual cells
Bacteria cooperate (work)
together
In the cyanobacterium Anabaena,
photosynthetic cells and nitrogen-fixing cells called heterocysts (or heterocysts) exchange metabolic products.
In some prokaryotic species
metabolic cooperation occurs in surface-coating colonies called biofilms.
biofilms are like the nasty stuff you get/feel on your teeth.
Bacteria that ________ tend to have abundant internal membranes.
are photosynthetic
Cyanobacteria have
thylakoid membranes, much like those in chloroplasts, that function in photosynthesis
Bacterial cells, but not eukaryotic cells, possess
a nucleoid with a circular chromosome
The bacterial chromosome is
one double-stranded DNA molecule in the form of a ring, and is not contained within a nuclear envelope
What is a difference between bacteria and archaea?
Bacteria and Archaea have different chemicals in their cell membranes and cell walls.
Bacteria have
peptidoglycan in their cell walls
Archaea never have
peptidoglycan
Plasmids
often contain antibiotic resistance.
are transferred from one bacterium to another by conjugation.
allow bacteria to survive adverse conditions.
replicate independently of the main chromosome.
Plasmids may also direct the
metabolism of rarely encountered nutrients
An F+ bacterial cell
acts as a donor during conjugation.
The F+ designation indicates that the bacterial cell has the genes necessary to initiate conjugation and transfer DNA to the receptor cell.
Photoautotrophs use
light as an energy source and CO2 as a carbon source
Gram-negative bacteria have less peptidoglycan than gram-positive cells, and their cell walls are
more complex structurally.
Gram-negative bacteria do not contain as much
peptidoglycan. They have an additional outer membrane with lipopolysaccharides
Portions of the genomes of certain prokaryotic species are very similar to portions of the genomes of distantly related prokaryotes. The process that most likely accounts for this genetic similarity is
horizontal gene transfer.
prokaryotes are adept at obtaining DNA from other sources, including other species of prokaryotes, through the processes of
conjugation, transformation, and transduction.
Bacteria that use light for their energy source and CO2 for their carbon source are called
photoautotrophs.
Photoautotrophs are photosynthetic organisms that harness light energy to drive the synthesis of organic compounds from carbon dioxide.
Scientists hypothesize that the O157:H7 strain of E. Coli is so different from the K-12 strain because of
horizontal gene transfer over many years, most likely through the action of bacteriophages.
Many of these imported genes are associated with the pathogenic bacterium’s invasion of the host.
The desulfovibrio bacterium breaks down organic matter (which it must have) and uses sulfate (not oxygen) as an electron acceptor. As a result, it produces hydrogen sulfide (H2S), accounting for the “rotten egg” smell of swamp muck. Oxygen is a deadly poison to Desulfovirbrio. We would call Desulfovirbrio an
obligately anaerobic chemoheterotroph.
Obligate anaerobes are poisoned by oxygen.
Chemoheterotrophs must consume organic molecules for both energy and carbon.
Why is salt a good preservative to use for foods such as pork and fish?
Prokaryotic cells living in the food will shrink from their cell walls, impacting their ability to reproduce.
A gram-negative cell wall consists of
a thin layer of peptidoglycan surrounded by an outer membrane containing lipipolysaccharides
Which of the following involves metabolic cooperation among prokaryotic cells?
biofilms
In an experiment, a microbiologist put equal numbers of each of the following organisms into a flask of sterile broth, consisting mostly of sugar and a few amino acids. She then placed the flask in the dark. Which of the organisms would be most likely to survive?
chemoheterotrophic bacteria.
these organisms do not require light and use organic compounds for both energy and carbon
Which statement about prokaryotes is true?
prokaryotes are widely used for bioremediation.
prokaryotes have been used in sewage treatment for decades, and they are being used to clean up oil spills and radioactive waste.
prokaryotes are completely indispensable to which chemical cycle?
nitrogen.
Nitrogen-fixing bacteria are
the only organisms that can fix atmospheric nitrogen into compounds that other organisms can use to build cellular components.
Which of the following is true about R Plasmids?
R plasmids can carry genes that confer resistance to many antibiotics,
and they can be transferred via conjugation
How is it possible that as many as 9 million mutations can arise each day in the E. coli inhabiting one human?
the mathematics of large population size and rapid reproduction rate combine to produce many mutations without a particularly high mutation rate.
SImply by rapid multiplication and a very large population with a normal mutation rate,
enormous numbers of mutations can arise in a single day. Even if many of the mutations are lethal, they will hardly make a dent in the population.
Bacterial flagella have a very complex structure composed of 42 distinct proteins. What is the most likely explanation for the evolution of these complex structures?
exaptation.
proteins that were already part of the bacterial body were modified through natural selection to take on new functions as the bacterial flagella.
Which statement about transformation is true?
it can be facilitated by cell-surface proteins that recognize compatible DNA.
for some bacteria, transformation is a very important source of genetic material, and they have evolved mechanisms to make the process efficient.
genetic variation in bacterial populations cannot result from
meiosis.
genetic variations in bacterial populations can result from
mutation transformation conjugation and transduction
the bacteria that cause tetanus can be killed only by prolonged heating at temperatures considerably above boiling. this suggests that these bacteria
produce endospores.
endospores are extremely heat resistant.
biofilms are an example of
metabolic cooperation among prokaryotic species.
Bacteria in biofilms send signals to each other, produce structures to channel nutrients in and wastes out, and
produce proteins that help the cells adhere to the substrate and to each other.
in the absence of meiosis and sexual reproduction, what general process allows genetic recombination among prokaryotes?
horizontal gene transfer
horizontal gene transfer by wat of transformation, transduction, and conjugation allows
bacteria to share genetic material and recombine it.
The peptide bond is
a covalent bond joining amino acids together to form a polypeptide.
It is a specific type of covalent bond joining two amino acids.
The lipids that form the main structural component of cell membranes are
phospholipids
Phospholipids have a
hydrophilic head and two hydrophobic tails. This permits the phospholipids to be arranged in a bilayer, or double layer, which forms a boundary between the cell and its external environment.
a glucose molecule is to starch as
a nucleotide is to a nucleic acid.
Nucleotides are the monomers that make
nucleic acid polymers, just as glucose is the monosaccharide (monomer) from which starch (polymer) is constructed
Carbohydrates can function in which of the following ways?
structural support and energy storage.
Carbohydrates function as both
storage molecules (starch, glycogen) and as structural support molecules (Cellulose)
In what polysaccharide form do plants store glucose to be available later as an energy source?
Starch.
Starch is a glucose storage polymer in
plants.
The molecular formula for glucose is C6H12O6. what would be the molecular formular for a polymer made by linking ten glucose molecules together by dehydration reactions?
C60H102O51
The fatty acid tails of a phospholipid are hydrophobic because they
have no charges to which water molecules can adhere.
Phospholipid tails, which consists of nonpolar hydrocarbon chains, are
hydrophobic
One characteristic shared by sucrose, lactose, and maltose is that
they are all disaccharides.
A disaccharide consists of
two monosaccharides joined together by a glycosidic linkage
Which of the following is a polymer?
cellulose, a plant cell wall component.
The polysaccharide cellulose is a
major component of plant cell walls.
It is a polymer composed of many glucose monomers joined together by glycosidic linkages.
A polysaccharide that is used for storing energy in human muscle and liver cells is
glycogen.
Humans and other vertebrates store glucose as a
polysaccharide called glycogen in their liver and muscles
When a protein is denatured, why does it lose its functionality?
denaturation breaks the weak bonds, such as hydrogen bonds and van der Waals interactions, that hold the protein in its three-dimensional shape. Without the proper shape, the protein cannot function.
Denaturation disrupts
secondary, tertiary, and quaternary protein structure, causing the protein to lose its form, and thus its function
Lipids differ from other large biological molecules in that they
are not truly polymers.
Lipids are not all made of the same type of
monomer. Their association as a group (fats, phospholipids, and steroids) is related to their solubility behavior.
Which of the following are pyrimidines found in the nucleic acid DNA?
thymine and cytosine
The polysaccharide that you are most likely to have eaten recently is
starch.
Starch is a
storage polysaccharide found especially in certain plant tissues
What is the process by which monomers are linked together to form polymers?
dehydration or condensation reactions
When monomers are linked together to form a more complex polymer,
a water molecule is removed by dehydration (condensation) reactions
A shortage of phosphorus in the soil would make it especially difficult for a plant to manufacture
DNA.
the backbone of a nucleic acid consists of
alternating sugar and phosphate groups.
What do Alzheimer’s, Parkinson’s, and mad cow disease have in common?
all have been associated with the buildup of misfolded proteins in cells.
These diseases and others have been associated with a buildup of misfolded versions of various proteins within cells.
Which of the following is true regarding complementary base pairing in DNA and RNA molecules?
Although the base pairing between two strands of DNA in a DNA molecule can be thousands to millions of base pairs long, base pairing in an RNA molecule is limited to short stretches of nucleotides in the same molecule or between two RNA molecules
Complementary base pairing provides an
accurate way to synthesize a new DNA molecule from an existing one, and gives RNA molecules particular three-dimensional shapes necessary for their function.
The enzyme amylase can break glycosidic linkages between glucose monomers only if the monomers are in the a form. Which of the following could amylase break down?
glycogen, stach, and amylopectin
Some lipids are formed when fatty acids are linked to glycerol. These subunits are linked together by
ester linkages.
In making a fat, each of the three fatty acid molecules is bonded to a glycerol by an
ester linkage type of covalent bond
Which of the following lists ranks these molecules in the correct oder by size? from largest to smallest.
protein, sucrose, glucose, water
which type of protein shields a newly forming protein from cytoplasmic influences while it is folding into its functional form?
chaperonins
Chaperonins shield proteins from
“bad influences” (interactions with other molecules in the cytoplasm) while they are folding into their functional forms
A polypeptide is a
chain of amino acids that have been linked together by dehydration reactions
What is the term for compounds that do not mix with water?
hydrophobic
Hydrophobic compounds are those that are
insoluble in water
which of the following components of a tossed salad will pass through the human digestive tract and be digested the least?
cellulose (in the lettuce)
Cellulose contains
glycosidic linkages that cannot be broken by human digestive enzymes
Omega-3 fatty acids are
polyunsaturated fats that contain three or more cis double bonds and are found in vegetable oils, some nuts, and in fatty fish. Considered essential fatty acids, they are required for normal growth in children and studies suggest that they provide protection against cardiovascular disease in adults.
On the basis of the principle of complementary base pairing, you would expect the percentage of adenine to be equal to the percentage of
thymine
Which of the following carbohydrate molecules has the lowest molecular weight?
glucose
glucose is a
monosaccharide
Which of the following describes differences between DNA and RNA?
RNA molecules consist of a single polynucleotide chain, whereas DNA molecules consist of two polynucleotide chains organized into a double helix.
They contain different sugars.
One of their nitrogenous bases is different.
the alpha helix and beta pleated sheet represent which level of protein structure?
secondary structure
Both the alpha helix and the beta pleated sheet are localized regions of
polypeptides held in a given structure by hydrogen bonds
Protein molecules are polymers (chains) of
amino acid molecules
Polymers of amino acids are called
polypeptides
A protein consists of
one or more polypeptides folded into specific conformations
Which of the following statements concerning unsaturated fats is true?
they have double bonds in the carbon chains of their fatty acids
Amylase is an enzyme that breaks down starch. Why can’t the same enzyme break down cellulose?
the monosaccharide monomers in cellulose are bonded together differently than in starch.
The glucose monomers in cellulose are bonded in a
beta glycosidic linkage, whereas those in starch have an alpha glycosidic linkage. the enzyme amylase is specific for the alpha glycosidic linkage.
The sex hormones estrogen, progesterone, and testosterone belong to which class of molecules?
lipids.
Steroids, such as estrogen, progesterone, and testosterone, are lipids based on their
insolubility in water. the molecules are characterized by a carbon skeleton consisting of four fused rings of carbon atoms.
What is a distinguishing feature of most naturally occurring fats?
nearly all naturally occurring unsaturated fats have cis double bonds
Naturally occurring unsaturated fats found in plants and fish are distinguished by the
presence of one or more cis double bonds in their hydrocarbon chains
A nucleotide is made of which of the following chemical components?
a nitrogenous base, a phosphate group, and a pentose sugar
Each nucleotide consists of three parts:
an organic molecule, called a nitrogenous base
a 5 carbon sugar, called a pentose
and a phosphate group that serves in the phosphodiester covalent bond that forms a bridge between adjacent nucleotides
In a hydrolysis reaction, a polymer is broke up into its constituent monomers, and in this process water is
consumer.
the meaning of “hydrolysis” is
“to break with water”
Enzyme molecules require a specific shape to perform their catalytic function. Which of the following might alter the shape of an enzymatic protein?
denaturing the protein
a change in salt concentrations of pH
mixing in a chemical that removes hydrogen bonds
heating the protein
Which of the following molecules is a monosaccharide?
C6H12O6
Monosaccharides have molecules formulas that are multiples of
CH2O
If a small droplet of triaclyglycerol molecules is suspended in water, the fat molecules form a “ball of spaghetti” with no particular orientation. But if a droplet of phospholipid molecules is put in water, all the molecules point outward, toward the water. Phospholipids are forced into this orientation because phospholipids have
a charged end and a noncharged end.
The hydrocarbon tails of phospholipids are
hydrophobic and are excluded from water. The negatively charged phosphate group and its attachments form a hydrophilic head that is attracted to water.
The enzyme amylase can break glycosidic linkages between glucose monomers only if the monomers are in the a (alpha) form. Which of the following could amylase break down?
glycogen, starch, and amylopectin
Which of the following statements concerning unsaturated fats is true?
They have double bonds in the carbon chains of their fatty acids.
Which of the following categories includes all of the others in the list?
a. monosaccharide
b. disaccharide
c. starch
d. carbohydrate
e. polysaccharide
d. carbohydrate
The structural level of a protein least affected by a disruption in hydrogen bonding is the
primary level
Enzymes that break down DNA catalyze the hydrolysis of the covalent bonds that join nucleotides together. What would happen to DNA molecules treated with these enzymes?
The phosphodiester linkages of the polynucleotide back bone would be broken
The molecular formula for glucose is C6H12O6. What would be the molecular formula for a polymer made by linking ten glucose molecules together by dehydration synthesis?
C60H102O51
Which of the following pairs of base sequences could form a short stretch of a normal double helix of DNA?
5’-ATGC-3’ with 5’-GCAT-3’
