Cell Phys Exam 1
K
the substrate concentration at which ½ Vmax is achieved
electronegativity
the tendency of an atom to attract electrons
true A lower KM indicates a higher E-S affinity. A higher KM indicates a lower E-S affinity. The KM of an enzyme is approximately equal to the physiological concentration of substrate available to it.
true or false A lower KM indicates a higher E-S affinity. A higher KM indicates a lower E-S affinity. The KM of an enzyme is approximately equal to the physiological concentration of substrate available to it.
false One thing all cells DO NOT have in common is an ability to colonize any environment on Earth.
true or false Is the following statement true, false, or impossible to determine? One thing all cells have in common is an ability to colonize any environment on Earth.
replication
DNA synthesis
0.01
10 A = _______ micrometers
It contains carbon-carbon bonds. Its cellular synthesis is directed by enzymes.
Based on your knowledge of other biological macromolecules, what are reasonable assumptions about your macromolecule? Choose one or more:
CO2; completely oxidized carbon
Carbon atoms cycle continuously through the biosphere. What is a by-product of cell respiration, and what does this by-product represent?
Fly
Drosophila melanogaster
Bacterium. Cylinders/ovals.
Escherichia coli
translation
Protein synthesis
enzyme
Proteins that catalyze the breaking or formation of covalent bonds in another molecule (or in the same molecule in some cases!)
An electron microscope
Ribosomes can most readily be visualized using
Km
The concentration of substrate required for significant catalysis to take place
During centrifugation, the proposed macromolecule sediments as a single, discrete band in the centrifuge tube.
What evidence may have led you to conclude that the molecule is a macromolecule?
hydrolysis
What general metabolic process is depicted here? CH2OH
reversible inhibitor
bind loosely to an enzyme, and are readily displaced
irreversible inhibitor
bind very tightly to the enzyme, sometimes forming a covalent bond with the enzyme.
Catabolic reactions
break down food molecules and in the process release energy
spontaneous reaction
catabolism is a __________
carbohydrates, proteins, nucleic acids (DNA and RNA), and lipids.
four categories of macromolecules
Competitive inhibitors
inhibitors that mimic the substrate and therefore bind at the active site
First two laws of thermodynamics
the total energy of a system plus that of its surroundings is constant; forms of energy are interconvertible the total entropy of a system plus that of its surroundings always increases
true Enzyme involvement does not affect DG in any way, only the rate of the reaction.
true or false Enzyme involvement does not affect DG in any way, only the rate of the reaction.
nucleus
where does transcription take place?
enzymes
- accelerates a reaction by lowering its activation energy-an enzyme is protein in nature (may be associated with a non-protein cofactoror coenzyme) -present in a cell at a low concentration (relatively few copies needed per cell) -is not permanently altered in the course of a reaction -is highly specific for its particular substrate/s and yields expected product/s -may be regulated to meet the needs of a cell
saturated hydrocarbons
A cell's plasma membrane with a greater degree of _______ will exhibit less fluidity at room temperature.
cell wall
Antibiotics tend to target features that are unique to bacterial cells and absent from eukaryotic cells such as our own. Which of the following would present a safe target for a new antibiotic?
Mustard plant
Arabidopsis thaliana
blood: 10,000 to1 ; stomach: 0.01 to 1
Aspirin has a pKa of 3.4. What is the ratio, [A-] to [HA], of aspirin when it is in the blood (pH 7.4), and what is the ratio, [A-] to [HA], of aspirin when it is in the stomach (pH 1.4)? Note: you do not have to come up with the concentrations [A-] and [HA], just the ratio Henderson-Hasselbalch Equation pH = pK + log ([A-]/[HA])
Zebrafish
Danio rerio
false In cells, electrostatic attractions are NOT stronger than covalent bonds.
Determine whether the following statement is true or false: In cells, electrostatic attractions are stronger than covalent bonds.
Enzymes are highly specific for their substrates
Each of the following statements is true for enzymes EXCEPT:
This excerpt is meant to explain that the cell membrane is not rigid, but fluid - despite being part of a living room cell analogy. Rather than staying put like a frame, receptors will fluidly move along the membrane of a cell.
Explain this excerpt from The Living Room Cell, in one or two sentences: "Unlike your living-room wall, large regions of the cell membrane are fluid, at least in a sense. They are not rigid. Drive a nail into your wall and it stays put. But thrust a receptor into the cell membrane and it will drift around, something like a block of wood floating on the surface of a pond."
electron microscope
How would you best visualize the detailed structure of a phospholipid bilayer? Note: a PL bilayer is about 5nm thick (that's 0.005 µm).
Cytoplasm: contents of the cell contained within the plasma membrane, but outside the nucleus. Cytosol: the contents of the cell cytoplasm excluding organelles and cytoskeleton
In a eukaryotic cell, what if the difference between cell cytoplasm and the cell cytosol?
They are propagated (grown, maintained) at a non-permissible (warmer) temperature.
In order to study a mutation that is lethal (that is, the mutant is not viable and therefore cannot by propagated for study), conditional mutants, such as temperature-sensitive mutants, may be used. Which of the following is NOT true about temperature-sensitive mutants?
Mitochondria and chloroplasts
In terms of their DNA and RNA contents, which of the following two organelles are most similar to each other?
-7.4 kcal/mole
In the first reaction of glycolysis (the pathway that begins the oxidative breakdown of sugars), the enzyme hexokinase uses ATP to catalyze the phosphorylation of glucose to glucose 6-phosphate and ADP. The ΔG° of this reaction is a favorable -4.06 kcal/mole. Another sometimes active enzyme, called glucose 6-phosphatase, effectively "reverses" this reaction, hydrolyzing glucose 6-phosphate back to glucose and releasing a phosphate. The ΔG° of this reaction is -3.34 kcal/mole. Based on these values, what is the ΔG° for the hydrolysis of ATP: ATP + H2O → ADP + Pi?
false Photosynthetic bacteria DO NOT contain chloroplasts.
Is the following statement true, false, or impossible to determine? Photosynthetic bacteria contain chloroplasts.
ionic bond hydrogen bond van der waals forces
Place a check next to each example of a non-covalent bond (attractive force).
glycosaminoglycan cellulose chitin
Place a check next to each substance naming a structural (rather than nutritional) polysaccharide.
transmission
The bacterial cell micrograph is most likely a __________ electron micrograph.
NADH carries an extra proton and two high-energy electrons.
What is the difference between NAD+ and NADH
lipid
What type of molecule found in the cell was observed in Part 1?
anabolic reactions
require energy and result in the generation of more complex molecules.
cation
When sodium loses an outer electron, it becomes positively charged, and a positively charged atom is called a(n) _____
archaea and bacteria
Which of the following are prokaryotes?
microtubules > intermediate filaments > actin filaments
Which of the following correctly ranks the three cytoskeletal elements with respect to size, largest to smallest (in diameter)?
bond between carbon and hydrogen, -C-H
Which of the following covalent bonds is relatively nonpolar?
Eukaryotes evolves from bacteria, eventually acquiring chloroplasts; later, a subset of eukaryotes acquired mitochondria
Which of the following is NOT true about the evolution of eukaryotic cells? It is thought that
As it occurs in nature, its stereochemistry is b-D
Which of the following is NOT true regarding the molecule depicted below: aDglucopyranose.png Note: b- = Greek letter beta NOTE: equilibrium does not indicate equal concentrations
The surfaces of A and D match well and therefore can form enough weak bonds to withstand thermal jolting; they therefore stay bound to each other during the experiment.
Which of the following is consistent with the data presented in the figure, which depicts three hypothetical interactions between macromolecule A and macromolecules B, C, and D?
An attractive force exists between a cation, (formed when electrons are lost), and an anion (formed when electrons are gained).
Which of the following most accurately describes an ionic bond?
Bacteria do not have a nucleus. The number of chromosomes varies from one organism to another, but is constant in all nucleated cells (except germ cells) within the same multicellular organism. The nuclear envelope is a double membrane, and mitochondria are surrounded by both an inner and an outer membrane. Peroxisomes and lysosomes contain enzymes that catalyze the breakdown of substances produced in the cytosol or taken up by the cell. One can argue, however, that many of these substances are degraded to generate food molecules, and as such are certainly not "unwanted."
Which of the following statements are correct? Explain your answers.
Hydrogenation reactions are oxidations, and dehydrogenation reactions are reductions.
Which of the following statements is not true?
ATP and magnesium cations
Which of the following would most likely interact by forming an ionic bond?
ribosome
Which of these cannot be resolved with a conventional light microscope?
Saccharomyces cerevisiae do not contain chloroplasts.
Which of these statements is consistent with the data presented in the evolutionary tree?
glucose oxidation EXERGONIC reactions are spontaneous. skewed right.
Which reaction will occur spontaneously?
A pairs with T, and G pairs with C.
Which statement is correct about base pairing in DNA?
The KM of an enzyme is approximately equal to the physiological concentration of the substrate available to it.
Why does Km give an indication of the affinity that an enzyme has for a substrate?
the nucleus mitochondria
You are a biologist interested in studying how eukaryotic cells obtained their unique features during their evolution from a prokaryotic ancestor. Which cellular features, unique to eukaryotes, might you focus on?
B, C, A
You are studying a reaction pathway within a cell in which you know metabolite A gets converted to metabolite D through two intermediate compounds, B and C (in that order). Each reaction is enzyme catalyzed. You think enzymes X, Y, and Z are involved (loss of any one prevents D formation), but you don't know which particular step each catalyzes. To uncover this, you individually add an inhibitor of each enzyme to cells and look to see which metabolite builds up. Results are shown in the table:
adding a hydroxyl group adding a carboxyl group
You have developed a promising anti-cancer agent, but it has poor solubility in water. Which of the following changes should improve water solubility?
increase the concentration of reactants continually remove products
Your company has developed an organic molecule with commercial potential and you know how to produce it in the lab. You want to increase production and make as much of the molecule as possible, but the reaction has a positive ΔG°. What can you do to try to drive the reaction toward your desired product?
noncompetitive inhibitor
a reversible inhibitor •binds to a site on the enzyme other than the active site •distorts the active site of the enzyme
competitive inhibitor
a reversible inhibitor •mimics the substrate •competes with a substrate for access to the active site of the enzyme •is not converted to product
Endoplasmic Reticulum
"There are vast areas of great floppy sheets, like a deflated hot air balloon that has been folded loosely and studded with thousands of marbles. The layers and layers of balloons wrap around VW nucleus, almost concealing it." Great floppy sheets:
ribosomes
"There are vast areas of great floppy sheets, like a deflated hot air balloon that has been folded loosely and studded with thousands of marbles. The layers and layers of balloons wrap around VW nucleus, almost concealing it." thousands of marbles:
the cell theory
1. All organisms are composed of one or more cells, 2. The cell is the basic organizational unit of life, 3. All cells arise from pre-existing cells
1000
10 A = ______ picometers
1
10 A = _______nanometer
enzyme kinetics
A measure of the rate at which an enzyme catalyzes a reaction at given experimental conditions
Wrong. While different types of cells are different sizes (and shapes!), for all cells, size is limited. This is due to the mechanisms needed for cell survival and how the cells' requirements are met by materials that must cross the plasma membrane and reach some interior or exterior destination, and by the structures that form and are contained within the cell. For example,Keeping the cell small maintains a large (surface area) / volume ratio. This is helpful because nutrients needed to sustain the cell enter via the surface of the cell and are needed in quantities related to the cell volume. One way to think of this is that a larger cell has more cytoplasm, and more cytoplasm results in higher demands for supplies via the cell membrane.Keeping the cell small results in a lower volume (interior). This is helpful because molecules and ions can more readily interact as they randomly diffuse in intracellular spaces.Keeping the cell small places fewer demands on the cytoskeleton, which serves to protect and support the structure of the cell as well as helping to maintain the shape of the cell.
A typical cell from an elephant is much larger than typical cell from a fruit fly. Right or wrong?
Vmax
At high very high substrate concentrations, the enzyme is approaching saturation (most active sites are occupied at any one moment), and the reaction is nearing its maximum velocity
Nematode worm
Caenorhabditis elegans
outer membrane --> cell wall --> plasma membrane
Cell diagram in order from outermost to innermost:
In the cytosol
Consider a eukaryotic cell. In what space does translation take place?
In the cytosol.
Consider a prokaryotic cell. In what space does translation take place?
oxygen
Consider an O-H covalent bond in H2O. In H2O, the __________ atom more strongly attracts electrons and acquires a partial negative charge within the molecule itself.
Your left hand
Consider the issues of surface area to volume ratio in the context of a cell, then consider the following: you have a glove and a mitten. They are made of the same material. You put the glove on your left hand, the mitten on the right hand, and go out into subfreezing temperatures. Which hand will become cold sooner - your right hand or your left?
pH = 3.4; blood
Consider the question above related to the dissociation of aspirin. At what pH would the aspirin begin to dissociate, and in what fluid is this acid most dissociated (in blood or stomach fluid)?
10^1
For a reaction at 37°C, a 5.94 kJ/mole decrease in ΔG changes K by a factor of which of the following?
In cells, lower SA to V ratios are not adaptive
Given your understanding of the "rules" of cell size, which statement best reflects the results shown in Figure 2?
paralogs
Homologous genes are defined as two genes that evolved from a common ancestor gene. Homologs can further be defined a paralogs or orthologs. In brief, orthologs are homologous genes that are the result of a speciation event; paralogs are homologous genes that are the result of gene duplication. Consider this diagram and then indicate whether genes A and B are paralogs or orthologs (fill in the blank).
All biological structures generate and maintain order at every level
How is it that organisms, through various syntheses, do not defy the second law of thermodynamics?
a hydrogen atom of one water molecule and an oxygen atom of another
In water, hydrogen bonds can form between which of the following?
It is false, because some cells lose the ability to replicate their DNA and divide.
Is the following statement true or false, and why? Within a developed multicellular organism, all cells possess the ability to divide and do so regularly.
false All bacteria DO NOT have the same DNA
Is the following statement true, false, or impossible to determine? Like the differentiated cells in an individual plant or animal, all bacteria have the same DNA.
by an ancestral eukaryotic cell before the lines that led to animal cells, plant cells, and fungi diverged
Mitochondria are essentially the same in all eukaryotes, including plants, animals, and fungi. Based on this observation, how were mitochondria most likely acquired?
transcription
RNA synthesis
Because radioisotopes of an element differ only in the number of neutrons, they still behave the same way chemically.
Radioactive isotopes (radioisotopes) of elements are commonly used in biological experiments as tracers to follow and detect molecules of interest. For example, photosynthetic intermediates produced during carbon dioxide conversion to sugars were detected by exposing algae to carbon dioxide containing a radioactive form of carbon. This radioactive carbon could be rapidly detected in molecules produced by the algae during carbon fixation and sugar production. Why can radioisotopes substitute for non-radioactive isotopes of elements in experiments?
Yeast. Round bubble-looking structures.
Saccharomyces cerevisiae
One of the reasons why there is a limit to the size of a cell is that the transport of materials across the plasma membrane best supports cell metabolism if
The cell surface to cell volume ratio is maintained at a consistent, higher value
The virus is 100 times smaller than its host cell
The human immunodeficiency virus (HIV) has a diameter of 100 nm. Considering this dimension (diameter), how many times smaller is this virus than it's host cell, a 10 micrometer diameter T lymphocyte?
protein
The most diverse and versatile class of macromolecules is _______
with dimensional analysis, it's 12.5 molecules
The phospholipid bilayer is about 5 nm thick (from polar head of one leaflet to polar head of the other leaflet). A water molecule has a diameter of about 4 Å. How many water molecules could line up along a protein channel that spans the membrane, end to end?
5 water molecules
The phospholipid bilayer is about 5nm thick (from polar head of one leaflet to polar head of the other leaflet). A water molecule has a diameter of about 4 Å. How many water molecules could line up along a protein channel that spans the membrane, end to end?
hydrogen bond
The type of non-covalent bond that allows for specific base pairing in double stranded DNA is _________ (fill in the blank below).
true
True or falase Within a molecule, or between molecules, a hydrogen bond may form between a hydrogen and a nearby electronegative atom (O, N), if that hydrogen is also covalently bonded to an electronegative atom.
The following statement about cells is NOT true:
Two cells with the same genome will be similar in size, appearance, and function
a nucleus and membrane-bound organelles
What do eukaryotic cells have that prokaryotes lack?
chloroplasts, beyond a doubt!
What does a plant cell have that an animal cell doesn't have?
salt
What is the best term to describe a chemical held together solely by ionic bonds?
sunlight
What is the origin of the energy that animals acquire by eating plants or other animals?
archaea
What organisms commonly colonize the hot acid of volcanic springs, the airless depths of marine sediments, the sludge of sewage treatment plants, the pools beneath the frozen surface of Antarctica, as well as the acidic, oxygen-free environment of a cow's stomach where they break down ingested cellulose and generate methane gas?
hydration stabilization (More water can bind ADP and Pi, than can bind to ATP) resonance stabilization electrostatic repulsion
What three features of ATP to ADP hydrolysis makes ATP have a high phosphoryl group transfer potential?
both the types of bonds that involve the sharing of electrons between atoms and the types of bonds that involve electrostatic interactions between atoms
What type(s) of bonds link together the components of a ribosome, as shown in the figure?
The different cells have different DNA.
When comparing liver cells and kidney cells within an organism, many differences can be observed and documented. Which of following is not a difference between liver cells and kidney cells in the same animal?
the lower graph. the lower KM, the greater the ES affinity
When given two graphed Km's, which depicts an enzyme substrate affinity that is higher than the other?
encoding genetic information
Which is not a function of proteins?
Mitochondria and chloroplasts have similar DNA.
Which is not evidence for the endosymbiotic origins of mitochondria and chloroplasts?
Chloroplasts are present in essentially all eukaryotic cells and in certain photosynthetic bacteria.
Which statement is not true of chloroplasts?
Mitochondria are not present in plant cells.
Which statement is not true of mitochondria?
they mix well with water
Which statement is true of hydrophilic molecules?
The heat released by an animal cell comes from the chemical-bond energy present in the food molecules it metabolizes.
Which statement is true?
All cells are formed by the growth and division of existing cells.
Which statement represents the cell theory?
amphipathic
Which term best describes a fatty acid?
single bond
Which type of covalent bond allows for rotation about the bond axis?
to attain a stable, filled valence shell
Why do atoms share electrons in a covalent bond?
electron microscope
Within the microscope image below, identify the type of microscopy used by dragging the correct label to the target in the image.
activation energy
a boost over an energy barrier before it can undergo a chemical reaction that moves it to a lower-energy (more stable) state
substrate
a molecule or ligand that an enzyme catalyzes
endosymbiotic theory
an evolutionary theory of the origin of eukaryotic cells from prokaryotic organisms
nonspontaneous reaction
anabolism is a __________
gram negative
bacteria that have a thin peptidoglycan layer in the cell wall and a second, outer membrane around the cell wall.
non-covalent bonds
bonds that are weaker, easily broken and formed, and longer in length
oligosaccharides
branched, small polymers of sugars joined by glycosidic bonds an essential component of cell-cell (molecule-molecule) recognition
ATP to ADP
energy released in breaking a phosphoanhydride bond
NADPH to NADP+
energy released in the form of elections and H
nonpolar bond
equal sharing of electron, where electronegativities of two atoms are similar or close together
unsaturated
glycerol separated
saturated
glycerol straight and linear
transition state
high energy areas that substrates must pass through to be converted to product
starch
nutritional polysaccharide Also called amylose Polymer of α glucose, branched and unbranched
glycogen
nutritional polysaccharide Polymer of α glucose, branched
Lysosomes
small, irregularly shaped organelles in which intracellular digestion occurs, releasing nutrients from ingested food particles into the cytosol and breaking down unwanted molecules for either recycling within the cell or excretion from the cell.
peroxisomes
small, membrane-enclosed vesicles that provide a sequestered environment for a variety of reactions in which hydrogen peroxide is used to inactivate toxic molecules.
cellulose
structural polysaccharide Polymer of glucose, unbranched (α and β)
glycosaminoglycans
structural polysaccharide unbranched polymers of repeating disaccharide units
spontaneous
the free energy change (Delta G) for a chemical reaction is less than zero
true Living organisms, and the order they create, is made possible by a constant input of energy -some of the energy is used to do the work of the cell, including syntheses, and the rest is lost as heat; heat released into the environment allows the overall entropy of the universe to increase (thus obeying the second law of thermodynamics).
true or false Living organisms, and the order they create, is made possible by a constant input of energy -some of the energy is used to do the work of the cell, including syntheses, and the rest is lost as heat; heat released into the environment allows the overall entropy of the universe to increase (thus obeying the second law of thermodynamics).
true The two types of reversible inhibitors are competitive inhibitors and non-competitive inhibitors.
true or false The two types of reversible inhibitors are competitive inhibitors and non-competitive inhibitors.
true the lower the Kd, the greater the affinity the two molecules, R and L, have for each other(the concentration of RL is greater than the concentrations of R and L alone; likewise, the higher the Kd, the lesser the affinity the two molecules, R and L, have for each other.
true or false the lower the Kd, the greater the affinity the two molecules, R and L, have for each other(the concentration of RL is greater than the concentrations of R and L alone; likewise, the higher the Kd, the lesser the affinity the two molecules, R and L, have for each other.
polar bond
unequal sharing of electrons, where the positive charge is concentrated toward one atom in the molecule (the positive pole) and the negative charge is concentrated toward another atom (the negative pole)
many types of proteins (glycoproteins) many types of lipids (glycolipids)
what are oligosaccharides covalently attached to?
cytoplasm
where does translation take place?
