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001 2.0 points Below are two pairs of events that might have occurred during the origin and evolution of life on the early earth environment. Event I: Photosynthetic (photoautotro- phic) cyanobacteria came into existence Event II: chemosynthetic (chemoautotro- phic) bacteria came into existence Select one of the choices given below based on the relative time of each of these pairs of events given in following question.
- Events I and II occurred simultane- ously.
- No such events occurred.
- It does not matter which happened first.
- Event II occurred before Event I. correct
- Event I occurred before Event II.
Explanation:
002 2.0 points Consider the following events in the origin of life: I. synthesis of amino acids and sugars; II. systhesis of protobiont-like structures; III. availability of basic elements C, H, O, and N; IV. formation of macromolecules. What is the correct sequence?
- I, II, IV, III
- II, IV, III, I
- IV, II, I, III
- II, I, III, IV
- III, IV, I, II
6. IV, II, III, I
7. I, III, II, IV
8. II, I, IV, III
- III, I, IV, II correct
- III, II, I, IV
Explanation: The correct sequence is
- Availability of basic elements C, H, O, and N;
- Synthesis of amino acids and sugars;
- Formation of macromolecules; and
- Synthesis of protobiont-like structures.
003 2.0 points Which of the following was demonstrated by the Miller-Urey experiment?
- Organic molecules important to life could have been formed from a vast array of simple chemicals. correct
- Life was formed in “premordial soup.”
- Life can be started experimentally in the laboratory.
- Life began on the pre-biotic Earth 3. billion years ago.
- Life began in the oceans.
Explanation: The experiment involved running an elec- tric current through a mixture of methane, ammonia, hydrogen, and water and resulted in the formation of organic molecules includ- ing amino acids.
004 2.0 points Which of the following pairs does not match?
- nucleolus : ribosomal RNA
- nucleus : DNA replication
- cytoskeleton : microtubules
- lysosome : protein synthesis correct
- cell membrane : lipid bilayer
Explanation: Lysosome and protein synthesis do not match; lysosome has different functions and does not take part in protein synthesis. It con- tains hydrolytic enzymes that hydrolyze pro- teins, polysaccharides, fats and nucleic acids.
005 2.0 points Which of the following organelles carries out the biosynthesis of oils and detoxifies drugs and poisons?
- ribosomes
- smooth endoplasmic reticulum correct
- mitochondria
- contractile vacuoles
- lysosomes
Explanation: The smooth ER of various cell types func- tions in diverse metabolic processes such as synthesis of lipids, metabolism of carbohy- drates and detoxification of drugs and poi- sons.
006 2.0 points All the following are true of both Mitochon- dria and Chloroplasts EXCEPT
- Both contain their own DNA and synthe- size some proteins.
- Both import some proteins from the cy- toplasm.
- Both are inherited in a maternal fashion.
- The major function of both organelles is cellular respiration. correct
- Both have double membrane structures.
- Both replicate autonomously (indepen- dent of cell division).
Explanation: Chloroplasts and mitochondria have their own DNA, make their own proteins and im- port some proteins from cytosol. Both have double membrane and they are maternally in- herited. Chloroplasts perform photosynthesis and amino acid biosynthesis. Mitochondria on the other hand perform respiration.
007 2.0 points The most common route for membrane flow in the endomembrane system is which of the following?
- Golgi → lysosome → ER → plasma mem- brane
- nuclear envelope → lysosome → Golgi → plasma membrane
- tonoplast → plasma membrane → nuclear envelope → smooth ER
- ER → chloroplasts → mitochondrion → cell membrane
- rough ER → vesicles → Golgi → vesicles → plasma membrane correct
Explanation: The innermost of the endomembrane sys- tem is the nuclear envelope and the outermost is plasma membrane. Next to and adjoining the nuclear envelope is ER and vesicle fol- lowed by Golgi bodies.
008 2.0 points Consider the four steps in an experimental procedure done to determine the amount of rRNA in a liver sample: I. Purify the mRNA from other molecules such as proteins and DNA; II. Break the liver cells by grinding them in a suitable buffer;
012 2.0 points An antibiotic such as tetracycline inhibits bacterial ribosomes but not eukaryotic ribo- somes. What could be a plausible reason for this difference? The prokaryotic ribosomes differ from the eukaryotic ones in
- numbers limiting in prokaryotes.
- their net electric charge.
- their function of making proteins.
- their shape and having two subunits.
- their RNA and protein sequence. cor- rect
Explanation:
013 2.0 points It is discovered that a new strain of bacteria is protected from the hydrolytic properties of lysozymes, commonly found in our tears and saliva. The reason for this newfound resistance could be
- significant change in the cell wall compo- sition and structure. correct
- an increased number of pili.
- plasmamembrane becoming impermeable to any molecules.
- increased number of lysosomes.
- changes in the structure of the number of ribosomes.
Explanation: Lysozymes degrade the modified polysac- chardide NAM-NAG found in the cell walls of bacteria. Any changes in cell wall composi- tion or structure may affect the effectiveness of lysozyme and the bacteria may no longer be suceptible to that enzyme.
014 2.0 points
You would not expect to find RNA in which of the following structures?
- Nucleus
- Prokaryotic cell
- Ribosome
- Vacuole correct
- Mitochondrion
Explanation: Mitochondrions are known to contain their own set of genetic information separate from the cell. The nucleus is where RNA originates. Ribosomes are made from RNA and protein, and additionally it is the structure that trans- lates mRNA into proteins. Prokaryotic cells contain a nucleoid which is a region composed of genetic material such as RNA. Vacuoles are the only structures containing enzymes that would degrade RNA rendering it useless, thus it would be a loss of energy for the cell to make any form of RNA in the vacuole just for it to be degraded.
015 2.0 points How does the surface area-to-volume ratio of a 1-mm cube compare to the surface area-to- volume ratio of a 3-mm cube?
- Increasing the volume increases the ra- tio.
- The ratio does not change.
- The 3 mm cube has a higher ratio.
- The ratio decreases as the cube becomes larger. correct
- The ratio increases as the cube becomes larger.
Explanation: 1-mm cube: Surface area = (Length) × (Width) × (6 sides) = 6 mm^2
Volume = (Length) × (Width) × (Height) = 1 mm^3 3-mm cube: Surface area = (3 mm) × (3 mm) × 6 sides = 54 mm^2 Volume = (3 mm) × (3 mm) × (3 mm) = 27 mm^3 Ratio of the 1-mm cube (6:1) is 3 times larger than the 3-mm cube (2:1).
016 2.0 points Of the following plant cell structures, which is most likely to have the greatest volume?
- Vacuole correct
- Chromosome
- Glyoxysome
- Lysosome
- Ribosome
Explanation:
017 2.0 points One of the relationships that exists between ribosomes and lysosomes is that
- lysosomes are located near ribosomes on the surface of the endoplasmic reticulum.
- lysosomes are produced by ribosomes and therefore contain proteins that were synthe- sized at the ribosomes.
- ribosomes produce enzymes that could be stored in lysosomes. correct
- lysosomes produce enzymes used in ribo- somes.
- ribosomes produce lipids that could be stored in lysosomes.
Explanation: Ribosomes produce proteins, some of which are enzymes that may be used by a lysosome.
018 2.0 points Placing a plant cell in a hypotonic solution will cause the cell to
- burst.
- divide.
- not change at all.
- shrivel.
- swell. correct
Explanation: In hypotonic solutions, there is less solute (and therefore more water) outside the cell; therefore, water will rush into the cell. Plant cells prefer this environment, and use the wa- ter to keep the stem upright and rigid. Unlike animal cells, plant cells have cell walls to pre- vent the cell from bursting.
019 2.0 points Suppose you genetically engineered fungi that can rapidly digest agricultural waste to simple sugars in order to make ethanol. These fungi should be able to produce high amounts of
- chitinase.
- lysozyme.
- phosphate.
- cellulase. correct
- alcohol dehydrogenase.
Explanation:
020 2.0 points The plasma membranes of winter wheat are able to remain fluid when it is extremely cold by
- closing protein channels.
- using fatty acids with longer tails.
high concentration of dissolved material cor- rect
Explanation: explanation
025 2.0 points One result of the movement of ions through ion channels is the creation of a membrane potential.
- a charge imbalance across the plasma membrane. correct
- the difference in ATP concentrations on either side of the plasma membrane.
- the capacity for active transport.
- the ability of macromolecules to recognize and adhere to one another.
- the difference in ion concentrations on either side of the plasma membrane.
Explanation:
026 2.0 points A characteristic of plasma membranes that helps them fuse during vesicle formation and phagocytosis is the
- ratio of one protein molecule for every 25 phospholipid molecules.
- capacity of lipids to associate and main- tain a bilayer organization. correct
- constant fatty acid chain length and de- gree of saturation.
- asymmetrical distribution of membrane proteins.
- ability of phospholipid molecules to flip over and trade places with other phospholipid molecules.
Explanation:
027 (part 1 of 2) 2.0 points
Which structure in A B
C
D
E
is responsible for making the ATP needed for active transport?
- E
- D
- C correct
- B
- A
Explanation: A: nucleus B: rough ER C: mitocondrion D: golgi apparatus E: cell membrane
028 (part 2 of 2) 2.0 points A steroid hormone can stimulate a cell to produce specific proteins, and hence high amounts of particular mRNAs. In the above cell, where would mRNA be made in response to the stimulus by a steroid hormone?
- B
- D
- A correct
- E
- C
Explanation:
029 2.0 points Intracellular mediators (also called secondary messengers) alter the behavior of proteins by binding with them, thus altering their shape. Which of the following are two widely-used secondary messengers?
- cAMP and G proteins
- cAMP and calcium correct
- cAMP and calmodulin
- cAMP and potassium
- cAMP and ATP
Explanation: Recall
030 2.0 points How does paracrine signaling work by acting on target cells?
- It involves secreting cells act on a target in the vicinity cells by discharging a local regulator into the extracellular fluid. correct
- It involves mating factors attach to target cells and cause production of new paracrine cells.
- It occurs only in paracrine yeast cells.
- It requires nerve cells to release a neuro- transmitter into synapse.
- It is characteristic of plants and not of animals.
Explanation: Paracrine signaling is a type of local signal- ing in which one class of local regulators in an- imals can simultaneously receive and respond to the molecules of growth factors produced by a single cell in their vicinity. It releases a local regulator into the extracellular fluid.
031 2.0 points The transduction process is usually initiated
- after the target cell divides.
- when the hormone is released from the gland into the blood.
- after the third stage of cell signaling is completed.
- when the signal molecule changes the re- ceptor protein. correct
- when the chemical signal is released from the α cell. Explanation: The transduction process starts when the signal molecule changes the shape of the re- ceptor protein.
