Hbio Unit 2 quiz q&a:
What mitochondrial feature enhances cellular respiration?
Cristae. Explanation: These folds increase the surface area of the membrane, allowing more proteins to be embedded and thus enhancing the ability of the mitochondrion to produce ATP.
FUN FACT: FLIP.
Even prokaryotic cells have ribosomes
Light is _____ energy, which is converted by plants into molecules, which possess _____ energy
Kinetic ... Chemical: Explanation: Light is kinetic energy, and molecules possess chemical energy. Chemical energy refers to the potential energy that can be released during chemical reactions.
Which of the following cytoplasmic structures functions in the transport of vesicles from the endoplasmic reticulum to the Golgi apparatus?
Microtubules. Explanation: Vesicles travel along microtubules as they move from one part of the cell to another.
The eyepiece of a light microscope has a magnification level of 10x. If you were looking at a paramecium under the lowest-power objective (4x), what would be the total magnification of the microscope at this setting?
40x. Explanation: Total magnification is equation: (4x) × (10x) = 40x.
A 100 mm x 100 mm x 100 mm cell has a surface area that is _____ and a volume that is _____. A second cell, that is 10 mm x 10 mm x 10 mm, has a _____ surface-to-volume ratio when compared to the first cell.
60,000 mm2 ... 1,000,000 mm3 ... larger. Explanation: The smaller cell has a larger surface (600 mm2) to volume (1,000 mm3) ratio. This accounts for why most cells are microscopic.
A disease called primary ciliary dyskenisia is characterized by abnormal ciliary movements. In these cilia, microtubule functioning is disrupted due to microtubules missing an essential component. This disease could be caused by __________.
A lack of dynein proteins. Explanation: Dynein is part of the proteins that make up microtubules. Defects in dynein proteins are responsible for this disease.
What is an accurate comparison of active transport and facilitated diffusion?
Active transport moves solutes against their concentration gradient; facilitated diffusion moves substances down their concentration gradient. Explanation: Active transport involves moving solutes against their concentration gradient. Facilitated diffusion moves solutes down their concentration gradient. Active transport requires the use of ATP, whereas facilitated diffusion does not.
Finish the sentence: A Salt Lake has an average salinity seven times higher than the oceans. Very few multicellular organisms live in this harsh environment. An example is the brine shrimp, which must devote a large portion of its metabolic energy to osmoregulation. These brine shrimp must _____.
Actively pump water back into their cells to counter its loss due to osmosis. Explanation: A cell (in this case, cells within the body of a brine shrimp) will experience a net output of water in a hypertonic environment. For cells to prevent shriveling, they must actively recapture water from their surroundings.
Antibiotics—for example, penicillin—cannot be used to treat viral infections, such as the common cold. Why?
Antibiotics inhibit enzymes that are essential to the survival of bacteria only. Explanation: Antibiotics are designed specifically to fight bacterial infections. Many antibiotics, such as penicillin, inhibit a bacterial enzyme that is used to make protective cell walls. Neither animals nor viruses make such an enzyme and therefore are mostly unaffected by antibiotics.
Finish the sentence: Cells store energy that they use for work in the _____
Arrangement of atoms within molecules. Explanation: The bonds holding atoms together also contain potential energy, energy the cell harnesses when bonds are broken during metabolism.
Which is a typical function of lysosomes?
Breaking down of damaged organelles, such as chloroplasts. Explanation: Lysosomes do break down damaged organelles; lysosomes are rarely found in plant cells.
What allows simple molecules to assemble into more complex molecules, and also disassemble, in cells but not in other, nonbiological environments?
Cells couple energy-releasing reactions to energy-requiring reactions. Explination: One of the many things cells do well is the linking of metabolic reactions in ways that allow an energy-yielding reaction to be coupled to an energy-requiring reaction. ATP molecules are the key to energy coupling.
Many researchers think that the first eukaryotic cells obtained energy for life-sustaining functions from organic compounds. Given this information, what organelle is most likely appeared last in eukaryotic cells?
Chloroplast. Explanation: If the earliest eukaryotic cells had contained chloroplasts, they would not have had to obtain organic compounds through food.
Azidothymidine (AZT) is an antiretroviral drug used in the treatment of HIV. It shares a structural similarity to a nucleotide. What might be the mode of action for this drug?
Competitive inhibition. Explanation: AZT and the nucleotide compete for the active binding site. When AZT binds to an enzyme known as reverse transcriptase, it blocks the replication of the genetic material of HIV.
Frequently, transplanted organs are rejected by the recipient's body. How is this reaction related to plasma membranes?
Each person has a unique set of carbohydrate chains attached to his or her plasma membranes. Explanation: When cells with unrecognized carbohydrate chains are placed in a person, his or her immune system attacks the foreign cells as though they were infectious agents.
Which technique allowed scientists to figure out that all cells, and not just muscle cells, contained actin filaments?
Electron microscopy. Explanation: In the 1960s, staining actin filaments and visualizing them with an electron microscope allowed scientists to discover that these structures are present in all cells.
Where are chlorophyll molecules located within the chloroplasts?
Embedded in the thylakoid membrane. Explanation: Chlorophyll molecules are embedded within the thylakoid membrane, which is the most extensive membrane system within plant cells.
Which statement regarding enzyme function is true?
Excessive salt ions can cause an enzyme to denature. Explanation: Few enzymes can tolerate extremely salty conditions, because the salt ions interfere with some of the chemical bonds that maintain protein structure.
In a theoretical world where all things are possible, how could you increase the amount of energy that could be stored in a molecule of ATP?
Increase the negative charge of each phosphate group. Explanation: Because the high energy of ATP hydrolysis depends on the strong charge repulsion between the negatively charged phosphates, anything that increases this repulsion would also increase the energy liberated when ATP is broken down to ADP + P.
What changes would you expect to see in the liver cells of someone suffering from chronic alcoholism?
Increased levels of endoplasmic reticulum activity. Explanation: The smooth endoplasmic reticulum of liver cells has enzymes that are involved in alcohol metabolism. This organelle is affected in the liver cells of alcoholics.
Finish the sentence: New drugs are being developed to lower levels of circulating cholesterol. A successful drug would be one that _____
Increases the rate of LDL receptor-mediated endocytosis. Explanation: Because cholesterol levels in the blood reflect the balance of, addition to, and removal of cholesterol, anything that tips the balance in favor of removal will lower the concentration of circulating cholesterol. Increasing LDL receptor-mediated endocytosis will have exactly this effect.
What component of the cell membrane connects signals from the outside of the cell with the inside of the cell and vice versa?
Integrins. Explanation: Integrins span the membrane and integrate signals, transmitting information between the extracellular matrix and the cytoskeleton of the cell.
The cells of a person with adrenoleukodystrophy (ALD) swell with a buildup of fatty acids. In other words, fatty acids are not being broken down. Which organelle is most likely failing to function correctly?
Lysosome. Explanation: This organelle functions to remove unwanted or unneeded material from the cell.
Which of the following organelles is found only in animal cells and NOT in most plant cells?
Lysosome. Explanation: This organelle is found only in animal cells. Most plant cells do not have a lysosome.
Macrophages are white blood cells that roam the body searching for invading microbes. Inside macrophage vacuoles these invaders are destroyed. How do the microbes get inside the macrophages?
Microbes are engulfed into the macrophage via phagocytosis. Explanation: Phagocytosis is a type of endocytosis in which a cell takes macromolecules, other cells, or particles packaged in vacuoles into its cytoplasm.
Which cell structure is responsible for metabolism?
Mitochondrion. Explanation: Mitochondria are involved in the process of converting the chemical energy of food to ATP.
You have three different amino acids, four different sugars, and two different ions. How many different proteins does the cell need to move these molecules across the plasma membrane using facilitated transport?
Nine. Explanation: The specificity of transport proteins for the materials they transport is exactly like the specificity of enzymes for their substrates. Therefore, if there are nine different substances to be transported by facilitated diffusion, this almost certainly involves nine different transport proteins.
The synthesis of an amino acid follows this pathway: precursor A → intermediate B → amino acid C. Each reaction is catalyzed by a different enzyme. This metabolic pathway is controlled by feedback inhibition with amino acid C inhibiting the conversion of precursor A to intermediate B. Amino acid C acts as a _____ of the first enzyme in the pathway.
Noncompetitive inhibitor. Explanation: In this form of feedback inhibition, the end product of the pathway inhibits an early-acting enzyme. Because the product of the pathway and the substrate of the early-acting enzyme are very different in structure, competitive inhibition is unlikely as this involves binding of an inhibitor to the active site. Much more plausible is noncompetitive inhibition in which the inhibitor binds to a site on the enzyme that is different from the active site.
Finish the sentence: You have identified a new organism. It has ribosomes, plasmodesmata, and cell walls made of cellulose. This new organism is most likely a(n) __________
Plant. Explanation: Plant cells have cell walls that are made of cellulose and plasmodesmata, which are cytoplasmic channels that connect adjacent cells.
Which plant structure is most like gap junctions in animal cells?
Plasmodesmata. Explanation: Plasmodesmata form channels between adjacent plant cells which have a similar function to gap junctions in animal cells.
Which of the following would distinguish a bacterial cell from an animal cell?
Presence of a cell wall. Explanation: Prokaryotic cells have cell walls. Some eukaryotic cells do also, but animal cells do not.
Overall, membranes seem to have a great deal in common, but on closer inspection it is revealed that membranes of different cells have unique properties. What is the primary component of membranes that gives membranes cell-specific properties?
Proteins. Explanation: There is a large variety of proteins, and it is differences in these widely varying molecules that give a particular membrane its unique properties.
Finish the sentence: When placed in a hypotonic environment, where the solute concentration is below that of the cell, a houseplant will _____
Remain standing upright. Explanation: Being in a hypotonic environment is good for the plant. The water balance in plants is remarkably different. In an isotonic solution plant cells will look flaccid (limp), and in a hypotonic environment they will be turgid (firm). The cell wall allows the plant cell to balance the osmotic pressures inside the cell.
Pancreatic cells produce large amounts of protein. About how many ribosomes would you expect there to be in a pancreatic cell?
Several million. Explanation: There are several million ribosomes in cells, such as the cells in the pancreas that produce digestive enzymes.
Which tissue would likely contain large amounts of anchoring junctions?
Stomach tissue. Explanation: Stomach tissue is muscle tissue that initiates movement (churning of food) and expansion.
The plasma membrane would fit into which general function category?
Support, movement, and communication. Explanation: The plasma membrane is an important structure for cell communication with the external environment.
The hydrolysis of DNA into nucleotides constitutes an exergonic reaction. Yet, DNA is quite stable. Why is this the case?
The activation energy required to initiate this reaction is seldom reached. Explanation: An input of energy, termed the activation energy, is required to initiate this reaction
What drives osmosis?
The difference in water concentration across a selectively permeable membrane. Explanation: The driving force for osmosis is water's concentration gradient across a selectively permeable membrane. Differences in solute concentration across a membrane create water concentration differences, but solute concentration differences do not directly drive osmosis.
The eukaryotic cell has multiple membrane-enclosed compartments. This evolutionary innovation provides what advantage to the cell?
The different membrane-enclosed spaces allow different parts of the cell to perform specific functions. Explanation: The membranes that surround organelles make it possible to construct very different chemical environments within and on the surface of each of these organelles.
What controls the direction of a molecule, such as oxygen, involved in passive transport?
The direction of the oxygen concentration gradient. Explanation: The direction a material moves in passive transport is determined solely by the material's concentration gradient, with material diffusing from regions of higher concentration to regions of lower concentration.
What happens to the chemical energy that is extracted from molecules by cellular activities but that is not used for cellular work?
The energy contributes to the entropy of the system. Explanation: The second law of thermodynamics states that in any energy transformation, the overall disorder of the universe increases. Most often, this disorder comes in the form of thermal molecular motion (heat), which is a form of energy that is not lost but cannot be harnessed for work.
What is the relationship between the Golgi apparatus and the plasma membrane?
The finished products of the Golgi apparatus may leave the cell through vesicles that fuse with the plasma membrane. Explanation: Transport vesicles from the Golgi move to the plasma membrane for export. In some cases the finished products become part of the plasma membrane or part of another organelle.
What is an essential difference between animal and plant cells that could explain how a plant cell can withstand this expansion of the central vacuole?
The plant cell wall provides a more rigid structure. Explanation: The plant cell can use the central vacuole for growth because the cell wall is rigid. Example: One function of the central vacuole in plant cells is facilitating cell growth: the central vacuole absorbs water and increases in size, expanding the volume and size of the plant cell while doing so. Animal cells, however, do not grow by this method.
How are cell surface proteins exported out of the cell?
The protein is folded, then packaged for transport to the Golgi apparatus. Explanation: The protein structure is critical to the normal function of the protein. Once folded, then it will be transported to the Golgi apparatus via a transport vesicle.
Sucrose, is quite stable, and left on its own at room or even human body temperature, breakdown occurs very slowly. The breakdown of sucrose into the simple sugars fructose and glucose is an exergonic reaction. Sucrase, an enzyme, can increase the reaction rate at least one-million-fold. How does the net amount of energy released during the breakdown of sucrose compare between a spontaneous reaction and one catalyzed by sucrase?
The sucrase-catalyzed reaction releases the same amount of energy as the spontaneous reaction. Explanation: Enzymes reduce activation energy. The difference in energy between reactants and products remains constant regardless of the rate of the reaction.
What do the rough endoplasmic reticulum, Golgi apparatus, and lysosomes have in common?
They are constructed of interrelated membranes. Explanation: Each of these organelles is a member of the endomembrane system and is constructed of the same type of membrane.
If you wished to clearly observe the organelles inside of a white blood cell, which type of microscope would you choose?
Transmission electron microscope. Explanation: This type of microscope allows you to view internal structures of living cells.
Which of the following structures is essential for the successful operation of the endomembrane system?
Transport vesicles. Explanation: Transport vesicles provide a means for moving materials from one part of the endomembrane system to another.
A pharmaceutical company wishes to focus on an enzyme to develop new medications. What type of study would be of the greatest benefit?
Understanding the enzyme's structure would help pharmaceutical companies design molecules that fit to the binding site and alter activity. Explanation: The net yield of any quantity is the difference between what's gained and what's put in. In the case of the sucrase-catalyzed reaction and spontaneous (noncatalyzed) reactions, the trip up to and down from the activation energy barrier yields nothing, no matter how far the journey; all that matters is the difference in energy between product and reactant, something that remains constant, regardless of the rate of the reaction.
What substance is transported by aquaporins
Water. Explanation: Aquaporins are a newly discovered class of transport proteins that transport water in cells with very high water permeability needs. (How to remember): Aqua means water
finish the sentence: In an oil-based, nonpolar environment, phospholipids would arrange themselves so that they __________
Would stay together but in a reverse orientation, with their tails projecting outward. Explanation: The fatty acid tails of a phospholipid remain nonpolar and the phosphate heads remain polar regardless of the surrounding environment. In an oily environment, the tables are turned relative to water; the polar heads will cluster together to avoid exposure to the oil, and the nonpolar tails will project outward into the nonpolar, oil-based surroundings.
