1.
Plasma membranes are a feature of ______.
Correct Answer
C. All cells
Explanation
Plasma membranes are a feature of all cells because they are essential for maintaining the integrity and functionality of the cell. The plasma membrane acts as a selective barrier, regulating the movement of substances in and out of the cell. It also plays a crucial role in cell signaling and communication with the external environment. Therefore, plasma membranes are present in both prokaryotic and eukaryotic cells, as well as in plant and animal cells.
2.
Which of the following is NOT a component of plasma membranes?
Correct Answer
B. Glycosylated nucleic acids
3.
Which of the following are true of the plasma membrane?
Correct Answer
E. B, C, and D
Explanation
The plasma membrane is composed of an extracellular and intracellular layer of phospholipids, which is true. The membrane contains peripheral proteins, which are proteins that are not embedded in the lipid bilayer but are attached to either the inner or outer surface of the membrane. Integral proteins, on the other hand, span through the membrane, meaning they are embedded within the lipid bilayer. The membrane also contains glycolipids and glycoproteins, which are molecules that have carbohydrates attached to them. Therefore, options B, C, and D are all true statements about the plasma membrane.
4.
The pathway from the ER to the Golgi to the plasma membrane is called the ______.
Correct Answer
D. Secretory pathway
Explanation
The pathway from the ER to the Golgi to the plasma membrane is called the secretory pathway. This pathway is responsible for the transport and secretion of proteins and other molecules from the ER to their final destination at the plasma membrane. It involves the sorting and packaging of proteins in the Golgi apparatus before they are transported to the cell surface. The secretory pathway is essential for various cellular processes, including the secretion of hormones, enzymes, and other signaling molecules.
5.
The process of covalently attaching a carbohydrate to a protein or lipid is ______.
Correct Answer
A. Glycosylation
Explanation
Glycosylation is the process of covalently attaching a carbohydrate to a protein or lipid. This process plays a crucial role in various biological functions, such as protein folding, stability, and recognition. It helps in determining the structure and function of the glycoprotein or glycolipid. Glycosylation can occur in the endoplasmic reticulum and Golgi apparatus, where specific enzymes catalyze the attachment of carbohydrates to proteins or lipids. This process is essential for cellular communication, immune response, and many other biological processes. Therefore, glycosylation is the correct answer for the given question.
6.
Which of the following are 2 major functions of the SRP protein/RNA complex?
Correct Answer
B. Recognizes the ER signal sequence and pauses translation AND SRP binds to receptor in ER membrane, which docks the ribosome over a channel protein
Explanation
The SRP protein/RNA complex has two major functions. Firstly, it recognizes the ER signal sequence and pauses translation. This helps in directing the ribosome to the endoplasmic reticulum (ER) for protein synthesis. Secondly, the SRP binds to a receptor in the ER membrane, which then docks the ribosome over a channel protein. This allows for the efficient translocation of the growing polypeptide chain into the ER lumen.
7.
Facilitated diffusion but not passive diffusion requires energy.
Correct Answer
B. False
Explanation
Facilitated diffusion is a type of passive transport that does not require energy. It involves the movement of molecules across a membrane with the help of specific carrier proteins. These proteins facilitate the movement of molecules down their concentration gradient, without the need for energy input. Therefore, the correct answer is False.
8.
The following solutes have very low permeability through the plasma membrane.
Correct Answer
C. Charged polar molecules and macromolecules
Explanation
Charged polar molecules and macromolecules have very low permeability through the plasma membrane because they are larger in size and have charge, which makes it difficult for them to pass through the hydrophobic lipid bilayer of the membrane. The hydrophobic interior of the membrane repels charged molecules, while the large size of macromolecules prevents them from passing through the small pores of the membrane. Therefore, these solutes have limited ability to diffuse across the plasma membrane.
9.
Water can freely diffuse through animal cell membranes.
Correct Answer
B. False
Explanation
Water can freely diffuse through animal cell membranes. False. Animal cell membranes are selectively permeable, meaning they allow certain substances to pass through while restricting others. While small water molecules can pass through the lipid bilayer of the cell membrane, the process is not completely free or unregulated. The movement of water across the membrane is facilitated by specialized channels called aquaporins, which control the flow of water in and out of the cell.
10.
Which of the following organelles would become more active when a cell is induced to produce more protein secretions?
Correct Answer
B. Nucleus, RER, Golgi, mitochondria
Explanation
When a cell is induced to produce more protein secretions, the nucleus becomes more active because it contains the DNA that encodes the instructions for protein synthesis. The rough endoplasmic reticulum (RER) becomes more active as it is responsible for protein synthesis and modification. The Golgi apparatus also becomes more active as it processes and packages proteins for secretion. Additionally, the mitochondria become more active as they provide the energy needed for protein synthesis. Therefore, the correct answer is nucleus, RER, Golgi, mitochondria.
11.
Approximately 75% of all genes encode transmembrane proteins.
Correct Answer
B. False
Explanation
Approximately 25% of all genes encode transmembrane proteins.
12.
Which of the following is the major lipid found in membranes?
Correct Answer
B. Phospholipids
Explanation
Phospholipids are the major lipid found in membranes. They are composed of a hydrophilic head and hydrophobic tails, which allows them to form a bilayer structure in cell membranes. This arrangement provides a barrier that separates the internal environment of the cell from the external environment. Phospholipids also play a role in cell signaling and transport of molecules across the membrane. Steroids, cholesterol, triglycerides, and saturated fatty acids are also lipids, but they do not make up the majority of lipids in membranes.
13.
Which of the following is NOT true of the plasma membrane?
Correct Answer
E. The extracellular and intracellular layer of leaflets are highly symmetrical
Explanation
The extracellular and intracellular layer of leaflets in the plasma membrane are not highly symmetrical. The plasma membrane is composed of an extracellular and intracellular layer of phospholipids, and it contains peripheral proteins, glycolipids, and glycoproteins. Integral proteins span through the membrane, but the symmetry of the leaflets is not a characteristic of the plasma membrane.
14.
Scientists unearth a Wooly Mammoth from the Siberian Ice Sheath and discover that a eukaryotic "amoeba"-like cell is still alive. Which component of the cell membrane might contribute to maintaining the fluidity of plasma membranes under freezing conditions?
Correct Answer
C. High levels of unsaturated fatty acyl tails within the lipid bilayer
Explanation
High levels of unsaturated fatty acyl tails within the lipid bilayer might contribute to maintaining the fluidity of plasma membranes under freezing conditions. Unsaturated fatty acids have double bonds in their carbon chains, which create kinks in the structure. These kinks prevent the fatty acid chains from packing closely together, making the membrane more fluid and flexible. In freezing conditions, maintaining fluidity is important to prevent the membrane from becoming rigid and losing its function. Therefore, high levels of unsaturated fatty acyl tails would help the cell membrane remain fluid even in freezing temperatures.
15.
The movement of water across a semipermeable membrane to balance solute concentrations is called osmosis and requires energy output.
Correct Answer
B. False
Explanation
Osmosis is the movement of water across a semipermeable membrane to balance solute concentrations, but it does not require energy output. In osmosis, water molecules move from an area of lower solute concentration to an area of higher solute concentration, in order to equalize the concentration on both sides of the membrane. This process occurs passively, without the need for energy input. Therefore, the correct answer is False.
16.
Carbohydrates of the plasma membrane ____.
Correct Answer
E. All of the above
Explanation
Carbohydrates of the plasma membrane are associated with a protein or lipid, meaning they are attached to either a protein or a lipid molecule. They are also located on the outer surface of the plasma membrane, making them accessible for interactions with other cells. Additionally, these carbohydrates can function as cell markers for recognition by other cells, allowing for cell-cell communication and signaling. Therefore, the correct answer is "all of the above" as all the statements are true.
17.
A transmembrane protein in the plasma membrane is glycosylated at two sites in the polypeptide sequence. One site is Asn-Val-Ser and the other is Asn-Gly-Thn. Where in the protein would you expect these two sites to be found?
Correct Answer
E. A and B
Explanation
The correct answer is A and B. The glycosylation sites are found in hydrophilic regions that project into both the extracellular environment and the cytosol. This means that the protein has regions that are exposed to both the inside and outside of the cell, allowing for interactions with molecules in both compartments.
18.
What structural features of a membrane are major contributors to selective permeability?
Correct Answer
E. C and D
Explanation
The structural features of a membrane that are major contributors to selective permeability are the phospholipid bilayer and lipid exchange proteins. The phospholipid bilayer forms the basic structure of the membrane and consists of a hydrophilic head and hydrophobic tails, creating a barrier that only allows certain molecules to pass through. Lipid exchange proteins help transport specific lipids across the membrane, further contributing to the selective permeability of the membrane. Therefore, options C and D are correct as they include both of these important structural features.
19.
Both ______ and _______ are performed by transmembrane proteins, but the latter requires the input of some types of energy.
Correct Answer
B. Facilitated diffusion, active transport
Explanation
Facilitated diffusion is a type of passive transport where transmembrane proteins help in the movement of molecules across the cell membrane, but it does not require any input of energy. On the other hand, active transport is a process that also involves transmembrane proteins but requires the input of energy to move molecules against their concentration gradient. Therefore, the correct answer is facilitated diffusion, active transport.
20.
What term is used to describe the process in which water is moved across a membrane to try and equilibrate solute concentration on either side of the membrane?
Correct Answer
A. Osmosis
Explanation
Osmosis is the term used to describe the process in which water is moved across a membrane to try and equilibrate solute concentration on either side of the membrane. It is a passive process that does not require energy and occurs when there is a difference in solute concentration on either side of the membrane. The water molecules move from an area of lower solute concentration to an area of higher solute concentration, in an attempt to balance the concentration on both sides of the membrane.
21.
An electrochemical gradient occurs with solutes that have a net positive or negative charge.
Correct Answer
A. True
Explanation
An electrochemical gradient refers to the difference in electrical charge and concentration of ions across a membrane. It occurs when solutes with a net positive or negative charge are present. This is because charged particles are influenced by both electrical and chemical forces, leading to the establishment of a gradient. Therefore, the statement that an electrochemical gradient occurs with solutes that have a net positive or negative charge is true.
22.
If cells are in a _____ environment, this means that the concentration of a solute is ______ outside the cell than inside.
Correct Answer
E. A and B
Explanation
If cells are in a hypertonic environment, this means that the concentration of a solute is higher outside the cell than inside. Similarly, if cells are in a hypotonic environment, this means that the concentration of a solute is lower outside the cell than inside. Therefore, both options A and B are correct as they describe different scenarios of solute concentration relative to the cell.
23.
Secreted proteins most likely will pass through the _____, particularly if they are ____ prior to being moved out of the cell.
Correct Answer
C. Golgi apparatus, glycosylated
Explanation
Secreted proteins are synthesized in the rough endoplasmic reticulum (ER) and then transported to the Golgi apparatus. The Golgi apparatus is responsible for modifying and packaging proteins before they are transported out of the cell. One common modification that occurs in the Golgi apparatus is glycosylation, where sugar molecules are added to the protein. This modification helps in stabilizing the protein, aiding in proper folding, and targeting it to the correct destination. Therefore, the correct answer is Golgi apparatus, glycosylated.
24.
The process by which large macromolecules are transported outside the cell via vesicle formation at the Golgi apparatus and subsequent fusion with the plasma membrane is called ______.
Correct Answer
D. Exocytosis
Explanation
Exocytosis is the correct answer because it describes the process of large macromolecules being transported outside the cell. In exocytosis, vesicles are formed at the Golgi apparatus and then fuse with the plasma membrane, releasing their contents into the extracellular space. This process is essential for the secretion of proteins, hormones, and other molecules from cells. Facilitated diffusion and active transport involve the movement of molecules across the cell membrane but do not specifically refer to the transport of large macromolecules. Endocytosis, on the other hand, is the process by which substances are taken into the cell through the formation of vesicles.
25.
All cells of a multicellular organism may not respond in the same manner to a particular ligand that binds to a cell surface receptor. The difference in response may be due to _____.
Correct Answer
E. All of the above
Explanation
The correct answer is "all of the above". The difference in response of cells to a particular ligand can be due to multiple factors. The type of receptor that the cell expresses can determine how the ligand binds and activates signaling pathways. The type of signal transduction pathways that the cell expresses can further modulate the cellular response. Additionally, the affinity of the ligand for the receptor in a given cell type and the type of target proteins that the cell expresses can also influence the response. Therefore, all of these factors can contribute to the variation in cellular response to a ligand.
26.
When a cell secretes a signaling molecule that binds to receptors on neighboring cells of the same type as well as the same cell, this is called _____ signaling.
Correct Answer
A. Autocrine
Explanation
Autocrine signaling refers to a type of cell signaling where a cell secretes a signaling molecule that binds to receptors on both neighboring cells of the same type and the same cell that secreted it. This means that the signaling molecule acts on the cell that produced it, creating a feedback loop.
27.
A substrate binds an enzyme as a signal molecule binds a ______.
Correct Answer
C. Receptor
Explanation
A substrate binds an enzyme in a similar way that a signal molecule binds a receptor. Just as a substrate interacts with an enzyme to initiate a chemical reaction, a signal molecule interacts with a receptor to initiate a cellular response. Both processes involve specific binding and recognition between molecules, leading to a downstream effect.
28.
The benefit of second messengers in signal transduction pathways is _______.
Correct Answer
D. A and B
Explanation
Second messengers play a crucial role in signal transduction pathways by amplifying the original signal and increasing the speed of cellular response. They act as intermediaries between the extracellular ligands and the intracellular targets, allowing for a more efficient and rapid cellular response. Therefore, the correct answer is "A and B" as both amplification of the signal and an increase in the speed of a cellular response are benefits of second messengers in signal transduction pathways.
29.
A hormone binds a receptor and activates the cAMP signal transduction pathway ultimately leading to the cell response. Which of the following is NOT a likely mechanism for reversing (or shutting off) cAMP transduction?
Correct Answer
C. Activate adenylyl cyclase
Explanation
Adenylyl cyclase is responsible for producing cAMP, which is a key molecule in the cAMP signal transduction pathway. Activating adenylyl cyclase would further increase cAMP levels and enhance the pathway, rather than reversing or shutting it off. Therefore, activating adenylyl cyclase is not a likely mechanism for reversing cAMP transduction.
30.
Various cells in the body respond to the hormone epinephrine in various ways due to ______.
Correct Answer
A. Differential gene regulation
Explanation
The various cells in the body respond to the hormone epinephrine in different ways due to differential gene regulation. This means that different genes are turned on or off in different cells, leading to different responses to the hormone. The regulation of gene expression allows cells to have specific functions and responses to external signals like epinephrine. Therefore, the variability in gene regulation among different cells is responsible for the diverse responses to epinephrine throughout the body.
31.
Which of the following does NOT describe a typical cellular response to signaling molecules?
Correct Answer
B. Change in a gene sequence that encodes a particular protein
Explanation
A typical cellular response to signaling molecules involves the activation of enzymes within the cell, which can lead to various biochemical reactions and processes. It can also involve a change in the function of structural proteins, which determine cell shape and provide support. Additionally, signaling molecules can alter the levels of certain proteins in the cell by changes in gene expression. However, a change in a gene sequence that encodes a particular protein does not describe a typical cellular response to signaling molecules. This is because changes in gene sequences occur during processes like mutation or genetic recombination, rather than in direct response to signaling molecules.
32.
Due to gene regulation, cells _____ into specialized types of cells.
Correct Answer
C. Differentiate
Explanation
Gene regulation refers to the process by which genes are turned on or off in response to signals or environmental cues. This regulation ultimately determines the fate of a cell and whether it will differentiate into a specialized type of cell or not. Therefore, the correct answer is "differentiate" as it accurately describes the process by which cells develop into specialized types of cells through gene regulation.
33.
The function of the ECM in animals is ______.
Correct Answer
E. All of the above
Explanation
The extracellular matrix (ECM) in animals serves multiple functions. It provides structural support to tissues by forming a framework that holds cells together. Additionally, the ECM helps organize cells within tissues by providing a scaffold for cell attachment and migration. Moreover, the ECM plays a crucial role in cell signaling, as it contains various signaling molecules that regulate cell behavior and communication. Lastly, the ECM contributes to the strength and resilience of tissues. Therefore, the correct answer is "all of the above."
34.
The polysaccharide that forms the hard outer covering of many invertebrates is _____.
Correct Answer
B. Chitin
Explanation
Chitin is a polysaccharide that forms the hard outer covering of many invertebrates. It is a strong and flexible material that provides structural support and protection to these organisms. Collagen is a protein, not a polysaccharide, and is found in connective tissues. Chrondroitin sulfate is a component of cartilage, not the outer covering of invertebrates. Pectin is a polysaccharide found in plant cell walls, not in the outer covering of invertebrates. Cellulose is also a polysaccharide, but it is found in plant cell walls, not in the hard outer covering of invertebrates.
35.
Which of the following is involved in the process of tissue and organ formation in multicellular organisms?
Correct Answer
E. All of the above
Explanation
All of the options listed - cell growth, cell division, cell connections, and cell differentiation - are involved in the process of tissue and organ formation in multicellular organisms. Cell growth refers to the increase in size of cells, while cell division involves the replication of cells. Cell connections are important for cells to communicate and coordinate their activities. Cell differentiation refers to the process by which cells become specialized for specific functions. Together, these processes contribute to the development and organization of tissues and organs in multicellular organisms.
36.
The tissue type common to animals that functions in the conduction of electrical signals is _____.
Correct Answer
C. Nervous
Explanation
The correct answer is "nervous." Nervous tissue is responsible for conducting electrical signals in animals. This tissue type is found in the brain, spinal cord, and nerves, and it allows for the transmission of information throughout the body. Nervous tissue contains specialized cells called neurons, which are capable of generating and transmitting electrical impulses, allowing for communication and coordination of various bodily functions.
37.
Gap junctions prevent the leakage of materials across animal cell layers.
Correct Answer
B. False
Explanation
Gap junctions actually facilitate the exchange of materials between animal cell layers, rather than preventing leakage. These specialized channels allow for the direct transfer of ions, small molecules, and electrical signals between adjacent cells, enabling communication and coordination within tissues. Therefore, the correct answer is False.
38.
During glycolysis, glucose is broken down into ____.
Correct Answer
A. Pyruvate
Explanation
During glycolysis, glucose is broken down into pyruvate. Glycolysis is the initial step in cellular respiration, where glucose is converted into pyruvate through a series of enzymatic reactions. This process occurs in the cytoplasm of cells and does not require oxygen. The breakdown of glucose into pyruvate generates a small amount of ATP and NADH, which can be further used in the production of more ATP through other metabolic pathways. Therefore, pyruvate is the correct answer as it is the end product of glycolysis.
39.
Where does glycolysis take place?
Correct Answer
D. Cytosol
Explanation
Glycolysis is the metabolic pathway that converts glucose into pyruvate. It is the first step in cellular respiration and occurs in the cytosol, the fluid portion of the cell outside the organelles. This process does not take place in the mitochondria, as the other options suggest. Instead, glycolysis occurs in the cytosol to break down glucose and produce ATP.
40.
The ATP made during glycolysis is generated by ____.
Correct Answer
E. Substrate-level phosphorylation
Explanation
During glycolysis, ATP is generated by substrate-level phosphorylation. This process involves the direct transfer of a phosphate group from a high-energy molecule (such as a substrate) to ADP, forming ATP. In glycolysis, this occurs twice, resulting in a net production of two ATP molecules. Substrate-level phosphorylation is different from oxidative phosphorylation, which occurs in the electron transport chain, and photophosphorylation, which occurs in photosynthesis. Chemosmosis is a process that involves the movement of ions across a membrane to generate ATP, but it is not specifically related to glycolysis.
41.
The enzyme responsible for oxidizing pyruvate once it enters the mitochondrial matrix is _____.
Correct Answer
B. Pyruvate dehydrogenase
Explanation
Pyruvate dehydrogenase is the correct answer because it is the enzyme responsible for oxidizing pyruvate once it enters the mitochondrial matrix. This enzyme catalyzes the conversion of pyruvate to acetyl-CoA, which is an important step in the citric acid cycle (also known as the Krebs cycle) that takes place in the mitochondria. This conversion allows for the further breakdown of glucose and the production of energy in the form of ATP.
42.
In which phase of the cell cycle does the cell divide?
Correct Answer
C. M phase
Explanation
The M phase of the cell cycle is the phase in which the cell actually divides. It is also known as mitosis or cell division. During this phase, the cell undergoes a series of complex processes that result in the formation of two daughter cells with identical genetic information. These daughter cells can then go on to perform their specific functions in the body.
43.
Which of the following is a reason for meiotic division?
Correct Answer
C. Gamete formation in animals
Explanation
Meiotic division is a type of cell division that occurs in sexually reproducing organisms to produce gametes. Gametes are specialized cells that fuse during fertilization to form a new individual. Asexual reproduction does not involve the formation of gametes, while multicellularity refers to the presence of multiple cells in an organism, but does not directly relate to meiotic division. Therefore, the correct answer is "gamete formation in animals" as it accurately describes the purpose of meiotic division.
44.
During which phase of cellular division does Mendel's law of segregation physically occur?
Correct Answer
B. Meiosis I
Explanation
During the phase of cellular division known as meiosis I, Mendel's law of segregation physically occurs. This is because meiosis I is the stage where homologous chromosomes separate, resulting in the segregation of alleles into different gametes. This process is crucial for the formation of haploid cells with unique combinations of genetic material, which is the basis for genetic variation and inheritance as described by Mendel's law of segregation.
45.
An individual that has the same allele of a gene on both chromosomes is said to be _____.
Correct Answer
C. Homozygous
Explanation
An individual that has the same allele of a gene on both chromosomes is said to be homozygous. This means that both copies of the gene are identical, either both dominant or both recessive. Homozygosity can result in the expression of a particular trait or characteristic, as both copies of the gene carry the same information. In contrast, heterozygosity refers to having different alleles of a gene on each chromosome.
46.
If the SsWw individual is mated with another SsWw individual, what is the probability of producing a SSWW offspring?
Correct Answer
A. 1/16
Explanation
When two SsWw individuals are mated, each parent can produce four types of gametes: SW, Sw, sW, and sw. The probability of producing a SSWW offspring is the probability of getting SW from one parent and SW from the other parent, which is 1/4 * 1/4 = 1/16.
47.
A geneticist finds that a gene that gives werewolves long fangs also makes them extra hairy. This is an example of _____.
Correct Answer
B. Pleiotropy
Explanation
Pleiotropy refers to a single gene having multiple effects on an organism's phenotype. In this case, the gene responsible for long fangs in werewolves also affects their hairiness. This demonstrates pleiotropy because a single gene is influencing multiple traits in the organism.
48.
A situation where alleles at one gene influence the phenotypic expression of alleles of another gene would be called ____.
Correct Answer
E. Epistasis
Explanation
Epistasis refers to a situation where alleles at one gene can mask or modify the phenotypic expression of alleles at another gene. This means that the presence of certain alleles at one gene can override or suppress the effects of alleles at another gene, influencing the overall phenotype. Therefore, epistasis is the appropriate term to describe the given scenario.
49.
A replicated chromosome is composed of ____.
Correct Answer
C. Two sister chromatids held together at the centromere
Explanation
A replicated chromosome is composed of two sister chromatids held together at the centromere. This is because during DNA replication, each chromosome is duplicated to form two identical sister chromatids. These sister chromatids remain attached to each other at the centromere until they separate during cell division. This arrangement ensures that each daughter cell receives an exact copy of the genetic material.
50.
Selected genotypes at the BRCA1 locus in humans have been shown to cause breast cancer in woman. However, not all women with predisposing genotypes will get breast cancer. This is an example of ______.
Correct Answer
D. Penetrance
Explanation
Penetrance refers to the proportion of individuals with a specific genotype who exhibit the associated phenotype. In this case, the selected genotypes at the BRCA1 locus have been shown to cause breast cancer in some women, indicating that the genotype has high penetrance. However, not all women with these genotypes will develop breast cancer, suggesting that penetrance is incomplete in this context.