Questions

Below is the complete compilation of questions and answers from all three practice sets, with each question immediately followed by its corresponding answer. (For the source documents, see citeturn0file0 for Set 1, citeturn0file1 for Set 2, and citeturn0file2 for Set 3.)

Practice Questions Set 1

Questions 1–3 (Historical Poison Testing Experiment)

Independent vs. Dependent Variables
– Question: What are the independent and dependent variables in this study? (What is “manipulated” as opposed to what is “measured”?)
– Answer:
– Independent Variable: Whether the prisoner was treated with the medicinal oil (oil administered vs. not administered).
– Dependent Variable: The measured outcome—the survival (or death) of the prisoner (including time to death).
Causation or Correlation?
– Question: Does this study show causation or correlation? Explain why.
– Answer:
– This study represents a manipulative experiment because the treatment (oil) was deliberately applied. Thus, it is designed to demonstrate causation (i.e. the oil is linked causally to survival), although the very small sample size and ethical issues limit its robustness.
Improving the Experiment
– Question: How would you improve this experiment? Consider the elements of experimental design.
– Answer:
– Increase the sample size and include multiple subjects in each group to allow for replication and statistical significance.
– Use proper randomization to control for confounding variables.
– Standardize all other conditions (e.g., poison dosage, timing, environment) so that the only difference is the administration of the oil.

Questions 4–6 (Preschool Study)

Null and Alternative Hypotheses
– Question: State the null and alternative hypotheses for this study.
– Answer:
– Research Question: Does participation in an intensive preschool program lead to improved long-term academic and economic outcomes?
– Null Hypothesis (H₀): There is no difference in college attendance, GPA, or wages between children who attended preschool and those who did not.
– Alternative Hypothesis (H₁): Children who attended the intensive preschool program will show higher college attendance, higher GPAs, and higher wages later in life.
Variables
– Question: What are the dependent and independent variables in this study?
– Answer:
– Independent Variable: Preschool participation (enrolled vs. not enrolled).
– Dependent Variables: Long-term outcomes such as percentage attending college, GPA, and wages.
Randomization and Standardization
– Question: How did the researchers standardize the other variables in the study? What does randomization accomplish?
– Answer:
– Randomization helps ensure that any other variables (e.g., socioeconomic factors) are evenly distributed between groups, minimizing bias.
– Other variables are standardized by using a controlled selection process (random assignment) so that differences in outcomes can be more confidently attributed to the preschool intervention.

Question 7 (Tool-Use in Chimps Experiment)

Components of the Experiment
– Question: Identify the question being asked, the alternative hypothesis, the independent and dependent variables, and the control treatment.
– Answer:
– Big Question: Can an educated (trained) chimp teach its group members to use a stick as a tool to obtain food?
– Alternative Hypothesis: Groups with an educated chimp will exhibit a higher number of individuals successfully using the stick than groups without one.
– Independent Variable: Presence or absence of an educated (trained) chimp in the group.
– Dependent Variable: The count of chimps that use a stick at least 10 times in a 24‑hour period.
– Control Treatment: Group 3, which had no educated chimp, serving as the control group.

Question 8 (Fundamentals of Cell Theory)

Key Tenets of Cell Theory
– Question: What are the fundamentals of the cell theory as put together by Schleiden, Schwann, and Virchow?
– Answer:
– All living organisms are composed of one or more cells.
– The cell is the basic unit of life and organization in living things.
– All cells arise from pre‑existing cells.

Question 9 (Pasteur’s Experiment)

Breakdown of Pasteur’s Experiment
– Question: Review Pasteur’s experiment. What is the question being asked? What are two alternative hypotheses he was testing? Pick one of them and write the experimental prediction. What are the independent and dependent variables in this experiment? What are 2 standardized variables?
– Answer:
– Question Asked: Do microorganisms arise spontaneously or only from pre‑existing cells?
– Alternative Hypotheses:
1. Spontaneous generation: Microorganisms can emerge from non‑living matter.
2. Biogenesis: Microorganisms arise only from existing microorganisms.
– Experimental Prediction (choosing biogenesis): Sterilized broth that is protected from microbial contamination will remain free of microbial growth.
– Variables:
• Independent Variable: Exposure to air (and thereby potential contamination).
• Dependent Variable: Presence or absence of microbial growth.
– Standardized Variables: Temperature, nutrient composition of the medium, incubation time, and other environmental conditions.

Question 10 (Pasteur’s Support for Virchow’s Hypothesis)

Relating Pasteur’s Experiment to Virchow’s Hypothesis
– Question: How do Pasteur’s experiments support Virchow’s hypothesis?
– Answer:
– Virchow’s Two-Part Hypothesis:
1. All cells come from pre‑existing cells (biogenesis).
2. Spontaneous generation does not occur.
– In Pasteur’s experiment, the swan‑neck flask (which prevented entry of microorganisms) supports the second part by showing no microbial growth in a sterile environment. Conversely, when a flask is exposed (or its neck is broken), microbial growth occurs, indicating that cells come from the external environment, reinforcing the idea that cells do not form spontaneously.

Question 11 (Hierarchical Classification)

Most Inclusive vs. Most Exclusive
– Question: Consider hierarchical classification going from species to genus to… to domain. Which is the most inclusive? Which is the most exclusive?
– Answer:
– Most Inclusive: Domain (the highest taxonomic level).
– Most Exclusive: Species (the most specific level).

Question 12 (Scientific Name Format)

Correct Format of a Scientific Name
– Question: Which of the following scientific names is written in the correct format?
– Answer:
– The proper format capitalizes only the genus and uses lowercase for the species name. Therefore, "Phaseolus vulgaris" is correct.

Question 13 (Flightless Birds)

Major Question Raised by Distribution of Flightless Birds
– Question: When comparing the large flightless birds (Rheas, Emus, and Ostriches), what was the major question?
– Answer:
– Why are similar large flightless birds found on different continents? This raises issues of convergent evolution versus common ancestry and adaptation to similar ecological niches.

Question 14 (Comparative Anatomy – Homologous Structures)

Comparative Anatomy Question
– Question: The study of comparative anatomy of vertebrates showed that the bones in the forearms of humans and legs of dogs and wings of bats are the same bones. What question did that raise?
– Answer:
– Why do organisms with very different functions share similar bone structures? This suggests a common evolutionary origin (homology) and raises questions about how modifications lead to different functions.

Question 15 (Embryonic Similarities)

Question Raised by Similar Embryonic Stages
– Question: The study of comparative anatomy of vertebrate embryos showed that these embryos go through similar developmental stages early on. What question did that raise?
– Answer:
– Why do vertebrate embryos exhibit similar early developmental stages despite evolving into diverse forms? This implies a shared developmental pathway or common ancestry.

Question 16 (Extinct Fossils vs. Modern Relatives)

Interest in Fossil vs. Extant Organisms
– Question: What was the interest in the extinct fossils versus their modern contemporaries, such as glyptodonts and armadillos, or giant ground sloths and modern sloths?
– Answer:
– The focus is on understanding why closely related organisms—such as glyptodonts versus armadillos or giant ground sloths versus modern sloths—have differing survival outcomes, examining the ecological and evolutionary factors that led to extinction in some cases.

Question 17 (Lyell’s Influence on Darwin)

Charles Lyell’s Contribution
– Question: Why was Charles Lyell’s theory of uniformity important to Darwin’s thought process?
– Answer:
– Lyell’s theory proposed that geological processes occur gradually over long periods. This concept helped Darwin understand that small, cumulative changes (natural selection) over vast periods could lead to significant evolutionary change.

Question 18 (Malthus and Natural Selection)

Malthus’s Influence
– Question: What did Malthus say about human populations and how did that influence Darwin’s theory of natural selection?
– Answer:
– Malthus argued that populations grow exponentially while resources increase only arithmetically, leading to a struggle for survival. This idea helped Darwin realize that competition for limited resources drives natural selection.

Question 19 (Animal/Plant Breeding and Natural Selection)

Artificial Selection as an Analogy
– Question: How did the work of animal and plant breeders relate to Darwin’s theory of natural selection?
– Answer:
– Breeders selectively mate organisms to enhance desired traits, demonstrating how selection pressures can shape a population. This process mirrors natural selection, where environmental pressures favor certain traits, thus driving evolution.

Question 20 (Darwin’s Four Tenets)

Darwin’s Four Tenets of Natural Selection
– Question: What are Darwin’s 4 tenets of evolution through natural selection?
– Answer:
1. Variation: Individuals within a population vary in traits.
2. Heritability: Traits are passed from parents to offspring.
3. Overproduction: More offspring are produced than can survive given environmental constraints.
4. Differential Survival: Individuals with advantageous traits are more likely to survive and reproduce.

Question 21 (Insect Color Variation)

Insect Color Variation and Natural Selection
– Question: Consider the slide showing the bird hunting the insects of different colors. Why are there different colors to begin with? What will happen to the colors in the next generation?
– Answer:
– Why the Variation? Genetic differences cause variation in coloration.
– Prediction: When a predator (bird) preferentially preys on the more visible (less camouflaged) insects, the less visible (better camouflaged) insects will have a survival advantage. Over generations, the frequency of the less visible color will increase in the population.

Question 22 (Darwin’s Concept – Exception)

Which Statement Is NOT Part of Darwin’s Original Concept?
– Question: Which of the following statements is not part of Charles Darwin's concept of natural selection?
– Answer:
– Option c: “Characteristics of organisms are inherited as genes on chromosomes.” (Darwin’s ideas predated the discovery of genes and chromosomes.)

Question 23 (Antibiotic Resistance)

Antibiotic Resistance Explained by Natural Selection
– Question: Explain how indiscriminate use of antibiotics is leading to the evolution of antibiotic-resistant bacteria using Darwin’s 4 tenets.
– Answer:
– In any bacterial population, there is variation in susceptibility to antibiotics.
– When antibiotics are used indiscriminately, susceptible bacteria die while resistant ones survive and reproduce.
– This shifts the population toward resistance, exemplifying natural selection in action.

Question 24 (pH and Acidity)

Why pH 6 Is More Acidic Than pH 7
– Question: An aqueous solution at pH 6 is more acidic than one at pH 7. Why?
– Answer:
– pH is defined as –log₁₀[H⁺].
– A solution at pH 6 has a hydrogen ion concentration of 10⁻⁶ M, while pH 7 has 10⁻⁷ M.
– Because 10⁻⁶ M is greater than 10⁻⁷ M, the pH 6 solution is more acidic.

Question 25 (Substance That Cannot Be Broken Down)

Substance That Cannot Be Broken Down
– Question: A substance that cannot be broken down into simpler substances by ordinary chemical or physical techniques is a(n) _____.
– Answer:
– An element cannot be broken down into simpler substances by ordinary chemical or physical techniques.

Question 26 (Isotopes of Carbon)

Why ¹⁴C Is Heavier Than ¹²C
– Question: ¹⁴C is heavier than ¹²C because it has ______.
– Answer:
– ¹⁴C has two more neutrons than ¹²C.

Question 27 (Characteristics of Living Things)

Characteristics of Life
– Question: For something to be considered living, what characteristics must it exhibit?
– Answer:
– Living organisms typically exhibit:
• Cellular organization
• Metabolism (energy processing)
• Homeostasis (internal balance)
• Growth and development
• Reproduction
• Response to stimuli
• Adaptation through evolution

Question 28 (Isotope Ratios as Evidence of Life)

Evidence from ¹²C:¹³C Ratios
– Question: Why is a change in the 12C:13C ratio about 3.7 BYA considered to be evidence for life?
– Answer:
– Enzymes in living organisms preferentially use the lighter ¹²C isotope.
– A change in the ¹²C:¹³C ratio (with more ¹²C) around 3.7 billion years ago is taken as evidence that biological processes were at work.

Question 29 (Hypotheses on the Origin of Cells)

Hypotheses for the Origin of the First Cells
– Question: What are 3 possible hypotheses we reviewed in class for the question: where did the first cells on Earth come from?
– Answer:
– Abiogenesis: Life arose spontaneously from non‑living matter under early Earth conditions.
– Panspermia: Life or its building blocks were delivered to Earth from space (via meteorites, comets, etc.).
– Hydrothermal Vent Hypothesis: Life originated in the chemically rich environment of deep‑sea hydrothermal vents.

Question 30 (Seeding Hypothesis)

Seeding (Panspermia) Hypothesis
– Question: What does the seeding hypothesis state?
– Answer:
– This hypothesis states that life—or at least the essential organic molecules—was brought to Earth from outer space by meteorites, comets, or cosmic dust.

Question 31 (Hydrogen Bond Formation)

How Partial Charges Lead to Hydrogen Bonds
– Question: Explain how “partial” charges can lead to the formation of a hydrogen bond.
– Answer:
– When hydrogen is covalently bonded to a highly electronegative atom (like O or N), it acquires a partial positive charge.
– This hydrogen atom is then attracted to a nearby electronegative atom with a partial negative charge, forming a hydrogen bond.

Question 32 (Ionic vs. Polar Covalent Bonds)

Differences Between Ionic and Polar Covalent Bonds
– Question: What is the difference between an ionic bond and a polar covalent bond?
– Answer:
– Ionic Bond: Involves the transfer of electrons from one atom to another, forming oppositely charged ions that attract one another.
– Polar Covalent Bond: Involves the unequal sharing of electrons between atoms, resulting in partial positive and negative charges within the molecule.

Practice Questions Set 2

Question 1 (Identifying Bonds in a Structure)

Identifying Bonds
– Question: In the structure above, circle and label one polar covalent bond, one non‑polar covalent bond, and one hydrogen bond.
– Answer:
– Polar Covalent Bond: Typically occurs between atoms of differing electronegativity (e.g. O–H).
– Non‑Polar Covalent Bond: Occurs between atoms with similar electronegativity (e.g. C–C).
– Hydrogen Bond: A weak bond (often drawn as a dashed line) between a hydrogen atom (bonded to an electronegative atom) and another electronegative atom.

Question 2 (Basic Functional Group)

Basic Functional Group
– Question: Which of the 7 functional groups we reviewed is basic? What does it mean for this functional group to be basic?
– Answer:
– The amine group (–NH₂) is basic because it can accept a proton (H⁺), resulting in a positive charge under acidic conditions.

Question 3 (Weakest Chemical Linkage)

Weakest Chemical Linkage
– Question: Which of the following types of chemical linkages is the weakest?
– Answer:
– Van der Waals forces are the weakest among the listed types of chemical interactions.

Question 4 (Molecules with Only Carbon and Hydrogen)

Molecules Consisting Only of C and H
– Question: In general, molecules consisting only of carbon and hydrogen atoms are called ____.
– Answer:
– These molecules are called hydrocarbons.

Question 5 (Structural Isomers: Glucose vs. Fructose)

Different Sugars Despite Same Formula
– Question: Review the structures for Fructose and Glucose. How come they are considered two different sugars?
– Answer:
– Glucose and fructose are structural isomers; they have the same molecular formula and functional groups but differ in the arrangement of atoms (especially the position of the carbonyl group).

Question 6 (Aldehyde vs. Ketone)

Aldehyde vs. Ketone
– Question: Glucose is an aldehyde, while fructose is a ketone. Explain what that means.
– Answer:
– Glucose is an aldehyde because its carbonyl group is located at the end of the chain (bonded to a hydrogen).
– Fructose is a ketone because its carbonyl group is positioned internally (bonded between two carbons).

Question 7 (Type of Reaction)

Type of Reaction
– Question: What kind of reaction is shown below?
– Answer:
– The reaction is a dehydration synthesis (condensation) reaction, where monomers join to form a larger molecule with water as a byproduct.

Question 8 (Amylose vs. Cellulose)

Similarities and Differences Between Amylose and Cellulose
– Question: Review the figures for the structures of amylose and cellulose. What do the two structures have in common? Why can enzymes digest amylose but not cellulose?
– Answer:
– Similarity: Both amylose and cellulose are polymers of glucose.
– Difference:
• Amylose has α‑1,4 glycosidic bonds (which can be digested by human enzymes).
• Cellulose has β‑1,4 glycosidic bonds (which human enzymes cannot break down).

Question 9 (Phospholipids vs. Triglycerides)

Phospholipids vs. Triglycerides
– Question: What is the difference between a phospholipid and a triglyceride?
– Answer:
– Triglycerides: Glycerol is esterified to three fatty acids.
– Phospholipids: Glycerol is esterified to two fatty acids and one phosphate group (often further linked to a polar molecule), making them amphipathic.

Question 10 (Saturated vs. Unsaturated; Cis vs. Trans)

Fatty Acid Characteristics
– Question: Explain what it means for a fatty acid to be saturated versus unsaturated, and cis versus trans fat.
– Answer:
– Saturated Fatty Acids: No double bonds; straight chains with maximum hydrogen atoms.
– Unsaturated Fatty Acids: One or more double bonds, which introduce kinks.
– Cis Configuration: Hydrogen atoms on the same side of the double bond, causing a bend.
– Trans Configuration: Hydrogen atoms on opposite sides, resulting in a straighter chain.

Question 11 (Amphipathic Phospholipids)

Amphipathic Definition
– Question: What does it mean for a phospholipid to be amphipathic?
– Answer:
– Molecules that have both a hydrophilic (water‑loving) region and a hydrophobic (water‑fearing) region.
– Example: A phospholipid (with a hydrophilic phosphate head and hydrophobic fatty acid tails).

Question 12 (Cholesterol vs. Phospholipids)

Structural Similarity Between Cholesterol and Phospholipids
– Question: Cholesterol structure is very different from phospholipids. Both are found in membranes in animal cells. What is the similarity in their structural properties?
– Answer:
– Both cholesterol and phospholipids contain regions that are hydrophobic as well as small polar regions (cholesterol has a polar –OH group).

Question 13 (Glycerol Backbone)

Glycerol Backbone
– Question: Select all that apply: Glycerol forms the backbone of which molecules?
– Answer:
– Glycerol forms the backbone of triglycerides and phospholipids.

Question 14 (Amino Acid Side Groups)

Amino Acid Side Groups
– Question: The two amino acids depicted both have side groups (R groups) that are which of the following?
– Answer:
– In the depicted pair (based on typical examples), the side groups are uncharged and nonpolar.

Question 15 (Protein Secondary Structure)

Protein Secondary Structure Identification
– Question: The structure depicted in the figure shows what type of protein secondary structure?
– Answer:
– If the figure shows a repeating helical or sheet pattern, it is likely an α‑helix (secondary structure) and is an example of secondary structure.

Question 16 (Hydrophobic Interactions in Tertiary Structure)

Role of Hydrophobic Interactions
– Question: Explain how hydrophobic interactions among amino acid side chains may help form the tertiary structure of a polypeptide.
– Answer:
– Hydrophobic amino acid side chains tend to cluster together in the interior of the protein to avoid contact with water, which helps stabilize the protein’s overall three‑dimensional (tertiary) structure.

Question 17 (Disulfide Bridges)

Amino Acid Involved in Disulfide Bridges
– Question: Look up the structures of cysteine and glycine. Which one can be involved in forming disulfide bridges?
– Answer:
– Cysteine contains a sulfhydryl (–SH) group, which can form disulfide bridges, while glycine does not.

Question 18 (Peptide Bond)

Definition of a Peptide Bond
– Question: What is a peptide bond?
– Answer:
– A peptide bond is the covalent bond that links the carboxyl group of one amino acid to the amino group of the next, with the loss of a water molecule.

Question 19 (Type of Bond in Protein Structure)

Identifying a Bond in Protein Structure
– Question: The chemical bond shown below is called what?
– Answer:
– Based on textbook references, the highlighted bond is a hydrogen bond (which plays a major role in stabilizing secondary structures such as α‑helices and β‑sheets).

Question 20 (Level of Protein Structure)

Protein Structure Level
– Question: The chemical bonds highlighted above are involved in the formation of which level of structure in the protein?
– Answer:
– The hydrogen bonds highlighted are involved in the formation of the secondary structure of proteins.

Question 21 (Protein Structure Fill-in-the-Blanks)

Fill in the Blanks
– Question: Fill in the blanks: The unique sequence of monomer subunits in a protein is the ____ structure of the protein. An ionic bond between the amino acid side groups (R groups) from two different polypeptide chains in a multichain protein would be considered part of the ____ structure of the protein.
– Answer:
– The unique sequence of monomers in a protein is its primary structure.
– An ionic bond between side groups on different polypeptide chains in a multichain protein is part of the quaternary structure.

Question 22 (Coronavirus Spike Protein Structure)

Tertiary vs. Quaternary Structure of the Spike Protein
– Question: Explain the difference between the tertiary and quaternary structure of the spike protein.
– Answer:
– Tertiary Structure: The three‑dimensional folding of a single polypeptide chain (its own unique shape).
– Quaternary Structure: The assembly of multiple polypeptide subunits into a larger, functional complex (for example, the trimeric organization of the spike protein).

Question 23 (Importance of Spike Protein Shape)

Why the Shape of the Spike Protein Matters
– Question: Explain why the shape of the spike protein of Coronavirus matters.
– Answer:
– The precise three‑dimensional shape of the spike protein is critical for binding to the host cell receptor (ACE2). A proper fit is required for viral entry, meaning that even small changes in shape can greatly influence infectivity and immune recognition.

Question 24 (Drawing Glycine)

Structure of Glycine
– Question: Glycine is an amino acid with an H as the R group. Draw the structure of glycine.
– Answer:
– Description:
• Central (α) carbon attached to:
– An amino group (NH₂)
– A carboxyl group (COOH)
– A hydrogen (the R group)
– A second hydrogen (as the fourth substituent)
– Text Diagram:
H | NH₂–C–COOH | H

Practice Questions Set 3 (With Hints)

Question 1 (MC1R Gene Nucleotide Sequence)

Why Only the Nitrogenous Bases?
– Question: The “nucleotide sequence” of the MC1R gene only shows the sequence of the nitrogenous bases, not the nucleotides. Why?
– Answer:
– The sequence lists only the order of the nitrogenous bases (A, T/U, C, G) because these bases carry the genetic information.
– The sugar–phosphate backbone is common to all nucleotides and does not add extra coding information.

Question 2 (Abiogenesis vs. Virchow’s Hypothesis)

Abiogenesis Theory vs. Virchow’s Hypothesis
– Question: What is the theory of abiogenesis as proposed by Oparin and Haldane? How does it relate to Virchow’s hypothesis about the origin of cells?
– Answer:
– Abiogenesis (Oparin/Haldane): Proposes that life arose from non‑living matter through these steps:
1. Formation of simple organic molecules (e.g. amino acids, nucleotides) from inorganic compounds in a reducing atmosphere.
2. Assembly of these molecules into more complex polymers.
3. Formation of protocells with lipid membranes.
4. Development of metabolic and genetic functions leading to true cells.
– Virchow’s Hypothesis: States that all cells come from pre‑existing cells.
– Relation: Abiogenesis explains how the first cells might have originated when no cells were present, while Virchow’s hypothesis applies once cells already exist.

Question 3 (Pasteur vs. Miller/Urey)

Comparing Two Experiments
– Question: Consider the experiments by Pasteur and by Miller/Urey. What are the questions and hypotheses they are addressing? Are they related?
– Answer:
– Pasteur’s Experiment: Tested whether microorganisms arise spontaneously or only from pre‑existing cells (focusing on modern life and biogenesis).
– Miller/Urey Experiment: Investigated whether organic molecules necessary for life could be synthesized under early Earth conditions (focusing on the origin of life’s building blocks).
– Relationship: Both address the origins of life but from different angles—one refutes spontaneous generation in existing life, the other demonstrates a plausible chemical pathway for life’s beginnings.

Question 4 (Significance of Miller–Urey Products)

Significance of Specific Products
– Question: Review the list of products from the Miller–Urey experiment. What is the significance of formaldehyde, formic acid, amino acids, and fatty acids? How about adenine synthesis from Joan Oro’s work?
– Answer:
– Formaldehyde: A simple organic molecule that can polymerize to form sugars.
– Formic Acid: A small organic acid that can participate in metabolic reactions.
– Amino Acids: The building blocks of proteins.
– Fatty Acids: Key components of lipids, which form cell membranes.
– Adenine Synthesis: Demonstrates that nucleobases (critical for nucleic acids) can also form abiotically.
– Overall: These products represent the four major classes of biomolecules needed for a living cell: carbohydrates, proteins, lipids, and nucleic acids.

Question 5 (Miller–Urey and Abiogenesis)

Step Supported by Miller–Urey
– Question: Which part of abiogenesis as proposed by Oparin and Haldane is supported by the results of the Miller–Urey experiment?
– Answer:
– The experiment supports the step in abiogenesis involving the synthesis of organic molecules (like amino acids and fatty acids) from inorganic precursors under early Earth conditions.

Question 6 (Polymerization Work Importance)

Importance of Fox and Bernal’s Work
– Question: Without getting into details of polymerization, explain why the work of Sidney Fox and Bernal matters to the theory of abiogenesis.
– Answer:
– Their research demonstrated that simple organic molecules can polymerize into larger, more complex molecules (e.g. peptides), offering a plausible mechanism for how the basic building blocks of life could assemble into functional macromolecules.

Question 7 (Ribozymes)

Ribozymes and the RNA World
– Question: What are ribozymes? Explain what their discovery suggested about the genetic material in the first cells.
– Answer:
– Ribozymes are RNA molecules that possess catalytic activity. Their discovery suggests that early life might have relied on RNA both to store genetic information and to catalyze chemical reactions—supporting the RNA world hypothesis.

Question 8 (Cilia/Flagella Structural Components)

Principal Component of Cilia/Flagella
– Question: The principal structural components of cilia and flagella are:
– Answer:
– Microtubules are the main structural elements of cilia and flagella.

Question 9 (Comparing Flagella and Cilia)

Comparing Prokaryotic and Eukaryotic Structures
– Question: Compare and contrast the flagella of prokaryotes with the flagella and cilia of eukaryotes.
– Answer:
– Prokaryotic Flagella: Made primarily of the protein flagellin; simpler in structure; rotate like propellers.
– Eukaryotic Flagella and Cilia: Composed of microtubules arranged in a 9+2 pattern; beat in a whip‑like or coordinated fashion; are membrane‑bound.

Question 10 (Flagellar Motor Structure)

Identifying the Motor Structure
– Question: The figure on the right shows the structure of the motor involved in movement of which organelle in which type of organisms?
– Answer:
– The figure likely shows the bacterial flagellar motor, a complex protein assembly in prokaryotes that drives the rotation of the flagellum for locomotion.

Question 11 (Regulation of Molecule Movement)

Movement Regulation
– Question: Which structure regulates the movement of molecules in and out of the cell?
– Answer:
– The structure that regulates the movement of molecules in and out of the cell is the plasma membrane.

Question 12 (Central Vacuole and Turgor Pressure)

Central Vacuole Function in Turgor
– Question: Describe the role of the central vacuole in maintaining turgor pressure in a crisp lettuce leaf versus a wilted leaf.
– Answer:
– A full central vacuole stores water, maintains high turgor pressure, and keeps a lettuce leaf crisp. In a wilted leaf, loss of water from the vacuole leads to decreased turgor pressure and a flaccid appearance.

Question 13 (Site of Aerobic Respiration)

Organellar Site of Aerobic Respiration
– Question: Aerobic respiration in plants occurs in which organelle?
– Answer:
– Mitochondria are the organelles where aerobic respiration occurs in plants.

Question 14 (Organelles with DNA)

DNA-Containing Organelles
– Question: Select all that apply: Which organelles contain DNA?
– Answer:
– Mitochondria and chloroplasts contain their own DNA.

Question 15 (Endoplasmic Reticulum Continuity)

ER and Nuclear Envelope Continuity
– Question: True/False: The endoplasmic reticulum is continuous with the nuclear envelope.
– Answer:
– True.

Question 16 (Relative Sizes in Plant Cells)

Ranking Organelles by Size
– Question: In a plant cell, rank the following organelles in terms of their size: central vacuole, chloroplast, mitochondrion.
– Answer:
– Largest: Central vacuole
– Intermediate: Chloroplast
– Smallest: Mitochondrion

Question 17 (Centrioles in Plant Cells)

Presence of Centrioles in Plant Cells
– Question: True/False: Plant cells contain centrioles.
– Answer:
– False.

Question 18 (Endosymbiosis – Chronology)

Endosymbiosis Chronology
– Question: True/False: Endosymbiosis was proposed as a mechanism for evolution of chloroplasts before it was proposed for evolution of mitochondria.
– Answer:
– False. Endosymbiosis was initially proposed for mitochondria and later extended to chloroplasts.

Question 19 (Gene Transfer Idea)

Gene Transfer from Organelles to the Nucleus
– Question: True/False: The idea of gene transfer from organelles to the nucleus was proposed first by Schimper about the evolution of chloroplasts.
– Answer:
– True.

Question 20 (Major Components of Cell Membrane)

Components of the Cell Membrane
– Question: What are the major structural components of a cell membrane?
– Answer:
– The cell membrane is mainly composed of phospholipids, proteins, and sterols.

Question 21 (Fluid Mosaic Model)

Phospholipid Mobility
– Question: According to the fluid mosaic model, what is true regarding membrane phospholipids?
– Answer:
– Membrane phospholipids can move laterally along the plane of the membrane.

Question 22 (Key Lipid in Membranes)

Most Important Lipid Component
– Question: Which type of lipid is most important in the structure of biological membranes?
– Answer:
– Phospholipids are the most important lipid component in biological membranes.

Question 23 (Meaning of “Glyco-”)

Understanding “Glyco-”
– Question: When referring to membrane glycolipids and glycoproteins, to what does the term "glyco-" refer?
– Answer:
– The carbohydrate (sugar) portion attached to glycolipids or glycoproteins.

Question 24 (Amphipathic Definition and Example)

Amphipathic Components
– Question: What does amphipathic mean? List one example of an amphipathic component of membranes.
– Answer:
– Amphipathic means having both hydrophilic and hydrophobic regions.
– Example: Phospholipids (hydrophilic phosphate head and hydrophobic fatty acid tails).

Question 25 (Unsaturated Fatty Acids and Membrane Function)

Membrane Fluidity and Fatty Acids
– Question: Explain the role of unsaturated fatty acids of phospholipids in maintaining the function of the plasma membrane. Why is it important for organisms to adjust the proportion of phospholipids with saturated versus unsaturated fatty acids as the seasons change?
– Answer:
– Unsaturated fatty acids have kinks that prevent tight packing, thereby increasing membrane fluidity.
– Organisms adjust the proportion (more unsaturated in cold temperatures) to maintain optimal membrane function as environmental temperatures change.

Question 26 (Lipid Movement: Lateral vs. Flip-Flop)

Lateral Drift vs. Transverse Flip-Flop
– Question: Explain why lateral drift of lipids in a membrane happens much more often than transverse flip-flop.
– Answer:
– Lateral diffusion is energetically favorable and occurs rapidly within the same layer of the membrane, while transverse flip-flop is energetically unfavorable because the polar head must pass through the hydrophobic core.

Question 27 (Role of SARS‑CoV‑2 Spike Protein)

Spike Protein Function
– Question: Explain the role of the SARS‑CoV‑2 spike protein in viral invasion.
– Answer:
– The SARS‑CoV‑2 spike protein, a glycoprotein, binds to the host cell receptor (ACE2) to facilitate viral entry by promoting membrane fusion.

Question 28 (TMPRSS2 Function)

TMPRSS2 Characteristics
– Question: Explain what type of protein TMPRSS2 is and how it helps the virus.
– Answer:
– TMPRSS2 is a serine protease that cleaves and activates the spike protein, facilitating the fusion of the viral and host cell membranes, which aids viral entry.

Question 29 (Frye and Edidin Membrane Fusion Experiment)

Membrane Fusion Experiment Analysis
– Question: In the Frye and Edidin experiment, state:
• What is the big question being asked?
• What is one alternative hypothesis?
• What is the null hypothesis for the alternative hypothesis you wrote above?
• What is the experimental prediction based on the alternative hypothesis?
– Answer:
– Big Question: Do the membranes of fused cells allow their lipids and proteins to mix uniformly?
– Alternative Hypothesis: Upon fusion, membrane components will diffuse and mix homogeneously between the two originally distinct membranes.
– Null Hypothesis: No mixing occurs; the membrane components remain segregated even after fusion.
– Experimental Prediction: After fusion, markers from each original membrane will be found evenly distributed throughout the fused membrane.