BIOL 107 606 Fundamentals of Microbiology

Correct Answer C: Tissue

Detailed Explanation of the Correct Answer:

C. Tissue is correct because in biological organization, a tissue is defined as a group of similar cells that are structurally alike and work together to perform a specific, common function. For example, muscle tissue contracts to produce movement, and epithelial tissue forms protective layers. Tissues are the next level of complexity above cells and serve as the building blocks for organs.

Explanation of Why the Other Options Are Incorrect:

A. Organ – Organs are made up of multiple types of tissues functioning together, not just one type of cell. An example is the heart, which includes muscle tissue, connective tissue, and nerve tissue.

B. System – A system refers to a group of organs working together, such as the digestive or circulatory system. It is a broader organizational level beyond tissues and organs.

D. Organism – An organism is a complete living individual composed of multiple systems. It includes all levels of biological organization, including cells, tissues, organs, and systems.

Summary:

A tissue is a group of similar cells working together for one function, making the correct answer C. Tissue.

Correct Answer A: Primary structure

Explanation:

The primary structure of a protein is the specific sequence of amino acids in a polypeptide chain. This sequence is determined by the gene encoding the protein and forms the foundation for all higher levels of protein structure.

The amino acids are linked by peptide bonds in a linear fashion.

Even a single change in this sequence can dramatically alter the protein's function.

Why the other options are incorrect:

B) Secondary structure:

This refers to localized folding into structures like α-helices and β-pleated sheets, stabilized by hydrogen bonds—not the amino acid sequence itself.

C) Tertiary structure:

This is the overall 3D shape of a single polypeptide chain, formed by interactions between side chains (R groups) of the amino acids.

D) Quaternary structure:

This level involves the interaction and arrangement of multiple polypeptide chains (subunits) into a functional protein complex.

Correct Answer B: 15

Explanation:

The atomic number of an atom is determined by the number of protons in its nucleus. In this case, the atom has 15 protons, so its atomic number is 15. The atomic number defines the element and its position on the periodic table (in this case, phosphorus).

Why the other options are incorrect:

A) 31:

This is the mass number, which is the sum of protons and neutrons (15 + 16 = 31), not the atomic number.

C) 17:

This is the number of electrons, which does not determine the atomic number.

D) 16:

This is the number of neutrons, which affects the isotope, not the atomic number.

E) 33, F) 48, G) 32:

These values do not correspond to the number of protons in the atom and are unrelated to the atomic number in this case.

Correct Answer E: Telophase

Detailed Explanation of the Correct Answer:

E. Telophase is the correct answer because the image shows two distinct nuclear regions forming within a single cell, which is a defining feature of telophase. During this phase, the separated chromosomes reach the opposite poles of the cell and begin to de-condense back into chromatin. At the same time, nuclear envelopes start to re-form around each set of chromosomes, effectively restoring the nuclei in each emerging daughter cell. The cell also begins to show signs of cytokinesis, as indicated by the clear indentation or cleavage between the two nuclear regions in the image.

Explanation of Why the Other Options Are Incorrect:

A. Interphase – This is the phase where the cell is not actively dividing. The DNA is in the form of uncondensed chromatin, and the nucleus is intact. No visible chromosomes or nuclear division occurs in this phase, which contrasts with what is shown in the image.

B. Metaphase – In metaphase, chromosomes align in the middle of the cell along the metaphase plate. The image does not show any such alignment; instead, the chromosomes are already separated.

C. Prophase – Prophase is characterized by the condensation of chromatin into chromosomes and the beginning of spindle fiber formation. However, no nuclear envelope breakdown or chromosome condensation is occurring in the image; the chromosomes are already separated into two regions.

D. Anaphase – In anaphase, sister chromatids are pulled apart toward opposite poles of the cell. The image shows that the chromatids have already been moved to opposite ends and are now enclosed in forming nuclei, indicating that anaphase is complete and telophase has begun.

Summary:

The image depicts two forming nuclei within one cell, with chromosomes enclosed and the cell beginning to divide. These characteristics are consistent with telophase, the final stage of mitosis before cytokinesis. Therefore, the correct answer is E. Telophase.

The correct answer is A): Pro

Based on the provided codon dictionary, the three-nucleotide sequence CCG codes for the amino acid Pro (Proline).

Explanation:

Locate the first letter (C) in the leftmost column.

Find the second letter (C) in the top row.

Match the third letter (G) in the corresponding box.

The codon CCG is found in the C row and C column, intersecting with G as the third letter, which corresponds to Pro.

Explanation of Why the Other Options Are Incorrect:

Leu (Leucine)

Codons for Leu are UUA, UUG, CUU, CUC, CUA, CUG.

CCG is not in this list.

Gln (Glutamine)

Codons for Gln are CAA, CAG.

CCG does not match these sequences.

His (Histidine)

Codons for His are CAU, CAC.

​​​​​​​CCG does not match these sequences.

Summary:

The codon CCG specifically codes for Pro (Proline), as confirmed by the codon table.

The other options (Leu, Gln, His) are incorrect because their codons do not include CCG.

Key Takeaway: Each codon is unique to one amino acid (except for stop codons), and CCG → Pro is a direct match.

Final Answer: Pro is the correct amino acid for CCG.

Correct Answer D: Aerobic respiration

Detailed Explanation of the Correct Answer:

D. Aerobic respiration is correct because it is the most efficient method of converting glucose into usable ATP in the human body. In the presence of oxygen, glucose undergoes complete oxidation through a series of steps: glycolysis, the Krebs cycle, and the electron transport chain. This process can yield up to 36–38 ATP molecules per glucose molecule, making it far more efficient than any anaerobic process.

Explanation of Why the Other Options Are Incorrect:

A. Lactic acidosis – This is not a method of glucose conversion but rather a dangerous condition where lactic acid accumulates in the body, usually due to prolonged anaerobic metabolism. It can lead to muscle fatigue and other health issues.

B. Anaerobic respiration – This occurs when oxygen is not available. It includes glycolysis followed by lactic acid fermentation, producing only 2 ATP molecules per glucose, which is much less efficient than aerobic respiration.

C. Fermentation conversion – Like anaerobic respiration, fermentation produces minimal ATP. It helps regenerate NAD⁺ for glycolysis but results in very low energy yield (only 2 ATP per glucose).

Summary:

Aerobic respiration is the most efficient and productive method of glucose conversion for generating ATP in the human body. The correct answer is D. Aerobic respiration.

Correct Answer B: They serve as high-energy electron carriers that transport electrons throughout the cell

Detailed Explanation of the Correct Answer:

B. They serve as high-energy electron carriers that transport electrons throughout the cell is correct because NAD⁺ and FAD are coenzymes that become NADH and FADH₂ when they accept electrons during glycolysis, the citric acid (Krebs) cycle, and pyruvate oxidation. These reduced forms carry high-energy electrons and hydrogen atoms to the electron transport chain (ETC) in the mitochondria. There, the electrons are used to generate a proton gradient, which ultimately drives the synthesis of ATP through oxidative phosphorylation.

Explanation of Why the Other Options Are Incorrect:

A. They serve to help produce co-enzyme A – This is incorrect. Coenzyme A is involved in the conversion of pyruvate to acetyl-CoA, but NAD⁺/FAD are not involved in its production.

C. They serve as the final electron acceptor for the electron transport chain – This is incorrect. The final electron acceptor in the ETC is oxygen, not NAD⁺ or FAD.

D. They serve to directly help catalyze the reaction of ADP to ATP – Incorrect. While NADH and FADH₂ contribute to the process that leads to ATP production, they do not directly catalyze the conversion of ADP to ATP. That function is performed by ATP synthase.

Summary:

NAD⁺/NADH and FAD/FADH₂ function as electron carriers, shuttling high-energy electrons to the electron transport chain, where most of the cell's ATP is ultimately generated. Therefore, the correct answer is B.

Correct Answer B: Strep throat

Detailed Explanation of the Correct Answer:

B. Strep throat is correct because it is caused by the bacterium Streptococcus pyogenes, also known as group A streptococcus. It is a bacterial infection that affects the throat and tonsils, leading to symptoms like sore throat, fever, swollen lymph nodes, and difficulty swallowing. Since it's bacterial, strep throat can be effectively treated with antibiotics, such as penicillin or amoxicillin.

Explanation of Why the Other Options Are Incorrect:

A. Common cold – Caused by viruses, most commonly rhinoviruses, not bacteria. Antibiotics are ineffective against the common cold.

C. AIDS (HIV⁺) – Caused by the Human Immunodeficiency Virus (HIV), which is a virus, not a bacterium.

D. Mumps – Caused by the mumps virus, which is a viral infection, often preventable through vaccination.

Summary:

Among the options listed, strep throat is the only disease caused by a bacterium, making the correct answer B. Strep throat.

Correct Answer E: S phase

Detailed Explanation of the Correct Answer:

E. S phase (short for Synthesis phase) is the specific part of interphase during which DNA replication occurs. During this phase, the cell synthesizes a complete copy of its DNA in preparation for cell division. Each chromosome is duplicated to ensure that both daughter cells receive an identical set of genetic instructions.

This is a crucial step because accurate DNA replication is necessary for genetic stability across generations of cells.

Explanation of Why the Other Options Are Incorrect:

A. Prophase – This is a stage of mitosis where chromosomes condense and the nuclear envelope begins to break down, but DNA replication is already complete by this point.

B. G1 phase – This is the first phase of interphase, where the cell grows and performs normal functions, but DNA is not yet being replicated.

C. G2 phase – This is the final phase of interphase after DNA replication, where the cell continues to grow and prepares for mitosis, but no new DNA is synthesized.

D. Cytokinesis – This is the physical division of the cytoplasm into two daughter cells after mitosis has been completed. DNA replication is not involved in this stage.

Summary:

DNA replication takes place during the S phase of the cell cycle, which is part of interphase and occurs before mitosis. Therefore, the correct answer is E. S phase.