BIOL 107 606 Fundamentals of Microbiology

Correct Answer  A: Golgi apparatus

Why this is correct:

The arrow in the image is pointing to a stack of flattened, membrane-bound sacs that resemble a curved ribbon or folded pancakes — a classic depiction of the Golgi apparatus in a typical animal cell diagram. The Golgi apparatus is located near the endoplasmic reticulum and is responsible for modifying, sorting, and packaging proteins and lipids for secretion or for use within the cell. It does not have ribosomes on its surface and has a smooth appearance.

Why the other options are wrong:

B. rough endoplasmic reticulum

Incorrect. The rough ER is typically found close to the nucleus and is studded with ribosomes, giving it a rough appearance. It is involved in protein synthesis. The structure indicated by the arrow does not have ribosomes and is not directly attached to the nucleus.

C. mitochondria

Incorrect. Mitochondria are usually shown as oval or bean-shaped organelles with a double membrane, including an inner folded membrane called cristae. The structure indicated does not match this appearance and is not involved in energy production.

D. lysosomes

Incorrect. Lysosomes are small, spherical vesicles that contain digestive enzymes. They are usually drawn as tiny dots or round bodies scattered throughout the cytoplasm, not as large, folded stacks like the Golgi apparatus.

Summary:

The cellular structure pointed to by the arrow is the Golgi apparatus, which is involved in the processing and packaging of proteins and lipids. Its distinctive stack-like appearance and location away from the nucleus confirm its identity. Therefore, the correct answer is A. Golgi apparatus.

Correct Answer A: Hypertonic

Detailed Explanation of the Correct Answer:

A hypertonic solution has a higher solute concentration compared to the inside of the cell. The normal internal concentration of NaCl inside a red blood cell is about 0.9% NaCl. The solution outside the cell in the image is 12% NaCl, which is significantly higher.

Because of this concentration difference, water moves out of the cell via osmosis to balance the concentration gradient. As a result, the red blood cell will shrink or crenate in a hypertonic environment.

Explanation of Why the Other Options Are Incorrect:

B. Hypotonic – A hypotonic solution has a lower solute concentration than the inside of the cell. This causes water to enter the cell, potentially leading to swelling or lysis. Since 12% NaCl is much higher than the internal 0.9%, the solution is not hypotonic.

C. Isotonic – An isotonic solution has the same solute concentration as inside the cell (around 0.9% NaCl). This maintains equilibrium with no net water movement. Because 12% NaCl is far more concentrated, it is not isotonic.

Summary:

The 12% NaCl solution outside the red blood cell is significantly more concentrated than the inside (0.9%), making it a hypertonic solution. This causes water to move out of the cell, leading it to shrink. Therefore, the correct answer is A. Hypertonic.

Correct Answer E: Atoms 2 and 3

Explanation:

Isotopes are atoms that have the same number of protons (same atomic number) but a different number of neutrons. This means they are the same element but differ in atomic mass.

Atom #2 and Atom #3 both have 10 protons, meaning they are the same element. However:

Atom #2 has 11 neutrons

Atom #3 has 10 neutrons

Because they differ in neutrons but have the same number of protons, they are isotopes.

Why the other options are incorrect:

A) Atoms 1 and 4:

Both have 11 protons, but also have different numbers of electrons (10 vs. 11). This makes them ions, not isotopes.

B) Atoms 1 and 2:

Different number of protons (11 vs. 10), so they are not the same element and therefore cannot be isotopes.

C) Atoms 1 and 3:

Different number of protons (11 vs. 10), so they are not isotopes.

D) Atoms 3 and 4:

Different number of protons (10 vs. 11), so they are different elements, not isotopes.

Correct Answer D: 0%

Explanation:

Let’s assign alleles:

A = normal (healthy) allele

a = sickle cell allele (recessive)

Mother’s genotype: Aa (heterozygous — carrier)

Father’s genotype: AA (homozygous dominant — healthy)

Results:

50% chance the child will be AA (healthy, not a carrier)

50% chance the child will be Aa (carrier, but healthy)

0% chance the child will be aa (have the disease)

Since two copies of the sickle cell allele (aa) are required for the disease, and the father contributes only A alleles, no child can inherit two "a" alleles.

So, the probability the child will have sickle cell anemia is 0%.

Correct Answer: Amine

Explanation:

The amine group (–NH₂) is a functional group found in amino acids and many organic compounds. It consists of a nitrogen atom attached to hydrogen atoms and possibly a carbon chain. This group is responsible for the basic properties of amino acids.

Why the other options are incorrect:

Hydroxyl: An –OH group alone, not what is highlighted here.

Carbonyl: A carbon double-bonded to an oxygen (C=O), but the question focuses on the –NH₂ part.

Phosphate: Involves phosphorus atoms, which are not present in this structure.

Correct Answer C: He HAS a distinct pointing of his hair in the center of his forehead

Detailed Explanation of the Correct Answer:

C. He HAS a distinct pointing of his hair in the center of his forehead is correct because the man is heterozygous (Ww) for a dominant trait. Since widow’s peak is dominant, only one dominant allele (W) is needed for the trait to be expressed. Thus, regardless of the presence of the recessive allele (w), he will show the widow’s peak phenotype.

Explanation of Why the Other Options Are Incorrect:

A. ww (both lowercase) – This represents the genotype, not the phenotype, and it refers to someone who is homozygous recessive and would not show a widow’s peak.

B. He does NOT have a distinct pointing of his hair in the center of his forehead – This would only be true for someone with a ww genotype, which is not the case here.

D. WW (both uppercase) – This represents a homozygous dominant genotype, not the phenotype, and while it would also result in a widow's peak, it's not the man’s genotype.

E. Ww – This is the genotype, not the phenotype. It shows that the man is heterozygous, but the question asks for the phenotype (what is physically seen).

Summary:

A heterozygous individual (Ww) for a dominant trait like widow's peak will show the dominant phenotype, which is a distinct point in the hairline. Therefore, the correct answer is C. He HAS a distinct pointing of his hair in the center of his forehead.

Correct Answer C: To allow for survival under harsh conditions

Explanation:

Bacterial endospores are highly resistant, dormant structures formed by certain bacteria (e.g., Bacillus and Clostridium species) when environmental conditions become unfavorable. Endospores enable the bacteria to survive extreme conditions such as:

High temperatures

Desiccation (drying out)

UV radiation

Chemical disinfectants

Lack of nutrients

When conditions improve, the endospore can germinate back into a vegetative (active) bacterial cell.

Why the other options are incorrect:

A) For protection from phagocytosis:

Endospores are not primarily for avoiding immune cells; capsules serve that purpose better.

B) To pass on new genetic information from one cell to another:

That function is done through conjugation, transformation, or transduction, not endospores.

D) To allow for extra nutrient storage within the cell:

Endospores are not storage bodies; their main role is survival, not nutrient storage.

Correct answer B: photosynthesis

Detailed explanation:

In prokaryotes, specifically cyanobacteria, thylakoid membranes are infoldings of the plasma membrane. These specialized structures contain the photosynthetic machinery necessary for photosynthesis. The thylakoid membranes house chlorophyll and other pigments that absorb light energy and convert it into chemical energy during the light-dependent reactions of photosynthesis.

Photosynthesis involves the conversion of light energy into chemical energy, which is stored in the form of ATP and NADPH. The thylakoid membranes play a crucial role in this process, facilitating the reactions necessary for synthesizing glucose and other organic compounds.

In eukaryotic cells, such as plants, the equivalent of the thylakoid membranes is found in the chloroplasts, where photosynthesis also occurs. However, in prokaryotes, the thylakoid membranes are directly part of the plasma membrane, allowing these organisms to carry out photosynthesis without the need for specialized organelles like chloroplasts.

Why the other options are incorrect:

A osmosis

Osmosis is the process of water movement across a semipermeable membrane. This process occurs in various types of cells but is not specifically linked to thylakoid membranes. Osmosis is a passive transport process and does not directly involve photosynthesis.

C respiration

Respiration in prokaryotes typically occurs across the plasma membrane or in the cytoplasmic membrane. While some respiratory enzymes may be present in the membrane, respiration is a separate metabolic process from photosynthesis and does not directly involve thylakoid membranes.

D thermotaxis

Thermotaxis refers to the movement of an organism in response to temperature changes. This process is not related to the function of thylakoid membranes, which are specifically involved in photosynthesis, not in movement or temperature response.

Summary:

Thylakoid membranes in prokaryotes, particularly cyanobacteria, are responsible for photosynthesis by housing the necessary pigments and enzymes that capture light energy and convert it into chemical energy. Therefore, the correct answer is B photosynthesis.

Correct Answer A: False

Detailed Explanation of the Correct Answer:

False is the correct answer because while glucose is a primary and preferred source of energy for many cells, it is not the only molecule that can be used to produce ATP. Cells can metabolize a variety of other molecules when glucose is unavailable, including:

Fatty acids – Broken down through beta-oxidation to produce acetyl-CoA, which enters the Krebs cycle.

Amino acids – Can be deaminated and converted into intermediates that enter glycolysis or the Krebs cycle.

Glycerol – From triglycerides, can be converted into glycolytic intermediates.

Other sugars – Like fructose and galactose, can be converted into intermediates of glycolysis.

These alternative pathways still lead to the electron transport chain, where the majority of ATP is generated.

Summary:

Cells have multiple metabolic pathways to generate ATP from various biomolecules, not just glucose. Therefore, the correct answer is A. False.