Nokea
What type of bond in the DNA nucleotide base holds the strands together?
- A. Hydrogen
- B. Sodium chloride
- C. Copper
- D. Potassium bromide
Correct Answer: A
Rationale: Hydrogen bonds are the type of bonds that hold the two strands of DNA together by connecting complementary nitrogenous bases (adenine with thymine and cytosine with guanine). These weak bonds allow the DNA strands to separate during replication and transcription while providing stability to the overall structure of the DNA molecule.
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Osmotic pressure is the tendency for a single solution to absorb what substance?
- A. Sodium.
- B. Water.
- C. Positive ions.
- D. Negative ions.
Correct Answer: B
Rationale: The correct answer is B: Water. Osmotic pressure is the pressure required to prevent the flow of water across a semipermeable membrane to achieve equilibrium. Water moves from a region of lower solute concentration to higher solute concentration to balance the concentration on both sides of the membrane. Therefore, the tendency for a solution to absorb water is what osmotic pressure refers to. Choices A, C, and D are incorrect because osmotic pressure is specifically related to the movement of water molecules, not sodium, positive ions, or negative ions.
Where in the cell does the Krebs cycle take place?
- A. mitochondrion.
- B. Nucleus.
- C. Cytoplasm.
- D. Chloroplast.
Correct Answer: A
Rationale:
Which disease is caused by a bacterium?
- A. Mumps
- B. Strep throat
- C. AIDS (HIV+)
- D. Common cold
Correct Answer: B
Rationale: Strep throat is caused by the bacterium Streptococcus pyogenes. Unlike mumps, which is a viral infection, AIDS caused by the HIV virus, and the common cold usually caused by rhinoviruses, strep throat is specifically a bacterial infection that can be treated with antibiotics.
Which of the following statements is false?
- A. Animal cells use lysosomes to break down old cells
- B. Animal cells use chloroplasts to gain energy
- C. Plant cells have a cell wall to maintain structure
- D. All of the above are true
Correct Answer: B
Rationale: The correct statement is B. Animal cells do not use chloroplasts to gain energy; instead, they rely on mitochondria for energy production through cellular respiration. Lysosomes in animal cells are responsible for breaking down old cells and cellular waste. Plant cells have a cell wall to provide structural support and protection. Therefore, option B is false, as animal cells do not utilize chloroplasts for energy.
What process of division do sex cells undergo?
- A. Mitosis.
- B. Binary fission.
- C. Facilitated division.
- D. Melosis.
Correct Answer: D
Rationale: The correct answer is D: Meiosis. Sex cells undergo meiosis, which is a specialized form of cell division that reduces the chromosome number by half to produce gametes (sperm and egg cells). This process involves two rounds of division (meiosis I and II) resulting in four haploid daughter cells.
A: Mitosis is a form of cell division where a cell divides to produce two identical diploid daughter cells, not sex cells.
B: Binary fission is a form of asexual reproduction in prokaryotes, not a process of division for sex cells.
C: Facilitated division is not a recognized term in biology and is not related to the division of sex cells.