Nokea
Which macromolecule is an example of a nucleic acid?
- A. Glucose.
- B. DNA.
- C. Albumin.
- D. HCl.
Correct Answer: B
Rationale: Correct Answer: B - DNA
Rationale:
1. Nucleic acids are macromolecules that store genetic information.
2. DNA (Deoxyribonucleic acid) is a type of nucleic acid that carries genetic instructions.
3. Glucose (A) is a carbohydrate, not a nucleic acid.
4. Albumin (C) is a protein, not a nucleic acid.
5. HCl (D) is a compound, not a nucleic acid.
Summary:
The correct answer is B because DNA is a nucleic acid that specifically functions to store genetic information, unlike the other choices which are not nucleic acids.
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Which of the following statements about enzymes is not true?
- A. They catalyze reactions
- B. They raise the activation energy needed
- C. They have an active site
- D. They are typically proteins
Correct Answer: B
Rationale: Enzymes function to catalyze reactions by lowering the activation energy required for the reaction to occur. Therefore, the statement that enzymes raise the activation energy needed is incorrect. Enzymes have an active site where substrates bind and undergo catalysis. Enzymes are typically proteins that act as biological catalysts.
A plant cell is placed in a solution and it shrinks from water loss. In what type of environment was the cell placed?
- A. Plasmolytic
- B. Hypertonic.
- C. Hypotonic.
- D. Isosmotic.
Correct Answer: B
Rationale: Correct Answer: B - Hypertonic
Rationale:
1. A hypertonic solution has a higher solute concentration than the cell, causing water to move out of the cell by osmosis.
2. Water loss results in the cell shrinking, as observed in this scenario.
3. Plasmolytic refers to the process of cytoplasm shrinking due to water loss in a hypertonic environment.
4. Hypotonic and isosmotic environments would not cause the cell to shrink from water loss.
Where in the cell does the Krebs cycle take place?
- A. mitochondrion.
- B. Nucleus.
- C. Cytoplasm.
- D. Chloroplast.
Correct Answer: A
Rationale:
What is the characteristic of the cell membrane consisting of a bilayer of phospholipids with proteins, cholesterol, and glycoproteins that creates a hydrophobic region between two layers of lipids?
- A. Impermeable
- B. Permeable
- C. Selectively permeable
- D. Selectively impermeable
Correct Answer: C
Rationale: The correct answer is 'C: Selectively permeable.' The cell membrane is selectively permeable because it allows certain molecules to pass through while restricting the passage of others. The hydrophobic region formed by the lipid bilayer makes it selectively permeable by controlling the movement of substances in and out of the cell. This selective permeability is vital for cellular functions, as it regulates the transport of essential molecules and maintains the internal environment required for proper cell operation and overall cellular homeostasis.
How many different types of nucleotides are there in DNA?
- A. one
- B. two
- C. four
- D. eight
Correct Answer: C
Rationale: The correct answer is C: four. DNA is composed of four different types of nucleotides: adenine (A), thymine (T), cytosine (C), and guanine (G). These nucleotides pair specifically (A with T and C with G) to form the double-stranded DNA structure.