Nokea
Why is DNA crucial for the metabolic activities of the cell?
- A. It initiates cellular mitosis.
- B. It provides cell wall stability.
- C. It increases glucose absorption.
- D. It controls the synthesis of enzymes.
Correct Answer: D
Rationale: DNA is crucial for the metabolic activities of the cell because it contains the genetic information necessary to regulate the synthesis of enzymes. Enzymes are essential for catalyzing biochemical reactions involved in metabolic processes within the cell. DNA controls the production of enzymes, which are vital for driving various metabolic pathways. Therefore, the correct answer is D, as DNA's role in controlling enzyme synthesis is fundamental for the cell's metabolic activities.
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Which base has two carbon rings?
- A. N
- B. C
- C. T
- D. G
Correct Answer: D
Rationale: The correct answer is G. In organic chemistry, the base Guanine (G) contains two carbon rings in its structure. Guanine is one of the four main nucleobases found in DNA and RNA. The other options, N, C, and T, do not have two carbon rings in their structures. Therefore, Guanine is the only option that fits the description of a base with two carbon rings.
Cells reproduce by different processes, all of which fall into what two categories?
- A. Sexual reproduction and binary fission
- B. Sexual reproduction and asexual reproduction
- C. Asexual reproduction and binary fission
- D. Asexual reproduction and mitosis
Correct Answer: B
Rationale: Cells can reproduce through sexual reproduction, involving the fusion of gametes, and asexual reproduction, which does not involve the fusion of gametes. Binary fission is a specific type of asexual reproduction where a cell divides into two identical cells. Therefore, the correct answer is B as it encompasses the broad categories of cellular reproduction processes, covering both sexual and asexual reproduction.
What structure in a plant cell is surrounded by a double membrane and contains most of the genetic information used to control the cell?
- A. Mitochondrion
- B. Nucleus.
- C. Chromatin.
- D. Chromosome.
Correct Answer: B
Rationale: Rationale: The correct answer is B: Nucleus. The nucleus is surrounded by a double membrane and contains most of the genetic information in the form of DNA, which controls the cell's activities. Mitochondria (A) are involved in energy production, chromatin (C) is a complex of DNA and proteins within the nucleus, and chromosomes (D) are condensed structures of DNA found in the nucleus during cell division. Therefore, the nucleus is the structure that fits the description provided in the question.
In a Punnett square, a capital letter represents what type of allele?
- A. Dominant.
- B. Ryeesive.
- C. Homozygous.
- D. Heterozygous.
Correct Answer: A
Rationale: Correct Answer: A: Dominant.
Rationale:
1. In a Punnett square, capital letters denote dominant alleles.
2. Dominant alleles are expressed in the phenotype over recessive alleles.
3. This representation helps predict the possible offspring genotypes.
4. Choice B is incorrect as it's a misspelling of 'Recessive.'
5. Choices C and D refer to genotype combinations, not allele types.
Summary:
The capital letter in a Punnett square signifies a dominant allele that will be expressed in the offspring's phenotype. This helps in predicting genetic outcomes accurately.
What type of bond holds water molecules together?
- A. Ionic
- B. Covalent
- C. Hydrogen
- D. Molecular
Correct Answer: C
Rationale: The correct answer is 'Hydrogen.' Water molecules are held together by hydrogen bonds. These bonds form between the slightly positive hydrogen atom of one water molecule and the slightly negative oxygen atom of another water molecule. While hydrogen bonds are weaker than covalent bonds, they play a crucial role in various biological processes, such as the cohesion of water molecules and the unique properties of water as a solvent.