Nokea
Choose the two bases that have two carbon rings:
- A. Adenine
- B. Cytosine
- C. Thymine
- D. Guanine
Correct Answer: A
Rationale: Adenine and guanine have two carbon rings and are known as purines. These bases are found in nucleic acids such as DNA and RNA. Adenine (option A) and guanine (option D) are the correct choices as they both have two carbon rings in their molecular structure. Cytosine (option B) and thymine (option C) have a single carbon ring each, making them incorrect choices for bases with two carbon rings.
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How is the plasma membrane arranged?
- A. In a single layer made of proteins
- B. In a double layer made of proteins
- C. In a single layer of phospholipids
- D. In a double layer of phospholipids
Correct Answer: D
Rationale: The plasma membrane is arranged in a double layer of phospholipids, known as a phospholipid bilayer. This structure consists of two layers of phospholipid molecules with hydrophilic heads facing the exterior and hydrophobic tails facing the interior, providing a semipermeable barrier for the cell. Choice A is incorrect because the plasma membrane is not made of a single layer of proteins. Choice B is incorrect as the double layer is composed of phospholipids, not proteins. Choice C is incorrect as the plasma membrane is not made of a single layer of phospholipids but rather a double layer.
Which type of passive transport uses proteins that change shape to move a target molecule through the membrane?
- A. Diffusion
- B. Carrier proteins
- C. Channel proteins
- D. None of the above
Correct Answer: B
Rationale: The correct answer is B: Carrier proteins. Carrier proteins are involved in facilitated diffusion, a type of passive transport where specific target molecules are moved across the membrane with the help of proteins that change shape. These carrier proteins bind to the target molecule on one side of the membrane, undergo a conformational change, and then release the molecule on the other side. This process is crucial for the selective transport of certain molecules that cannot pass through the membrane by simple diffusion. Choices A and C are incorrect because diffusion and channel proteins do not involve proteins that change shape to transport target molecules selectively. Choice D is incorrect as carrier proteins fit the description provided in the question.
Where is DNA stored?
- A. The nucleus
- B. Ribosomes
- C. Endoplasmic reticulum
- D. Mitochondria
Correct Answer: A
Rationale: DNA is stored in the nucleus of a cell. The nucleus houses the cell's genetic material, including the DNA, which contains the instructions for building and operating the cell. The nucleus controls the activities of the cell and is essential for proper cell function and reproduction. Ribosomes are responsible for protein synthesis, not DNA storage. The endoplasmic reticulum is involved in protein and lipid synthesis, storage, and transport but does not store DNA. Mitochondria are known as the powerhouse of the cell, producing energy in the form of ATP, but they do not store DNA.
The difference between diploid and haploid is as follows:
- A. Diploid organisms are multicellular
- B. Diploid cells are somatic
- C. Diploid cells have two sets of homologous chromosomes
- D. More than one of the above is true
Correct Answer: D
Rationale: Option B correctly states that diploid cells are somatic cells that make up the body tissues and organs in an organism, while haploid cells are gametes involved in sexual reproduction. Option C accurately differentiates diploid and haploid cells based on their chromosome sets - diploid cells have two sets of homologous chromosomes (one from each parent), whereas haploid cells have one set of unpaired chromosomes. Therefore, the correct choice is D, as both statements in options B and C are accurate descriptions of the differences between diploid and haploid cells. Option A is incorrect because diploid and haploid refer to the number of sets of chromosomes in a cell, not whether the organism is multicellular or not.
Which of the following statements about the respiratory system is true?
- A. The respiratory system consists of all the organs involved in breathing
- B. Organs included in the respiratory system are the nose, pharynx, larynx, trachea, bronchi, and lungs
- C. The respiratory system conveys oxygen into our bodies and removes carbon dioxide from our bodies
- D. All of the Above
Correct Answer: D
Rationale: The correct answer is D. The respiratory system consists of all the organs involved in breathing, including the nose, pharynx, larynx, trachea, bronchi, and lungs. Additionally, the respiratory system is responsible for conveying oxygen into our bodies and removing carbon dioxide from our bodies. Therefore, all the statements provided are true, making option D the correct choice. Options A, B, and C are all accurate statements about the respiratory system, reinforcing the correctness of choosing option D.