what is the structure of dna

ATI TEAS 7

ATI TEAS Science Practice Test

1. What is the structure of DNA?

A. Single-stranded, linear
B. Double-stranded, linear
C. Double-stranded, helix
D. Single-stranded, helix

Correct answer: C

Rationale: The correct answer is C: Double-stranded, helix. DNA is structured as a double helix formed by two strands of nucleotides. The nucleotides are paired with complementary bases (A-T and C-G) in the center, held together by hydrogen bonds. This double-stranded helical structure is a fundamental characteristic of DNA and essential for its function in storing genetic information. Choices A, B, and D are incorrect because DNA is not single-stranded; it consists of two strands that run antiparallel to each other and are connected via hydrogen bonds. Additionally, DNA does not have a linear structure but rather a helical one, providing stability and protection to the genetic information it carries.

2. Where in the cell are proteins modified, sorted, and packaged for transport?

A. Ribosomes
B. Golgi apparatus
C. Endoplasmic reticulum (ER)
D. Lysosomes

Correct answer: B

Rationale: The Golgi apparatus is the cellular organelle responsible for modifying, sorting, and packaging proteins for transport within the cell or for secretion outside the cell. Ribosomes are not involved in modifying, sorting, or packaging proteins; they are responsible for protein synthesis. The endoplasmic reticulum (ER) is primarily involved in protein synthesis and folding, rather than modification and packaging for transport. Lysosomes function in breaking down cellular waste rather than modifying, sorting, or packaging proteins for transport.

3. How can you differentiate between a bacterial and viral infection based solely on symptoms?

A. It's impossible to differentiate solely based on symptoms.
B. Bacterial infections typically respond well to antibiotics, while viral infections don't.
C. Bacterial infections usually cause fever, while viral infections don't.
D. Viral infections often present with respiratory symptoms like a cough, while bacterial infections don't.

Correct answer: A

Rationale: It is impossible to differentiate between a bacterial and viral infection based solely on symptoms because many symptoms overlap between the two types of infections. Symptoms like fever, cough, and others can be present in both bacterial and viral infections. Additional diagnostic tests such as cultures or blood tests are often needed to determine the cause of the infection accurately. Relying only on symptoms can lead to misdiagnosis and inappropriate treatment. Choices B, C, and D are incorrect because they oversimplify the differentiation process and do not encompass the complexity of symptoms associated with bacterial and viral infections. While it is true that bacterial infections may respond to antibiotics and some differences in symptoms may be observed between bacterial and viral infections, these are not definitive indicators without proper diagnostic tests.

4. Which of the following is the intricate network of blood vessels responsible for transporting blood throughout the body?

A. Lymphatic system
B. Circulatory system
C. Nervous system
D. Respiratory system

Correct answer: B

Rationale: The circulatory system, comprising the heart, blood vessels (arteries, veins, and capillaries), and blood, is responsible for transporting blood, oxygen, nutrients, and waste products throughout the body. The lymphatic system aids in maintaining fluid balance and fighting infections; the nervous system transmits signals. The respiratory system facilitates the exchange of oxygen and carbon dioxide in the body, which is distinct from the circulatory system's role in blood transport. Therefore, the correct answer is the Circulatory system (Choice B). Choices A, C, and D are incorrect as they do not pertain to the intricate network of blood vessels responsible for transporting blood throughout the body.

5. Which level of protein structure is defined by the folds and coils of the protein's polypeptide backbone?

A. Primary
B. Secondary
C. Tertiary
D. Quaternary

Correct answer: B

Rationale: The correct answer is B: Secondary. The secondary structure of a protein is defined by the folds and coils of the protein's polypeptide backbone. This level of structure is characterized by the formation of alpha helices and beta sheets, which are stabilized by hydrogen bonds between amino acids along the polypeptide chain. Choice A, Primary, refers to the linear sequence of amino acids in the protein. Choice C, Tertiary, involves the 3D folding of the entire polypeptide chain. Choice D, Quaternary, pertains to the arrangement of multiple polypeptide subunits in a protein complex.