Nokea
What is the function of platelets in the blood?
- A. To transport oxygen
- B. To clot blood
- C. To fight infection
- D. To transport nutrients
Correct Answer: B
Rationale: Platelets play a crucial role in clotting blood to prevent excessive bleeding when injuries occur. They are responsible for initiating the coagulation process by forming clots at the site of injury, sealing the damaged blood vessels, and preventing further blood loss. Platelets do not primarily transport oxygen, fight infection, or transport nutrients. While red blood cells are responsible for carrying oxygen, white blood cells are involved in fighting infections, and nutrients are transported by plasma, platelets' main function is related to hemostasis and wound healing.
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What are the small, finger-like projections in the small intestines called?
- A. Cilia
- B. Rugae
- C. Trachea
- D. Villi
Correct Answer: D
Rationale: The correct answer is D: Villi. Villi are small, finger-like projections in the small intestine that increase the surface area for absorption, aiding in the absorption of nutrients. Cilia (Choice A) are tiny hair-like structures found in various parts of the body but are not present in the small intestine. Rugae (Choice B) are folds in the mucosa of the stomach that allow for its expansion during digestion. The trachea (Choice C) is part of the respiratory system, responsible for carrying air to and from the lungs, and is not related to the small intestine.
Which of the following statements regarding the working of the heart is not correct?
- A. The atria contract, and the valves open to allow blood into the ventricles.
- B. The heartbeat begins when the heart muscles relax, and blood flows into the atria.
- C. The valves close to stop blood from flowing backward.
- D. The ventricles contract, forcing blood to leave the heart.
Correct Answer: B
Rationale: The correct answer is B because the heartbeat actually begins when the heart muscles relax, allowing the chambers to fill with blood. The contraction phase follows, which propels blood out of the heart. The other statements are accurate in describing the normal sequence of events in the heart's functioning: the atria contract to push blood into the ventricles, the valves close to prevent backflow of blood, and the ventricles contract to pump blood out of the heart.
Which of the following enzymes is responsible for adding a nucleotide to a growing DNA chain?
- A. Helicase
- B. Ligase
- C. Nuclease
- D. Polymerase
Correct Answer: D
Rationale: The correct answer is Polymerase. Polymerase is the enzyme responsible for adding nucleotides to a growing DNA chain during DNA replication. Helicase unwinds the DNA double helix to separate the DNA strands for replication, Ligase joins DNA fragments together by catalyzing the formation of phosphodiester bonds between them, and Nuclease cuts or degrades DNA strands. Therefore, choices A, B, and C are incorrect in the context of adding nucleotides to a growing DNA chain.
Where does glycolysis occur within the cell?
- A. Cytosol
- B. Nucleus
- C. Mitochondria
- D. Endoplasmic reticulum
Correct Answer: A
Rationale: Glycolysis occurs in the cytosol, the liquid component of the cytoplasm, not in the nucleus, mitochondria, or endoplasmic reticulum. It is the initial step in cellular respiration and involves the breakdown of glucose into pyruvic acid. The process takes place in the cytosol as it does not require membrane-bound organelles like the mitochondria or endoplasmic reticulum for its completion.
Where does the maturation of T-cells and the production of T-cell receptors occur?
- A. Thymus
- B. Spleen
- C. Lymph nodes
- D. Bone marrow
Correct Answer: A
Rationale: The correct answer is the Thymus. T-cells mature and develop their receptors in the thymus gland, making it a vital organ for the immune system. The thymus provides the necessary environment for T-cells to differentiate and acquire their specific receptors and functions, which are essential for their role in the adaptive immune response. The spleen, lymph nodes, and bone marrow are all important components of the immune system, but they do not primarily serve as sites for T-cell maturation and T-cell receptor production.