Nokea
How does ingested food move through the digestive tract?
- A. Chewing, digestion, absorption
- B. Swallowing, peristalsis, segmentation
- C. Swallowing, mastication, defecation
- D. Digestion, absorption, excretion
Correct Answer: B
Rationale: The correct answer is B: Swallowing, peristalsis, segmentation. Food moves through the digestive tract by first being swallowed, then undergoing peristalsis (wave-like movements that propel food along the digestive tract), and finally undergoing segmentation (mixing movements in the intestines). Chewing and digestion occur in the mouth and stomach, respectively, while absorption and excretion happen later in the digestive process. Choice A is incorrect as absorption is a later stage in the process. Choice C is incorrect because defecation is the elimination of waste, not the movement of food. Choice D is incorrect as excretion is the elimination of waste products, not the movement of ingested food through the digestive tract.
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Salts like sodium iodide (NaI) and potassium chloride (KCl) use what type of bond?
- A. Ionic bonds
- B. Disulfide bridges
- C. Covalent bonds
- D. London dispersion forces
Correct Answer: A
Rationale: Salts like sodium iodide (NaI) and potassium chloride (KCl) use ionic bonds. Ionic bonds are formed between atoms with significantly different electronegativities, leading to the transfer of electrons from one atom to another. In the case of NaI and KCl, sodium (Na) and potassium (K) are metals that easily lose electrons to become positively charged ions, while iodide (I) and chloride (Cl) are nonmetals that readily accept electrons to become negatively charged ions. The attraction between the oppositely charged ions forms the ionic bond, which holds the compound together in a lattice structure. Disulfide bridges (option B) are covalent bonds formed between sulfur atoms in proteins, not in salts. Covalent bonds (option C) involve the sharing of electrons between atoms and are typically seen in molecules, not ionic compounds like salts. London dispersion forces (option D) are weak intermolecular forces that occur between all types of molecules but are not the primary type of bond in salts like NaI and KCl.
What is the role of enzymes in the body?
- A. To transport oxygen
- B. To speed up chemical reactions
- C. To regulate body temperature
- D. To store energy
Correct Answer: B
Rationale: Enzymes act as biological catalysts that speed up chemical reactions in the body. They lower the activation energy required for reactions to occur, thus facilitating processes like digestion, metabolism, and other essential functions. Choice A is incorrect as the transportation of oxygen is primarily carried out by red blood cells. Choice C is incorrect as the regulation of body temperature involves mechanisms such as sweating and shivering. Choice D is incorrect as energy storage is mainly performed by molecules like glycogen and triglycerides.
What controls muscles by sending electrical impulses to the muscles?
- A. Blood vessels
- B. Nerves
- C. Hormones
- D. Neurons
Correct Answer: B
Rationale: Nerves control muscles by transmitting electrical impulses that initiate muscle contractions. Blood vessels are responsible for transporting blood, not controlling muscles. Hormones are chemical messengers produced by glands to regulate bodily functions, not specifically controlling muscles. Neurons are the basic building blocks of the nervous system that transmit signals, but nerves are the specific structures that control muscles by sending electrical impulses.
What is the main function of the skeletal system?
- A. To regulate blood pressure
- B. To protect internal organs
- C. To produce hormones
- D. To fight infection
Correct Answer: B
Rationale: The main function of the skeletal system is to provide structural support for the body, protect internal organs, facilitate movement, and produce blood cells in the bone marrow. Choice A, 'To regulate blood pressure,' is incorrect as blood pressure regulation is primarily controlled by the circulatory and endocrine systems. Choice C, 'To produce hormones,' is incorrect as hormone production is mainly carried out by the endocrine system. Choice D, 'To fight infection,' is incorrect as the immune system is responsible for fighting infections, not the skeletal system.
What is the small repeating unit in the contractile apparatus of skeletal muscle?
- A. Myofibril
- B. Actin
- C. Sarcomere
- D. Myosin
Correct Answer: C
Rationale: The correct answer is 'Sarcomere.' The sarcomere is the smallest repeating unit within myofibrils and is responsible for muscle contraction in skeletal muscle. It consists of overlapping actin and myosin filaments arranged in a highly organized structure that allows for the sliding of filaments during muscle contraction. 'Myofibril' (choice A) is incorrect because it is a larger structure composed of sarcomeres. 'Actin' (choice B) and 'Myosin' (choice D) are incorrect as they are individual proteins that are components of the sarcomere, not the smallest repeating unit itself.