Nokea
Which statement below correctly describes the movement of molecules in the body and in relation to the external environment?
- A. Osmosis is the movement of a solution from an area of low solute concentration to an area of high solute concentration.
- B. Diffusion is the process in which oxygen moves from the lungs into the bloodstream.
- C. Dissipation is the transport of molecules across a semipermeable membrane from low to high concentration.
- D. Reverse osmosis is the movement of molecules in a solution from high concentration to low concentration.
Correct Answer: B
Rationale: The correct answer is B. Diffusion is the process where molecules move from an area of higher concentration to an area of lower concentration. In the context of the lungs, oxygen moves from the alveoli in the lungs to the bloodstream through diffusion. Choice A is incorrect as osmosis involves the movement of water across a semipermeable membrane from an area of low solute concentration to an area of high solute concentration. Choice C is incorrect because dissipation does not refer to a specific biological process related to molecule movement. Choice D is incorrect as reverse osmosis is a process where solvent moves from an area of high solute concentration to an area of low solute concentration, not the movement of molecules within a solution.
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What correction should the student make to the hypothesis: Lengthening the string of the pendulum increases the time it takes the ball to make one complete period?
- A. Turn it into an 'if-then' statement.
- B. Change 'will increase' to 'increases.'
- C. Switch the order of the sentence so that the phrase about the period comes first.
- D. No corrections are needed.
Correct Answer: A
Rationale: The correct answer is A. A hypothesis should be structured as an 'if-then' statement for clarity. This format helps to clearly establish the relationship between the variables and the expected outcome. In this case, the student should frame the hypothesis in a way that if a specific action is taken (lengthening the string), then a specific outcome is expected (increasing the time it takes for the ball to make one complete period). 'If-then' statements are fundamental in hypothesis construction as they clearly define the cause and effect relationship being tested. Choice B is incorrect because changing 'will increase' to 'increases' does not address the structural issue of the hypothesis. Choice C is incorrect as switching the order of the sentence does not fundamentally alter the clarity of the hypothesis. Choice D is incorrect as the hypothesis structure can be improved for better understanding and testing, making correction necessary.
A substance is only considered acidic if it has a pH less than what?
- A. 12
- B. 9
- C. 7
- D. 4
Correct Answer: C
Rationale: A substance is considered acidic if its pH is less than 7. pH values below 7 indicate acidity, while pH values above 7 indicate alkalinity or basicity. Substances with a pH less than 7 are categorized as acidic, not above it. Therefore, a substance is classified as acidic if its pH is less than 7, making choice C the correct answer. Choices A, B, and D are incorrect because a pH of 12, 9, and 4, respectively, are all above 7, and therefore not indicative of acidity.
How do hydrogen bonds in water affect its characteristics?
- A. Hydrogen bonds are not polar enough to attract non-polar molecules.
- B. Hydrogen bonds cause water to be less dense when it is a solid than when it is a liquid.
- C. Hydrogen bonds cause water to have high surface tension, allowing some organisms to move across it.
- D. Hydrogen bonds cause water to be a good solvent.
Correct Answer: C
Rationale: Hydrogen bonds in water contribute to its high surface tension, enabling some organisms to move across the water's surface. This property is essential for certain insects and small animals that rely on surface tension to move or stay afloat on water. Choice A is incorrect because hydrogen bonds are polar and can attract polar and other charged molecules. Choice B is incorrect as hydrogen bonds make ice less dense than liquid water, which is a unique property. Choice D is incorrect as the ability of water to act as a good solvent is primarily due to its polarity, not just hydrogen bonding.
Which of the following is NOT part of the circulatory system?
- A. Kidneys
- B. Heart
- C. Blood
- D. Blood vessels
Correct Answer: A
Rationale: The correct answer is A: Kidneys. The kidneys are part of the urinary system, responsible for filtering waste and maintaining fluid balance in the body. In the circulatory system, the heart pumps blood, blood carries oxygen and nutrients, and blood vessels transport blood throughout the body. Choices B, C, and D are all components of the circulatory system, making the kidneys the correct choice as it belongs to the urinary system.
Fill in the blanks in the following sentence: Enzymes are ________ molecules that serve as _______ for certain biological reactions.
- A. complex; suppressors
- B. acidic; triggers
- C. small; targets
- D. large; catalysts
Correct Answer: D
Rationale: Enzymes are large molecules that act as catalysts, accelerating chemical reactions by lowering the activation energy required for the reactions to occur. In the context of biological reactions, enzymes function as catalysts, not suppressors, triggers, or targets. The use of 'large' and 'catalysts' accurately describes the nature and role of enzymes in facilitating biological processes.