Nokea
Which of the following pathways best represents the flow of blood from the human heart to organs?
- A. Blood pumped from the heart first enters arteries that then narrow to form arterioles that deliver blood to capillaries of the organs
- B. Blood pumped from the heart first enters veins that then narrow to form venules that deliver blood to arteries of the organ
- C. Blood pumped from the heart first enters arteries that then narrow to form arterioles that deliver blood to capillaries of the organs
- D. Blood pumped from the heart first enters arteries that then narrow to form veins that deliver blood to the organs
Correct Answer: C
Rationale: The correct pathway for the flow of blood from the human heart to organs involves a series of blood vessels. Blood is pumped from the heart into large arteries, which then branch into smaller arterioles. These arterioles deliver blood to capillaries located in the organs. Capillaries are essential for the exchange of nutrients, gases, and waste products between the blood and the tissues. This intricate network ensures efficient delivery of oxygen and nutrients to the organs and removal of waste products. Therefore, the correct sequence is for blood to flow from the heart, through arteries, then arterioles, and finally to capillaries in the organs for optimal exchange and organ function.
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A student conducts an experiment where they dissolve 1 g each of several substances in 50 mL of water. They have 12 identical plastic cups of water and place 1 g of salt into three of the cups, 1 g of sugar into three of the cups, and 1 g of baking soda into three of the cups. The three remaining cups contain only water. All the cups are put in a freezer, and the temperature of the solution in each cup is recorded every 15 minutes for 4 hours. What question is the student most likely investigating?
- A. What effect do different concentrations of solute have on the freezing point of water?
- B. How does the volume of water affect the rate at which it cools?
- C. What effect does cooling have on the solubility of different solutes?
- D. How is the cooling rate of water affected by different solutes?
Correct Answer: A
Rationale: The student is most likely investigating the effect of different concentrations of solutes (salt, sugar, baking soda) on the freezing point of water. By monitoring the temperature changes during freezing, the student can observe how each solute affects the freezing point. This experiment helps understand the concept of colligative properties, where the presence of solutes lowers the freezing point of a solvent like water. Therefore, the correct answer is A: 'What effect do different concentrations of solute have on the freezing point of water?'
Which of the following molecules are found in substantial quantities in both the cell membrane and DNA?
- A. Nitrogenous bases
- B. Steroids
- C. Phosphate groups
- D. Lipids
Correct Answer: C
Rationale: Phosphate groups are crucial components of the DNA backbone, forming the phosphodiester bonds between nucleotides. In DNA, the phosphate group connects the 3' carbon of one nucleotide to the 5' carbon of the next nucleotide. In the cell membrane, phospholipids are the main components, with phosphate groups present in the hydrophilic head of the molecule. This key structural feature allows phospholipids to form the lipid bilayer that comprises the cell membrane. While nitrogenous bases are essential components of DNA, they are not found in substantial quantities in the cell membrane. Steroids are not typically abundant in either the cell membrane or DNA. Lipids, although present in the cell membrane, do not have the same substantial presence in DNA as phosphate groups do.
How many times stronger is the hydrogen-ion concentration of a pH 4 solution compared with a pH 9 solution?
- A. 50
- B. 100,000
- C. 0.000001
- D. 5
Correct Answer: B
Rationale: The pH scale measures the concentration of hydrogen ions in a solution, where each pH unit change represents a tenfold difference in concentration. In this case, the pH 4 solution is 5 units lower than the pH 9 solution. Therefore, the difference of 5 pH units translates to a 10^5 times (or 100,000 times) increase in hydrogen-ion concentration in the pH 4 solution compared to the pH 9 solution. The pH scale is logarithmic, with each unit representing a tenfold change, so a 5-unit difference results in a 100,000-fold difference in hydrogen-ion concentration. Hence, option B, 100,000, is the correct answer.
What is a common cause of a tsunami?
- A. Earthquakes
- B. Sunspot activity
- C. Lightning strikes
- D. Flooding
Correct Answer: A
Rationale: Earthquakes are a common cause of tsunamis. When an earthquake occurs under the ocean, it can displace a large volume of water, triggering a series of powerful waves known as a tsunami. Sunspot activity, lightning strikes, and flooding do not directly cause tsunamis. Therefore, the correct answer is earthquakes, as they are the primary geological event that leads to the formation of tsunamis.
Which of the following is an example of a biological macromolecule?
- A. Monosaccharide
- B. Protein
- C. Nucleic acid
- D. Amino acid
Correct Answer: B
Rationale: The correct answer is B, 'Protein.' Proteins are biological macromolecules composed of amino acid chains. They play vital roles in cellular functions, including catalyzing reactions, providing structural support, and acting as signaling molecules. Monosaccharides are simple sugars, nucleic acids are genetic materials such as DNA and RNA, and amino acids are the fundamental units that make up proteins.