Question

1. which of the following macromolecules are the most functionally diverse? (a) carbohydrates; (b) proteins; (c) nucleic acids; (d) lipids. 16. which of the following are completely absent in biological membranes? (a) carbohydrates; (b) proteins; (c) nucleic acids; (d) lipids. 17. the facts that water drops form spheres, is able to hold large amount of heat and is more dense than its solid form (ice) are all because water molecules form a. covalent bonds with each other. b. polar charges. c. hydrogen bonds with each other. 18. even if a molecule has ionic bonds, such as sodium (na⁺) chloride (cl⁻), which forms sodium chloride (table salt), water can dissolve it because water: a. is able to hold tremendous amounts of heat. b. is a polar molecule - hence can dissolve many other kinds of molecules. c. has high surface tension. 19. a solution that has a low ph of about 2 is said to be: (a) acidic; (b) basic; (c) neutral. 20. a solution whose ph is 4 is ____ more acidic than a solution whose ph is 6. (a) 1 x; (b) 10 x; (c) 100 x; (d) 1,000 x. 21. an acidic substance releases ____ into solution. (a) hydrogen ions; (b) hydroxyl ions; (c) both hydrogen ions and hydroxyl ions; (d) neither of the above. 22. in a solution of nacl in water, what part of the water molecules would be pointed toward the anion? (a) the oxygens; (b) the hydrogens; (c) only one of the hydrogens of each water molecule; (d) no preference - orientation would just be random. 23. which of the following is the basic unit of life? (a) organ; (b) tissue; (c) organism; (d) cell. 24. the cytoskeleton is made of (a) lipids; (b) nucleic acids; (c) proteins; (d) carbohydrates. 25. the building blocks of proteins are (a) amino acids; (b) fatty acids; (c) glucose; (d) nucleotides. 26. which of the following types of proteins make chemical reactions possible? (a) antibodies; (b) carrier proteins; (c) enzymes; (d) structural proteins. 27. which of the following types of proteins are involved in immune defense of the organism? (a) antibodies; (b) carrier proteins; (c) enzymes; (d) structural proteins. 28. which of the following proteins in biological membranes either brings ionic solutes into the cell or extrudes them? (a) channels or pores; (b) cytoskeletal proteins; (c) motor proteins; (d) antibodies.

Explanation:

1. Proteins have the most diverse functions among macromolecules, such as catalysis, transport, and structural support.
2. Nucleic acids are absent in biological membranes which are mainly composed of lipids and proteins with some carbohydrates.
3. Water's properties like spherical - drop formation, high heat - holding capacity, and higher density than ice are due to hydrogen bonding between water molecules.
4. Water is a polar molecule, so it can dissolve ionic compounds like sodium chloride through ion - dipole interactions.
5. A low pH (around 2) indicates an acidic solution.
6. The pH scale is logarithmic. A difference of 2 pH units means a 100 - fold difference in hydrogen ion concentration, so a pH 4 solution is 100 times more acidic than a pH 6 solution.
7. An acidic substance releases hydrogen ions into solution.
8. In a NaCl - water solution, the anions (Cl⁻) are attracted to the positive end of water molecules, which is the hydrogen part.
9. The cell is the basic unit of life.
10. The cytoskeleton is made of proteins.
11. Amino acids are the building blocks of proteins.
12. Enzymes are proteins that catalyze chemical reactions.
13. Antibodies are proteins involved in immune defense.
14. Channels or pores in biological membranes can transport ionic solutes into or out of the cell.

Answer:

1. B. proteins
2. C. nucleic acids
3. C. Hydrogen bonds with each other
4. B. Is a polar molecule - hence can dissolve many other kinds of molecules
5. A. acidic
6. C. 100 X
7. A. hydrogen ions
8. B. the hydrogens
9. D. cell
10. C. proteins
11. A. amino acids
12. C. enzymes
13. A. antibodies
14. A. Channels or pores