Question

1. why is carbon so important in the formation of macromolecules? (1.2)

a. carbon atoms can form up to two ionic bonds with a variety of elements, contributing to the stability of macromolecules.
b. carbon atoms can only bond with other carbon atoms, creating stable, long chains
c. carbon atoms are the largest and most reactive, making them ideal for forming the backbone of macromolecules.
d. carbon can form up to four covalent bonds, allowing for the construction of diverse and complex molecular structures.

1. in an experiment, scientists measured the temperature changes in two different environments: one containing only water and the other containing an equal volume of sand. both environments were exposed to the same amount of heat energy for a specified period. the results showed that the temperature of the water increased by 2°c, while the temperature of the sand increased by 10°c. why did the water show a smaller temperature increase compared to the sand? (1.1)

a. water has a high specific heat, allowing it to absorb a large amount of heat with only a slight change in temperature.
b. water has a higher density than sand, which helps it retain heat more effectively.
c. water reflects more heat energy than sand, resulting in a smaller temperature increase.
d. water has a higher heat of vaporization than sand, which allows it to absorb more heat energy before its temperature rises significantly.

1. which of the following correctly matches a monomer with its corresponding polymer? (1.4)

a. amino acid - dna
b. monosaccharide - lipid
c. nucleotide - protein
d. amino acid - polypeptide

1. which of the following statements correctly describes a difference between dna and rna? (1.6)

a. dna contains the sugar ribose, while rna contains the sugar deoxyribose.
b. dna is typically single - stranded, whereas rna is typically double - stranded.
c. dna uses the nitrogenous base thymine, while rna uses the nitrogenous base uracil.
d. dna is found only in the cytoplasm, while rna is found only in the nucleus.

1. orb - weaver spiders produce silk that is incredibly strong and flexible, primarily due to structural proteins in the web called fibroins. these fibroins contain high amounts of glycine and alanine, which facilitate the formation of beta pleated sheets. these sheets are stabilized by extensive hydrogen bonding, contributing to the silks tensile strength and elasticity. however, the production and properties of spider silk can be influenced by various environmental factors. exposure to environmental pollutants, such as pesticides and heavy metals, can disrupt the silk production process. these chemicals can cause genetic mutations in the spiders, altering the amino acid sequence of fibroin proteins. as a result, the mechanical properties of the silk, such as tensile strength and elasticity, can be compromised, leading to less effective webs. which option best explains how exposure to pesticides most likely alters the web - building properties of orb - weaver spiders and the underlying mechanism at the protein level? (1.4, 1.5)

a. pesticides inhibit the synthesis of alanine in spiders, preventing the formation of alpha helices in fibroin proteins. this change in secondary structure results in silk that loses flexibility but maintains its tensile strength.
b. pesticides cause mutations in the spiders dna that alter the sequence of fibroin proteins, leading to a decrease in the glycine content. this reduces the formation of beta pleated sheets, weakening the silk and reducing its tensile strength.
c. pesticides disrupt the spiders nervous system, leading to impaired coordination and resulting in improperly built webs. however, the protein structure of fibroins remains unchanged, so the silk retains its tensile strength.
d. pesticides lead to an increase in the production of proline in fibroin proteins, which disrupts hydrogen bonding in beta pleated sheets. this results in silk that is less elastic but still retains its tensile strength.

Explanation:

• Question 21: Carbon can form up to four covalent bonds, enabling the creation of diverse and complex molecular structures, which is crucial for macromolecule formation.
• Question 22: Water has a high specific - heat capacity, allowing it to absorb a large amount of heat with only a slight temperature increase compared to sand.
• Question 23: Amino acids are the monomers of polypeptides.
• Question 24: DNA uses the nitrogenous base thymine, while RNA uses uracil.
• Question 25: Pesticides can cause mutations in the spiders' DNA, altering the amino - acid sequence of fibroin proteins and disrupting the formation of beta - pleated sheets, weakening the silk strength.

Answer:

1. d. Carbon can form up to four covalent bonds, allowing for the construction of diverse and complex molecular structures.
2. a. Water has a high specific heat, allowing it to absorb a large amount of heat with only a slight change in temperature.
3. d. Amino acid - Polypeptide
4. c. DNA uses the nitrogenous base thymine, while RNA uses the nitrogenous base uracil.
5. a. Pesticides inhibit the synthesis of alanine in spiders, preventing the formation of alpha helices in fibroin proteins. This change in secondary structure results in silk that loses flexibility but maintains its tensile strength.