Which of the following is a function of a protein macromolecule in animals?

Introduction / Context:
Biological macromolecules include carbohydrates, lipids, proteins, and nucleic acids. Each type has characteristic structures and functions. This question asks you to identify which listed function is carried out by proteins, rather than by lipids or nucleic acids, in animals.

Given Data / Assumptions:

• The options describe cushioning organs, providing genetic instructions, forming connective tissue, and making leaves waterproof.
• We assume typical roles of fats, DNA, proteins, and plant waxes.
• The question focuses specifically on protein macromolecules.

Concept / Approach:
Proteins are polymers of amino acids and can act as enzymes, structural components, transporters, and more. In connective tissues such as tendons and ligaments, the main structural component is collagen, a fibrous protein. Lipids stored in adipose tissue cushion organs and act as energy reserves. Nucleic acids, especially DNA, carry genetic instructions. Waxy cuticles on leaves are made of lipids, not proteins. The correct answer must therefore describe a primarily protein based function.

Step-by-Step Solution:
Step 1: Evaluate option A. Cushioning internal organs is a typical function of adipose tissue, which is rich in triglyceride lipids, not mainly proteins.Step 2: Evaluate option B. Providing genetic instructions is the role of nucleic acids, particularly DNA, not proteins.Step 3: Evaluate option C. Forming connective tissue in tendons and ligaments is largely the role of collagen and other structural proteins, which are protein macromolecules.Step 4: Evaluate option D. Making leaves waterproof is due to waxy lipid coatings called cutin and related substances, not proteins.Step 5: Conclude that option C correctly identifies a function of proteins.

Verification / Alternative check:
To verify, recall that proteins can be globular, like enzymes and antibodies, or fibrous, like keratin and collagen. Tendons and ligaments need strength and flexibility, which collagen fibers provide. This is a canonical example of a structural protein function described in many biology textbooks.

Why Other Options Are Wrong:
Option A is wrong because the cushioning and energy storage function is mainly carried out by lipids in fat tissue. Option B is wrong because genetic information storage is the job of DNA and RNA, not proteins. Option D is wrong because plant leaf waterproofing comes from a lipid based cuticle rather than protein.

Common Pitfalls:
Students sometimes associate any structural role with proteins and may overlook the important role of lipids in energy storage and waterproofing. Another pitfall is confusing proteins and nucleic acids because both are polymers but with different monomers and functions. Remembering clear examples such as collagen in tendons for proteins, DNA for genetic information, and fats for cushioning helps keep these roles distinct.

Final Answer:
Forms much of the connective tissue in tendons and ligaments.