Question

which of the following statements about the amino acids that are required by adult humans is true?
the human body produces 20 amino acids.
there are eight amino acids used as building blocks for human proteins.
amino acids are the building blocks of carbohydrates.
amino acids are the building blocks of proteins.
question 40
1 pts
which of the following is true for the figure shown?
image of a muscle - related figure
click to view larger image.
it represents an entire myofibril.
it represents a single muscle fiber.
it represents a muscle in a contracted position.
it represents a muscle in a relaxed position.

Explanation:

First Question (Amino Acids):

• Analyze each option:
• "The human body produces 20 amino acids": Humans produce some, but 20 are involved in protein synthesis (some essential, some non - essential), so this is incorrect.
• "There are eight amino acids used as building blocks for human proteins": Adults have 9 essential amino acids (must be obtained from diet), and all 20 (essential + non - essential) are building blocks of proteins, so this is incorrect.
• "Amino acids are the building blocks of carbohydrates": Carbohydrates' building blocks are monosaccharides (like glucose), so this is incorrect.
• "Amino acids are the building blocks of proteins": By definition, proteins are polymers made of amino acid monomers, so this is correct.

• Analyze each option:
• "It represents an entire myofibril": A myofibril has many sarcomeres, and the figure is a single sarcomere or a representation of muscle contraction/relaxation, not an entire myofibril, so incorrect.
• "It represents a single muscle fiber": A muscle fiber is a cell with many myofibrils, the figure is about muscle contraction state, not a muscle fiber, so incorrect.
• "It represents a muscle in a contracted position": In a contracted muscle, the sarcomere shortens (actin and myosin overlap more). The figure shows a state where the muscle is contracted (compared to relaxed where sarcomeres are longer), so this is correct.
• "It represents a muscle in a relaxed position": In relaxed state, sarcomeres are longer with less overlap, which does not match the figure, so incorrect.

Answer:

Amino acids are the building blocks of proteins.

Second Question (Muscle Figure):