Questions: What cellular macromolecules make up the complement pathway? Lipids Nucleic acids Proteins Carbohydrates Based on the animation, which of the following is cleaved by C1? C5 C2 C4

Part A

The answer is: Proteins

Explanation:

• The complement pathway is a part of the immune system that enhances the ability to clear microbes and damaged cells. It involves a series of proteins that work together to opsonize pathogens and trigger an inflammatory response. Therefore, proteins are the cellular macromolecules that make up the complement pathway.

• Lipids, nucleic acids, and carbohydrates are not the primary components of the complement pathway. Lipids are involved in cell membrane structure, nucleic acids are involved in genetic information storage and transfer, and carbohydrates are involved in energy storage and cell recognition.

Part B

The answer is: C4

Explanation:

• In the classical complement pathway, the C1 complex is responsible for the initial activation step. C1 binds to antibodies that are attached to a pathogen, and this binding leads to the cleavage of C4 into C4a and C4b. C4b then binds to the pathogen surface and participates in the formation of the C3 convertase.

• C5 is cleaved later in the complement cascade, not by C1. C2 is also involved in the complement pathway but is cleaved after C4. Therefore, C4 is the correct answer as it is directly cleaved by C1.