Which of the following does not promote multiple steps in the clotting pathway?
a. Platelet phospholipids
b. Factor XI
c. Thrombin
d. Ca²⁺

Verified step by step guidance

Step 1: Understand the clotting pathway involves a cascade of reactions where each activated factor promotes the activation of the next, amplifying the response to form a clot.

Step 2: Identify the role of platelet phospholipids, which provide a surface that facilitates the assembly of clotting factor complexes, thus promoting multiple steps in the cascade.

Step 3: Recognize that Factor XI is an enzyme that activates Factor IX, contributing to the amplification and continuation of the clotting cascade.

Step 4: Know that thrombin is a key enzyme that not only converts fibrinogen to fibrin but also activates several upstream factors, thereby promoting multiple steps in the clotting pathway.

Step 5: Understand that Ca²⁺ (calcium ions) act as a cofactor required for several steps but do not themselves promote multiple steps; they are essential but do not amplify the cascade like enzymes or phospholipids do.

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above.

Video duration:

Was this helpful?

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Clotting Pathway and Cascade Mechanism

The clotting pathway involves a series of enzymatic reactions where inactive clotting factors are sequentially activated, amplifying the response to form a blood clot. This cascade ensures rapid and localized clot formation through multiple steps, involving intrinsic, extrinsic, and common pathways.

Role of Platelet Phospholipids in Clotting

Platelet phospholipids provide a negatively charged surface essential for assembling clotting factor complexes. This surface accelerates the activation of clotting factors, promoting multiple steps in the cascade and enhancing thrombin generation.

Function of Clotting Factors and Cofactors (Factor XI, Thrombin, Ca²⁺)

Factor XI is an enzyme that activates downstream factors, thrombin converts fibrinogen to fibrin and activates other factors, and Ca²⁺ acts as a cofactor facilitating binding of factors to phospholipid surfaces. All promote multiple steps in the clotting cascade except when a component does not directly participate in amplification.

Recommended video: