Name one enzymatic step of the tca cycle wherein a universal electron carrier (in its reduced form) is a product of the reaction:

Oxidation of Malate to Oxaloacetate by Malate Dehydogenase

Explanation:

An electron carrier is able to accept and donate electrons in a reaction. The most popular is NADH. NADH in its oxidized form is NAD+. NAD+ received two (2) electrons and an H+ to be reduced to NADH. Other electron carriers are NADPH & FADH₂

There are several steps in the TCA where NAD+ is reduced to NADH by accepting an electron. One of this step is the last step where malate is oxidized and is converted back to oxaloacetate the beginning  molecule of the cycle.

c. heat from the poles back down towards the equator.