Biochemistry is a difficult subject where even the postgraduate students find it difficult to correlate the biochemical changes that occur in human body in the state of health and disease. This book aims to present selected crucial concepts of biochemistry in a lucid, mathematical and compact way with suitable illustrations. The topics have been chosen keeping in mind the need of a medical student to understand biochemistry at clinical level. The aim is to help students digest and assimilate the actual biochemical phenomena as they occur in human body in health and disease, rather than remembering cycles and facts from textbooks. A brilliant mind is that which seeks answers to the unknown. The book, written in question and answer format, is in no way meant to be a substitute for regular textbooks on the subject but is only meant to be a companion to the students who want to critically understand and revise the matter to be able to apply a similar approach to learning whole biochemistry and answer with confidence and reasoning the difficult questions based on biochemistry asked in various PG entrance examinations.