Creatine and Creatinine

Creatine is present in muscle, brain and blood. It is particularly important in its phosphorylated form as an immediate store of high-energy phosphoryl bonds for the generation of ATP from ADP. The chemical energy for the first few seconds of muscle contraction are supplied by ATP generated from this source.

EXAMPLES OF DEFECTS IN AMINO ACID METABOLISM

Condition

Biochemical defect

Clinical features

Phenylketonuria

X conversion of phenylalanine to tyrosine

1 in 10 000 births mental retardation

Homocystinuria

X levels of cysteine and cystine levels of homocystine and methionine

Tall, thin body, subluxation of lens mental retardation

Alkaptonuria

levels of homogentisic acid

Ochronosis (pigmented connective tissues), arthritis

Figure MT.15

Figure MT.15

Phosphorus Cycle

Figure MT.16 Urea cycle

Creatine is phosphorylated by creatine kinase. The serum levels of this enzyme are used as a marker of muscle damage following trauma or myocardial infarction. Creatine kinase activity may also be raised however simply as a result of violent exercise.

Creatinine is the anhydride of creatine and is formed as a metabolite for excretion in the urine. The 24 H urinary excretion of creatinine is relatively constant for any given individual, while renal tubular re-absorption is small. This means that the value for creatinine clearance can be used as an approximation to glomerular filtration rate.

Purines and Pyrimidines

These substances are ring-based structures that occur widely throughout the body. They form the base components in the ribonucleotides and deoxyribonucleotides, i.e. the 'alphabet' triplets that code RNA and DNA strands. Purines and pyrimidines occur throughout the tissues as carriers of high-energy phosphoryl bonds, e.g. adenosine triphosphate (ATP), guanosine triphosphate (GTP) and uridine triphosphate (UTP). These molecules are also ubiquitous as the functional parts of many co-factors.

Was this article helpful?

0 0
Osteoarthritis

Osteoarthritis

Thank you for deciding to learn more about the disorder, Osteoarthritis. Inside these pages, you will learn what it is, who is most at risk for developing it, what causes it, and some treatment plans to help those that do have it feel better. While there is no definitive “cure” for Osteoarthritis, there are ways in which individuals can improve their quality of life and change the discomfort level to one that can be tolerated on a daily basis.

Get My Free Ebook


Post a comment