Lecture 10 - Introduction to Protein Metabolism Flashcards
the breakdown of protein into amino acids provides:
key metabolic intermediates
Defects in protein metabolism results in:
defects in protein metabolism results in a variety of human diseases
3 main purposes of metabolism:
(1) The performance of mechanical work in muscle contraction and cellular movements
(2) The active transport of molecules and ions (such as neurones)
(3) The synthesis of macromolecules and other biomolecules from simple precursors
amino acids are:
(1) key metabolic intermediates
(2) broken down into their amino group and carbon skeleton feeds into fundamental metabolic processes [toxic amino/ammonia by-products are removed by the Urea cycle]
(3) precursors for hormones and neurotransmitter
Liver, muscles and kidneys regulate protein metabolism:
1.Proteins ingested and absorbed via intestinal lumen are moved via the hepatic portal vein to the liver
2.There is trafficking of amino acids and metabolic intermediates between the muscle, liver, and kidney
3.Muscle cells use glucose for energy but during metabolic starvation or intense exercise they use branched chain amino acids (BCAA) as an energy source
4.The liver is fundamental in protein metabolism and amino acid recycling
5.Liver cells have the role in removal of ammonia, a toxic by-product of amino acid breakdown, from the body through the urea cycle
what are essential & non-essential amino acids?
•Essential amino acids are those that the human body cannot synthesise on its own
•Must be acquired through diet or supplements
•Some adults may be able to synthesise Histidine
•Non-essential amino acids can be synthesised by our body
•Synthesised using aminotransferases (transaminases)
Alanine plays a vital role in:
the glucose-alanine cycle - alanine is converted into the crucial intermediate pyruvate through the activity of Alanine Aminotransferase
two acidic amino acids ________ & _______ play a crucial role in metabolism:
glutamate & aspartate
•carry a negative charge in their R group at certain pH
•are often crucial in the active site of enzymes as they interact with metal ions (i.e., Mg2+)
•are vital metabolic intermediates and participate in the TCA cycle and nitrogen removal
Glutamate is the most:
abundant excitatory neurotransmitter in the body
Basic amino acids are also important metabolic intermediates:
•Basic amino acids carry a positive charge in their R group at certain pH
•Are crucial sites of covalent linkage through the Epsilon amino group
•Such as ubiquitin which is important during protein degradation
•Are important intermediates for the Urea Cycle
•Crucial for the removal of the toxic by-products of amino acid catabolism
Branched chain amino acids:
•Contain a branched chain R group
•Can be used as a temporary substitute for fatty acids as a fuel for oxidation in muscles during short term starvation
•These metabolic events require the glucose-alanine cycle to remove the nitrogen from the amino groups
•Can buy BCAA’s as an exercise supplement proposed to prevent lactic acid build up
are very hydrophobic and important for protein structure
ketogenic amino acids can be:
metabolised into ketone bodies via acetyl co-enzyme A
glucogenic amino acids can be:
metabolised into glucose via pyruvate and oxaloacetate
major purine bases:
adenine and guanine
major pyrimidine bases:
cytosine, thymine and uracil
