30 AAs - Amino Acid Metabolism

30 AAs - Amino Acid Metabolism - Amino Acids and Proteins...

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Unformatted text preview: Amino Acids and Proteins: Metabolism: Utilization of Amino Acids HNFE 3025 Fall 2009 • Ensures that a balanced and appropriate mixture of AAs is present in blood and available for other cells • Principle site of excess AA degradation – Forms urea for the disposal of ammonium ions – Utilizes carbon skeletons of AAs for GNG • Synthesize liver specific proteins • Synthesize plasma proteins • Produce a variety of non-protein N-containing compounds Roles of the Liver in AA and Protein Metabolism 2 • Hundreds of proteins are found in blood – Most synthesized in, secreted from, and degraded by the liver – Albumin – Transthyretin (prealbumin) – Retinol-binding protein – Blood clotting proteins – Immunoproteins – Transport proteins – Acute phase proteins – Stress (heat) shock proteins (hsp) • Some plasma proteins are used in assessing protein status – Based on the assumption that decreases in plasma proteins are due to a decrease in the liver’s production Plasma Proteins 3 • Most abundant plasma protein 4.6 g/dl (~50% of total plasma protein mass) • Relatively small mass (66.3 kDa), so also found in extracellular fluids, including cerebrospinal fluid (at concentrations < plasma concentration) • Maintains colloidal osmotic pressure in both vascular and extra-vascular spaces • Transports nutrients (eg. FFA, some minerals) and drugs • Has a relatively long half life (t ½ = 15 -19 d) – Concentration does not change rapidly (except for acute dehydration) – Slower changes (decreases) seen with inflammation, liver disease, kidney disease and malnutrition Albumin 4 Osmosis and Osmotic Pressure 5 Levels on each side before adding solute to one side Semi-permeable membrane. Allows only water to pass through. Osmosis and Osmotic Pressure 6 Level before adding solute to other side Level after adding solute to other side. Loss of water on this side. Semi-permeable membrane. Allows only water to pass through. New level on this side, after solute added. Old level, before any solute added to this side. Represents dissolved solute molecules/ions h is the height of fluid on left side above that on right side. Demonstrates osmotic pressure. • Transferrin – Principal plasma transport for iron (Fe 3+ ) in the blood – responsible for TIBC – Can also transport Cu in blood – t ½ = 8 - 9d • Transthyretin – TTR (formerly known as prealbumin) – Travels in blood in 1:1 complex with retinol binding protein....
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30 AAs - Amino Acid Metabolism - Amino Acids and Proteins...

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