1. Unit Thirteen: Metabolism and Temperature Regulation
Chapter 69: Protein Metabolism
Guyton and Hall, Textbook of Medical Physiology, 12th edition

2. Basic Properties
Amino Acids- peptide linkages and peptide chains

3. Fig Amino acids

4. Protein Metabolism
Other Linkages-hydrogen bonding

5. Protein Metabolism
Transport and Storage of Amino Acids
Blood amino acids- account for only 2-3 mEq of
negative ions in the blood
When absorbed from the GI tract, most are
absorbed by the liver
Carried into cells by active transport; stored as
proteins once inside the cell

6. Protein Metabolism
Functional Roles of Plasma Proteins
Major types are albumin, globulin, and fibrinogen
Albumin-provides colloid osmotic pressure
Globulins-enzymatic functions and immunity
Fibrinogen-converted into fibrin to form blood
clots

7. Protein Metabolism
Formation of Plasma Proteins
All of the albumin, fibrinogen, and 50-80% of
the globulins are formed in the liver
Formation by the liver can be as much as 30 g/day
Plasma Proteins are a Source of Amino Acids for
Tissues

8. Protein Metabolism
Fig Reversible equilibrium among the tissue proteins, plasma proteins, and plasma amino acids

9. Protein Metabolism
Essential and Nonessential Amino Acids
Group of amino acids that cannot be synthesized
by the body but must be supplied in the diet
Nonessential aa can be synthesized; mostly from
alpha-keto acids such as pyruvic acid (process of
transamination)

10. Essential and Nonessential Amino Acids
Protein Metabolism
Essential and Nonessential Amino Acids
Fig Synthesis of alanine from pyruvic acid by transamination

11. Protein Metabolism
Use of Proteins for Energy- once cells are filled to
their limit with proteins, any additional aa
are degraded and used for energy or stored as
fat or glycogen
Degradation occurs in the liver and begins with
the process of deamination
b. Begins with the removal of the amine group

12. Protein Metabolism
Transamnation schema for the deamination
of amino acids

13. Protein Metabolism
Hormonal Regulation
Growth hormone increases the synthesis of cellular
proteins
Insulin is necessary for protein synthesis
Glucocorticoids increase the breakdown of most
tissue proteins
Testosterone increases protein deposition in tissues
Estrogen causes some deposition of protein in
tissues, but minor compared to testosterone
Thyroxine increases the rate of metabolism and
indirectly affects protein metabolism