Amino Acids Lecture 1 PDF

# Amino Acids ## Dr. Adham Maher ### Page 1: - Amino acids are organic compounds composed of **C, H, O, N**. - They are the building blocks of proteins. - **L-type** amino acids have the amino (H2N-) group on the left. - There are 22 common amino acids that differ in their **side chain** and make...

# Amino Acids ## Dr. Adham Maher ### Page 1: - Amino acids are organic compounds composed of **C, H, O, N**. - They are the building blocks of proteins. - **L-type** amino acids have the amino (H2N-) group on the left. - There are 22 common amino acids that differ in their **side chain** and make up all proteins. ### Page 2: - The below diagram depicts the difference between D- and L- amino acids. | Amino acid | Structure | |---|---| | L-amino acid | H<br>H2NC - COOH<br>R | | D-amino acid | COOH<br>H<br>C - NH2<br>R | ### Page 3: ## Classification of amino acids ### 1. According to polarity and structure #### Non-polar amino acids - **Glycine (Gly)** [G] - **Alanine (Ala)** [A] - **Valine (Val)** [V] - **Leucine (Leu)** [L] - **Isoleucine (Ile)** [I] - **Methionine (Met)** [M] - **Proline (Pro)** [P] - **Phenylalanine (Phe)** [F] - **Tryptophan (Trp)** [W] ### Page 4: #### Polar uncharged amino acids - **Serine (Ser)** [S] - **Threonine (Thr)** [T] - **Cysteine (Cys)** [C] - **Tyrosine (Tyr)** [Y] - **Asparagine (Asn)** [N] - **Glutamine (Gln)** [Q] #### Polar negatively charged (acidic) amino acids - **Aspartic acid (Asp)** [D] - **Glutamic acid (Glu)** [E] ### Page 5: #### Polar positively charged (basic amino acids) - **Lysine (Lys)** [K] - **Arginine (Arg)** [R] - **Histidine (His)** [H] #### Newly discovered amino acids (incorporated in proteins by a unique mechanism) - **Selenocysteine (Sec)** [U] - **Pyrolysine (Pyl)** [O] ### Page 6: ## II. According to the nutritional value (biological value) ### A. Essential amino acid: - Cannot be synthesized by the human body. - Must be taken in the diet. - They are: **Valine, Leucine, Isoleucine, Methionine, Phenylalanine, Tryptophan, Lysine, and Threonine**. - Proteins may be: - **High biological value**: contain all the essential amino acids (e.g., milk and egg proteins) - **Low biological value**: are deficient in one or more of the essential amino acids (e.g., Collagen) ### B. Semi-essential amino acids: - **Arginine and Histidine** - Arginine is found in the body at a rate enough for adults but not for growing individuals. ### C. Non-essential amino acids: - Can be synthesized in the body from: - Each other (interconversion) - Intermediary metabolites ### Page 7: ## III. Classification of amino acids according to metabolic fates ### 1. Purely ketogenic a.a: - Amino acids giving rise to ketone bodies and fat during their catabolic pathways (e.g., Leu). ### 2. Purely glucogenic a.a: - Amino acids giving rise to carbohydrates (enter glucogenic pathway) during their catabolic pathways: - Gly, Ser, Ala, Thr, Asp, Asn, Glu, Gln, Pro, Met, Cys, Arg, Val and His. ### 3. Ketogenic and glucogenic (mixed) amino acids - During metabolism, part of the carbon skeleton of these amino acids will enter the fatty acid metabolic pathway and the other part into the glucose pathway: - Ile, Lys, Trp, Phe, and Tyr.