Amino Acids

Amino Acids

•  Structure 
  • carbon attached to carboxyl group + amino group + “R” group
    • “R” group gives each of the 20 amino acids its unique properties
    • only L-form amino acids (AA) are found in proteins
• Properties
  • hydrophobicity
    • allow for protein folding such that hydrophilic AAs face externally and hydrophobic AAs face internally
    • hydrophobic AAs have aliphatic or aromatic R-groups
    • hydrophilic AAs have oxygen or nitrogens in R-group
  • pH
    • acidic AAs are negatively charged at body pH
      • Asp, Glu
    • basic AAs are positively charged at body pH
      • Arg, His, Lys
  • essential/non-essential
    • essential AAs must be part of the diet
      • remember: PVT TIM HALL (Phe/Val/Thr/Trp/Ile/Met/His/Arg*/Lys/Leu)
        • *is essential under times of stress/demand
          • pregnancy
          • growth during childhood and adolescence
          • illness
  • catabolic product
    • glucogenic AAs can become glucose
      • Met, Val, Arg, His
    • ketogenic AAs can become ketone bodies 
      • Leu, Lys
    • some AAs can become both ketone bodies or glucose
• Ile, Phe, Thr, Trp

Amino Acid Derivatives

• Tyrosine
  • thyroid hormones (T₃/T₄)
  • melanin
    • deficiency
      • albinism 
        • cause
          • defective tyrosinase
            • inability to synthesize melanin from tyrosine
          • defective tyrosine transporters
            • ↓ amounts of tyrosine and thus melanin
          • lack of migration of neural crest cells forming melanocytes
        • presentation
          • lack of melanin ↑ risk of skin cancer
        • genetics
          • AR
          • locus heterogeneity can result in variable inheritance
          • XR for ocular albinism
  • catecholamines
    • pathway see above
• Tryptophan
  • NAD, NADP (niacin)
  • serotonin
• Histidine
  • histamine
• Arginine
  • nitric oxide (NO)
• Glutamate
  • GABA
• Glycine
  • protoprophyrin → heme

Introduction

Amino acids are organic compounds that serve as the building blocks of proteins. They are essential for the growth, development, and maintenance of all living organisms. There are 20 different amino acids that can be found in proteins, each with a unique chemical structure and specific properties.

All amino acids share a common chemical structure consisting of an amino group (-NH2), a carboxyl group (-COOH), and a side chain that is specific to each amino acid. The side chain, also known as the R group, gives each amino acid its unique properties, such as hydrophobicity, hydrophilicity, acidity, or basicity.

Essential and Non-essential Amino acids

There are 20 different amino acids that can be found in proteins, and they can be classified into two categories: essential and non-essential.

Essential amino acids cannot be synthesized by the body and must be obtained from the diet. There are nine essential amino acids:

1. Histidine
2. Isoleucine
3. Leucine
4. Lysine
5. Methionine
6. Phenylalanine
7. Threonine
8. Tryptophan
9. Valine

Non-essential amino acids, on the other hand, can be synthesized by the body from other amino acid or metabolic intermediates.

1. Alanine
2. Arginine
3. Asparagine
4. Aspartic acid
5. Cysteine
6. Glutamic acid
7. Glutamine
8. Glycine
9. Proline
10. Serine
11. Tyrosine

Functions

1. Protein synthesis: Amino acids are the building blocks of proteins. They are linked together by peptide bonds to form long chains, which fold into complex structures to perform specific functions.
2. Hormone production: Some amino acids are used to synthesize hormones, such as adrenaline, thyroid hormones, and insulin.
3. Immune function: Amino acids are used to produce antibodies, which are critical components of the immune system that help to identify and neutralize foreign invaders.
4. Energy production: Amino acids can be broken down into glucose or other metabolites to provide energy for the body.
5. Neurotransmitter synthesis: Some amino acid, such as glutamate and GABA, are used to synthesize neurotransmitters, which are chemical messengers that transmit signals between neurons in the brain and nervous system.
6. Transport and storage of molecules: Amino acid can be used to transport molecules, such as oxygen and carbon dioxide, in the blood. They can also be stored in the body for later use.
7. pH regulation: Amino acid can act as buffers, helping to maintain the pH balance of bodily fluids.
8. Wound healing and tissue repair: Amino acids are involved in the process of wound healing and tissue repair, helping to rebuild damaged tissues and cells.

Deficiency

Deficiency of essential amino acids can lead to a variety of health problems, including impaired growth and development, muscle wasting, weakness, fatigue, and impaired immune function. If the body is deficient in one or more essential amino acid, it may not be able to synthesize all of the proteins it needs to function properly.

Protein malnutrition, which is a lack of dietary protein, is a common cause of amino acid deficiency. It can result from inadequate intake of protein-rich foods, such as meat, fish, eggs, dairy, and beans, or from conditions that impair protein digestion or absorption, such as chronic pancreatitis or inflammatory bowel disease.

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