Proteins and Amino Acids

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Chapter 6

• Proteins and Amino Acids

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General Amino Acid Structure
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Examples of amino acids
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Condensation of two amino acids Formation of a
dipeptide
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Formation of a Polypeptide
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Essential versus Non-essential Amino Acid
Humans need ALL 20 amino acids to be able to make
proteins. Glycine Alanine Serine Cysteine
Proline Tyrosine Aspartic
Acid Asparagine Glutamic Acid Glutamine Arginine
Valine Leucine Isoleucine Threonine Methioni
ne Phenylalanine Tryptophan Lysine Histidine Es
sential Amino Acids
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Conditionally Essential Amino Acids
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Protein digestion in the GI Tract
Mouth - moisten and mechanical
crushing Stomach - HCl denatures proteins
- HCl also converts pepsinogen into pepsin
- pepsin acts to cleave large polypeptides into
smaller polypeptides
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Protein digestion in the GI Tract
Small Intestine - Trypsin and chymotrypsin
breakdown polypeptides into smaller and smaller
peptides. - Carboxypeptidases and
aminopeptidases chew along from the ends to
liberate amino acids. - Di- and tripeptidases
break down dipeptides and tripeptides to amino
acids. - Free amino acids are absorbed into
the blood system.
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Protein synthesis Transcription Making
messenger RNA
Cell
DNA
mRNA
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Protein synthesis Translation Ribosomes
translate the CODE of the message utilizing
transfer RNAs which carry individual amino acids
Ribosome
mRNA
Amino Acid
Transfer RNA
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Protein synthesis

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Protein Function Within Our Body
1) Building materials (e.g. collagen,
elastin, keratin, myocin, actin)
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2) Enzymes (e.g. lipase, amylase, pepsin)
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3) Hormones (e.g. insulin, glucagon, CCK)
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4) Regulators Fluid balance
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5) Transport i.e. hemoglobin, ferritin
Iron atom
Heme
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Normal versus Sickle Cells
6th residue
Normal Hemoglobin Val-His-Leu-Thr-Pro
-Glu-Glu- Sickle Cell Hemoglobin
Val-His-Leu-Thr-Pro-Val-Glu-
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A Membrane-bound transport protein Sodium -
Potassium Pump
INSIDE CELL
OUTSIDE CELL
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6) Acid-Base Regulators
Death
8.0
Alkalosis
7.45
Normal
7.35
Acidosis
6.8
Death
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7) Antibodies (Immune system) 8) Energy -
break down protein to use the energy.
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Proteins per Serving In Food Groups
Grams
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Quality of Proteins

• A COMPLETE protein contains essential amino
  acids is relatively the same amounts as humans
  need.
• (e.g. meat, fish, poultry, eggs, milk)
• However, all proteins do not have the same
  proportion of each amino acid.

Ile Lys Met Trp
Legume YES YES NO NO
Grains NO NO YES YES
Together YES YES YES YES
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PEM (Protein-Energy Malnutrition)

• affects 1 out of 4 children in the world.
• accomplice in 50 of the 10.9 million child
  deaths each year.
• 70 in Asia, 26 in Africa 4 in Latin America

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PEM (Marasmus)

• chronic PEM
• 6 - 18 months
• inadequate intake of energy and protein.

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PEM (Kwashiorkor)

• acute PEM
• sets in at 18 months - 2 years of age
• inadequate intake of protein due to a change
  from breast milk to protein poor cereals.

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Protein and Amino Acid Supplements

• what is the RDA for protein?
• what happens when more high protein higher
  amounts of proteins are consumed?
• do athletes need to supplement their diet with
  higher amounts of protein or amino acid?

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Types of Vegetarianism
Omnivores - people that eat ALL foods
including meat. Lactoovovegetarians - exclude
meat, poultry, fish, and seafood. Lactovegetarian
s - also exclude eggs Vegan - exclude ALL animal
derived foods
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Vegetarians obtain their protein from whole
grains, legumes, nuts, vegetables, and, in some
cases, eggs and milk products
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Food Pyramids Compared