Chapter 6 Proteins and Amino Acids

General Amino Acid Structure

Examples of amino acids

Condensation of two amino acids: Formation of a dipeptide

Formation of a Polypeptide

Folding and Shape of Proteins

Essential versus Non-essential Amino Acid Humans need ALL 20 amino acids to be able to make proteins. GlycineAlanineSerine Cysteine Proline Tyrosine Aspartic AcidAsparagineGlutamic Acid GlutamineArginine ValineLeucineIsoleucine ThreonineMethionine Phenylalanine TryptophanLysineHistidine Essential Amino Acids

Conditionally Essential Amino Acids

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

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.

Protein synthesis: Transcription Making messenger RNA Cell DNA mRNA

Protein synthesis: Translation Ribosomes “translate” the CODE of the message utilizing transfer RNAs which carry individual amino acids Transfer RNA Amino Acid Ribosome mRNA

Protein synthesis

Protein Function Within Our Body 1) Building materials (e.g. collagen, elastin, keratin, myocin, actin)

2) Enzymes (e.g. lipase, amylase, pepsin)

3) Hormones (e.g. insulin, glucagon, CCK)

4) Regulators Fluid balance

5) Transport: i.e. hemoglobin, ferritin Iron atom Heme

Normal versus Sickle Cells Normal Hemoglobin Val-His-Leu-Thr-Pro-Glu-Glu- Sickle Cell Hemoglobin Val-His-Leu-Thr-Pro-Val-Glu- 6th residue

A Membrane-bound transport protein “Sodium - Potassium Pump” OUTSIDE CELL INSIDE CELL

6) Acid-Base Regulators Death Acidosis Alkalosis Normal

7) Antibodies (Immune system) 8) Energy: - break down protein to use the energy.

Proteins per Serving In Food Groups Grams

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. IleLysMetTrp LegumeYESYESNONO GrainsNONOYESYES TogetherYESYESYESYES

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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

PEM (Marasmus) chronic PEM months inadequate intake of energy and protein.

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.

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?

Types of Vegetarianism Omnivores - people that eat ALL foods including meat. Lactoovovegetarians - exclude meat, poultry, fish, and seafood. Lactovegetarians - also exclude eggs Vegan - exclude ALL animal derived foods

Vegetarians obtain their protein from whole grains, legumes, nuts, vegetables, and, in some cases, eggs and milk products

Food Pyramids Compared