Chapter 6Chapter 6Chapter 6Chapter 6
Proteins and Amino AcidsProteins and Amino Acids
General Amino Acid Structure
HN C C
H O
OH
H
Aminogroup
Acidgroup
Side Group Varies
Examples of amino acids
HN C C
H
O
OH
C
H
O OH
HH
HN C C
H
O
OH
CH3
HHN C C
H
O
OH
H
H
HN C C
H
O
OH
C
H
HH
HN C C
H
O
OH
C
H
HH
SH
HN C C
H
O
OH
C
H
CH3
OHH
Glycine Alanine
AsparticAcid
Phenylalanine Cysteine Threonine
Condensation of two amino acids:
Formation of a dipeptide
HN C C
H
O
OH
CH3
H HN C C
H
O
OH
C
H
HH
HN C C
H
O
CH3
H H
N C C
O
OH
C
H
HH
Alanine Phenylalanine
+
+ H2O
PeptideBond
Formation of a Polypeptide
11 H2O
AA1 AA2 AA4 AA7AA6AA3 AA5 AA8 AA10AA9 AA11 AA12++++++ +++++
AA1---AA2---AA3---AA4---AA5---AA6---AA7---AA8---AA9---AA10---AA11---AA12
Folding andShape of Proteins
Essential versus Non-essential Amino Acid
Humans need ALL 20 amino acids to be able to make proteins.
Glycine Alanine SerineCysteine Proline TyrosineAspartic Acid Asparagine Glutamic AcidGlutamine Arginine
Valine Leucine IsoleucineThreonine Methionine PhenylalanineTryptophan Lysine Histidine
Essential Amino Acids
Conditionally Essential Amino Acids
HN C C
H
O
OH
C
H
HH
HN C C
H
O
OH
C
H
HH
OH
Phenylalanine Tyrosine
Human enzymephenylalanine hydroxylase
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
CellDNAmRNA
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
Growing protein strand
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
Normalversus
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
8.0
7.45
7.35
6.8 Death
Death
Acidosis
Alkalosis
Normal
7) Antibodies (Immune system)
8) Energy: - break down protein to use
the energy.
Proteins per ServingIn Food Groups
Gra
ms
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.
IleIle LysLys MetMet TrpTrp
LegumeLegume YESYES YESYES NONO NONO
GrainsGrains NONO NONO YESYES YESYES
TogetherTogether YESYES YESYES YESYES YESYES
© 2002 Wadsworth Publishing / Thomson Learning™
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
•6 - 18 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