2. Chapter 5 Protien
Azhar Bin Mustafa@erican
• Proteins are the major structural parts of the body’s cells and are
made of nitrogen-containing amino acids joined end to end by
peptide bonds. Proteins often contain from 35 to several hundred or
more amino acids.
• There are 20 different amino acids, each with a different side group.
• Essential amino acids cannot be made in the body or cannot be
made in the quantities needed. Nonessential amino acids can be
made in the body. Sometimes a nonessential amino acid becomes
essential, and it is then called a conditionally essential amino acid.
• Protein fragments with 10 or more amino acids are called
polypeptides
Structure of Protien
4. Chapter 5 Protein
Azhar Bin Mustafa@erican
• Proteins function as part of the body’s structure, as in your skin,
bones, hair, muscles, blood, blood vessels, and digestive tract.
• Proteins are used for building and maintaining body tissues. Worn-
out cells are replaced at regular intervals.
• The greatest amount of protein is needed when the body is building
new tissues rapidly, such as during pregnancy or infancy.
• Some hormones are made of proteins. Hormones are chemical
messengers secreted into the bloodstream by various organs to
travel to a target organ and influence what it does
• Proteins also act as taxicabs in the body, transporting iron and
other minerals, some vitamins, fats, and oxygen through the blood.
Function of Protein
5. Chapter 5 Protein
Azhar Bin Mustafa@erican
• Protein plays a role in body fluid balance and the acid-base
balance of the blood.
• Amino acids can be burned to supply energy if that is
absolutely necessary.
• Protein fibers known as fibrin help form a clot so that
bleeding stops.
Function of Protein
6. Chapter 5 Protein
Azhar Bin Mustafa@erican
• Protein digestion takes place in the stomach and small
intestine.
• The hydrochloric acid in the stomach converts pepsinogen to
the enzyme pepsin, which splits peptide bonds in proteins.
• Next, in the small intestine, proteases split up proteins into
short peptide chains and amino acids.
• The brush border of the small intestine produces several
peptidases, enzymes that break down short peptide chains
into amino acids, dipeptides, and tripeptides.
Digestion, Absorption, & Metabolism
7. Chapter 5 Protein
Azhar Bin Mustafa@erican
• When tripeptides and dipeptides enter the intestinal cells,
they are split into amino acids. Because amino acids are
water-soluble, they travel easily in the blood to the liver and
then to the cells that need them.
• An amino acid pool in the body provides the cells with a
supply of amino acids for making protein. If the body is
making a protein and can’t find an essential amino acid for it,
the protein can’t be completed, and the partially completed
protein is taken apart.
Digestion, Absorption, & Metabolism
8. Chapter 5 Protein
Azhar Bin Mustafa@erican
• Animal proteins are examples of complete proteins, and
most plant proteins are examples of incomplete proteins.
• By eating complementary plant proteins, such as legumes
with grains, you can overcome the problem presented by
limiting amino acids and eat a nutritionally adequate diet.
• In the right amounts and combinations, plant proteins can
support growth and maintenance.
PROTEIN IN FOOD
9. Chapter 5 Protein
Azhar Bin Mustafa@erican
• Eating too much protein has no benefits. It will not result in
bigger muscles, stronger bones, or increased immunity.
• Diets high in protein can also be a concern if you are eating
a lot of high-fat animal proteins such as hamburgers and
cheese and few vegetable proteins. Eating too many high-fat
animal foods, which contain much saturated fat, raises your
blood cholesterol levels. Higher blood cholesterol levels
increase your risk of heart disease. Eating too many high-fat
foods also increases the chances of eating too many
kcalories and gaining weight.
PROTEIN IN FOOD
10. Chapter 5 Protein
Azhar Bin Mustafa@erican
• High intakes of animal proteins are also associated with
certain cancers, such as cancer of the colon.
• High protein intakes lead to increased calcium losses.
PROTEIN IN FOOD
