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Chapter 6
Proteins and Amino
Acids
Sources of Protein in the Diet
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Protein deficiency is rare in the United
States.
In the US, about two-thirds of dietary protein
comes from meat, poultry, seafood, eggs
and dairy products.
Most of the world relies on plant proteins
from grains and vegetables.
As a country’s economy improves, the
proportion of animal foods in the diet tends
to increase.
Copyright 2010, John Wiley & Sons, Inc.
Nutrients Supplied by Plant and
Animal Foods
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Animal products provide sources of protein,
B vitamins and minerals such as iron, zinc
and calcium.
However, animal products are low in fiber
and can be high in fat.
Plant sources of protein are also a good
source of B vitamins, iron, zinc, fiber and
calcium, but in less absorbable forms.
Copyright 2010, John Wiley & Sons, Inc.
Amino Acids
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Amino acids are the building blocks of
protein.
Each amino acid contains
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a central carbon atom bound to a hydrogen atom
an amino group
an acid group
a side chain.
Copyright 2010, John Wiley & Sons, Inc.
Copyright 2010, John Wiley & Sons, Inc.
Protein differs from carbohydrate
and lipid in that protein
a)
does not provide the body
with a source of energy.
b)
is classified as an
inorganic molecule.
c)
contains the element
nitrogen.
d)
is not considered to be an
essential nutrient.
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•Essential amino acids cannot be
synthesized by the human body in
sufficient amounts to meet needs.
•Essential amino acids must be
included in the diet.
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Amino Acids
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Amino Acids: Transamination
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When a nonessential amino acid is not
available from the diet, it can be made in the
body by the process of transamination.
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Protein Structure
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Peptide bonds are chemical bonds that link amino acids
together.
Peptide bonds are formed between the acid group of
one amino acid and the nitrogen group of the next
amino acid.
Dipeptide bonds are formed between two amino acids.
Polypeptides are formed between many amino acids.
A protein is made of one or more polypeptide chains
folded into a three-dimensional shape.
Copyright 2010, John Wiley & Sons, Inc.
Protein
Structure
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7. Which of the following terms can be used to describe a
protein?
a) polypeptide.
b) monopeptide.
c) polysaccharide.
d) glycogen.
Copyright 2010, John Wiley & Sons, Inc.
Protein Shape Determines Function
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The final shape of a protein determines its
function.
Connective tissue proteins and collagen are
elongated.
Hemoglobin has a spherical shape.
If the shape of a protein is altered, its
function may be disrupted.
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If Protein Shape is Altered,
Function May Be Altered
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If the shape of a protein is altered,
the ___________ of the protein is
altered.
a)
nutritional value
b)
functionality
c)
taste
d)
smell
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Protein
Digestion
and
Absorption
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The enzymes trypsin and chymotrypsin
break large polypeptides
into smaller peptides.
are needed to denature
proteins.
rearrange the sequence of
amino acids in a
polypeptide.
are needed to make
nonessential amino acids.
Copyright 2010, John Wiley & Sons, Inc.
Amino Acids
Copyright 2010, John Wiley & Sons, Inc.
Proteins that May Harm Certain
Individuals: Phenylketonuria
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PKU is an inherited condition attributed to a
defective gene.
Aspartame, a sugar substitute, contains
phenylalanine.
Copyright 2010, John Wiley & Sons, Inc.
Protein Digestion and Food Allergies
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Food allergies are triggered when a protein from the
diet is absorbed without being completely digested.
Proteins from milk, eggs, nuts, wheat, soy, fish and
shellfish and peanuts are common causes of food
allergies
A rapid, severe allergic reaction is called anaphylaxis.
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Amino Acid Pool Allows for Amino
Acid Availability
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Protein Synthesis: Transcription and
Translation
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The sequence of amino acids in a polypeptide chain is
determined by
a) the types of food a person eats.
b) the genetic material DNA.
c) digestive enzymes called proteases.
d) the hormone insulin.
Copyright 2010, John Wiley & Sons, Inc.
Energy Production from Protein
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Protein Functions
Examples of proteins
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Enzymes speed up metabolic reactions (ie: trypsin)
Transport proteins move substances in and out of cells
(ie: hemoglobin)
Antibodies help the immune system in fighting off
foreign bodies.
Contractile proteins help the muscles to move.
Hormones are chemical messengers, such as insulin
and glucagon.
Proteins help to regulate fluid and acid-base balance.
Copyright 2010, John Wiley & Sons, Inc.
Protein Deficiency
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Protein-energy malnutrition (PEM) is a
term that covers a range of protein
deficiency conditions that may include only
protein deficiency or protein deficiency plus
energy deficiency.
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Kwashiorkor is a pure protein deficiency.
Marasmus is an energy deficiency.
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Kwashiorkor is a pure protein deficiency
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Marasmus is an energy deficiency.
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Protein Excess
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Elevated protein intakes over long periods of
time can result in:
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Hydration and kidney function issues
Bone health issues
Increased risk of heart disease and cancer
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Nitrogen Balance
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Determining Protein Requirements
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Calculating Protein Requirements
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One reason to get more
of your protein from
plants would be?
to get more fiber
to get more poly
and mono
unsaturated fats
to lower blood
cholesterol
All answer
choices are
correct.
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How do you meet your needs
if you are a vegetarian?
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Using MyPyramid for Daily Protein
Selection
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Meeting Protein Needs with a Vegan
Diet
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Considering Protein Quality
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Considering Protein Quality
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Meeting Protein Needs with a
Vegetarian Diet
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Meeting Nutrient Needs with a Vegan
Diet
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Food allergies involve an
interaction between a protein
from the diet and
the immune system.
the excretory system.
the genetic material
DNA.
the genetic material
RNA.
Copyright 2010, John Wiley & Sons, Inc.
The amino acid pool refers
to amino acids
a)
which are soluble in
bodily fluids.
b)
present in body
tissues and fluids
that are available for
protein synthesis.
c)
d)
amino acids which
are used by the body
for energy.
which the body is
not able to make
and must be
supplied by the diet.
Copyright 2010, John Wiley & Sons, Inc.
Chapter 6
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