Slide 1 - Cengage
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Chapter 6
The Proteins and Amino Acids
Nutrition: Concepts & Controversies, 12e
Sizer/Whitney
Learning Objectives
Describe why some amino acids are
essential, nonessential, or conditionally
essential to the human body, and state the
outcome should any one of them be lacking
in the diet.
Compare the digestion of protein and
transport of amino acids with digestion and
transport of lipids in the body.
Discuss the roles that various proteins and
amino acids can play in the body.
Learning Objectives
Describe the fate of amino acids consumed
with a balanced diet versus a carbohydratepoor diet.
Discuss the concept of nitrogen balance
and compute the amount of protein needed
for a healthy college student.
Learning Objectives
Identify the major forms of protein
malnutrition, and discuss reasons why
consuming too much protein is not
recommended.
Summarize the health advantages and
nutritional risks of a vegan diet.
Develop a lacto-ovo vegetarian diet plan
that meets all nutrient requirements for a
given individual.
The Structure of Proteins
Difference from carbohydrates and fats
Amino acids
Carbon atom with amine group and acid
group
Side chain
Essential amino acids
Conditionally essential
Recycling
Priority system
How Do Amino Acids Build
Proteins?
Peptide bonds
Link amino acids
Strands of amino acids do not remain
straight
Coils
Folds
Side chain electrical charge
Activation
The Coiling and Folding of a
Protein Molecule
The Structure of Hemoglobin
The Variety of Proteins
Protein shapes enable performance of
different tasks
Examples
Protein strands – alone or in association
Inherited amino acid sequences
Alterations to sequence
Sickle-cell disease
Nutrients and gene expression
Normal Red Blood Cells and
Sickle Cells
Protein Synthesis
Denaturation of Proteins
Denaturing agents
Digestion
Stomach acid
Dangers of
denaturation
Protein Digestion
Stomach
Denatures protein in food
Uncoil protein’s strands
Enzymes attack peptide bonds
Small intestine
Polypeptides
Further break down
Common misconceptions
A Dipeptide and Tripeptide
How Protein in Food Becomes
Amino Acids in the Body
Amino Acid Absorption
Absorbed by cells of small intestine
Larger molecules
Hormones or allergens
Separate sites for absorption
Released into the bloodstream
Carried to the liver
The Importance of Protein
Amino acids must
be continually
available
Building of new
proteins
Amino acids are
needed each day
Protein turnover
Roles of Body Proteins
Regulation of gene expression
Providing structure and movement
Muscle tissue
Other structural proteins
Building enzymes, hormones, & other
compounds
Building antibodies
Enzyme Action
Amino Acid Sequence of Human
Insulin
Roles of Body Proteins
Transporting substances
Hemoglobin and lipoproteins
Maintaining fluid and electrolyte balance
Edema
Maintaining acid-base balance
Blood clotting
Providing energy and glucose
Proteins Transport Substances
Into and Out of Cells
Amino Acids to Glucose
Protein can help maintain blood glucose
levels
No storage compound for protein
Dismantle tissue proteins
Oversupply of amino acids
Remove amine group
Use of residues
Three Different Energy Sources
Amino Acids to Glucose
Fate of an amino acid
Cellular use
Build protein
Make a needed compound
Dismantle amino acid for component parts
Wasting of amino acids
Preventing waste
Protein and Amino Acid
Supplements
Protein supplements
Do not improve performance
Not effective for weight loss
Amino acid supplements
Body designed to work with whole proteins
No safe level of amino acid supplementation
People Most Likely to Be Harmed
by Amino Acid Supplements
How Much Protein Do People
Really Need?
DRI
Depends on body size
Infants and growing children
Recommended intake
Vegetarians
Minimum amount
Upper limit
Body’s health
Quality
Nitrogen Balance
Nitrogen excreted as compared to nitrogen
eaten
Levels in healthy adults
Variation in nitrogen balance
Positive balance
Examples
Negative balance
Examples
Nitrogen Balance
Which Foods Provide High Quality
Protein?
High-quality proteins
Enough of all essential amino acids
Limiting amino acids
Complementary proteins
Mutual supplementation
Protein digestibility
Animal proteins
Legumes
Complementary Protein
Combinations
Protein Deficiency and Excess
World’s leading form of malnutrition
Combined with energy deficiencies
Protein-energy malnutrition (PEM)
Locations of prevalence
Effects of PEM
Children and adults
Two forms
Protein Deficiency and Excess
Marasmus
Common in
children
Muscle wasting
Impairments
Disease conditions
Preventing death
Heart failure
Protein Deficiency and Excess
Kwashiorkor
Weaning of babies
Fluid balance is
diminished
Changes in body
Risk of infection
PEM at home
Protein Deficiency and Excess
Overconsumption of protein-rich foods
Possible health risks
U.S. protein intakes
Heart disease
Homocysteine
Kidney disease
Adult bone loss
Cancer
Getting Enough but Not Too Much
Protein
Protein-rich foods
Protein is critical to nutrition
Displacement of other necessary foods
Advantages of legumes
Protein
Vitamin and mineral source
Soybeans
Top Contributors of Protein to the
U.S. Diet
A Legume
Vegetarian and Meat-Containing
Diets: What Are the Benefits and
Pitfalls?
Controversy 6
Vegetarian Diets
Reasons to choose a vegetarian lifestyle
Categorization of vegetarians
By foods they choose to eat
Reasons why meat eaters choose to eat
meat
Terms Used to Describe
Vegetarians and Their Diets
Positive Health Aspects of
Vegetarian Diets
Other health behaviors associated with
being vegetarian
Obesity
Heart disease
Blood lipids
Hypertension
Cancer
Other health benefits
Positive Health Aspects of the
Meat Eater’s Diet
Critical times in life
Examples
Pregnancy and infancy
Childhood
Adolescence
Aging
Planning a Vegetarian Diet
Vegetarian food guides
Ensure adequate intakes
Protein
Iron
Zinc
Calcium
Vitamin B12
Vitamin D
Omega-3 fatty acids
My Vegetarian Food Pyramid
Nutrients in Nonfat Milk and Light
Soy Milk