Slide1 : Chapter 6: The Proteins and Amino Acids
Introduction : Introduction What do you think of when you hear the word “protein”?
Proteins have many roles in the body, but their basic structure is the same Hair, skin, eyesight, and the health of the whole body depend on protein from food
The Structure of Proteins : The Structure of Proteins The structure of proteins enables them to perform many vital functions
Proteins contain nitrogen, unlike CHO and fat.
Amino acids are the building block.
20 different amino acids exist.
Amino Acids : Amino Acids
Amino Acids : Amino Acids
Essential Amino Acids : Essential Amino Acids 9 amino acids are essential
11 amino acids are nonessential
Under special circumstances, a nonessential amino acid can become essential - conditionally essential amino acids
How Do Amino Acids Build Proteins? : How Do Amino Acids Build Proteins? Amino acids link into long strands that coil and fold to make a wide variety of different proteins.
Several strands may cluster together into a functioning unit, or a metal ion (mineral) or a vitamin may join to the unit and activate it.
How Do Amino Acids Build Proteins? : How Do Amino Acids Build Proteins?
The Variety of Proteins : The Variety of Proteins Each type of protein has a distinctive sequence of amino acids and so has great specificity.
Like letters in the alphabet, the sequence of amino acids determines the identity of the protein.
The Variety of Proteins : The Variety of Proteins Hemoglobin, found in red blood cells is made of four associated protein strands,
each holding the mineral iron.
The Variety of Proteins : The Variety of Proteins The variety of possible sequences for amino acid strands is tremendous.
A single human cell may contain as many as 10,000 different proteins, each one present in thousands of copies.
Denaturation of Proteins : Denaturation of Proteins Proteins can be denatured (distorted in shape) by heat, radiation, alcohol, acids, bases, or the salts of heavy metals.
During digestion, stomach acid denatures proteins, permitting digestive enzymes to make contact with the peptide bonds and cleave them.
During cooking, denaturation also occurs.
Protein Digestion : Protein Digestion
The Roles of Proteins in the Body : The Roles of Proteins in the Body Proteins are versatile, unique, and play important roles in the body
Proteins have been called “the primary material of life”
Supporting Growth and Maintenance : Supporting Growth and Maintenance The body needs dietary amino acids daily to grow new cells and to replace worn-out ones
The entire process of breakdown, recovery, and synthesis is called protein turnover.
Building Enzymes, Hormones, and Other Compounds : Building Enzymes, Hormones, and Other Compounds The body makes enzymes, hormones, and chemical messengers of the nervous system from its amino acids
Building Antibodies : Building Antibodies Antibodies are proteins that defend against foreign proteins and other foreign substances within the body
Maintaining Fluid and Electrolyte Balance : Maintaining Fluid and Electrolyte Balance Proteins help regulate the body’s electrolytes and fluids
Maintaining Acid-Base Balance : Maintaining Acid-Base Balance Proteins buffer the blood against excess acidity or alkalinity.
Blood Clotting : Blood Clotting Proteins that clot the blood prevent death from uncontrolled bleeding.
Providing Energy and Glucose : Providing Energy and Glucose When insufficient carbohydrate and fat are consumed to meet the body’s energy need, food protein and body protein are sacrificed to supply energy.
The nitrogen part is removed from each amino acid, and the resulting fragment is oxidized for energy.
No storage form of amino acids exists in the body.
The Fate of An Amino Acid : Amino acids are “wasted” when:
Energy is lacking from other sources.
Protein is overabundant.
An amino acid is oversupplied in supplement form.
The quality of the diet’s protein is too low (too few essential amino acids). The Fate of An Amino Acid
Food Protein: Quality, Use, And Need : Food Protein: Quality, Use, And Need The body’s use of a protein depends in part on the user’s health.
To be used efficiently, protein must be accompanied by ample carbohydrate and fat, vitamins and minerals.
Protein quality is influenced by a protein’s digestibility and its amino acid composition.
Which Kinds of Protein-Rich Foods Are Easiest To Digest? : Digestibility of protein varies from food to food.
Amino acids from animal proteins are most easily digested and absorbed (over 90%)
Amino acids from legumes are next (80 to 90%)
Amino acids from plant foods vary (70 to 90%)
Cooking with moist heat can improve digestibility whereas dry heat methods impair it. Which Kinds of Protein-Rich Foods Are Easiest To Digest?
Amino Acid Composition : Amino Acid Composition High-quality proteins – provide enough of all of the essential amino acids needed to make new proteins
Low-quality proteins – do not provide all the essential amino acids
If a nonessential amino acid is unavailable from food, the cell synthesizes it
If the diet fails to provide an essential amino acid, the cells begin to conserve the amino acid and reduce their use of amino acids for fuel.
Complementary Proteins : Complementary Proteins If a person does not consume all the essential amino acids it needs, the body’s pools of essential amino acids will dwindle until body organs are compromised.
Proteins lacking essential amino acids can be used only if those amino acids are present from other sources.
Complementary Proteins : Complementary Proteins
Complementary Proteins : Complementary Proteins Mutual supplementation
Complementary Proteins : Who needs to be concerned about mutual supplementation?
Everyone
Lacto-ovo vegetarians
Pregnant women
Growing children
Vegans Complementary Proteins Answer: Vegans
How Much Protein Do People Really Need? : How Much Protein Do People Really Need? The DRI recommendation for protein intake depends on size and stage of growth
DRI recommended intake is 0.8 gram per kilogram of body weight
Minimum is 10 percent of total calories
Athletes may need slightly more (1.0 gram per kg)
How Much Protein Do People Really Need? : The DRI recommended intake is 0.8 g/kg
To figure your protein need:
Find your body weight in pounds
Convert pounds to kilograms (by dividing pounds by 2.2)
Multiply kilograms by 0.8 to find total grams of protein recommended How Much Protein Do People Really Need?
How Much Protein Do People Really Need? : How Much Protein Do People Really Need?
Protein Deficiency And Excess : Protein Deficiency And Excess Protein deficiencies and energy deficiencies are the world’s leading form of malnutrition
Both protein deficiencies and excess are of concern
What Happens When People Consume Too Little Protein? : What Happens When People Consume Too Little Protein? Protein-energy malnutrition (PEM) is the most widespread form of malnutrition in the world today.
PEM takes two different forms:
Marasmus
Kwashiorkor
Marasmus : Marasmus Extreme food energy deficiency The extreme loss of muscle and fat characteristic of marasmus is apparent in this child’s matchstick arms
Kwashiorkor : Kwashiorkor Kwashiorkor is the Ghanaian name for “the evil spirit that infects the first child when the second child is born.”
Each baby is weaned from breast milk as soon as the next comes along. The older baby no longer receives breast milk and is given a watery cereal with scant protein of low quality.
Kwashiorkor : Kwashiorkor The edema and enlarged liver characteristic of kwashiorkor are apparent in
this child’s swollen belly.
Kwashiorkor : Kwashiorkor
PEM At Home : PEM At Home PEM is not unknown in the United States, where millions live on the edge of hunger.
Inner cities
U.S. Indian reservations
Rural areas
Some elderly people
Hungry and homeless children
People suffering from anorexia nervosa
People with wasting illnesses such as AIDS, cancer, or drug and alcohol addictions