Proteins:
From Foods to Cells in the Body
By Jennifer Turley and Joan Thompson
© 2016 Cengage
Presentation Overview
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Denaturation vs. Digestion
Synthesis
Character & Types
Functions
Quality
Needs (Recommended Intake)
Deficiency vs. Excess
Protein Denaturation
• Causes the protein to change
shape or conformation.
• The protein and the amino acids
are still intact.
• Can be caused by heat, alkali or
acid treatments, or metals.
• Is required before the protein can
be digested.
Protein Digestion
• The protein strand is broken and
the amino acids are released.
• Occurs by the protease enzymes
secreted by the pancreas and GI
mucosal cells.
• Amino acids are absorbed,
transported to cells and then
used to build proteins.
Protein Denaturation to
Digestion
Protein Synthesis
• We eat protein, denature &
digest the protein, absorb &
transport the amino acids to the
cells, then within each cell,
protein is made (synthesized)
according to the DNA.
• Protein is synthesized in a
process of converting DNA to
RNA & then protein.
The Gene Encodes Proteins
Protein Synthesis inside the Cell
Protein
Character
• Protein Character
is determined by:
– How the 20 amino
acids are
combined
together (the
sequence).
– The polypeptide
strand folding &
interacting.
Types of Protein
Fibrous
• Uniform in structure.
• Either exclusively helical
or sheet formation.
• Examples are the
proteins found in hair,
muscle fibers & finger
nails.
Globular
• Have variation in
structure.
• Are part helical, part
sheet, part random, or
completely random.
• Examples of globular
proteins include blood,
mucous, milk protein and
egg white.
Low & high quality dietary proteins support these
Protein Functions
1.
2.
3.
4.
5.
6.
7.
8.
Growth & tissue maintenance (replace, repair &
possibly add LBM).
Enzymes (catalysts).
Antibodies, complement proteins, circulating
components of immunity.
Fluid & electrolyte balance (free proteins).
Acid - base balance (H donors & acceptors).
Energy (4 Cals/gm, requires N removal).
Protein hormones like insulin & glucagon, secretin &
cholecystokinin.
Transportation of nutrients (lipoproteins).
Adult Protein Need (DRI & AMDR)
Sample Calculations
• Eric weighs 90 Kg and ate 88 g of protein
and 3000 Calories in one day.
• What is his DRI for protein? Adult DRI is 0.8 gm/Kg
– 90 Kg x 0.8 gm/Kg = 72 gm protein
• What % of his DRI for protein did he
consume?
– 88 gm ÷ 72 gm x 100 = 122%
• What % of Calories in his diet came from
protein? AMDR is 10-35%
– 88 g protein x 4 Cal/gm = 352 Cals from protein
– 352 Cals ÷ 3000 Cals x 100 = 11.7%
Protein Deficiency
• Protein deficiency is called
Kwashiorkor. The individual has
peripheral edema and may not
look undernourished.
• Protein-Energy deficiency is
called Marasmus. The individual
looks undernourished (skin &
bones, starvation).
• Both conditions occur primarily
in 3rd world countries.
• In the U.S. individuals who are
on starvation diets, poor,
abused, or in hypermetabolic
states can experience
Kwashiorkor or Marasmus.
Kwashiorkor
Marasmus
Protein Excess
• Is most common in athletes & fad
dieters.
• Increases risk of:
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Dehydration.
Liver & spleen enlargement.
Accelerated kidney aging.
Metabolic acidosis (with low carbohydrate
intake)
– Vitamin B6 deficiency, Ca & Zn loss.
– Heart disease & cancer.
Body Builders:
sample diet
• Meal 1: Cooked cereal, 12 egg whites,
banana, 1 piece whole wheat toast,
coffee, water, vitamin/mineral & amino
acid supplements.
• Meal 2 (Pre-workout): Protein powder,
carbohydrate powder, amino acids.
• Meal 3 (Post-workout): 8 oz poultry, rice,
sweet potato, corn, non-starchy
vegetable, amino acids.
• Meal 4: 7 oz fish, rice, salad, potato,
water, amino acids.
• Meal 5: 8 oz beef, potato, mixed
vegetable, water, amino acids.
• Meal 6: Cooked cereal, 10 egg whites,
amino acids.
Body Builders:
sample diet analysis results
• 5500 Calories
• 36% Calories from protein,
49% carbohydrate, 15% fat
• Inadequate in vitamin E (83%
DRI) and Calcium (75% DRI)
What it takes to gain muscle
• One pound muscle is: 75% water, 20%
protein, 5% other material like fat,
glycogen, minerals, enzymes.
• One pound muscle equals 105 grams
protein.
• To gain one pound muscle in 2 weeks
an athlete would need an extra 7-8 g
protein/day intake.
– 1 oz meat, 1 cup milk, 3 slices bread.
Some
Summary Points
• Dietary protein is denatured then
digested.
• The amino acids from dietary
intake are used by cells to make
proteins by converting DNA to
RNA to protein.
• Protein character is determined
by amino acid sequence.
Summary
• Proteins types: fibrous & globular.
• Proteins have many functions in the
body.
• Protein deficiency is called
kwashiorkor. Protein-energy
malnutrition is Marasmus.
• Protein excess can led to negative
health affects.
References for this presentation are the same as those for this topic found in
module 3 of the textbook