1. Kin 110 Lecture 5
Ch. 6 Proteins

2. Objectives Describe how amino acids make proteins
Distinguish between essential and non essential amino acids
List primary functions of protein in the body
Calculate the RDA for protein for a healthy adult from body weight
Distinguish between complete (high-quality) and incomplete (low-quality) sources of protein
Describe complementary sources of lower quality proteins
Develop vegetarian diet plan that meets the body’s nutritional needs

3. Overview of Proteins
Thousands of substances in body are made of protein
Protein is the major non-water component of lean tissue (16 %)
20 different amino acids
building blocks of protein
9 essential - must be obtained from diet
Complete protein
high quality - all essential a.a. in ample amounts -
Incomplete protein
lower quality - lack sufficient amount of one or more essential a.a.
simple combinations of incomplete protein sources are complementary providing all essential a.a. in meal

4. Overview of Protein Proteins crucial for thousands of body processes
each function requires a specific protein
The sequence of a.a. determines the structure and function
body uses a.a. from diet as building blocks for many configurations and sizes of proteins for these varied functions
without proper essential a.a. in diet, body functions slow, immune system begins to fail
Require essential aa for production of protein to continue

5. Amino Acids Amino acids have general structure
variations in ‘R’ region determine functional characteristics (p. 190)
20 a.a. - 9 essential - can not be made by the body - required in diet
Table 6-1
Semi-essential (physiologically)
Must be made from essential aa if not enough consumed in the diet
PKU - Phenylketonuria
inability to process phenylalanine (ess.) into tyrosine (non-essential)
Tyrosine becomes an essential a.a.

6. Dietary Considerations (essential vs. non-essential)
Complete protein
contains all 9 essential a.a.
Animal protein and Soy protein
Incomplete protein
lacks one or more essential a.a.
most plant proteins
Important as all a.a. are necessary for protein synthesis
All or None Principle of protein synthesis
ALABAMA eg.

7. Complementary Proteins
Various plant sources can compensate for essential a.a. deficiencies in one food source
Adults should have little concern, combination over entire day is important
more attention required for young children - growth
Table 6-2
* know traditional cultural combinations that make complete protein in diet *

8. Protein Amino acids joined by peptide bonds
thousands of different proteins
Letters making sentences, paragraphs
order directed by DNA, genes
Protein synthesis - fig 6.1
Creates specific and unique 3-D structure, necessary for function
Eg. Sickle cell anemia - fig 6.3
Slight error in a.a. order
Structure of hemoglobin is altered, leaving it non functional

9. Denaturing of Protein Breaking down structure
Acid, alkaline, Heat or agitation
alters protein 3-D structure
destroys normal function
Cooking, makes foods safer to eat and facilitates further digestion (exposure to enzymes)
* recall - we dismantle proteins for the a.a. building blocks*
aa are absorbed and synthesized into proteins in the body

10. Protein Digestion Fig 6.6 Begins in stomach Creates Peptones
Enzyme Pepsin
breaks proteins into smaller a.a. sequences (selected bonds are broken)
Creates Peptones
Hormone Gastrin controls release of Pepsin and Acid in stomach
Thinking about food and chewing food stimulates gastrin production and release in stomach
acid activates pepsin and denatures proteins so that enzyme can act on it

11. Small Intestine
Protein and Fat in SI trigger pancreatic juice to be released
breaks peptones into shorter sequences and a.a.
a.a. and short sequences are able to be absorbed in SI
In infancy - whole proteins can be absorbed - important in transferring immunity from mother in milk
travel to liver (portal circulation)
recombined into protein
converted to glucose or fat
released to blood to be taken up by other tissues

12. Functions of Proteins
To ensure availability of ingested protein for these functions, you must take in sufficient carbohydrates and fat for energy needs
Taking in excess protein does not enhance any of these functions
Vital body constituents
most are in a constant state of breakdown, rebuilding and repair
most a.a. can be recycled, but some are lost, requiring constant intake in small amounts.

13. Other Protein Functions
Maintaining fluid balance
Blood Proteins
Pressure in blood pushes fluid out of capillaries to bathe cells
albumin and globulins (proteins) bring fluid back into the bloodstream after in leaves at the capillaries
prevents edema (swelling) - fig 6.8
Acid Base Balance
proteins in membranes pump ions in an out of cell
buffers; take away and add acid (H+) as required
Some blood proteins are good buffers

14. Other Protein Functions
Hormones (insulin, glucagon), Enzymes (all enzymes) are protein and many Neurotransmitters (norepinephrine) are derived from a.a.
Immune Functions
Antibodies
Rapid production requires ample protein availability
excess protein does not boost immune function
Formation of glucose and Fat
Excess protein stored as fuel
With inadequate carbohydrate intake, protein used to produce glucose (fig 6.7)
Provision of Energy
costly processing

15. Protein Intake Protein equilibrium - fig 6-9
need to balance intake with output
output measure as nitrogen in urine (protein broken down)
Positive protein balance - required for growth, recovery from illness, training
requires insulin, growth hormone, testosterone
Negative protein balance - occurs with inadequate intake, infections, bed rest

16. RNI for Protein .8 g/Kg healthy body weight 56 g for 155 lb man
double for infants
56 g for 155 lb man
.8 g/kg * kg = 56g
44 g for 120 lb woman
2-3 servings per day
mental stress and physical labor do not increase requirement for protein
World class athletes may benefit from up to 1.5 g /Kg
Pregnancy inc. need by 10-15g / day
elderly may have higher needs
Helps maintain muscle mass (1.2g/kg)

17. Serving of Protein ? Recommend 2-3 servings per day Meat and fish
55g of protein (150 lb man)
Meat and fish
One serving is about g of meat
Size of cassette tape or pack of cards
Contains g of protein
Can of tuna - 25 g of protein
Serving is 1/3 - 2/3 of a can
Burger g of protein
Egg 1-2 for a serving of protein
one large egg - 6-7g of protein
Nuts - one ounce - handful
Beans - 1/2 cup
Peanut butter - one serving - 2 tbsp
Tofu - 100g - 1/3 cup

18. Other sources of protein
Table 6.3
Protein is also found in servings of food from other food groups
milk or soy milk - 8 g/cup
Spinach - 7 g / cup
Cheese - 7g / ounce
Bread - 5 g / 2 slices

19. High Protein Diet? Increased saturated fat intake, lower fiber intake
may be related to colon cancer
May increase loss of calcium
May compromise kidney health
in diabetics and those with kidney disease or kidney stones
may accentuate heart disease
homocysteine
Recommended not to exceed 2 X RNI
average diet already X RNI
Use whole foods NOT supplements
athlete diet is already larger than average, they already take in more protein with a balanced diet

20. Protein-Energy Malnutrition (PEM)
Protein deficiency usually accompanies a deficiency of dietary energy and other nutrients
Children in developing areas of the world
Marasmus - “ to waste away ”
severe nutrient deficiency - energy and protein
Little or no subcutaneous fat
Kwashiorkor - “ the disease the first child gets when the new child comes ”
Diet switches from mothers milk to low protein starches and high fiber (bulk)
Edema with some subcutaneous fat are symptoms
Risk of more severe disease conditions also listlessness, failure to grow and gain weight

21. Protein Sources Fig 6.4 Nuts are a great source of protein
Animal sources - most dense
65 % of protein from animal sources in US
20 % of protein from animal sources in Africa and parts of Asia
Plant sources - complementary proteins complete dietary needs for essential amino acids
Also high in Magnesium and Fiber
no cholesterol and little saturated fat
Nuts are a great source of protein
Less saturated fat, high in phytochemicals (flavonoids)
Vit E, Magnesium, calcium and fiber
30 g (one ounce) of nuts (handful) or two table spoons of peanut butter recommended per day

22. Vegetarianism p 213 - 216 Why become a vegetarian?
Political, Ecological and Health reasons
Often a combination of many reasons
Omnivore - both plant and animal
Vegan - only plant foods
Lactovegetarian - plant and dairy
Lactoovovegetarian - plants, dairy and eggs
Concerns - essential a.a., essential fatty acids, vitamin B-12, calcium, iron
Table nutrients supplied in plant sources
Fig vegetarian diet pyramid

23. Soy Protein p 199 Health Benefits Soy milk is often enriched with
lowers LDL
Lowers blood cholesterol
25g / day
May reduce symptoms of menopause
isoflavones act as plant-like estrogens
May increase of maintain bone density
May slow growth of prostate cancer cells
not recommended for women with breast cancer
Antioxidant
vascular dilation
Soy milk is often enriched with
calcium, riboflavin, zinc,
vitamins A, D and B12