Proteins From Foods to Cells in the Body

Presentation Overview • • 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? – 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? – 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 3 rd 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: – – Dehydration. Liver & spleen enlargement. Accelerated kidney aging. Metabolic acidosis (with low carbohydrate intake) – Vitamin B 6 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 7 gm/oz 7 gm/white • 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. 7 gm/oz 3 gm/0. 5 c 2 gm/0. 5 c 4 gm/0. 5 c 3 gm/slice 3 gm/0. 5 c

Summary • 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 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