Proteins: From Foods to Cells in the Body By Jennifer Turley and Joan Thompson © 2013 Cengage

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. Done in stomach due to Hcl

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. Absorbed thru active transport.

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 DNA is converted to RNA through transcription in the nuclues Then the mRNA is used to order the amino acids in the protein through translation. So the transfer RNA transfers the amino acids to the ribosome to be translated to a protein.

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 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). 3. Like Ige 4. Free proteins – amino acid pool used in fluid and electrolyte balance in body 5. Acid base in kidney fxn. – H donors…pathway 8. Like HDL, LDL

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% Adult DRI is 0.8 gm/Kg AMDR is 10-35%

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: Dehydration. Liver & spleen enlargement. Accelerated kidney aging. Metabolic acidosis (with low carbohydrate intake) Vitamin B6 deficiency, Ca & Zn loss. Heart disease & cancer. Dehydration –– with excess protein …water is part of muscle so is used in muscle Liver and spleen - used in protein synthesis….liver overworked Kidney aging – kidney does work in acid base and in excreting nitrogenous waste…so protein excretion Acidosis – with low carb – kidneys involved in acidosis…state Vit b6 – used in tranamination process or synthesis…calcium is inolved in albumin n so is zinc Ha and Ca – is due to high intake of meat Heart dx and Cancer – due to high intake of meats…arichidonic acid

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. skip

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) skip

What it takes to gain muscle 7 gm/oz 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 7 gm/white 7 gm/oz 3 gm/0.5 c 4 gm/0.5 c 3 gm/slice 2 gm/0.5 c 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