Proteins: Proteins: From Foods to Cells in the BodyFrom Foods to Cells in the Body

By Jennifer Turley and Joan ThompsonBy Jennifer Turley and Joan Thompson

© 2013 Cengage© 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.

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 Functions1. Growth & tissue maintenance (replace, repair &

possibly add LBM).2. Enzymes (catalysts). 3. Antibodies, complement proteins, circulating

components of immunity.4. Fluid & electrolyte balance (free proteins).5. Acid - base balance (H donors & acceptors).6. Energy (4 Cals/gm, requires N removal).7. Protein hormones like insulin & glucagon, secretin &

cholecystokinin.8. 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 3rd world countries.

• In the U.S. individuals who are on starvation diets, poor, abused, or in hypermetabolic states can experience Kwashiorkor or Marasmus.

MarasmusMarasmus

KwashiorkorKwashiorkor

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.

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.

3 gm/slice3 gm/slice

7 gm/oz7 gm/oz

7 gm/white7 gm/white

2 gm/0.5 c2 gm/0.5 c3 gm/0.5 c3 gm/0.5 c

3 gm/0.5 c3 gm/0.5 c

7 gm/oz7 gm/oz

4 gm/0.5 c4 gm/0.5 c

7 gm/oz7 gm/oz

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