1. Copyright © 2011 Pearson Education, Inc. PowerPoint® Lecture Slide Presentation Created by Susan Tripp, MS, RD, LDN UMass Memorial Medical Center Proteins: Facts to Know Concept 13

2. Copyright © 2011 Pearson Education, Inc. Pop Quiz True or False? 1.Proteins are made up of amino acids. 2.Excess dietary protein is stored by the body as fat. 3.Proteins provide structural support in your body. 4.Most enzymes in your body are proteins. 5.Your body can use protein as an energy source. ANSWER

3. Copyright © 2011 Pearson Education, Inc. What Are Proteins?  The Building Blocks of Proteins Are Amino Acids  Essential and Nonessential Amino Acids  Building Proteins from Amino Acids  Protein Function Is Altered by Denaturation  What Happens to the Proteins You Eat?

4. Copyright © 2011 Pearson Education, Inc. The Building Blocks of Proteins Are Amino Acids  Proteins are the predominant structural and functional materials in every cell in the body.  Amino acids are the building blocks of proteins.  Amino acids are like digits in a phone number—they link together to form unique sequences with a specific purpose.  Contain carbon, hydrogen, oxygen, and nitrogen  A unique side chain gives the amino acid its distinguishing qualities.  There are 20 amino acids.  Categorized as either essential or nonessential

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6. Essential and Nonessential Amino Acids  There are nine essential amino acids.  The body cannot synthesize these.  Must be obtained from foods  Found in foods such as meat and milk  The remaining 11 are nonessential amino acids.  These can be created in the body so are not essential in the diet.

7. Copyright © 2011 Pearson Education, Inc. Building Proteins from Amino Acids  Amino acids are joined by peptide bonds.  Dipeptide: two amino acids joined  Tripeptide: three amino acids joined  Polypeptide: many amino acids joined together  Proteins typically consist of 100 to 1,000 amino acids in a specific sequence.  Fold into a distinct 3-D shape based on the interaction of the side chains with each other and the environment  Hydrophobic side chains cluster to the interior.  Hydrophilic side chains assemble on the outside surface.  The shape of a protein determines its function in the body.

8. Copyright © 2011 Pearson Education, Inc. The Making of a Protein Figure 13.2 The Building Blocks of Protein

9. Copyright © 2011 Pearson Education, Inc. Protein Function Is Altered by Denaturation  Denaturation: the alteration of a protein’s shape due to exposure to heat, acids, or salt  Doesn’t alter the sequence of amino acids  Alters its function, sometimes permanently  Examples:  Frying an egg  Marinating chicken in an acidic mixture  Acidic stomach juices denature and untangle proteins during digestion

10. Copyright © 2011 Pearson Education, Inc. Denaturing a Protein Figure 13.3

11. Copyright © 2011 Pearson Education, Inc. What Happens to the Protein You Eat?  Protein digestion begins in the stomach.  Stomach acid denatures protein strands.  The digestive enzyme pepsin breaks strands into smaller polypeptides.  In the small intestine:  Polypeptides are broken down into tripeptides and dipeptides.  These are absorbed by intestinal cells and broken down into single amino acids.  Amino acids enter the blood and travel to the liver.  The liver uses the amino acids according to your body’s needs. Animation: Protein Digestion

12. Copyright © 2011 Pearson Education, Inc. Digesting and Absorbing Proteins Figure 13.4

13. Copyright © 2011 Pearson Education, Inc. How Does Your Body Build Proteins?  Your Body Degrades and Synthesizes Proteins  DNA Directs the Synthesis of New Proteins

14. Copyright © 2011 Pearson Education, Inc. How Does Your Body Build Proteins?  The diet provides essential and nonessential amino acids.  A limited amount of all of these are stockpiled in amino acid pools in the blood and cells.  The body constantly degrades its proteins to replenish the amino acid pools and build the new proteins it needs.

15. Copyright © 2011 Pearson Education, Inc. The Fate of Amino Acids in Your Body Figure 13.5

16. Copyright © 2011 Pearson Education, Inc. Your Body Degrades and Synthesizes Proteins  Protein turnover: the process of continually degrading and synthesizing protein within the body  200 grams of protein are turned over daily.  The intestines and liver account for as much as 50 percent of turnover.  Proteins and amino acids are lost daily through sloughed-off skin, hair, nails, and intestinal cells.  Amino acid pools provide the building materials to synthesize replacement proteins and nonprotein substances such as thyroid hormones and melanin.

17. Copyright © 2011 Pearson Education, Inc. Your Body Degrades and Synthesizes Proteins  When amino acids are broken down, the component parts meet different fates.  The nitrogen forms ammonia (NH 3 ), which is converted to urea by the liver and excreted in urine via the kidneys.  The carbon-containing remnants are converted to glucose and used as energy or stored as fat.  Surplus amino acids from excess dietary protein can’t be stored as protein, so they are stored as fat.

18. Copyright © 2011 Pearson Education, Inc. DNA Directs the Synthesis of New Proteins  Deoxyribonucleic acid (DNA) is a molecule that directs protein synthesis in the body.  Each DNA molecule carries the code to synthesize every protein that you need.  The actual protein that can be synthesized depends on the specific genes expressed in the cell.  DNA can’t leave the nucleus, so messenger ribonucleic acid (mRNA) delivers the protein synthesis “blueprints” to the cell’s machinery.  There, transfer RNA (tRNA) gathers the amino acids needed to make the desired protein. Animation: Protein Synthesis

19. Copyright © 2011 Pearson Education, Inc. Protein Synthesis Figure 13.6

20. Copyright © 2011 Pearson Education, Inc. DNA Directs the Synthesis of New Proteins  Abnormalities in protein synthesis can result in serious medical conditions.  Sickle-cell anemia is a blood disorder caused by abnormal formation of the protein hemoglobin.  Displacement of one amino acid causes the hemoglobin chains to stick to one another.  Red blood cells are stiff and sickle (half-moon) shaped under certain conditions when oxygen levels are low.  Abnormal cells can build up in blood vessels, causing painful blockages and damage to tissues and organs.

21. Copyright © 2011 Pearson Education, Inc. How Does Your Body Use Proteins?  Proteins Provide Structural and Mechanical Support  Proteins Help Maintain Body Tissues  Proteins Build Enzymes and Hormones  Proteins Help Maintain Fluid Balance  Proteins Help Maintain Acid-Base Balance  Proteins Transport Substances throughout the Body  Proteins Are Needed for Antibodies and the Immune Response  Proteins Can Provide Energy

22. Copyright © 2011 Pearson Education, Inc. Proteins Provide Structural and Mechanical Support  Fibrous proteins in your bones, muscles, and other tissues help hold up your body.  Collagen is the most abundant protein in your body and is found in all of your connective tissues, including bones, tendons, and ligaments.  Other proteins provide mechanical support by helping your muscles contract.  Eating extra protein won’t make muscles larger, but weight-bearing exercise will.

23. Copyright © 2011 Pearson Education, Inc. Proteins Help Maintain Body Tissues  Daily wear and tear on the body causes breakdown of hundreds of grams of protein each day.  Proteins help create a new layer of outer skin every 25 to 45 days.  Your body has trillions of red blood cells with life spans of just 120 days.  The cells lining the inner surface of your organs (such as lungs and intestines) are constantly sloughed off, excreted, and replaced.  Protein is essential in healing.  Extensive wounds or burns can more than triple protein needs.

24. Copyright © 2011 Pearson Education, Inc. Proteins Build Enzymes and Hormones  Enzymes are substances that speed up reactions in the body.  Many are proteins  Are not changed, damaged, or used up in the process  Many reactions also utilize a coenzyme, such as a vitamin, to initiate the reaction.  Hormones are protein- or lipid-based chemical messengers that initiate or direct a specific action.  Released from tissues and organs and travel to target cells in another part of the body to direct an activity  Examples: glucagon and insulin

25. Copyright © 2011 Pearson Education, Inc. An Enzyme in Action Figure 13.7

26. Copyright © 2011 Pearson Education, Inc. Proteins Help Maintain Fluid Balance  Proteins help ensure that the water in your body is distributed evenly.  Fluids can flow easily through capillaries and into the spaces between cells.  Proteins are too big to cross cell membranes.  Proteins attract water and draw fluids back into the capillaries to maintain a balance.  During severe malnutrition, fewer proteins are available and fluid imbalances and edema can result.

27. Copyright © 2011 Pearson Education, Inc. Edema Figure 13.8

28. Copyright © 2011 Pearson Education, Inc. Proteins Help Maintain Acid-Base Balance  Normal blood pH is 7.4.  Acidosis: a pH below 7.35; can result in a coma  Alkalosis: a pH above 7.45; can result in convulsions  Proteins act as buffers in your blood.  Minimize changes in acid-base levels by picking up or donating hydrogen ions from some amino acid side chains

29. Copyright © 2011 Pearson Education, Inc. Proteins Transport Substances throughout the Body  Transport proteins carry oxygen, waste products, lipids, some vitamins, sodium, and potassium through your blood and cell membranes.  Hemoglobin acts as a transport protein for oxygen and carbon dioxide.  In cell membranes, transport proteins control the entry and exit of sodium and potassium.  Substances that are not lipid soluble or are too large to pass through the cell membrane must use a protein channel.

30. Copyright © 2011 Pearson Education, Inc. Protein Transport Figure 13.9

31. Copyright © 2011 Pearson Education, Inc. Proteins Are Needed for Antibodies and the Immune Response  The immune system uses specialized proteins called antibodies to tag potentially harmful substances for elimination from the body.  Immunity occurs once your body knows how to create antibodies against a specific invader.  An allergic reaction is caused by the body incorrectly perceiving a nonthreatening substance as harmful and attacking it.

32. Copyright © 2011 Pearson Education, Inc. Proteins Can Provide Energy  Proteins provide 4 calories per gram.  When the diet contains adequate calories from carbohydrates and fat, proteins are spared for other important roles in the body.  In times of starvation, the body breaks down protein from muscles for energy.  The waste products from protein breakdown must be eliminated, which is a burden for the liver and kidneys.

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35. The Top Five Points to Remember 1.Proteins are made of amino acids joined together by peptide bonds. The are 20 different amino acids, each characterized by a unique side chain. 2.The interaction between the side chains of amino acids cause a protein to fold into a precise three- dimensional shape, which determines its function. Heat, acids, and salts disrupt the shape and function of a protein. 3.Of the 20 amino acids, nine are essential and must be obtained through the diet. The body can synthesize the remaining 11 amino acids.

36. Copyright © 2011 Pearson Education, Inc. The Top Five Points to Remember 4.A limited number of amino acids are readily available in pools in your body. DNA within your cells directs the synthesis of proteins. Excess amino acids are broken down and stored in another form or used as energy. The nitrogen is converted into the waste product urea and excreted in urine. 5.Proteins play many roles in the body. They provide structural support, supply materials for ongoing maintenance, form enzymes and hormones, maintain acid-base and fluid balance, transport nutrients, aid your immune system, and provide energy when needed.

37. Copyright © 2011 Pearson Education, Inc. Answers to the Pop Quiz 1.TRUE. Amino acids are the building blocks of protein. BACK TO QUIZ

38. Copyright © 2011 Pearson Education, Inc. Answers to the Pop Quiz 2.TRUE. All excess calories are eventually stored as fat. BACK TO QUIZ

39. Copyright © 2011 Pearson Education, Inc. Answers to the Pop Quiz 3.TRUE. Protein is needed to “hold up” your body. BACK TO QUIZ

40. Copyright © 2011 Pearson Education, Inc. Answers to the Pop Quiz 4.TRUE. There are thousands of unique enzymes in your body, and most are made of protein. BACK TO QUIZ

41. Copyright © 2011 Pearson Education, Inc. Answers to the Pop Quiz 5.TRUE. However, using protein, rather than carbohydrates or fat, for energy is an inefficient way to use this precious nutrient. BACK TO QUIZ