Chapter 7: Proteins and Fats

Define the following terms:

• 1. adipose cells—cells that sore fat from foods and grow larger as they store additional fat.

• 2. amino acids—chemical building blocks of proteins that link together in many arrangements.

• 3. cholesterol—fat-like substance in all body cells; needed for many essential body processes.

• 4. complete proteins—proteins that contain all essential amino acids.

• 5. essential amino acids—amino acids that the body needs but cannot provide; obtained from foods.

• 6. fatty acids—chemical structures that make up fats.

• 7. HDL—lipoprotein that picks up cholesterol and takes it back to liver for excretion; “good” cholesterol.

• 8. hemoglobin—protein with globular shape; transports oxygen in blood to all body cells.

• 9. hydrogenation—chemical process that turns vegetable oils into solids.

• 10. incomplete proteins—plant proteins that lack at least one essential amino acid.

• 11. LDL—lipoprotein that takes cholesterol from liver to where needed in the body; can accumulate too much; considered “bad” cholesterol.

• 12. lipoproteins—chemical “packages” that transport fatty acids through bloodstream.

• 13. monounsaturated fatty acids—unsaturated fatty acids with one hydrogen unit missing.

• 14. omega-3 fatty acids—fatty acid in fish oils, especially fatty fish; may lower risk of heart disease.

• 15. saturated fatty acids—fatty acid that contains all the hydrogen it can chemically hold.

• 16. trans fats—fats produced when oils are turned into solids in food production; they increase LDL cholesterol levels and may lower HDL.

• 17. triglycerides—type of lipid, commonly called fats.

Answer the following questions.

• 1. Chemically speaking, what is protein?

• Objects formed by amino acids that perform different functions determined by their shape.

2. What is hemoglobin?.

• A protein with a globular shape that transports oxygen in the blood to cells in the body.

3. How does protein in food become protein in the body?

• Once you’ve eaten a protein, your body breaks the protein down into amino acids. Then the amino acids can be reassembled a human body protein.

• Protein digestion starts in the stomach. First, strong stomach acid changes the shape of the proteins. Protein digestion continues in the small intestine until individual amino acids become available.

• The amino acids can then be absorbed into the bloodstream. Upon reaching the cells, the amino acids are used to make proteins for specific purposes.

4. Compare complete and incomplete proteins.

• Complete proteins: foods with all the essential amino acids.

• Incomplete proteins: foods that lack at least one essential amino acid.

5. Summarize the work of proteins in your body.

• Proteins play MANY roles in the body. These are the highlights:

• Growth and maintenance—growing new cells and repairing worn-out and damaged parts. Some cells last only a few days and must be constantly replaced.

• Enzymes—Without special proteins called enzymes, chemical reactions cannot take place at the necessary rates.

• Hormones—Hormones are chemical messengers that help regulate conditions in the body. Some are made from amino acids.

• One is the thyroid hormone that regulates metabolism. Another is insulin that helps maintain the level of glucose (sugar) in your bloodstream.

• Antibodies—Antibodies are proteins that fight invaders. The body creates them as the need arises. In this way, proteins are part of the immune system and play a major role in fighting disease.

• Fluid Balance—A cell’s life depends on having fluid in the right amount. Too much and the cell ruptures. Too little stops their activity. Cells can’t move fluids directly themselves so they build proteins inside cells to attract water. They send proteins into the blood stream too maintain fluid levels there.

6. For teens, what percentage of calories should come from

proteins?

• 10—30 percent

7. What can happen if you eat too much protein?

• Excess protein is stored as fat; if amounts are huge, the body works overtime to break down the extra protein and remove the by-products.

8. What is a health expert likely to recommend as good food

sources for protein? Why?

• Foods from plant sources because they have less fat and usually cost less.

9. After a blood test, if someone says his triglyceride level is high, what does

he mean?

• The level of fat in his blood is high.

10. Can you see fat in foods? Explain.

• You can see the fat on meats and recognize it in butter, margarine, and oil. Some fats can’t be seen because they’re part of the food’s chemical composition.

11. Why is it important to include some fat in the diet?

• Fat helps the body absorb vitamins A, D, E, and K.

• Body fat serves as a reserve supply of energy.

• Body fat cushions and protects the heart and other vital organs. It protects bones from injury.

• A layer of body fat under the skin provides insulation for warmth.

• Fat is a component of cell membranes.

• Because fats move slowly through the digestive system, they help you fell full longer after eating.

12. Use chemistry to theorize why foods heavy in saturated fatty acids are

solid at room temperature.

• Since saturated fatty acids have all the hydrogen the structure can hold, the structure may be strong enough to hold its shape.

13. If butter melts, does it become polyunsaturated? Explain.

• No, because melting is only temporary; the butter solidifies again at room temperature.

14. What happens to fats during digestion?

• They are broken down into fatty acids, which move into the bloodstream and head for the liver and tissues that need them. Many are stored in fat cells.

15. What is cholesterol and how do you get it?

• A fat-like substance in all body cells needed for many essential body processes; the body makes some but it’s also in foods from animal sources.

16. Compare LDL and HDL.

• LDL—Low-density lipoprotein, or LDL, takes cholesterol from the liver to wherever it is needed in the body. If too much LDL cholesterol is circulation, excess amounts can build up in the artery walls. This buildup increases the risk of heart disease and stroke, which earns LDL cholesterol the “bad” cholesterol reputation.

• HDL—High-density lipoprotein, or HDL, is more helpful. It picks up excess cholesterol and takes it back to the liver for excretion, keeping the cholesterol from harming the body. For this reason, HDL cholesterol is known as “good” cholesterol. On a blood test, you would want your level of HDL to be high but your level of LDL to below.

17. What effect does fat have on cholesterol?

• Saturated fat appears to raise LDL levels; polyunsaturated fat may help lower cholesterol levels; monounsaturated fat appears to lower LDL and help raise HDL.

18. How is a trans fat made?

Hydrogen is added to the unsaturated fat in vegetable oil, making it saturated and solid.

19. If a teen needs 2,500 calories each day, how many grams of fat does

that allow? If needed, show math.

• 67—97 g of fat (2500 x .25 = 625 calories divided by 9calories per fat gram = about 69 g;

• 2500 x .35 = 875 divided by 9 = about 97 g)

20. Why do some people gain weight when cutting down on fat?

• Some increase the amount of fat-free and low-fat foods they eat and thereby consume more calories.