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Lipids Review

Lipids Review. 1. List four substances that are lipids. Triglycerides (fats & oils). Lipids. Phospholipids (a component of cell membranes) . Waxes (waxy coating on leaves, candle wax, bees wax). Cholesterol and Steroids. 2. What do all lipids have in common?.

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Lipids Review

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  1. Lipids Review

  2. 1. List four substances that are lipids. Triglycerides (fats & oils) Lipids Phospholipids (a component of cell membranes) Waxes (waxy coating on leaves, candle wax, bees wax) Cholesterol and Steroids

  3. 2. What do all lipids have in common? Lipids are hydrophobic, which means that they repel water. Lipids In other words… Lipids are nonpolar, which means that they do not dissolve in water.

  4. 3. What is the structure of a triglyceride? A triglyceride consists of three fatty acid tails bonded to a glycerol molecule Lipids More specifically it looks like this: Fatty acid tail Glycerol Fatty acid tail Hydrogen atom Carbon atom Fatty acid tail Oxygen atom

  5. 4. What molecule is released whenever a fatty-acid tail bonds to glycerol? (Click once and watch the animation) Lipids Fatty acid tail Fatty acid tail Fatty acid tail Glycerol As you can see, a water molecule is released for each bond formed.

  6. 5. What is the difference between saturated and unsaturated fatty-acid tails? Saturated fatty-acids have the maximum number of hydrogen atoms that each carbon in the chain can hold. Lipids Hydrogen atom Carbon atom Oxygen atom

  7. 5. What is the difference between saturated and unsaturated fatty-acid tails? For example, count the number of white hydrogen atoms in the middle fatty acid chain. Lipids You should have counted 23. That is the maximum number that chain can hold. Hydrogen atom Carbon atom Oxygen atom

  8. 5. What is the difference between saturated and unsaturated fatty-acid tails? Now count the number of hydrogen atoms in the top chain. Lipids You should have counted 21. That is two atoms less than the middle chain. Can you figure out why? Hydrogen atom Carbon atom Oxygen atom

  9. 5. What is the difference between saturated and unsaturated fatty-acid tails? If you thought it had something to do with the double bond (see circled area) you are correct. When a pair of carbon atoms form a double bond, two hydrogen atoms are released. The chain is now said to be unsaturated. Lipids Hydrogen atom Carbon atom Oxygen atom

  10. 6. How are fatty acids named? The top fatty acid chain has 12 carbon atoms and 1 double bond. It is also unsaturated, so its referred to as mono-unsaturated 12:1 Lipids Notice also that the double bond starts at the third carbon from the end of the chain. In addition, the carbon atom at the end of a fatty acid is called the omega (Ω)carbon Ω Therefore, the double bond position is referred to as omega-3 3 Hydrogen atom Carbon atom Oxygen atom

  11. 7. Notice that both the top chain and bottom chain contain an omega-3 double bond. However, the top chain has a kink in it but not the bottom chain. What do you think causes the kink? Lipids When the hydrogen atoms end up on the same side of the double bond they repel each other, causing a kink in the chain. This is known as a cis configuration. Ω 3 Hydrogen atom Carbon atom Oxygen atom 3 Ω

  12. 7. Notice that both the top chain and bottom chain contain an omega-3 double bond. However, the top chain has a kink in it but not the bottom chain. What do you think causes the kink? Lipids When the hydrogen atoms end up on opposite sides of the double bond the shape of the chain remains unchanged (see circled area). This is known as a trans configuration. Ω Hydrogen atom Carbon atom Oxygen atom 3 Ω

  13. 8. So how would you name each of the fatty-acid tails? Lipids The top chain is a monounsaturated 12:1 omega-3 cis fat The middle chain is a saturated 12:0 fat Ω 3 3 Ω The bottom chain is a monounsaturated 12:1 omega-3 trans fat

  14. 9. What would you call the top chain of this triglyceride? Lipids The top chain is a polyunsaturated 12:2 omega-3 cis, -6 trans fat Ω 3 6 Hydrogen atom Carbon atom Oxygen atom Ω 3

  15. 10. How does a phospholipid differ from a triglyceride? Lipids A triglyceride has three fatty-acid chains (remember, tri means 3). Fatty acid tail Fatty acid tail A phospholipid has two fatty-acid chains. The third chain has been replace by a PO4 (phosphate) group. PO4 Glycerol Glycerol Fatty acid tail Fatty acid tail Fatty acid tail

  16. 11. What is the simplest way to draw triglycerides and phospholipids? Lipids Triglycerides are usually drawn like this. In phospholipids, the phosphate group usually has another molecule attached to it. Therefore the phosphate head is drawn as a large circle.

  17. 12. Are triglycerides and phospholipids polar or nonpolar? Lipids Both molecules have a polar and nonpolar regions Polar heads which are hydrophilic (water loving) Nonpolar tails which are hydrophobic (water fearing)

  18. 13. Where are phospholipids found in the body? Phospholipids are found in cellular membranes, of which they are a major component. Lipids

  19. 14. How do lipids behave when placed in water? Both molecules will float in water as shown below. Lipids The nonpolar tails are repelled by water… Note: Lipid molecules are a million times smaller than shown. …while the polar heads are attracted to water.

  20. 15. What is the most common steroid in the body? Lipids Cholesterol

  21. 16. Why is cholesterol biological important? a. The body uses cholesterol as a starting point to make other steroids, like the ones shown below. Lipids For example: progesterone, estradiol, and testosterone are sex hormones. Asldosterone regulates blood pressure. Cholic acid is involved in digestion. Cortisol is a stress hormone.

  22. 16. Why is cholesterol biological important? b. Cholesterol is also found in the lipid bilayer of cell membranes. It regulates membrane permeability and fluidity over a wide range of temperatures. Lipids Cholesterol molecule

  23. 17. How do organisms use lipids? Energy storage: Animals store lipids in fat cells as long-term energy storage. Lipids Protection: The waxy coating on plant leaves help repel water.

  24. 17. How do organisms use lipids? c. Buoyancy for marine animals: lipids are less dense than water helping animals float. Lipids d. Insulation: A layer of fat beneath the skin cuts down on heat loss.

  25. 17. How do organisms use lipids? Production of water: Fatty acids produce a lot of water when they are used as fuel during respiration. Lipids Camel humps are made of fat Construction: Bees use wax (beeswax) to make honeycombs.

  26. 18. Which provides more energy per gram, fats or carbohydrates? Lipids Fats will give off more energy (over twice as much) than will carbohydrates. Generally, fats provide about 9 Calories per gram and carbohydrates provide about 4 Calories per gram.

  27. 19. Which provides the quickest release of energy in the body, fats or carbohydrates? Lipids Small carbohydrates like table sugar provide energy very quickly. Complex carbohydrates like starches and glycogen release energy more steadily but at a slower pace. Fats make energy available at a much slower pace than carbohydrates.

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