Lipids Quiz

PDF page 111: Lipids also are sources of energy that power cellular processes. Like carbohydrates, lipids are composed of carbon, hydrogen, and oxygen, but these atoms are arranged differently. Most lipids are nonpolar and hydrophobic. Major types include fats and oils, waxes, phospholipids, and steroids. A typical fat consists of three fatty acids bonded to one molecule of glycerol, forming triglycerides or triacylglycerols. The fatty acids may be saturated or unsaturated, depending on the presence or absence of double bonds in the hydrocarbon chain; a saturated fatty acid has the maximum number of hydrogen atoms bonded to carbon and, thus, only single bonds. In general, fats that are liquid at room temperature (e.g., canola oil) tend to be more unsaturated than fats that are solid at room temperature. In the food industry, oils are artificially hydrogenated to make them chemically more appropriate for use in processed foods. During this hydrogenation process, double bonds in the cis- conformation in the hydrocarbon chain may be converted to double bonds in the transconformation; unfortunately, trans fats have been shown to contribute to heart disease. Phospholipids are a special type of lipid associated with cell membranes and typically have a glycerol (or sphingosine) backbone to which two fatty acid chains and a phosphate-containing group are attached. As a result, phospholipids are considered amphipathic because they have both hydrophobic and hydrophilic components. (In Chapters 4 and 5 we will explore in more detail how the amphipathic nature of phospholipids in plasma cell membranes helps regulate the passage of substances into and out of the cell.) Although the molecular structures of steroids differ from that of triglycerides and phospholipids, steroids are classified as lipids based on their hydrophobic properties. Cholesterol is a type of steroid in animal cells’ plasma membrane. Cholesterol is also the precursor of steroid hormones such as testosterone. Information presented and the examples highlighted in the section, support concepts outlined in Big Idea 4 of the

PDF page 112: Lipids include a diverse group of compounds that are largely nonpolar in nature. This is because they are hydrocarbons that include mostly nonpolar carbon–carbon or carbon–hydrogen bonds. Non-polar molecules are hydrophobic (“water fearing”), or insoluble in water. Lipids perform many different functions in a cell. Cells store energy for long-term use in the form of fats. Lipids also provide insulation from the environment for plants and animals (Figure 3.13). For example, their water-repellant hydrophobic nature can help keep aquatic birds and mammals dry by forming a protective layer over fur or feathers. Lipids are also the building blocks of many hormones and an important constituent of all cellular membranes. Lipids include fats, waxes, phospholipids, and steroids.

PDF page 111: Lipids also are sources of energy that power cellular processes. Like carbohydrates, lipids are composed of carbon, hydrogen, and oxygen, but these atoms are arranged differently. Most lipids are nonpolar and hydrophobic. Major types include fats and oils, waxes, phospholipids, and steroids. A typical fat consists of three fatty acids bonded to one molecule of glycerol, forming triglycerides or triacylglycerols. The fatty acids may be saturated or unsaturated, depending on the presence or absence of double bonds in the hydrocarbon chain; a saturated fatty acid has the maximum number of hydrogen atoms bonded to carbon and, thus, only single bonds. In general, fats that are liquid at room temperature (e.g., canola oil) tend to be more unsaturated than fats that are solid at room temperature. In the food industry, oils are artificially hydrogenated to make them chemically more appropriate for use in processed foods. During this hydrogenation process, double bonds in the cis- conformation in the hydrocarbon chain may be converted to double bonds in the transconformation; unfortunately, trans fats have been shown to contribute to heart disease. Phospholipids are a special type of lipid associated with cell membranes and typically have a glycerol (or sphingosine) backbone to which two fatty acid chains and a phosphate-containing group are attached. As a result, phospholipids are considered amphipathic because they have both hydrophobic and hydrophilic components. (In Chapters 4 and 5 we will explore in more detail how the amphipathic nature of phospholipids in plasma cell membranes helps regulate the passage of substances into and out of the cell.) Although the molecular structures of steroids differ from that of triglycerides and phospholipids, steroids are classified as lipids based on their hydrophobic properties. Cholesterol is a type of steroid in animal cells’ plasma membrane. Cholesterol is also the precursor of steroid hormones such as testosterone. Information presented and the examples highlighted in the section, support concepts outlined in Big Idea 4 of the

PDF page 113: A fat molecule consists of two main components—glycerol and fatty acids. Glycerol is an organic compound (alcohol) with three carbons, five hydrogens, and three hydroxyl (OH) groups. Fatty acids have a long chain of hydrocarbons to which a carboxyl group is attached, hence the name “fatty acid.” The number of carbons in the fatty acid may range from 4 to 36; most common are those containing 12–18 carbons. In a fat molecule, the fatty acids are attached to each of the three carbons of the glycerol molecule with an ester bond through an oxygen atom (Figure 3.14).

PDF page 111: Lipids also are sources of energy that power cellular processes. Like carbohydrates, lipids are composed of carbon, hydrogen, and oxygen, but these atoms are arranged differently. Most lipids are nonpolar and hydrophobic. Major types include fats and oils, waxes, phospholipids, and steroids. A typical fat consists of three fatty acids bonded to one molecule of glycerol, forming triglycerides or triacylglycerols. The fatty acids may be saturated or unsaturated, depending on the presence or absence of double bonds in the hydrocarbon chain; a saturated fatty acid has the maximum number of hydrogen atoms bonded to carbon and, thus, only single bonds. In general, fats that are liquid at room temperature (e.g., canola oil) tend to be more unsaturated than fats that are solid at room temperature. In the food industry, oils are artificially hydrogenated to make them chemically more appropriate for use in processed foods. During this hydrogenation process, double bonds in the cis- conformation in the hydrocarbon chain may be converted to double bonds in the transconformation; unfortunately, trans fats have been shown to contribute to heart disease. Phospholipids are a special type of lipid associated with cell membranes and typically have a glycerol (or sphingosine) backbone to which two fatty acid chains and a phosphate-containing group are attached. As a result, phospholipids are considered amphipathic because they have both hydrophobic and hydrophilic components. (In Chapters 4 and 5 we will explore in more detail how the amphipathic nature of phospholipids in plasma cell membranes helps regulate the passage of substances into and out of the cell.) Although the molecular structures of steroids differ from that of triglycerides and phospholipids, steroids are classified as lipids based on their hydrophobic properties. Cholesterol is a type of steroid in animal cells’ plasma membrane. Cholesterol is also the precursor of steroid hormones such as testosterone. Information presented and the examples highlighted in the section, support concepts outlined in Big Idea 4 of the

PDF page 114: During this ester bond formation, three water molecules are released. The three fatty acids in the triacylglycerol may be similar or dissimilar. Fats are also called triacylglycerols or triglycerides because of their chemical structure. Some fatty acids have common names that specify their origin. For example, palmitic acid, a saturated fatty acid, is derived from the palm tree. Arachidic acid is derived from Arachis hypogea, the scientific name for groundnuts or peanuts. Fatty acids may be saturated or unsaturated. In a fatty acid chain, if there are only single bonds between neighboring carbons in the hydrocarbon chain, the fatty acid is said to be saturated. Saturated fatty acids are saturated with hydrogen; in other words, the number of hydrogen atoms attached to the carbon skeleton is maximized. Stearic acid is an example of a saturated fatty acid (Figure 3.15)

PDF page 111: Lipids also are sources of energy that power cellular processes. Like carbohydrates, lipids are composed of carbon, hydrogen, and oxygen, but these atoms are arranged differently. Most lipids are nonpolar and hydrophobic. Major types include fats and oils, waxes, phospholipids, and steroids. A typical fat consists of three fatty acids bonded to one molecule of glycerol, forming triglycerides or triacylglycerols. The fatty acids may be saturated or unsaturated, depending on the presence or absence of double bonds in the hydrocarbon chain; a saturated fatty acid has the maximum number of hydrogen atoms bonded to carbon and, thus, only single bonds. In general, fats that are liquid at room temperature (e.g., canola oil) tend to be more unsaturated than fats that are solid at room temperature. In the food industry, oils are artificially hydrogenated to make them chemically more appropriate for use in processed foods. During this hydrogenation process, double bonds in the cis- conformation in the hydrocarbon chain may be converted to double bonds in the transconformation; unfortunately, trans fats have been shown to contribute to heart disease. Phospholipids are a special type of lipid associated with cell membranes and typically have a glycerol (or sphingosine) backbone to which two fatty acid chains and a phosphate-containing group are attached. As a result, phospholipids are considered amphipathic because they have both hydrophobic and hydrophilic components. (In Chapters 4 and 5 we will explore in more detail how the amphipathic nature of phospholipids in plasma cell membranes helps regulate the passage of substances into and out of the cell.) Although the molecular structures of steroids differ from that of triglycerides and phospholipids, steroids are classified as lipids based on their hydrophobic properties. Cholesterol is a type of steroid in animal cells’ plasma membrane. Cholesterol is also the precursor of steroid hormones such as testosterone. Information presented and the examples highlighted in the section, support concepts outlined in Big Idea 4 of the

PDF page 114: During this ester bond formation, three water molecules are released. The three fatty acids in the triacylglycerol may be similar or dissimilar. Fats are also called triacylglycerols or triglycerides because of their chemical structure. Some fatty acids have common names that specify their origin. For example, palmitic acid, a saturated fatty acid, is derived from the palm tree. Arachidic acid is derived from Arachis hypogea, the scientific name for groundnuts or peanuts. Fatty acids may be saturated or unsaturated. In a fatty acid chain, if there are only single bonds between neighboring carbons in the hydrocarbon chain, the fatty acid is said to be saturated. Saturated fatty acids are saturated with hydrogen; in other words, the number of hydrogen atoms attached to the carbon skeleton is maximized. Stearic acid is an example of a saturated fatty acid (Figure 3.15)

PDF page 115: When the hydrocarbon chain contains a double bond, the fatty acid is said to be unsaturated. Oleic acid is an example of an unsaturated fatty acid (Figure 3.16).

PDF page 111: Lipids also are sources of energy that power cellular processes. Like carbohydrates, lipids are composed of carbon, hydrogen, and oxygen, but these atoms are arranged differently. Most lipids are nonpolar and hydrophobic. Major types include fats and oils, waxes, phospholipids, and steroids. A typical fat consists of three fatty acids bonded to one molecule of glycerol, forming triglycerides or triacylglycerols. The fatty acids may be saturated or unsaturated, depending on the presence or absence of double bonds in the hydrocarbon chain; a saturated fatty acid has the maximum number of hydrogen atoms bonded to carbon and, thus, only single bonds. In general, fats that are liquid at room temperature (e.g., canola oil) tend to be more unsaturated than fats that are solid at room temperature. In the food industry, oils are artificially hydrogenated to make them chemically more appropriate for use in processed foods. During this hydrogenation process, double bonds in the cis- conformation in the hydrocarbon chain may be converted to double bonds in the transconformation; unfortunately, trans fats have been shown to contribute to heart disease. Phospholipids are a special type of lipid associated with cell membranes and typically have a glycerol (or sphingosine) backbone to which two fatty acid chains and a phosphate-containing group are attached. As a result, phospholipids are considered amphipathic because they have both hydrophobic and hydrophilic components. (In Chapters 4 and 5 we will explore in more detail how the amphipathic nature of phospholipids in plasma cell membranes helps regulate the passage of substances into and out of the cell.) Although the molecular structures of steroids differ from that of triglycerides and phospholipids, steroids are classified as lipids based on their hydrophobic properties. Cholesterol is a type of steroid in animal cells’ plasma membrane. Cholesterol is also the precursor of steroid hormones such as testosterone. Information presented and the examples highlighted in the section, support concepts outlined in Big Idea 4 of the

PDF page 115: Most unsaturated fats are liquid at room temperature and are called oils. If there is one double bond in the molecule, then it is known as a monounsaturated fat (e.g., olive oil), and if there is more than one double bond, then it is known as a polyunsaturated fat (e.g., canola oil). When a fatty acid has no double bonds, it is known as a saturated fatty acid because no more hydrogen may be added to the carbon atoms of the chain. A fat may contain similar or different fatty acids attached to glycerol. Long straight fatty acids with single bonds tend to get packed tightly and are solid at room temperature. Animal fats with stearic acid and palmitic acid (common in meat) and the fat with butyric acid (common in butter) are examples of saturated fats. Mammals store fats in specialized cells called adipocytes, where globules of fat occupy most of the cell’s volume. In plants, fat or oil is stored in many seeds and is used as a source of energy during seedling development. Unsaturated fats or oils are usually of plant origin and contain cis unsaturated fatty acids. Cis and trans indicate the configuration of the molecule around the double bond. If hydrogens are present in the same plane, it is referred to as a cis fat; if the hydrogen atoms are on two different planes, it is referred to as a trans fat. The cis double bond causes a bend or a “kink” that prevents the fatty acids from packing tightly, keeping them liquid at room temperature (Figure 3.17). Olive oil, corn oil, canola oil, and cod liver oil are examples of unsaturated fats. Unsaturated fats help to lower blood cholesterol levels whereas saturated fats contribute to plaque formation in the arteries.

PDF page 114: Three molecules of water are released in the process.

PDF page 114: During this ester bond formation, three water molecules are released. The three fatty acids in the triacylglycerol may be similar or dissimilar. Fats are also called triacylglycerols or triglycerides because of their chemical structure. Some fatty acids have common names that specify their origin. For example, palmitic acid, a saturated fatty acid, is derived from the palm tree. Arachidic acid is derived from Arachis hypogea, the scientific name for groundnuts or peanuts. Fatty acids may be saturated or unsaturated. In a fatty acid chain, if there are only single bonds between neighboring carbons in the hydrocarbon chain, the fatty acid is said to be saturated. Saturated fatty acids are saturated with hydrogen; in other words, the number of hydrogen atoms attached to the carbon skeleton is maximized. Stearic acid is an example of a saturated fatty acid (Figure 3.15)

PDF page 113: A fat molecule consists of two main components—glycerol and fatty acids. Glycerol is an organic compound (alcohol) with three carbons, five hydrogens, and three hydroxyl (OH) groups. Fatty acids have a long chain of hydrocarbons to which a carboxyl group is attached, hence the name “fatty acid.” The number of carbons in the fatty acid may range from 4 to 36; most common are those containing 12–18 carbons. In a fat molecule, the fatty acids are attached to each of the three carbons of the glycerol molecule with an ester bond through an oxygen atom (Figure 3.14).

PDF page 113: A fat molecule consists of two main components—glycerol and fatty acids. Glycerol is an organic compound (alcohol) with three carbons, five hydrogens, and three hydroxyl (OH) groups. Fatty acids have a long chain of hydrocarbons to which a carboxyl group is attached, hence the name “fatty acid.” The number of carbons in the fatty acid may range from 4 to 36; most common are those containing 12–18 carbons. In a fat molecule, the fatty acids are attached to each of the three carbons of the glycerol molecule with an ester bond through an oxygen atom (Figure 3.14).

PDF page 114: During this ester bond formation, three water molecules are released. The three fatty acids in the triacylglycerol may be similar or dissimilar. Fats are also called triacylglycerols or triglycerides because of their chemical structure. Some fatty acids have common names that specify their origin. For example, palmitic acid, a saturated fatty acid, is derived from the palm tree. Arachidic acid is derived from Arachis hypogea, the scientific name for groundnuts or peanuts. Fatty acids may be saturated or unsaturated. In a fatty acid chain, if there are only single bonds between neighboring carbons in the hydrocarbon chain, the fatty acid is said to be saturated. Saturated fatty acids are saturated with hydrogen; in other words, the number of hydrogen atoms attached to the carbon skeleton is maximized. Stearic acid is an example of a saturated fatty acid (Figure 3.15)

PDF page 115: Most unsaturated fats are liquid at room temperature and are called oils. If there is one double bond in the molecule, then it is known as a monounsaturated fat (e.g., olive oil), and if there is more than one double bond, then it is known as a polyunsaturated fat (e.g., canola oil). When a fatty acid has no double bonds, it is known as a saturated fatty acid because no more hydrogen may be added to the carbon atoms of the chain. A fat may contain similar or different fatty acids attached to glycerol. Long straight fatty acids with single bonds tend to get packed tightly and are solid at room temperature. Animal fats with stearic acid and palmitic acid (common in meat) and the fat with butyric acid (common in butter) are examples of saturated fats. Mammals store fats in specialized cells called adipocytes, where globules of fat occupy most of the cell’s volume. In plants, fat or oil is stored in many seeds and is used as a source of energy during seedling development. Unsaturated fats or oils are usually of plant origin and contain cis unsaturated fatty acids. Cis and trans indicate the configuration of the molecule around the double bond. If hydrogens are present in the same plane, it is referred to as a cis fat; if the hydrogen atoms are on two different planes, it is referred to as a trans fat. The cis double bond causes a bend or a “kink” that prevents the fatty acids from packing tightly, keeping them liquid at room temperature (Figure 3.17). Olive oil, corn oil, canola oil, and cod liver oil are examples of unsaturated fats. Unsaturated fats help to lower blood cholesterol levels whereas saturated fats contribute to plaque formation in the arteries.

PDF page 115: Most unsaturated fats are liquid at room temperature and are called oils. If there is one double bond in the molecule, then it is known as a monounsaturated fat (e.g., olive oil), and if there is more than one double bond, then it is known as a polyunsaturated fat (e.g., canola oil). When a fatty acid has no double bonds, it is known as a saturated fatty acid because no more hydrogen may be added to the carbon atoms of the chain. A fat may contain similar or different fatty acids attached to glycerol. Long straight fatty acids with single bonds tend to get packed tightly and are solid at room temperature. Animal fats with stearic acid and palmitic acid (common in meat) and the fat with butyric acid (common in butter) are examples of saturated fats. Mammals store fats in specialized cells called adipocytes, where globules of fat occupy most of the cell’s volume. In plants, fat or oil is stored in many seeds and is used as a source of energy during seedling development. Unsaturated fats or oils are usually of plant origin and contain cis unsaturated fatty acids. Cis and trans indicate the configuration of the molecule around the double bond. If hydrogens are present in the same plane, it is referred to as a cis fat; if the hydrogen atoms are on two different planes, it is referred to as a trans fat. The cis double bond causes a bend or a “kink” that prevents the fatty acids from packing tightly, keeping them liquid at room temperature (Figure 3.17). Olive oil, corn oil, canola oil, and cod liver oil are examples of unsaturated fats. Unsaturated fats help to lower blood cholesterol levels whereas saturated fats contribute to plaque formation in the arteries.

PDF page 115: Most unsaturated fats are liquid at room temperature and are called oils. If there is one double bond in the molecule, then it is known as a monounsaturated fat (e.g., olive oil), and if there is more than one double bond, then it is known as a polyunsaturated fat (e.g., canola oil). When a fatty acid has no double bonds, it is known as a saturated fatty acid because no more hydrogen may be added to the carbon atoms of the chain. A fat may contain similar or different fatty acids attached to glycerol. Long straight fatty acids with single bonds tend to get packed tightly and are solid at room temperature. Animal fats with stearic acid and palmitic acid (common in meat) and the fat with butyric acid (common in butter) are examples of saturated fats. Mammals store fats in specialized cells called adipocytes, where globules of fat occupy most of the cell’s volume. In plants, fat or oil is stored in many seeds and is used as a source of energy during seedling development. Unsaturated fats or oils are usually of plant origin and contain cis unsaturated fatty acids. Cis and trans indicate the configuration of the molecule around the double bond. If hydrogens are present in the same plane, it is referred to as a cis fat; if the hydrogen atoms are on two different planes, it is referred to as a trans fat. The cis double bond causes a bend or a “kink” that prevents the fatty acids from packing tightly, keeping them liquid at room temperature (Figure 3.17). Olive oil, corn oil, canola oil, and cod liver oil are examples of unsaturated fats. Unsaturated fats help to lower blood cholesterol levels whereas saturated fats contribute to plaque formation in the arteries.

PDF page 116: have one or more double bonds. Each double bond may be in a cis or trans configuration. In the cis configuration, both hydrogens are on the same side of the hydrocarbon chain. In the trans configuration, the hydrogens are on opposite sides. A cis double bond causes a kink in the chain. Trans Fats In the food industry, oils are artificially hydrogenated to make them semi-solid and of a consistency desirable for many processed food products. Simply speaking, hydrogen gas is bubbled through oils to solidify them. During this hydrogenation process, double bonds of the cis- conformation in the hydrocarbon chain may be converted to double bonds in the transconformation. Margarine, some types of peanut butter, and shortening are examples of artificially hydrogenated trans fats. Recent studies have shown that an increase in trans fats in the human diet may lead to an increase in levels of low-density lipoproteins (LDL), or “bad” cholesterol, which in turn may lead to plaque deposition in the arteries, resulting in heart disease. Many fast food restaurants have recently banned the use of trans fats, and food labels are required to display the trans fat content. Omega Fatty Acids Essential fatty acids are fatty acids required but not synthesized by the human body. Consequently, they have to be supplemented through ingestion via the diet. Omega-3 fatty acids (like that shown in Figure 3.18) fall into this category and are one of only two known for humans (the other being omega-6 fatty acid). These are polyunsaturated fatty acids and are called omega-3 because the third carbon from the end of the hydrocarbon chain is connected to its neighboring carbon by a double bond.