1. Lipid molecules (fats) are used as energy storage in many animals. These mole
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Question
1. Lipid molecules (fats) are used as energy storage in many animals. These molecules have many non-polar covalent bonds (C – C and C – H bonds… making these molecules hydrophobic).
What feature of these bonds makes lipids a good source of energy for cells? (2 points)
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2. Calories are a unit of energy. A gram of fat has 9 calories, so we get a lot of energy from fatty foods. Delicious! A gram of protein only has 4 calories. A gram of sugar also only has 4 calories. When breaking apart the bonds of these different biomolecules, why do we get fewer calories from proteins and carbohydrates than from fats (Hint, look at your answer for #1; 2 points)
Explanation / Answer
Lipids are organic compounds that contain the same elements as carbohydrates: carbon, hydrogen, and oxygen. However, the hydrogen-to-oxygen ratio is always greater than 2:1. More important for biological systems, the carbon-to-hydrogen bonds are nonpolar covalent, which means that lipids are fat soluble and will not dissolve in water.
Fats are large molecules that are composed of three fatty acid molecules bonded to a glycerol molecule. The fatty acid molecule is a long chain of covalently bonded carbon atoms with nonpolar bonds to hydrogen atoms all along the carbon chain with a carboxyl group attached to one end. Because the carbon-hydrogen bonds are nonpolar, the chain is hydrophobic, meaning they are not water soluble. Glycerol is a three-carbon-chain compound that bonds with the fatty acids to create a fat. Typically, each carbon in the glycerol molecule bonds via dehydration synthesis to the first carbon atom from a fatty acid molecule so that the resulting fat molecule appears to have a glycerol head with three fatty acid chains streaming from it. This resulting molecule is called a triglyceride. Because carbon-hydrogen bonds are considered energy rich, fats store a lot of energy per unit. In fact, a gram of fat stores more than twice as much energy as a gram of a polysaccharide such as starch. Fats are lipids that are used by living organisms for stored energy.
A saturated fatty acid has hydrogen atoms bonded to all available carbon atoms. An unsaturated fatty acid has one or more carbon atoms double-bonded to the neighboring carbon atom so that fewer hydrogen atoms are needed to create a stable electron cloud. With fewer hydrogen atoms attached, the molecule is considered unsaturated with hydrogen atoms. So saturated fatty acids have more hydrogen atoms attached than unsaturated fatty acid chains. Through their metabolism, plants generally produce triglycerides that contain unsaturated fatty acids such as peanut oil or olive oil, whereas animals generally produce triglycerides that contain saturated fatty acids which humans sometimes convert into butter and lard.
The carbon-hydrogen bonds Protein, carbohydrates and fats are the three macronutrients that make up all foods consist.
Fats, also called lipids, are our primary source of energy while at rest. Lipids are composed of a molecule of glycerol and one to three fatty acids. Most fats are found with three fatty acids and are called triglycerides.
Proteins are made up of many thousands of smaller units called amino acids. Some amino acids can be made by the body while others have to be eaten in the foods we consume. Proteins are generally not used for energy by the body except under conditions of starvation, or prolonged, strenuous exercise like long distance cycling and running.
Carbohydrates are the body's primary source of energy for most activities. Carbohydrates are found in simple forms, such as fruit or table sugar, or complex forms, like whole wheat breads, rice, or potatoes -- but in all cases they're made up of smaller units. These smaller units are mostly glucose and fructose. The sugar lactose is primarily found in dairy products like milk. All are combinations of carbon, hydrogen, and oxygen in a perfect balance for use in the body. There are other minor sugars found in foods that are important for cellular communication.
A molecule of dietary fat typically consists of several fatty acids Carbohydrate metabolism denotes the various biochemical processes responsible for the formation, breakdown and interconversion of carbohydrates in living organisms.
The most important carbohydrate is glucose, a simple sugar (monosaccharide) that is metabolized by nearly all known organisms. Glucose and other carbohydrates are part of a wide variety of metabolic pathways across species: plants synthesize carbohydrates from carbon dioxide and water by photosynthesis storing the absorbed energy internally, often in the form of starch or lipids. Plant components are consumed by animals and fungi, and used as fuel for cellular respiration. Oxidation of one gram of carbohydrate yields approximately 4 kcal of energy, while the oxidation of one gram of lipids yields about 9 kcal. Energy obtained from metabolism (e.g., oxidation of glucose) is usually stored temporarily within cells in the form of ATP. Organisms capable of aerobic respiration metabolize glucose and oxygen to release energy with carbon dioxide and water as byproducts.
Reason for protein catabolism is so organisms can convert proteins into a form of energy that they can use or store. To reuse their proteins, bacteria or soil microorganisms break down their proteins through protein catabolism into their individual amino acids and are used to form bacterial proteins or oxidized for energy. To convert to energy, once the proteins are broken down, they are typically deaminated.
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