Nutrition C8
Beta-oxidation of fatty acids is an example of a(n) _____ reaction.
catabolic
Which of the following storage sites can yield the greatest amount of energy?
Triglycerides in the adipose tissue Liver glycogen can yield about 300 to 400 kcal. Muscle glycogen can yield about 1200 to 1600 kcal. Triglycerides stored in adipose tissue can yield about 80,000 to 100,000 kcal.
The end product of glycolysis is pyruvate. Complete the following statements to describe what happens to pyruvate.
Under anaerobic conditions, such as intense exercise, pyruvate is converted to lactate. This 3-carbon molecule travels through the blood to the liver, where it can be converted to glucose by the Cori cycle. Under aerobic conditions, pyruvate enters the mitochondrion, where it is converted to acetyl CoA. This 2-carbon molecule goes on to participate in a series of oxidative reactions called the citric acid cycle.
What is/are the source(s) of energy in the homemade high-caliber smoothie?
All of the choices are correct. Nonfat milk Nonfat plain yogurt Berries Nonfat milk and nonfat plain yogurt contain carbohydrates and protein, which can provide energy to the body. Raspberries and blueberries contain carbohydrates, which can also provide energy to the body.
Side effects of caffeine consumption include _________.
All of these choices are correct. anxiety tremors rapid heart rate Caffeine is a stimulant drug because it increases the activity of the nervous system. The drug, however, can cause unpleasant side effects, including anxiety, restlessness, tremors, rapid heart rate, and sleep disturbances.
Complete the following statements to describe how amino acids can be utilized for energy.
Before an amino acid can be metabolized to yield ATP, its nitrogen group must be removed. This process requires the coenzyme form of vitamin B-6. Amino acids that are converted into pyruvate or intermediates of the citric acid cycle are called glucogenic amino acids. Amino acids that are converted into acetyl CoA are called ketogenic amino acids.
Describe how cells use fatty acids for fuel.
Free fatty acids are taken up by cells from the bloodstream. Before they can be metabolized for fuel, fatty acids must be bound to coenzyme A. Activated fatty acids must be transported from the cytosol into the mitochondrion of the cell. The transport protein that shuttles fatty acids across the mitochondrial membrane is carnitine. Next, fatty acids are cleaved into 2-carbon fragments in a process called beta-oxidation. The 2-carbon fragments are converted into acetyl CoA. The 2-carbon fragments that arise from these cleavage reactions can then be oxidized in the citric acid cycle. High-energy electrons released by this series of reactions are taken up by two coenzymes, NAD and FAD. ATP can be generated from the chemical energy stored in the reduced coenzymes (NADH and FADH₂) that are produced by these reactions. This final phase of fatty acid catabolism is the electron transport chain.
Which drink is a healthier source of energy?
High-caliber smoothie The high-caliber smoothie contains natural ingredients; carbohydrates, protein, vitamins, and minerals are present in the smoothie. The carbohydrates and protein will provide energy to the body. Commercial energy drinks may provide a small amount of energy from simple sugars, but those simple sugars can contribute to a blood glucose spike and excessive insulin secretion. Neither caffeine nor B vitamins provide energy.
Which of the following enzymes breaks down the triglycerides stored in adipose tissue to release fatty acids into the bloodstream?
Hormone sensitive lipase Hormone sensitive lipase is the enzyme that hydrolyzes triglycerides in adipose tissue so that fatty acids can be released into the blood, then used for fuel by body cells. Gastric lipase (secreted in the stomach) and pancreatic lipase (secreted into the pancreas) are two enzymes that break down triglycerides in the digestive tract so that fatty acids, monoglycerides, and glycerol may be absorbed. Lipoprotein lipase is the enzyme that hydrolyzes triglycerides in circulating lipoproteins (e.g., chylomicrons and VLDLs), so that fatty acids can be taken up by body cells.
Which of the following is not an effect of consuming caffeine?
Increased energy production Although caffeine increases alertness, the compound does not provide any energy (calories). Simply consuming an energy drink that contains caffeine and other naturally occurring stimulants may reduce feelings of fatigue, but it will not lead to having more energy.
Which of the following are hormones that regulate human metabolism? Check all that apply.
Insulin Epinephrine Thyroid hormone The five key hormones that direct or regulate metabolic activities are insulin, glucagon, cortisol, epinephrine, and thyroid hormone.
Not long after the drinks are consumed, blood sugar levels begin to rise, which stimulates the pancreas to release insulin. Assume the person consuming the commercial energy drink does not need the calories from the beverage for energy. In this situation, what effect would the insulin have on the body?
Insulin will promote glycogen synthesis. Insulin will promote storage of nutrients in the body. The excess calories from the energy drink can be stored as glycogen or in adipose cells.
Which of the following does not describe guarana?
It contains the depressants theobromine and theophylline In addition to caffeine, energy drinks may contain B vitamins and other dietary supplements, including taurine, a derivative of the amino acid cysteine, and guarana, an herbal product. Guarana naturally contains caffeine and two chemically related stimulants, theobromine and theophylline.
During starvation, the body adapts to ensure that cells have access to a variety of fuel sources. Select all of the biochemical pathways that are active during periods of prolonged starvation.
Ketogenesis Lipolysis Proteolysis Gluconeogenesis As the body adapts to starvation, blood glucose and glycogen stores are completed, so triglycerides and proteins are catabolized to maintain a supply of energy-yielding nutrients for the cells. Metabolic pathways that store energy (glycogenesis and lipogenesis) are suppressed.
What is the primary site for the following reaction within the cell?
Mitochondrion Most of the phosphorylation of ADP to produce ATP takes place in the mitochondria of the cell. A relatively small amount of ATP is generated in the cytosol during glycolysis.
Which of the following situations lead to ketosis? Check all that apply.
Poorly controlled diabetes mellitus Very-low-carbohydrate diet Starvation Ketosis is the accumulation of ketone bodies in the blood. Ketogenesis occurs when beta-oxidation of fat outpaces glycolysis. There is an excess of acetyl CoA from beta-oxidation of fatty acids, but not much oxaloacetate, which originates as a by-product of carbohydrate metabolism. As a result, the citric acid cycle slows down and acetyl CoA is converted into ketone bodies. During poorly controlled diabetes, a lack of insulin prevents cells from taking up glucose, so cells must rely heavily of catabolism of fatty acids for fuel. Carbohydrates are available in abundance, but the cells cannot use them due to the lack of insulin. During starvation and low-carbohydrate diets, the supply of dietary carbohydrates is not sufficient to meet the body's need for fuel, so fatty acids are mobilized from adipose tissue. Again, the low availability of pyruvate (from glycolysis) slows down the citric acid cycle, and the abundance of acetyl CoA leads to ketogenesis. Ketogenic diets, which are low in carbohydrates, are sometimes used as a treatment for epilepsy, but epilepsy itself does not cause ketosis.
Which of these is/are the primary site(s) of glycogen storage? Check all that apply.
Skeletal muscle Liver Skeletal muscles normally store about 300 to 340 grams of glycogen. The liver normally stores about 70 to 100 grams of glycogen. Minor amounts (5 to 10 grams) of glycogen are stored in other tissues, such as cardiac muscle.
What is/are the source(s) of energy in the commercial energy drink?
Sucrose The only nutrients that provide energy (ATP) are carbohydrates (e.g., sucrose), proteins, and lipids. Alcohol provides energy, but is not a nutrient. Caffeine is a stimulant but does not provide energy to the body. B vitamins serve as cofactors in energy metabolism but do not provide energy.
Alcohol requires no digestion; it is absorbed intact from the stomach and small intestine.
TRUE The presence of food in the GI tract may delay absorption of alcohol, but no digestion of alcohol is required before it can be absorbed.
Describe the three phases of carbohydrate catabolism.
The first step of carbohydrate catabolism is glycolysis. This process converts the 6-carbon glucose molecule into two 3-carbon molecules of pyruvate. This series of chemical reactions takes place in the cytosol. The next step of carbohydrate catabolism takes place in the mitochondrion. With the help of coenzyme A, the 3-carbon pyruvate molecules are converted to acetyl CoA. This is the entry point for the citric acid cycle, a 6-step process that harvests the chemical energy stored in carbohydrates in the form of high-energy electrons. During the last step of carbohydrate catabolism, the high-energy electrons liberated during previous steps are shuttled to the electron transport chain, which is a series of enzymes embedded in the membrane of the mitochondrion. The chemical energy is used to generate ATP from ADP and inorganic phosphate.
The high-energy phosphate compound that cells use to perform work is _______.
adenosine triphosphate (ATP) The high-energy phosphate compound that powers human cells is adenosine triphosphate (ATP). Adenosine diphosphate (ADP) is formed when the high-energy bond between phosphate groups in ATP is broken to release energy. Nicotinamide adenine dinucleotide phosphate (NADP) is a coenzyme form of niacin that is required for many biosynthetic reactions, such as fatty acid synthesis. Pyridoxal phosphate (PLP) is the coenzyme form of vitamin B-6 that is especially important for amino acid metabolism.
Energy input in the form of ATP is required for ______ reactions.
anabolic
Gluconeogenesis is an example of a(n) _____ reaction.
anabolic
Metabolic pathways that build larger molecules from smaller ones are ____ reactions.
anabolic
The most common ingredient in energy drinks is _________.
caffeine Most energy drinks contain caffeine as a major ingredient. Energy drinks may contain sucrose and other simple carbohydrates as well as taurine. The B vitamins niacin, B-6, B-12, and pantothenic acid are often included in energy drinks, but folic acid is rarely included.
Human cells extract energy from the chemical breakdown of _______. Select all that apply.
carbohydrates fats proteins Human cells can use the chemical energy stored in the bonds of carbohydrates, fats, proteins, and alcohol. Vitamins and minerals serve as cofactors or coenzymes for the chemical reactions that release energy from carbohydrates, fats, proteins, and alcohol; but do not yield any energy themselves.
Chemical and heat energy are released as a result of _____ reactions.
catabolic
Metabolic pathways that break down large molecules into smaller ones are _____ reactions.
catabolic
To maintain a steady supply of glucose to body cells, the process of _______ frees glucose from its storage form in the muscle and liver.
glycogenolysis Glycogen can be broken down to yield glucose during the process of glycogenolysis.
Typically, women have lower alcohol tolerance than men due to _______. Check all that apply.
lower body water content lower production of gastric alcohol dehydrogenase Compared to men, women tend to reach higher blood alcohol content from a given quantity of alcohol. First, production of gastric alcohol dehydrogenase is lower among women, which means that the liver bears the full burden of alcohol metabolism. Women are typically smaller than men. The lower amount of lean body mass means that women have less body water content in which alcohol can be diluted. The size of the liver is also smaller, which means less alcohol can be metabolized per hour. Women tend to have a higher body fat content than men, which means that, even if a woman has the same body weight as a man, the woman has lower body water content. Kidney function is not gender-dependent.
The net yield of oxidation of 1 glucose molecule via glycolysis is ______ ATP. Enter a whole number.
Glycolysis requires the input of 2 ATP, but generates 4 ATP. Thus, the net energy yield of glycolysis is 2 ATP. 2
Complete the following statements to describe how the body handles glucose that is consumed in excess of immediate needs.
When carbohydrate consumption exceeds the body's immediate needs for energy, glycogenesis increases. Glycogen storage space in the liver and muscles is limited. When glycogen stores are full, use of glucose for energy increases and oxidation of fat for energy decreases. Overall, when carbohydrate intake is excessive, lipogenesis increases.
