please solve part b!!!!!!!! The Cori cycle is viewed as 33% efficient, in that 3
ID: 3513786 • Letter: P
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please solve part b!!!!!!!!
The Cori cycle is viewed as 33% efficient, in that 33% of the energy mobilized in the liver is delivered for use in the destination tissue (quite often muscle), and the rest utilized as the 'cost' of this transport. (This low efficiency is one reason we have evolved to perceive a characteristic metabolite of its operation, lactic acid, as sometimes mildly uncomfortable, in cramping or 'the burn' after intense exercise turns muscle anaerobic.) The other pathway we have studied so far that transports things between tissues is the ketone bodies pathway. Here too, we may characterize its efficiency in terms of how much of the total energy is actually delivered. Consider a given amount of fat mobilized by the ketone bodies pathway, and answer the following questions. For purposes of this, consider al energy converted t appropriate pathways of a mammal a. What percentage of the fat's energy is delivered to the destination tissue? To do this you need to figure out i. How much ATP a given fat could potentially produce under 'normal conditions' (use 1 g or 1 mole or whatever you want - of whichever fat you want...) How much ATP is produced in the destination tissue ii. iii. What the energy value is of this ATP in each case. Use physiological values of AG for ATP based on the table to the right. Then calculate the percentage delivered iv. What is the cost of this process (once again- physiological conditions as given)? Thus, calculate the efficiency, on an energy basis (similar to the Cori cycle calculation) Is the rest of this energy used up in the pathway (as it is in Cori), or what else happens to it? Produce another measure of efficiency taking this into account. How do the above measures (a through d) vary for each ketone body compound? b. mM 10 NADH NAD+ ATP ADP Pi c. d. 0.3 e.Explanation / Answer
The human body is remarkably adept at making do with whatever type of food is available. Our ability to survive on a variety of diets has been a vital adaptation for a species that evolved under conditions where food sources were scarce and unpredictable. Imagine if you had to depend on successfully hunting a woolly mammoth or stumbling upon a berry bush for sustenance!
Today, calories are mostly cheap and plentiful—perhaps too much so. Understanding what the basic macronutrients have to offer can help us make better choices when it comes to our own diets.
From the moment a bite of food enters the mouth, each morsel of nutrition within starts to be broken down for use by the body. So begins the process of metabolism, the series of chemical reactions that transform food into components that can be used for the body's basic processes. Proteins, carbohydrates, and fats move along intersecting sets of metabolic pathways that are unique to each major nutrient. Fundamentally—if all three nutrients are abundant in the diet—carbohydrates and fats will be used primarily for energy while proteins provide the raw materials for making hormones, muscle, and other essential biological equipment.
Protein
Proteins in food are broken down into pieces (called amino acids) that are then used to build new proteins with specific functions, such as catalyzing chemical reactions, facilitating communication between different cells, or transporting biological molecules from here to there. When there is a shortage of fats or carbohydrates, proteins can also yield energy.
Fat
Fats typically provide more than half of the body's energy needs. Fat from food is broken down into fatty acids, which can travel in the blood and be captured by hungry cells. Fatty acids that aren't needed right away are packaged in bundles called triglycerides and stored in fat cells, which have unlimited capacity. "We are really good at storing fat," says Judith Wylie-Rosett, EdD, RD, a professor of behavioral and nutritional research at Albert Einstein College of Medicine.
Carbohydrate
Carbohydrates, on the other hand, can only be stored in limited quantities, so the body is eager to use them for energy. "We think of carbs as the [nutrient] that's used first," says Eric Westman, MD, MHS, director of the Lifestyle Medicine Clinic at Duke University Medical Center. "We can only store a day or two of carbs." The carbohydrates in food are digested into small pieces—either glucose or a sugar that is easily converted to glucose—that can be absorbed through the small intestine's walls. After a quick stop in the liver, glucose enters the circulatory system, causing blood glucose levels to rise. The body's cells gobble up this mealtime bounty of glucose more readily than fat, says Wylie-Rosett.
Once the cells have had their fill of glucose, the liver stores some of the excess for distribution between meals should blood glucose levels fall below a certain threshold. If there is leftover glucose beyond what the liver can hold, it can be turned into fat for long-term storage so none is wasted. When carbohydrates are scarce, the body runs mainly on fats. If energy needs exceed those provided by fats in the diet, the body must liquidate some of its fat tissue for energy.
While these fats are a welcome source of energy for most of the body, a few types of cells, such as brain cells, have special needs. These cells could easily run on glucose from the diet, but they can't run on fatty acids directly. So under low-carbohydrate conditions, these finicky cells need the body to make fat-like molecules called ketone bodies. This is why a very-low-carbohydrate diet is sometimes called "ketogenic." (Ketone bodies are also related to a dangerous diabetic complication called ketoacidosis, which can occur if insulin levels are far too low.) Ketone bodies could alone provide enough energy for the parts of the body that can't metabolize fatty acids, but some tissues still require at least some glucose, which isn't normally made from fat. Instead, glucose can be made in the liver and kidneys using protein from elsewhere in the body. But take care: If not enough protein is provided by the diet, the body starts chewing on muscle cells
Another component of 24-h energy expenditure is the energy cost of spontaneous physical activity, which accounts for 8–15% of total daily expenditure.12 Consistent with the cross-sectional observation of a decreased spontaneous physical activity in obese individuals, longitudinal studies in Pima Indians showed that spontaneous physical activity is a familial trait inversely related to weight and fat mass gain at least in men.39 Although it could be argued that spontaneous physical activity during a respiratory chamber study is limited, it was found to be highly correlated with habitual physical activity in free-living conditions.40However, in a prospective study in which free-living physical activity was measured by doubly labeled water in 92 nondiabetic Pima Indians, activity energy expenditure or the level of physical activity was not associated with changes in body weight.35 Levine et al.41 fed 16 sedentary individuals an extra 1000 kcal day1 for 8 weeks and measured free-living activity and changes in body weight. Despite no changes in voluntary physical activity or energy wastage through fecal losses, fat gain varied more than 10-fold among individuals, ranging from 0.36 to 4.23 kg, and was inversely related to the increase in total energy expenditure. Because changes in RMR and thermic effect of food were small, the resistance to weight and fat gain with overfeeding was attributed to changes in spontaneous physical activity ranging from 98 to 692 kcal day1. We recently reviewed the literature on spontaneous physical activity and the control of body weight.42
Low SNS activity
Studies in Caucasians indicate that the activity of the SNS is related to each of the major components of energy expenditure: RMR,43 the thermic effect of food,44 spontaneous physical activity45 and 24-h respiratory quotient.46 Importantly, cross-sectional studies indicate that individuals (Pima Indians) prone to obesity have lower rates of muscle sympathetic activity compared with weight-matched Caucasians.43Consequently, we prospectively studied the role of impaired SNS activity and/or adrenal medullary function in the etiology of human obesity in Pima Indian men. At follow-up, body-weight change was negatively correlated with baseline urinary norepinephrine excretion rate, whereas the changes in waist-to-thigh circumference ratio negatively correlated with baseline epinephrine excretion rate.47 Together, these results show that an impaired SNS activity and a low activity of the adrenal medulla axis are associated with body weight gain and central obesity. Consistently, a low SNS activity was associated with poor weight loss outcomes in obese individuals treated with a dietary restriction intervention.48
Low fat oxidation
As reviewed above, the composition of nutrient intake is an important factor in the development of obesity, and consequently, one expects that the composition of nutrient oxidation also plays a role in its etiology. The nonprotein respiratory quotient (RQ) is an index of the ratio of carbohydrate to fat oxidation, and fasting values of 0.80 after an overnight fast indicate a major reliance on fat oxidation,49 whereas values approaching 1.00 following ingestion of a carbohydrate meal indicate reliance on carbohydrate as the major energy substrate.26,50 Apart from the obvious impact of diet composition, the RQ is also influenced by recent energy balance, sex, adiposity, and importantly family membership, suggesting genetic determinants.50,51
A longitudinal study of Pima Indians showed that a high 24-h RQ predicted weight gain, with low fat oxidizers (90th percentile for respiratory quotient) having a 2.5 times greater risk of gaining 5 kg or more body weight than high fat oxidizers (10th percentile for respiratory quotient).50 This effect was independent of a relatively low or high 24-h metabolic rate. Similar results have been reported in Caucasians.52 Others have shown that postobese volunteers have low rates of fat oxidation,53,54 and those successful at maintaining weight loss have higher fat oxidation rates than those experiencing weight relapse
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