Use of Calories

00:01 So how do we use all of these different calories, especially the ones for basal metabolic rate.

00:07 You need to know where the majority of calories go to.

00:10 So a quick graphic here to help us with that.

00:14 First of all our brain, again we have numbers on here.

00:19 You really need to consider the relativity.

00:21 So which organ uses the most calories? Right, in our basal metabolic rate, we consider the liver, which maybe surprising.

00:32 But the liver uses almost the majority of our calories, but it does an awful lot of stuff.

00:37 It's always active, it's always working for us.

00:40 As well as our brain, so that also has a fairly high caloric usage.

00:46 And then the heart and kidneys are pretty active in using calories.

00:52 And then skeletal muscle, well of course we're using the skeletal muscle to stand up and move around at all times.

00:58 And so it is going to use surprisingly just about as much as the brain.

01:04 So the brain really does have a high demand on our caloric intake.

01:10 All the other organs fit in the other slices of the pie.

01:12 So don't go memorizing the numbers, understand the major users of our basal metabolic rate, the calories attributed to that.

01:24 Brain, liver, skeletal muscle, heart and kidney, Relative proportions are good enough.

01:29 Because again, sources will vary on the specific percentages.

01:34 So any calories that we consumed above and beyond, are basal metabolic needs pictured here, are going to be stored, right.

01:43 And we generally store them as fat.

01:46 And they can become an issue if we have an imbalance in the intake and output of those calories.

01:56 We need to consider for your exam, what calories come from? You are familiar with the major macromolecules, carbohydrates, proteins, fats.

02:07 Those are our sustenance and then of course alcohol is an additional consideration for us when we're considering nutrition.

02:16 You can see the USDA's recommendations of portion sizes.

02:22 We moved from the pyramid to this full plate concept, with all the different proportions in various places.

02:32 There are different arguments as to what are the ideal proportions of proteins, carbohydrates and fats.

02:38 But for the purposes of your exam, the standard here is probably going to be what they hit on most heavily.

02:45 So keep these numbers in mind, 4 calories and 4 calories.

02:50 Sometimes you'll see carbohydrates noted as 4.5.

02:54 Seems from more sources 4 is good enough.

02:58 Alcohol 7 calories per gram, and fat having the most calories per gram because it is an excellent calorie storage spot.

03:07 So, what you will also want to do is recall where each of the different fuels are utilized in cellular respiration or metabolism.

03:19 And I'm certain that you've spent plenty of time examining those between anatomy and physiology, between cell and molecular biology and in biochemistry, for certain.

03:33 You probably know many of the intermediates along the pathway.

03:37 And what you need to remember in this census of nutrition is where each of these sources enter into the respiratory cycle.

03:47 So is it utilized in glycolysis? Is it utilized in the Krebs cycle? And where are the intermediaries coming into there.

03:56 And again that has been covered in the cellular respiration lectures.

04:00 So keep those pathways in mind.

04:06 The one that we may have not spent as much time in is alcohol metabolism.

04:12 Alcohol metabolism is a particularly hot topic in the multi-disciplinary area of nutrition for the exams.

04:21 I think you've seen the pathway before.

04:23 I want to alert you to two key enzymes, alcohol dehydrogenase, which is involved in conversion of ethanol and some other alcohols to acetaldehyde.

04:34 And then acetaldehyde dehydrogenase taking more hydrogens off.

04:39 And the formation of acetate which can easily enter into the Krebs or TCA cycle, so that it can be metabolized.

04:48 Acetate is harmless.

04:50 Acetaldehyde on the other hand is another story.

04:54 It turns out to be fairly toxic.

04:57 A couple of drugs to consider, there is Formepizole.

05:05 And that is involved in treatment of alcohol poisoning.

05:10 So ethylene glycol or methanol poisoning.

05:13 It's administered to deactivate alcohol dehydrogenase.

05:18 And prevent toxicity from the build up of formaldehyde and formic acid.

05:23 In the case of methanol and a buildup of glycol aldehyde glycol eight gly oxalate and oxalate in the case of ethylene glycol.

05:35 The next drug that you should be familiar with is disulfiram or antabuse.

05:41 Now you probably heard that the symptoms of taking this drug and drinking alcohol are quite formidable in sense of a really, really bad hangover.

05:54 And that is because acetaldehyde dehydrogenase is inactivated and that results in a build up of acetaldehyde.

06:04 And excessive acetaldehyde is what causes the classic symptoms of a hangover.

06:11 So usually the hangover results from having sort of a back log in the activity of these enzymes.

06:18 So we have a build up of intermediaries creating a hangover.

06:22 Antabuse locks that creating greater symptoms and ideally prohibiting the individual from wanting to consume alcohol cause it feels so awful.

06:34 Anyway that's what you need to know on the basics of alcohol metabolism as far as nutrition is concerned.