Lecture 3, Energy Metabolism Flashcards

Question

Chemical Energy Derived From Fats (stage 2-4)

Answer 1

- stage 2: fatty acids are linked to coenzyme A (requires 1 ATP investment) = Fatty Acyl-CoA ◦ activating that fatty acid tail once it is snipped off in order to be used for energy ◦ these substrates need to move from cytosol to mitochondria - we need to be able to move carbon from one cellular component to other ◦ upfront energy investment of 1 ATP - stage 3: Fatty Acyl-CoA interacts with carnitine and can cross into mitochondrial matrix (carnitine shuttle) ◦ the carnitine attached onto fatty acid can help shuttle the fatty acid chain from cytosol to mitochondria ◦ there are different layers of regulations (breaking apart of triglyceride, attaching of acetyl CoA, finding a way to get it from cytosol to mitochondria) in order to use lipids ◦ once that molecule is inside mitochondrial matrix there is a bunch of enzymes that snip apart that fatty acid tail into 2-carbon molecules of acetyl CoA - stage 4: beta-oxidation: breaks down fatty acids into acetyl-CoA for entry into the Krebs cycle as previous ◦ cuts off all of those fatty acid chains into multiple 2 carbon acetyl CoA molecules ◦ can make up a lot of acetyl CoA from one fatty acid tail ◦ fatty acid carbon is use to make acetyl CoA in order to turn the cycle which essentially produces the energy from the triglyceride

Answer 2

- beta-oxidation: breakdown of fatty acids into acetyl Co-A. repeated until 2-C remain - ATP produced depends on the length of the fatty acid (4 –26 carbons) - more carbons = more ATP ◦ e.g. 18c stearic acid (18 chain carbon fatty acid) = 120 ATP molecules ◦ 1 chain of acetyl CoA can make 9 molecules of acetyl CoA ◦ makes 9 molecules of acetyl CoA ◦ if stearic acid exists as triglyceride (3 fatty acids combined to a glucose) you can make 3 times that (360 molecules of ATP) if the triglyceride if break down all 3 of the fatty acids - process requires oxygen and is coupled with carbohydrate availability / blood glucose - we need a sufficient level of carbohydrate to have an adequate amount of substrates when we want to use fatty acids - we do not use up acetyl CoA if we do not have enough oxaloacetate (gluconeogenic precursor) - if we do not have enough glucose in our system we do need up producing enough of oxaloacetate and we want to catabolize acetyl CoA, it is not there to be converted to substrate (essentially are missing our reactants if carbohydrates are low) - this is the reason why fat is much more energy dense than carbohydrates and proteins as there are way more carbon contained within them that is used to make ATP

Answer 3

- proteins are not stored but oxidized to make ATP or converted to new proteins for the growth and repair of the body 1. amino acids stripped of their nitrogen component (deamination) * we remove the nitrogen group we get deamination 2. remaining carbon skeleton can enter the breakdown pathways of the Krebs cycle at many different points 3. nitrogen component is converted to ammonia and then urea and excreted 4. ATP generated depends on stage AA enters the Krebs cycle – small compared to carbohydrate and fats * since there are entering from one so many different points we do not get one big representation of amino acids

Answer 4

1. ↑ number and size of mitochondria (as we exercise regularly we end up having more mitochondria and greater size - our body becomes more efficient as we increase our mitochondria and sensory of enzymes) 2. ↑ concentration of glycolytic enzymes (we are still using some amount of carbohydrate still even with endurance training - coordinated up regulation in the amount of proteins responsible for making ATP from glycolysis, Krebs, electron transport chain) 3. improved aerobic efficiency (waste a lot less energy completing work - getting a molecule of glucose converted to 32 ATP) 4. improved electron delivery to the ETC - through endurance training changes that happen to oxidative metabolism and enzymes that regulate it 5. ↑ ability of the muscle to oxidize lactate (oxygen delivery which helps us oxidize lactate to take pyruvate into mitochondria) 6. improvements in the heart’s stroke volume and angiogenesis 7. improved capillary density and capacity to transport fatty acids from plasma to muscle cells (we are really good turning on glycolysis - getting fatty acids out of fat cells and delivering it to the blood to our working muscles - can create need blood vessels and capillaries - we become really good at mobilizing energy stores from non muscular sources (adipose tissues)

Answer 5

- gluconeogenesis: creates glucose for the body from non carbohydrate precursors (glucose is vital to our existence) - carbon comes from sources that are not carbohydrate in nature - makes glucose from other sources ◦ amino acids enter the Krebs cycle ◦ pyruvate (come from glycerol as they are both 3 carbon) ◦ lactic acid - Cori cycle in liver converts to lactic acid to glucose (lactate gets produced from anaerobic glycolysis in our muscles gets shunted in liver where it converts it back into pyruvate and then into glucose which can be shoot back in muscle) ◦ glycerol - converted in the liver to glucose - a lot of systems to keep our glucose levels fairly stable - happens primarily in the liver but also in the kidney (10%) - anabolic reaction - fats: ◦ fatty acids cannot be converted directly to glucose and the pyruvate → acetyl-coA reaction cannot be reversed (catabolism of fatty acids through beta oxidation can help fuel gluconeogenesis - a carbon in a fatty acid is not getting recycled back into glucose it is still important for providing ATP that is required to make ATP even though it cannot be reversed and used itself) ◦ the glycerol can be used but the fatty acid tails can only aid and provide energy that supports this process - main site (90%) in liver, 10% in kidneys

Answer 6

assembles glucose molecules into branched chains for storage as glycogen - when demand for glucose ↓, glycogen synthase activity ↑ and restores glycogen stores in liver and muscle - the process of creating an ever-growing strand of glucose - glycogen synthase is the enzyme that primarily does this - glycogenesis is likely to occur when you are not using up or requiring a high degree of energy - when you just eat a meal as there is an abundance of energy substrates flowing around in our system (this is important in liver and muscles to create more glycogen) - replenish that we used up before we ate (pay back what we used up), after exercise as there is not an ATP demand at that point

Answer 7

accelerated during times of excess calorie consumption; often leads to the gain of fat tissue due to excess acetyl-CoA molecules - is the creation of lipid species (fats) - lipogenesis occurs when there is an energy surplus (create new energy substrate like glycogen and lipids that we can store for later use) or less energy demand (after feeding or recovery from exercise)

Answer 8

- this energy balance does not factor in social determinants for PA and health (you cannot just change your diet as it can be outside of your control) - regulation of body weight is based on some rules of thermodynamics (however it is an exceedingly complex process) - if you change your energy intake that can change your energy expenditure and vice versa

Answer 9

3 principle components of energy expenditure: 1. resting metabolic rate (RMR); 50 – 70% - maintain basic physiologic function - roughly makes up half of our energy expenditure - can use interchangeably with basil metabolic rate (all of the energy that is needed to simply exist) - that energy is used for things like ion cycling, synthesis of hormones, maintenance of tissues etc. - 50-70% of the calories we burn in a day come from this 2. thermic effect of food (TEF); 10% - how much energy it takes to breakdown food - eating is gaining calories but the process of eating and digesting food requires us to burn and take energy to breakdown all of the macromolecules into forms that are meaningfully used by our body - this can change depending on what composes of our diet (the percentage can change) - protein has the highest simulation energy - when we digest we end up spend up using a lot of energy to make it digestable and get it into a useable form so we are left with less calories to actually store 3. physical activity: non-exercise activity thermogenesis (NEAT) + Physical activity. 15 – 30% - can be subdivided into two components - physical activity and NEAT - neat is standing, moving from places, chewing, fidgeting (uses up energy - not a lot) - neat is not under conscious control - can be determined by social factor (does everyone have the ability to make modifications to increase neat) - our energy intake would have to match our energy expenditure if we want to maintain current body weight (it is not acute but rather long term) caloric intake and energy expenditure may not be identical on a daily basis but with weight stability it is balanced over time - if we want to be in state of energy balance how do we know how many calories to burn - in order to know that you need to know how many calories your body burns - indirect (V02 max test - measure of oxygen consumption where we can estimate energy expenditure), direct calorimetry (heat that is given off your body - requires expensive and complex methodologies) and pr