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APHY 102 Lab 2 Exam
Metabolism, Glycolysis, Krebs Cycle, and The Electron Transport Chain
| Question | Answer |
|---|---|
| what is the first step of breaking down glucose? | glycolysis |
| where does glycolysis happen? | cytoplasm |
| does glycolysis require oxygen or not? | no |
| think of glycolysis as cracking glucose open. what happens to 1 glucose and what does it produce? | glycolysis splits 1 glucose (6 carbons) into 2 pyruvate (3 carbons each) and produces 4 ATP but uses 2 ATP. It also nets 2 NADH |
| what step comes after glycolysis? | Krebs cycle |
| what process should be associated with the name Krebs cycle, aka citric acid cycle? | extracting high-energy electrons to load up electron carriers |
| where does Krebs cycle happen? | in the mitochondrial matrix |
| does the Krebs cycle require oxygen? | indirectly yes |
| what is the linking step between glycolysis and the Krebs cycle? | pyruvate oxidation - in the mitochondria, each pyruvate loses 1 carbon released as CO2 and the remaining 2-carbon piece attaches to a helper molecule called CoA, altogether forming acetyl-CoA, and acetyl-CoA is what enters the Krebs cycle |
| what are the products of the Krebs cycle? | CO2 exhaled, lots of NADH and FADH2 (electron carriers), and a small amount of ATP |
| how much NADH and FADH are produced per acetyl-CoA? per glucose? | per one acetyl-CoA turn of the cycle = 3 NADH and 1 FADH2 and 1 ATP; per one glucose is 2 turns of the cycle: 6 NADH, 2 FADH2, 2 ATP |
| which produces more electron carriers, glycolysis or Krebs cycle? | Krebs cycle by far |
| what step happens after glycolysis and the Krebs cycle? | electron transport chain |
| what does the electron transport chain accomplish? | it's where most of the ATP is made - about 90% of ATP is made here |
| where does the electron transport chain happen? what does it use? | in the inner mitochondrial membrane, the ETC uses electrons from NADH and FADH2 |
| does the ETC require oxygen? | absolutely yes |
| what happens in the ETC? (1) | electrons move through a chain of proteins |
| what happens in the ETC? (2) | these electrons' energy pumps protons (H+) across a membrane |
| what happens in the ETC? (3) | a gradient is created like water behind a dam |
| what happens in the ETC? (4) | H+ flowing back through ATP synthase makes a lot of ATP |
| what happens in the ETC? (5) | oxygen combines with electrons and H+ producing water |
| where are complex carbohydrates found? | aka starches are found in bread, cereal, flour, pasta, nuts, and potatoes |
| where are simple carbohydrates found? | aka sugars, found in soft drinks, candy, fruit, and ice cream |
| what are some of the names of simple sugars? | glucose, sucrose, fructose |
| are disaccharides considered simple sugars? | yes |
| what are the three common disaccharides? | the three most common are sucrose (glucose + fructose), lactose (glucose + galactose), and maltose (glucose + glucose) |
| what is the molecule ultimately used by body cells to make ATP? | glucose |
| which cells rely almost entirely upon glucose to supply their energy needs? | neurons and RBCs |
| what happens to excess glucose? | it is converted to glycogen or fat and stored |
| what is glycogen? | the human body's version of starch - a storage molecule |
| what is known as the human body's more efficient way of storing energy? | fat - store 9 kcal/g versus 4 kcal/g for carbs and proteins |
| what are the most abundant dietary lipids, which are found in both animal and plant foods? | triglycerides |
| which substances, found in most vegetables, must be ingested because the body doesn't synthesize them? | essential fatty acids such as linoleic and linolenic acid |
| what are the 4 functions of dietary fats? | 1. help absorb vitamins 2. are a major energy fuel of hepatocytes(!) and skeletal muscle 3. are the preferred fuel of cardiac muscle 4. are a component of myelin sheaths and all cell phospholipid bilayers |
| which vitamins are the fat-soluble vitamins? | A, D, E, K |
| how do the heart and brain differ in their energy sources? | the brain is dependent on glucose whereas the heart prefers to run on dietary fats for fuel |
| what is a triglyceride? | has a glycerol backbone with 3 fatty acids hanging off it |
| the fatty deposits in adipose tissue provide 3 things. what are they? | 1. protective cushion around body organs, such as the kidneys 2. an insulating layer beneath the skin (like whale blubber) 3. an easy-to-store concentrated store of energy, more than twice the amount of carbs/proteins per g |
| dietary PROTEINS supply what substances to the body? | essential amino acids (must ingest) as well as the building blocks for nonessential amino acids (body makes) - for protein synthesis. proteins also are source of NITROGEN for nonprotein nitrogen-containing substances such as urea and creatinine |
| what is the all-or-none rule of protein synthesis? | not an actual rule in biology, but basically that all amino acids needed must be present at the same time for protein synthesis to occur |
| why is adequacy of caloric intake important in regards to protein? | without enough calories, protein is misused as fuel, negating its role in muscle retention and growth, ex.) in times of starvation |
| be able to recognize amino acids off this list of essential amino acids | tryptophan, methionine/cysteine, valine, threonine, phenylalanine/tyrosine, leucine, isoleucine, histidine in infants, arginine in infants |
| what are the organic (carbon-containing) compounds needed for growth and good health, crucial in helping the body use nutrients? | vitamins |
| what are the organic compounds that often function as coenzymes, such as in the Krebs cycle? | vitamins |
| which are the only 3 vitamins synthesized in the body? | D, K, B. (all others must be ingested) |
| why is vitamin A important? | to the eyes, though excess kerotene results in yellow/orange coloring to the skin |
| why is vitamin C important? | to the immune system |
| why is vitamin E important? | to the skin |
| where are water-soluble vitamins (B-complex and C) absorbed? | gastrointestinal tract |
| B12 additionally requires what to be absorbed? | gastric intrinsic factor |
| which cells make gastric intrinsic factor? | parietal cells (aka oxyntic) within the gastric glands of the stomach fundus and body |
| what is intrinsic factor? | glycoprotein essential for binding vitamin B12, alongside hydrochloric acid |
| chief cells make what? know the difference from parietal cells. | chief cells make pepsinogen (a precursor to pepsin) and gastric lipase to digest proteins and fats |
| parietal cells make what? know the difference from chief cells. | parietal cells make hydrochloric acid (HCl), which activates pepsinogen and kills microbes, and intrinsic factor, essential for vitamin B12 absorption |
| where are chief cells and where are parietal cells? | both found in the gastric glands of the intestinal mucosa. parietal cells (acid-secreting) are mostly found in the upper-to-middle part of these glands, while chief cells (enzyme-secreting) are concentrated at the base |
| how do vitamins A, C, and E act in an antioxidant cascade? | they will deactivate metabolism molecules called free radicals |
| what is the process wherein enzymes (usually kinases) shift the high-energy phosphate groups of ATP to other molecules? these molecules are then activated to perform cellular functions | phosphorylation, under the bigger categories of anabolism and catabolism, under the biggest umbrella of metabolism |
| what are the 3 major stages of metabolism? i.e., steps in processing energy-containing nutrients | digestion/nutrient transport to tissues anabolism & formation of catabolic intermediates where nutrients are a) built into lipids, proteins and glycogen, b) broken down catabolically to pyruvic acid + acetyl CoA oxidative breakdown (catabolism) |
| oxidation is very important in which metabolic cycle? | Krebs cycle |
| what is oxidation? | gain of oxygen or loss of hydrogen. whenever one substance is oxidized, another substance is reduced (that is, gains an electron) |
| true or false, oxidized substances lose energy (like PGAL in glycolysis) | true |
| true or false, reduced substances lose energy (like NAD+ becoming NADH) | false, they gain energy |
| what actor acts as hydrogen (or electron) acceptors? | coenzymes |
| NAD+ is 1 of 2 important coenzymes. what does NAD stand for? | nicotinamide adenine dinucleotide |
| FAD is 2 of 2 important coenzymes. what does FAD stand for? | flavin adenine dinucleotide |
| true or false, both NAD+ and FAD act as electron carriers that reduce other molecules, but they primarily act as oxidizing agents to become reduced themselves | true |
| what is the process called when an enzyme slaps a phosphate (P) onto ADP? | substrate-level phosphorylation |
| what processes is substrate-level phosphorylation important in? | it is central to glycolysis, the citric acid (Krebs) cycle, and phosphocreatine metabolism in muscles |
| most derived ATP requires sending coenzymes to mitochondria. why then is substrate-level phosphorylation significant? | SLP provides immediate, oxygen-independent ATP in the cytoplasm and mitochondrial matrix, crucial for rapid energy supply when oxygen is limited |
| what are the 2 mechanisms of ATP synthesis in living organisms? | substrate-level phosphorylation, oxidative phosphorylation |
| what process does oxidative phosphorylation use? | uses the chemiosmotic process, whereby the movement of substances across a membrane is coupled to chemical reactions |
| what carries out oxidative phosphorylation in the cristae of the mitochondria? | the electron transport proteins found there |
| earlier in glycolysis and the Krebs cycle, dehydrogenases stripped hydrogens from food and handed them over to NAD+ and FAD. what do the mitrochondrial cristae proteins do with the H+? | pump hydrogen ions into the intermembrane space, resulting in a steep diffusion gradient across the membrane |
| when hydrogen ions flow back across the membrane, what protein complex do they go through? | ATP synthase uses the flow of hydrogen ions to physically crush a phosphate group onto an ADP molecule. usually 3 ATP molecules are produced per turn of the synthase |
| true or false, since all carbohydrates are transformed into glucose, it is essentially glucose metabolism | true |
| know this pathway of oxidation of glucose | C6H12O6 + 6O2 → 6H20 + 6CO2 + 32 ATP + heat |
| glucose is catabolized in three pathways. what are they and where do they take place? | glycolysis occurs in the cell cytoplasm, Krebs cycle occurs in the mitochondrial matrix (liquid center), and ETC/oxidative phosphorylation occurs at the inner mitochondrial membrane and uses the intermembrane space |
| what are the 3 phases of glycolysis (occurring in the cytoplasm)? | glucose is oxidized into pyruvic acid; NAD+ is reduced to NADH + H+; 2 net ATP are synthesized by substrate-level phosphorylation |
| what product of glycolysis moves on to the Krebs cycle in an aerobic pathway / is reduced to lactic acid in an anaerobic environment? | pyruvic acid |
| what are the final products of glycolysis? | 2 pyruvic acid molecules, 2 NADH + H+ molecules (reduced NAD+), and a net gain of 2 ATP molecules |
| what cycle is fueled by pyruvic acid and fatty acids? | Krebs cycle |
| pyruvic acid is converted to acetyl-CoA in what 3 main steps? | decarboxylation (carbon is removed from pyruvic acid and CO2 is released), oxidation (hydrogen atoms are removed from pyruvic acid and NAD+ is reduced to NADH + H+), formation of acetyl-CoA (the resulting acetic acid is combined with coenzyme A) |
| what is the sulfur-containing enzyme important in the formation of acetyl-CoA? | coenzyme A |
| what is the 8-step cycle in which each acetyl group from pyruvic acid is decarboxylated and oxidized to regenerate oxaloacetate? | Krebs cycle |
| for each molecule of glucose entering glycolysis, how many molecules of acetyl-CoA enter the Krebs cycle? | 2 |
| what are the products of the Krebs cycle? | 3 molecules of NADH + H+, 1 molecule of FADH2, 2 molecules of CO2, 1 molecule of ATP |
| what happens to the hydrogens that are released when glucose is oxidized? | coenzymes NADH and FADH2 transport them; they enter a chain of proteins bound to metal atoms (cofactors); they combine with molecular O2 to form water(!); they release energy that is harnessed to attach Pi to ADP→ ATP is made via oxidative phosphorylation |
| the complexes at the ETC split hydrogens into protons (H+) and electrons. what structures pump the protons across the inner mitochondrial membrane? | cytochromes, which are certain ETC proteins that are colorful due to the heavy metals they contain. the electrons are shuttled from one acceptor to the next |
| in the ETC, electrons are delivered to which final electron acceptor? | oxygen, of which ions attract H+ to form water |
| which structure allows H+ to go down its gradient back to the matrix? | the high H+ spins ATP synthase and H+ diffuses back to the matrix, releasing energy for ATP synthase to make ATP |
| which electron carrier gets electrons from Complexes I and II and passes it on to III? | coenzyme Q (coQ) |
| which electron carrier shuttles electrons between Complexes III and 4? | Cytochrome C |
| true or false, the transfer of energy from NADH + H+ and FADH2 to oxygen releases large amounts of energy | true |
| why is NADH worth 2.5 ATPs? | NADH donates electrons to Complex I & produces 10 protons in intermembrane space. those flow back into matrix thru ATP synthase. takes 4 protons to synthesize & export a single ATP (3 to turn motor, 1 for transport), so 10 protons yield 2.5 ATPs (10÷4) |
| why is FADH worth 1.5 ATPs? | it donates its electrons to cytochrome II and only produces 2 H+s in the intermembrane space |
| the cytochromes create what? | an electrochemical proton gradient across the inner membrane |
| the electrochemical proton gradient across the inner membrane creates what and generates what? | creates a pH gradient and generates a voltage gradient, which together cause H+ to flow back into the matrix via ATP synthase |
| what's the difference between glycogenosis, glycogenolysis? | the first two are opposite processes: the former forms glycogen when glucose supplies exceed cellular need for ATP synthesis; the latter breaks down glycogen in response to low blood glucose |
| what is gluconeogenesis and its role? | gluconeogenesis is forming sugar from NON-carbohydrate molecules and takes place in the liver. protects the body and especially the brain, from the damaging effects of hypoglycemia by ensuring ATP synthesis can continue |
| true or false, all fats are routinely oxidized and catabolized for energy | false, only neutral fats are. they are broken down into glycerol and fatty acids. glycerol is put through the glycerol pathway and fatty acids through the fatty acid pathway |
| what is the glycerol pathway? | glycerol is converted to glyceraldehyde phosphate; glyceraldehyde is ultimately converted into acetyl-CoA which enters the Krebs cycle |
| what is the fatty acid pathway? | fatty acids undergo beta oxidation which produces (a) 2-carbon acetic acid fragments which enter the Krebs cycle and (b) reduced coenzymes which enter the ETC |
| true or false, lipogenesis and lipolysis are names for the same thing | false, they are opposites |
| what is the conversion of excess dietary glycerol and fatty acids to form triglycerides? | lipogenesis |
| why is glucose also easily converted into triglycerides? | glucose formed into acetyl-CoA is an intermediate in glucose catabolism and is the starting molecule for the synthesis of fatty acids |
| excess dietary protein results in ____ being oxidized for energy and converted into fat for storage? | amino acids |
| (highlighted) true or false, proteins are catabolized in times of starvation | true |
| why must amino acids be deaminated prior to oxidation for energy? | by removing the nitrogen-containing amino group, the molecule is converted into a keto acid, which can be transformed into intermediates like pyruvate or acetyl-CoA to enter the Krebs cycle |
| what are the most important anabolic nutrients and why? | amino acids because they form all protein structures and the bulk of the body's molecules (the most important catabolic nutrients would be glucose) |
| what is the state of the body called referring to how organic molecules (except DNA) are continuously broken down and rebuilt? | a dynamic catabolic-anabolic state, wherein the body's total supply of nutrients constitutes its nutrient pool |
| where do amine groups removed from catabolized amino acids end up? | in urine |
| true or false, it is tough for carbohydrates to be converted into fats | false, carbs are easily and frequently converted into fats, linked by key intermediates |
| how do carbs and fats differ from the amino acid pool of nutrients? | fats and carbs are oxidized directly to produce energy versus amino acids requiring deamination; also, excess amino acids must be converted to carbs or fat for storage |
| which molecule is the interconnector for pathways of nutrients? | acetyl-CoA |
| what happens in phosphorylation? | hexokinase takes a Pi from ATP to give it to the 6C glucose, turning into Glucose 6-Phosphate |
| what happens in priming? | phosphohexoisomerase rearranges the carbons to Fructose 6-Phosphate and phosphofructosekinae takes a Pi from ATP to make Fructose 1,6-Diphosphate |
| what happens in cleavage? | aldolase cleaves the fructose into 2 pieces |
| what happens in oxidation? | NAD+ steals 2 H from each of the two 3C pieces (PGALs) |
| what happens in dephosphorylation? | enzymes take off the phosphates from the sugars; each phosphate makes an ATP |
| what happens to pyruvic acid if there is no O2 available? | anaerobic fermentation keeps the cycle going by using lactate |
| what does CIA(AKG) SSFMO stand for? | krebs cycle intermediates citric acid, isocitric acid, alpha-ketaglutaric acid, succinyl-CoA, succinate, fumaric acid, malic acid, oxelacetic acid |
| what are the two C6 intermediates on either side of isocitric acid? | CiS-aconitic acid and oxalosuccinic acid |
| when do the NAD+ steal two hydrogens off the C6? | after isocitric acid, after AKG, and after malic acid is made |
| when does the FAD oxidize the C4 intermediate? | after succinic acid is made |
| after what step does GTP turn into GTP, making ADP into ATP? | after succinyl-CoA is made |
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