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APHY 201 Exam 1d
Ch. 5 Cell Respiration and Metabolism
| Question | Answer |
|---|---|
| which drives the other between catabolism and anabolism? | catabolism drives anabolism; think how catabolizing glucose allows for the anabolism of ATP, involving many redox reactions |
| The 3 stages of glucose breakdown are glycolysis, Krebs cycle, and electron transport chain. what are these 3 called collectively? | these are the 3 stages of aerobic cellular respiration |
| what is the equation for aerobic cellular respiration? | C6H12O6 (glucose) + 6 O2 --> 6 CO2 + 6 H2O |
| true or false, the first steps of breaking down glucose are anaerobic | true |
| where do glycolysis, Krebs cycle, and electron transport chain occur, respectively? | glycolysis in the cytoplasm (anaerobic), citric acid (Krebs) cycle in the mitochondrial matrix (aerobic), and ETC on cristae of mitochondria (aerobic) |
| differentiate between glycogenesis, glycogenolysis, and gluconeogenesis. | glycogenesis stores excess glucose as glycogen (liver), glycogenolysis breaks that down so glucose can be used (liver and muscle), and gluconeogenesis synthesizes entirely new glucose from non-carbohydrate sources |
| in glycolysis, note that there is a loss of 4 hydrogen ions lost that were attached to the carbons of glucose. what happened? | the 4 hydrogen ions were ued to reduce 2 molecules of NAD (yields 2 NADH) |
| is glycolysis endergonic or exergonic? | exergonic. think about how catabolism is exergonic |
| 4 ATP are generated in glycolysis, but how many are used up / how many are net positive? | 2 ATPs are used in glycolysis, so it nets 2 ATP |
| what occurs so that glucose cannot diffuse back through the plasma membrane? | it is phosphorylated by specific -ase enzymes who use Pi stripped from ATPs |
| why does free energy decrease as glycolysis occurs? | free energy decreases because the cell oxidizes and breaks down a high-energy glucose molecule into lower-energy pyruvate molecules. this overall process is exergonic |
| what is the equation for reactants/products in glycolysis? | glucose + 2 NAD + 2 ADP + 2 Pi --> 2 pyruvic acid + 2 NADH + 2 ATP |
| without O2 to complete the breakdown of glucose, NADH gives its electrons to pyruvic acid. NAD reforms and pyruvic acid is converted to what in the process of anaerobic metabolism? | lactic acid (lactate) |
| what is another name for anaerobic metabolism? | lactic acid fermentation, which still yields a net gain of 2 ATP (!) |
| what cell type in the blood plasma can only use lactic acid fermentation because it lacks mitochondria? | RBCs |
| what is the difference between combustion and aerobic respiration? | the key difference is that energy is released in small, enzymatically controlled steps, not in large amounts of heat |
| the products of glycolysis are 2 pyruvate molecules, 2 NADH, 2 ATP. what do the pyruvic acid and NADH go? | pyruvate is used next in the Krebs cycle (citric acid cycle), and the NADH will be oxidized to make ATP (!) |
| how does pyruvic acid become acetic acid? | as pyruvate leaves the cytoplasm and enters the matrix of mitochondria, CO2 is removed (decarboxylation) to form acetic acid |
| what happens to acetic acid next in prepration for the Krebs cycle? | acetic acid is combined with coenzyme A (CoA) to form acetyl-CoA. so 1 glucose does become 2 molecules acetyl CoA, AND two CO2s, reducing NAD to NADH in the process |
| what is the tricarboxylic acid another name for? | Krebs/citric acid cycle |
| how is citric acid formed? hint: citric acid is what starts off the Krebs cycle--and it is so named :) | acetyl-CoA combines with oxaloacetic acid to form citric acid |
| true or false, citric acid is a cycle because citric acid moves through a series of reactions to produce oxaloacetic acid again | true |
| what important events happen in one turn of the Krebs cycle regarding GTP/ATP, NAD, and FAD? give numbers of how many molecules of each are produced. | 1 GTP is produced and donates a Pi to ADP, forming ATP; 3 NADs are reduced to NADHs, and 1 FAD is reduced to FADH2. these amounts are doubled when taken into consideration that 1 glucose yields 2 turns of the Krebs cycle |
| what are the products of the Krebs cycle PER GLUCOSE? | 6 NADH, 2 FADH2, 2 ATP, and 4 CO2. phew! |
| would the process of the electron transport chain have to be endergonic or exergonic? | exergonic because energy is produced (to make ATP from ADP through phosphorylation) |
| what is the name of the theory that explains how cels generate energy in ATP form, stating that free energy from e- transport is used to pump H+ across a membrane --> making ATP? | chemiosmotic theory |
| what are respiratory assemblies? | another name for the Complexes at the electron transport chain, THROUGH WHICH H+ ions MOVE |
| what does the H+ concentration gradient accomplish? | movement of H+ across the membrane provides energy to ATP synthase, which crushes a Pi onto ADP to make ATP (oxidative phosphorylation) |
| why is it important that oxygen act as the final electron acceptor? | citric acid cycle (indirectly) and electron transport chain (directly) require oxygen to continue |
| explain the equation O2 + 4 e- + 4 H+ --> 2 H2O | O2 receives electrons in its valence shell, breaking the molecule into 2 atoms. the atoms each attract 2 e- and 2 H+, yielding H2O |
| how many ATP are yielded altogether by direct substrate-level phosphorylation in glycolysis plus the citric acid cycle (2 turns here)? | 4 ATP |
| in oxidative phosphorylation at the electron transport chain, theoretically each NADH yields 3 ATP (2.5 practically) and each FADH2 yields 2 ATP (1.5). what is the yield for ATP per glucose? | 36-38 theoretically, 32 in practice (6 lost) |
| why would it be dangerous for cells to store a lot of glucose? | it would pull water into the cell via osmosis |
| why doesn't glycogen pull water inside the cell? | glycogen does not pull excess water into cells because it is an insoluble, massive polymer |
| where is glucose stored as glycogen? (3 areas) | liver, skeletal muscles, and cardiac muscles |
| what is the process that changes glucose to glycogen? | glycogenesis |
| how does glycogenesis happen? | glucose is phosphorylated, then isomerized; glycogen synthase removes the phosphate and joins glucose together |
| when the cell needs glucose, it breaks stored glycogen down. what is this process called? | glycogenolysis; produces glucose 1-phosphate, catalyzed by gylcogen phosphorylase (!) |
| what are the fates of glucose 6-phosphate? | can undergo glycolysis if it gets turned into fructose 6-phosphate, can get dephosphorylated by enzymes at the liver and go into the blood (gluconeogenesis) or be stored back to glycogen (glycogenesis) |
| what is the primary enzyme responsible for buildling glycogen in the body via glycogenesis? | glycogen synthase |
| true or false, glycogenesis and glycogenolysis both happen at the liver | true |
| what is the opposite enzyme of glycogen synthase? i.e., if glycogen synthase is building up glycogen at the liver, which enzyme breaks it down to start glycogenolysis, producing glucose 1-phosphate? | glycogen phosphorylase |
| when the liver gets lactic acid from the blood (from the skeletal muscles before that), the liver converts it to pyruvic acid and rebuilds it to glucose via gluconeogenesis. what is this pathway/process called? | Cori cycle aka lactic acid cycle |
| which enzyme at the liver converts lactic acid to pyruvic acid and NADH? (hint: this enzyme also does the opposite and converts pyruvic acid into lactic acid.) | lactic acid dehydrogenase |
| what process turns pyruvate into free glucose so muscles can use it again? | gluconeogenesis in the Cori cycle |
| true or false, lipids and proteins take a different pathway from the metabolism of pyruvic acid | false, lipids and proteins can also be used for energy via the same pathways used for the metabolism of pyruvic acid |
| true or false, ATP is stored for later | false, ATP is made and used almost immediately. glucose must be converted and stored as glycogen and fat, and ATP production is inhibited |
| what is the process used for fatty acids to combine with glycerol to form triglycerides in the adipose tissue and liver? | lipogenesis |
| when ATP production is inhibited because of rising levels of ATP after an energy-rich meal, what are some types of lipids that are formed from acetyl CoA? | cholesterol, ketone bodies, and fatty acids |
| what is the term for fatty acids combining with glycerol to form triglycerides in the adipose tissue and liver? (hint: storage) | lipogenesis |
| using the enzyme lipase, lipolysis breaks triglycerides down into what 2 types of molecules? | fatty acids (enter the bloodstream and bind to albumin protein) and glycerol (sent to the liver to be converted into glucose) |
| glycerol is taken up by the liver after fat breakdown and converted to glucose through which process? | gluconeogenesis |
| what is the link and/or difference between lipolysis and beta-oxidation? both have to do with fat. | lipolysis=cell gets fat out of storage, beta-oxidation is how it burns that fat for energy. lipases break apart triglycerides, then an enzyme at the target cell attaches CoA to make fatty acyl-CoA. inside the mitochondrial matrix, beta-oxidation occurs |
| in beta-oxidation, what molecules are removed from fatty acids to form acetyl CoA? | |
| what is the process called where enzymes remove acetic acid molecules from fatty acids to form acetyl CoA? | beta-oxidation |
| a 16-carbon fatty acid yields how many acetyl-CoAs? | 8 acetyl CoAs (and 108 ATP!) |
| what kind of tissue is involved in thermogenesis for newborns? | brown adipose tissue / brown fat |
| what triggers brown fat into thermogenesis? | the sympathetic release of norepinephrine |
| how does brown fat use up fatty acids? | sympathetic norepinephrine causes brown fat to form an uncoupling protein called UPCI (thermogenin); H+ leaks out of inner mitochondrial membrane, less ATP is formed, mitochondrion "panics" and uses up fatty acids causing more heat generation |
| what is the term for the molecules that result as a lipolysis exceeding the rate of fatty acid utilization (dieting, starvation, diabetes...)? | ketone bodies |
| how are ketone bodies formed? | liver cells convert fatty acids into acetyl CoA and then into ketone bodies, which are water-soluble molecules that circulate in the blood. buildup can cause ketosis |
| without functional insulin signaling, glucose is trapped outside the cells because cells can't open which doors of which transport proteins? | GLUT4 |
| true or false, proteins provide nitrogen for the body | true |
| true or false, nitrogen is toxic in some forms and helpful in others | true, toxic in ammonia but helpful on/as proteins |
| what is the primary reaction called that is used to swap, move, and recycle amino acids? | transamination |
| which coenzyme is required for transamination? | vitamin B6 (pyridoxine) |
| true or false, transamination for all amino acids is handled by a handful of different enzymes | false, each transamination requires a specific enzyme |
| what is the difference between transamination and oxidative deamination? | they are sequential in amino acid metabolism. transamination transfers an AA's Ngroup to a keto acid (usually α-ketoglutarate), forming glutamate. oxidative deamination removes that N from glutamate as free ammonia, converting it back to the keto acid |
| if there are more amino acids than needed, which process comes into play to strip the amine group from glutamate and excreted in urea? | oxidative deamination |
| when does the formation of glucose from amino acids occur? this is a type of gluconeogenesis. | in the Cori cycle |
| there are 3 main substrates of gluconeogenesis, and each has 3 carbons to it. what are these 3 substrates? | alanine, lactic acid, and glycerol |
| what must occur before an amino acid can be used for fuel in the body? | its nitrogen-containing amine group must be removed |
| which organ do glucose and ketone bodies come from? | liver |
| which tissue do fatty acids come from? | adipose |
| which tissue do lactic acid and amino acids come from? | muscle |
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elianayu
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