Kaplan MCAT Biology Ch. 3: Cellular Metabolism
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sportyperson246 on June 26, 2012
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43 terms
Terms | Definitions |
|---|---|
 autotrophs | using the sun's energy to create organic molecules that store energy in their bonds (plants, carry this out through photosynthetic, don't require outside source of organic compounds) |
| heterotrophic | breaking down organic molecules and harnessing power held in the bonds (humans, catabolic) |
| formation of glucose by autotroph | involves breaking of C-O of CO2 and O-H bonds in H2O --> rearrange into glucose, store energy in chemical bond (sun's energy is endo) |
| formation of heterotrophic organisms | liberate energy by breaking bonds and coupling energy release to perform useful work (reverse of photosynthetic = cell respiration); some heat lost along the way. |
| ATP, NAD+ and FAD (coenzymes) | energy released during glucose catabolism is harnessed in useful way throug these intermediates; serves as high-energy electron shuttles between cytoplasm and mitochondria |
| ATP | -primary energy currency; rapid formation and degradation allowing energy stored and released -generated during glucose catabolism (also provides energy to reverse; made up of N-base adenine, sugar ribose (OH on C2), and three phosphate groups; actual energy in phosphate bonds due to close neg. charges (covalent), so when broken, releases; -breaking down makes either ADP + P or AMP + PP (7 kcal/mol) |
| NAD+ and FAD | -capable of accepting high-energy electrons during glucose oxidation -doesn't provide energy themselves, just passing through ETC, ATP generated by capture stored energy -in cell rep -- redox rxns -- NAD+ and FAD accept hydridre durign glycolysis and Krebs --- NADH and FADH2 (reduced) -- H- electrons carred to ETC on inner mito membrane -- produce ATP -- reverse (oxidize) NADH and FADH2 to original |
| glucose | heterotrophic cells requires this as primary source of fuel |
| glycolysis and cell rep | energy of glucose liberate through this two processes |
| Glycolysis: glycolytic pathway | -cytoplasm -02 or no -step 4: dihydroxyacetone phosphate isomerizes to PGAL -twice as many PGALs as glucose, so steps 5 - 9 twice as many as 1-4. -1 gluc --> 2 molecules 3-C pyruvate -steps 1 and 3 consume 1 ATP -steps 6-9 produce one ATP (twice) -total of four ATP, net of two -electron carriers, NAD+ reduced to NADH twice |
| substrate-level phosphorylation | ATP from ADP and P |
| pyruvate aerobic fate | pyruvate further oxidation through mito ETC |
| pyruvate anarobic fate | known as fermentation, some are obligate aerobes and anaerobes (designated environment), other are facultative, prefer one environemtn over other, but can survive in either |
| fermentation | reduces pyruvate to either ethanol or lactic acid, oxidizing back to NAD+ for further glycolysis; glycolysis + reduction of pyruvate; no new ATP, only NAD+, total of two ATP |
| two types of fermentation | alcohol and lactic acid |
| alcohol fermentation | -yeast and some bacteria -pyruvate decarboxylated (3C) -- acetaldehyde (2C) -- reduced by NADH -- ethanol and NAD+ |
| lactic acid fermentation | -some fungi and bac, mammal muscles -when O2 demand exceeds supply -NADH build up --> keep muscle working --> pyruvate redcued --> lactic acid (3C) and NAD+ --. dec local pH --> burn and fatigue -when O2 supply catch up --> lactic to pyruvate (Cori Cycle); amount of oxygen necessary is known as oxygen debt. |
| cellular respiration | -most efficent means of glucose catabolism --> 36 to 38 ATP per molecule of glucose -some action in cytoplasm, then to mitochondria 3 phrases: pyruvate decarboxylation, citric acid cycle, and ETC (aerobic, w/ O2 as final electron acceptor |
| pyruvate carboxylation | -aerobic resp, although doesn't require O2 -pyruvate from cytoplasm into mito matrix --- decarboxylated (CO2) --- acetyl-CoA, one NAD+ reduced to NADH per pyruvate (two) (key intermediate in using fat, protein, and other carb energy reserves) |
| coenzyme A | bound to remaining acetyl group when pyruvate is decarboxylated |
| acetyl-CoA | coenzyme bound to acetyl group which was produced when pyruvate is decarboxylated |
| citric acid cycle | -starts w/ combo of acetyl Co-A (2C) and oxaloacetate (4C) --> citrate (6C) -8 rxns, two C02 (4) released and oxaloacetate regenerated -total for ATP (from one ATP via substrate-level phosphorylation and GTP intermediate) -able to generate high energy electrons carried by NADH and FADH2, (each molecule gets 3 NADH and 1 FADH2) -coenzymes move elecrons to ETC on inner mito membrane where more ATP produced via oxidative phosphorylation - |
| ETC electron transfer | -where energy is harnessed - |
| oxidative phosphorylation | electrons from NADH and FADH2 are passed along assembly line of carriers that release free energy with each transfer, put towards ATP production |
| cytochromes | carriers are enzymes of oxidative phosphorylation, resemble hemoglobin, each containing central iron |
| hydride ions | very strong reducing agents |
| redox rxns | don't direclty produce usuable energy, they transport high-energy electrons to a final electron acceptor (oxygen), which is coupled to ATP generation |
| conversion of acetalaldehyde to ethanol | typical reduction rxn of aldehyde to alcohol |
| glucose | has 6 carbons; two of original six carbons are lost during pyruvate decarboxylation as CO2 |
| energy checkpoints of glycolysis | 2 ATP and 2 NADH |
| energy checkpoints decarboxylation of pyruvate | 2 NADH |
| TCA cycle | major purpose is to generate high-energy intermediates that can be used to make APTP some ATP generated from GTP directly through substrate level phosphorylation |
| ATP | actually made in form of GTP, which is genetically equivalent |
| energy checkpoints of TCA cycle | 6NADH 2FADH2 2ATP |
| oxygen | final electron acceptor in ETC=> result in formation of water molecule w/o this => ATP production is not adequate to sustain human life |
| CO2 | generated in citric acid cycle is same that's exhaled |
| glycolysis | location: cytoplasm |
| fermentation | location: cytoplasm |
| pyruvate to acetyl CoA | mito matrix |
| TCA cycel | mito matrix |
| ETC | inner mito membrane |
| NADH | = 3 ATP (only exception when generated in cytoplasm, generating only two ATP per molecule of this) |
| FADH2 | = 2 ATP |
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