MCAT Biology Ch3: Cellular Metabolism Kap Flashcards
(43 cards)
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
