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MCAT Biology - Cellular Metabolism
Terms in this set (39)
An organism that obtains organic food molecules without eating other organisms or substances derived from other organisms;
Autotrophs use energy from the sun or from the oxidation of inorganic substances to make organic molecules (e.g. glucose) from inorganic ones (water and carbon dioxide).
- e.g. plants and photosynthesis.
Organisms that can only get the organic molecules and energy necessary for life through the consumption of other organic matter. In the food web, all consumers and decomposers are heterotrophs. Heterotrophs can be herbivores, carnivores, or omnivores.
Consumes energy (endothermic) to create a complex molecule from simple ones (e.g. photosynthesis).
breakdown of complex molecules to smaller molecules to release energy (exothermic).
e.g. Glucose to CO2, H2O and ATP
ATP, NAD+ and FAD (both coenzymes).
Adenosine Triphosphate (ATP)
E available immediately to do work.
nitrogenous base, ribose, 3 phosphate functional groups; there is a high energy bond between the 2nd and 3rd phosphate groups. It can readily transfer that last phosphate group to many other molecules inside cells.
transfer of E from glucose to ATP occurs in two stages: glycolysis and cellular respiration
anaerobic process occuring in the cytoplasm in which glucose is broken down into two molecules of (3C's) pyruvate and two net ATP are produced
Net rxn of Glycolysis
NET: Glucose + 2ADP + 2 Pi + 2 NAD+ --> 2 Pyruvate + 2 ATP + 2NADH + 2H+ + 2H2O
Total E output of 4 ATP (via substrate level phosphorylation), but only 2 net bc 2 ATP required for rxn to go.
process that does not require oxygen.
require their designated environment.
Have a preferred environment but can survive in either.
Fate of Pyruvate
Aerobic Organisms (use oxygen to survive):cellular respiration (ETC)
Anaerobic Organisms: fermentation (alcohol or lactic acid fermentation)
Includes all the steps of glycolysis + reduction of pyruvate (from the oxidation of NADH to NAD+).
Allows us to reform NAD+ so that it may be recycled and glycolysis may continue.
Glycolysis followed by the conversion of pyruvate to carbon dioxide and ethyl alcohol.
- occurs in yeast and some bacteria
Pyruvate (3C) --> CO2 + Acetaldehyde (2C)
Acetaldehyde + NADH + H+ --> Ethanol (2C) + NAD+
Lactic Acid Fermentation
series of anaerobic chemical reactions in which pyruvic acid uses NADH to form lactic acid and NAD+, which is then used in glycolysis; supplies energy when oxygen for aerobic respiration is scarce.
- occurs in some fungi and bateria;also in mammalian muscle cells.
Net Rxn for Lactic Acid Fermentation
Pyruvate (3C) + NADH + H+ --> Lactic Acid + NAD+
The process by which accumulated lactate from anaerobic lactic acid fermentation is shuttled to the liver to be converted back to pyruvate and then to glucose and returned to muscle. The Cori cycle provides a means to deal with the pyruvate that accumulates during anaerobic glycolysis;
Net loss of 4 ATP.
amount of oxygen required to oxidize lactic acid produced anaerobically during strenuous muscle activity.
The aerobic harvesting of energy from food molecules (carbs, fats and amino acids) such as glucose, and the storage of potential energy in a form that cells can use to perform work (ATP); involves glycolysis, the citric acid cycle, and oxidative phosphorylation (the electron transport chain and chemiosmosis).
- net: 36-38 ATP
Step 1: Pyruvate Decarboxylation
1st step of aerobic respiration in which pyruvate is transferred from cytoplasm to mitochondrial matrix where it loses a CO2.
- Acetyl remains (2C) and is bound to coenzyme A (acetyl CoA
Net Rxn for Pyruvate Decarboxylation
Net: 2 Pyruvate (3C) + 2 CoA + 2 NAD+ --> 2 NADH + 2 acetyl-CoA (2C) + 2 CO2 (1C)
Citric Acid Cycle
a chemical cycle involving eight steps that completes the metabolic breakdown of glucose molecules begun in glycolysis by oxidizing acetyl CoA (2C - derived from pyruvate) with oxaloacetate (4C - regenerated at end of cycle) to 2 carbon dioxide ;
- occurs within the mitochondrion in eukaryotic cells and in the cytosol of prokaryotes;
- together with pyruvate oxidation, the second major stage in cellular respiration.
- Generates high E e-s carried in NADH and FADH2 for use in the ETC;
- aka Krebs Cycle and tricarboxylic acid cycle (TCA)
- Each turn (2turns/glucose) generates 1 ATP (in the form of GTP - via substrate-level phosphorylation), 3 NADH, 1 FADH2,
Net Rxn Kreb Cycle
2 Acetyl CoA + 6 NAD+ + 2 FAD + 2 GDP + 2 Pi + 4 H2O --> 4 CO2 + 6 NADH + 2 FADH2 + 2 ATP + 4 H+ + 2CoA
The formation of ATP by an enzyme directly transferring a phosphate group to ADP from an intermediate substrate in catabolism;
- occurs during glycolysis and the Krebs cycle.
Electron Transport Chain
Process involving a series of enzyme complexes (cytochromes - contain central Fe ion) found along the inner mitochondrial membrane, the thylakoid membrane in chloroplasts and the plasma membrane in prokaryotes .
- NADH and FADH2 are oxidized by tehse enzymes; the electrons are shuttled down the chain and are ultimately passed to oxygen and to produce water. The electron energy is used to pump H+ out of the mitochondrial membrane; the resulting H+ gradient is subsequently used to drive the production of ATP via oxidative phosphorylation.
NADH Pathway in ETC
- Complex I: hands of e-s to FMN
- passed to Carrier Q (ubiquinone)
- Complex III
- passed to cytochrome c
- Complex IV: protein cytochrome a3 passes to oxygen along with 2 H+ to make H2O
- 1 NADH generates 3 ATP (exception: in cytoplasm aka in glycolysis, 1 NADH = 2ATP)
FADH2 pathway in ETC
Complex II aka succinate Q oxidoreductase
passes to carrier Q
- rest is the same as NADH
- less d traveled so less E generated; 2 ATP per FADH2
Final e- Acceptor in ETC
Oxygen; 2H+ + 2e- + 1/2 O2 --> H2O
ETC disrupted by Cyanide and DNP
Cyanide: blocks the final transfer of e-s to O2
DNP: destroys mitochondria's ability to creat H+ gradient
ATP generation and the Proton Pump
reduced carries give up e-s and H+ are passed into matrix; accumulate and are pumped out into intermembrane space via complexes. gradient drives H+ passively back across inner mitochondrial membrane into the mito matrix (proton-motive force) via channels, enzyme complex aka ATP synthase, E is released and phosphorylation of ADP back to ATP occurs (oxidative phosporylation0.
Glycolysis occurs in the _______.
Fermentation occurs in the ________.
Pyruvate to Acetyl CoA occurs in the _________.
TCA cycle occurs in the _________.
ETC occurs in the _________.
inner mitochondrial membrane
The production of ATP from ADP and Pi molecules using energy derived from the redox reactions of an electron transport chain; occurs in mitochondria.
NADH and ATP output
4 ATP from glycolysis (2 NADH x 2)
6 ATP from pyruvate decarbox. (2 NADH x 3)
18 ATP from TCA (6 NADH x 3)
28 ATP total from NADH
4 ATP from TCA Cycle (2FADH2 x 20
THIS SET IS OFTEN IN FOLDERS WITH...
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