Chapter 8-How Cells Make ATP: Energy-Releasing Pathways Flashcards
catabolism
releases energy by splitting complex molecules into smaller components
anabolism
the synthesis of complex molecules from simpler building blocks; anabolic reactions are endergonic and require ATP or other energy sources to drive them
redox reaction
the chemical reaction in which one or more electrons are transferred from one substance (the substance that becomes oxidized) to another (the substance that becomes reduced)
In the overall reaction of aerobic respiration, which reactant becomes oxidized and which becomes reduced?
glucose becomes oxidized, oxygen becomes reduced
What is the general equation for cellular respiration of glucose?
C6H12O6 + 6O2 —-> 6CO2 + 6H2O + 38 ATP
How do cells obtain ATP?
All cells must make their own ATP from nutrients they have either synthesized (autotrophs) or consumed (heterotrophs)
All cells (prokaryotic and eukaryotic) require energy to:
combat entropy, carry out day-to-day functions, repair/replace worn out organelles, reproduce
What happens during reduction? Oxidation?
Remember: OIL RIG; Oxidation is losing, reduction is gaining
Explain the first phase of glycolysis.
The word glycolysis means “sugar splitting”, glucose does not require oxygen and it occurs in the cytosol; the first phase of glycolysis is the “energy investment phase”, first, glucose is phosphorylated (a phosphate group is transferred from ATP to glucose) and the resulting product is fructose-1,6-biphosphate which is less stable than glucose so it is broken down into two three-carbon molecules (dihydroxyacetone phosphate AND glyceraldehyde-3-phosphate (G3P), the dihydroxyacetone phosphate is converted to G3P, so the products at this point are two molecules of G3P which can be summarized as [glucose + 2ATP —-> 2G3P + 2ADP
Explain the second phase of glycolysis.
called the “energy capture phase”, each G3P from the last phase is oxidized by the removal of 2 electrons (as part of two hydrogen atoms), these hydrogen atoms/electrons combine with they hydrogen carrier molecule, NAD+; because there are two G3P molecules for every glucose, two NADH are formed, this phase can be summarized with this equation: 2G3P + 2NAD+ + 4ADP —> 2 pyruvate + 2NADH + 4ATP
Explain how pyruvate is converted to acetyl CoA.
In eukaryotes, the pyruvate molecules enter the mitochondria, in prokaryotes, they enter the cytosol; the pyruvate undergoes a process known as oxidative decarboxylation, first, a carboxyl group is removed as carbon dioxide which diffuses out of the cell, then the remaining two-carbon fragment becomes oxidized and NAD+ aaccepts the electrons removed during the oxidation, finally, the oxideized two-carbon fragment, an acetyl group, becomes attached to coenzyme A, yielding acetyl CoA; the overall reaction for the formation of acetyl CoA is: 2 pyruvate + 2NAD+ + 2CoA —> 2 acetyl CoA + 2 NADH + 2CO2
Explain the Krebs cycle.
first, acetyl CoA tranfers its two-carbon acetyl group to the four-carbon acceptor compound oxaloacetate, forming citrate, a six-carbon compound, the citrate then goes through a series of chemical transformations, losing first one and then a second carboxyl group as CO2, one ATP is formed (per acetyl group) by substrate level phosphorylation, in the course of the krebs cycle, two molecules of CO2 and the equivalent of 8 hydrogen atoms are removed, forming three NADH and one FADH2, some of these hydrogen atoms come from water molecules that are added during the reactions of the cycle
What does the citric acid cycle yield?
four CO2, six NADH, two FADH2, and two ATP per glucose molecule
Explain the Electron Transport Chain.
the electron transport chain is a series of electron carriers embedded in the inner mitochondrial membrane of eukaryotes and in the plasma membrane of prokaryotes, each of these carriers exists in an oxidized form or a reduced form, in the electron transport chain, each acceptor molecule becomes alternately reduced as it accepts electrons and oxidized as it gives them up, the electrons entering the chain have relatively high energy content but they lose some of their energy at each step as they pass along the chain, the chain contains four large, distince protein complexes of acceptors, Complex I accepts electrons from NADH molecules that were produced during glycolysis, the formation of acetyl CoA, and the krebs cycle, Complex II accepts electrons from FADH2, Complexes I and II both produce the same product, reduced ubiquinone, which is the substrate of Complex III, that is, Complex III accepts electrons from reduced ubiquinone and passes them on to cytochrome c, Complex IV accepts electrons from cytochrome c and uses these electrons to reduce molecular oxygen, forming water in the process, because oxygen is the final electron acceptor in the chain, organisms that respire aerobically require oxygen
How many ATP’s can one NADH produce? One FADH2?
one NADH produces 3 ATPs and one FADH2 produces 2 ATPs
