Chapter 9 Flashcards
Fermentation
Partial degradation of sugars or other organic fuel that occur without the use of oxygen
Redox reactions
The transfer of one or more electrons from one reactant to another
The energy state of the electron changes as hydrogen (with its electrons) is transferred.
Ex: In respiration, the oxidation of glucose transfers electrons to a lower energy state, liberating energy that becomes available for ATP synthesis
Oxidation
The loss of electrons from one substance.
The substance being oxidized is referred to as the reducing agent.
Reduction
The addition of electrons to another substance.
The substance gaining the electron is the oxidizing agent.
Adding electrons is called reduction, adding negatively charged electrons to an atom reduces the amount of positive charge of that atom
NAD+
Coenzyme, that acts as an electron carrier, Passing electrons from hydrogen atoms to oxygen
NAD+ is reduced to form NADH
Electron transport chain
A chain consisting of a number of molecules, mostly proteins, built into the inner membrane of the mitochondria of eukaryotic cells
Process:
Electron transfer from NADH to oxygen is an exergonic reaction with a free energy change of of -222 kJ/ mole. Instead of this energy being released and wasted in a single explosive step, electrons cascade down the chain from one carrier molecule to the next in a series of redox reactions, losing a small amount of energy with each step until they finally reach oxygen, the terminal electronic acceptor, which has a very great affinity for electrons.
Each downhill carrier is more electronegative than it’s uphill neighbor with oxygen at the bottom of the chain. Therefore the electron transfer from glucose to NAD+, which is thus reduce to NADH, fall down an energy gradient in the electron transport chain to a far more stable location in the electro negative atom oxygen
List the three stages of cellular respiration
glycolysis
pyruvate oxidation and the citric acid cycle
oxidative phosphorylationelectron transport and chemiosmosis
Define Glycolysis:
Energy investment phase
Energy payoff phase
Net
Glycolysis is the sugar splitting that happens in order to create energy. At the end of glycolysis all carbons remain in the form of pyruvate. This occurs in the cytosol.
Energy investment phase: Two ATP are used to produce to ADP and two phosphate groups.
Energy payoff phase: four ATP are formed and two NADH +2H, Two pyruvate +2 H2O
Net: two pyruvate +2 H2O, two ATP, two NADH plus 2H +
How many steps are in the process of glycolysis and at what steps can this process be inhibited?
What is the inhibitor and activator?
There are 10 steps in glycolysis.
The third step can be inhibited by ATP and citrate.
Glycolysis activators are ADP and AMP
Describe the oxidation of pyruvate
Pyruvate enters the mitochondria via active transport. Pyruvate is converted to a compound called acetyl CoA
3 steps:
-pyruvate carboxyl group is fully oxidized and has little chemical energy. This is removed and given off as CO2, the first CO2 to be released
-The remaining two carbon fragment is oxidized, forming acetate. The extracted electrons transferred to NAD+, storing energy in the form of NADH
-coenzyme A, a sulfur containing compound, is attached it sulfur atom to the acetate its sulfur atom to the acetate forming acetyl CoA, which has high potential energy. This molecule will now feed it’s acetyl group into the citric acid cycle for further oxidation
Krebs cycle/citric acid cycle
Eight step process where two carbons from acetyl-CoA, from the oxidation of pyruvate, adds its two carbon acetyl groups to oxaloacetate producing citrate
3 NADH, 1 FADH2 and 1 ATP are created per pyruvate. There to pyruvate going through the citric acid cycle at one time. The carbon atoms added to the citric acid cycle are released on the second cycle in the form of CO2
What is the net amount of energy produced from glycolysis and oxidated pyruvate?
Two net ATP from glycolysis, two net ATP from the citric acid cycle
The pathway of electron transport
Most components of the chain are proteins, which exist in multiprotein complexes numbered one through four, each embedded in the mitochondrial matrix. During electron transport along the chain, electron carriers alternate between reduced and oxidize states as they accept and then donate electrons. Each component of the chain becomes reduced when it is an electronic acceptor from its uphill neighbor which has a lower affinity for electrons. It then returns to its oxidized form as it passes electrons to its downhill, more electronegative, neighbor.
NADH transfers electrons to?
FADH2 transfers electrons to?
NADH transfers electrons to complex one.
FADH2 transfers elections to complex two.
Although NADH and FADH2 each donated equivalent amount of electrons, two, for oxygen reduction, the electron transport chain provides about one third less energy for ATP synthesis when an electron donor is from FADH2 rather than NADH
ATP synthase and chemiosmosis
ATP synthase is the enzyme that makes ATP from ADP. This is embedded in the mitochondria matrix. Chemiosmosis is the process in which energy stored in the form of a hydrogen ion gradient across a membrane is used to drive cellular work such as the synthesis of ATP.
