Chapter 9 - Cellular Respiration: Harvesting Chemical Energy Flashcards
What is a Redox reaction? (also known as oxidation-reduction reactions.)
“OIL RIG” - “Oxidation is Lost, Reduction is Gain”
In oxidation, a substance loses its electrons; it’s oxidized.
In reduction, a substance gains its electrons; it;s reduced.
What happens to the carbon and the oxygen when methane is oxidized?
when methane is oxidized:
CH4 + O2 —> CO2 + 2H2O
Carbon “loses” electrons to Oxygen when CO2 is formed.
Oxygen “gains” elections from Hydrogen when H2O is formed.
In the attached reaction, which substance is reduced and which is oxidized?
Also, why is energy released in cellular respiration?
The energy release during cellular respiration is due to the fact that glucose is oxidized.
As elections from Hydrogen are transferred to Oxygen, energy is released as they go from high energy state to low energy state.
Explain the oxidation of glucose and why it’s so willing to be oxidized.
Glucose has an abundance of hydrogen atoms (12) waiting to be oxidized.
Glucose cannot oxidize all at once… if it did, there would be a large release of energy (EXPLOSION).
So, by having a sequential method for releasing energy (releasing gradually), less energy is lost. This is done through multiple reactions.
Rocket fuel is an example of this reaction.
What is a Coenzyme? and- what is the coenzyme used in cellular respiration?
A coenzyme is a substance that enchances the action of an enzyme ( which speeds up a reaction ).
The coenzyme in cellular respiration is Nictotinamide Adenine Dinucleotide , or NAD+.
What is the function of NAD+ (Nicotinamide Adenine Dinucleotide) ?
Known as the “Electron Shuttle”
Electrons lose very little energy when they are transferred from glucose to NAD+.
1) NAD+ is reduced to NADH when it accepts electrons.
2) NADH has high energy electrons, so it is edventually oxidized back to NAD+.
Energy is used in electron transport chain to produce ATP
What are the two ways energy can be obtaned from glucose?
Energy can be obtained from Glucose in two ways:
1) In presence of oxygen: Aerobic Respiration (aka cellular respiration)
Oxygen and organic fuel are consumed, producing ATP
2) In the absence of oxygen: Fermentation
Partial degradation of sugars
**Regenerates NAD+**
Both processes begin with “Glycolysis”.
Explain Substrate Level Phosphorylation
Enzymes phosphorylate ADP to form ATP
Produces relatively small amount of ATP
Brieftly describe the three stages to cellular respirarion
1. Glycolysis - “Splitting of sugar”, Metabolic pathway that breaks 1 molecule of glucose into 1 molecules of pyruvate.
2. Citric Acid Cycle - takes place within mitochondrial matrix.
3. Oxidative phosphorylation - accounts for most of ATP synthesis
What are the intermediate products in Glycolysis? (Splitting of sugar)
1) Hexokinase 6) Triose phosphate dehydrogenase
2) Phosphoglucoisomerase 7) Phosphoglycerokinase
3) Phosphofructokinase 8) Phosphoglyceromutase
4) Aldolaes 9) Enolase
5) Isomerase 10) Pyruvate kinase
Where does Glycolysis (stage 1) occur and what does it ultimately do?
Glycolysis occurs in the cytosol
and is the “splitting of glucose into 2 pyruvate”
What happens during the citric acid cycle?
and, where does this happen?
Transition from Stage 1 to stage 2. Glycolysis à Citric Acid Cycle (CAC)
CAC occurs within mitochondria in presence of O2.
Upon entering mitochondria… Pyruvate is converted to Acetyl CoA (coenzyme A). For each pyruvate molecule, 1 CO2 is released and 1 NADH is formed
This step links glycolysis to the citric acid cycle.
**Each “turn” of the cycle generates:
i) 1 ATP,
II) 3 NADH and
III) 1 FADH2 (also an electron shuttle)
In the citric acid cycle, each “turn” of the cycle generates what?
1) 1 ATP,
2) 3 NADH and
3) 1 FADH2 (also an electron shuttle)
How many steps are there in the citric acid cycle?
CAC has 8 steps: each catalyzed by a specific enzyme
1) The acetyl group of acetyl CoA joins the cycle by coming with oxaloacetate, forming citrate.
2-7) The next seven steps decompose the citrate back to oxaloacetate.
The NADH and FADH2 produced by the cycle relay electrons extracted from food to the electron transport train.
For every molecule of Glucose, Glycolysis and the Citric Acid Cycle have made what?
4 ATP molecules (by substrate-level phosphorylation)
10 NADH Molecules
2 Glycolysis + 2 producing Acetyl CoA + 6 during CAC
2 FADH2
2 H2O molecules
4 CO2 molecules
What is the function of the electron transport train?
break the large free-energy drop from NADH or FADH2 to O2 into smaller steps that release energy in manageable amounts. The electron transport chain generates no ATP.
What is the final part of ATP production?
Chemiosmosis
“ATP synthesis powered by the flow of H+ back across a membrane”
Electron transfer in the electron transport chain causes proteins to pump hydrogen ions or protons, or H+ from:
The mitochondrial matrix to the intermembrane space
Pumping H+ across a membrane creates a membrane potential
The imbalance of H+ concentration on either side of membrane creates the potential energy for H+ to flow back across the membrane.
Membrane potential is the basis of Chemiosmosis.
When H+ flows back across the membrane, they pass through a protein complex called ATP synthase. ATP synthase uses the exergonic flow of H+ to make ATP
Summarize ATP production in three brief steps.
1) Glycolysis and Citric Acid Cycle transfer electrons and NAD+ and FAD, forming NADH and FADH2.
2) Those high energy electrons then go through the electron transport chain (ETC) creating a membrane potential across the inner-membrane of mitochondrion vis chemiosmosis.
3) This proton-motive force drives the protein complex ATP synthase, which phosphorylates ADP making ATP.
