Unit 2b: Cellular Respiration and Photosynthesis Flashcards
Describe the chemical formula of glucose.
C6H12O6
How many ATPs does one glucose molecule charge?
38 (as suggested by IB)
36 (sometimes)
List the phases of aerobic respiration, where in the cell they occur and their net ATP generation per glucose molecule.
Glycolysis: cytoplasm
+2 net ATP
Link Reaction: occurs as pyruvate is being transported through outer membrane to the matrix
+0 net ATP
Citric Acid/Krebs Cycle: matrix
+2 net ATP
Oxidative Phosphorylation/ETC: inner membrane
+32 net ATP
List the components of the mitochondria.
Components relevant to this unit:
Outer membrane
Intermembrane space
Inner membrane
Matrix
Cristae
Other components:
Mitochondrial DNA
Ribosomes
What kind of reaction is glycolysis?
Redox (reduction-oxidation) reaction
State the net equation (very first reactants –> very last products) of aerobic respiration.
C6H12O6 + 6 O2 –> 6 CO2 + 6 H2O + Energy
What is OIL RIG? Explain its meaning.
Oxidation
Is
Loss (of electrons)
Reduction
Is
Gain (of electrons)
Explains the flow of electrons of a given reaction
Choose the proper answer:
Oxidation results in a…
gain/loss of electrons
gain/loss of protons (H+ ions)
gain/loss of potential energy
gain/loss of oxygen
Reduction results in a…
gain/loss of electrons
gain/loss of protons (H+ ions)
gain/loss of potential energy
gain/loss of oxygen
Oxidation:
loss of electrons (OIL RIG), potential energy, hydrogen (protons follow electrons)
gain of oxygen
Reduction:
gain of electrons, potential energy, hydrogen
loss of oxygen
Name the three phases of glycolysis, as well as the initial reactant(s) and final product(s).
Activation of Glucose
Splitting of Glucose
Oxidation of G3P to Pyruvate
Glucose –> pyruvate (via oxidation)
Describe the “activation of glucose” stage in Glycolysis.
Glucose reacts with two ATP molecules and has two phosphate groups attached to either end, forming fructose 1,6-bisphosphate (short form: F 1,6-BP) [6C]
Glucose is converted to this form because glucose is not as symmetrical as fructose
NET EQUATION: C6H12O2 + 2 ATP –> 2 F 1,6-BP + 2 ADP
Describe the “splitting of glucose” stage in Glycolysis.
Fructose 1, 6-biphosphate (F 1,6-BP) {6C} is split into two: DHAP and Glyceraldehyde 3-phosphate (aka triose phosphate/G3P) {3C}
- Because fructose is not perfectly symmetrical, the extra oxygen atom goes to the DHAP [3C]
- DHAP is identical to G3P but has an extra oxygen atom
- DHAP is converted into G3P and undergoes the same process
Every F 1,6-BP is eventually split into 2 G3Ps
NET EQUATION: 2 F 1,6-BP –> 2 G3P
Describe the oxidation of G3P to pyruvate, and provide the net ATP gain during the entire process of glycolysis.
2 hydrogen atoms are removed from each of the two G3P [3C], which then react with NAD+ and Pi, forming NADH + H+ (there are more hydrogen ions than NAD+ molecules) and attaching another Pi to each G3P
The NADH + H+ go to the ETC
The two phosphate groups from each G3P are transferred to ADP (this reaction is called substrate level phosphorylation) to form ATP
Each G3P is now a pyruvate [3C] molecule
EQUATION: 2 G3P + 2 NAD+ 2 Pi –> 4 ATP, 2 NADH + H+
Net gain of 2 ATP in glycolysis (+4 ATP in this phase, -2 ATP in the activation of glucose)
Describe the link reaction (between glycolysis and the Krebs cycle)
Two pyruvate molecules [3C] that come from the oxidation of G3P to pyruvate are transported from the cytoplasm into the mitochondrial matrix via carrier proteins on the membrane
Each pyruvate loses a carbon atom through carboxylation, which forms a carbon dioxide molecule
The new compound [2C] loses 2 hydrogen atoms to NAD+, producing NADH + H+ and forming an acetyl group
The acetyl compound combines with coenzyme A to form acetyl coenzyme A (acetyl CoA)
NET EQUATION: 2 pyruvate –> 2 CO2, 2 acetyl CoA, 2 NADH + H+
Describe the Krebs cycle, as well as all the products made per glucose molecule
.
Acetyl CoA transfers its acetyl group to oxaloacetate [4C] to make citrate [6C]
- Coenzyme A returns to the link reaction in order to bring in another acetyl molecule
The molecule [6C] reacts with 2 instances of NAD+, losing two carbons and 4 H+ ions in the process, producing 2 CO2, 2 NADH and 2 H+
ADP and an inorganic phosphate react with the energy present in the molecule [4C] to create 1 ATP via substrate level phosphorylation
The molecule [4C] loses two H+ ions to FAD, another electron carrier, to produce FADH2
The molecule [4C] then loses one H+ ion to NAD+ to produce NADH; the molecule now turns into oxaloacetate, and is able to start the cycle again by picking up another acetyl molecule
Note: because glucose produces two molecules of acetyl CoA, the Krebs cycle occurs twice per glucose molecule
Net production (per glucose molecule): 4 CO2, 2 ATP, 6 NADH + H+, 2 FADH2
What is the purpose of oxidative phosphorylation/the electron transport chain (ETC) in aerobic respiration?
To release the energy stored from the NADH and FADH2 produced by the other steps of aerobic respiration and create more ATP
Describe the process of oxidative phosphorylation/the electron transport chain (ETC), and how it is altered in the absence of oxygen.
The electron transport chain (ETC) is a long series of proteins and organic molecules found on the cristae (folds on inner membrane) of mitochondria
Hydrogen/electron carriers (NADH, FADH2) are oxidized and donate their stored electrons and protons to the ETC
As the electrons move through the ETC, they lose energy to the protein complexes located on the chain
The protein complexes use this energy to pump hydrogen ions from the matrix into the intermembrane to maintain an electrochemical gradient (aka a proton motive force); the intermembrane contains many more protons, and is thus much more positive than the matrix
Chemiosmosis is performed:
- The accumulated H+ ions pass through the transmembrane enzyme ATP synthase (due to osmosis) to move from the intermembrane space back to the matrix
- This movement is exergonic (releases energy); this provides enough energy for ATP Synthase to catalyze the phosphorylation of ADP + Pi –> ATP
At the end of the chain in the matrix, oxygen picks up the de-energized electrons in order to prevent the clogging of the chain
Two H+ ions that came into the matrix (via ATP synthase, after chemiosmosis) react with 1/2 of an O2 particle and the electron to form water
In the absence of oxygen, the electron transport chain clogs up in the 4th complex, as oxygen is unable to remove the de-energized electrons from the chain (forcing the body to undergo anaerobic respiration)
Define chemiosmosis, and provide an example.
The use of energy released from the movement of ions across a semipermeable membrane with the electrochemical gradient to catalyze a reaction
A prime example to know is the movement of H+ ions across the mitochondria’s inner membrane to catalyze ADP + Pi –> ATP
Define phosphorylation, and provide an example.
The attachment of a phosphate group to a molecule/ion.
A prime example to know is ADP + Pi –> ATP
When is anaerobic respiration used, and why is it important?
When there is a lack of sufficient oxygen
Recall that oxygen is used to “pick up” de-energized electrons at the end of the ETC; lack of oxygen means the ETC gets clogged in the 4th complex with the de-energized electrons, and hydrogen/electron carriers (NADH and FADH2) cannot drop off their electrons or protons
- Thus, chemiosmosis cannot be performed and ATP cannot be produced
Anaerobic respiration comes into clutch in an attempt to keep the organism alive by producing (significantly) smaller quantities of ATP (but at least ATP is being produced)
What is VO2 max? What happens at VO2 max?
The maximum rate that oxygen can be transported/used in the body
At this level, aerobic respiration becomes limiting; the graph of oxygen consumption vs exercise intensity plateaus
What can VO2 max measure, and what units does it use?
It is considered the best indicator for an athlete’s fitness and aerobic endurance
It is expressed either as an absolute rate (e.g. L of O2 / min) or relative rate (mm of O2/kg of body mass*min)
Describe the process of lactic acid/lactate fermentation. In what organisms does it take place?
After glycolysis and before the chain reaction, 2 pyruvate accept electrons from NADH to form 2 lactic acid and 2 NAD+ via the enzyme lactate dehydrogenase
The 2 NAD+ are reused in glycolysis; the 2 ATP produced in glycolysis are the only source of ATP
This takes place in mammal muscle and some bacteria
Describe the process of alcohol fermentation. In what organisms does it take place?
2 pyruvate molecules each lose 1 carbon to form 1 CO2 each; this is done through the enzyme pyruvate decarboxylase
- The pyruvate molecules are now acetaldehyde
The electrons from 2 NADH are donated to the acetaldehyde to produce 2 ethanol and 2 NAD+; this process is catalyzed by the enzyme alcohol dehydrogenase
The 2 NAD+ are reused in glycolysis; the 2 ATP produced in glycolysis are the only source of ATP
This takes place in yeast
