Unit 3: Topic 6 - Cellular Respiration Flashcards
What are the two major ways ATP is created across all life forms?
Organisms use one of two major processes to generate ATP from macromolecules: aerobic respiration or anaerobic respiration. Aerobic respiration, which is better known as cellular respiration, uses oxygen to generate energy from glucose (the process will be explained more in later flashcards). For situations where oxygen is not available or when the organism cannot conduct aerobic respiration, anaerobic respiration/ fermentation (of which there are two types) is used. Fermentation is much less effective at generating ATP from glucose than cellular respiration, so larger organisms tend to use cellular respiration.
What macromolecule do fermentation and cellular respiration use to create ATP?
A) Phospholipids
B) Glucose
C) Sucrose
D) Fructose
B) Glucose
What are the three major parts of cellular respiration?
The three stages of cellular respiration are glycolysis, the Krebs Cycle, and the electron transport chain. Throughout these three stages, enzymes are used to slowly break down glucose and use electron carriers to capture the energy released in the process.
What are the electron transport chains, and what are the major locations where these reactions occur?
Electron transport chains are a series of reactions that use the energy from an excited electron to establish an electrochemical gradient across a membrane (the energy is used to transport ions across the membrane). Electron transport chains play essential roles in cellular respiration and photosynthesis, and they also occur on prokaryotic plasma membranes. In animal cells, the electron transport chain used for cellular respiration is on the inner mitochondrial membrane. In plant cells, the electron transport chains used for photosynthesis are on the thylakoid membranes, and the transport chain used for cellular respiration is in the same place as in animal cells.
Describe the role of the movement of electrons through the electron transport chain in cellular respiration, and explain how it differs from the electron transport chain reactions that occur on prokaryotic plasma membranes.
In cellular respiration, electrons from NADH and FADH2 are passed onto the proteins of the electron transport chain, from where they travel down to the chain to the terminal (final) electron acceptor of oxygen. This differs from the electron transport chains in prokaryotes because prokaryotes perform anaerobic respiration, which means that the final electron acceptor will not be oxygen, but a different molecule.
What is the final electron acceptor in photosynthesis?
A) NAD+
B) NADH
C) NADP+
D) NADPH
C) NADP+
In photosynthesis, the electron transport chain uses energy from sunlight to excite an electron, which then travels down the transport chain to the final acceptor of NADP+. The energy that is now stored in NADP+ will be used in the Calvin Cycle to create glucose.
Explain the results of the movement of electrons down the electron transport chain.
As electrons travel down the proteins in the electron transport chain, the energy from those electrons is used to power the active transport of protons. The proteins harness the energy from the electron and use it to move protons across the membrane that the transport chain is located on (whether that be the inner mitochondrial membrane, the inner thylakoid membranes of the chloroplast, or the plasma membrane of a prokaryote). This establishes a region of high proton concentration and a region of low protein concentration, which can be used by ATP synthase to generate ATP.
Explain in detail the movement of electrons down the electron transport chain in cellular respiration.
First, NADH (an electron carrier, the source of which will be explained later) gives its electron to protein complex I, and FADH2 (another electron carrier) gives its two electrons to complex II. Complex I uses the energy from its electron to pump protons from the mitochondrial matrix to the intermembrane space, but complex II does not. Then, complexes I and II pass their electrons to an electron carrier protein called ubiquinone (Q), from where the electrons from both complexes follow the same path. Ubiquinone passes the electrons onto complex III, which pumps more protons across the membrane. From there, the electrons are carried by the electron carrier cytochrome C to complex IV, which pumps more protons across the membrane and then passes the electrons onto the final electron acceptor (oxygen).
A diagram that shows the information explained above
What role does the electron transport chain play in generating ATP?
The electron transport chain establishes the electrochemical gradient of protons that ATP synthase uses to create ATP. The movement of protons down their concentration gradient through ATP synthase results in a release of energy as the potential energy stored in the proton gradient gets converted to mechanical energy. The membrane-bound ATP synthase then uses this mechanical to bind inorganic phosphate to ADP to create ATP, where the energy is now stored as chemical energy. This process is known as oxidative phosphorylation.
How can the electron transport chain be used by endothermic organisms to regulate body heat?
By decoupling the electron transport chain from oxidative phosphorylation, the electron transport chain would not result in oxidative phosphorylation, and instead, the energy released by the protons moving down their concentration gradient will be released as heat. This heat can be used to regulate body heat.
Explain the role glycolysis plays in cellular respiration.
Glycolysis is a reaction that breaks down glucose into two molecules of pyruvate, which will later be used to create Acetyl CoA (which is used in the Krebs Cycle). Since glycolysis consists of an energy investment phase (where 2 molecules of ATP are used to break glucose down into 2 molecules of G3P) and an energy payoff phase (which generates 2 molecules of NADH and 4 molecules of ATP from the oxidation of G3P into pyruvate), there is a net gain of 2 molecules of ATP and 2 molecules of NADH.
Where in the cell does glycolysis happen?
A) The inner mitochondrial membrane
B) The mitochondrial matrix
C) The thylakoid membranes
D) The cytosol
D) The cytosol
What is the link reaction between glycolysis and the Krebs Cycle?
Before the Krebs Cycle occurs, the 2 molecules of pyruvate formed during glycolysis are transported into the mitochondrial matrix (where the Krebs Cycle takes place), where they are oxidized into 2 molecules of Acetyl CoA (the inputs of the Krebs Cycle). This link step also produces 2 molecules of NADH in the process of oxidizing pyruvate.
Describe the role of the Krebs Cycle in cellular respiration.
The general purpose of the Krebs Cycle is to generate NADH and FADH2 for use in the electron transport chain. To accomplish this, Acetyl CoA is joined with oxaloacetate to form citric acid (which is why this process is also known as the Citric Acid Cycle). Citric acid is then oxidized in steps, forming the end products of 1 molecule of oxaloacetate (which can then be used to start the process again), 3 molecules of NADH, 1 molecule of FADH2, 1 molecule of ATP, and 2 molecules of CO2 per molecule of Acetyl CoA. This cycle happens twice per molecule of glucose since 1 glucose produces 2 Acetyl CoA, so 6 NADH, 2 FADH2, and 2 ATP are produced in the Krebs Cycle for each glucose molecule.
A diagram that shows the information stated above
What purpose do NADH and FADH2 serve in cellular respiration?
After the Krebs Cycle, all the molecules of NADH and FADH2 produced in glycolysis, the link reaction, and the Krebs Cycle are used in the electron transport chain. These two molecules act as electron/energy carrier molecules, meaning that they carry over the energy stored in electrons to the electron transport chain. They give their electrons to the proteins of the electron transport chain, which use the energy from the electrons to establish a proton gradient.
