Tutorial 27 Cellular Respiration

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Redox A chemical reaction in which one molecule is oxidized and another is reduced.
Reduction A molecule gains an electron, entailing a decrease in its positive charge.
Oxidation Removal of one or more electrons from an atom, ion, or molecule.
Oil RiG Oxidize species lose electrons and reduced species gain electrons.
What is the general equation of a redox reaction? Xe- + Y –> Xe+ + Y-
electronegativity The affinity for electrons and likelihood of being reduced by addition of electrons.
What happens to an oxidized molecule? It loses energy.
What happens to a reduced molecule? It gains energy.
What does an exergonic reaction entail? Release of energy.
What is carbon dioxide? A reduced form of carbon.
What is water? A reduced form of oxygen.
Why is heat not very useful for biological reactions? It is released as a by-product of chemical reactions.
What happens as electrons from other molecules move closer to oxygen? They lose energy, which can be used to do work.
What in essence is cellular respiration? A series of reactions in which electrons are removed from glucose and its catabolic products to oxygen or some other terminal electron acceptor.
What is the "work" done in cellular respiration? The synthesis of ATP.
What kind of reaction is ATP? Anabolic.
What is the general equation for cellular respiration? C6 H12O6 + 6 O2 –> 6 CO2 + 6 H2O + energy
What is the end result of the cellular respiration equation? Oxygen is reduced to form water and glucose is oxidized to produce carbon dioxide.
What should be kept in mind with the "simple" redox reaction for cellular respiration? It is actually a controlled series of steps that controls the oxidation of glucose so that the high amount of energy released is not wasted as heat.
oxidant An electron carrier.
What is the most prevalent electron carrier? Nicotinamide adenine dinucleotide (NAD).
What are the two forms of NAD? NADH (reduced form) and NAD+ (oxidized form)
What is NAD+ able to do? It can pick up electrons.
What is the main feature of NADH? It has two more electrons than NAD+ and an additional proton, giving it a balanced charge.
What are necessary for reduction of NAD+ to NADH? Dehydrogenase and hydrogen.
oxidizing agent electron acceptor
What does NAD+ function as during cellular respiration? An oxidizing agent that picks up electrons from catabolic products of glucose, as well as hydrogen atoms).
What does it take to reduce an NAD+ molecule? Two high-energy electrons and one hydrogen atom.
Why does NAD+ act as a shuttle? Once it is reduced to NADH, it can deposit its electrons, oxidize to NAD+, and pick up more electrons.
What happens when NAD+ accepts a hydrogen atom from H2? The second hydrogen remains unpaired; these unpaired hydrogens accumulate.
What is important about high-energy molecules? They are unstable and can spontaneously change into low-energy molecules, with the release to do work.
What is important about glucose? It is a highly ordered, high-energy molecule that is catabolized in the transduction of cellular energy.
What is the most important thing contained by ATP? Three high-energy-containing phosphate groups.
Cellular respiration The ability of cells to use the energy in a glucose molecule to convert that energy to energy in the form of ATP.
What is peculiar about oxygen? It is highly electronegative.
What is the key to the high amount of energy obtained from a glucose molecule? The high electronegativity of oxygen.
What are the three steps of cellular respiration? 1. Glycolysis2. Krebs cycle3. Electron transport/oxidative phosphorylation
Where does glycolsis take place? In the cytosol.
Where does the Krebs cycle take place? In mitochondria.
Where does electron transport/oxidative phosphorylation take place? In mitochondria.
Glycolysis The initial breakdown of glucose to pyruvate, water, and NADH.
Pyruvate A 3-carbon molecule that is an end product of glycolysis
What happens with food intake? It is broken down by saliva and stomach enzymes.
How is glycolysis initiated? By addition of P from ATP, which destabilizes the molecule, breaking bonds and releasing energy.
Despite the net gain in ATP from cellular respiration, what is required? Some ATP to initialize the reaction.
How many steps are involved in glycolysis? Ten.
What is PEP? A phosphorylated molecule acting as a substrate that transfers a phosphate group to ADP.
What is important about substrate-level phosphorylation? It can only occur in the present of a specific kinase enzyme depending on the particular substrate.
How much ATP is required to break down one molecule of glucose to pyruvate? Two molecules.
What is the output of glucose breakdown to pyruvate? Four ATPs and two NADHs.
What is the net gain from one molecule of glucose from glycolysis alone? Two ATPs and two NADHs.
Where does most of the energy remain after glycolysis? In the pyruvate molecule.
At what stages of cellular respiration is most ATP produced for cellular work? The Krebs cycle and electron transport chain.
What is important about glycolysis not using oxygen as an electron acceptor? Glycolysis can occur in aerobic or anaerobic conditions.
fermentation The process by which glucose is partially broken down and NAD+ is regenerated.
alcohol fermentation Pyruvate gives off carbon dioxide and is converted to ethyl alcohol (ethanol) in a two-step process.
lactic acid fermentation Pyruvate is converted to lactate (lactic acid).
The metabolic pathway that converts glucose into pyruvate and 2 molecules of ATP. Glycolysis
NAD+ An oxidizing agent – it accepts electrons from other molecules and becomes reduced.
NADH A reducing agent – it donates electrons to other molecules and becomes oxidized.
Substrate-level phosphorylation A metabolic reaction that produces ATP by the direct transfer of a phosphate group to ADP from another phosphorylated compound
Kinase An enzyme that modifies proteins by transferring high-energy phosphate groups to them.
What type of organisms use glycolysis? All: photoautotrophs, photoheterotrophs, chemoautotrophs, chemoheterotrophs.
Glycolysis produces ATP by what process? Substrate level phosphorylation.
Protein kinases Enzymes that modify other proteins by chemically adding phosphate groups to them.

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