7.1 An Overview of Cellular Respiration Flashcards
catabolism
describes the set of chemical reactions that break down molecules into smaller units, releases chemical energy that can be stored in molecules of ATP
anabolism
the set of chemical reactions that build molecules from smaller units, require an input of energy, usually in the form of ATP
cellular respiration is one of the major sets of:
catabolic reactions in a cell
cellular respiration is a series of catabolic reactions that converts the energy stored in food molecules into:
the energy stored in ATP
what are the wastes or by-products of cellular respiration?
carbon dioxide and water
aerobic respiration
cellular respiration that occurs in the presence of oxygen
anaerobic respiration
cellular respiration that occurs in the absence of oxygen
oxygen is consumed in aerobic respiration; the products are:
carbon dioxide and water
carbohydrates and lipids have a large amount of potential energy in their chemical bonds, whereas:
carbon dioxide and water have less potential energy in their bonds
cellular respiration releases a large amount of energy because:
the sum of the potential energy in all of the chemical bonds of the reactants is higher than that of the products
the maximum amount of free energy released during cellular respiration is:
-686kcal per mole of glucose
if all the energy stored in glucose were released at once:
most of it would be released as heat and the cell would not be able to harness it to do work
in cellular respiration, energy is released:
gradually in a series of chemical reactions; this allows some of the energy to be used to form ATP
how many molecules of ATP are produced from the aerobic respiration of a single molecule of glucose?
32
in most organisms, cellular respiration consumes oxygen and produces ATP by…?
substrate-level phosphorylation and oxidative phosphorylation, as well as carbon dioxide and water
how much of the total energy released by aerobic respiration is harnessed in the form of ATP?
34% with the remainder of the energy given off as heat
what are the two different ways to produce ATP from the chemical energy stored in a molecule of glucose?
substrate-level phosphorylation and oxidative phosphorylation
substrate-level phosphorylation
a way of generating ATP in which a phosphate group is transferred to ADP from an organic molecule, which acts as a phosphate donor or substrate
in the case of substrate-level phosphorylation, there are two coupled reactions carried out by a single enzyme:
the hydrolysis of a phosphorylated organic molecule and the addition of a phosphate group to ADP
substrate-level phosphorylation produces only:
a small amount of the total ATP generated in cellular respiration (12%)
electron carrier
a molecule that carries electrons (and energy) from one set of reactions to another
electron transport chain
the system that transfers electrons along a series of membrane-associated proteins to a final electron acceptor, using the energy released as electrons move down the chain to produce ATP
in aerobic respiration, oxygen is the:
final electron acceptor, resulting in the formation of water
oxidative phosphorylation
a set of metabolic reactions that occurs by passing electrons along an electron transport chain to the final electron acceptor, oxygen, pumping protons across a membrane, and using the proton electrochemical gradient to drive synthesis of ATP
electron transport chains are used in respiration to:
harness energy from fuel molecules
outline the major steps in oxidative phosphorylation:
chemical energy of organic molecules are broken down by catabolism, electrons carriers transport electrons and energies to the electron transport chain, electron transport chains transfer electrons along a series of membrane-associated proteins to a final electron acceptor and in the process harness the energy released to produce ATP, oxygen is final electron acceptor and forms water as a product
oxidation-reduction reactions
a reaction involving the loss and gain of electrons between reactants. In biological systems these reactions are often used to store or release chemical energy
oxidation
the loss of electrons
reduction
the gain of electrons
the loss and gain of electrons always occur together in a :
coupled oxidation-reduction reaction
what occurs in a coupled oxidation-reduction reaction?
electrons are transferred from one molecule to another so that one molecule loses electrons and one molecule gains those electrons
the oxidized molecule….
loses electrons
the reduced molecule….
gains electrons
what are two important electron carriers in cellular respiration?
nicotinamide adenine dinucleotide (NAD+) and flavin adenine dinucleotide (FAD)
what is the reduced form of NAD+ and FAD?
NADH and FADH2
in redox reactions involving organic molecules (ex. NAD+ and FAD), the gain or loss of electrons if often accompanied by:
the gain or loss of protons (H+)
reduced molecules can easily be recognized by:
an increase in C-H bonds and the corresponding oxidized molecules by a decrease in C-H bonds
in their reduced forms, NADH and FADH2 can :
donate electrons, this allows electrons (and energy) to be transferred to the electron transport chain
the oxidation of NADH and FADH2 also produces:
NAD+ and FAD which can then accept electrons from the breakdown of fuel molecules
electron carriers act as shuttles, transferring electrons derived from:
the oxidation of fuel molecules (Ex. glucose) to the electron transport chain
even though it consists of many steps, cellular respiration can be understood as a:
redox reaction (glucose is oxidized producing carbon dioxide, oxygen is reduced forming water)
in carbon dioxide, how are electrons shared?
not equally, the oxygen atom is more electronegative than the carbon atom, as a result, carbon has partially lost electrons to oxygen and is oxidized
in glucose, carbon atoms share electrons…
equally
in oxygen gas, electrons are shared…
equally between two oxygen atoms
in water, the electrons that are shared between hydrogen and oxygen are more likely to be found near:
oxygen because the oxygen is more electronegative. as a result, oxygen has partially gained electrons and is reduced
glucose is a good electron donor because:
its oxidation to carbon dioxide releases a lot of energy
oxygen is a good electron acceptor because:
it has a high affinity for electrons
in cellular respiration, glucose is not:
oxidized all at once to carbon dioxide, oxidized in a series of reactions to release energy in a controlled manner
some of the energy released in the series of reactions between glucose being oxidized to produce carbon dioxide can be:
used to synthesize ATP directly and some of it is stored temporarily in reduced electron carriers and then used to generate ATP by oxidative phosphorylation
cellular respiration has how many stages?
4
glycolysis
the breakdown of glucose to pyruvate; the first stage of cellular respiration
outline the process of stages 1 (glycolysis):
glucose is partially broken down to make pyruvate and energy is transferred to ATP and reduced electron carriers
what occurs in stage 2 of cellular respiration?
pyruvate is oxidized to another molecule called acetyl-coenzyme A (acetyl-CoA), producing reduced electron carriers and releasing carbon dioxide
citric acid cycle (tricarboxylic -TCA cycle or the Krebs cycle)
the third stage of cellular respiration, in which acetyl-CoA is broken down and more carbon dioxide is released
outline the citric acid cycle:
acetyl-CoA enters stage 3, completely oxidized to carbon dioxide and energy is transferred to ATP and reduced electron carriers. The amount of energy transferred to ATP and reduced electron carriers in this stage is nearly twice that of stages 1 and 2 combined
oxidative phosphorylation
a set of metabolic reactions that occurs by passing electrons along an electron transport chain to the final electron acceptor, oxygen, pumping protons across a membrane, and using the proton electrochemical gradient to drive synthesis of ATP
outline what occurs in stage 4 of cellular respiration:
reduced electron carriers generated in stages 1-3 donate electrons to the electron transport chain and a large amount of ATP is produced
outline where the stages of cellular respiration occur in eukaryotes:
glycolysis takes place in the cytoplasm, pyruvate oxidation/citric acid cycle/oxidative phosphorylation all take place in mitochondria
the electron transport chain is made up of:
proteins and small molecules associated with the inner mitochondrial membrane
where do reactions of cellular respiration occur in bacteria?
it takes place in the cytoplasm and the electron transport chain is located in the plasma membrane
the change in the free energy is much greater for the steps that generate:
reduced electron carriers composed to those that produce ATP directly
