8.2 : Cell Respiration Flashcards
what occurs when the energy is converted into a useable form?
much of the energy is lost in the form of heat energy –> cells are then able to retain a significant amount of chemical energy in the form of ATP.
what is a respiratory substrate? examples?
- molecule from which energy can be liberated to produce ATP in living cells
- glucose, lipids, proteins, carbohydrates
how is energy transferred from respiratory substrates like glucose?
via oxidation –> when glucose is oxidised, energy is released and stored in ATP molecules.
what are decarboxylation reactions?
a reaction in which a carboxyl group (COOH) is removed, releasing CO2.
in respiration, a redox reaction takes place. What gets oxidised and what gets reduced? what occurs in these reactions?
- glucose gets oxidised to carbon dioxide : addition of oxygen, removal of hydrogen, loss of electrons, release of energy (exergonic)
- oxygen gets reduced to water : removal of oxygen, addition of hydrogen, gain of electrons, uptake of energy (endergonic)
in respiration, energy is produced in the form of heat and ATP. What does the fact that energy is left over suggest?
means that the energy set free from the exergonic reaction (oxidation), is larger than the amount required for the endergonic (reduction) reaction to take place.
what does the amount of energy in a molecule depend on?
- depends on its degree of oxidation
- an oxidised substance has less stored energy than a reduced substance (oxidation = exergonic= energy is set free during the reaction)
what are the processes that take place during cellular respiration?
1) glycolysis
2) link reaction
3) Krebs Cycle
4) Chemiosmosis / oxidative phosphorilation
what occurs during glycolysis?
1) Phosphorylation : reaction of phosphate with ATP activated glucose –> glucose-phosphate formed –> converted to fructose phosphate = molecules are less stable, meaning they are more reactive in the reaction.
- -> phosphate group added at the expense of another = ATP molecule, two ATP molecules consumed per molecule of glucose respired –> phosphorylation = fructose biphosphate
2) Lysis : splitting of fructose biphosphate into two molecules of triose phosphate (3 carbon sugars)
3) Oxidation : of triose phosphate (removal of hydrogen) –> denhydrogenase (enzyme) that does this, works with NAD (coenzyme) whihc is a hydrogen acceptor.
- -> REDOX reaction –> NAD is reduced (NADH2) –> able to pass hydrogen ions & electrons onto other acceptor molecules –> oxidised back to NAD.
4) ATP formation : occurs twice in reactions by which each triose phosphate molecule is oxidised to pyruvate = ATP synthesis at substrate level.
what occurs during the link reaction?
- pyruvate formed in glycolysis diffused into matrix of mitochondrion
- pyruvate (3 carbon) –> decarboxylised by the removal of carbon dioxide and oxidised by the removal of hydrogen, where NAD is reduced –> and the product (of oxidative decarboxylation ) is an acetyl group (2 carbon)
- -> combines with coenzyme A to form acetylCoA.
what occurs during the Krebs cycle?
- acetylCoA (2C) from the link reaction reacts with a 4-carbon organic acid, forming a 6-carbon organic acid (citrate) –> coenzyme A is release and reused in the link reaction.
- citrate (6C) is converted back into the 4-carbon acid by reactions in the krebs cycle, which involved :
- -> two carbon dioxide molecules given off
- -> molecule of ATP formed (synthesised at substrate level)
- -> three molecules of reduced NAD (nicotineamide adenine dinucleotide) are formed
- -> one molecule of coenzyme FAD (Flavin adenine dinucleotide) is reduced.
what occurs during oxidative phosphorilation / chemiosmosis?
- hydrogen atoms or their electrons (from reduced NAD / FAD) are transported along a series of carrier proteins–> these are combined with oxygen, forming water –> so, oxygen is the final electron acceptor.
- electron carrier proteins are arranged in the inner mitochondrial wall –> oxidise the reduced coenzymes –> energy from the oxidation process is used to pump the hydrogen ions (protons) to the inner membrane space (=high concentration of protons in matrix)
- -> protons flow back into the inner membrane space via channels in the thylakoid membrane = ATP synthase enzyme = ATPase –> flow down a concentration gradient, causing energy to be transferred and the synthesis of ATP to occur.
what are the structures of the mitochondrion, and how are they related to functions conducted?
- external double membrane –> permeable to pyruvate, carbon dioxide, oxygen, NAD (necessary for cellular respiration)
- inner membrane : surface area is increased due to foldings forming cristae –> enhances the electron transport chain & ATP synthase enzymes (faster).
- inter-membrane space : is a small space –> allowing the accumulation of protons (hydrogen ions), which generates a large concentration difference with the matrix –> facilitating phosphorilation.
