| what is respiration | a series of metabolic pathways which bring about the release of energy from the breakdown of food molecules (eg glucose).
The energy released is used to generate the energy transfer molecule ATP |
| how significant is cellular respiration to metabolism | cellular respiration is central to metabolism and is linked to many other pathways |
| what does phosphorylation require | ATP
ATP has a role in carrying out phosphorylation reactions |
| what is a phosphorylation reaction | involves a phosphate group being added to a substrate |
| what are the three stages of cellular respiration | glycolysis
citric acid cycle
electron transport chain |
| what is glycolysis | the breakdown of glucose to pyruvate in the cytoplasm in a series of enzyme controlled steps |
| describe the process of glycolysis | ATP is required for the phosphorylation of glucose and intermediates during the energy investment phase of glycolysis
This leads to the generation of more ATP during the energy pay off stage and results in a net gain of ATP |
| what is the function of dehydrogenase enzymes during glycolysis | dehydrogenase enzymes remove hydrogen ions and electrons from the intermediate substrate molecules. These hydrogen ions and electrons immediately attach to co enzyme molecules called NAD, forming NADH.
these co enzyme molecules are also known as hydrogen carriers. |
| what is meant by energy investment in glycolysis | 2 ATP is broken down to supply phosphate and energy to progress the reactions of glucose being converted from intermediate 1 to intermediate 2 |
| what is meant by energy payoff in glycolysis | enough energy is released during the breakdown of intermediate 2 to pyruvate reactions to generate 4ATP (4ADP are phosphorylated) |
| when does the citric acid cycle take place | if oxygen is available, the pyruvate produced at the end of glycolysis progresses into the citric acid cycle |
| where does the citric acid cycle take place | in the matrix of the mitochondria |
| describe the citric acid cycle | in aerobic condition, pyruvate is broken down to an acetyl group and carbon dioxide is released
acetyl combines with coenzyme A forming acetyl coenzyme A
the acetyl group from coenzyme A combines with oxaloacetate to form citrate.
During a series of enzyme controlled steps, citrate is gradually converted back into oxaloacetate which results in the generation of ATP and release of carbon dioxide.
Dehydrogenase enzymes remove hydrogen ions and electrons and pass them to the coenzyme NAD, forming NADH. This occurs in both glycolysis and the citric acid cycle.
The hydrogen ions and electrons from NADH are passed to the electron transport chain on the inner mitochondrial membrane |
| describe ATP Synthesis/The Electron Transport Chain | the electron transport chain is a series of carrier proteins attached to the inner mitochondrial membrane
electrons are passed along the electron transport chain releasing energy.
This energy allows hydrogen ions to be pumped across the inner mitochondrial membrane.
The flow of these ions back through the membrane protein ATP synthase results in the production of ATP
Finally hydrogen ions and electrons combine with oxygen to form water. Oxygen is known as the final hydrogen/electron acceptor. |
| when and where does fermentation take place | in the absence of oxygen in the cytoplasm |
| describe fermentation in animal cells | pyruvate is converted to lactate in a reversible reaction. |
| describe fermentation in plants and yeast | ethanol and carbon dioxide are produced in an irreversible reaction. |
| how much atp is produced by fermentation compared to aerobic respiration | fermentation results in much less ATP (2 ATP) being produced than in aerobic respiration (38 ATP) |
