1.7 - Cellular Respiration Flashcards
Process of respiration
Respiration is the process by which energy is released from food.
It occurs in all living cells.
What is respiration
Respiration is a metabolic pathway. It consists of a series of chemical reactions, each catalysed by specific enzymes.
What is the main substrate within respiration?
The main substrate within the respiration pathway is glucose.
What are the parts of the metabolic pathway involved in respiration?
- Glycolysis
- Citric acid cycle
- Electron transport chain
What is phosphorylation?
Phosphorylation is an enzyme control process by which a phosphate group is added to a molecule.
Example of phosphorylation:
When low energy ADP and Pi combine to form high energy ATP
What is glycolysis
Glycolysis is the first stage of respiration which takes place in the cytoplasm and does not require oxygen.
Respiration metabolic pathway oxygen requirements
Glycolysis - no
Citric acid cycle - yes
Electron transport chain - yes
What does glycolysis involve?
Glycolysis involves the breakdown of glucose into two pyruvate molecules.
Glycolysis involves 2 phases:
- an energy investment phase
- an energy payoff stage
Glycolysis - production of pyruvate
The production of pyruvate from glucose involves the production of several intermediate molecules.
Glycolysis- what is required for the phosphorylation of glucose
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 payoff stage and results in a net gain of ATP.
What happens during the energy payoff stage?
During the energy payoff phase of glycolysis (and in the citric acid cycle), dehydrogenase enzymes remove hydrogen ions and electrons and pass them to the coenzyme NAD, forming NADH.
What enzyme removes hydrogen ions and electrons and where do they pass them
Dehydrogenase enzymes remove hydrogen ions and electrons and pass them to the coenzyme NAD, forming NADH.
In what conditions is pyruvate broken down into an acetyl group?
Aerobic (oxygen present)
What happens to pyruvate in aerobic conditions?
In aerobic conditions, pyruvate is broken down into an acetyl group.
Once pyruvate has been broken down into an acetyl group what happens to the acetyl group?
The acetyl group then combines with coenzyme A to form acetyl coenzyme A.
What is the next stage of respiration after glycolysis?
Citric acid cycle
What needs to be present for the citric acid cycle to take place?
The citric acid cycle only occurs of oxygen is present.
Where does the citric acid cycle take place in the cell?
The citric acid cycle occurs in the matrix of the mitochondria. 
What is the citric acid cycle controlled by?
The citric acid cycle is controlled by enzymes including dehydrogenases. 
What happens to the acetyl group in the citric acid cycle?
In the citric acid cycle, the acetyl group from acetyl coenzyme A combines with oxaloacetate to form citrate.
What happens to citrate in the citric acid cycle?
During a series of enzyme controlled steps, citrate is gradually converted back into oxaloacetate which results in the generation of ATP and releases carbon dioxide.
What do dehydrogenase enzyme is do during the citric acid cycle?
Dehydrogenase enzymes remove hydrogen ions and electrons and pass them to the coenzyme NAD, forming NADH.
What happens to the hydrogen ions and electrons from NADH?
The hydrogen ions and electrons from NADH are passed to the electron transport chain (on the inner mitrochondrial membrane).
What is the last stage of glycolysis?
The electron transport chain is the last stage of respiration requires oxygen to be present.
Where does the electron transport chain take place
The electron transport chain takes place in the inner membrane of the mitochondria.
What is the ETC?
The electron transport chain is a series of carrier proteins attached to the inner mitochondrial membrane.

What stage is most ATP made
The electron transport chain is the final stage of respiration where most of the ATP is made
How is ATP made in the ETC
ATP is made using the energy from the electrons which have been removed during glycolysis and the citric acid cycle.
ETC: ATP synthesis process
- Electrons are passed alone electron transport chain releasing energy.
- this energy allows hydrogen ions to be pumped across the inner mitochondrial membrane.
- The flow of hydrogen ions back through the membrane protein ATP synthase results in the production of ATP.
- finally the hydrogen ions and electrons combine with oxygen to form water.
What is the final hydrogen acceptor in the ETC?
Oxygen is the final hydrogen acceptor of the electron transport chain.
What is the role of ATP in the transfer of energy?
ATP is used to transfer energy to cellular processes which require energy.
Cellular process that require energy
Muscle cell contraction
Transmission of nerve impulses
Cell division
Protein synthesis
