1.7. Cellular Respiration Flashcards
Why is cellular respiration so important?
It yields energy and is connected to many other metabolic pathways.
What is ATP made of?
ADP and an inorganic phosphate.
How is the energy in ATP released?
Through breaking it into ADP and an inorganic phosphate.
What does phosphorylation mean?
The addition of a phosphate.
Describe the process of glycolysis.
Glycolysis is a series of enzyme controlled reactions which take place in the cytoplasm of the cell.
Glucose is broken down into pyruvate in the absence of oxygen. The phosphorylation of the intermediates of the process uses up two ATP molecules and is called the energy investment stage. In the energy pay-off stage dehydrogenase enzymes remove hydrogen ions which combine with NAD to form NADH. NADH then carried the hydrogens to the electron transport chain. In this stage four molecules of ATP are produced giving the whole process a net gain of 2 ATP.
What is the enzyme in glycolysis?
Phosphofructokinase.
Where in the cell do the citric acid cycle and the electron transport chain take place?
The mitochondria.
Where in the mitochondria does the citric acid cycle take place?
The matrix.
Describe the process of the citric acid cycle.
IF OXYGEN IS PRESENT, pyruvate progresses to the CAC. When pyruvate enters the cycle it is immediately broken down into an acetyl group and carbon dioxide. The acetyl group then reacts with coenzyme A to create acetyl coenzyme A. This then reacts with oxaloacetate to create citrate. The citrate then goes through a series of enzyme controlled steps which remove hydrogen ions (which are then transported to the electron transport chain) with the help of hydrogen acceptors NAD -> NADH and FAD -> FADH2. An ATP molecule is also produced. The cycle regenerates oxaloacetate which then goes on to react with more acetyl coenzyme A and the cycle starts again.
Describe the process of the electron transport chain.
NADH and FADH2 transport and pass on hydrogen ions and high energy electrons to the electron transport chain. This takes place on inner membranes of the mitochondria. The actual electron transport chain is a collection of electron acceptors on the inner mitochondrial membrane. NADH and FADH2 pass on their electrons which go down the chain of electron acceptors and release their energy. This energy then pumps the hydrogen ions across the inner mitochondrial membrane into the intermembrane space. The return flow of the hydrogen ions back into the matrix drives the enzyme ATP synthase resulting in the creation of ATP from ADP and an inorganic phosphate. This stage produces the most ATP. Oxygen accepts the hydrogen ions and creates water as a waste product.
What happens if there is no oxygen present to allow pyruvate to progress to the citric acid cycle?
Pyruvate undergoes fermentation resulting in the production of lactic acid. Fermentation does not release as much energy as cellular respiration as much of the energy stays in the lactic acid.
How do carbohydrates act as substrates for cellular respiration?
Molecules like starch and glycogen can be converted into glucose or one of the intermediates of glycolysis. Other sugars can do this too.
How do proteins act as substrates for cellular respiration?
Proteins can be broken down into amino acids which can be broken down into intermediates of either glycolysis or the CAC.
How do fats act as substrates for cellular respiration?
Fats can be broken down into glycerol and fatty acids which can be converted into intermediates of both glycolysis and the CAC.
