Module 5: Respiration Flashcards
Name the 4 steps involved in aerobic respiration , in order
Glycolysis
Link reaction
Krebs cycle
Electron transport chain
Where in the cell does glycolysis occur?
-in the cytoplasm
Name and describe the first 2 steps of glycolysis
1)Phosphorylation-two phosphates released from two ATP molecules attach to a glucose molecule to form hexose bisphosphate
2)Lysis-hexose bisphosphate is an unstable molecule so is quickly split into two triose phosphate (TP) molecules
Name and describe the final 2 steps of glycolysis
3)Phosphorylation-another phosphate group is added to both the TP molecules forming two triose bisphosphate molecules
-these phosphate groups come from free phosphate ions in the cytoplasm
4)Dehydrogenation and formation of ATP-the two triose bisphosphate molecules are oxidised by the removal of hydrogen atoms to form two pyruvate molecules
-NAD coenzymes accept these removed hydrogens and form reduced NAD molecules
What happens at the same time as the two NAD coenzymes form reduced NAD molecules?
What is this production an example of , describe what this means?
four molecules of ATP are produced using phosphates from the triose bisphosphate molecules
substrate level phosphorylation-formation of ATP without the use of an electron transport chain
What is the overall net yield of ATP from glycolysis?
2 molecules of ATP , as 4 are produced but 2 were used to prime the process at the beginning
Where in the cell does the link reaction (oxidative decarboxylation) take place?
What is meant by the term oxidative decarboxylation?
in the mitochondria
the removal of hydrogen and carbon dioxide
Describe the first 2 steps of the link reaction
-start with pyruvate entering the mitochondrial matrix
1)Pyruvate enters the mitochondrial matrix by active transport via specific carrier proteins and then undergoes oxidative decarboxylation
-the removed hydrogen atoms are used to reduce NAD
2)The resulting 2 carbon acetyl group binds to coenzyme A to form acetylcoenzyme A
Describe the last 2 steps of the link reaction
3)Acetly CoA delivers the acetyl group to the Krebs cycle and reduced NAD is used in oxidative phosphorylation to synthesise ATP
4)Carbon dioxide removed will either diffuse out the cell and be removed as metabolic waste , or in autotrophic organisms it may be used as a raw material in photosynthesis
Where in the cell does the Krebs cycle take place?
also takes place in the mitochondrial matrix
Describe the first step of the Krebs cycle
-Acetyl CoA delivers an acetyl group to the Krebs cycle where it combines with a four carbon compound called oxaloacetate to form a six carbon molecule called citrate
Describe the second step of the Krebs cycle
-the citrate molecule undergoes decarboxylation and dehydrogenation producing one reduced NAD molecule and carbon dioxide , a five carbon compound is now formed
Describe the third and final step of the Krebs cycle
-the five carbon compound then undergoes decarboxylation and dehydrogenation which regenerates the oxaloacetate molecule and so the cycle continues
-this produces more carbon dioxide , two more molecules of reduced NAD , one molecule of reduced FAD , as well as ATP by substrate level phosphorylation
Where in the cells are electron transport chains present?
What atoms are delivered to these transport chains and what two molecules deliver them?
in the membranes of the cristae in the mitochondria
hydrogen atoms that have been collected by the coenzymes NAD and FAD
In oxidative phosphorylation , what do the hydrogen atoms dissociate into?
hydrogen ions and electrons
