Chapter 3 Respiration Flashcards
What are oxidation reactions?
The loss of electrons
What are reduction reactions?
The gain of electrons
Relate structure of mitochondrion to function
Cristae - large SA for reactions
Matrix - contains enzymes for Krebs cycle
H+ carriers - needed for chemiosmosis/ETC
Permeable outer membrane - enables entry of pyruvate
What is oxidative phosphorylation?
The energy for making ATP comes from oxidation-reduction reactions and is released in the transfer of electrons along a chain of electron carrier molecules.
Why do plants respire?
Energy in the form of ATP is generated, which is needed for active transport and metabolic activity.
What is photophosphorylation?
The energy for making ATP comes from light and is released in the transfer of electrons along a chain of electron carrier molecules.
What is substrate-level phosphorylation?
When phosphate groups are transferred from donor molecules to ADP to make ATP with no oxygen required.
Define dehydrogenation
The removal of one or more hydrogen atoms from a molecule.
What is decarboxylation?
The removal of a carboxyl group from a molecule, releasing carbon dioxide
Define respiratory substrate
An organic substance that can be used for respiration
What are the 4 stages of aerobic respiration?
Glycolysis
Link reaction
Krebs cycle
Electron transport chain
Where does glycolysis occur?
In the cytoplasm of the cell.
What happens in glycolysis?
Glucose is phosphorylated by 2 molecules of ATP. This makes a hexose biphosphate. The fructose biphosphate splits into 2 triose phosphates that are then dehydrogenated. The hydrogen atoms transfer to coenzyme NAD producing reduced NAD. The 4 phosphates left over combine with 4 ADP’s to form 4 molecules of ATP. 2 molecules of pyruvic acid is also produced as a result of substrate-level phosphorylation.
What is the function of FAD in respiration?
FAD accepts H ions and then donate them to set up the H ion gradient in chemiosmosis
Where does the Link reaction occur?
Mitochondrial matrix
What does NAD do in respiration?
NAD accepts H ions and then acts as a source of H ions for the electron transport chain
What happens in the link reaction?
Pyruvate diffuses into the mitochondrial matrix. The pyruvate is dehydrogenated and the hydrogen is accepted by NAD to form reduced NAD. The pyruvate is also decarboxylated. The 2-carbon acetate group remaining from the glucose combines with coenzyme A to form acetyl coenzyme A.
Where does the Krebs cycle occur?
Mitochondrial matrix
Where is hexose biphosphate formed?
In glycolysis, in the cytosol outside the mitochondrion
What happens in the Krebs cycle?
Acetyl coenzyme A (2-C) combine with oxaloacetate (4-C acid) to form citrate (6-C acid). The citrate is dehydrogenated and decarboxylated. CO2 and NADH is formed with a 5-C acid. The 5-C acid is dehydrogenated and decarboxylated. 1 molecule of CO2, 2 molecules of NADH and 1 molecule of FADH2 are formed with a 4-C acid. Substrate level phosphorylation occurs and ATP is produced.
How many carbon atoms in acetate?
2
How many carbon atoms in citrate?
6
How is citrate made from acetate?
Citrate (6C) is made in the Krebs cycle by the combination of Acetyl coenzyme A (2C) and oxaloacetate (4C)
What is produced in the Krebs cycle?
1 ATP by substrate level phosphorylation
3 molecule of NADH
1 molecule of FADH2
2 molecules of CO2
Where does the electron transport chain (ETC) occur?
On the Cristae (inner membrane of mitochondria)
What happens in the ETC?
Hydrogen from reduced NAD and FAD splits into hydrogen ions and electrons. The electrons get passed from one carrier to the next. Each movement releases enough energy to power the pumping of H+ ions across the membrane into the inter-membrane space. An electrochemical gradient is created from the build up of H+ ions in the inter membrane space. H+ ions pass down the electrochemical gradient through a stalked particle containing ATP synthetase (chemiosmosis). Oxygen is the final acceptor of the hydrogen which produces water.
For each molecule of glucose entering glycolysis, how many NADH and FADH2 does the ETC receive?
10 NADH
2 FADH2
How much ATP is produced at the end of the Aerobic respiration?
2 net ATP molecules are made during glycolysis, 2 made during the Krebs cycle. During ETC for every 2 FADH2 makes 4 ATP molecules and for every 10 NADH makes 30 ATP molecules. Therefore, a total of 38 ATP molecules are synthesised.
What happens during anaerobic respiration in animals?
Glycolysis still occurs (glucose is broken down into pyruvate). The pyruvate becomes the hydrogen acceptor and is converted into lactate (lactic acid). This process is reversible, so that when oxygen becomes available again, the lactate can be broken down into carbon dioxide and water, releasing the energy it contains.
What happens during anaerobic respiration in microorganisms?
Glycolysis occurs (glucose is broken down into pyruvate). The pyruvate is decarboxylated and converted into CO2 and ethanal (a hydrogen acceptor). Ethanal is reduced by accepting hydrogen from NADH converting it into ethanol (in alcoholic fermentation). This is not reversible and ethanol cannot be broken down if oxygen is available, it accumulates in the cells and can rise to toxic concentrations.
What is the final electron acceptor in aerobic respiration?
Oxygen - H+ ions and electrons combine with oxygen to form water
Describe the process of anaerobic respiration in yeast
Glucose is broken down into pyruvate and ATP is produced. Pyruvate is converted to ethanal and then to ethanol.
Describe the process of anaerobic respiration in mammals
Glucose is broken down into pyruvate. Coenzyme NAD is reduced and ATP is formed. Pyruvate is converted to lactate (lactic acid) NAD is produced from reduced NAD
Explain the difference in relative energy values of carbohydrates, lipids and protein respiratory substrates.
The energy released is proportional to the relative numbers of hydrogen and oxygen atoms in the substrate, the more hydrogen for chemiosmosis, the greater the number of ATP that can be generated
Describe how the rate of respiration can be investigated practically
Rate of respiration can be investigated by measuring volume of Carbon Dioxide produced. By capturing and measuring CO2 the factors that increase CO2 production can also be investigated
Describe the evidence for chemiosmosis
Low pH in the inter membrane space
Outline the process of chemiosmosis
Reduced NAD & FAD donate H+ ions, which are pumped across the Cristae into the inter membrane space. This sets up a proton gradient. As the H+ ions diffuse back into the matrix via a stalked particle combined with ATP synthetase, ATP is formed
Compare anaerobic respiration in mammals and in yeast
Anaerobic respiration in yeast produces ethanol, in mammals they generate lactic acid.
Explain why the theoretical maximum yield of ATP per molecule of glucose is rarely achieved in aerobic respiration
Not all H+ ions are used in chemiosmosis (some may leak out)
ATP is also used in respiration and so the net ATP production will be less than the theoretical depending on how much ATP is used.
