Section 5- Respiration Flashcards
What is respiration?
The release of energy from organic compounds.
What is the process of glycolysis in respiration?
2x ATP phosphorylate glucose into glucose phosphate and then hexose bisphosphate.
Destabilises glucose splitting into 2x triose phosphate.
TP oxidised into pyruvate, reducing NAD into reduced NAD.
ATP is also released.
What are the products of glycolysis?
2x ATP
2x reduced NAD
2x Pyruvate
After glycolysis, what is the process of anaerobic respiration?
In absence of oxygen, pyruvate stays in cytoplasm.
Reduced NAD must be recycled back to oxidised NAD so process of glycolysis can continue
What 4 stages is aerobic respiration divided into?
Glycolysis
Link Reaction
Krebs cycle
Oxidative phosphorylation
In short, what is glycolysis?
Splitting of glucose into 2x 3C pyruvate molecules
In short, what is the link reaction?
Pyruvate molecules enter into a series of reactions which lead to the formation of acetyl coenzyme A
In short, what is the Krebs cycle?
Intro of acetyl coenzyme A into cycle of oxidation-reduction reactions that produces ATP, reduced NAD, FAD.
In short, what is oxidative phosphorylation?
Use of electrons, associated with reduced NAD and FAD, released from Krebs cycle to synthesise ATP with water produced.
What is the link reaction?
Pyruvate is actively transported into the matrix of the mitochondria.
Pyruvate is oxidised to acetate.
3C pyruvate loses CO2 molecule and 2H.
H is accepted by NAD, forming reduced NAD.
2C acetate combines with coenzyme A, producing acetylcoenzyme A.
What are the products of the link reaction?
2x reduced NAD
2x CO2
2x Acetylcoenzyme A
What happens in the Krebs cycle?
2C acetlycoenzyme A combined with
4C oxaloacetate, producing 6C citric acid.
6C citric acid loses CO2 and H to give 4C oxaloacetate and ATP as a result of substrate level phosphorylation.
4C molecule now combines with acetylcoenzyme A to begin cycle again.
What are the products of the Krebs cycle?
2x reduced FAD 6x reduced NAD 2x ATP 4x CO2 (2x coenzyme A)
Why does the Krebs cycle perform an important role?
Produces hydrogen atoms which provides energy for oxidative phosphorylation
ATP produced provides metabolic energy for cell
How many carbons are there in a single molecule of pyruvate?
3
What is the 2 carbon molecule pyruvate is converted into during the link reaction?
Acetate
In what part of the cell does the Krebs cycle take place in?
Mitochondrial matrix
Where does oxidative phosphorylation occur?
Inner mitochondrial membrane/ Cristae
What is oxidative phosphorylation?
Energised electrons join electron transport chain and use energy to pump H+ ions across membrane generating electrochemical gradient.
Chemiosmosis occurs and H+ moves back into matrix by ATP synthase by facilitated diffusion.
Provides energy for ATP synthase to phosphorylate ADP into ATP.
Oxygen is final electron acceptor that forms water.
What is the role of oxygen in aerobic respiration?
Final electron acceptor in electron transport chain.
Produces water as by-product
What are 2 molecule that can be used as alternative respiratory substances?
Proteins (amino acids)
Lipids (glycerol and fatty acids)
What is the benefit of an electron transport chain rather than a single reaction?
Energy is released gradually
Less energy is released as heat
How can lipids act as an alternative respiratory substrate?
- Phosphorylation of glycerol- TP for glycolysis
- Fatty acid- acetate
a) acetate enters link reaction
b) H atoms produced for oxidative phosphorylation.
How can amino acids act as an alternative respiratory substrate?
Deamination produces:
- 3C compounds- pyruvate for link reaction
- 4C- 5C compounds- intermediated in Krebs cycle
What is the advantage of producing ethanol/ lactate during anaerobic respiration?
Converts NADH back into NAD so glycolysis can continue
What is the disadvantage of producing ethanol during anaerobic respiration?
Cells die when ethanol concentration is above 12%
Ethanol dissolves cell membranes
What is the disadvantage of producing lactate during anaerobic respiration?
Acidic, so decreases pH
Results in muscle fatigue
What is the disadvantage of producing lactate during anaerobic respiration?
Acidic, so decreases pH
Results in muscle fatigue
Why are the processes in the electron transfer chain also known as oxidative phosphorylation?
Movement of electrons along the chain is due to oxidation.
Energy from electrons combines inorganic phosphate and ADP to form ATP = phosphorylation.
What is one advantage of the highly folded membrane to the electron transfer chain?
Provides larger surface area of membrane incorporating coenzymes and electron carries that transfer the electrons along the chain
As part of which molecule does the oxygen taken into an organism leave after being respired?
Water molecule
What is the process of anaerobic respiration in plants?
Pyruvate loses molecule of CO2 and accepts hydrogen from reduced NAD to produce ethanol.
Pyruvate + reduced NAD -> ethanol + carbon dioxide + oxidised NAD
What is the word equation for anaerobic respiration in plants?
Pyruvate + reduced NAD
–>
ethanol + carbon dioxide + oxidised NAD
What is the word equation for anaerobic respiration in animals?
Pyruvate + reduced NAD -> lactate + oxidised NAD
Why is oxygen needed for the production of ATP on the cristae of the mitochondrion?
Oxygen is electron acceptor
Forms water with electrons and hydrogen atoms
ATP forms as electrons pass along transport chain
Why is converting pyruvate to ethanol important in allowing the continued production of ATP in anaerobic respiration?
Reduced NAD must be recycled back to oxidised NAD so glycolysis can continue
Why is ATP better than glucose or fatty acids as an immediate source of energy for cell metabolism?
Easily hydrolysed into ADP + Pi
Released in small quantities
No waste
What is the 2-carbon molecule that pyruvate is converted to during the link reaction?
Acetylcoenzyme A
In precisely what part of the cell does the Krebs cycle take place in?
Matrix of mitochondria
What is the important role of oxygen taken up by organisms in aerobic respiration?
Oxygen is final acceptor of electrons and hydrogen ions in electron transfer chain
Without it electrons would accumulate along chain and respiration would cease
As part of which molecule does the oxygen taken into an organism leave after being respired?
Water molecule
In the respiration practical, how is the rate of reaction calculated?
Rate= distance travelled (mm)/ time (s)
In the respiration practical, what does the tolerance of yeast cells mean to the different NaCl solutions?
Yeast is freely permeable
Yeast cell releases water when high NaCl concentration
Water is necessary for respiration, osmosis slows reproduction/ fermentation of yeast
What is the advantage of presenting results as a ratio?
So results are comparable of one another
As sample size may vary
What are the products of oxidative phosphorylation?
Water
ATP
NAD
What is the number of ATP molecules that are made directly ‘per turn’ of the Krebs cycle?
1
What is the number of NADH and FADH molecules that are formed in the Krebs cycle from one molecule of acetyl CoA?
NADH: 3
FADH: 1
Where are the reduced NAD and reduced FAD molecules reoxidised and what happens to the hydrogen atoms?
Inner mitochondrial membrane (cristae)
Hydrogen splits into protons and electrons
Proton gradient
Formation of water
During an experiment into respiration measuring the rate of oxygen consumption, why does the coloured liquid in tubing move towards tube with organism in?
Aerobic respiration causes release of CO2 which is absorbed
Oxygen needs to be taken in
Movement due to oxygen taken in decreasing pressure in tubing
What is the role of NAD in respiration?
NAD is a coenzyme
Transfer hydrogen from one molecule to another
When reduced it can oxidise other molecules
How could a colorimeter be used to estimate the rate of respiration in a test tube containing a yeast suspension and methylene blue?
Samples taken from test tube at regular intervals and analysed
Time it takes for the absorbance to drop to that of a yeast suspension without any methylene blue could be used to calculate rate of respiration
Respiration produces more ATP per molecule of glucose in the presence of oxygen than it does when oxygen is absent. Why?
Oxygen is final electron acceptor in oxidative phosphorylation
