Respiration Flashcards
What is respiration?
The process by which organic molecules are oxidised in a series of stages to synthesise ATP from ADP and Pi
The mitochondria in muscles contain many cristae. Explain the advantage of this (2)
Larger surface area for electron carrier system/oxidative phosphorylation
Provides more ATP/energy for muscle contraction
What are the 4 stages in aerobic respiration? (4)
Glycolysis
Link reaction
Krebs cycle
Oxidative phosphorylation (electron transport chain)
Where does glycolysis occur?
Cytoplasm of the cell
Where, in the mitochondria, does the link and Krebs reaction occur?
Matrix of mitochondria
Where, in the mitochondria, does oxidative phosphorylation occur?
Mitochondrial membranes
During respiration, what are the two ways in which ATP can be generated? (2)
Substrate-level phosphorylation
Oxidative phosphorylation
Where does substrate level phosphorylation occur? (1)
In glycolysis and Krebs cycle - ATP can be generated directly through energy released via respiration reactions
Where does oxidative phosphorylation occur?
At the electron transport chain
Describe glycolysis (6)
Glucose is activated by phosphorylation.
This requires the hydrolysis of 2 molecules of ATP to 2 x ADP to provide the 2 phosphates
Glucose phosphate (phosphorylated glucose ‘unstable’) then splits into 2 x triose phosphate
Triose phosphate is then oxidised to pyruvate.
This step involves the loss of H (via dehydrogenase enzyme) which reduces the Hydrogen carrier molecule NAD to NADH
ATP is also produced via substrate level phosphorylation
What does glycolysis of glucose yields? (3)
2 molecules of pyruvate
2 NET ATP directly by substrate level phosphorylation
2 reduced NAD
Why does glycolysis occur in the cytoplasm? (2)
Glycolysis enzymes are only found in the cytoplasm
Glucose too large to enter matrix of mitochondria
Describe the link reaction (5)
Pyruvate is actively transported into the mitochondrial matrix
Pyruvate is oxidised to acetate and the hydrogen removed is used to reduce the hydrogen carrier ‘NAD’ to form reduced
A molecule of CO2 is lost in this reaction (decarboxylation)
Acetate combines with a molecule of coenzyme A to form acetyl coenzyme A
No ATP produced directly in the link reaction
What are the products of link reaction? (3)
Reduced NAD
2 molecules of acetyl coenzyme A
CO2
Describe the Krebs cycle (5)
Acetyl coenzyme A combines with 4C molecule to form 6C compound
6C compound loses CO2 and hydrogen to convert to a 4C compound and 1xATP (via substrate-level phosphorylation)
FAD reduced
NAD reduced
What are the products of Krebs cycle? (3)
2 x CO2 produced
Some ATP produced directly by substrate level phosphorylation
3 x reduced NAD and 1 x FAD produced to be used in oxidative phosphorylation
How many times the Krebs cycle take place per molecule of glucose? (1)
2 times
Describe how oxidation takes place in glycolysis and in the Krebs cycle
Removal of hydrogen/dehydrogenation
By enzymes/dehydrogenases
H accepted by NAD/reduced NAD formed
In Krebs cycle, FAD used as well
Describe oxidative phosphorylation (9)
Reduced H carriers (reduced NAD and reduced FAD) are oxidised losing hydrogen
Electrons from H pass down a series of electron carrier proteins within the mitochondrial membranes in a series of redox reactions
As the electrons pass along the electron transport chain they lose energy, some of which is used to pump the H+ (proton) through the inner mitochondrial membrane into intermembrane space
Some of the energy is also lost as heat
The H+ diffuse down a proton gradient across the inner membrane into the matrix via ATP synthase enzymes and as they diffuse through the enzymes, enough energy is provided to form ATP
The electrons and H+ recombine with oxygen gas to form water
Oxygen is the final/terminal electron acceptor
Without oxygen removing H+ and electrons, there would be a ‘back up’ of electrons along the ETC and the process of cellular respiration will come to a halt
Water is a waste product of aerobic respiration. Describe how water is formed at the end of aerobic respiration. (2)
Oxygen is the terminal/final electron acceptor
Combines with electrons and protons (to form water)
Describe the roles of the coenzymes and carrier proteins in the synthesis of ATP (3)
NAD/FAD reduced / hydrogen attached to NAD/FAD;
H+ ions/electrons transferred from coenzyme to coenzyme/carrier to carrier (ETC on cristae of inner membrane)
Energy released (from electrons) through series of redox reactions;
Energy released used to pump H+/ protons into intermembrane space forming an electro-chemical gradient (of protons);
H+/ protons flow back through ATP synthase to produce ATP from ADP and phosphate
Describe how ATP is made in mitochondria. (6)
Substrate level phosphorylation / ATP produced in Krebs cycle
Krebs cycle/link reaction produces reduced coenzyme/reduced NAD/reduced FAD
Electrons released from reduced /coenzymes/ NAD/FAD
(Electrons) pass along carriers/through electron transport chain/through series of redox reactions
Energy released
ADP/ADP + Pi
Protons move into intermembrane space;
ATP synthase
Describe the events of oxidative phosphorylation
NAD/FAD reduced / hydrogen attached to NAD/FAD;
H+ ions/electrons transferred from coenzyme to coenzyme/carrier to carrier (ETC on cristae of inner membrane)
Energy released (from electrons) through series of redox reactions;
Energy released used to pump H+/ protons into intermembrane space forming an electro-chemical gradient (of protons);
H+/ protons flow back through ATP synthase to produce ATP from ADP and phosphate.
What are alternative respiratory substrates? (2)
Lipids and proteins
How do lipids act as alternative respiratory substrates? (3)
Glycerol is phosphorylated and converted to triose phosphate which enters glycolysis and Krebs cycle
Fatty acids are broken down into 2C fragments and converted into acetyl co A
Oxidation of fatty acids yields many hydrogen atoms to reduce NAD/FAD to be used in oxidative phosphorylation of ATP
How do proteins act as alternative respiratory substrates? (3)
Amino groups are removed (deamination)
Enter the respiratory pathway at different stages on the number of carbon atoms they contain
- 3C into pyruvate
- 4C and 5C into Krebs cycle intermediates
Explain how the amount of ATP is increased by reactions occurring inside a mitochondrion.
oxidation of/removal of electrons and H+
from pyruvate
acetyl CoA / 6 carbon compound; (credit oxidative decarboxylation)
substrate level production of ATP / ATP produced in Krebs cycle
production of reduced NAD / FAD (allow they take up hydrogen)
in matrix of mitochondria
electrons fed into electron transport chain / used in oxidative phosphorlation
(Electrons) pass along carriers/through electron transport chain/through series of redox reactions
Energy is released
Protons move into intermembrane space
ADP/ADP + Pi
ATP synthase
How many ATP molecules are produced in aerobic respiration (1)
Net 38 molecules of ATP per molecule of glucose
How many ATP molecules are produced in anaerobic respiration? (1)
2 molecules of ATP per molecule of glucose
What needs to be measured in a respirometer? (3)
The distance the ink/bubble moves
Over a fixed time period
Volume/diameter/cross-sectional area of tube
Give two reasons why the respirometer was left for 10 minutes when it was first placed in the water bath (3)
Equilibrium reached
Allow for expansion/pressure change in apparatus
Allow respiration rate of seeds to stabilise
Describe how anaerobic respiration occurs in animals (3)
Pyruvate is reduced to form lactate
Using H from the oxidation of NADH to produce NAD
So NAD regenerated and glycolysis can continue
Describe how anaerobic respiration occurs in plants and microorganisms (3)
Pyruvate is reduced to form ethanol and carbon dioxide
Using H from the oxidation of NADH to produce NAD
So NAD regenerated and glycolysis can continue
Describe the advantage of the electron transport chain (2)
Energy is released gradually
Less energy lost as heat
Disadvantage of producing ethanol during anaerobic respiration (1)
Ethanol dissolves cell membranes
Disadvantage of producing lactate during anaerobic respiration (2)
Acidic so decreases pH
Causes muscle fatigue
