5.7 - E - Respiration Flashcards
Define respiration
The release of chemical potential energy from organic molecules
inside mitochondria
What does ATP stand for?
Adenosine triphosphate
What are 7 uses of ATP?
Active Transport Endocytosis & exocytosis Synthesis of large molecules (collagen, enzymes, antibodies) DNA replication Cell division Movement Activation of chemicals
What type of molecule is ATP?
Phosphorylated nucleotide
How much energy is released when either the first or second phosphate group of ATP are removed?
How much energy is released when the third phosphate group of ATP is removed?
- 5 kJ
14. 2 kJ
What type of reaction occurs when a phosphate group is removed from ATP?
Hydrolysis - this requires water
List the full name of ATP when it has: 3 phosphate groups, 2 phosphate groups, 1 phosphate group, No phosphate groups
Adenosine triphosphate
Adenosine diphosphate
Adenosine monophosphate
Adenosine
What is adenosine monophosphate the same as?
RNA
What enzyme catalyses the removal of phosphate groups from ATP?
ATPase
Where does the energy that is released in the hydrolysis of ATP come from?
The chemical energy stored in glucose
Describe the role of coenzymes in respiration
They are enzymes needed to assist other enzymes in a reduction or oxidation reaction (because they can pick up and lose hydrogen atoms)
List the 3 coenzymes used in respiration
NAD - Nicotinamide Adenine Dinucleotide
CoA - Coenzyme A
FAD - Flavine Adenine Dinucleotide
What does RNA need to become ATP?
2 phosphate groups
Define energy
The capacity to do work
What is potential energy?
The energy that is stored in complex organic molecules.
Eg: fats, carbohydrates, and proteins.
State and explain the 2 types of metabolic reactions
Anabolic reactions - metabolic reactions where large molecules are synthesised from smaller molecules.
Catabolic reactions - metabolic reactions involving the hydrolysis of large molecules to smaller ones.
Why is ATP referred to as the universal currency of energy?
It occurs in all living cells and is a source of energy that can be used by cells in small amounts.
Why is all the chemical energy released during respiration not transferred to ATP?
It’s lost as heat
Why does each cell require the structures associated
with respiration?
ATP cannot cross the plasma membrane
What are the 4 main processes in aerobic respiration?
Glycolysis
Link reaction
Krebs cycle
Oxidative phosphorylation
Define glycolysis
The first stage in respiration, a 10 stage metabolic biochemical pathway that occurs in the cytoplasm or all living things that respire that converts glucose to pyruvate.
What coenzyme helps some enzymes in glycolysis?
NAD - Nicotinamide Adenine Dinucleotide
What are the 3 main stages in glycolysis?
Phosphorylation of glucose to hexose bisphosphate.
Splitting each hexose bisphosphate molecule into 2 triose phosphate molecules.
Oxidation of triose phosphate to pyruvate.
When do enzymes require coenzymes?
When catalysing oxidation and reduction reactions as they accept hydrogen atoms removed during oxidation.
What is NAD and what does it do throughout glycolysis?
It’s a non-protein molecule that helps dehydrogenase enzymes to carry out oxidation reactions.
How is NAD synthesised?
In living cells from nicotinamide (vitamin B3), ribose, adenine and 2 phosphoryl groups.
What happens in the first main stage of glycolysis (phosphorylation)?
One molecule of ATP is hydrolysed the Pi is added to glucose to make hexose monophosphate.
Another molecule of ATP is hydrolysed and the Pi is added to the hexose phosphate to form a molecule of hexose bisphosphate.
The energy from the hydrolysed ATP molecules activated the hexose sugar and prevents it from being transported out of the cell.
Explain the structure of hexose bisphosphate
It’s a sugar that has one phosphate group at carbon atom number 1 and another at carbon atom number 6.
Explain the second main stage in glycolysis (the splitting of the hexose bisphosphate)
Each molecule of hexose bisphosphate is split into two 3-carbon molecules, triose phosphate, each with a phosphate group attached.
What happens in the third main stage in glycolysis (the oxidation of triose phosphate to pyruvate)?
Although this process is anaerobic, it involves oxidation, because it involves the removal of hydrogen atoms from substrate molecules:
Dehydrogenase enzymes, aided by the coenzyme NAD, remove hydrogens from triose phosphate.
The 2 molecule of NAD accept the hydrogen atoms (protons and electrons) and become reduced.
Describe the products at the end of glycolysis, in relation to the original glucose
At this stage of glycolysis, 2 molecules of NAD are reduced for every molecule of glucose undergoing this process. Also at this stage, four molecules of ATP are made for every 2 triose phosphate molecules undergoing oxidation.
For each molecule of glucose, at the end of glycolysis there are:
2 molecules of ATP; 4 have been made, but 2 were used to ‘kick start’ the process, so the net gain is 2 ATP molecules.
2 molecules of reduced NAD (NADH).
2 molecules of pyruvate.
What type of respiration includes the 4 stages of respiration?
Aerobic (glycolysis happens before the 2 types separate that require different stages)
How are the 4 ATPs made in the third stage of glycolysis?
Substrate level phosphorylation
What does the outer membrane of mitochondria contain? What are these used for?
Protein channels or carriers to allow pyruvate to pass through
Explain the inner membrane of mitochondria
Has a different membrane structure and is much less permeable to small ions (e.g. hydrogen ions)
Folded into cristae to give a large surface area
Contains electron carriers and ATP synthase enzymes
What happens in the mitochondrial matrix?
What is found in there?
This is where the link reaction and the Krebs cycle take place.
Enzymes
Molecules of coenzyme NAD
Oxaloacetate (4C compound in the link reaction)
Mitochondrial DNA
Mitochondrial ribosomes
How is pyruvate transported into mitochondria?
Pyruvate is transported across the mitochondrial envelope using a
transport protein called the pyruvate‐H+ symport.
Where does glycolysis occur?
Cytoplasm
List the 5 stages of the link reaction
- Pyruvate is decarboxylated (carboxyl group removed)
This is the cause of some CO2 production. - It is also dehydrogenated (H atoms removed) to produce an acetyl group.
- These reactions are catalysed by a multi‐enzyme complex called
pyruvate dehydrogenase. - The acetyl group combines with coenzyme A to become acetyl CoA.
- The coenzyme NAD becomes reduced.
What word equation is used to sum up glycolysis?
glucose + 2NAD + 2ATP ‐‐> 2 pyruvate + 4ATP + 2NADH
What word equation is used to sum up the link reaction?
2 pyruvate + 2NAD + 2CoA ‐‐> 2 acetyl CoA + 2NADH + 2 CO2
List 6 similarities between mitochondria and chloroplasts
Both have inner and outer membranes and intermembrane space.
Both are fluid-filled (matrix, stroma).
Folding of inner membrane.
Circular DNA, proteinsynthesis (ribosomes).
Found in plants.
Electron transport chains (proteins in membranes)
Define decarboxylation
Removal of a carboxyl group from a substrate molecule
Define dehydrogenation
Removal of hydrogen atoms from a substrate molecule
Define substrate-level phosphorylation
Production of ATP from ADP and Pi during glycolysis and the Krebs cycle
What are cristae?
Inner highly-folded mitochondrial membrane
How is pyruvate transported and where to after glycolysis?
Across the outer and inner mitochondrial membranes via a specific pyruvate-H+ symport into the matrix.
Define decarboxylation
Removal of a carboxyl group from a substrate molecule
Define dehydrogenation
Removal of hydrogen atoms from a substrate molecule
Define substrate-level phosphorylation
The production of ATP from ATP and Pi during glycolysis and the Krebs cycle
What enzyme is a part of the link reaction?
Pyruvate dehydrogenase
What is the symbol equation of the link reaction?
2 pyruvate + 2NAD + 2CoA -> 2CO2 + 2 NADH + 2 acetyl CoA
Where do both the Krebs cycle and the link reaction take place?
The mitochondrial matrix
What 2 enzymes are used in the Krebs cycle?
NAD and FAD
What is the Krebs cycle?
A series of enzyme-catalysed reactions that oxidise the acetate from the link reaction to 2 molecules of carbon dioxide, while conserving energy by reducing the coenzymes NAD and FAD.
How many turns of the Krebs cycle per molecule of glucose?
2 (1 turn per pyruvate)
Explain the steps of the Krebs cycle
The acetyl group released from acetyl CoA combines with a 4-carbon compound, oxaloacetate, to form a 6-carbon compound, citrate.
Citrate is decarboxylation and dehydrogenated, producing a 5-carbon compound, one molecule of carbon dioxide and one molecule of NADH.
This 5-Carbon compound is further decarboxylation and dehydrogenated, producing a 4-carbon compound, one molecule of carbon dioxide and one molecule of reduced NAD.
This 4-Carbon compound combines temporarily with, and is then released from, coenzyme A. At this stage, substrate-level phosphorylation takes place, producing one molecule of ATP.
The 4-Carbon compound is dehydrogenated, producing a different 4-carbon compound and a molecule of reduced FAD.
Rearrangement of the atoms in the 4-carbon molecule, catalysed by an isomerase enzyme, followed by further dehydrogenation, regenerate a molecule of oxaloacetate, so the cycle can continue.
How many turns of the Krebs cycle are there for every molecule of glucose?
2
How many molecules are made in the link reaction of: NADH, FADH, Carbon dioxide, ATP, Acetyl CoA
2 0 2 0 2
How many molecules are made in 2 turns of the Krebs cycle of: NADH, FADH, Carbon dioxide, ATP
6
2
4
2
How many molecules are made in glycolysis of: NADH, FADH, Carbon dioxide, ATP
2
0
0
2
Define chemiosmosis
The flow of protons down their concentration gradient across a membrane through a channel associated with ATP synthase
Define oxidative phosphorylation
The production of ATP in the presence of oxygen using energy released in the electron transport chain. It is the last stage in aerobic respiration.
Where does oxidative phosphorylation take place?
Takes place in the mitochondria across the inner membrane. The
christae provides a large surface area for electron carrier proteins
and ATP synthase.
What 3 things happen in oxidative phosphorylation?
NADH and FADH are reoxidised when they deliver their hydrogen atoms to the electron transport chain.
The hydrogen atoms released from the reduced coenzymes split into protons and electrons.
The protons go into solution in the mitochondrial matrix.
Explain what NADH does and causes in oxidative phosphorylation
NADH binds to complex I. Releases an H atom as H+ & e-. NADH oxidsed to NAD. A total of 10H+ can be pumped from matrix to intermembrane space using energy from e- passing along the electron transport chain. (4 from I, 4 from III and 2 from IV)
Explain what FADH does and causes in oxidative phosphorylation
FADH binds to complex II. Releases H atom as H+ & e-. FADH oxidsed to FAD. A total of 6H+ can be pumped from matrix to intermembrane space using energy from e- passing along the electron transport chain. (4 from III, 2 from IV)
Explain the role of the electron transport chain in oxidative phosphorylation
Electrons from H atoms pass along the electron carriers. As the
electrons pass along the chain some of their energy is used to
pump protons into the intermembrane space. Oxygen is the final
electron acceptor.
What is the symbol equation at the end of oxidative phosphorylation (ATP synthase)
4H+ + 4e- + O2 -> 2H20
What happens after the protons have been pumped across the inner membrane of the cytoplasm in oxidative phosphorylation?
Protons build up in the intermembrane space creating a proton
gradient this is due to the outer membrane low permeability to
H+. This generates a chemiosmotic potential also known as a proton motive force (pmf).
What is the net gain of ATP per molecule of glucose in: Glycolysis The link reaction The Krebs cycle Oxidative phosphorylation Total
2 0 2 28 32
What happens if oxygen is absent in respiration? 5 points
Oxygen cannot act as the final electron acceptor. Protons diffusing through channels associated with ATP synthase are not able to combine with electrons and oxygen to form water.
The conc. of protons increases in the matrix and reduces the proton gradient across the inner mitochondrial membrane.
Oxidative phosphorylation ceases.
Reduced NAD and reduced FAD are not able to unload their hydrogen atoms and cannot be reoxidised.
The Krebs cycle stops, as does the link reaction.
What are the 2 ways NADH can be reoxidised without oxygen?
What organisms use which?
Where do they take place?
Ethanol fermentation pathway (A.K.A. alcoholic fermentation) - fungi, plants
Lactate fermentation pathway - mammals
Cytoplasm
Explain the ethanol fermentation pathway
Each molecule of pyruvate produced during glycolysis is decarboxylated and converted into ethanal. This is catalysed by pyruvate decarboxylase, which has a coenzyme, thiamine disphosphate, bound to it.
The ethanal accepts the hydrogen atoms from NADH, becoming reduced to ethanol. This is catalysed by ethanol dehydrogenase.
In the process, NADH is reoxidised and made available to accept more hydrogen atoms from triose phosphate, thus allowing glycolysis to continue.
Explain what happens in the lactate fermentation pathway
Pyruvate, produced by glycolysis, accepts hydrogen atoms from NADH, also made during glycolysis. The enzyme lactate dehydrogenase catalyses this. There are 2 outcomes:
Pyruvate is reduced to lactate.
The reduced NAD becomes reoxidised.
The reoxidised NAD can accept more hydrogen atoms from triose phosphate during glycolysis, and glycolysis can continue to produce enough ATP to sustain muscle contraction for a short period.
Explain the fate of lactate
The lactate produced in the muscle tissues is carried away from the muscles in the blood to the liver. When more oxygen is available, the lactate may be either:
Converted to pyruvate, which may enter the Krebs cycle via the link reaction.
Recycled to glucose and glycogen.
If lactate were not removed from the muscle tissues, the pH would be lowered and this would inhibit the action of many of the enzymes involved in glycolysis and muscle contraction.
What is a facultative anaerobe?
Give an example
Yeast
An organism that makes ATP by aerobic respiration if oxygen is present, but is capable of switching to fermentation if oxygen is absent.
What is a respiratory substrate?
An organic substance that can be oxidised by respiration, releasing energy to make molecules of ATP.
If glucose is not present what other respiratory substrates can be
respired to produce molecules of ATP?
Lipids - Hydrolysed
Proteins - deamination in the liver
Other carbohydrates: glycogen, starch - hydrolysed
Fructose, Galactose - Isomerase
What parts of the body can only use glucose in respiration?
The brain,
Red blood cells
What can glucose be stored as in:
Plants?
Animals?
Why is this a good thing?
Starch.
Glycogen.
It can be easily hydrolysed to become glucose and enter glycolysis.
What can lipids be hydrolysed into?
Glycerol and fatty acids
What can glycerol be converted to?
Why are fatty acids good for respiration?
TP.
They contain many H atoms so are a good source of H+ & e- for oxidative phosphorylation.
Explain beta oxidation
Fatty acids combine with CoA, this requires ATP. The combined
fatty acid and CoA can then enter the matrix from the cytoplasm.
Fatty acids, such as Palmitic Acid is broken down into 2C Acetyl
CoA molecules this produces 1x NADH & 1x FADH.
CoA is released and acetyl group can enter the Krebs cycle.
How are proteins useful in respiration?
Excess amino acids, released after the digestion of proteins, are deamination in the liver. Deamination of an amino acid involves removal of the amino group and its subsequent conversion to urea that is removed via the kidney. The rest of the amino acid molecule, a keto acid, enters the respiratory pathway as pyruvate, acetyl CoA or a Krebs cycle acid such as oxaloacetic acid. During starvation protein from muscles can be hydrolysed to AA for respiration.
What are the energy values of the 3 respiratory substances?
Glucose - 15.8kJg-1
Lipid - 39.4kJg-1
Protein - 17.0kJg-1
The more hydrogen atoms there are in the structure of a molecule…
The greater the energy value
What is the respiratory quotient?
What is the equation?
The ratio of the volumes of oxygen absorbed and carbon dioxide given off in respiration, it can indicate which respiratory substrate is being respired.
RQ = CO2 produced / O2 consumed
What does it mean if the RQ value > 1 ?
Some anaerobic respiration has taken place
State 4 factors which can effect the rate of respiration
Temperature
Substrate Concentration
Type of Respiratory Substrate
Availability of Oxygen
Describe the steps in how to use a respirometer
Place equal volumes of KOH solution in 2 boiling tubes.
Place a gauze basket just above the solution in each tube.
Place woodlice into one tube and glass beads into the other.
Connect a manometer to the 2 tubes.
Close the screw clip.
Use the syringe to make the fluid in the manometer level.
Note the manometer level and start the clock.
Read off the manometer fluid level at regular intervals.
