Respiration and ATP Flashcards
Respiration can be described as a catabolic process, explain what this means
Catabolic processes involve the breakdown of complex molecules into simpler ones, releasing energy. In respiration, large organic molecules like glucose are broken down to produce energy.
Define aerobic and anaerobic respiration
-Aerobic Respiration: Occurs in the presence of oxygen, producing carbon dioxide, water, and a large amount of ATP.
-Anaerobic Respiration: Occurs in the absence of oxygen, producing lactic acid (in animals) or ethanol and carbon dioxide (in yeast and some bacteria).
What is the citric acid cycle also known as?
The citric acid cycle is also known as the Krebs cycle.
Aerobic respiration can theoretically synthesize 38 ATP molecules from 1 glucose molecule, explain why this is a theoretical number
Some energy is used in processes like moving molecules across membranes. In reality, about 30-32 ATP molecules are typically produced due to these energy costs.
Name the final electron acceptor
Oxygen
Name the location of the following: glycolysis, link reaction, Krebs cycle, and chemiosmosis
Glycolysis: Cytoplasm.
Link Reaction: Mitochondrial matrix.
Krebs Cycle: Mitochondrial matrix.
Chemiosmosis (Oxidative Phosphorylation): Inner mitochondrial membrane (cristae).
How many ATP molecules can be synthesized from 1 glucose molecule in anaerobic respiration?
In anaerobic respiration, 2 ATP molecules are synthesized from 1 glucose molecule.
State the location of anaerobic respiration
Anaerobic respiration takes place in the cytoplasm of the cell.
If glucose is not available, name 2 alternative respiratory substrates that could be used
Fats (fatty acids)
Proteins (amino acids)
What are the 5 roles of ATP?
- Secretion - packaging and transport of secretory products into vesicles in cells
- Active Transport - allows molecules to move against the concentration gradient
- Metabolic processes - to synthesise large complex molecules from smaller ones
- Movement - muscle contraction
- Nerve Transport - sodium-potassium pump across the axon memebrane
Draw and label an ATP molecule
Adenine (hexagon connected to a pentagon or a rectangle)
Ribose Sugar (pentagon)
3 inorganic phosphate groups (3 circles connected in a straight line)
Draw and label an ADP molecule
Adenine
Ribose Sugar
2 inorganic phosphate groups
What is ATP?
ATP is the cell source of energy
Stands for Adenosine Triphosphate
ATP is a nucleotide
What does ADP stand for?
Adenosine Diphosphate
How is energy stored and released in ATP?
stored in the bonds of the 2nd and 3rd phosphate groups
breaking this bond releases energy
when cells have enough energy they store it by adding a phosphate group to ADP
How is ATP broken down?
the bond between second and third phosphate groups
energy released for cellular processes = exergonic reaction
ATP molecule therefore is hydrolysed into ADP and Pi
ATPase catalyses this reaction
How much energy is released for every mole of ATP hydrolysed?
30.6kJ
How is ATP made?
ADP + Pi -> ATP
this is an endergonic reaction
addition of phosphate to ADP is phosphorylation
What are the differences between glucose and ATP as energy stores?
ATP
- only ATPase is required (one enzyme)
- hydrolysis is a single step reaction and there is an instant release of energy
- releases small amounts of energy when and where it is needed
Glucose
- many enzymes are needed to release energy
- reaction involves many intermediates and takes longer for energy to be released
- glucose releases energy in large amounts and it’s all used at once
What is meant by metabolism?
Metabolism refers to all the reactions of the organism
What is respiration?
A catabolic process involving a series of enzyme-catalysed reactions in cells, where energy-rich substrates, e.g. glucose and fatty acids, are broken down to release energy
- some energy is trapped as chemical energy (ATP) and some is released as heat energy
What is aerobic respiration?
the release of large amounts of energy, made available as ATP, from the breakdown of molecules, with oxygen as the terminal electron acceptor
What is anaerobic respiration?
the breakdown of molecules in the absence of oxygen, releasing relatively little energy, making a small amount of ATP by substrate-level phosphorylation
What is oxidative phosphorylation?
Occurs in mitochondrial inner membrane in aerobic respiration
energy for forming the ATP comes from the oxidation-reduction reactions and is released in the transfer of electrons along a chain of electron carrier molecules
What is photophosphorylation?
occurs in the thylakoid membrane in the light dependent stage of photosynthesis
energy to form ATP comes from light and is released in the transfer of electrons along a chain of electron carrier molecules
What is substrate-level phosphorylation?
Occurs when phosphate groups are transferred from donor molecules or when enough energy is released for a reaction to bind ADP to inorganic phosphate
What are the is the enzymes and the reaction called when CO2 is removed from respiratory substrates?
decarboxylase enzymes
decarboxylation
What are the enzymes and reaction called when hydrogen is removed from respiratory substrates?
dehydrogenase enzymes
dehydrogenation
What are the 2 hydrogen carriers used in respiration?
NAD and FAD
these transport hydrogen to the final stage of aerobic respiration
when bound to a hydrogen atom we say these molecules have been reduced
What are the four stages of aerobic respiration?
Glycolysis
Link Reaction
Krebs Cycle
Chemiosmosis and Oxidative Phosphorylation
What are the two steps in anaerobic respiration?
Glycolysis
Fermentation
Where does glycolysis take place and why?
Cell cytoplasm because glucose can’t pass through mitochondrial membranes
Draw out the reaction of glycolysis
Glucose (6C)
2xATP -> 2xADP
(Fructose/glucose/hexose) Bisphosphate (6C)
splits
2xTriose Phosphate (3C)
dehydrogenation (2NAD to 2NADH) and subrate-level phosphorylation (4ADP to 4ATP)
2xPyruvate/pyruvic acid (3C)
What are the products of glycolysis per glucose molecule?
2 pyruvate
2 NADH
2 (net) ATP
Is glycolysis aerobic or anaerobic?
Anaerobic as there is no oxygen present
Why can’t cells rely on glycolysis as a long-term ATP generating system?
NAD would run out as NAD is regenerated at the end stages of respiration
Where does fermentation occur?
cell cytoplasm
Why does fermentation occur?
NAD needs to be regenerated (oxidise NAD so glycolysis can continue)
What does anaerobic mean?
Reactions where no oxygen is required
What does fermentation mean?
an anaerobic process that follows glycolysis to continue ATP production until oxygen is available
What are the 2 types of fermentation?
Lactic acid fermentation
Alcoholic fermentation
What happens in lactic acid fermentation?
- series of anaerobic reactions in which pyruvate uses NADH to form lactic acid and NAD
- NAD is then recycled in glycolysis and fermentation
- recycled NAD allows 2 ATP to form from glycolysis and 0 ATP from lactic acid fermentation
- lactic acid builds up in muscles and causes fatigue
- when O2 is available lactic acid leaves the muscle and goes to the liver to be converted back to pyruvate
What happens in alcoholic fermentation?
- an anaerobic process in which cells convert
pyruvate into CO2 and ethanol - pyruvate is broken down to a 2C, by releasing a CO2 molecule
- electrons are transferred from NADH to the carbon molecule producing ethanol
- yields 2 net ATP from glycolysis
- used by fungus and bacteria to release alcohol and carbon dioxide
What is the efficiency of anaerobic respiration?
(2 x 30.6) / 2880 then x100 = 2.1%
What is the equation for glycolysis?
Glucose + 2NAD + 2ADP + 2Pi -> 2Pyruvate + 2NAHD + 2ATP + heat energy
Why is ATP need for glycolysis?
Needed to phosphorylate glucose
What is the general formula for respiration?
C6H12O6 + 6O2 -> 6O2 + 6H2O
What is the problem with having no oxygen in respiration?
NADH and FADH cannot be reoxidised and therefore made available to pick up hydrogen
What factors of mitochondria support the endosymbiotic theory?
Have small ribosomes and circular DNA which are features of prokaryotes
the presence would be explained by endosymbiotic theory of cell evolution
mitochondria make some of their own protein and they need the DNA and ribosome to do so
Explain the features of the mitochondrial outer membrane
- it has a protein-to-phospholipid bilayer similar to the eukaryotic plasma membrane
- contains numerous integral membrane proteins called porins that contain a relatively - - large internal channel
- large molecules can only traverse the outer membrane by active transport
- a ‘smooth’ outer membrane
Explain the features of the mitochondrial inner membranes
Contains proteins with 3 types of functions:
1. Proteins that carry out the oxidation reactions of the respiratory chain (electron carriers for example)
2. ATP synthase which uses the H+ gradient to make ATP
3. Specific transport proteins that regulate passage of metabolites into and out of the matrix
Inner membrane does not contain porins and is highly impermeable
Where does the link reaction take place?
Mitochondrial Matrix
Draw and describe the link reaction?
Pyruvate (3C)
Dehydrogenation (NAD to NADH) and decarboxylation (CO2) formed
Acetate (2C)
Coenzyme A
Acetyl CoA (goes into Krebs Cycle)
Where does the Krebs Cycle take place?
Mitochondrial Matrix
Draw the Krebs Cycle
4C molecule
Acetyl CoA -> Coenzyme A
6C molecule
Decarboxylated (CO2) and dehydrogenation (NAD to NADH)
5C molecule
Decarboxylation (CO2), dehydrogenation (NAD to NADH) and substrate-level phosphorylation (ADP + Pi -> ATP)
4C molecule
Dehydrogenation (FAD to FADH)
4C molecule
Dehydrogenation (NAD to NADH)
4C molecule (the start again)
What are the enzymes involved in the Krebs Cycle and Link reaction for respiration?
- decarboxylase removed CO2 from intermediates (twice in Krebs and once in Link)
- dehydrogenase removed hydrogen from intermediates oxidising them and reducing NAD or FAD
What does the link reaction produce per glucose molecule in respiration?
2 NADH
2 CO2
2 Acetyl CoA (therefore krebs has to turn twice)
What does the Krebs cycle produce per glucose molecule in respiration?
2 ATP
6 NADH
2 FADH
4 CO2
(Krebs cycle must happen twice for each glucose molecule)
What is a Coenzyme?
A molecule required by an enzyme in order to function (not an enzyme)
Why is it important that the 4C molecule in the Krebs Cycle is regenerated?
AcCoA would accumulate otherwise
- Krebs cycle releases hydrogen atoms which is then used in oxidative phosphorylation to provide energy to make ATP
Where does oxidative phosphorylation and chemiosmosis take place?
inner mitochondrial membrane
Chemiosmosis/Oxidative Phosphorylation: Final Electron Acceptor (1)
- NADH and FADH are oxidised when they donate hydrogen atoms, which split into a proton and an electron
- the electrons are passed along the ETC and then donated to molecular oxygen, the final electron acceptor
2H+ + 2e- + 1/2O2 -> H2O - H+ stays in solution of matrix and removed from solution to reduce it to water
Chemiosmosis/Oxidative Phosphorylation: Chemiosmosis (2)
- As e- flow along the ETC energy is released and used to pump H+ from matrix into intermembrane space
- builds up proton gradient (also a pH and electrochemical gradient)
- protons flow then flow from inter-membrane space into matrix via ATP synthase which generates ATP (ADP + Pi -> ATP)
Chemiosmosis/Oxidative Phosphorylation: Oxidative phosphorylation (3)
- formation of ATP in the presence of oxygen which is the final electron acceptor
- as H+ flow through ATP synthase enzyme, they drive the rotation of part of the enzyme and join ADP and Pi to form ATP
How many proton pumps does each electron acceptor power?
FADH -> 2 pumps (2ATP)
NADH -> 3 pumps (3ATP)
What is the theoretical maximum number of ATP molecules that can be produced from one glucose in respiration?
38 molecules
How much ATP is produced in glycolysis per glucose molecule in respiration?
oxidative phosphorylation (producing NADH/FADH) = (2 x 3) 6
substrate-level phosphorylation = 2
total = 8
How much ATP is produced in the link reaction per glucose molecule?
oxidative phosphorylation (producing NADH/FADH) = (2 x 3) 6
substrate-level phosphorylation = 0
total = 6
How much ATP is produced in the krebs cycle per glucose molecule?
oxidative phosphorylation (producing NADH/FADH) = 22
substrate-level phosphorylation = 2
total = 24
How many molecules of ATP are made in the final stage of aerobic respiration/in oxidative phosphorylation?
34
How many molecules of ATP are made from substrate-level phosphorylation?
4
Why is the theoretical total of ATP made never met?
Cell is never this efficient:
ATP used to move pyruvate, ADP, NADH and FADH across inner mitochondrial membrane
Proton leakage across inner membrane rather than passing through ATP synthase
Molecules may also leak through membranes
On average, cells produce 30-32 molecules of ATP per glucose molecule
What is the efficiency of aerobic respiration?
(38x30.6/2880) x100 = 40.4%
What are respiratory substrates?
An organic molecule that can be respired (oxidised) to produce usable energy in the form of ATP
- carbs/glucose are important respiratory substrates
Compare the efficiency of aerobic and anaerobic respiration
Aerobic respiration is a much more efficient way of producing ATP from glucose (40% efficiency as opposed to 2%). However it requires the presence of oxygen. Anaerobic respiration is much less efficient as it only produces 2 ATP per glucose molecule. However it can take place in the absence of oxygen, which is useful if organisms live in low or zero oxygen environments, or if they are exercising.
Describe how lipids are respired
lipids are hydrolysed into fatty acids and glycerol
glycerol is phosphorylated with ATP, dehydrogenated with NAD and converted into triose phosphate (for glycolysis to form pyruvate)
fatty acids are oxidised, produces acetate units (2C) and fed into the Krebs Cycle via acetyl CoA
longer hydrocarbon chain = more acetate units (more ATP and more CO2 and water produced than from glucose)
How do camels humps produce metabolic water?
When the triglycerides stored in the hump are broken down, the long fatty acid tails are converted into acetate. Because there will be many acetate units, they are dehydrogenated and decarboxylated to produce a lot of CO2 and a lot of reduced NAD/FAD. The reduced NAD and FAD then carry the hydrogen to the inner mitochondrial membrane, where eventually O2 will act as the final electron acceptor, forming water. The water that is formed can be used by the camel.
Describe the respiration of proteins
proteins are hydrolysed into amino acids which are deaminated in the liver, forming a keto acid and ammonia
keto acid is converted to acetyl CoA, pyruvate or some other Krebs intermediate and oxidised through aerobic respiration
Q: Describe what happens to pyruvate in anaerobic conditions in mammalian cells
NADH is used to reduce pyruvate to lactate
- NAD is therefore regenerated to convert TP into pyruvate to form ATP
Q: Explain how having a larger number of proton pores in the inner mitochondrial membrane would result in a person being less likely to gain weight?
more pores results in protons leaking back into the matric
less ATP formed from oxidative phosphorylation as there is no proton gradient
more energy is wasted as heat
energy yield from aerobic respiration reduced per molecule of glucose
less excess energy intake in diet
less deposition of fat
fat stores may be respired for energy
Where does chemiosmosis take place in a mitochondrion and a chloroplast?
Mitochondrion: protons flow across the inner membrane from the intermembrane space into the matrix
Chloroplasts: protons flow across the thylakoid membrane from the thylakoid pace into the stroma
What is the proton gradient?
Maintained by proton pumps driven by potential energy associated with excited electrons
- gradient is maintained proton pumps are needed which are powered by energy from electrons
Explain why muscles use glycogen as an energy store rather than fat
releasing energy from glycogen doesn’t require a large O2 supply unlike fats would require
releasing energy from glycogen would mean there would not be the removal of large amounts of CO2
