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What is Adenosine Triphosphate (ATP)?
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What is Adenosine Triphosphate (ATP)?
Adenosine Triphosphate (ATP) is a small and soluble molecule that provides a short-term store of chemical energy that cells can use to do work.
Define the term universal energy currency.
Universal energy currency is a term used to describe ATP because it is used in all organisms and can be reused countless times for different reactions.
True or False?
ATP is a phosphorylated nucleotide.
True.
ATP is a phosphorylated nucleotide.
What does ATPase do?
ATPase is an enzyme that catalyses the hydrolysis of ATP, releasing energy quickly and easily where it is needed within the cell.
What are the components of ATP?
The components of ATP are ribose sugar, an adenine base, and three phosphate groups.
True or False?
ATP is stored in living organisms for later use.
False.
ATP is not stored in living organisms; instead, molecules like glucose and fatty acids are used as short-term energy stores, while glycogen, starch, and triglycerides act as long-term energy storage molecules.
What happens when ATP is hydrolysed?
When ATP is hydrolysed, ADP and a phosphate ion (Pi) are produced, and energy is released.
True or False?
When ATP is formed a molecule of water is released.
True.
Water is released when ATP is formed because ATP synthesis is a condensation reaction.
What is the purpose of cell respiration?
The purpose of cell respiration is to release energy in usable forms from the chemical energy stored in food, such as glucose.
True or False?
Cell respiration is a catabolic process.
True.
Cell respiration is a catabolic process.
Define the term aerobic respiration.
Aerobic respiration is the process of breaking down a respiratory substrate, such as glucose, to produce ATP using oxygen, with the substrate being completely oxidised.
What is the difference between aerobic and anaerobic respiration in terms of ATP yield?
Aerobic respiration yields approximately 36 ATP molecules per glucose molecule, while anaerobic respiration yields only about 2 ATP molecules per glucose molecule.
What are the main respiratory substrates used in cell respiration?
The main respiratory substrates used in cell respiration are glucose, lipids, and proteins.
Where does most of the aerobic respiration occur in eukaryotic cells?
Most of the aerobic respiration occurs in the mitochondria of eukaryotic cells.
What happens to glucose during anaerobic respiration in animals?
During anaerobic respiration in animals, glucose is partially oxidised to form lactic acid.
What by-products are produced in anaerobic respiration in plants and yeasts?
In anaerobic respiration, plants and yeasts produce ethanol and carbon dioxide as by-products.
What is the role of ATP in cell respiration?
In cell respiration, ATP is produced as a result of the controlled release of energy from organic compounds, and it is used to fuel various cellular processes such as muscle contraction, active transport, and anabolic reactions.
True or False?
Oxygen is required for anaerobic respiration.
False.
Oxygen is not required for anaerobic respiration; it occurs in the absence of oxygen.
What factors affect the rate of cell respiration?
Factors affecting the rate of cell respiration include the cell's metabolic activity, size of the organism, oxygen supply, availability of respiratory substrates, temperature, and pH.
How does temperature affect the rate of cell respiration?
The rate of cell respiration increases with temperature up to the optimum temperature of the enzymes involved. Beyond this, the rate decreases as the enzymes denature.
True or False?
Respirometers measure the rate of oxygen consumption during respiration.
True.
Respirometers measure the rate of oxygen consumption during respiration.
What role does potassium hydroxide play in a respirometer experiment?
Potassium hydroxide absorbs the carbon dioxide produced during respiration, reducing air pressure inside the respirometer chamber.
Define the term "metabolically active" in the context of cell respiration.
Metabolically active refers to how much energy a cell requires, with more active cells, like muscle cells, having a higher rate of cell respiration.
What is the purpose of using a water bath in respirometer experiments?
A water bath is used to maintain a constant temperature during respirometer experiments, ensuring accurate and reliable measurements.
How does the size of an organism affect its rate of cell respiration?
Smaller organisms have a higher surface area to volume ratio, leading to higher rates of respiration to compensate for greater heat loss.
What equation is used to calculate the volume of oxygen consumed in a respirometer?
The volume of oxygen consumed (mm³ min⁻¹) is calculated using the equation: πr²h
where r is the radius of the capillary tube, and h is the distance the manometer fluid moves.
True or False?
Lower oxygen availability increases the rate of anaerobic respiration.
True.
When oxygen availability is low, cells increase anaerobic respiration.
Why is it important to repeat respirometer experiments?
Repeating respirometer experiments helps identify anomalies, increases reliability, and allows for calculating a more accurate mean rate of respiration.
What are redox reactions?
Redox reactions are reactions during which both oxidation and reduction occur; they involve the transfer of electrons between molecules.
Define the term oxidation in the context of chemical reactions.
Oxidation is the loss of electrons. Oxidation reactions can also involve loss of hydrogen or gain of oxygen.
Define the term reduction in the context of chemical reactions.
Reduction is the gain of electrons. It can also involve the gain of hydrogen or loss of oxygen.
What are reducing agents?
Reducing agents are molecules that have a strong tendency to lose or donate their electrons.
What are oxidising agents?
Oxidising agents are molecules that have a strong tendency to gain electrons.
True or False?
When hydrogen is removed from a substrate (dehydrogenation), the substrate has been oxidised.
True.
When hydrogen (which contains an electron) is removed from a substrate, the substrate has been oxidised.
How do NAD+ and FAD serve as oxidising agents in respiration?
NAD+ and FAD act as oxidising agents when they gain electrons and hydrogen ions and become reduced (NADH and FADH2).
What is the role of the redox reactions, involving NADH and FADH2, in respiration?
In respiration NADH and FADH2 transport the electrons they have gained to other reactions, before releasing the electrons and returning to their original oxidised forms.
What is glycolysis?
Glycolysis is the first stage of cellular respiration; it takes place in the cytoplasm of the cell.
What are the main events that occur during glycolysis?
Glycolysis involves:
phosphorylation (of glucose)
lysis (of phosphorylated glucose)
oxidation (of the split, phosphorylated glucose)
ATP formation (through substrate-linked phosphorylation)
What happens during the lysis stage of glycolysis?
During lysis the molecule that is produced when glucose is phosphorylated (fructose-1,6-bisphosphate) is split into two molecules (triose phosphate).
What happens during the oxidation stage in glycolysis?
The oxidation stage removes hydrogen from the molecules produced during lysis (triose phosphate) and transfers it to NAD to form NADH.
What are the products of glycolysis?
The products of glycolysis are:
two molecules of pyruvate
a net gain of two molecules of ATP
two molecules of reduced NAD
True or False?
Each step in the glycolysis pathway is catalysed by a different enzyme.
True.
Each step in the glycolysis pathway is catalysed by a different enzyme.
What process converts pyruvate to lactate?
Pyruvate is converted to lactate during anaerobic respiration.
What is the purpose of converting pyruvate to lactate during anaerobic respiration?
Converting pyruvate to lactate during anaerobic respiration regenerates NAD; this allows glycolysis to continue.
What is the net ATP yield per molecule of glucose during anaerobic respiration?
The net ATP yield per glucose molecule during anaerobic respiration is two ATP molecules.
How is anaerobic respiration in yeast cells used in bread making?
Yeasts are useful in bread making because they produce carbon dioxide during anaerobic respiration; this causes bread dough to rise.
What are the similarities between anaerobic respiration in yeast cells and in human cells?
Similarities between anaerobic respiration in yeast cells and human cells include:
both involve the glycolysis pathway
both regenerate NAD
What are the differences between anaerobic respiration in yeast cells and in human cells?
Differences between anaerobic respiration in yeast cells and human cells include:
Anaerobic respiration in yeast cells converts pyruvate to ethanol, while in humans cells pyruvate is converted to lactate
Anaerobic respiration in yeast produces carbon dioxide, while in human cells it does not
What happens to pyruvate during respiration when oxygen is available?
When oxygen is available pyruvate enters the mitochondrial matrix where the link reaction takes place.
What happens to pyruvate during the link reaction?
During the link reaction pyruvate undergoes oxidation and decarboxylation to produce acetyl groups.
What are the products of the link reaction?
The products of the link reaction are:
acetyl CoA
carbon dioxide
reduced NAD
True or False?
The Krebs cycle takes place in the cytoplasm of the cell.
False.
The Krebs cycle takes place in the matrix of the mitochondria.
Which compound enters the Krebs cycle from the link reaction?
Acetyl CoA enters the Krebs cycle from the link reaction. This can also be described as the transfer of acetyl groups by coenzyme A.
How many CO2 molecules are produced per glucose molecule in the Krebs cycle?
The Krebs cycle produces four CO2 molecules per glucose molecule.
Each turn of the Krebs cycle involves two decarboxylation events (each of which produces a molecule of CO2), and there are two turns of the Krebs cycle per glucose molecule.
How is citrate formed in the Krebs cycle?
Citrate is produced by transfer of an acetyl group (from the link reaction) to oxaloacetate.
What are the products of the Krebs cycle?
The products of the Krebs cycle are
ATP
NADH
FADH2
Carbon dioxide
True or False?
The electron carriers in the electron transport chain are embedded in the outer mitochondrial membrane.
False.
The electron carriers in the electron transport chain are embedded in the inner mitochondrial membrane.
True or False?
NAD is converted to NADH when electrons enter the electron transport chain.
False.
Reduced NAD is converted back to NAD when a pair of electrons is passed to the first carrier in the electron transport chain.
Reduced NAD transfers electrons to the electron transport chain. Which reactions of respiration produce reduced NAD for this purpose?
Reduced NAD is produced by:
glycolysis
the link reaction
the Krebs cycle
How is a proton gradient established during oxidative phosphorylation?
The proton gradient is established by the flow of electrons along the electron transport chain.
As electrons pass down the electron transport chain energy is released; this energy is used to transfer protons across the inner mitochondrial membrane.
Define the term chemiosmosis.
Chemiosmosis is the process during which energy from a proton gradient is used to make ATP.
What is the role of ATP synthase in the electron transport chain?
ATP synthase couples release of energy from the proton gradient with phosphorylation of ADP; this generates ATP.
What is the role of oxygen in the electron transport chain?
Oxygen acts as the terminal electron acceptor in the electron transport chain. It accepts electrons from the electron transport chain and protons from the matrix of the mitochondrion, producing metabolic water.
What happens if oxygen is not present to accept electrons in the electron transport chain?
If oxygen is not present the electron transport chain will stop and ATP will no longer be produced by chemiosmosis.
How do lipids compare to carbohydrates as an energy source?
Lipids provide more energy per gram when oxidised during respiration, compared to carbohydrates.
Why do lipids have a higher energy yield than carbohydrates when respired?
Lipids have a higher energy yield than carbohydrates when respired because they have fewer oxygen atoms per molecule than carbohydrates. This means that they have more oxidisable C-H bonds.
True or False?
Glycolysis and anaerobic respiration can use lipids as a substrate.
False.
Glycolysis and anaerobic respiration can only occur if carbohydrates are the substrate.
How do lipids enter respiration?
Lipids enter respiration as follows:
lipids are broken down into fatty acids
fatty acid breakdown produces 2C acetyl groups
acetyl groups combine with coenzyme A to form acetyl CoA, which can then enter the Krebs cycle