What is the role of an enzyme in a chemical reaction?
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An enzyme speeds the reaction by reducing its activation energy (E A) without affecting the free-energy change (ΔG).
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What is the role of an enzyme in a chemical reaction?
An enzyme speeds the reaction by reducing its activation energy (E A) without affecting the free-energy change (ΔG).
What processes enable cells to produce ATP without oxygen?
Fermentation and anaerobic respiration.
How many chloroplasts does a typical mesophyll cell contain?
About 30 to 40 chloroplasts.
What happens to electrons as they move down the electron transport chain?
They lose energy in several energy-releasing steps.
What happens to one molecule of G3P in the Calvin cycle?
It exits the cycle to be used by the plant cell.
What are the other names for the Calvin cycle?
Dark reactions and light-independent reactions.
Which two crops are important C4 plants in agriculture?
Sugarcane and corn.
What does ΔG > 0 indicate?
An endergonic reaction where energy is required and the reaction is nonspontaneous.
When do CAM plants open their stomata?
During the night.
What is produced during lactic acid fermentation?
2 Lactate, with no release of CO2.
What types of work can ATP drive?
Mechanical work, chemical work, and transport work.
How much ATP is produced in glycolysis?
2 ATP.
Which enzyme catalyzes the first step of the Calvin cycle?
RuBP carboxylase-oxygenase, commonly known as rubisco.
What do anabolic pathways do?
They consume energy to build complicated molecules from simpler ones.
What is the role of sulfate-reducing bacteria in anaerobic respiration?
They have an electron transport chain but do not use oxygen as a final electron acceptor.
What are the two distinct types of photosynthetic cells in C4 plants?
Bundle-sheath cells and mesophyll cells.
What are the two main steps in alcohol fermentation?
What is transferred to the primary electron acceptor in a photosystem?
An excited electron from the special pair of chlorophyll a molecules.
What is activation energy (E A)?
The energy necessary to break the bonds of the reactants in a chemical reaction.
What do catabolic pathways do?
They release energy by breaking down complex molecules into simpler compounds.
What are the main electron carriers in the citric acid cycle?
NAD+ and FAD.
What is produced during pyruvate oxidation?
CO2, NADH, and Acetyl CoA.
From where is the oxygen produced during photosynthesis derived?
From water (H2O), not from carbon dioxide (CO2).
What is the energy content of one mole of ATP?
7.3 kcal/mol.
What is the primary energy currency in living systems?
ATP (Adenosine Triphosphate).
What do photoautotrophs use to synthesize organic molecules?
Light energy, carbon dioxide, and usually water.
What happens when a photon strikes a pigment molecule in a light-harvesting complex?
The energy is passed from molecule to molecule until it reaches the reaction-center complex.
What is ATP's role in energy coupling?
ATP provides energy for various cellular processes by coupling exergonic and endergonic reactions.
Where does pyruvate oxidation occur in aerobically respiring prokaryotic cells?
In the cytosol.
What type of work does ATP provide energy for?
Chemical work, transport work, and mechanical work.
What is the first step of the light reactions?
The solar-powered transfer of an electron from the reaction-center chlorophyll a pair to the primary electron acceptor.
What is the overall reaction for cellular respiration?
The breakdown of glucose to produce energy.
What is the efficiency of respiration in terms of ATP production?
34%.
What is substrate-level phosphorylation?
ATP synthesis occurs when an enzyme transfers a phosphate group from a substrate molecule to ADP.
What is another name for the citric acid cycle?
The tricarboxylic acid cycle or the Krebs cycle.
What is glycolysis?
The first stage of cellular respiration where glucose is broken down.
What drives the phosphorylation of ADP to form ATP during chemiosmosis?
The diffusion of H+ back into the matrix through ATP synthase.
What type of process is the Calvin cycle?
Anabolic, building carbohydrates from smaller molecules and consuming energy.
What is the primary function of photosynthesis?
To convert light energy to the chemical energy of food.
What is the conversion of glucose during glycolysis?
1 glucose is converted to 2 pyruvate.
What are the two main types of cellular respiration?
Aerobic cellular respiration and anaerobic cellular respiration.
What process occurs when oxygen is not available for energy production?
Anaerobic cellular respiration.
Where are chloroplasts mainly found in plants?
In the cells of the mesophyll.
What do CAM plants do during the night?
Take up CO2 and incorporate it into organic acids.
What do NADH and FADH2 transfer to the electron transport chain?
Electrons.
What characterizes an exergonic reaction in terms of energy profile?
It releases energy and is spontaneous under standard conditions.
What is the function of NADH in fermentation?
It transfers electrons to regenerate NAD+ from pyruvate or its derivatives.
What is oxidative phosphorylation associated with?
Mitochondria.
What do the light reactions of photosynthesis convert?
Solar energy to chemical energy.
What is the primary function of photosynthesis?
To convert light energy to the chemical energy of food.
What type of bacteria can perform anaerobic respiration using sulfate?
Sulfate reducing bacteria.
What is fermentation?
A way of harvesting chemical energy without using oxygen or an electron transport chain.
What are the three main stages of aerobic cellular respiration?
Glycolysis, pyruvate oxidation and the citric acid cycle, oxidative phosphorylation.
How much energy is produced from the breakdown of one mole of glucose under standard conditions?
686 kcal (2,870 kJ).
What is the mode of carbon fixation used by CAM plants called?
Crassulacean acid metabolism (CAM).
What are the three main types of work that ATP is involved in?
Chemical work, transport work, and mechanical work.
What pigment gives leaves their green color?
Chlorophyll.
What is the final electron acceptor in fermentation?
An organic molecule (e.g., acetaldehyde in alcohol fermentation, pyruvate in lactic acid fermentation).
What are the components of ATP (adenosine triphosphate)?
Sugar ribose, nitrogenous base adenine, and a chain of three phosphate groups.
What is the final electron acceptor in the electron transport chain?
Oxygen (O2), which is reduced to water (H2O).
What happens during the hydrolysis of ATP?
ATP is converted into ADP (adenosine diphosphate) and inorganic phosphate (Pi), releasing energy.
Can carbohydrates, fats, and proteins be used as fuel for cellular respiration?
Yes, they can all be used as fuel.
In what form does carbon enter the Calvin cycle?
As CO2.
What happens to the rest of the energy stored in glucose?
It is lost as heat.
What is the final product of the Calvin cycle?
G3P (glyceraldehyde-3-phosphate).
What is the main photosynthetic pigment in plants?
Chlorophyll a.
What does ΔG < 0 indicate?
An exergonic reaction where energy is released and the reaction is spontaneous.
What happens to pyruvate in eukaryotic cells when O2 is present?
It enters a mitochondrion where the oxidation of glucose is completed.
What is the function of veins in plants related to photosynthesis?
Deliver water from roots to leaves and export sugar from leaves to roots and other non-photosynthetic parts.
What is the net product of ATP from glycolysis?
2 ATP.
What does the citric acid cycle complete?
The energy-yielding oxidation of organic molecules.
What type of work is involved in catabolism?
Chemical work, transport work, and mechanical work.
What are examples of mechanical work driven by ATP?
Beating of cilia, contraction of muscle cells, and movement of chromosomes during cellular reproduction.
What occurs during oxidative phosphorylation?
Electron transport and chemiosmosis.
What is produced during glycolysis from one glucose molecule?
2 ATP and 2 NADH.
What is the total energy content of glucose in kcal?
686 kcal/mol.
What chemical energy is required for the Calvin cycle?
ATP.
Is carbon released as CO2 during glycolysis?
No, no carbon is released as CO2 during glycolysis.
What reducing power does the Calvin cycle consume?
NADPH.
What does ΔG < 0 indicate?
An exergonic reaction where energy is released and the reaction is spontaneous.
What is a photosystem composed of?
A reaction-center complex surrounded by several light-harvesting complexes.
What does ΔG > 0 indicate?
An endergonic reaction where energy is required and the reaction is nonspontaneous.
What is fermentation?
A metabolic process that converts sugar to acids, gases, or alcohol in the absence of oxygen.
What are the standard conditions for measuring free-energy change?
1 M of each reactant and product, 25 °C, pH 7.
What are the three main stages of aerobic respiration?
Glycolysis, pyruvate oxidation and the citric acid cycle, and oxidative phosphorylation.
What is the second phase of the Calvin cycle?
Reduction.
What is the role of enzymes in reactions?
Enzymes speed up reactions by lowering the activation energy.
What is the first step of the Calvin cycle?
Carbon fixation, where CO2 is attached to ribulose bisphosphate (RuBP).
How does ATP facilitate transport work?
By pumping substances across membranes against the direction of spontaneous movement.
What is the significance of activation energy in reactions?
It is the energy required to initiate a reaction, influencing the rate of the reaction.
What are the final electron acceptors in anaerobic respiration?
SO4^2- and NO3^-.
What does NAD+ function as during respiration?
An electron acceptor.
What is the initial step of the Calvin cycle?
Incorporating CO2 from the air into organic molecules in the chloroplast.
What is produced as a by-product when water is split during the light reactions?
Oxygen (O2).
What is the final electron acceptor in fermentation?
An organic molecule (e.g., acetaldehyde in alcohol fermentation, pyruvate in lactic acid fermentation).
What does glycolysis do?
Glycolysis harvests chemical energy by oxidizing glucose to pyruvate.
What is produced at the end of the Calvin cycle?
Sugar.
What is the total ATP yield from glycolysis and the citric acid cycle combined?
38 ATP per molecule of glucose.
What energy source does the Calvin cycle spend?
ATP.
Where do the light reactions occur?
In the thylakoids of the chloroplast.
What are photosystems composed of?
A reaction-center complex surrounded by light-harvesting complexes.
What is the first phase of the Calvin cycle?
Carbon fixation.
What does a negative ΔG indicate about a reaction?
The reaction is exergonic, meaning it releases energy and occurs spontaneously.
What enzyme is involved in the Calvin cycle?
Rubisco.
What is the role of the special pair of chlorophyll a molecules?
They can use energy from light to boost one of their electrons to a higher energy level and transfer it to the primary electron acceptor.
What is the process of photophosphorylation associated with?
Chloroplasts.
What is the role of Acetyl CoA in the citric acid cycle?
It combines with oxaloacetate to form citrate.
What are the two stages of photosynthesis?
The light reactions and the Calvin cycle.
What is the role of pyruvate oxidation in cellular respiration?
It converts pyruvate into acetyl-CoA for the citric acid cycle.
How much ATP is produced from one molecule of FADH2?
1.5 ATP.
What is the role of light reactions in relation to the Calvin cycle?
Light reactions regenerate ATP and NADPH needed for the Calvin cycle.
What is the role of the proton motive force in ATP synthesis?
It drives the phosphorylation of ADP to form ATP.
What allows cells to produce ATP without oxygen?
Anaerobic respiration and fermentation.
What is the product of glycolysis that enters the citric acid cycle?
Acetyl CoA.
What must happen to amino acids before they can be oxidized?
They must be deaminated.
What is the energy investment phase in glycolysis?
It involves the use of 2 ATP to initiate the process.
What does CAM stand for in the context of photosynthesis?
Crassulacean Acid Metabolism.
What is the wavelength range of visible light important for photosynthesis?
From about 380 nm to 750 nm.
What does glycolysis accomplish?
It harvests chemical energy by oxidizing glucose to pyruvate.
What is the significance of the hydrolysis of ATP?
It releases energy that can be used for cellular work.
How many moles of ATP are produced in aerobic respiration?
32 moles of ATP.
How many molecules of G3P must be recycled to regenerate three molecules of RuBP?
Five molecules of G3P.
How much ATP is produced from one molecule of NADH?
2.5 ATP.
Where do monomers of carbohydrates, fats, and proteins enter cellular respiration?
At various points in glycolysis or the citric acid cycle.
What molecule is reduced to NADPH during the light reactions?
NADP+.
What occurs during the light reactions in the thylakoid membranes?
Water is split, releasing O2, producing ATP, and forming NADPH.
How does energy flow in an ecosystem?
Energy flows in as sunlight and leaves as heat, while essential chemical elements are recycled.
What is the first product of the Calvin Cycle in C-3 plants?
3-phosphoglyceric acid (3-PGA).
What is the first product of the Calvin Cycle in C-4 plants?
Oxaloacetic acid.
Which plants are examples of C-3 plants?
Rice, wheat, and soybean.
What are pigments?
Substances that absorb visible light.
How do C4 plants fix carbon?
They incorporate CO2 into four-carbon compounds in mesophyll cells, which are then exported to bundle-sheath cells.
What is oxidative phosphorylation?
ATP synthesis occurs by the use of energy released by the electron transport chain.
What are the main products of the citric acid cycle?
NADH, FADH2, and ATP.
What are the main stages of aerobic cellular respiration?
Glycolysis, pyruvate oxidation and the citric acid cycle, and oxidative phosphorylation.
What are the energy requirements for the Calvin cycle to synthesize one G3P molecule?
The cycle consumes 9 ATP and 6 NADPH.
What is substrate-level phosphorylation?
A process that generates ATP directly in the citric acid cycle.
How many ATP are produced in glycolysis for fermentation, anaerobic respiration, and aerobic respiration?
2 ATP for each process.
What are the total ATP and NADH produced in the citric acid cycle from one glucose molecule?
2 ATP, 6 NADH, and 2 FADH2.
What does the Calvin cycle produce from CO2?
Sugar, using ATP for energy and NADPH for reducing power.
What is the role of NADH in oxidative phosphorylation?
It transfers electrons to the electron transport chain, creating a proton motive force to produce ATP.
Does glycolysis require oxygen?
Glycolysis occurs whether or not O2 is present.
How do fatty acids enter the citric acid cycle?
They undergo beta oxidation to form two-carbon fragments, which enter as acetyl CoA.
What is the third phase of the Calvin cycle?
Regeneration of the CO2 acceptor (RuBP).
Which plants are examples of C-4 plants?
Sugarcane and corn.
What are the three metabolic stages of cellular respiration?
(1) Glycolysis, (2) Pyruvate oxidation & the citric acid cycle, (3) Oxidative phosphorylation (electron transport and chemiosmosis).
What is carbon fixation?
The initial incorporation of carbon into organic compounds.
How many NADH are produced during pyruvate oxidation?
2 NADH.
What are the final electron acceptors in anaerobic respiration?
SO4^2- or NO3-.
What is the final electron acceptor in aerobic respiration?
O2.
How many times must the Calvin cycle occur to synthesize one molecule of G3P?
Three times.
What do the light reactions convert solar energy into?
Chemical energy in the form of ATP and NADPH.
How many ATP are produced from FADH2 during oxidative phosphorylation?
2 ATP per FADH2.
What distinguishes Photosystem II?
It contains P680 chlorophyll a molecules in the reaction-center complex.
What is the key light-capturing pigment in photosynthesis?
Chlorophyll a.
How do CAM plants adapt to arid climates?
They open their stomata at night to incorporate CO2 into organic acids, which are stored and used during the day.
What process powers the addition of a phosphate group to ADP in the light reactions?
Chemiosmosis, through photophosphorylation.
What are the three main stages of aerobic cellular respiration?
What is required for the Calvin cycle to continue after regeneration of RuBP?
CO2 must be received again.
Where does the Calvin cycle take place?
In the stroma of the chloroplast.
Do sulfate reducing bacteria use oxygen as a final electron acceptor?
No, they do not use oxygen as a final electron acceptor.
Why are leaves green?
Because chlorophyll absorbs most wavelengths except green.
How many ATP are produced from NADH during oxidative phosphorylation?
3 ATP per NADH.
What happens when chlorophyll a absorbs energy?
An electron is boosted to a higher energy level and transferred to the primary electron acceptor.
Which plants are examples of CAM plants?
Cactus and pineapple.
When does the Calvin Cycle occur in CAM plants?
At night when the stomata are open.
What distinguishes Photosystem I?
It contains P700 chlorophyll a molecules.
What completes the energy-yielding oxidation of organic molecules after pyruvate is oxidized?
The citric acid cycle.
What couples electron transport to ATP synthesis during oxidative phosphorylation?
Chemiosmosis.
What are the three stages of aerobic respiration?
What is the role of enzymes in metabolic reactions?
Enzymes speed up reactions by lowering energy barriers without affecting the free-energy change (ΔG).
What is the first product formed in C4 plants during carbon fixation?
A four-carbon compound.
