bioenergetics?
the quantitative study of energy conversions & energy relationships in biological system.
Why is photosynthesis a redox process?
What acts as the reducing agent in photosynthesis?
How is photosynthesis defined bio-energetically?
Which molecules are energy-poor in photosynthesis?
Which molecule is energy-rich after photosynthesis?
What provides the extra energy for photosynthesis?
What is the overall equation of photosynthesis?
What are the main requirements for photosynthesis?
Because CO₂ is reduced to C₆H₁₂O₆ & H₂O is oxidized to O₂.
Water (H₂O).
It is an energy conversion process where CO₂ and H₂O (energy-poor) are transformed into glucose (energy-rich) using sunlight absorbed by pigments.
CO₂ and H₂O.
Glucose.
Sunlight absorbed by photosynthetic pigments.
6CO₂ + 12H₂O → C₆H₁₂O₆ + 6O₂ + 6H₂O, in the presence of light and chlorophyll.
Sunlight, chlorophyll, water, and carbon dioxide.
Which laws do biological energy transformations obey?
What is the ultimate source of energy for life and ecosystems?
In what form does sunlight reach the Earth?
Why is light energy important for life processes?
What is the electromagnetic spectrum?
What is the range of visible light in nanometers?
Which part of the electromagnetic spectrum is effective for photosynthesis?
What determines the effectiveness of a wavelength in photosynthesis?
What is an action spectrum?
Which wavelengths of light are most effective for photosynthesis?
The laws of thermodynamics.
Sunlight.
Electromagnetic energy.
Because it is converted to chemical energy and then into other forms required for life.
The full range of electromagnetic radiation in the universe.
380 nm to 750 nm.
Visible light.
Its absorption by photosynthetic pigments.
A graph showing the effectiveness of different wavelengths of light for photosynthesis.
Blue light (around 430 nm) and red light (around 670 nm).
What role does carbon dioxide play in photosynthesis?
Why are plants called autotrophs?
In which phase of photosynthesis is CO₂ utilized?
What percentage of CO₂ is present in air?
How does an increase in CO₂ concentration affect photosynthesis?
What happens when CO₂ concentration rises above 1%?
What carbon sources do aquatic photosynthetic organisms use?
How can the rate of photosynthesis be measured?
It acts as a carbon source for the synthesis of organic compounds.
Because they use CO₂ (a low-energy inorganic compound) to make high-energy organic compounds.
In the light-independent reaction (Calvin cycle).
About 0.03 to 0.04 percent.
It increases the rate of photosynthesis.
The rate slows down due to stomatal closing.
Dissolved CO₂, bicarbonates, and carbonates.
By measuring the CO₂ consumed or O₂ released in a given time.
What role does water play in photosynthesis?
What is photolysis of water?
How are electrons from water used in photosynthesis?
What happens to hydrogen ions and electrons from water?
What happens to the oxygen produced in photolysis?
It acts as a hydrogen and electron donor.
The splitting of water into 2H⁺, 2e⁻, and ½O₂ during the light-dependent phase.
They replace the photoexcited electrons lost by chlorophyll-a in photosystem II (P680).
They are taken up by NADP⁺ to form NADPH, which reduces CO₂ in the Calvin cycle.
It is released into the atmosphere.
What is a pigment in photosynthesis?
Where are pigments found in photosynthetic bacteria?
Where are photosynthetic pigments located in plants?
What are the two major groups of pigments in higher plants?
Which wavelengths of light do chlorophylls mainly absorb?
Which wavelengths are least absorbed and reflected by chlorophylls?
What are the two major types of chlorophyll in plants?
What is the color of chlorophyll-a and where is it found?
What is the color of chlorophyll-b and where is it found?
Which additional forms of chlorophyll are found in algae?
Which type of chlorophyll is present in photosynthetic bacteria?
What is the molecular formula of chlorophyll-a?
What is the molecular formula of chlorophyll-b?
Any substance that absorbs light energy for food synthesis.
In the cytoplasm.
In the thylakoid membranes (grana lamellae) of chloroplasts.
Chlorophylls and carotenoids.
Violet, blue, orange, and red.
Green and yellow.
Chlorophyll-a and chlorophyll-b.
Bluish-green, found in all photosynthetic organisms except photosynthetic bacteria.
Yellowish-green, found in all photosynthetic organisms except brown algae, red algae, and photosynthetic bacteria.
Chlorophyll-c, chlorophyll-d, and chlorophyll-e.
Bacteriochlorophyll.
C₅₅H₇₂O₅N₄Mg.
C₅₅H₇₀O₆N₄Mg.
What are the main structural parts of a chlorophyll molecule?
What does the head of chlorophyll consist of?
What is found in the center of the porphyrin ring?
How many pyrrole rings are in the porphyrin ring and what do they contain?
How do nitrogen atoms in pyrrole rings interact with magnesium?
What is the only structural difference between chlorophyll-a and chlorophyll-b?
A head and two tails.
A porphyrin ring with magnesium in the center.
Magnesium (Mg).
Four pyrrole rings, each containing four carbons and one nitrogen atom.
They interact with the central magnesium atom.
Chlorophyll-a has a methyl group (-CH₃) on the 2nd pyrrole ring, while chlorophyll-b has an aldehyde group (-CHO) at that point.
What is the nature of the chlorophyll head and where is it located?
What are the two side chains of chlorophyll called?
What is the nature of the chlorophyll tails and where are they located?
What is the function of the chlorophyll tails?
Why do plants continuously synthesize chlorophyll?
What conditions are required for chlorophyll synthesis in plants?
Why do plants synthesize more chlorophyll in summer?
What is chlorosis?
Hydrophilic, exposed on the surface of the thylakoid membrane, and light absorbing.
Phytol and methyl ester.
Hydrophobic, embedded into the thylakoid membranes.
They anchor the chlorophyll molecule in the membrane.
To maintain continuous photosynthesis.
Sunlight, nitrogen, magnesium, and warm temperatures.
Because warm temperatures favor chlorophyll synthesis.
Deficiency of chlorophyll in leaves.
Why do plants appear green in color?
What instrument is used to measure the relative abilities of pigments to absorb light?
What is the primary role of photosynthetic pigment molecules?
What is the chief component of the photosystem?
What can chlorophyll-a directly convert light energy into?
Why are pigments like chlorophyll-b, xanthophyll, and carotenes called accessory pigments?
How do accessory pigments assist chlorophyll-a?
What extra function do some carotenoids perform?
Because chlorophyll does not absorb green light but reflects it.
Spectrophotometer.
To absorb EM radiation & transmit the energy of absorbed photons to the reaction center.
Chlorophyll-a molecule.
Chemical energy in the form of ATP and NADPH.
Because they can absorb light energy but cannot directly convert it into chemical energy.
By absorbing other wavelengths of light and transferring their energy to chlorophyll-a.
They protect chlorophyll from intense light by absorbing and dispersing excessive light energy.
What is an absorption spectrum?
Which instrument is used to measure absorption spectrum?
Name the two main photoreceptors in plants.
Which wavelengths do chlorophylls absorb strongly?
Which wavelengths do carotenoids absorb strongly?
Do pigments absorb all wavelengths equally?
Why do chlorophyll a and chlorophyll b absorb differently?
A graph showing how much light pigments absorb at different wavelengths.
Spectrophotometer.
Chlorophyll a and Chlorophyll b.
Violet-blue (400–470 nm) and orange-red (630–660 nm).
430–500 nm.
No.
Because of differences in their molecular formula, structure, and properties.
Where are photosynthetic pigments embedded for efficient absorption of light?
What are clusters of pigment molecules called?
What is the peripheral part of a photosystem called, and which pigments does it contain?
What is the central part of a photosystem called, and which pigment does it contain?
What is the optimal absorption wavelength of chlorophyll-a in PS-I and what is it called?
What is the optimal absorption wavelength of chlorophyll-a in PS-II and what is it called?
Why are photosystems named PS-I and PS-II?
Why does chlorophyll-a need antenna pigments?
What happens when energy reaches chlorophyll-a in the reaction centre?
What role does the electron transport system play after electron excitation?
On the surface of thylakoid membranes.
Photosystems.
Antenna complex; it contains accessory pigments such as chlorophyll-b and carotenoids.
Reaction centre; it contains only chlorophyll-a and associated proteins.
700 nm; P700.
680 nm; P680.
They are named in the order of their discovery, not their sequence in the thylakoid membrane.
Because chlorophyll-a absorbs light of only a narrow wavelength and needs help to capture energy from a larger spectrum.
Its electrons become highly excited, escape, and are accepted by the first molecule of the nearby electron transport chain.
It helps in the generation of ATP by converting light energy into chemical energy.
Into how many phases is photosynthesis divided?
What is the other name of the light-dependent phase?
Where does the light-dependent phase take place?
What are the main products of the light-dependent phase?
What are the input and output substances of the light-dependent phase?
What is the other name of the light-independent phase?
Why does the dark reaction occur during the daytime?
What is the input of the dark reaction?
What is the main output of the dark reaction?
What provides energy and reducing power for the dark reaction?
Two phases.
Light reaction.
In the thylakoid membranes.
ATP and NADPH.
Input: Water; Output: Oxygen.
Dark reaction.
Because it requires ATP and NADPH produced in the light reaction.
Carbon dioxide.
Glyceraldehyde-3-phosphate (G3P).
ATP provides energy; NADPH provides energized electrons & hydrogen
What does the light-dependent phase involve?
What are the types of electron flow in light reactions? flow through what?
Photophosphorylation? types?
Chemiosmosis?
In which type of electron flow do electrons not return to the photosystem?
Which photophosphorylation pathway is predominant in higher plants?
most imp. event in light reaction?
- Absorption of light, excitation and flow of electrons, ATP synthesis, and reduction of NADP⁺ to NADPH.
- Non-cyclic and cyclic electron flow. ETC
- the production of ATP during light reaction.
- mechanism of ATP production in light reaction
- Chemiosmosis.
- Non-cyclic electron flow.
- Non-cyclic photophosphorylation.
- production of ATP
reduction is gain of H
Which photosystems are used in non-cyclic photophosphorylation?
What happens when two photons strike the antenna complex of PS-II?
What is the fate of excited electrons of PS-II?
What happens to PS-II when its electrons are lost?
How are the “electron holes” of PS-II filled?
Both PS-I and PS-II.
Two electrons become excited and energy reaches the reaction centre (P680).
They are captured by the primary electron acceptor of PS-II.
It develops two “electron holes” and becomes a strong oxidizing agent.
By electrons released during photolysis of water.
After leaving PS-II, where do the excited electrons go first?
From plastoquinone (PQ), where do electrons flow next?
What does the cytochrome complex consist of?
Besides being an electron carrier, what is the other role of the cytochrome complex?
How does the cytochrome complex pump protons into the thylakoid inner space?
What gradient is formed in the thylakoid inner space due to proton pumping?
Which enzyme is activated by this proton gradient?
What is the function of ATP synthase in light reaction?
What is the process of ATP formation in light reaction called?
What is the whole mechanism of electron flow, proton pumping, and ATP formation called?
Where is the ATP produced in light reactions used later?
After losing energy, where do electrons move from cytochrome complex?
Into which photosystem are these electrons finally incorporated?
To plastoquinone (PQ).
Through the cytochrome complex (Cyt-b and Cyt-f).
Cytochrome-b and cytochrome-f.
Works as a proton pump.
By using the energy of flowing electrons.
Proton (H⁺) gradient.
ATP synthase.
Moves protons back into the stroma and catalyzes formation of ATP from ADP + Pi.
Photophosphorylation.
Chemiosmosis.
In the Calvin cycle for sugar synthesis.
To plastocyanin (PC).
Into photosystem I (PS-I).
What is the reaction centre of PS-I called?
15. What happens when P700 absorbs two photons of light?
16. Where are the excited electrons of PS-I passed?
17. What is created in P700 when its electrons are excited and passed on?
18. How are the “electron holes” of P700 filled?
19. Which photosystem donates electrons to fill the electron holes of P700?
P700.
15. Its electrons are boosted to a higher energy level.
16. To the primary electron acceptor of PS-I.
17. “Electron holes”.
18. By electrons received through the ETC.
19. Photosystem II (P680).
After PS-I, where are the photoexcited electrons first passed?
Which protein accepts electrons from PS-I?
What type of protein is ferredoxin (Fd)?
Which enzyme transfers electrons from ferredoxin to NADP⁺?
What type of enzyme is NADP reductase?
What reaction does NADP reductase catalyze?
What is formed when NADP⁺ combines with electrons and hydrogen ions?
What role does NADPH play in photosynthesis?
What is the electron transport pathway through both photosystems during non-cyclic photophosphorylation called?
Why is this pathway called the “Z-Scheme”?
To a second electron transport chain.
Ferredoxin (Fd).
An iron-containing protein.
NADP reductase.
A flavoprotein enzyme.
NADP⁺ + 2e⁻ + 2H⁺ → NADPH + H⁺.
NADPH (reduced form).
Provides reducing power for the Calvin cycle (sugar synthesis).
The Z-Scheme.
Because of its zigzag conceptual shape.
What condition stimulates a shift from non-cyclic to cyclic electron flow?
12. Which photosystem is used in cyclic photophosphorylation?
13. What happens when PS-I absorbs photons?
14. Where do excited electrons of PS-I first go?
15. Through which electron transport chain components do electrons pass in cyclic flow?
16. At which point in the chain is ATP generated?
17. How is ATP generated in cyclic photophosphorylation?
18. After losing energy, where do electrons return in cyclic photophosphorylation?
19. What three things do not occur in cyclic photophosphorylation?
When NADPH accumulates and ATP supply is low.
12. Only Photosystem I.
13. Electrons are boosted to a higher energy level.
14. To the primary electron acceptor of PS-I.
15. Ferredoxin (Fd), cytochrome b-f complex, and plastocyanin (PC).
16. When electrons pass through the cytochrome b-f complex.
17. By chemiosmosis (proton gradient driving ATP synthase).
18. Back to P700 chlorophyll in PS-I reaction centre.
19. No NADPH formation, no photolysis of water, no oxygen release.
Why is the dark reaction called “light independent”?
Which products of the light reaction are required for the dark reaction?
What is the role of NADPH in the dark reaction?
What is the role of ATP in the dark reaction?
Into which compound is CO₂ finally converted in the dark reaction?
Which metabolic pathway is involved in the dark reaction of most plants?
Which additional pathway is found in some plants besides the Calvin cycle?
What are plants called that use only the Calvin cycle?
Because it does not directly require light to occur.
NADPH and ATP.
NADPH reduces carbon dioxide.
ATP provides energy incorporation.
Glyceraldehyde-3-phosphate (G3P).
The Calvin cycle (C3 pathway).
The C4 pathway.
C3 plants.
What are the three main phases of the Calvin cycle?
What is the function of RuBP in the Calvin cycle?
Which enzyme catalyzes the reaction between RuBP and CO₂?
What is the full name of RuBisCO?
What happens to the six-carbon intermediate formed in this step?
What is the first stable compound formed in the Calvin cycle?
Why is the Calvin cycle also called the C3 pathway?
Carbon fixation, reduction, regeneration of RuBP.
Acts as the CO₂ acceptor (5-carbon phosphorylated sugar).
RuBisCO enzyme catalyzes the reaction.
Ribulose bisphosphate carboxylase/oxygenase.
It is unstable and immediately splits into two 3-carbon compounds.
3-phosphoglycerate (3-PGA).
Because the first stable product is a 3-carbon compound (3-PGA).
How many molecules of 3-PGA enter the reduction phase per cycle?
What happens when 3-PGA reacts with ATP?
Which compound is formed after phosphorylation of 3-PGA?
How is 1,3-bisphosphoglycerate reduced to G3P?
How many molecules of G3P are formed in the reduction phase?
How many G3P molecules are released from the cycle?
What happens to the remaining G3P molecules?
Six molecules.
Each 3-PGA receives a phosphate group from ATP.
1,3-bisphosphoglycerate.
By the addition of hydrogen from NADPH.
Six molecules of G3P.
Only one molecule is released.
Five molecules are used to regenerate RuBP (CO₂ acceptor).
How many G3P molecules from the previous phase are used to regenerate RuBP?
How many carbon atoms does each G3P molecule contain?
How many molecules of ribulose phosphate (RuP) are produced during regeneration?
What happens when RuP reacts with ATP?
What is the final product of this regeneration phase?
How many molecules of CO₂, NADPH, and ATP are used to release one molecule of G3P?
How many G3P molecules are required to produce one glucose molecule?
The overall process of Calvin cycle can be represented as?
Five molecules of G3P.
Three carbon atoms.
Three molecules of RuP.
Each RuP receives a phosphate group from ATP.
RuBP (ribulose-1,5-bisphosphate).
Three CO₂, six NADPH, nine ATP.
Two molecules of G3P.
What is an oxidation-reduction reaction in biological systems?
What is cellular respiration?
How many kinds of cellular respiration are there?
What is aerobic respiration?
What is anaerobic respiration?
Which organic molecule is usually broken down to release energy?
What is the first common step of both aerobic and anaerobic respiration?
What are the final products of aerobic respiration in the presence of oxygen?
How much ATP is produced in aerobic respiration in eukaryotes and prokaryotes?
What are the final products of anaerobic respiration, and how much energy do they release?
A chemical reaction involving the removal of hydrogen from one molecule and its gain by another.
A series of complex oxidation-reduction reactions by which living cells obtain energy through the breakdown of organic matter.
Two: aerobic and anaerobic respiration.
Respiration that occurs in the presence of abundant atmospheric oxygen.
Respiration that occurs in the absence of oxygen.
Glucose.
Glycolysis, where glucose is broken into two molecules of pyruvate.
Carbon dioxide and water.
36 ATPs in eukaryotes; 38 ATPs in prokaryotes.
Lactic acid or ethanol and carbon dioxide, releasing only 2 ATPs.
Where does anaerobic respiration occur?
What is anaerobic respiration?
What is another name for anaerobic respiration?
How many pathways of anaerobic respiration exist, and what are they based on?
What happens during lactic acid fermentation after glycolysis?
Why does lactic acid fermentation operate anaerobically?
What is the overall chemical equation for lactic acid fermentation?
In which organisms or cells does lactic acid fermentation occur?
What effect does the accumulation of lactic acid have on muscles?
In many microorganisms (bacteria, yeast), muscle cells of vertebrates, and cells of higher plants.
The incomplete breakdown of glucose in the absence of oxygen.
Fermentation.
Two pathways: lactic acid fermentation and alcoholic fermentation; based on the nature of the final products.
Pyruvate is reduced by NADH to form lactic acid.
Because NADH returns to pick up more electrons during glycolysis, allowing the process to continue without oxygen.
C₆H₁₂O₆ + 2NAD⁺ → 2C₃H₄O₃ + 2NADH + 2H⁺
Anaerobic bacteria, and muscles of mammals and humans during strenuous exercise.
Causes muscle fatigue, making muscles unable to contract and leading to soreness.
