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Questions and Answers
What is the primary function of ATP and reduced NADP in the photosynthesis process?
Where does the light independent stage of photosynthesis take place?
What role does the enzyme ribulose bisphosphate carboxylase (rubisco) play in the Calvin cycle?
What is formed when the unstable six-carbon compound in the Calvin cycle breaks down?
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How many triose phosphate molecules are used to regenerate ribulose bisphosphate in the Calvin cycle?
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What is the main product of pairing two triose phosphate molecules in the Calvin cycle?
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Which process is primarily responsible for the synthesis of carbohydrates in plants?
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What is the initial molecule that carbon dioxide combines with in the Calvin cycle?
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What happens when light is absent concerning the light independent stage of photosynthesis?
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What is the significance of the Calvin cycle in the context of plant metabolism?
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What happens to the majority of triose phosphate molecules produced in the Calvin cycle?
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What is the role of ATP in the Calvin cycle?
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During the Calvin cycle, what is the immediate product formed when carbon dioxide combines with ribulose bisphosphate?
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How are hydrogen ions provided for the reduction reaction in the Calvin cycle?
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What occurs in the stroma of chloroplasts during the light independent stage?
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How does water contribute to temperature stability in aquatic environments?
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What is the primary reason ice floats on liquid water?
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Which property of water is responsible for its high surface tension?
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Which characteristic of water helps in the transport of molecules in living organisms?
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Why does water have high melting and boiling points compared to other substances?
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How does the process of cohesion contribute to the properties of water?
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What role does water's transparency play in aquatic ecosystems?
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What is a consequence of ice floating on water for aquatic organisms?
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What defines water as an excellent solvent in biological systems?
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What causes the polarity of water molecules?
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How do water molecules demonstrate high surface tension?
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What is one significant role of water as a solvent in biological systems?
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Why does water have a high specific heat capacity?
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In which way does water facilitate transport in plants?
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What factor contributes to the high melting and boiling points of water?
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What happens to the charge of water molecules?
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How does the dipolar nature of water affect ionic substances?
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What role does water play in maintaining cell membrane stability?
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What characteristic enables water to be an excellent solvent for polar molecules?
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Study Notes
Light Independent Stage of Photosynthesis
- ATP and reduced NADP (NADPH H+) produced in the light dependent stage are essential for the light independent stage, also known as the Calvin cycle.
- This stage does not require light directly but relies on products from the light dependent stage, halting when light is absent.
- Occurs in the stroma of chloroplasts and was described by Melvin Calvin and his team.
- The Calvin cycle consists of several enzyme-controlled stages.
Stages of the Calvin Cycle
- Carbon dioxide enters the leaf through stomata, dissolves in surrounding water, and diffuses into the stroma of chloroplasts.
- In the stroma, carbon dioxide reacts with ribulose bisphosphate (RuBP) using the enzyme ribulose bisphosphate carboxylase (rubisco), forming an unstable six-carbon compound.
- This six-carbon compound splits into two molecules of glycerate 3-phosphate (GP), a three-carbon compound.
- One ATP molecule from the light dependent reaction converts GP into triose phosphate (TP), also a three-carbon sugar.
- Reduced NADP contributes hydrogen to reduce GP to TP.
- Triose phosphate molecules pair up to form six-carbon (hexose) sugars.
- Six-carbon sugars can polymerize to create starch, a storage carbohydrate.
- Five out of every six TP molecules regenerate RuBP using remaining ATP, ensuring the cycle continues.
Synthesis of Organic Compounds
- Plants synthesize various organic molecules, including carbohydrates, lipids, and proteins, from Calvin cycle compounds.
- Carbohydrates like sucrose are created by combining glucose and fructose; glucose serves as a respiratory substrate.
- Starch (storage carbohydrate) and cellulose (cell wall component) are formed by polymerizing glucose differently.
- Lipids consist of glycerol and fatty acids derived from triose phosphate and glycerate 3-phosphate, respectively.
- Lipids serve for storage and structural functions in cell membranes.
- Proteins, essential for cell structure and enzymatic functions, are composed of amino acids produced from glycerate 3-phosphate through acetyl coenzyme A and Krebs cycle intermediates.
Light Independent Stage of Photosynthesis
- ATP and reduced NADP (NADPH H+) produced in the light dependent stage are essential for the light independent stage, also known as the Calvin cycle.
- This stage does not require light directly but relies on products from the light dependent stage, halting when light is absent.
- Occurs in the stroma of chloroplasts and was described by Melvin Calvin and his team.
- The Calvin cycle consists of several enzyme-controlled stages.
Stages of the Calvin Cycle
- Carbon dioxide enters the leaf through stomata, dissolves in surrounding water, and diffuses into the stroma of chloroplasts.
- In the stroma, carbon dioxide reacts with ribulose bisphosphate (RuBP) using the enzyme ribulose bisphosphate carboxylase (rubisco), forming an unstable six-carbon compound.
- This six-carbon compound splits into two molecules of glycerate 3-phosphate (GP), a three-carbon compound.
- One ATP molecule from the light dependent reaction converts GP into triose phosphate (TP), also a three-carbon sugar.
- Reduced NADP contributes hydrogen to reduce GP to TP.
- Triose phosphate molecules pair up to form six-carbon (hexose) sugars.
- Six-carbon sugars can polymerize to create starch, a storage carbohydrate.
- Five out of every six TP molecules regenerate RuBP using remaining ATP, ensuring the cycle continues.
Synthesis of Organic Compounds
- Plants synthesize various organic molecules, including carbohydrates, lipids, and proteins, from Calvin cycle compounds.
- Carbohydrates like sucrose are created by combining glucose and fructose; glucose serves as a respiratory substrate.
- Starch (storage carbohydrate) and cellulose (cell wall component) are formed by polymerizing glucose differently.
- Lipids consist of glycerol and fatty acids derived from triose phosphate and glycerate 3-phosphate, respectively.
- Lipids serve for storage and structural functions in cell membranes.
- Proteins, essential for cell structure and enzymatic functions, are composed of amino acids produced from glycerate 3-phosphate through acetyl coenzyme A and Krebs cycle intermediates.
General Features of Water
- Water is a dipolar molecule with an oxygen atom carrying a slight negative charge (Ƨ -) and hydrogen atoms carrying slight positive charges (Ƨ +).
- Polarity leads to the formation of hydrogen bonds, where water molecules are attracted to one another.
- Oxygen is more electronegative than hydrogen, causing uneven electron sharing; this results in the partial charges in the molecule.
- As an excellent solvent, water enables the transport of polar molecules and ions, dissolving substances like oxygen, carbon dioxide, amino acids, and glucose.
- Water has high melting and boiling points due to the significant energy required to break hydrogen bonds connecting the molecules.
- High surface tension arises from stronger cohesion between water molecules compared to their adhesion with air, forming a 'skin' on the surface.
Properties of Water
- Acts as an excellent solvent for ions and polar molecules, facilitating biochemical reactions in living cells by allowing reactants to dissolve and move freely.
- Maintains the stability of cell membranes, essential for cellular function.
- Functions as a transport medium:
- In animals, water carries digested food, hormones, antibodies, and waste in blood and lymphatic systems.
- In plants, water transports salts through xylem and sugars in phloem.
High Specific Heat Capacity
- Water has a high specific heat capacity, requiring 4200 joules to raise 1 kg of water by 1°C.
- This property enables water to resist temperature changes, stabilizing environments:
- Lakes and oceans experience slow temperature change, providing a stable habitat for aquatic life.
- Maintains constant temperatures in the bodies of living organisms, essential for biochemical reactions and optimal enzymatic activity.
Density and Freezing Point
- Ice floats on liquid water, creating an insulating layer, which protects aquatic life from freezing conditions.
- Low-density ice reduces the risk of aquatic organisms freezing completely during cold temperatures.
Cohesion and Surface Tension
- Cohesion refers to water molecules sticking together due to hydrogen bonds, contributing to water's overall cohesion.
- Adhesion is the attraction between water molecules and different substances, enhancing water interaction with the environment.
- High surface tension minimizes surface area due to stronger hydrogen bond attractions among water molecules compared to the attraction to air.
Implications for Aquatic Life
- Transparency of water allows sufficient light penetration for photosynthesis in aquatic organisms.
- Insulating properties from floating ice help maintain underlying water temperatures.
- High specific heat capacity makes water more resistant to temperature fluctuations, benefiting the functioning of enzymes in aquatic environments.
Transport of Molecules
- Water’s polar nature enables it to dissolve ions and polar compounds effectively.
- The positive hydrogen ends attract negatively charged ions (anions), while the negative oxygen end attracts positively charged ions (cations), facilitating nutrient transport in organisms.
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Description
Explore the light independent stage of photosynthesis, where ATP and NADPH are utilized to reduce carbon dioxide. Learn how this stage, occurring in the stroma of chloroplasts, is essential yet does not rely on direct light. Discover the impact of light absence on this crucial process.
