CHAPTER 4 Flashcards
What is photosynthesis?
The process of converting sunlight energy into chemical energy.
Which organisms are capable of photosynthesis?
Plants, algae, and cyanobacteria.
Define autotrophs.
Organisms that can produce their own food.
Define heterotrophs.
Organisms that cannot produce their own food.
Where does photosynthesis primarily occur in plants?
In the mesophyll layer within the leaves.
What is the specific organelle where photosynthesis takes place?
Chloroplast.
True or False: Human cells can perform photosynthesis.
False.
How is light energy described?
A type of kinetic energy that we can see.
What is the relationship between wavelength and energy in light?
The longer the wavelength, the lower the energy.
What are photons?
A package of light.
What is the role of pigments in plants?
To absorb light energy.
Define photosystems.
Protein complexes consisting of proteins and pigments that can absorb light energy and convert it into chemical energy.
How many photosystems are there in plants?
2 Photosystems.
What do light-harvesting complexes do?
They pass light energy to the reaction center.
What is contained in the reaction center of a photosystem?
A special pair of chlorophyll a molecules that can give up electrons.
What is the first step of light-dependent reactions?
Photosystem II captures sunlight and excites electrons.
What is the equation for water splitting in photosynthesis?
2 H2O + light → O2 + 4e−.
What is the key product of the light-dependent reactions?
ATP, NADPH, and oxygen.
What does chemiosmosis refer to?
The diffusion of ions across a semipermeable membrane.
What is the end product of the Calvin cycle?
Glyceraldehyde 3-phosphate (G3P).
What is RuBisCO?
An enzyme involved in carbon fixation during the Calvin cycle.
Fill in the blank: The Calvin cycle does not directly require light but relies on the products of the light-dependent reactions, _______ and NADPH.
ATP.
What is the relationship between light-dependent reactions and the Calvin cycle?
Light-dependent reactions provide ATP and NADPH for the Calvin cycle.
What is the major precursor for the synthesis of carbohydrates produced by photosynthesis?
Glucose.
True or False: Photosynthesis and cellular respiration are interconnected processes.
True.
What does G3P leave the Calvin cycle to produce?
Glucose.
What is the first stage of the Calvin cycle?
Carbon Fixation: This stage begins with a molecule called ribulose-bisphosphate (RuBP), a five-carbon sugar. The enzyme RuBisCO catalyzes the reaction between RuBP and carbon dioxide (CO₂) from the atmosphere, forming an unstable six-carbon intermediate that splits into two molecules of 3-phosphoglycerate (3-PGA). Therefore, carbon dioxide is ‘fixed’ from an inorganic form into an organic molecule.
What occurs during the Reduction/Sugar Generation stage of the Calvin cycle?
Each molecule of 3-phosphoglycerate (3-PGA) is phosphorylated by ATP to form 1,3-bisphosphoglycerate (1,3-BPG). Then, NADPH reduces 1,3-bisphosphoglycerate (1,3-BPG) to form glyceraldehyde 3-phosphate (G3P). For every three molecules of CO₂ that enter the cycle, six molecules of G3P are produced, with one G3P molecule leaving the cycle to be used to make glucose and other organic molecules.
What happens in the Regeneration stage of the Calvin cycle?
The remaining five molecules of glyceraldehyde 3-phosphate (G3P) are used in a series of reactions that require ATP to regenerate ribulose-bisphosphate (RuBP). This regeneration of RuBP is crucial because it allows the Calvin cycle to continue fixing carbon dioxide.
