Understanding Photosynthesis

What are the main products of the light-dependent reactions?

• Oxygen, glucose, and pyruvate

• Carbon dioxide, NADH, and glucose

• Oxygen, ATP, and NADPH

• Glucose, ATP, and FADH2

Answer explanation

The light-dependent reactions of photosynthesis produce oxygen as a byproduct, while generating ATP and NADPH, which are essential for the subsequent light-independent reactions. Thus, the correct answer is Oxygen, ATP, and NADPH.

Where do the light-dependent reactions occur in the plant cell?

• Cytoplasm of the cell

• Nucleus of the cell

• Thylakoid membranes of the chloroplasts

• Mitochondrial membranes

Answer explanation

The light-dependent reactions occur in the thylakoid membranes of the chloroplasts, where sunlight is captured and converted into chemical energy. This is essential for the photosynthesis process.

What is the primary function of chlorophyll in photosynthesis?

• To store energy for later use.

• To release oxygen during photosynthesis.

• The primary function of chlorophyll in photosynthesis is to absorb light energy.

• To provide structural support to the plant.

Answer explanation

The primary function of chlorophyll in photosynthesis is to absorb light energy, which is essential for converting sunlight into chemical energy, enabling the plant to produce food.

Describe the role of ATP and NADPH in photosynthesis.

• ATP is a waste product of photosynthesis.

• NADPH is used to absorb sunlight during photosynthesis.

• ATP provides energy, while NADPH provides reducing power in photosynthesis.

• ATP and NADPH are both used to transport oxygen in plants.

Answer explanation

ATP provides the energy needed for various processes in photosynthesis, while NADPH acts as a reducing agent, supplying the electrons required for the conversion of carbon dioxide into glucose.

What are the main stages of the light-independent reactions?

• Light absorption, electron transport, and ATP synthesis

• NADPH production, oxygen release, and glucose formation

• Chlorophyll activation, water splitting, and carbon release

• The main stages are carbon fixation, reduction phase, and regeneration of RuBP.

Answer explanation

The main stages of the light-independent reactions, also known as the Calvin cycle, are carbon fixation, reduction phase, and regeneration of RuBP. This process does not involve light directly, unlike the light-dependent reactions.

How does carbon dioxide enter the plant for photosynthesis?

• Carbon dioxide is taken in through flowers.

• Carbon dioxide is absorbed by leaves directly.

• Carbon dioxide enters through roots.

• Carbon dioxide enters the plant through stomata.

Answer explanation

Carbon dioxide enters the plant through stomata, which are small openings on the leaves. This process allows the plant to absorb CO2 from the air, essential for photosynthesis.

What is the overall equation for photosynthesis?

• C6H12O6 + 6O2 -> 6CO2 + 6H2O + light energy

• 6CO2 + 6H2O + light energy -> C6H12O6 + 6O2

• 6O2 + 6H2O + light energy -> C6H12O6 + 6CO2

• 6CO2 + 6H2O -> C6H12O6 + 6O2 + heat

Answer explanation

The correct equation for photosynthesis shows that carbon dioxide (6CO2) and water (6H2O) combine with light energy to produce glucose (C6H12O6) and oxygen (6O2). This reflects the process of converting light energy into chemical energy.

List two factors that can affect the rate of photosynthesis.

• Light intensity, Carbon dioxide concentration

• Soil moisture levels

• Oxygen levels

• Temperature fluctuations

Answer explanation

Light intensity and carbon dioxide concentration are key factors that directly influence the rate of photosynthesis. Higher light intensity increases energy for photosynthesis, while more carbon dioxide enhances the process.

How does temperature influence photosynthesis?

• Temperature has no effect on photosynthesis.

• Higher temperatures always increase photosynthesis rates.

• Temperature only affects water absorption in plants.

• Temperature influences photosynthesis by affecting enzyme activity and stomatal function.

Answer explanation

Temperature affects photosynthesis by influencing enzyme activity, which is crucial for the biochemical reactions involved, and stomatal function, which regulates gas exchange necessary for photosynthesis.

Why is photosynthesis important for life on Earth?

• Photosynthesis consumes oxygen and releases carbon dioxide.

• Photosynthesis occurs only at night.

• Photosynthesis is only important for aquatic life.

• Photosynthesis is crucial for life on Earth as it produces oxygen and is the foundation of the food chain.

Answer explanation

Photosynthesis is vital as it produces oxygen, which is essential for most life forms, and it forms the base of the food chain, supporting both terrestrial and aquatic ecosystems.