3.5 Photosynthesis - Developing Questions

How do photosynthetic organisms contribute to the energy flow within an ecosystem?

• Through chemosynthesis, they break down chemicals from

  hydrothermal vents providing energy for deep-sea ecosystems.

• They consume organic compounds from other organisms converting it

  back into light energy used by plants.

• They convert light energy into chemical energy that can be used by themselves as well as heterotrophic organisms within the ecosystem.

• They primarily decompose organic matter releasing nutrients into the

  soil for autotrophs to absorb.

Answer explanation

In an ecosystem, photosynthetic organisms, such as plants or algae, capture light energy through photosynthesis turning it into chemical energy stored in sugar molecules; this stored chemical energy is then available for consumption by heterotrophs or themselves for growth—thereby fueling the ecosystem's food web.

Tags

NGSS.HS-LS1-5

NGSS.HS-LS2-5

Which proteins in the thylakoid membrane transfer electrons from water to the electron transport chain during light-dependent reactions?

• ATP synthase complex proteins

• NADPH Reductase complex proteins

• Photosystem II complex proteins

• Photosystem I complex proteins

Answer explanation

The Photosystem II complex proteins initiate the transport of electrons by splitting water, which is an essential step in the light-dependent reactions.

How does the presence of a large number of thylakoids in chloroplasts affect the efficiency of photosynthesis?

• Has no effect, since photosynthesis rate is not influenced by thylakoid number.

• Decreases, because too many thylakoids can block sunlight from reaching the stroma.

• Increases, because a larger surface area allows more space for light absorption and electron transport.

• Decreases, as it reduces the amount of carbon dioxide available for the Calvin cycle.

Answer explanation

Thylakoids contain chlorophyll and are where light-dependent reactions occur; more thylakoids mean more space for these reactions to take place, thus increasing efficiency.

Tags

NGSS.HS-LS1-5

Which of the following is NOT a side reactant involved in photosynthesis?

• Water

• Nitrogen

• Carbon dioxide

• Glucose

Answer explanation

Photosynthesis involves the absorption of light energy and its transformation throughout two major stages: the light-dependent reactions and the Calvin cycle. The key substances needed for the process include water, carbon dioxide, and oxygen (produced), with glucose formed. Thus, nitrogen is not directly utilized in photosynthesis.

Tags

NGSS.MS-LS1-6

NGSS.MS-LS2-3

What is a primary ecological consequence if there were no producers capable of performing photosynthesis?

• Animals could survive off mineral nutrient cycling without relying any longer upon photosynthetically derived nutrients.

• Decomposers would over-abundance ecosystems, breaking down dead materials rapidly and generating new sources of nourishment.

• All life forms dependent on oxidative phosphorylation would eventually perish due to lack of carbohydrates.

• Biogeochemical cycles would continue unaffected since decomposer activity supplies all necessary ecosystem energies.

Answer explanation

Producers perform a critical role within ecosystems by converting the sun's energy into chemically bound forms such as sugars that are essential for supporting both directly and indirectly the vast majority of life on Earth. The absence of primary productivity would result in the ultimate collapse of trophic structures reliant on said production.

Tags

NGSS.HS-LS1-5

NGSS.HS-LS2-5

NGSS.HS-LS2-6

Why do plants appear green to humans under white light?

• Green wavelengths are only used during cellular respiration not photosynthesis

• Plants lack pigments that can absorb green wavelegths

• Chlorophyll absorbs green wavelengths most effectively

• Chlorophyll reflects green wavelengths of light

Answer explanation

Green light is reflected more than others because chlorophyll absorbs red and blue wavelengths more than others, projecting more green.

Tags

NGSS.MS-LS1-6

During photosynthesis, what process produces oxygen as a byproduct?

• Reduction phase of Calvin Cycle

• Photolysis of water

• Regneration phase of RuBP

• Carbon fixation in Calvin Cycle

Answer explanation

The photolysis or splitting of water molecules during the light-dependent reactions releases oxygen as a byproduct.

What would be a direct consequence of closing the stomata on a hot, dry day for a plant undergoing photosynthesis?

• Increased water loss through transpiration

• Increased absorption of CO2 enhancing the Calvin cycle

• Reduced uptake of CO2 leading to decreased rate of photosynthesis

• Unaffected rate of photosynthesis due to stored carbon dioxide use

Answer explanation

Closing stomata conserves water but also limits CO₂ intake, directly affecting the rate of photosynthesis since CO₂ is needed for the Calvin cycle.

Tags

NGSS.HS-LS2-5

Which compound provides the carbon atoms that are incorporated into sugar molecules in the Calvin cycle?

• CO₂

• O₂

• NADPH

• RuBP

Answer explanation

Carbon dioxide (CO₂) supplies carbon atoms for carbon fixation phase of the Calvin cycle, resulting in glucose production.

Tags

NGSS.HS-LS2-5

Which part of a plant cell primarily contains pigments that absorb solar energy for photosynthesis?

• Mitochondrial inner membranes

• Thylakoid membranes within chloroplasts

• The central vacuole membrane

• The plasma membrane surrounding the cell

Answer explanation

Thylakoid membranes within chloroplasts contain chlorophyll and other pigments that capture solar energy necessary for photosynthesis.

Tags

NGSS.HS-LS1-5