Photosynthesis, Respiration, and Limiting Factors

Comprehensive practice flashcards covering the mechanism of photosynthesis, chemical and word equations, uses of glucose, comparison with respiration, and limiting factors.

What is the biological definition of photosynthesis?

The process by which plants manufacture carbohydrates from raw materials using energy from light (or make their own food using water from the soil, carbon dioxide from the air, and light energy from the Sun inside the chloroplasts).

What do the root words "photo" and "synthesis" mean?

"Photo" means light, and "synthesis" means building or putting together.

What is the word equation for photosynthesis?

Carbon dioxide + Water $\rightarrow$ Glucose + Oxygen (requiring light energy and chlorophyll).

What is the balanced chemical symbol equation for photosynthesis?

$$6\text{CO}_2 + 6\text{H}_2\text{O} \rightarrow \text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2$$

What is the role of chlorophyll in photosynthesis?

It traps and converts/transfers light energy into chemical energy for the synthesis of sugars (carbohydrates).

How do water and carbon dioxide enter the plant for photosynthesis?

Water is absorbed from the soil by root hair cells via osmosis, and carbon dioxide enters the leaf through the stomata via diffusion.

How does oxygen leave the leaf following photosynthesis?

Oxygen moves out of the leaf by diffusion.

What are the six uses of glucose produced by photosynthesis?

1. Respiration to provide energy\n2. Stored as starch\n3. Cellulose to build cell walls\n4. Sucrose for transport in the phloem\n5. Nectar to attract insects for pollination\n6. Combined with nitrate ions to make amino acids for growth and tissue repair (adding to plant biomass).

How do photosynthesis and respiration compare in terms of gas exchange?

Photosynthesis takes in $\text{CO}_2$ and releases $\text{O}_2$, while respiration takes in $\text{O}_2$ and releases $\text{CO}_2$.

How do photosynthesis and respiration compare in timing and plant location?

Photosynthesis occurs during the day only and solely in leaves; respiration occurs all the time (day and night) and in all parts of the plant.

Which cellular organelles carry out photosynthesis and respiration?

Photosynthesis occurs inside chloroplasts, while respiration occurs inside mitochondria.

What are the three main limiting factors of photosynthesis?

Light intensity, carbon dioxide concentration, and temperature.

Why does the rate of photosynthesis increase with increasing light intensity at low light levels?

Because light intensity is the limiting factor; more light energy is absorbed by chlorophyll and converted into chemical energy to make glucose.

Why does the rate of photosynthesis level off at high light intensity or high carbon dioxide concentration?

That factor is no longer the limiting factor; another factor (such as temperature or carbon dioxide/light) has become limiting.

Why is the rate of photosynthesis low at low temperatures?

Molecules have low kinetic energy, decreasing the frequency of effective collisions between enzymes and substrates, resulting in less fitting into active sites and fewer enzyme-substrate complexes forming.

What causes the rate of photosynthesis to increase as temperature rises toward optimum?

Molecules gain kinetic energy, increasing effective collisions and enzyme-substrate complexes; additionally, carbon dioxide molecules gain kinetic energy, speeding diffusion through stomata.

What occurs when the temperature exceeds the optimum temperature for photosynthesis?

The active site changes shape and is no longer complementary to the substrate, preventing enzyme-substrate complex formation; the enzyme becomes denatured and photosynthesis stops.