Chapter 7: Photosynthesis and Light Energy

Flashcards covering plant adaptations, light and the electromagnetic spectrum, stages of photosynthesis, and stomatal function based on the lecture notes.

How is photosynthesis defined in terms of energy transformation?

Photosynthesis is the conversion of light energy into chemical energy, effectively getting food from light.

What are the primary reactants and products in the general equation for photosynthesis?

Carbon dioxide, water, and light energy go in, producing sugar (glucose) and oxygen.

What unique structural adaptation for photosynthesis is seen in the rainforest orchid mentioned in the lecture?

The orchid consists entirely of roots growing on the surface of a tree without any leaves, placing its chloroplasts directly in its roots.

How does the non-green plant known as the ghost pipe obtain its sugar and nutrients?

It acts as a parasite on a fungus that shares a mutualistic relationship with a tree; the ghost pipe takes both nutrients and sugars directly from the fungus without performing photosynthesis.

Where does a generic tree take in carbon dioxide and water for photosynthesis?

It pulls in carbon dioxide from the air through its leaves and absorbs water primarily through its roots.

How are the waste products of cellular respiration related to the process of photosynthesis?

The waste products of respiration (water and carbon dioxide) serve as the reactants that enter photosynthesis.

Why does chlorophyll appear green to the human eye?

Chlorophyll absorbs red, orange, yellow, blue, and purple wavelengths of white light, while reflecting green light.

What does the Lambeau Field football analogy illustrate regarding leaves changing color in the autumn?

As green chlorophyll breaks down and leaves the leaf (like Packer fans leaving the stadium), underlying pigments that were present the entire time—such as red in maples and yellow in aspens—are no longer masked.

What two models of light are described in the lecture?

Light can be considered as a wave or as a photon (a packet or particle of energy).

Why do bones appear white on an X-ray image?

Bones absorb the high-energy X-rays, preventing them from reaching the detector, which results in a white area on the reverse image.

How does the energy of a photon of violet light compare to that of red light?

One photon of violet light possesses $2$ times the energy of red light, making violet the most energetic and red the least energetic of visible light.

What is the typical energy range of visible light compared to ultraviolet ($\text{UV}$) light?

Visible light carries between $2\text{ to }3\text{ electron volts}$, whereas $\text{UV}$ light carries up to about $124\text{ electron volts}$.

How does ultraviolet ($\text{UV}$) radiation cause cellular damage and mutations in skin?

It penetrates into the living layer of skin and breaks the double-stranded $\text{DNA}$ molecule; if the cell reassembles the $\text{DNA}$ incorrectly, mutations occur.

Why do certain plants growing on high-altitude equatorial mountains absorb ultraviolet ($\text{UV}$) radiation?

They possess pigments that absorb $\text{UV}$ radiation not for photosynthesis, but to convert it into heat to keep warm.

What are the two main stages of photosynthesis?

The light reactions and the Calvin cycle.

What two energy-storing molecules are generated by the light reactions?

$\text{ATP}$ and $\text{NADPH}$.

What molecule is split during the light reactions to produce oxygen gas?

Water ($H_2O$) molecules are split to release oxygen.

What is the primary role of $\text{ATP}$ in the Calvin cycle?

It supplies the chemical energy needed to join carbon dioxide molecules together into a three-carbon sugar precursor.

By what mechanism do guard cells control the opening and closing of stomata?

When filled with water, guard cells become stiff from internal pressure and open; when dried out or losing water, they collapse and close.

Why do clover leaves have stomata located exclusively on the underside of their leaves?

Their flat orientation low to the ground exposes the top to direct sunlight; keeping stomata on the bottom shields them from the sun and prevents water loss.