Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
Photosynthesis is the process by which plants manufacture carbohydrates from raw materials ( and ) using energy from light.
Chlorophyll is a green pigment found in chloroplasts that absorbs light energy and converts it into chemical energy for the synthesis of glucose ().
The process is divided into light-dependent reactions and light-independent reactions (Calvin Cycle).
Limiting factors determine the rate of photosynthesis; these include light intensity, concentration, and temperature.
Gaseous exchange occurs through the stomata, where diffuses into the leaf and diffuses out.
Glucose produced during photosynthesis is used for respiration, converted into starch for storage, used to make cellulose for cell walls, or turned into sucrose for transport in the phloem.
The internal structure of a leaf is adapted for photosynthesis: the palisade mesophyll contains many chloroplasts, and the spongy mesophyll has air spaces for gas diffusion.
📐Formulae
💡Examples
Problem 1:
Explain why the rate of photosynthesis levels off even if the light intensity continues to increase at a constant temperature of and concentration.
Solution:
The rate levels off because light intensity is no longer the limiting factor. Another factor, such as concentration or temperature, has become the limiting factor.
Explanation:
According to the principle of limiting factors, the rate of a process is restricted by the factor at its least favorable value. Once light is abundant, the enzymes or the availability of molecules restrict further increases in the reaction rate.
Problem 2:
A student measures the oxygen production of an aquatic plant. At from a light source, the plant produces bubbles per minute. If the distance is increased to , what is the expected change in light intensity?
Solution:
The light intensity will decrease by a factor of (it becomes of the original intensity).
Explanation:
Light intensity follows the inverse square law: . Since the distance doubled ( to ), the intensity decreases by .
Problem 3:
Why must a leaf be boiled in ethanol before performing the iodine test for starch?
Solution:
The leaf is boiled in ethanol to remove the chlorophyll ().
Explanation:
Chlorophyll is a green pigment that would mask the color change of the iodine solution (from brown to blue-black). Removing the pigment ensures that any color change resulting from the presence of starch is clearly visible.