Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
The leaf is the primary organ for photosynthesis, adapted to maximize the absorption of light and the intake of .
The Waxy Cuticle is a waterproof layer that prevents excessive water loss via evaporation while remaining transparent to allow light through.
The Upper Epidermis is a thin, transparent layer of cells that protects the inner tissues and allows light to reach the photosynthetic layers.
The Palisade Mesophyll consists of tall, columnar cells packed with chloroplasts. They are located near the top of the leaf to maximize light absorption for the reaction .
The Spongy Mesophyll contains loosely packed cells with large air spaces, increasing the surface area for the diffusion of into cells and out of cells.
Stomata are small pores, mostly on the lower epidermis, that allow gas exchange ( in, and vapor out).
Guard Cells control the opening and closing of stomata to balance gas exchange with the conservation of .
The Vascular Bundle contains the Xylem, which transports and dissolved mineral ions, and the Phloem, which transports manufactured food like sucrose.
📐Formulae
💡Examples
Problem 1:
Explain why the palisade mesophyll cells are arranged vertically and packed tightly together.
Solution:
Vertical arrangement and tight packing ensure that a large number of chloroplasts are exposed to direct sunlight. This maximizes the light energy captured to convert and into .
Explanation:
The columnar shape allows light to pass through the length of the cell, hitting multiple chloroplasts, which increases the efficiency of the light-dependent stage of photosynthesis.
Problem 2:
A leaf is tested for starch after being kept in the dark for 24 hours. What is the result and why?
Solution:
The iodine test will remain yellow-brown (negative), indicating no starch is present. This is because the plant was 'destarched'.
Explanation:
Without light, the plant cannot perform photosynthesis to produce . It converts existing starch reserves back into glucose for respiration to maintain cellular activities, depleting the starch stored in the leaf.
Problem 3:
How does the structure of the spongy mesophyll assist in the movement of ?
Solution:
The large internal surface area and air spaces allow to diffuse rapidly from the stomata to the palisade cells.
Explanation:
Diffusion is more efficient in gas than through liquid or cell layers. The air spaces ensure that reaches the cell membranes of the mesophyll cells quickly for the photosynthetic reaction.