Plants vs. Fungi: While plants and fungi may look superficially similar, they are structurally entirely different. Plants build strong, rigid walls of Cellulose (a tough glucose polysaccharide). Fungi construct walls of Chitin (a durable, nitrogen-containing sugar polymer also found in crab shells). Color these structures below!
Color the woody stem, realistic leaves, and energy-storing roots of this plant.
🟡 Leaf Waxy Cuticle Layer
🔵 Stem Cellulose Cell Walls
🔵 Root Starch Reserves
Coloring Guide:
Cellulose (Carb): Color the parallel **stem fibers** blue.
Lipids: Color the glossy **leaf wax borders** yellow.
Starch (Carb): Color the underground **root fibers** blue.
STOP & JOT #3
Animals use tough proteins (collagen/muscles) to stand upright. Why can plants use cellulose (a carbohydrate) to maintain their rigid structure without proteins?
Color the structural cap, gills, and underground hyphae network of this mushroom.
🟡 Cap Lipid Protective Skin
🔵 Stalk & Gills (Chitin Walls)
🔵 Mycelium Glycogen Fibers
Coloring Guide:
Chitin (Carb): Color the stalk and **gill structural zones** blue.
Lipids: Color the thick protective **cap skin boundary** yellow.
Glycogen (Carb): Color the underground **mycelial roots** blue.
STOP & JOT #4
Fungal cell walls are made of Chitin (which also forms hard crab/insect shells). What advantage does chitin's durability give to mushrooms growing in damp soil?
1. Cellulose vs. Chitin Chemical Strategy:
Both Cellulose and Chitin are long chains of glucose sugars (carbohydrates) utilized for structural defense rather than direct digestion. Why do plants and fungi rely on carbohydrates rather than bones or muscles to protect themselves?
2. Fungal Dietary Storage:
Fungi are evolutionarily closer to animals than plants. How does the fact that mushrooms store excess energy as glycogen (just like animal livers and muscles) instead of plant starch support this evolutionary relationship?
Anatomy Comparison Question: How does a microscopic cell membrane serve a similar protective purpose to a polar bear's layer of fat and blubber?
Needs Improvement (1 pt): Student states both protect the cell/organism, but fails to mention hydrophobic boundaries, lipid chemistry, or insulation.
Approaching Standard (2 pts): Student explains both act as waterproof boundaries because lipids do not mix with water. Briefly mentions blubber keeps the bear warm.
Meets Standard (3 pts): Full connection. Explains both establish waterproof (hydrophobic) boundaries. The blubber forms an organism-scale boundary protecting against heat loss, while the cell membrane regulates internal cellular homeostasis.
Teacher Implementation Guide & Answer Key • PAGE 2
HS Biology / Unit 2: Biochemistry
Page 2 focuses heavily on structural carbohydrates—specifically Cellulose in Plants and Chitin in Fungi. These are critical evolutionary markers showing how different kingdoms have adapted chemical polymers to build upright shapes without skeletons.
🔵 Cellulose (Stem)
Color the vertical stem fibers blue. Explain that cellulose microfibrils form highly-rigid cell walls, giving herbaceous stalks physical strength to grow tall.
🟡 Lipids (Leaf Cuticle)
Color the outer glossy leaf cuticle borders yellow. Explain that hydrophobic waxes prevent excessive water evaporation and protect against solar burning.
🔵 Starch (Roots)
Color the underground root system blue. This illustrates that plants store long-term excess glucose as highly-branched starch reserves in the soil.
🔵 Chitin (Stalk / Gills)
Color the structural stalk and gill zones blue. Explain that chitin is a rugged carbohydrate that forms tough fungal cell walls to hold upright structures.
🟡 Lipids (Cap Skin)
Color the upper curved cap skin boundary yellow. Ergosterols (lipids) regulate membrane fluidity and protect spores from drying out before distribution.
🔵 Glycogen (Mycelium)
Color the subterranean mycelial fibers blue. Note that fungi store excess carbohydrates as glycogen, matching animal livers rather than plants.
STOP & JOT #3: Plants & Cellulose
Ideal Answer: Unlike animals, which are motile and require elastic muscles/tendons (proteins) for locomotion, plants are static. Plants construct hard, overlapping, box-like cell walls of cellulose. When filled with water, these walls build turgor pressure, allowing a massive sunflower to stay rigid and upright using simple glucose sugars instead of muscle tissue.
STOP & JOT #4: Fungi & Chitin
Ideal Answer: Fungi grow in extremely damp, competitive soil. Chitin is highly resistant to enzymes, bacterial rot, and water absorption. Its tough chemical structure ensures that the mushroom stalk does not dissolve or decay in saturated mud, allowing the mushroom cap to remain standing long enough to release its spores.
Q1: Structural Carbohydrate Strategy:
Look for students to identify that carbohydrates are highly cost-efficient and easy to construct. Carbon, hydrogen, and oxygen are abundant in plants (photosynthesis) and fungi. Building a cellulose/chitin matrix requires far less nitrogen and energy than building complex animal protein skeletons or muscles.
Q2: Fungal Glycogen Evolutionary Link:
Students should connect glycogen storage to the evolutionary tree. Since fungi store excess energy as glycogen (just like animals) rather than starch (like plants), it biochemically proves that fungi and animals share a more recent common ancestor than either group does with the plant kingdom.
