Plants Unit Activity 4.5b: Explaining How Plants Grow: Biosynthesis Environmental Literacy Project Michigan State University

What molecules make up the dry mass of plants? FATS PROTEIN CELLULOSE (FIBER) GLUCOSE (SUGAR) STARCH Garden plants are usually 85-90% water. The dry mass (10-15%) is mostly large organic molecules.

What atoms make up the dry mass of plants? Atoms by dry mass: carbon (45%), oxygen (45%), hydrogen (6%), nitrogen (2%) and other elements (2%). FATS PROTEIN CELLULOSE (FIBER) GLUCOSE (SUGAR) STARCH Molecules in plants:

What atoms make up the dry mass of plants? Atoms by dry mass: carbon (45%), oxygen (45%), hydrogen (6%), nitrogen (2%) and other elements (2%).

Where do the atoms in the dry mass of a plant come from? Atoms by dry mass: carbon (45%), oxygen (45%), hydrogen (6%), nitrogen (2%) and other elements (2%).

Plants make glucose from carbon dioxide and water in their leaves.

After CO 2 and H 2 O go through photosynthesis to make sugar (glucose). Where does the sugar go?

Plants use food in two ways 8 FoodTo Cells Materials for growth: Biosynthesis Energy: Cellular respiration

Sap moving through the phloem carries glucose (sugar) to all parts of plant bodies. Water moving through the xylem carries minerals to all parts of plant bodies. How do glucose water, and minerals move for a plant stem cell to grow?

waterminerals glucose

How do plants use food and minerals as materials for growth? 11

Plants use food in two ways 12 FoodTo Cells Materials for growth: Biosynthesis Energy: Cellular respiration

Answering the Three Questions for Biosynthesis 13

Where are atoms moving from? Where are atoms moving to? The Movement Question

Which atoms and molecules move so that plants can grow through biosynthesis? waterminerals glucose

How do glucose water, and minerals move for a plant stem cell to grow? waterminerals glucose

The Carbon and Energy Questions: What happens to carbon atoms and chemical energy during biosynthesis? Chemical change Sugar and minerals go into cells, but don’t come out. What happens inside the cells?

The Carbon and Energy Questions Carbon: How do atoms use glucose and minerals to make large organic molecules? Energy: Large organic molecules (such as starch, cellulose, fats, and proteins) high-energy (C-C and C-H) bonds. Where does the chemical energy in the bonds come from?

Plants make large organic molecules from glucose and minerals The result of photosynthesis is glucose, then plants use the glucose to make large organic molecules GLUCOSE (SUGAR) PROTEINS Plus nitrogen FATS STARCH CELLULOSE

Chemical change Products Large organic molecules (+ water) Reactants 20 What happens to carbon atoms and chemical energy in biosynthesis? Small organic molecules

Chemical change Products Large molecules (+ water) Reactants 21 What happens to carbon atoms and chemical energy in biosynthesis? Small organic molecules Carbon atoms stay in organic molecules with high-energy bonds

Revisiting the Predictions Tool Carbon atoms (45% of the dry mass of a garden plant) come from _________. Explain how carbon atoms get to plant cells. Oxygen atoms (45% of the dry mass of a garden plant) come from _________. Explain how carbon atoms get to plant cells. Hydrogen atoms (6% of the dry mass of a garden plant) come from _________. Explain how hydrogen atoms get to plant cells. Nitrogen, phosphorous, and all other atoms (4% of the dry mass of a garden plant) come from _________. Explain how other atoms get to plant cells. The chemical energy in plants’ organic molecules comes from ___________. Explain how energy gets to plant cells. 22

Pulling it together Plant roots are constantly emitting small amounts of CO 2 into the soil. Tell a complete story of where the carbon atoms in that CO 2 comes from. – Tell a story that traces a carbon atom from CO 2 in the air around a plant’s leaf to CO 2 in the soil around a plant’s root. 23