We know that Bernadette loves trees – but I do too! Every time we talk about photosynthesis in
BBtHk, I think about growing up in Northern California, surrounded by the tallest trees in the
world (Coastal Redwoods, which can get close to 400 feet tall). I remember learning about how
they are still undergoing photosynthesis to grow (just like any other plant) but it wasn't until I
was in graduate school that I really started to think about how they and their larger (by mass)
cousins, the giant sequoias, get so big! Just for reference (for those of you who haven't been to
CA to see these natural wonders), giant sequoias can get almost 300 feet tall, 25 ft in diameter
and weigh over two million pounds! They can have 1-2 billion leaves (needles) for undergoing
photosynthesis and are truly breathtaking to walk among. But how did they get so big? Let's
explore!
1. Below is the formula for photosynthesis.
a) Please fill in all the blanks with chemical symbols (you will just re-write the entire
formula in your submission) and label each component [with words, indicate the name of
each component]:
6___+6___ + ___ --> _______+6___
b) Is this reaction endothermic or exothermic? [Explain briefly]
c) Which part of the reaction is adding mass to the tree? [Hint: you can ignore the water in
the tree]
d) What molecule (on the reactant side) is most responsible for the gain in mass? In other
words, thinking back to the photosynthesis equation, where does the dry mass (non-water
mass) of the tree come from? [Explain in detail; Hint: this might be a great place to re-
read “What’s gotten into you”?]
e) If you were writing a children’s book about photosynthesis (which some of you might do
for your final project), how would you explain where the mass of a giant redwood tree
comes from (now, without the chemical equation or any specific molecules)? [seriously,
don’t use an equation or specific molecule