Download Today is Friday (!), November 5th, 2010

In This Lesson:
Photosynthesis
(Lesson 2 of 3)
Today is Thursday,
October 29th, 2015
Pre-Class:
Why are plants green?
(Or why are the green parts of them green, at least?)
Other stuff:
Grab a [small] paper towel for your pair.
Today’s Agenda
• Photosynthesis
• Photosynthesis
• And maybe flamingos.
http://www.harunyahya.com/kids/pictures/wallpaper1024/flamingo.jpg
By the end of this lesson…
• You should be able to identify the general
input and output of the photosynthesis
reactions.
ATP Review
• Think of ATP (Adenosine Triphosphate) as a molecule
like a chocolate bar.
– “Not another analogy!”
• The cell can break off a square to make it ADP.
– That releases energy.
• The cell can put a square on (add a phosphate group
to ADP, making ATP), but that’s hard to do.
– You’d need to melt it down in an oven and re-form it.
– That absorbs (uses) energy.
Simple Diagram
(worth sketching…no, really)
http://mrsec.wisc.edu/Edetc/nanoquest/molecular_motor/images/atpenergy.jpg
Watching Plants Grow
• First, where is this in my book?
– P. 204 and following…
• As usual, here are the historic figures related
to Photosynthesis:
– Van Helmont
– Priestley
– Ingenhousz
– [your name here]
1600s: Jan van Helmont
• Belgian physician – tries to figure out if
plants take mass from soil to grow so
large.
• Measured soil, planted a seed, and
watered it.
• Then he waited five years (!). The soil
weighed the same as it did five years
earlier.
• CONCLUSION
– The plant is using water (hydrate) to grow.
– Importantly, plants gain their mass largely
from CO2, not from water.
– Jan van Helmont also coined the word “gas.”
http://2.bp.blogspot.com/_XU9nEwykZRc/SkO5s53xzgI/AAAAAAAAACU/gUPGWU3wpbo/s320/van_Helmont.jpg
Floating head!
Spooky…
1700s: Joseph Priestley
• English minister – noticed that a
candle will go out if you put a glass
‘allo
jar over it.
guv’nah!!
– Flames need oxygen as fuel.
• However, if you put a leaf in there
(he used mint), the candle burns
longer.
• CONCLUSION
– Plants produce oxygen.
– Priestley also named rubber. Hmmph.
http://explorepahistory.com/images/ExplorePAHistory-a0h1r8-a_349.jpg
Aside: Great Moments in Science
• Turns out that Priestley wasn’t the
first to discover oxygen, though he
got all the credit.
• Previously, Carl Scheele discovered
oxygen and seven other elements,
unfortunately receiving credit for
none of them.
• Also unfortunate: Scheele had a
habit of tasting all the chemicals
with which he worked.
– He was found dead at the age of 43
surrounded by several toxic
chemicals.
1700s: Jan Ingenhousz
• Dutch scientist – noticed that air
bubbles only form around aquatic
(underwater) plants when they are
in sunlight.
– The air bubbles are oxygen from
photosynthesis.
• No bubbles formed in darkness.
• CONCLUSION
– Plants need sunlight to make oxygen.
http://0.tqn.com/d/chemistry/1/0/W/1/1/Jan_Ingenhousz.jpg
I am
grayscale.
2015: You.
• Here’s an interesting question:
– Suppose you put soil and some water in a clear jar.
– Then you plant a seedling in that soil.
– Then you put a lid on the jar, sealing the air.
– Lastly, you set it on a windowsill so it gets a
normal amount of light and heat.
• What happens?
The Magic Photosynthesis Machine
?
INPUT
YE OLDE
PHOTOSYNTHESIS
MACHINE
?
OUTPUT
Photosynthesis: An Outline
• Photosynthesis is basically this:
• 6CO2 + 6H2O + [LIGHT]  C6H12O6 + 6O2
– In other words, it’s a conversion of light energy to
chemical energy.
– Plants use it to convert and store energy.
• What you should do is this:
– Write down the chemical formula.
– Write down the formula in English.
– Draw the formula in mini-diagrams.
• (2 minutes to work)
Photosynthesis
• First, some review: (whiteboards)
– In which organelle does photosynthesis occur?
– What is a pigment?
– What’s the name of the pigment inside
chloroplasts?
– What color is it?
• Chlorophyll appears green to us because it is reflecting
green light. Therefore, it’s absorbing every other color
but green.
The Big Aside
• TED: David Gallo – Underwater Astonishments
• Other people’s colors
– Do I See Colors The Same Way You Do?
– A Bee’s Eye View article
• Ishihara Test
• Stop sign color experiment and night vision
– TED: Beau Lotto – Optical Illusions
•
•
•
•
Primary colors
Upside-down perception
Vision correction
Vision anomalies
– TED: Michael Mauser – Floaters
Ishihara Test
http://www.toledo-bend.com
Ishihara Test
http://www.toledo-bend.com
Perception
• The image of the world around you strikes the
retina in the back of the eye upside-down.
– Your brain “flips” the image for you. Kinda.
http://www.diycalculator.com/imgs/cvision-upside-down.gif
Vision Correction
http://www.d.umn.edu/~jfitzake/Lectures/DMED/Vision/Optics/Figures/RefractiveErrors.gif
The Chloroplast
Sketch it like you mean it!
Grana
Chloroplast Structure
(It’s not just an oval)
• Two membranes
– The inside of the inner membrane is called the
stroma.
• Stacks of “disk-like structures.” (Holt: Biology)
– The disks are called thylakoids.
– The stacks are called grana (singular: granum).
– Contain chlorophyll (pigment).
• Light hits chlorophyll and chlorophyll reacts!
RapidTrivia!
• It’s time for something new I’m going to try.
• Grab your whiteboards, grab your markers, and get
your partner’s attention.
• I’m going to post a series of trivia questions about
today’s topics or recent ones, including an off-topic
bonus question.
• Write down your answers QUICKLY!
– Got the right answer? Fantastic, give yourself a star.
– Got the wrong answer? Write down the topic of the
question and review it later.
• Unless it’s the off-topic bonus question.
Question #1
• What is the name of the innermost “space” of
the chloroplast?
– Stroma
Question #2
• What is the name of the disk-like structures
inside the chloroplasts? (just the disks, not
the stacks!)
– Thylakoids
Question #3
• What are the two products of the
photosynthesis reactions?
– Sugar (glucose) and oxygen
Question 4*
• Why did bald eagles become so endangered in
the mid-20th century?
– DDT (dichlorodiphenyltrichloroethane)
*Off-topic
“Illuminating Photosynthesis”
• Before we get to pigments and the “nuts and bolts”
of this whole process, we’re going to see a really
nice animation of the whole process in general.
• Please take the time to read through it carefully –
this will help!
• It’s available here:
– http://www.pbs.org/wgbh/nova/methuselah/phot_flash.html
Photosynthesis: Pigments
• There are three main pigments:
– Chlorophyll A
– Chlorophyll B
– Carotenoids
– There are also Anthocyanins – they help make
leaves change color in the fall.
• “Hard to place” fact:
– Chlorophyll reflects green light!
Carotenoids: A Brief Aside
• In plants:
– Carrots
– Oranges
– Fall leaves
• In animals:
– Flamingos
– Zebra Finches
– Et cetera
http://www.rbgsyd.nsw.gov.au/__data/assets/image/0011/88535/Taeniopygia_guttata_Zebra_Finch_620.JPG
I know you
think my
beak is
attractive.
Back on topic…
http://www.pearsonsuccessnet.com/snpapp/iText/products/0-13-115075-8/text/chapter8/08images/08-02.gif
Chloroplasts
http://www.school.net.th/library/create-web/10000/science/10000-6528/pic2.jpeg
Chloroplasts
http://www.vialattea.net/spaw/image/biologia/May2005/thylakoids2.jpg
Let’s summarize…
Let’s summarize…
Photosynthesis Lab Gizmo!
• Today we’re going to look at a photosynthesis
gizmo. Also please complete the
Photosynthesis Lab Gizmo quiz on Quia.
• [Log-in Instructions]
Photosynthesis Reactions
• There are two overall parts of Photosynthesis:
– The Light Reactions (or Light-Dependent Reactions)
• [because the plant needs light for them]
– The Calvin Cycle (or Light-Independent Reactions)
• Also called “The Dark Reactions”
• [because the plant doesn’t need light for them]
Light Reactions
•
•
•
•
Where: The thylakoid membrane.
Needs: Light and Water (H2O)
Makes: ATP and protons (H+)
Waste: Oxygen
– Note: Even though oxygen is waste, it’s still a
product.
Photosynthesis Reactions
6CO2 + 6H2O  C6H12O6 + 6O2
Light Reactions
Light Reactions
Light Reactions
• Three Steps:
– Light excites chlorophyll’s electrons (makes them
go to higher energy).
– Electrons travel down the thylakoid membrane as
they lose energy. (leave some space in your notes)
– The electrons power the thylakoid to make ADP
into ATP. (leave some space in your notes)
• This thing is called the electron transport chain, by the
way, and it’s much like electricity flowing through a
strand of holiday lights.
e-
Electron Transport Chain
STROMA SPACE
H+
e-
THYLAKOID SPACE
http://bioweb.wku.edu/courses/Biol120/images/non-cyclic1.jpg
ETC
• And what do those electrons power?
– Electrons power a proton pump which brings protons
into the thylakoid space.
• And then…
– Protons passively diffuse out through a
protein/enzyme complex called ATP Synthase.
• ATP Synthase “harvests” the motion of diffusion
to synthesize ATP from ADP and free phosphate
groups.
– Much like a hydroelectric dam harvests water flow.
The Calvin Cycle/Dark Reactions
• Where: The Stroma
• Needs: ATP and protons (H+) [from the Light
Reactions] and CO2 [from the air]
• Makes: Glucose (sugar/carbohydrate)
• Side note: named after Melvin Calvin.
Photosynthesis Reactions
6CO2 + 6H2O  C6H12O6 + 6O2
Light Reactions
Calvin Cycle
Light Reactions
Calvin Cycle
Summary
• The light reactions use sunlight to make ATP
(and some by-products).
• The dark reactions use that ATP to make
glucose.
Closure
• First, let’s do a WhipAround, shall we?
• Write down one new vocabulary word from
today or yesterday and its definition.
– Stand up once you’re done.
• Now the Water Weed Lab.
Closure
• TED: Amanda Ooten – The Simple Story of
Photosynthesis and Food