Today is Thursday,
October 29
th, 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. In This Lesson:
Photosynthesis (Lesson 2 of 3)
Today’s Agenda
• Photosynthesis
• Photosynthesis
• And maybe flamingos.
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.
Simple Diagram
(worth sketching…no, really)
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
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 jar over it.
– 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
‘allo guv’nah!!
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
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.
The Magic Photosynthesis Machine
YE OLDE
PHOTOSYNTHESIS
MACHINE
?
INPUT 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
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
Ishihara Test
Ishihara Test
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.
Vision Correction
The Chloroplast
Sketch it like you mean it!
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).
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.
Question #1
• What is the name of the innermost “space” of the chloroplast?
Question #2
• What is the name of the disk-like structures inside the chloroplasts? (just the disks, not the stacks!)
Question #3
• What are the two products of the photosynthesis reactions?
Question 4*
• Why did bald eagles become so endangered in the mid-20th century?
– DDT (dichlorodiphenyltrichloroethane)
“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:
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:
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…
Chloroplasts
Chloroplasts
Photosynthesis Lab Gizmo!
• Today we’re going to look at a photosynthesis gizmo. Also please complete the
Photosynthesis Lab Gizmo quiz on Quia.
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”
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
6CO
2+ 6H
2O
C
6H
12O
6+ 6O
2 Ligh t R eac tions Ligh t R eactio nsLight 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.
-Electron Transport Chain
http://bioweb.wku.edu/courses/Biol120/images/non-cyclic1.jpg e -H+ STROMA SPACE THYLAKOID SPACEETC
• 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.
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)
Photosynthesis Reactions
6CO
2+ 6H
2O
C
6H
12O
6+ 6O
2 Ligh t R eac tions Ligh t R eactio ns Calv in Cy cle Calv in Cy cleSummary
• 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