Presentation on theme: "Today is Wednesday, October 30 th, 2013 Pre-Class: Why are plants green? (Or why are the green parts of them green, at least?) Other stuff: Turn in your."— Presentation transcript:
Today is Wednesday, October 30 th, 2013 Pre-Class: Why are plants green? (Or why are the green parts of them green, at least?) Other stuff: Turn in your homework if you did it on paper. Grab a [small] paper towel for your pair. In This Lesson: Photosynthesis (Lesson 2 of 3)
Today’s Agenda Photosynthesis And maybe flamingos.
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)
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. (it’s also using CO 2 but he didn’t catch that part) – Jan van Helmont also coined the word “gas.” 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. ‘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 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. I am grayscale.
2013: 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 YE OLDE PHOTOSYNTHESIS MACHINE YE OLDE PHOTOSYNTHESIS MACHINE ? INPUT OUTPUT ?
Photosynthesis: An Outline Photosynthesis is basically this: 6CO 2 + 6H 2 O + [LIGHT] C 6 H 12 O 6 + 6O 2 – 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*.
*Disclaimer Technically, when a color is transmitted to us, only a complementary color is absorbed:
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
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.
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-20 th 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: –
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 I know you think my beak is attractive.
Back on topic…
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 (H 2 O) Makes: ATP and protons (H + ) Waste: Oxygen – Note: Even though oxygen is waste, it’s still a product.
Photosynthesis Reactions 6CO 2 + 6H 2 O C 6 H 12 O 6 + 6O 2 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-e-
Electron Transport Chain e-e- H+H+ STROMA SPACE THYLAKOID SPACE
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 CO 2 [from the air] Makes: Glucose (sugar/carbohydrate) Side note: named after Melvin Calvin.
Photosynthesis Reactions 6CO 2 + 6H 2 O C 6 H 12 O 6 + 6O 2 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 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.
Water Weed Lab This is a written lab report. – Specific requirements and a rubric are listed on the reverse of your lab sheet. You will be taking a virtual look at an aquatic plant (Elodea) and analyzing photosynthetic rate as a function of three particular conditions: – Light Level – Light Color – CO 2 Level You will need to create a graph for your final lab report. – The graph can be created in Excel, by hand, or with an online graphing tool. Create-a-Graph (in Biology Links – Various Units section) TIP: Select “X5” to run the simulator faster.
Closure TED: Amanda Ooten – The Simple Story of Photosynthesis and Food