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Photosynthesis PS Learning Targets 1-8.

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1 Photosynthesis PS Learning Targets 1-8

2 Photosynthesis Outline
LT’s 1-3: Energy and Old Dead Dudes LT’s 4 & 5: Light and Structures of PS LT’s 6-8: Reactions and Factors of PS

3 ENERGY All living things need energy to live!
LT 1 ENERGY All living things need energy to live! Heterotrophs-get their food by eating other organisms and turning them into energy (Ex: herbivores, carnivore, decomposers, etc) Autotrophs-get their energy by converting light or chemical energy into sugar, and then converting that into energy (Ex: plants, bacteria, and some protists)

4 ENERGY The cell will store energy in molecules like sugars and ATP
Most cells have small stores of ATP that only last a few seconds, but cannot store energy there long-term. Cells will store it long term in carbohydrates/ sugars Sugar energy > ATP energy 90x greater

5 ENERGY What are the uses for ATP in biochemical reactions?
Active Transport Energy to move cell organelles Making proteins or nucleic acids PHOTOSYNTHESIS!!!

6 Understanding Photosynthesis
LT 2 Understanding Photosynthesis Van Helmont **Water and CO2 are needed to make plants grow** Do plants grow by taking material out of the soil? Thought most of it came from the water absorbed Did not know that the bulk of the mass came from CO2 absorbed from the air. Priestley **O2 is made from PS ** Put a flame under a jar and watched it burn out. Found there was something in the air that caused the flame to burn Put a mint plant in the jar and found it produced something flames needed. Ingenhousz **Plants need light for PS** Found that Priestley’s experiment needed light to occur.

7 Photosynthesis Reaction
LT 3 Photosynthesis Reaction 6 CO H2O light C6H12O O2 Made in the dark rxn Made in the light rxn From the roots From the sun From the air Will be made into ATP later in Cellular Respiration

8 Light and Pigments Photosynthesis starts with SUNLIGHT!
LT 4 Light and Pigments 6 CO H2O light C6H12O O2 Photosynthesis starts with SUNLIGHT! The light that comes from the sun is WHITE LIGHT or ROYGBIV (R O Y G B I V) The red end is lower energy and longer wavelength The violet end has higher energy and smaller wavelength

9 Light and Pigments ? If plants use visible light, are all colors/wavelengths/energies equally valuable to PS? Let’s see… Read the results of the experiment from Thomas Engelmann in 1803

10 Light and Pigments Most plants are GREEN. This means that
ROY BIV is absorbed and G is reflected. This means that if ROY and BIV are absorbed these are the colors of light that power PS Pigment – any substance that absorbs light Chlorophyll a – the main pigment in plants that absorbs the sun’s light to power PS


12 Light and Pigments There are also other pigments, beside chlorophyll a, called ACCESSORY PIGMENTS chlorophyll b and carotenoids Each pigment has its optimal portion of ROYGBIV for absorption and to fuel PS Chlorophyll a is the main pigment for PS, while the accessory pigments help chlorophyll a by expanding the portion of ROYGBIV it can use!

13 Light and Pigments Chlorophyll a best absorption occurs around 425nm AND 660nm Chlorophyll b best absorption occurs around 475nm AND 640nm Carotenoids best absorption occurs around 450nm AND 490nm Therefore, the accessory pigments expand the absorption from about 425nm (V) to nm (V-B) AND from 660nm (R) to nm (O-R). More light absorbed = More PSing!!

14 Why do leaves change color in the fall?
What are the three kinds of pigments? What two factors cause the color to change? What three factors will give good fall color, especially reds?

15 Why do leaves change color in the fall?
Remember…leaves get their colors from their pigments PIGMENT COLOR WHEN ACTIVE Chlorophyll green Present all year Carotenoids yellow, oranges, and browns Present all year but covered by chlorophyll in summer Anthocyanins red Only produced in autumn under certain conditions

16 Why do leaves change color in the fall?
So how do they know to change color?? Fewer hours of sunlight/days are shorter Trees produce less and less chlorophyll Now carotenoids (already in leaf) can show through Drop in temperature

17 Why do leaves change color in the fall?
But what about the anthocyanins? This is dependent upon… Temperature and cloud cover Warm days and cool nights = good reds Help plants get all the remaining sugar out of the leaves before they fall off So for good fall leaf color… A warm, wet summer A summer that is not too hot or dry A fall with many warm days and cool nights

18 Cell Structures We Already Know….
LT 5 Cell Structures We Already Know…. Cell Membrane A phospholipid bilayer embedded with proteins Selectively permeable Maintains homeostasis for the cell via PASSIVE (diffusion, osmosis, or facilitated diffusion) ACTIVE TRANSPORT (active transport, endocytosis or exocytosis) Now…The Leaf and Chloroplasts The structures plants use for PS

19 The Leaf Cuticle- the waxy outer covering of a leaf that prevents water loss Palisdade Layer-layer of long cells where chloroplasts are found and where most of PS occurs Spongy Mesophyll-random collection of cells with large spaces in between them. Some PS occurs here, but mostly this is where the gases taken in & given off by PS are exchanged between palisade layer and stoma

20 The Leaf (cont.) Guard Cells-the cells on either side of the stoma that open/close them to let gases in or out OR to keep gases in Stoma- openings on the underside of leaves that allow for gas exchange between the leaf and atmosphere.

21 The Chloroplast Let’s see this
Organelle responsible for PHOTOSYNTHESIS! Disc-like in shape Green due to the presence of the pigment Chlorophyll a Found mostly within the palisade layer, but some are in the mesophyll too. Internal structures include Thylakoids StRoma Granum (sing.) or Grana (pl.) Lumen Let’s see this

22 The Chloroplast (cont.)
1 of 2 membranes that surround the organelle Fluid between the thylakoids where the dark rxn occurs Disc where the pigments of PS are. Where the light rxn occurs

23 How Photosynthesis Occurs
LT’s 6 & 7 How Photosynthesis Occurs ? So what about the rest of the PS equation; like CO2, Water, Glucose and O2 ? 6 CO H2O light C6H12O O2 PS occurs in 2 parts Light Dependent (or Light Reaction) This part of the rxn requires LIGHT, H2O, and gives off O2 Light Independent (or Dark Reaction) This part of the rxn requires CO2 and produces the sugar or glucose

24 Photosynthesis Reactants Products

25 The Light Reaction “I’m So Excited!” e- LT 6
electron carriers receive chlorophyll’s electrons the excited e-’s and pass get very excited from the them along to other sun’s energy molecules. These e-’s carriers molecules are called the ELECTRON TRANSPORT CHAIN

26 The Light Reaction NADP+ ATP NADP+ + 2e- + 1H+ NADPH
Examples of a Carrier Molecule: NADP+ Takes 2e-’s from chlorophyll and 1H+ from water NADP e H NADPH Takes energy with it to other cell rxns Think of it like a UPS truck, picking up “packages” and dropping them off ATP

27 The Light Reaction: Key Concepts
Occurs in the thylakoid membrane of the chloroplast Includes Photosystem II and Photosystem I Needs Light and H2O to start Produces O2, NADPH and ATP Waste!

28 The Light Reaction: Photosystem II
PS II - In the Thylakoid Membrane (TM) 1. e- absorb sun’s energy and get highly energized 2. The proteins in the TM split a water (hydrolysis) to make H+’s , e-’s , and O2 3. e-’s go to ETC (a series of protein carriers) 4. Energy from the e-’s pumps H+’s into the TM, changing the [H+] ions (low to high-active transport)

29 The Light Reaction: Photosystem I
PS I - In the Thylakoid Membrane (TM) 5. Light is energized again 6. e-’s move to the final e- acceptor which adds them to NADP+ to make NADPH 7. High [H+] (left over from hydrolysis) diffuse through the enzyme protein ATP synthase to make ATP form ADP (H+ give energy to add a phosphate to ADP) Let’s See This

30 The Light Reaction: The Thylakoid Membrane


32 The Light Reaction: The Thylakoid Membrane
A Little Quiz: Put a #1 where there is a higher concentration of H+ Draw a squiggly line between PSII and PSI Put a #2 on the thylakoid membrane Put a #3 in the stroma Put a #4 where the e-’s are first energized Put a #5 where the e-’s are re-energized Put a #6 where hydrolysis occurs Put a #7 where active transport is occurring.

33 The Dark Reaction: Key Concepts
LT 7 The Dark Reaction: Key Concepts The second part of PS is called the Dark Reaction,the Calvin Cycle, or the Light Independent Cycle It is called the Dark Rxn because this part can take place without light (that is not to say it must be dark, but if it were, this part could still proceed)

34 The Dark Reaction: Key Concepts
The two products from the Light Reaction, NADPH and ATP go to the Dark Reaction NADPH and ATP have lots of energy in their bonds but they can only hold it for a few minutes If the cell wants to hold the energy long-term, they will have to build high energy molecules that can hold it…like GLUCOSE (savings account!) This process takes place in the stRoma (outside of chloroplast)

35 1 exits and will become GLUCOSE
The Dark Reaction From Light Rxn 3-RuBP’s 5 C’s 6-ATP 3 -CO2 3-6C Compound-Unstable! 6-3C PGA’s 6-NADPH 6-3C PGAL’s 3-5C RuBP’s 3-ATP Calvin Cycle Video 1 exits and will become GLUCOSE 5 stay in cycle

36 There are factors that limit the amount of PS
LT 8 Limiting Factors to PS There are factors that limit the amount of PS H2O –slow or decrease PS Temperature Recall that enzymes have particular optimal temperatures Functions best between °C Temperatures above or below these temps slow PS Very low temps STOP PS Light Intensity- increase intensity = increase PS Color of Light – RO and BV preferred

37 Photosynthesis Review
LT’s 1-8 Photosynthesis Review Two rxns: Light and Dark Reactants: H2O, CO2, and Light Products: O2 and Glucose Two Locations: Light –Thylakoid Membrane Dark- StRoma

38 Photosynthesis Review
Word Bank Photosynthesis ATP (2) Thylakoid Stroma Light Energy from the sun High energy sugars NADPH (2) Oxygen Light-depentdent reaction Calvin Cycle Chloroplast 1. 2. 8. 11. 3. 9. 10. 4. 6. 12. 5. 7. 13.

39 Photosynthesis Review

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