1. Making life on earth possible!
Photosynthesis
Making life on earth possible!
©2013 Erin Mucci

2. Energy and Living Things
You get energy from the food you eat
Almost all of the energy in living systems comes from the sun
Metabolism involves either
using energy to build molecules or
breaking down molecules in which energy is stored
©2013 Erin Mucci

3. Light energy  Chemical energy
Photosynthesis
Light energy  Chemical energy
Autotrophs – organisms that use energy from sunlight or from chemical bonds in inorganic substances to make organic compounds
Heterotrophs – organisms that must get energy from food instead of directly from sunlight
©2013 Erin Mucci

4. Can you trace the energy from a ham and cheese sandwich back to the sun?
Ham > Pig > Grains > Sun
Cheese > Milk > Cow > Grass > Sun
Bread > Wheat > Sun
What did you eat today? Create the food chain that leads back to the sun for each item you have eaten today.
©2013 Erin Mucci

5. Without organisms that make sugars, living things on Earth could not survive!
You may feel tired, like you need energy…..does food give you energy?
Yes and No
Food contains organic compounds (like carbohydrates, lipids, and protein) that store chemical energy in their bonds
Digestion breaks food down into smaller
molecules that could possibly be put back
together to make ATP!
©2013 Erin Mucci

6. ATP (Adenosine Triphosphate)
Carries the energy that cells can use in its chemical bonds H2O + ATP  ADP + P + energy Cells use the energy from this reaction to power metabolism
Adenine P
Ribose
Energy
©2013 Erin Mucci

7. What if there is no sunlight?
Deep in the ocean? Underground?
Chemosynthesis – organisms use chemical energy (chemo) instead of light energy (photo) to make energy-storing carbon-based molecules
A submarine volcano!
©2013 Erin Mucci

8. Producers All photosynthetic organisms are producers
They make their own chemical energy
Plants
Algae
Bacteria
©2013 Erin Mucci

9. What is Photosynthesis?
A process where plants absorb visible light from the sun and convert it into sugars that store chemical energy
Visible light – a region of the electromagnetic spectrum made up of several colors at different wavelengths
©2013 Erin Mucci

10. So, why are plants usually green?
Chlorophyll
Pigments – light absorbing substances
Chlorophyll – primary pigment involved in photosynthesis
Absorbs blue and red wavelengths
Reflects green and yellow wavelengths
So, why are plants usually green?
Chlorophyll is found in Chloroplasts (organelles that are only found in plants)
©2013 Erin Mucci

11. Chloroplasts Pigments are located in the chloroplasts of the plant
Thylakoids inside the chloroplasts are disc-shaped structures that hold the pigments which absorb the light energy
Thylakoid
©2013 Erin Mucci

12. Photosynthesis - The Equation
Why do plants need photosynthesis?
The sugars that are produced during photosynthesis allow the plant to build more cells and grow!
©2013 Erin Mucci

13. There are 2 Stages of Photosynthesis
Light-dependent reactions (photo-)
Energy is captured and transferred to electrons
Light-independent reactions (-synthesis)
Energy in the form of ATP and NADPH is used to create sugars
©2013 Erin Mucci

14. The Light-dependent reactions
Photosystem II and Electron Transport Chain
Energy is absorbed from sunlight by chlorophyll and other light-absorbing molecules in the thylakoid membrane
The energy is transferred to electrons (e-)
The energized electrons enter the Electron Transport Chain (which is a series of proteins in the thylakoid membrane)
Water is broken down by enzymes into oxygen gas (O2) and hydrogen ions (H+)
Electrons move from protein to protein in the electron transport chain. Their energy is used to pump H+ from outside to inside the thylakoid membrane.
H+ builds up inside the thylakoid, electrons move on to Photosystem I
©2013 Erin Mucci

15. The Light-dependent reactions
Photosystem I and Energy-Carrying Molecules
Energy is absorbed from sunlight by chlorophyll and other light-absorbing molecules in the thylakoid membrane
The energy is transferred to electrons (e-)
The energized electrons enter combine with NADP+, forming NADPH
NADPH functions like ATP, they are both energy-carrying molecules
NADPH moves on to the light-independent reactions
©2013 Erin Mucci

16. The Light-dependent reactions
Production of ATP
Hydrogen ions (H+) diffuse through the thylakoid membrane with the concentration gradient
While H+ is flowing through the protein channel, ATP Synthase enzyme adds phosphates to ADP to make ATP
ADP + P  ATP
Adenosine Diphosphate
Adenosine Triphosphate
Energy
©2013 Erin Mucci

17. The Light-independent reactions
Take place in chloroplasts
Do not need sunlight
ATP and NADPH from the light-dependent reactions are used to fuel a series of reactions called the Calvin Cycle
Carbon Dioxide gas (CO2) from the atmosphere and ATP and NADPH molecules from the light-dependent reactions are used to create simple sugars
©2013 Erin Mucci

18. The Calvin Cycle
CO2 molecules are added to five-carbon molecules to form six-carbon molecules
Energy (ATP and NADPH) is used by enzymes to split the six-carbon molecules into 2 three-carbon molecules
One of the three-carbon molecules exits the cycle
It will meet up with another three-carbon molecule to form a six-carbon molecule of glucose sugar
ATP is used to change the remaining three-carbon molecules back into five-carbon molecules.
©2013 Erin Mucci

19. The Calvin Cycle CCCCC CCCCCC CCC CCC CCC CCCCCC CCC CO2 O2 ATP
ATP & NADPH
CCC
CCC
Glucose sugar!
CCCCCC
CCC
©2013 Erin Mucci

20. Image Credits Slide 3: Field & Molecule - Microsoft Clipart Gallery
Slide 7: Submarine Volcano – NOAA
Slide 8: Plants & Bacteria – Microsoft Clipart Gallery, Algae: © Copyright Stephen Craven and licensed for reuse under this Creative Commons License
Slide 9: Electromagnetic Spectrum - Public Domain
Slide 11: Chloroplast – Public Domain
Slide 14-19: Sunburst - Microsoft Clipart Gallery
©2013 Erin Mucci