Lesson OverviewLesson Overview Photosynthesis: An OverviewPhotosynthesis: An Overview
Lesson OverviewLesson Overview8.2 8.2 Photosynthesis:
An Overview
Lesson OverviewLesson Overview Photosynthesis: An OverviewPhotosynthesis: An Overview
Light
Energy from the sun travels to Earth in the form of light.
Sunlight is a mixture of different wavelengths, many of which are visible to our eyes and make up the visible spectrum.
Lesson OverviewLesson Overview Photosynthesis: An OverviewPhotosynthesis: An Overview
Pigments
Plants gather the sun’s energy with light-absorbing molecules called pigments.
The plants’ principal pigment is chlorophyll.
Lesson OverviewLesson Overview Photosynthesis: An OverviewPhotosynthesis: An Overview
Pigments
Lesson OverviewLesson Overview Photosynthesis: An OverviewPhotosynthesis: An Overview
ChloroplastsChloroplasts contain saclike photosynthetic membranes called thylakoids, which are interconnected and arranged in stacks known as grana.
The fluid portion outside of the thylakoids is known as the stroma.
Lesson OverviewLesson Overview Photosynthesis: An OverviewPhotosynthesis: An Overview
Energy Collection
When chlorophyll absorbs light, a large fraction of the light energy is transferred to electrons. These high-energy electrons make photosynthesis work.
Lesson OverviewLesson Overview Photosynthesis: An OverviewPhotosynthesis: An Overview
High-Energy ElectronsThe high-energy electrons produced by chlorophyll are highly reactive and
require a special “carrier.”
Think of a high-energy electron as being similar to a hot potato. If you wanted to move the potato from one place to another, you would use an oven mitt —a carrier—to transport it.
Plants use electron carriers to transport high-energy electrons from chlorophyll to other molecules.
Lesson OverviewLesson Overview Photosynthesis: An OverviewPhotosynthesis: An Overview
High-Energy ElectronsNADP+ (nicotinamide adenine dinucleotide phosphate) is a carrier molecule.
NADP+ accepts and holds two high-energy electrons, along with a hydrogen ion (H+). In this way, it is converted into NADPH.
The NADPH can then carry the high-energy electrons to chemical reactions elsewhere in the cell.
Lesson OverviewLesson Overview Photosynthesis: An OverviewPhotosynthesis: An Overview
An Overview of PhotosynthesisPhotosynthesis uses the energy of sunlight to convert water and carbon dioxide into high-energy sugars and oxygen.
In symbols:
6 CO2 + 6 H2O C6H12O6 + 6 O2
In words:
Carbon dioxide + Water Sugars + Oxygen
Lesson OverviewLesson Overview Photosynthesis: An OverviewPhotosynthesis: An Overview
An Overview of Photosynthesis
Plants use the sugars generated by photosynthesis to produce complex carbohydrates such as starches, and to provide energy for the synthesis of other compounds, including proteins and lipids.
Lesson OverviewLesson Overview Photosynthesis: An OverviewPhotosynthesis: An Overview
Light-Dependent Reactions
Photosynthesis involves two sets of reactions.
The first set of reactions is known as the light-dependent reactions because they require the direct involvement of light and light-absorbing pigments.
Lesson OverviewLesson Overview Photosynthesis: An OverviewPhotosynthesis: An Overview
Light-Dependent ReactionsThe light-dependent reactions use energy from sunlight to produce ATP and NADPH.
These reactions take place within the thylakoid membranes of the chloroplast.
Water is required as a source of electrons and hydrogen ions. Oxygen is released as a byproduct.
Lesson OverviewLesson Overview Photosynthesis: An OverviewPhotosynthesis: An Overview
Light-Independent ReactionsDuring light-independent reactions, ATP and NADPH molecules produced in the light-dependent reactions are used to produce high-energy sugars from carbon dioxide.
No light is required to power the light-independent reactions.
The light-independent reactions take place outside the thylakoids, in the stroma.
Lesson OverviewLesson Overview Photosynthesis: An OverviewPhotosynthesis: An Overview
Lesson OverviewLesson Overview Photosynthesis: An OverviewPhotosynthesis: An OverviewQuestions1. In the process of photosynthesis, plants convert the energy of sunlight into
chemical energy stored in the bonds of _________. Carbohydrates
2. Photosynthetic organisms capture energy from sunlight with ________. Pigment
3. The plant’s principal pigment is _______. Chlorophyll
4. Photosynthesis takes place in ___________. Chloroplasts
5. T or F - Chloroplasts contain an abundance of saclike photosynthetic membranes called thylakoids. TRUE
6. T or F - The fluid portion of the chloroplast, outside of the thylakoids, is known as the matirx. FALSE - STROMA
7. Raising the energy levels of electrons on the chlorophyll molecule, light energy can produce a steady supply of _______________electrons, which is what makes photosynthesis work. High Energy
Lesson OverviewLesson Overview Photosynthesis: An OverviewPhotosynthesis: An Overview
Questions8. An electron _________is a compound that can accept a pair of high-energy
electrons and transfer them, along with most of their energy, to another molecule.Carrier
9. NADP+ is converted to ______________as it accepts and transfers electrons to chemical reactions elsewhere in the cell.NADPH
10. What is the overall equation of photosynthesis?6CO2 + 6H2O + light C6H12O6 + 6O2
11. The light- ______________reactions produce ATP and NADPH from sunlight in the thylakoid membranes.Dependent
12. The light-______________t reaction in the stroma, sugars are created from carbon dioxide using the ATP and NAPH from the light-dependent reactions.Independent
Lesson OverviewLesson Overview Photosynthesis: An OverviewPhotosynthesis: An Overview
Photosynthesis REVIEW
Lesson OverviewLesson Overview Photosynthesis: An OverviewPhotosynthesis: An Overview
Photosynthesis REVIEW
Lesson OverviewLesson Overview Photosynthesis: An OverviewPhotosynthesis: An Overview
Photosynthesis REVIEW
Lesson OverviewLesson Overview Photosynthesis: An OverviewPhotosynthesis: An Overview
What is the equation for photosynthesis?