Cell Energy: Cell Energy: Photosynthesis Photosynthesis

Where Does Energy Come Where Does Energy Come From?From?

Autotrophs:Autotrophs: Use light energy from Use light energy from the sun to produce food necessary the sun to produce food necessary to give them energy.to give them energy.

Heterotrophs:Heterotrophs: Can’t use the energy Can’t use the energy of the sun, these organisms need to of the sun, these organisms need to obtain energy from foods they obtain energy from foods they consume.consume.

EnergyEnergy

Energy comes in many forms: Energy comes in many forms: Light, Light, Heat, Electricity.Heat, Electricity.

One source of chemical energy that One source of chemical energy that living things use isliving things use is adenosine adenosine triphosphate (ATP).triphosphate (ATP).

ATP: Adenosine ATP: Adenosine TriphosphateTriphosphate Consists of:Consists of:

AdenosineAdenosine A 5-Carbon sugar called RiboseA 5-Carbon sugar called Ribose 3 Phosphate groups (the key to its ability to store 3 Phosphate groups (the key to its ability to store

and release energy).and release energy). Energy Energy storagestorage and and releaserelease

Cells have the ability to store energy in small Cells have the ability to store energy in small amounts (3-5 seconds)amounts (3-5 seconds)

ADPADP (energy source like ATP but with one less (energy source like ATP but with one less phosphate group) must add a phosphate group so phosphate group) must add a phosphate group so the cell can the cell can storestore energyenergy,,

Energy will be releasedEnergy will be released from that ATP when that from that ATP when that same phosphate group is removed.same phosphate group is removed.

ATP powers many reactions this way (ATP powers many reactions this way (active active transport, protein synthesis, muscle contractiontransport, protein synthesis, muscle contraction))

PhotosynthesisPhotosynthesis

The process which plants use to The process which plants use to convert the energy of sunlight into convert the energy of sunlight into carbohydratescarbohydrates ( (sugars and starchessugars and starches) ) they can use as an energy source.they can use as an energy source.

Scientist of Scientist of PhotosynthesisPhotosynthesis Van Helmont-Van Helmont- Experimented to see if Experimented to see if

plants grew by taking materials out of plants grew by taking materials out of soil.soil. He concluded that water was responsible for He concluded that water was responsible for

the majority of plant growth.the majority of plant growth. He had it ½ right, he didn’t realized that the He had it ½ right, he didn’t realized that the

carbon dioxide in the air was used with the carbon dioxide in the air was used with the water and sunlight to produce energy.water and sunlight to produce energy.

Scientist of Scientist of PhotosynthesisPhotosynthesis

PriestlyPriestly- Experimenting with a fig plant - Experimenting with a fig plant and a candle under a jar, discovers that and a candle under a jar, discovers that plants release a chemical (we now know plants release a chemical (we now know is Oxygen) that allows the candle to burn.is Oxygen) that allows the candle to burn.

IngenhouszIngenhousz--Discovers that plants Discovers that plants produce oxygen when in light but, not in produce oxygen when in light but, not in the dark.the dark.

PhotosynthesisPhotosynthesis

The photosynthesis reaction:The photosynthesis reaction: 6CO6CO22+H+H22O --> CO --> C66HH1212OO66+6O+6O22 (With (With lightlight

present).present). The photosynthesis reaction requires: The photosynthesis reaction requires: LightLight, ,

WaterWater, and , and Carbon DioxideCarbon Dioxide.. The light used for photosynthesis to occur, is The light used for photosynthesis to occur, is

captured by a green pigment (captured by a green pigment (chlorophyllchlorophyll) ) stored in the stored in the chloroplastchloroplast..

Plants also contain other pigments (Plants also contain other pigments (redred, , orange, orange, yellowyellow, , etc.) that absorb light from another part of the etc.) that absorb light from another part of the spectrum that chlorophyll does not absorb.spectrum that chlorophyll does not absorb.

PhotosynthesisPhotosynthesis

Inside the Inside the ChloroplastChloroplast:: Chloroplast Envelope-Chloroplast Envelope- Made of an inside and Made of an inside and

outside membrane surrounds the outside membrane surrounds the chloroplastchloroplast.. ThylakoidsThylakoids- Saclike photosynthetic membrane - Saclike photosynthetic membrane

(location of (location of Light ReactionLight Reaction).). GranumGranum-- Stack of Stack of thylakoidsthylakoids PhotosystemsPhotosystems- Proteins in the - Proteins in the thylakoidsthylakoids organize organize

chlorophyll and other pigments into clusters known chlorophyll and other pigments into clusters known as as photosystemsphotosystems, this is the light collecting unit of , this is the light collecting unit of the chloroplast.the chloroplast.

Stroma-Stroma- Space outside of the Space outside of the thylakoids (thylakoids (location oflocation of Dark ReactionDark Reaction))..

PhotosynthesisPhotosynthesis

Light ReactionLight Reaction:: The The first stepfirst step of photosynthesis. of photosynthesis. Requires Requires LightLight.. Takes place in the Takes place in the ThylakoidsThylakoids.. Uses sunlight to produce Uses sunlight to produce OxygenOxygen and and

convert convert ADP & NADPADP & NADP into into ATPATP and and NADPHNADPH..

Requires Requires waterwater (H (H22O).O).

PhotosynthesisPhotosynthesis The steps of a The steps of a Light ReactionLight Reaction

1.1. Pigments begin to absorb light, which is used to break Pigments begin to absorb light, which is used to break up water molecules into up water molecules into HH++ and and OO (which is released (which is released into the air).into the air).

2.2. Energy from electrons in the electron transport chain is Energy from electrons in the electron transport chain is used to transport Hused to transport H++ from the from the stromastroma into the into the thylakoidthylakoid..

3.3. Energy from light is used to reenergize electron. Energy from light is used to reenergize electron. NADPNADP picks up these electron along with picks up these electron along with HH++ at the outer at the outer surface of the surface of the thylakoidthylakoid to become to become NADPHNADPH..

4.4. As electrons pass from chlorophyll to As electrons pass from chlorophyll to NADPNADP, more , more HH++ ions are passed across the membrane, after a while ions are passed across the membrane, after a while the inside becomes (+) and the outside becomes (-) the inside becomes (+) and the outside becomes (-) this difference in charge provides the energy this difference in charge provides the energy necessary to make necessary to make ATPATP..

5.5. HH++ use a protein called use a protein called ATP synthaseATP synthase to help it pass to help it pass through the membrane, as Hthrough the membrane, as H++ passes the membrane it passes the membrane it rotates the protein, As it is rotating it binds rotates the protein, As it is rotating it binds ADPADP and a and a phosphate groupphosphate group together producing together producing ATPATP..

PhotosynthesisPhotosynthesis

Dark Reaction:Dark Reaction: Also known as the Also known as the Calvin Cycle, Calvin Cycle, it is theit is the

second step second step in photosynthesis.in photosynthesis. Takes place in the Stroma.Takes place in the Stroma. Uses the energy from the Uses the energy from the ATPATP and and NADPH NADPH

produced by the light reaction to make produced by the light reaction to make high high energy sugars.energy sugars.

Doesn’t require Doesn’t require lightlight.. Requires Requires COCO22..

PhotosynthesisPhotosynthesis The steps of a The steps of a Dark ReactionDark Reaction::

1.1. 6 carbon dioxide6 carbon dioxide molecules enter the reaction in molecules enter the reaction in the stroma, they combine with the stroma, they combine with 66 ( (5 carbon5 carbon) ) molecules to make molecules to make 1212 ( (3 carbon3 carbon) molecules.) molecules.

2.2. Energy from Energy from ATPATP and and high-energy electronshigh-energy electrons from from NADPHNADPH are used to convert the are used to convert the 1212 ( (3 carbon3 carbon ) ) molecules into high-energy forms.molecules into high-energy forms.

3.3. 22 of the of the 1212 ( (3 carbon3 carbon ) molecules are removed ) molecules are removed from the cycle, the plant cell uses these molecules from the cycle, the plant cell uses these molecules to produce; to produce; sugars, lipids, amino acidssugars, lipids, amino acids, and , and other molecules needed for other molecules needed for plant metabolismplant metabolism and and growthgrowth..

4.4. The remaining The remaining 1010 ( (3 carbon3 carbon) molecules are ) molecules are converted back to converted back to 6 6 ((5 carbon5 carbon) molecules like the ) molecules like the cycle started with, they will be used to start the cycle started with, they will be used to start the cycle over again.cycle over again.

PhotosynthesisPhotosynthesis