CHAPTER 8 PHOTOSYNTHESIS

CHAPTER 8 PHOTOSYNTHESISSECTION 8-1ENERGY and LIFEAUTOTROPHS AND HETEROTROPHSWhat is the key source of energy for most things?THE SUNPlants and other organisms such as blue-green algae use light energy from the sun to produce food.These organisms are called AUTOTROPHS.Use simple inorganic molecules to do this.

AUTOTROPHS and HETEROTROPHSHeterotrophs are organisms that obtain energy from the food they consume.Unable to use sunlight directly.

ALL organisms must release energy in sugars and other compounds.

CHEMICAL ENERGY and ATPWhat are three forms of energy?Light, heat, and electricity

Energy can be stored in compounds.

Electrons release energy when a piece of wood is set on fire.

When chemical bonds are broken and electrons shift from higher energy levels to lower energy levels, the extra energy is released as light and heat.

CHEMICAL ENERGY and ATPHow do organisms such as humans store and release energy?Chemical compounds are used to do this.

What is ATP?Adenosine Triphosphate (ENERGY storing molecule)

ATP consists of ADENOSINE, a 5-CARBON SUGAR, and 3 PHOSPHATE GROUPS

What is ATP?https://www.youtube.com/watch?v=bbtqF9q_pFwRELEASING ENERGYHow is stored energy released from ATP to be used by the cell?Energy stored in chemical bond between the second and third phosphate groups.

Breaking this bond releases the energy stored in it.

STORING ENERGYWhat is ADP?ADENOSINE DIPHOSPHATE2 PHOSPHATE GROUPSPartially charged battery

Key molecule used to store excess energy.

To store energy

P + ADP ATP

ATP is like a fully charged battery. WHY?RELEASING ENERGYATP is the basic energy source for all cells.

What are different cellular functions that ATP can power within the cell?

ACTIVE TRANSPORT

PROTEIN SYNTHESIS

MUSCLE CONTRACTION

USING BIOCHEMICAL ENERGYWhat is a SODIUM POTASSIUM Pump?Used during Active TransportPumps Na- ions out of the cell and K+ ions inAssists in transport of glucose into cellMaintains muscle movement and controlControls cell volume

Why do most cells only have a small amount of ATP?Not a good molecule for storing large amounts of energy over a long period of time.Cells regenerate ATP

How do cells store energy for long periods of time?Glucose stores 90 times more energy than ATP

8-2 Photosynthesis: An OverviewWhat is PHOTOSYNTHESIS?

Plants use the energy of sunlight to convert water and carbon dioxide into high energy carbohydrates Sugars and starches

And Oxygen, a waste product.

Investigating PhotosynthesisAs a tree grows bigger and bigger in size, where does the trees increase in mass come from?

SOIL, WATER, AIR?

This simple question asked hundreds of years ago began the research into photosynthesis.

Lets take a closer look at some of the experiments that led to the discovery of photosynthesis

Van HELMONTS Experiment1643, Belgian physician Jan van Helmont.

What did he do?Experiment to investigate if plants grew by taking materials out of the soil.

His experiment?1. Determined mass of a pot of dry soil and a seedling.

Van HELMONT Experiment2. Planted the seedling in the pot of soil.Watered regularly.3. At the end of 5 years, the seedling had grown into a small tree. Mass gain of 75 grams.4. Mass of soil remained almost unchanged.

His ConclusionMass of the tree came from the water only thing he added.Accounted for the HYDRATE portion of a CARBOHYDRATE

Where does the CARBO portion come from?Carbon DioxidePriestleys Experiment1771, English minister Joseph Priestley

What did he do?Lit a candle, placed a jar over it, and watched the flame gradually die out.

What did he reason about the candle flame?Something in the air was necessary to keep the candle burning. Priestleys ExperimentWhat was his next step?He placed a spring of mint underneath the jar with the candle.

After a few days, candle could be relit.Burned for a longer period of time.

His conclusion?The mint sprig released something needed to keep the candle flame burning.What was this mystery substance?OXYGEN

The Ingenhousz Experiment1779, Dutch scientist Jan Ingenhousz

What did he do?Showed the effect observed by Priestley only occurred when plant exposed to light.

What did these experiments show?When a plant is exposed to light, it transforms carbon dioxide and water into carbohydrates and releases oxygen.

PHOTOSYNTHESIS EQUATIONWhat is the balanced equation of photosynthesis?

Compare the equation of photosynthesis with another cellular process.

Light and PigmentsWhite light - mixture of different wavelengths of light visible spectrumDifferent wavelengths = different colors.

Light and PigmentsWhat are colored substances that absorb or reflect light?PIGMENTS

Why are plants green?chlorophyll: principle pigment in green plantsAbsorbs red and blue-violet light

Chlorophyll a and Chlorophyll bReflect green light which is why plants look green.

Absorption of LightB caroteneRed and orange pigments that absorb light in other regions of the spectrum.

SECTION 8-3: The ReactionsWhere do they occur?The ChloroplastContains ThylakoidsPhotosyntheticmembranes.Arranged in stacks called GRANA (GRANUM)

Photosystems: chlorophyll and pigments in the thylakoidLIGHT-Collecting Units of the Chloroplast

8-3: Reactions of Photosynthesis1. Light-Dependent ReactionsIn the thylakoid membranes

2. Light-Independent Reactions or The Calvin CycleTake place in the stroma

NADP+AN ELECTRON CARRIERCarries 2 High-energy electrons (e-) and a hydrogen ion (H+).

Converts NADP+ into NADPH

Sunlight energy is trapped in chemical form.

NADPH carries HE e- produced in chlorophyll to chemical reactions in the cell.LIGHT DEPENDENT REACTIONSPRODUCE Oxygen gasCONVERT ADP and NADP+ into energy carriers ATP and NADPH

STEP A: Pigments in Photosystem II absorb light.

Electrons absorb light energy making them HIGH-Energy electrons

HIGH-Energy electrons passed to Electron Transport Chain (ETC)

LIGHT DEPENDENT REACTIONSSTEP A CONTINUED:Does chlorophyll run out of electrons?No

Where do the new electrons come from?WATER is broken down by enzymes.1 WATER molecule 2 H+ ions and 1 O atom2 H+ ions replace the HE electrons passed to the ETCOxygen is released into the atmosphere

LIGHT DEPENDENT REACTIONSSTEP B: HE e- move through ETC from Photosystem II to Photosystem IEnergy used in ETC to transport H+ ions from Stroma to Thylakoid.

STEP C: Pigments in Photosystem I use light energy to recharge electrons.NADP+ picks up HE e- and H+ ionsNADP+ becomes NADPHLIGHT DEPENDENT REACTIONSSTEP D: H+ ions are pumped across the thylakoid membrane.Inside of membrane fills up with H+ ionsOutside of membrane becomes negatively charged.

This difference in charges provides the energy to make ATP.

What is the importance of H+ ions?LIGHT DEPENDENT REACTIONSSTEP E: ENERGY MAKING STEPATP SYNTHASE found in cell membrane.

Allows H+ ions to pass through.

ATP Synthase rotates and binds ADP with a Phosphate making ATP.

LDR ETC produces HIGH-Energy electrons and ATPATP SYNTHASE

Photosynthesis Reactions

REVIEW of LDR What happens in LDR?LDR traps sunlight energy in a chemical form (A).HE e- give energy to ETC to move H+ ions into the thylakoid (B).PHOTOSYSTEM I recharges e- and are picked up by NADP+ with H+ ions making NADPH (C).H+ ions are pumped across the thylakoid membrane into the cell (D).H+ ions diffuse back through the membrane using ATP Synthase (E).Provides energy for ADP + P ATP (FREE ENERGY)

The Calvin Cycle (Light-Independent Reactions)Discovered by Melvin Calvin in 1948.

Involves an enzyme called RUBISCO

The Calvin Cycle uses ATP and NADPH from LDR to produce high energy sugars.The Calvin CycleSTEP A: CO2 Enters the Cycle12 (3-C molecules) made

STEP B: Energy Input3-C molecules are converted into higher-energy forms.Uses ATP and HE electrons

12 ATP and 12 NADPH are usedReturns 12 ADP and 12 NADP+

The Calvin CycleSTEP C: 6-Carbon Sugar Produced3-C molecules produce SUGARS, lipids, amino acids, and other compounds.

STEP D: 5-Carbon Molecules Regenerated5-C molecules are returned to beginning of cycle6 ATP are used here.

The Calvin Cycle6 CO2 are used to create a single 6-C SUGAR molecule

Plants use the SUGARS to meet energy needs and build more macromolecules such as Cellulose.

LDR traps sunlight energy in a chemical formATP and NADHP

CC uses this chemical energy to produce stable, high energy SUGARS from CO2 and H2O.

REVIEW of CALVIN CYCLECO2 combines with 5-C molecules to make 3-C molecules (A)3-C molecules converted into higher energy forms using ATP and NADPH (B)Two 3-C molecules removed from CC to make Glucose and other molecules (C)Ten 3-C molecules are converted back to Six 5-C molecules (D).Cycle repeats itself.

Bozeman Science Videohttp://www.youtube.com/watch?v=g78utcLQrJ4

Start 2:13Stop 8:35LDR and CCWhy are they called LIGHT DEPENDENT REACTIONS?They require light energy to take place.

Lets look at the bigger picture.What would happen if plants do not get sunlight?Plants could not perform photosynthesis.They would not produce sugars or release Oxygen GasOrganisms like you and me(heterotrophs) would not be able to survive.

Why is the Calvin Cycle called Light Independent Reactions?When does the CC take place?The CALVIN CYCLE

THE CALVIN CYCLE1. Where does the Calvin Cycle take place?

2. What enters the CC from the atmosphere?

3. Where do ATP and NADPH come from?

4. What is the product of the CC?

5. How is the cycle completed? (Why is the CC called a cycle?)Factors that Affect PhotosynthesisWaterProvides electrons to the LDRHow do plants in dry areas protect themselves from water loss?

Temperature ENZYMES function best between 0 and 35 degrees CWhat effect will extreme temperatures have on enzymes?

Intensity of LightMore Light = More Photosynthesis

Why do leaves change color in the fall?Pigments carotene (red/orange) and xanthophyll (yellow)

Help absorb sunlight with chlorophyll for photosynthesis.

What major change occurs during winter?

Carotene and xanthophyll are responsible for supplying light energy to the plant.

Name:EXIT PASSNov 4 1. What materials enter the chloroplast that are used in the light-dependent reactions?

2. What material comes into the chloroplast that is used in the Calvin Cycle?

3. What material exits the chloroplast from the light-dependent reactions?

4. How do plants receive electrons for use in Photosystem II?

5. What materials move from the L-D reactions to the Calvin Cycle?

Which steps produce these materials?

6. What materials move from the Calvin Cycle back to the LDR?