Chapter 8 Chapter 8 PhotosynthesisPhotosynthesis

Section 8-1Section 8-1Energy and LifeEnergy and Life

Energy is the ability to do workEnergy is the ability to do work Without energy, life would cease to Without energy, life would cease to

existexist The energy in most food comes from The energy in most food comes from

the sunthe sun

A.A. Autotrophs Autotrophs

Organisms that make their own food-Organisms that make their own food-

either photosynthetic or chemosyntheticeither photosynthetic or chemosynthetic

B. HeterotrophsB. Heterotrophs

Obtain energy from the foods they Obtain energy from the foods they consume-plant, animals or decomposing consume-plant, animals or decomposing mattermatter

C. Chemical Energy and ATPC. Chemical Energy and ATP

1. Energy comes in different forms1. Energy comes in different forms

a. light, heat, and electricitya. light, heat, and electricity

b. can also be stored in chemical b. can also be stored in chemical compoundscompounds

2. ATP – adenosine triphosphate2. ATP – adenosine triphosphate

a. adenine, ribose, and 3 phosphate a. adenine, ribose, and 3 phosphate groupsgroups

b. 3 phosphates – give the ability to b. 3 phosphates – give the ability to store store and release energyand release energy

i. Storing Energyi. Storing Energy

- when energy is available it adds - when energy is available it adds a a phosphate group to ADP (like phosphate group to ADP (like a a full battery)full battery)

ii. Releasing Energyii. Releasing Energy

- energy released by breaking the - energy released by breaking the bond between the bond between the

phosphate phosphate groupsgroups

- basic energy source of all cells- basic energy source of all cells

DRAW ATP MOLECULEDRAW ATP MOLECULE

D. Using Biochemical Energy (Using ATP) D. Using Biochemical Energy (Using ATP) 1. Active Transport1. Active Transport2. Motor Proteins- to move organelles2. Motor Proteins- to move organelles3. Synthesis of proteins and nucleic acids3. Synthesis of proteins and nucleic acids

E. ATP is a useful source of Energy, but it E. ATP is a useful source of Energy, but it is not a good long-term energy is not a good long-term energy

storage moleculestorage molecule1.1. Most cells only have a small amount of Most cells only have a small amount of

ATPATP2.2. One single molecule of glucose stores One single molecule of glucose stores

90 times the chemical energy of an 90 times the chemical energy of an ATP moleculeATP molecule

3.3. Cells can regenerate ATP from ADP Cells can regenerate ATP from ADP as needed by using the energy in as needed by using the energy in foods like glucosefoods like glucose

Section 8-2Section 8-2Photosynthesis: An Photosynthesis: An OverviewOverview

Photosynthesis – the key cellular process Photosynthesis – the key cellular process identified with energy productionidentified with energy production

Plants use sunlight to convert water and Plants use sunlight to convert water and carbon-dioxide into high energy carbon-dioxide into high energy carbohydrates and oxygencarbohydrates and oxygen

A. Scientists A. Scientists Investigating Investigating PhotosynthesisPhotosynthesis

1.1. Van HelmontVan Helmonta. concluded that trees gain most of a. concluded that trees gain most of

their mass from watertheir mass from waterb. he did not account for the carbon part b. he did not account for the carbon part

of the equation (COof the equation (CO22))

2. Priestley2. Priestleya. candle experiment – jar and the mint a. candle experiment – jar and the mint

plant – release oxygenplant – release oxygen

3. Jan Ingenhousz3. Jan Ingenhousz

-showed Priestley’s effect only occurred in -showed Priestley’s effect only occurred in the presence of lightthe presence of light

- light is necessary for plants to produce - light is necessary for plants to produce oxygenoxygen

B. Photosynthesis EquationB. Photosynthesis Equation

6CO2 + 6H2O + Sunlight --> C6H12O6 + 6O2

- Photosynthesis uses energy from sunlight to - Photosynthesis uses energy from sunlight to convert carbon dioxide and water into convert carbon dioxide and water into glucose and oxygenglucose and oxygen

C. Light and PigmentsC. Light and Pigments

1. photosynthesis requires light and 1. photosynthesis requires light and chlorophyll – found in chloroplastschlorophyll – found in chloroplasts

2. Plants use pigments to gather the sun’s 2. Plants use pigments to gather the sun’s energyenergy

3. Chlorophyll – plant’s key pigment3. Chlorophyll – plant’s key pigment

- chlorophyll chlorophyll a- a- absorbs red and violet absorbs red and violet wavelengths of light

- chlorophyll - chlorophyll b – b – absorbs red-orange absorbs red-orange and blue wavelengthsand blue wavelengths

Section 8-3Section 8-3The Reactions of PhotosynthesisThe Reactions of Photosynthesis

1.1. Inside a chloroplastInside a chloroplasta. Where photosynthesis takes placea. Where photosynthesis takes placeb. Structuresb. Structures

i. Thylakoids – saclike photosynthetic i. Thylakoids – saclike photosynthetic membrane (pancakes)membrane (pancakes)

- proteins in the thylakoid - proteins in the thylakoid organize organize chlorophyll into clusters chlorophyll into clusters called called photosystems (light-photosystems (light-collecting units)collecting units)

ii. Grana – Stack of thylakoidsii. Grana – Stack of thylakoidsiii. Stroma – region outside the iii. Stroma – region outside the

thylakoid thylakoid membrane (syrup)membrane (syrup)

2 reactions2 reactions

--Light-dependent- Light-dependent- in the in the thylakoid membranethylakoid membrane

- - Light-independent (Calvin Cycle) – Light-independent (Calvin Cycle) –

in the stromain the stroma

2. Electron Carriers2. Electron Carriers

a. sunlight excites the electrons in chlorophyll a. sunlight excites the electrons in chlorophyll – high in energy– high in energy

b. NADPb. NADP+ + - electron carrier- electron carrier

- can accept a pair of high energy - can accept a pair of high energy electrons and a hydrogen ion (Helectrons and a hydrogen ion (H++))

- this converts NADP- this converts NADP++ to NADPH to NADPH

c. this makes up the Electron Transport c. this makes up the Electron Transport Chain (ETC)Chain (ETC)

d.d. NADPH carries the electrons to Calvin NADPH carries the electrons to Calvin cyclecycle

3. Light-Dependent Reactions3. Light-Dependent Reactions

a. require lighta. require light

b. produce oxygen gasb. produce oxygen gas

c. convert ADP and NADPc. convert ADP and NADP++ into energy into energy carriers ATP and NADPHcarriers ATP and NADPH

Light-Dependent ReactionsLight-Dependent Reactions

A. Photosystem II absorb lightA. Photosystem II absorb light

- electrons absorb energy- electrons absorb energy

- passed on to the ETC- passed on to the ETC

- thylakoid replaces electrons with - thylakoid replaces electrons with electrons from broken apart Helectrons from broken apart H220 0

moleculesmolecules

- Oxygen is released into the air - Oxygen is released into the air

- H- H++ ions are released inside the ions are released inside the thylakoid thylakoid

B. e- go from PS II to PS I B. e- go from PS II to PS I

- energy from e- is used to pump the H- energy from e- is used to pump the H++ ions from the stroma into the thylakoid ions from the stroma into the thylakoid membranemembrane

C. Pigment in PS I use energy from light to C. Pigment in PS I use energy from light to reenergize the e-reenergize the e-

- NADP- NADP++ then again turns to NADPH then again turns to NADPH

D. As the electrons pass to NADP+ more H+ D. As the electrons pass to NADP+ more H+ ions are pumped across the membraneions are pumped across the membrane

- outside of membrane (-) charged- outside of membrane (-) charged

- inside of membrane (+) charged- inside of membrane (+) charged

- this charge difference provides the energy - this charge difference provides the energy needed to make ATPneeded to make ATP

E. ATP synthase – enzyme that allows the H+ E. ATP synthase – enzyme that allows the H+ ions to cross the membrane ions to cross the membrane

- as H+ ions pass through the enzyme - as H+ ions pass through the enzyme it it rotatesrotates

- as it rotates, ATP synthase binds the - as it rotates, ATP synthase binds the phosphate group to ADP phosphate group to ADP

making making ATPATP

- this produces not only high energy - this produces not only high energy electrons but ATP as wellelectrons but ATP as well

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4. 4. Light-Independent ReactionsLight-Independent Reactions

(Calvin Cycle)- (Calvin Cycle)-

American scientist Melvin CalvinAmerican scientist Melvin Calvin

- Uses ATP and NADPH to produce - Uses ATP and NADPH to produce sugars (short term storage)sugars (short term storage)

- contain a lot of chemical energy- contain a lot of chemical energy

- does not require light- does not require light

Light Independent ReactionsLight Independent Reactions

A. 6 COA. 6 CO22 molecules – enter cycle from molecules – enter cycle from

atmosphereatmosphere

- combine with (6) 5 Carbon molecules- combine with (6) 5 Carbon molecules

- produce (12) 3-Carbon molecules- produce (12) 3-Carbon molecules

B. (12) 3-Carbon molecules are converted B. (12) 3-Carbon molecules are converted into high energy formsinto high energy forms

- energy for conversion comes from ATP - energy for conversion comes from ATP and NADPHand NADPH

C. (2) of the 3-Carbon molecules are removed C. (2) of the 3-Carbon molecules are removed from the cycle to produce molecules needed from the cycle to produce molecules needed by the plant (glucose)by the plant (glucose)

D. The remaining (10) 3-Carbon molecules are D. The remaining (10) 3-Carbon molecules are converted back into (6) 5-Carbon moleculesconverted back into (6) 5-Carbon molecules

- These return to the beginning of the - These return to the beginning of the cycle cycle to restart the next cycle.to restart the next cycle.

Purpose of the Calvin CyclePurpose of the Calvin Cycle

- It uses (6) CO- It uses (6) CO22 molecules to make a molecules to make a single 6-carbon sugar molecule single 6-carbon sugar molecule (glucose)(glucose)

Light-dependent – Trap the energy from Light-dependent – Trap the energy from the sun in chemical formthe sun in chemical form

Light-independent – use the stored Light-independent – use the stored chemical energy to produce sugarschemical energy to produce sugars