Chapter 8
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Chapter 8. Wakefield 2010-2011. Photosynthesis - Energy & Life. Energy is the ability to do work Comes in many forms Light – heat – electrical – chemical Can be stored and released Can be changed from one form to another Light energy to chemical energy. Photosynthesis - Energy & Life.

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Chapter 8

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Chapter 8

Chapter 8

Wakefield

2010-2011


Photosynthesis energy life

Photosynthesis - Energy & Life

  • Energy is the ability to do work

    • Comes in many forms

      • Light – heat – electrical – chemical

    • Can be stored and released

    • Can be changed from one form to another

      • Light energy to chemical energy


Photosynthesis energy life1

Photosynthesis - Energy & Life

  • Autotrophs – organisms that can use light energy from the sun to produce chemical energy in the form of food

    • Producers

  • Heterotrophs – organisms which cannot make their own food

    • Consumers


Photosynthesis energy life2

Photosynthesis - Energy & Life

  • Energy comes in many forms

    • Light – heat – electrical – chemical

  • Energy can be changed from one form to another


Photosynthesis energy life3

Photosynthesis - Energy & Life

  • Living things use chemical energy

    • Living things store energy in 2 ways

      • Short term as ATP

        • Adenosine triphosphate

      • Long term as glucose or glycogen


Chapter 8

Figure 8-3 Comparison of ADP and ATP to a Battery

Section 8-1

ADP

ATP

Energy

Energy

Adenosine diphosphate (ADP) + Phosphate

Adenosine triphosphate (ATP)

Partially

charged

battery

Fully

charged

battery


Energy transfer

Energy Transfer

  • Energy from ATP is powers:

    • Cellular processes

      • Active transport

    • Synthesis of proteins & nucleic acids

    • Aids in responses to chemical signals from the cell membrane

    • Produce light (fireflies)


Energy transfer1

Energy Transfer

  • ATP stores only very small amounts of energy

  • ATP is great to for transferring energy over short terms

  • Not good for long term energy storage


Energy transfer2

Energy Transfer

  • Single molecule of sugar (glucose) stores more than 90 times the chemical energy as one molecule of ATP

  • ATP can be generated from ADP as needed by using the energy in glucose / and other foods


Chapter 8

Breakdown of glucose in the cell to form ATP


Photosynthesis

Photosynthesis

  • Jan van Helmont – 1643

    • Stated that trees gain most of their mass from water


Photosynthesis1

Photosynthesis

  • Joseph Priestley – 1771

    • Using a bell jar, a candle and a plant, he found that the plant releases oxygen


Photosynthesis2

Photosynthesis

  • Jan Ingenhousz– 1779

    • Found that aquatic plants also produce tiny bubbles / Oxygen

  • Julius Robert Mayer – 1845

    • Proposed that plants convert light energy into chemical energy


Photosynthesis3

Photosynthesis

  • Melvin Calvin – 1948

    • Traced the chemical path that carbon follow to form glucose

      • Now known as the Calvin Cycle


Photosynthesis4

Photosynthesis

  • Rudolph Marcus – 1992

    • Won the Nobel Prize for chemistry for describing the process by which electrons are transferred from one molecule to another in the electron transport chain


Photosynthesis5

Photosynthesis

  • The process in which autotrophs use energy from the sun (or chemicals) to convert water and carbon dioxide into high-energy carbohydrates (sugars & starches) and oxygen

  • Photosynthesis takes place in the chloroplast


Photosynthesis6

Photosynthesis

  • In addition to the sun’s energy, producers also need chlorophyll for photosynthesis

    • Chlorophyll is the light absorbing pigment in plants

      • Since chlorophyll absorbs light it is consequently absorbing energy which can be used in photosynthesis

    • Chlorophyll a and chlorophyll b

      • Absorb light in the red, blue and blue-violet parts of the spectrum

      • Does not absorb green light (reflects green light) so plants appear shades of green

    • Stored in chloroplast – where photosynthesis takes place


Chapter 8

Figure 8-5 Chlorophyll Light Absorption

Section 8-2

Absorption of Light by

Chlorophyll a and Chlorophyll b

Chlorophyll b

Chlorophyll a

V

B

G

Y

O

R


Critical thinking

Critical Thinking ? ? ? ?

  • How well would a plant grow under pure green or yellow light?


Critical thinking1

Critical Thinking ? ? ? ?

  • How well would a plant grow under pure green or yellow light?

    It would not grow well because chlorophyll does not absorb much light in the green or yellow region of the visible spectrum


Reactions of photosynthesis

Reactions of Photosynthesis

  • What happens when light is absorbed by chlorophyll in the chloroplast?

    • Light is a form of energy so . . .

      • Much of the energy from the light absorbed by the chlorophyll is transferred directly to electrons in the chlorophyll molecule

      • These high energy electrons make photosynthesis work

Plant cells with chloroplasts


Chapter 8

Photosynthesis: Reactants and Products

Section 8-2

Light Energy

Chloroplast

CO2 + H2O

Sugars + O2


Reactions of photosynthesis1

Reactions of Photosynthesis

  • Electron Carriers

    • Sun has so much energy it needs special carries to move it from the chlorophyll to other molecules

      • These carriers are called NADP+

        • Each NADP+ can “carry” 2 high energy electrons (e-)(energy) and 1 Hydrogen ion (H+)

          • Forms NADPH which traps and holds energy from the sun

      • NADPH then carries the energy from light absorption in the chlorophyll to chemical reactions elsewhere in the cell

        • This energy is then used for the cell’s needs; including the production of glucose


Reactions of photosynthesis2

Reactions of Photosynthesis

  • Two parts to photosynthesis -

    • Light Dependent Reactions – (requires light)

      • Produce O2 and convert light energy into ATP & NADPH

      • Occurs in the thylakoid of the cell (located in the chloroplast

        • aka the Photosystem II

    • Calvin Cycle ( needs no light )

      • Takes Carbon from CO2 & hydrogen from light dependent reaction to create C6H12O6 and releases oxygen as a waste product

        • Occurs in the stroma of the cell – just outside the thylakoid (inside the chloroplast)


Reactions of photosynthesis3

Reactions of Photosynthesis

  • Light Dependent Reaction (requires light) –

    • The sun’s energy is uses ADP and NADP (energy carriers)

    • Splits water taken up in the roots of the plant from the soil to create O2 and 2 high energy compounds (ATP and NADPH)

    • This energy is used to create energy containing sugars (glucose) in the Calvin Cycle (Light Independent Cycle)

    • O2 is given off as a waste product into the atmosphere


Reactions of photosynthesis4

Reactions of Photosynthesis

  • Calvin Cycle – aka Light Independent Cycle – (does not require light)

    • Uses high energy compounds ATP & NADPH (created in the Light Dependent Cycle)

    • Removes CO2 from the atmosphere

    • Uses 6 molecules of CO2 to produce 1 molecule of C6H12O6

    • Produces high energy sugars (glucose)

      • The plant uses this sugar to:

        • meet its energy needs

        • Growth & development

      • Consumers use this sugar for their energy needs when they eat the producer


Chapter 8

Light-

dependent

reactions

Calvin cycle

Energy from

sunlight

Thylakoid

membranes

ATP

Stroma

NADPH

High-energy

sugars

ATP

NADPH

O2

Chloroplasts

Concept Map

2 Parts to Photosynthesis

Section 8-3

Photosynthesis

includes

takes place in

uses

use

take place in

to produce

to produce

of


Factors affecting photosynthesis

Factors Affecting Photosynthesis

  • Temperature

    • Best between 0oC and 35oC

    • At very low temperatures photosynthesis may stop completely

  • Light Intensity

    • Increasing the intensity of light increases the rate of photosynthesis . . . to a certain point – once photosynthesis has reached its maximum rate it cannot increase more

      • This maximum level varies from plant to plant


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