March 14, 2011Agenda: Photosynthesis Lesson

Photosynthesis WorksheetReview: Respiration Exam

Lab Activity 24

Do Now:1) Pass forward light-reaction drawings2) Describe what happens when chlorophyll

absorbs light energyElectrons become excited, and are passed down the electron transport chain on the thylakoid

membrane

Experimental set up

Test tube #1: Test Tube #2:(Experimental) (Control)Light LightChloroplasts ChloroplastsH2O H2ONo CO2 CO2

If there is no CO2, very little oxygen was produced

AIM: Why is carbon dioxide necessary for photosynthesis?

Review: Photosynthesis

CO2 + H2O (light energy) C6H12O6 + O2

H2O 2 H2 + O2

• This reaction is very endergonic• Hydrolysis: splitting of water

• Water is being OXIDIZED

http://www.youtube.com/watch?v=OTEX38bQ-2w

If water is being oxidized, what else must happen?

Water is oxidized, NADP is reduced

On a sunny day, the light dependent reactions will occur rapidly. NADP

will be reduced to NADPH. There is a limited amount of NADP in the

thylakoid of the plant. …What’s the problem?

NADPH needs to be recycled to NADP for

photosynthesis to continue to occur.

• NADPH will lose its hydrogen;CO2 will act as a hydrogen acceptor

Dark Reactions, Light-Independent Reactions,

Calvin Cycle: NADPH and CO2 will be used to make

glucose.

Light Reactions: Summary

Do Now: Take out homework

Dark Reactions

• Synthesis of glucose from NADPH2 and CO2 using ATP energy

• Takes place in the stroma of the cell

Dark Reactions

• Calvin was interestedin studying the processOf the “Dark Reactions”

Calvin traced carbon using a radioactive isotope (C14)

• Chlorella- algae

Do Now: Why are the following necessary for photosynthesis?

• Water: donates H+’s to form a hydrogen gradient and electrons through the ETC

• CO2: combines with hydrogen from NADP to produce glucose

• Light- excites electrons to pass through ETC

Review Calvin’s Experiment

• Whoops! Not THAT Calvin….

Calvin’s Problem: How can carbon dioxide form glucose

during photosynthesis?

Calvin’s Experiment1) Calvin exposes the Chlorella (algae) to

radioactive C 14 in C 14 O2

2) Allows photosynthesis to occur in lollipop apparatus

3) “Freezes” the reaction using ethanol alcohola) release chlorophyll b) denature the enzymes involved in photosynthesis

4) Separates out radioactive carbon using CHROMATOGRAPHY

Chromatography- technique of separating different pigments based on chemical properties

5. Observes radioactive compounds using “radioautography”

• Technique that allows radioactive carbon to become visible.

• By freezing photosynthesis at different times, Calvin was able to trace how carbon dioxide was converted to sugar.

AIM: What did Calvin discover?

Results of Calvin’s Experiment

Glycolysis

Calvin Cycle: A

STEP A: Six carbon dioxide molecules enter the cycle from the atmosphere. The carbon dioxide molecules combine with six 5-carbon molecules. They rearrange to form 3 carbon molecules.

Step B: Energy investment stage

• The 12 3 carbon molecules are then converted into higher energy forms. The energy for this conversion comes from ATP and NADPH

• Where does the ATP and NADPH come from?

STEP C: Two of the twelve 3-carbon molecules rearrange

into two similar 3 carbon molecules (PGAL)

Sheesh! That’s a lot of biochem..

• Let’s summarize:

How many CO2 are needed to synthesize 1 glucose?

How many ATP are needed to synthesize 1 glucose?

How many NADPH are needed to synthesize 1 glucose?

Calvin Cycle

• Energy input• Plants use energy that ATP and

NADPH

Do Now:

• Take out homework

• Calvin Cycle ReviewHow many:CO2 = 6ATP= 18 ATPNADPH= 12 NADPH

http://www.youtube.com/watch?v=_NIhg1qa_L0

AIM: Why did the plant die?

Hypothesis: If the plant dies, then Photosynthesis is

not occurring

Materials: Benedict’s Solution and Lugol’s Solution

• Indicators for glucose and starch

Factors that may affect photosynthesis:

1) Sunlight2) Water3) CO24) Nutrients in the soil5) Temperature

Plants can still produce glucose for a short time in the

dark…. Why?• However, Plants

need NADPH and ATP from the Light-

Dependent reactions

to continue photosynthesis

Rainforest Desert

• Large, broad leaves Small, needlike leaves Cuticle covering

How can temperature affect photosynthesis?

Enzymes in Photosynthesiswork best between0 and 35 degreesCelsius, after 35Celsius, enzymesdenature

How will carbon dioxide affect photosynthesis?

• Carbon Dioxide is necessary during the Calvin Cycle to produce glucose

How will water affect photosynthesis?

How will water be transported to the top of trees?

Root Pressure

• Concentration of nutrients and sugar is higher inside the roots than

outside the plant…

Water will move viaOsmosis into the roots

Cohesion-Adhesion

• Cohesion: waterMolecules attract toOne another

• Adhesion: waterAttracts to other sub-Stances

• Cohesion and Adhesion lead to capillary action- tendency for water to rise in a thin tube

Transpirational Pull- water moves into the leaves via

osmosis Transpiration: loss of water

through the leaves

Root pressure, capillary action, and transpirational pull contribute to the movement of water within a plant

Wilting

• Too little water decreases TURGOR pressure in a plant, causing it to wilt

Summary: What may be wrong with Ms. Simon’s plant?