January 8, 2014!
Welcome Back! Bellringer: Photosynthesis … Pass back exams
Go over EVERY question Diagnose Wrong Answers
Start Photosynthesis Notes HW:
Draw and Define the parts of the Chloroplast (pg. 111)
1/9/14 Bellringer: 6…5…4… Check off HW
Photosynthesis Notes
HW: Read 114-116
(or at least the chapter summary)
Photosynthesis
What does it mean to photosynthesize?
Who Photosynthesizes?
Name the reactants and products of photosynthesis.
Photosynthesis Photosynthesis: When light energy is used
by producers/autotrophs to make sugars and other food molecules ~75% performed in the ocean Temperature, light intensity, water and carbon
dioxide supply affect the efficiency
Photosynthesis Reactants/Products
Reactants: CO2: Let into the leaf through pores called stomata H2O: Taken in through the roots
Catalyst: Chlorophyll: Pigment in chloroplast that catches sunlight
Products: O2: Used by plants/animals for cellular respiration Glucose: Used by the plant (or by an animal that eats the
plant!) for energy (C6H12O6)
Oxidation-Reduction Reactions Reactions that give or take electrons are
called “oxidative-reduction reactions” or Redox rxns
Oxidation = Molecules lose electrons or hydrogen
Reduction: Molecules gain electrons or hydrogen
In organisms, each electron travels with a proton (an H atom)…
Increasing energy
Gammarays
X-rays UV InfraredMicro-waves
Radiowaves
Visible light
380 400 500 600 700 750
Wavelength (nm)
650nm
10–5 10–3nm 1 nmnm 103 nm 106 nm 1 m 103 m
Why do we see certain colors?
Why do we see this red sweatshirt as red?
Answer: When all colors (ROYGBIV) hit it, all colors are absorbed but red, which is reflected back to our eyes!
Why do white things LOOK white?
Because all the colors (ROYGBIV) are hitting the object, and all the colors are reflecting back into your eyes
Why do black things LOOK black?
Because all the colors (ROYGBIV) are hitting the object, and all the colors are being absorbed
Pigments (start writing notes
again) Pigments: The natural coloring matter of
organisms Several pigments are built into the thylakoids of
chloroplasts These absorb some wavelengths of light; reflect or
transmit others Chlorophyll a:
Absorbs blue-violet and red light, reflects green light
Participates directly in the light reactions
Cont’d Chlorophyll b:
Absorbs blue and orange light, reflects yellow-green
Gives absorbed energy to chlorophyll a Carotenoids:
Yellow-orange pigments Pass energy to chlorophyll a or protect it by
dissipating excessive light energy Xanthophylls:
Yellow pigments
Stage 1: Light Reactions The light reaction takes place in the
thylakoid (disc inside the chloroplast
Chloroplast
Thylakoid
Photo Review
1) What is the formula for photosynthesis? (should know this by memory)
2) What are the four pigments in chlorophyll?
3) Why aren’t plant’s roots green?
Photosynthesis RXNs
Photosynthesis takes place in two stages: Light-Dependent Stage: Light-Independent/Calvin Cycle:
Stage 1: Light Reactions When photosynthesizers absorb sunlight, it
boosts their electrons to higher energy levels It EXCITES them
The electron now has more energy
PARTS OF THE LIGHT RXN
1) Photosystem: First part of the light reaction that gathers light. Contains the following:
A.Pigment Molecules: these absorb sunlight and give their energy to Chlorophyll a
B.Chlorophyll a Reaction Center: The molecule whose electron gets excited, and moves on to…
C.Primary Electron Acceptor: These take the electron from the reaction centerThere are 2 photosystems in the light reaction
A. Photosystem II: (P680), and Photosystem I: (P700)
Electron Transport Chain (ETC)
Electron transport chain(ETC): Series of proteins in the thylakoid membrane that makes the products of the light reaction
Takes the high energy electrons from the photosystems
Uses the electrons’ energy is to make ATP and NADPH ATP: Made from ADP NADPH: Carries electrons to the light-
independent reaction, made from NADP+
Steps of the Light Reaction
1. Light excites an electron (e-)in Photosystem II’s reaction center, and it goes to the Electron Transport Chain
2. A water molecule replaces the lost electrons3. e- moves down ETC (electron transport
chain),and this makes ATP4. Light excites an electron in Photosystem I’s
reaction center, and it goes to the second Electron Transport Chain
5. e- moves down ETC, which makes NADPH
LIGHT RXN SUMMARY
What do plants enter the light reaction with? Energy from sunlight and pigments to absorb it
What do plants leave the light reaction with? ATP and NADPH
WHAT DO WE HAVE LEFT TO DO? Actually build the glucose molecule!!!
The Light-Independent Reaction/Dark Reaction/Calvin Cycle
2nd part of Photosynthesis, and occurs in the stroma
Uses carbon atoms from CO2 to make the backbone of a sugar molecule (glucose) Glucose is made
ATP is used to get the energy for this (recycling)
Molecules of NADPH donate electrons and become NADP+ (recycling)
THE OVERALL LIGHT-INDEPENDENT REACTION!!!
What do plants enter with? ATP, NADPH, and CO2
What do plants leave the light reaction with? Glucose
Bellringer What is the equation
for photosynthesis? What products have
we made thus far? Where does the light
reaction take place?
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