Photosynthesis Photosynthesis Chapter 8 Chapter 8
Dec 28, 2015
PhotosynthesisPhotosynthesisChapter 8Chapter 8
Autotrophs vs. HeterotrophsAutotrophs vs. Heterotrophs
Autotrophs: Plants and some other types of organisms that use light energy from SUNLIGHT to make their own food. These organisms undergo photosynthesis!! – EX: Trees, grass, algae, plants
Heterotrophs: Organisms that CANNOT use the sun’s energy to make food– they obtain energy from the foods they consume – EX: Deer, rabbits, bear, fish, insects, etc…
The Photosynthesis EquationThe Photosynthesis Equation
Photosynthesis uses the energy of sunlight to convert water and carbon dioxide into high energy sugars and oxygen
6CO2 + 6H2O + light→C6H12O6 + 6O2
(carbon dioxide + water + light → sugars + oxygen)
Plants then use the sugars to produce complex carbohydrates such as starches
Plants obtain CO2 from the air or water in which they grow
PhotosynthesisPhotosynthesis
Light Energy
CO2 + H2O Sugars + O2
Chloroplast
Inside a ChloroplastInside a Chloroplast
Chloroplast= Filled with chlorophyll and are where photosynthesis takes place in plants and other photosynthetic eukaryotes – Thylakoids= saclike photosynthetic membranes
arranged into stacks known as grana. Area where light-dependent reactions take place
– Photosystems= clusters of chlorophyll and other pigments that are organized by the thylakoids
– Stroma= Area outside the thylakoid membranes where light- independent reactions
Light-dependent ReactionsLight-dependent Reactions
Absorption of Light byChlorophyll a and Chlorophyll b
V B G YO R
Chlorophyll b
Chlorophyll a
Section 8-2
Figure 8-5 Chlorophyll Light Absorption
Electron CarriersElectron Carriers
Electron Transport= The transfer of a pair of high energy electrons & their energy to another molecule
Electron Carriers= The “bucket” or carrier that moves electrons and their energy from molecule to the next EX: NADP+: Accepts and holds a pair of high-energy electrons
and an H+ ion, converting NADP+ into NADPH turning energy from the sun into chemical energy .
An analogy would be a pan carrying hot coals like the NADP+ carries two electrons and a H+ ion.
ATP FormationATP Formation
Adenosine Triphosphate (ATP)Adenosine Triphosphate (ATP)
Adenine Ribose 3 Phosphate groups
ADP and ATP (Electron Carriers)ADP and ATP (Electron Carriers)
ATPADP
Energy
Adenosine diphosphate (ADP) + PhosphateEnergy
Adenosine triphosphate (ATP)
Partiallychargedbattery
Fullychargedbattery
Light-Dependent ReactionsLight-Dependent Reactions
Light-Dependent Reactions: Use energy from sunlight to produce the energy carriers ATP and NADPH and oxygen. – Reactions occur within the thylakoid
membranes of chloroplasts
Light-dependent ReactionsLight-dependent Reactionshttp://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/
free/0072437316/120072/bio13.swf::Photosynthetic%20Electron%20Transport%20andfree/0072437316/120072/bio13.swf::Photosynthetic%20Electron%20Transport%20and%20ATP%20Synthesis%20ATP%20Synthesis
HydrogenIon Movement
Photosystem II
InnerThylakoidSpace
ThylakoidMembrane
Stroma
ATP synthase
Electron Transport Chain Photosystem I ATP Formation
Chloroplast
Section 8-3
Figure 8-10 Light-Dependent Reactions
PhotosynthesisPhotosynthesis
Steps in PhotosynthesisSteps in Photosynthesis
Photosynthesis: Has five major steps that occur within the thylakoid membrane of the chloroplast – 1. Photosystem II: Light absorbed by photosystem
II is used to break up water molecules into energized electrons, hydrogen ions (H+) and oxygen.
– 2. Electron Transport Chain: High-energy electrons from photosystem II move through the electron transport chain into photosystem I.
Steps in PhotosynthesisSteps in Photosynthesis
– 3. Photosystem I: Electrons released by photosystem II are energized again in photosystem I. Enzymes in the membrane use these electrons to make NADPH/
– 4. Hydrogen Ion Movement: The inside of the thylakoid membrane is charged with H+ ions. This causes the outside of the thylakoid membrane to be negatively charged and the inside of the membrane to be positively charged.
Steps in PhotosynthesisSteps in Photosynthesis
– 5. ATP Formation: As hydrogen ions pass through ATP synthase, their energy is used to convert ADP into ATP. As it rotates ATP synthase (enzyme) binds ADP and P+ group to create ATP. Because of this, light-dependent transport produces high energy electron AND ATP.
SUMMARY: Light dependent reactions use water, ADP and
NADP+ to produce oxygen, ATP and NADPH (Water, ADP, NADP+ Oxygen, ATP, NADPH)
ATP and NADPH then provide energy to build energy containing sugars from low-energy compounds.
Light-independent ReactionsLight-independent Reactions
Calvin Cycle: Energy stored in the ATP and NADPH formed during photosynthesis, is used to build high-energy sugars that can be stored for a long period of time. – Does not require light and is called light
independent reaction – Takes place in the stroma of the
chloroplasts
Calvin CycleCalvin Cyclehttp://highered.mcgraw-hill.com/sites/0070960526/student_view0/chapter5/animation_quiz_1.htmlhttp://highered.mcgraw-hill.com/sites/0070960526/student_view0/chapter5/animation_quiz_1.html
Steps in the Calvin CycleSteps in the Calvin Cycle
The Calvin Cycle has four major steps: – 1. C02 Enters the Cycle: 6 CO2 molecules are
combined with six 5- carbon molecules to produce three 12-carbon molecules
– 2. Energy Input: Energy from ATP and electrons from NADPH convert the twelve 3-carbon molecules into higher-energy forms
– 3. 6-Carbon Sugar Produced: two 3-carbon molecules are removed to produce sugars, lipids, amino acids, and other compounds
Steps in the Calvin CycleSteps in the Calvin Cycle
– 4. 5-Carbon Molecules Regenerated: the 10 remaining 3-carbon molecules are converted back into six 5-carbon molecules, which are used to start the next cycle : )
ChloropIast
CO2 Enters the Cycle
Energy Input
5-CarbonMoleculesRegenerated
Sugars and other compounds
6-Carbon SugarProduced
Section 8-3
Figure 8-11 Calvin Cycle
Photosynthesis
includes
of
take place intakes place in uses
to produce to produce
use
Light-dependentreactions
Calvin cycle
Thylakoidmembranes Stroma NADPHATPEnergy from
sunlight
ATP NADPH O2 Chloroplasts High-energysugars
Section 8-3
Concept Map
Chloroplast
Light
O2
Sugars
CO2
Light-Dependent Reactions
CalvinCycle
NADPH
ATP
ADP + PNADP+Chloroplast
Section 8-3
Figure 8-7 Photosynthesis: An Overview
Factors Affect PhotosynthesisFactors Affect Photosynthesis
Various Factors Affect the Rate of Photosynthesis.
Some of these factors are:1. Amount of available water
– EX: Plants in dry areas have waxy leaves to prevent water loss
2. Temperature – EX: Enzymes work best between 0° and 35°C. Temps
above or below this range may slow down photosynthesis or stop it entirely
3. Light Intensity 1. EX: The higher the intensity the higher the rate of
photosynthesis. There is a maximum limit however. This varies from plant to plant