Chapter 8 Photosynthesis. 8-1 Energy and Life Autotrophs Make their own food 8-1 Energy and Life.
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Transcript of Chapter 8 Photosynthesis. 8-1 Energy and Life Autotrophs Make their own food 8-1 Energy and Life.
Chemical Energy and ATP
• The principal chemical compounds that cells use to store and release energy is called ATP adenosine triphosphate
8-1 Energy and Life
Storing Energy• ATP stores energy in the third
phosphate
• ATP is like a fully charged battery
8-1 Energy and Life
Releasing Energy
A: Break bond between the second and 3rd phosphates
ADP
2
Q: How is the energy in ATP released?
8-1 Energy and Life
Using Biomechanical Energy
• Active Transport
• Movement of organelles through cell
• Sythesis of proteins and nucleic acids
• Produce light– Blink of firefly caused by an enzyme
powered by ATP
8-1 Energy and Life
ATP Availability
• Most cells only have enough ATP for a few seconds of activity
• Why?– Not good at storing energy over the long term– Glucose stores 90X the chemical energy of ATP– Cells generate ATP from ADP as needed by
using the energy in foods like glucose
8-1 Energy and Life
During Photosynthesis…
• Organisms (plants) absorb light energy from the sun and store it in organic compounds.
• Energy is crucial to all life, without it work could not be done.
8-2 Photosynthesis an Overview
Photosynthesis is the process by which autotrophic organisms use light energy to make sugar and oxygen gas from carbon
dioxide and water
AN OVERVIEW OF PHOTOSYNTHESIS
8-2 Photosynthesis an Overview
The Photosynthesis Equation
CO2 + H2O +C6H12O6 O2light
(Carbon Dioxide) (Water) (Sun) (Glucose) (Oxygen)
8-2 Photosynthesis an Overview
Because light is a form of energy…
• Anything that absorbs light also absorbs the energy from that light
• When chlorophyll absorbs light, much of the energy is transferred to electrons in the chlorophyll molecule, raising the energy level of these electrons
• These high-energy electrons make photosynthesis work
8-2 Photosynthesis an Overview
Chloroplasts
• The site of Light Dependent Reactions
• These organelles are surrounded by a double membrane and contain an
inner membrane separate into disk like sacs called thylakoids
• Thylakoid are arranged into granum, or neat stacks
• Each thylakoid contains the green pigment chlorophyll
• The light absorbing pigments are organized into photosystems, which transfer energy during the light reactions
8-2 Photosynthesis an Overview
Pigments in chloroplasts
• Chloroplasts absorb all other color pigments, leaving green to be reflected resulting in a plant’s color.
• Chlorophyll a and b are
two are the 2 most
common types of chlorophyll
• Chlorophyll b absorbs colors or
light energy NOT absorbed by
chlorophyll a
Light Reflectedlight
Absorbedlight
Transmittedlight
Chloroplast
8-2 Photosynthesis an Overview
Absorption of Light byChlorophyll a and Chlorophyll bAbsorption of Light byChlorophyll a and Chlorophyll b
V B G YO R
Chlorophyll b
Chlorophyll a
8-2 Photosynthesis an Overview
Scientists describe the reactions of photosynthesis in two parts
1. Light – dependent reactions (in the thylakoid membranes)
2. Light – independent reactions (takes place in stroma)
8-3 Reactions of Photosynthesis
Photosynthesis Consists of 2 Stages
• Light dependent reactions
• Take place in the Thylakoid Membrane
• Depends on sunlight for activation energy
• Responsible for the absorbing of light in Photosynthesis
• Water is split, • giving off oxygen
• H2O + O2 + ATP + NADPH2
• Non-light dependent (dark) reactions
• Takes place in the Stroma
• Includes the Calvin cycle
• Does not literally occur in the dark, but requires no light to occur
• Carbon dioxide is split, • Carbon to make sugars
• ATP + NADPH2 + CO2 + C6H12O6
8-3 Reactions of Photosynthesis
Carrier Molecule• Compound that can accept a pair
of high energy electrons and transfer them along with most of their energy to another molecule
• Ex.) NADP+
8-3 Reactions of Photosynthesis
Q: What does this do?• NADP + H NADPH
A: this traps sunlight in chemical form
8-3 Reactions of Photosynthesis
Light Dependent Reactions
• Uses energy from light to produce
1. Oxygen gas
2. ATP
3. NADPH
8-3 Reactions of Photosynthesis
Watch The Light Reaction Video
8-3 Reactions of Photosynthesis
Watch The Light Reaction Video
8-3 Reactions of Photosynthesis
The Calvin Cycle• The ATP and NADPH formed by the light-
dependent reactions contain an abundance of chemical energy, but they are not stable enough to store that energy for more than a few minutes.
• The Calvin cycle uses ATP and NADPH from light – dependent reactions to produce high energy sugars
8-3 Reactions of Photosynthesis
The Calvin Cycle• These reactions don’t require
light, therefore these reactions are called
• Light – independent reactions
8-3 Reactions of Photosynthesis
Watch The Calvin Cycle Video
8-3 Reactions of Photosynthesis
Watch The Calvin Cycle Video
8-3 Reactions of Photosynthesis
Factors Affecting Photosynthesis
• Not enough water
• Temperature
• Light intensity
8-3 Reactions of Photosynthesis
Review: Photosynthesis uses light energy to make food molecules
Chloroplast
Light
Stack ofthylakoids ADP
+ P
NADP
Stroma
Lightreactions
Calvincycle
Sugar used for
Cellular respiration Cellulose
Starch
Other organic compounds
8-3 Reactions of Photosynthesis