Photosynthesis Chapter 7. Photosynthesis Almost all plants are photosynthetic autotrophs As are...
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Transcript of Photosynthesis Chapter 7. Photosynthesis Almost all plants are photosynthetic autotrophs As are...
Photosynthesis
Chapter 7
Photosynthesis
Almost all plants are photosynthetic autotrophs As are some bacteria and protists Generate their own organic matter through photosynthesis
Photosynthesis Occurs in chloroplasts Energized electrons are added to carbon dioxide to make
sugar Converts solar energy into the chemical energy of a
carbohydrate Sunlight provides the energy
Anatomy of a Plant
Carried out by the green portions of plants
Leaves contain mesophyll tissue specialized for photosynthesis
Water taken up by roots and transported to leaves by veins
Anatomy of a Plant
Carbon dioxide enters through openings in the leaves called stomata
Light energy absorbed by chlorophyll and other pigments in thylakoids of chloroplasts Main organelle that
carries out photosynthesis!!!!
Chloroplasts Are found in the interior cells of leaves Contain stroma, a thick fluid Contain thylakoids, membranous sacs
Photosynthetic Reaction
Glucose and oxygen are the products of photosynthesis Oxygen given off comes from water
CO2 gains hydrogen atoms and becomes a carbohydrate Reaction written as:
Two Steps…..
1. Light reactions convert solar energy to chemical energy Light-dependent
reactions take place only in presence
of light produce ATP and NADPH
2. Calvin cycle makes sugar from carbon dioxide Light-independent
reactions do not need light to occur result in the formation of
organic molecules
Light Reactions
An Overview of Photosynthesis
Photosystem Starting point of photosynthesis Network of pigments in the membrane of the
thylakoid molecules that absorb light energy primary pigment of a photosystem is chlorophyll pigments act as an antenna to capture energy from
sunlight individual chlorophyll pigments pass the captured energy
between them
How Plants Capture Energy from Sunlight
Light comprised of packets of energy called photons Sunlight has photons of varying energy levels
possible range of energy levels is represented by an electromagnetic spectrum
Human eyes only perceive photons of intermediate energy levels this range of the
spectrum is known as visible light
Chloroplasts absorb select wavelengths of light that drive photosynthesis
The light reactions of photosynthesis Two types of photosystems
cooperate in the light reactions Photosystem II
captures a photon of light and releases an excited electron to the electron transport system (ETS)
Photosystem I absorbs another photon of
light and releases an excited electron to another ETS
Electron transport chain
Connects the two photosystems Releases energy that the chloroplast uses to
make ATP
Calvin Cycle
Calvin Cycle
Light-independent These reactions are the second stage of
photosynthesis Functions like a sugar factory within a chloroplast Regenerates the starting material with each turn NADPH and ATP produced in light reactions used to
reduce carbon dioxide to a carbohydrate
Overview of Photosynthesis
Photosynthesis Versus Cellular Respiration Both plant and animal cells carry out cell respiration
Only plant cells photosynthesize Both processes utilize an electron transport chain
and chemiosmosis for ATP production Photosynthesis reduces CO2 to carbohydrates and
releases O2
Respiration utilizes O2 and gives off CO2
Photosynthesis and Respiration Compared
Environmental Impacts Photosynthesis has an enormous
impact on atmosphere. swaps O2 for CO2
Greenhouses used to grow plant indoors Trap sunlight that warms the air
inside The greenhouse effect
Warms the atmosphere Caused by atmospheric CO2
Greenhouse gases are the most likely cause of global warming Slow but steady rise in the Earth’s
surface temperature Destruction of forests may be
increasing this effect