chapter 6: photosynthesis mrs. stewart honors biology central magnet
TRANSCRIPT
Chapter 6: Photosynthesis
Mrs. StewartHonors BiologyCentral Magnet
Standards CLE 3210.3.3 - Investigate the
relationship between the processes of photosynthesis and cellular respiration.
SPI 3210.3.3 - Compare and contrast photosynthesis and cellular respiration in terms of energy transformation.
ObjectivesSummarize the reactants and
products of photosynthesis.Describe the reactants and
products of the light reactions.Describe the reactants and
products of the Calvin Cycle (dark reactions).
Summarize how the light reactions and Calvin cycle work together to create a continuous cycle of photosynthesis.
Q: Where does the energy come from in each stage of the food chain?
Think – Pair - Share
AutotrophsMake their own food
HeterotrophsCannot make their own food
WHAT is the energy? Much of the energy used by living
organisms is in the form of ATP
Chemical Energy and ATPThe principal chemical compound that cells use to store and release energy is called ATP (adenosine triphosphate)
Storing EnergyATP stores energy in the bond between the second and third phosphate group
ATP is like a fully charged battery
Energy
Releasing EnergyQ: How is the energy in ATP released?A: Break bond between the second and 3rd
phosphates
ADP
2
Think – Pair - Share
ATP vs. ADPATP – has all 3 phosphate groups
Fully charged battery Brief energy storage Can remove a phosphate group to release
energy and form ADP
ADP – has only 2 phosphate groups Partially charged battery Can add a phosphate group to make ATP
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 90 times the chemical energy of ATP
Cells generate ATP from ADP as needed by using the energy in foods (like glucose)
6-1:Photosynthesis
PhotosynthesisThe process in which plants use the energy of sunlight to convert water and carbon dioxide into high energy carbohydrates – sugars and starches – and oxygen as a waste product
Photosynthesis
6CO2 + 6H2O C6H12O6 + 6O2
LIGHT
(Carbon Dioxide) (Water) (Sun) (Glucose) (Oxygen)
Photosynthesis
The Visible Light Spectrum
Pigments Absorb different wavelengths of light
(colors) Reflect (transmit) what they do not
absorb We see what is reflected back.
ChlorophyllThe plant’s principal pigment
absorbs light energy blue-violet red
Absorption of Light byChlorophyll a and Chlorophyll b
Absorption of Light byChlorophyll a and Chlorophyll b
V B G Y O R
Chlorophyll b
Chlorophyll a
Q: Why are leaves green?
A: because chlorophyll absorbs the blue-violet and red light and reflects the green back.
Think – Pair - Share
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
Photosynthesis Basics
Where does photosynthesis take place?In organelles called chloroplasts.
ThylakoidsSac-like photosynthetic membranes arranged in stacks
GranaStacks of thylakoids
Granum – singularGrana - plural
StromaThe region outside the thylakoid
The watery region in a chloroplast
Similar to the cytoplasm in the cell
Photosynthesis occurs in two parts:
1. Light – dependent reactions (takes place in the thylakoid membranes)
2. Light – independent/Calvin Cycle reactions (takes place in stroma)
ANALYZE THE PICTURE List the reactants and products for
1. The light dependent reactions2. The Calvin Cycle (light independent)
reactions List the location where each reaction
occurs
Pg. 123
Light Dependent Reactions
“photo” part of photosynthesis Reactants:
H2O, energy from light (photons) NADP+, ADP+ and phosphate group
Products: Oxygen gas, ATP, NADPH
Q: Where did the Oxygen, produced by the light dependent reactions come from?
A: H2O
Think – Pair – Share
What you need to know:
Where do the light reactions occur?
What is needed (reactants)?
What is created (products)
In the thylakoids.
•Light (photons)•water
•ATP & NADPH - go on to Calvin cycle•Oxygen - that is released
Carrier MoleculeCompound that can accept a high energy electron and transfer it along with most of its energy to another molecule
Ex.) NADP+ + H NADPH
The Calvin CycleThe “synthesis” part of photosynthesis
These reactions don’t require light, therefore these reactions are called Light – Independent or Dark reactions
The Calvin CycleReactants: ATP and NADPH (from
light – dependent reactions) and CO2
Products: high energy sugars (C6H12O6) and NADP+ and ADP+ (which will go back to light dependent reaction for reuse)
Carbon FixationThe incorporation of CO2 into
organic compoundsThe Carbon in CO2 is “fixed” into
the usable energy form of sugar
6 CO2 molecules will go into the cycle to produce each organic molecule of 6-Carbon sugar. (C6H12O6 )
Factors Affecting Photosynthesis
Not enough waterTemperature Light intensityCO2 levels
Objectives (Did we…)Summarize the overall reactants
and products of photosynthesis.Describe the reactants and
products of the light reactions.Describe the reactants and
products of the Calvin Cycle (dark reactions).
Summarize how the light reactions and Calvin cycle work together to create a continuous cycle of photosynthesis.