Transcript of Unit 6- Photosynthesis & Cellular Respiration 6a- Photosynthesis.
- Slide 1
- Unit 6- Photosynthesis & Cellular Respiration 6a-
Photosynthesis
- Slide 2
- First Homework (New Semester) Bring a leaf to class
tomorrow
- Slide 3
- Life Requirements All organisms need a constant source of
energy to survive. The ultimate source of energy for most life on
Earth is the Sun.
- Slide 4
- Trapping the Suns Energy Photosynthesis is the overall process
by which solar energy is used to chemically convert water and
carbon dioxide into chemical energy stored in simple sugars.
Involves a complex series of chemical reactions in which the
product of 1 reaction is a reactant in the next
- Slide 5
- Photosynthesis The process of photosynthesis is generally
represented using a balanced chemical equation. However, this
equation does not represent all of the steps that occur. Sunlight
6CO 2 + 6H 2 O C 6 H 12 O 6 + 6O 2
- Slide 6
- Steps of Photosynthesis Photosynthesis can be divided into two
stages Light-dependent Reaction Solar energy is absorbed by
chloroplasts and two energy-storing molecules (ATP & NADPH) are
produced. Calvin Cycle (Light-independent reaction) Simple sugars
(glucose) are formed using CO 2 & the energy stored in ATP
& NADPH
- Slide 7
- Structure of Chloroplasts Photosynthesis takes place in the
chloroplasts Each chloroplast is surrounded by a pair of membranes.
Inside the inner membrane is another system of membranes called
thylakoids. Arranged as hollow disks Connected & layered to
form stacks called grana Surrounding the grana is a solution called
the stroma.
- Slide 8
- Where does each step take place? Light-dependent reactions take
place in the membranes of the thylakoid disks Calvin Cycle takes
place in the stroma
- Slide 9
- Review of Light Light from the sun- white light Can be
separated into its component colors by passing the light through a
prism Results in the visible spectrum (ROYGBIV) When white light
strikes an object, its component colors can be reflected,
transmitted, or absorbed. Pigments- compounds that absorb light
Most absorb certain colors more strongly than others, so the light
that is reflected no longer appears white.
- Slide 10
- The Role of Chloroplasts and Pigments The thylakoid membranes
contain the pigments that can absorb certain wavelengths of
sunlight. The most important pigment is chlorophyll. Absorb most
wavelengths of light except for green. Green is reflected making
the plants appear green. In the fall, plants reabsorb chlorophyll
leaving other pigments that reflect other wavelengths of light
making the leaves appear red, yellow, or orange.
- Slide 11
- Light-Dependent Reactions Sunlight strikes the chlorophyll
molecules in the thylakoid membrane. Chlorophyll absorbs the light
& the solar energy is used to split water molecules
(photolysis) Results in the release of oxygen (O 2 ) as a waste
product. Allows for the temporary transfer of the solar energy to
electrons released by the broken bonds Electrons are passed down an
Electron Transport Chain Photolysis
- Slide 12
- Light Dependent Reactions The Electron Transport Chain is a
series of proteins in the thylakoid membrane. As the electrons are
transferred from one protein to another, some energy is released.
This energy is used to make ATP & NADPH (electron carrier
molecule)
- Slide 13
- Light Dependent Reactions
- Slide 14
- Light-dependent Reactions Solar Energy absorbed by chloroplasts
NADPH released Oxygen released ATP Released Products of Light
Reactions (ATP and NADPH) fuel the Calvin Cycle
- Slide 15
- Video https://www.youtube.com/watch?v=joZ1EsA5
_NYhttps://www.youtube.com/watch?v=joZ1EsA5 _NY (3:30)
https://www.youtube.com/watch?v=sQK3Yr4
Sc_khttps://www.youtube.com/watch?v=sQK3Yr4 Sc_k (7:35-8:20, end of
light-dependent)
- Slide 16
- Calvin Cycle A series of enzyme-assisted chemical reactions
that produces 3-carbon sugars Occurs in the stroma of the
chloroplast Uses the ATP & NADPH that was produced during the
light reactions and CO 2 from the atmosphere
- Slide 17
- Calvin Cycle 1.Carbon Fixation: An enzyme combines CO 2 with a
5-carbon molecule called ribulose biphosphate (RuBP). 6-carbon
molecule is very unstable, so it immediately splits into two
3-carbon molecules called 3-phosphoglycerate (3-PGA or PGA)
2.Reduction Each 3-PGA is converted into another 3-carbon molecule,
PGAL (aka G3P) in 2 steps. 1- receive a phosphate group from ATP;
2- receive a proton from NADPH ADP & NADP+ will be used again
in light reaction 3.PGAL leaves & is used to build glucose (or
other carbohydrates). 4.Regeneration Remaining PGAL molecules
converted back to RuBP by the addition of a phosphate group from
ATP. Enter Calvin Cycle again.
- Slide 18
- The Calvin Cycle Uses Carbon Dioxide from the air Uses ATP and
NADPH from light reactions to build PGAL- a 3- carbon sugar The
3-carbon sugars can be used to build a glucose molecule Uses
another ATP to replenish RuBP Or the 3-carbon sugars can be
recycled to keep the Calvin Cycle going.
- Slide 19
- Photosynthesis Equation 6CO 2 + 6H 2 O C 6 H 12 O 6 + 6O 2
Carbon Dioxide from the air Used in the Calvin Cycle Water Split
during Photolysis in the Light Reactions Glucose Made in the Calvin
Cycle Oxygen Released during Photolysis in the Light Reactions
Light Energy chlorophyll Plants can use this glucose molecule for
energy during Cellular Respiration. Plants can also convert this
glucose molecule into other organic compounds such as proteins and
fats/lipids or other carbohydrates like starch and cellulose
- Slide 20
- Cycle of Photosynthesis
- Slide 21
- 3 Factors that Affect Photosynthesis Carbon Dioxide (CO 2 )
Without CO 2, the plant would not have one of the raw materials
needed for photosynthesis CO 2 is used in the first step of the
Calvin Cycle Temperature The temperature must be in the appropriate
range for the plant in order for photosynthesis to properly
occur
- Slide 22
- 3 Factors that Affect Photosynthesis Intensity of Light If the
intensity of light is lower, the available energy for
photosynthesis is lower. In a greenhouse, if the light source is
further away, intensity is lower and less photosynthesis can occur
If light is not available at all, the light-dependent reactions
cannot occur (nor can they provide the materials used in the Calvin
Cycle)
- Slide 23
- Video https://www.youtube.com/watch?v=joZ1EsA5
_NYhttps://www.youtube.com/watch?v=joZ1EsA5 _NY (3:30)
https://www.youtube.com/watch?v=sQK3Yr4
Sc_khttps://www.youtube.com/watch?v=sQK3Yr4 Sc_k (8:20, end of
light-dependent)