Transcript Ch. 8 Photosynthesis - YISS

Ch. 8 Photosynthesis
• Autotroph – make their own food.
Ex. Plants
• Heterotroph – obtain energy from the foods they
consume.
Ex. Animals
Adenosine Triphosphate
• ATP
Chemical Energy
• Energy is stored within the chemical bonds in ATP.
STORING ENERGY:
• ADP: has two phosphate groups.
• ATP: has three phosphate groups.
• When a cell has energy available, it can store small
amounts of it by adding a phosphate group to ADP
molecules---making ATP.
RELEASING ENERGY
• Energy that is stored in ATP is released by breaking
the chemical bonds between the second and third
phosphates.
Using Biochemical Energy
• ATP powers pumps in cell membrane, protein
synthesis, responses to chemical signals at the cell
surface.
Review Questions
1.
What is the ultimate source of energy for plants?
2.
What is ATP and what is its role in the cell?
3.
Describe one cellular activity that uses the energy
released by ATP.
4.
How do autotrophs obtain energy? How do
heterotrophs obtain energy?
ACTIVITY
- Photosynthesis article.
- Mind Web from article.
Mind Map
• Read the article and create a mind map using the
information from the article.
8-2 Photosynthesis: An
Overview
Van Helmont’s Experiment
- To find out if plants grew by taking material out of
the soil.
- Determined the mass of a pot of dry soil and a small
seedling.
- He planted the seedling in the pot of soil.
- He watered it regularly.
- End of five years, the seedling, which by then had
grown into a small tree, had gained about 75kg.
- Mass of soil, however, was almost unchanged.
- He thought that the mass had come from the water.
- But where does the “carbon” come from in the
plant?
- He didn’t realize that carbon dioxide in the air made
a major contribution to the mass of his tree.
Priestley’s Experiment
• Took a candle, placed a glass jar over it.
• Watched as the flame gradually died out.
• Something in the air was necessary to keep a candle
flame burning.
• When that substance was used up, the candle went out.
• That substance was oxygen.
• If he placed a live sprig of mint under the jar and
allowed a few days to pass, the candle could be relighted and would remain lighted for a while.
• The mint plant had produced the substance required
for burning.
• It released oxygen.
• http://www.youtube.com/watch?v=fsa71gKvCaw
Jan Ingenhousz
• Showed that the effect observed by Priestley
occurred only when the plant was exposed to light.
• His and Priestley’s experiments showed that light is
necessary for plants to produce oxygen.
The Photosynthesis Equation
6CO2 + 6H2O ----- C6H12O6 + 6O2
Activity:
What would happen if clouds formed and light wasn’t
able to hit the earth.
Think about what happens first and then eventually.
At least one page in length.
Light and Pigments
Light and Pigments
• Pigments – light absorbing molecules, plants use to
gather sun’s energy.
• Chlorophyll – plants’ principal pigment.
• 2 types:
• Chlorophyll a
• Chlorophyll b
Absorbs light very well in blue-violet and red regions.
• Light energy is transferred directly to electrons in the
chlorophyll molecule, raising the energy levels of
these electrons.
• Electrons move down the electron transport chain.
Review
1. What did van Helmont, Priestley, and Ingenhousz
discover about plants?
2. Describe the process of photosynthesis, including
the reactants and products.
3. Why are light and chlorophyll needed for
photosynthesis?
4. Describe the relationship between chlorophyll and
the color of plants.
8-3 The Reactions of
Photosynthesis
• Thylakoids – saclike photosynthetic membranes.
• Grana – stacks of thylacoids. (granum)
• Photosystems – clusters of chlorophyll and other
pigments. Light-collecting units of the chloroplast.
• Stroma – region outside the thylakoid membranes.
Light rxn. Dark rxn.
Reactants of Light rxn.
From the Dark rxn.
- light
- NADP+
- water
- ADP + P
Reactants of Dark rxn.
- CO2
From the Light rxn.
- ATP
- NADPH
Light rxn. Dark rxn.
Products of Light rxn.
- ATP
- NADPH
- O2
Products of Dark rxn.
- Sugars
- NADP+
- ADP + P
Electron Carriers
• Sunlight excites electrons in chlorophyll.
• E- gain a lot of energy.
• Use carrier molecules to carry these e-.
Ex. NADP+ (nicotinamide adenine dinucleotide
phosphate)
- Holds 2 high-energy electrons along with a hydrogen
ion (H+). NADP+ ------NADPH
Light-Dependent Reactions
pg. 210
A: Light absorbed by photosystem II is used to break
up water molecules into energized electrons,
hydrogen ions (H+), and oxygen.
B: High-energy electrons from photosystem II move
through the electron transport chain to photosystem
I.
C: E- released by photosystem II are energized again in
photosystem I. Enzymes in the membrane use the eto form NADPH. NADPH is used to make sugar in
the Calvin Cycle.
D: The inside of the thylakoid membrane fills up with
positively charged hydrogen ions. This action makes
the outside of the thylakoid membrane negatively
charged and the inside positively charged.
E: As hydrogen ions pass through ATP synthase, their
energy is used to convert ADP into ATP.
ATP Synthase
• As it rotates it binds ADP and a phosphate group
together to produce ATP.
• Light-dependent rxn. Produces high-energy
electrons (NADPH) and ATP.
The Calvin Cycle
The Calvin Cycle
• Uses ATP and NADPH from the light-dependent
rxns. to produce high-energy sugars.
• Melvin Calvin, worked out the details of this cycle.
• LIGHT-INDEPENDENT RXN. Or DARK
REACTION
Process of Calvin Cycle
A: 6 Carbon dioxide molecules enter the cycle from the
atmosphere. The carbon dioxide molecules combine
with six 5-carbon molecules. The result is twelve 3carbon molecules.
B: The twelve 3-carbon molecules are then converted
into higher-energy forms. The energy for this
conversion comes from ATP and high-energy
electrons from NADPH.
C: Two of the twelve 3-carbon molecules are removed
from the cycle. The plant cell uses these molecules
to produce sugars, lipids, amino acids, and other
compounds needed for plant metabolism and
growth.
D: The remaining ten 3-carbon molecules are
converted back into six 5-carbon molecules. These
molecules combine with six new carbon dioxide
molecules to begin the next cycle.
• The Calvin cycle uses six molecules of carbon
dioxide to produce a single 6-carbon sugar molecule.