Cell Energy Adapted from A. Anguiano & J. Zhen All organisms need energy to live.
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Transcript of Cell Energy Adapted from A. Anguiano & J. Zhen All organisms need energy to live.
Cell Energy
Adapted from A. Anguiano & J. Zhen
All organisms need energy to live.
Autotrophs Organisms that make their own food.They use sunlight to produce food.
Example: Plants
Autotrophs
Heterotrophs Organisms that get energy from the food they eat.
Examples: animals
Heterotrophs
Photosynthesis …. Process by which plants
convert water and carbon dioxide to high-energy carbohydrates (glucose).
Plants = “autotrophs” (make their own food)
Carbohydrates are: Glucose, starch and cellulose
What are examples of carbohydrates?
Glucose is used to store energy (ATP)
1 Glucose gives 36 ATP
36 ATP
6CO2 + 6H2O C6H12O6 + 6O2
PRODUCTSPRODUCTSREACTANTSREACTANTS
Reactants: are what goes into a chemical reaction
Products: Are what is produced at the end of the chemical reaction.
Photosynthesis Equation
light
Photosynthesis Equation
6CO2 + 6H2O C6H12O6 + 6O2
Carbon Dioxide
Water
Glucose
Oxygen
light
Light
6 CO2
6 H2O
6 O2
C6H12O6
Where Photosynthesis
happens
Chloroplast Site of photosynthesis Contains chlorophyll, a
pigment that absorbs energy from sunlight
Structure of a chloroplast:
1) Double membrane2) Thylakoid: contain chlorophyll; where light rxn takes place3) Granum: stacks of thylakoids4) Photosystems: light-collecting units of the chloroplast (a
cluster of chlorophyll in the thylakoid)5) Stroma: space outside the thlakoid membrane
3
4
1
2
5
Plants plant cells Chloroplast Chlorophyll a
Chlorophyll is a pigment* found in the Chloroplast.
This is what gives it the green color.
*A pigment is a molecule that absorbs light.
The sun shines white light.
White light is made up of a rainbow of colors.
SUN
Each drop of water acts like a prism.
Why do plants look green? Plants look green because
they contain chlorophyll αα which reflects green light.
Photosynthesis
Plant Pigments
Main pigment = chlorophyll a (absorbs blue/red light reflects green/yellow)
Photosynthesis
Photosynthesis
Plant Pigments
Accessory pigments = chlorophyll b (absorbs
blue/red light reflects green/yellow
carotene(absorbs blue/green light reflects yellow/orange)
Photosynthesis is divided into 2 parts:
1. Light Dependent reactions
2. Dark reaction (Calvin Cycle) (Light InIndependent ~ no Light is needed)
Light Dependent Reactions
Light Independent Reactions
Two Reactions Occurs in 2 stages:
1) Light reaction (requires sunlight)
2) Dark reaction (does not require sunlight; also called the Calvin Cycle)
1. Light Dependent Reactions- Requires sunlight; occurs in
thylakoids
Sunlight
Electron excited
Chlorophyll ATP, NADPH
1) Chlorophyll in each thylakoid absorbs energy (in the form of photons) from sunlight
2) The energy is transferred to electrons and they leave the chlorophyll
3) Water (H2O) gets split. Electrons from water replace the electrons that chlorophyll lost and Oxygen (O2) is released as a waste product
4) Thylakoid uses the energy to make two products to be used in Dark rxn later:
- ATP (Adenosine Triphosphate) = energy-carrying molecule- NADPH = a temporary energy storage molecule
Reactant
Product
Energy carrying molecules
NADPH: molecule that carries electrons
NADPH holds 2 electrons
NADP+ is ready to accept 2 electrons & H+
Photosynthesis
Chemical Energy and ATP
Storing Energy ADP has two phosphate groups instead of three. A cell can store small amounts of energy by adding a
phosphate group to ADP.
ADPATP
Energy
Energy
Partiallycharged battery
Fullycharged battery
+
Adenosine Diphosphate (ADP) + Phosphate
Adenosine Triphosphate (ATP)
Chemical Energy and ATP
Releasing Energy Energy stored in ATP is released by breaking the
chemical bond between the second and third phosphates.
P
ADP
2 Phosphate groups
Light-Dependent Reactions
Photosystem II
Photosynthesis begins when pigments in photosystem II absorb light, increasing their energy level.
Photosystem II
These high-energy electrons are passed on to the electron transport chain.
Electroncarriers
High-energy electron
Photosystem II
2H2O
Enzymes on the thylakoid membrane break water molecules into:
Electroncarriers
High-energy electron
Photosystem II
2H2O
hydrogen ions oxygen atoms energized electrons
+ O2
Electroncarriers
High-energy electron
Photosystem II
2H2O
+ O2
The energized electrons from water replace the high-energy electrons that chlorophyll lost to the electron transport chain.
High-energy electron
Photosystem II
2H2O
As plants remove electrons from water, oxygen is left behind and is released into the air.
+ O2
High-energy electron
Photosystem II
2H2O
The hydrogen ions left behind when water is broken apart are released inside the thylakoid membrane.
+ O2
High-energy electron
Photosystem II
2H2O
Energy from the electrons is used to transport H+ ions from the stroma into the inner thylakoid space.
+ O2
Photosystem II
2H2O
High-energy electrons move through the electron transport chain from photosystem II to photosystem I.
+ O2
Photosystem I
2H2O
Pigments in photosystem I use energy from light to re-energize the electrons.
+ O2
Photosystem I
2H2O
NADP+ then picks up these high-energy electrons, along with H+ ions, and becomes NADPH.
+ O2
2 NADP+
2 NADPH2
2H2O
As electrons are passed from chlorophyll to NADP+, more H+ ions are pumped across the membrane.
+ O2
2 NADP+
2 NADPH2
2H2O
Soon, the inside of the membrane fills up with positively charged hydrogen ions, which makes the outside of the membrane negatively charged.
+ O2
2 NADP+
2 NADPH2
2H2O
The difference in charges across the membrane provides the energy to make ATP
+ O2
2 NADP+
2 NADPH2
2H2O
H+ ions cannot cross the membrane directly.
+ O2
ATP synthase
2 NADP+
2 NADPH2
2H2O
The cell membrane contains a protein called ATP synthase that allows H+ ions to pass through it
+ O2
ATP synthase
2 NADP+
2 NADPH2
2H2O
As H+ ions pass through ATP synthase, the protein rotates.
+ O2
ATP synthase
2 NADP+
2 NADPH2
2H2O
As it rotates, ATP synthase binds ADP and a phosphate group together to produce ATP.
+ O2
2 NADP+
2 NADPH2
ATP synthase
ADP
2H2O
Because of this system, light-dependent electron transport produces not only high-energy electrons but ATP as well.
+ O2
ATP synthase
ADP2 NADP+
2 NADPH2
2. Dark Reactions (Calvin Cycle)- Does not require
sunlight; occurs in stroma (CO2 enters)
Light Dark
NADPH Used to form glucose
ATP stored or used elsewhere
1) ATP & NADPH from Light rxn are used to take carbon atoms from CO2 to make glucose
2) It takes 6 turns of Calvin cycle to fix CO2 (1 carbon) into C6H12O6 (6 carbons)
ReactantProduct
Six carbon dioxide molecules enter the cycle from the atmosphere and combine with six 5-carbon molecules.
CO2 Enters the Cycle
The result is twelve 3-carbon molecules, which are then converted into higher-energy forms.
The energy for this conversion comes from ATP and high-energy electrons from NADPH.
12 NADPH
12
12 ADP
12 NADP+
Energy Input
Two of twelve 3-carbon molecules are removed from the cycle.
Energy Input
12 NADPH
12
12 ADP
12 NADP+
The molecules are used to produce sugars, lipids, amino acids and other compounds.
12 NADPH
12
12 ADP
12 NADP+
6-Carbon sugar produced
Sugars and other compounds
The 10 remaining 3-carbon molecules are converted back into six 5-carbon molecules, which are used to begin the next cycle.
12 NADPH
12
12 ADP
12 NADP+
5-Carbon MoleculesRegenerated
Sugars and other compounds
6
6 ADP