5/15/2017 1 Cellular Energy and Photosynthesis Cellular Energy Energy is the ability to do work. Living things use Chemical Energy Cells use chemical energy to do work. Cell growth Reproduction Active transport Movement Chemical reactions The sun is the source of energy for living things • Energy enters most ecosystems as sunlight and leaves as heat. • Photosynthesis: a biochemical pathway that converts solar energy into the chemical energy stored in the bonds of organic molecules. • One important product of photosynthesis is glucose.
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5/15/2017
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Cellular Energy and Photosynthesis
Cellular Energy
Energy is the ability to do work.
Living things use Chemical Energy
Cells use chemical energy to do work.Cell growth
Reproduction
Active transport
Movement
Chemical reactions
The sun is the source of energy for living things
• Energy enters most ecosystems as sunlight and leaves as heat.
• Photosynthesis: a biochemical pathway that converts solar energy into the chemical energy stored in the bonds of organic molecules.
• One important product of photosynthesis is glucose.
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Energy in glucose is converted to energy in ATP
Cellular Respiration is the biochemical pathway that breaks down glucose and uses the energy to make ATP.
ATP is the basic energy source used by all types of cells.
Energy Cycling in Ecosystems
ATP
ATP = adenosine triphosphate. This is the compound that directly supplies the energy to do cellular work.
How ATP works
The release of one of the phosphate groups makes energy available to do cellular work.
ATP energizes other molecules by transferring one phosphate group.Example: for muscle contraction
ATP transfers one phosphate group to a special motor protein in the muscle cell.
Because of the ATP, the protein changes it’s shape and causes the muscle cells to contract.
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ATP and Glucose
Most cells have only a small amount of ATP (enough to last for a few seconds of activity)
ATP is very efficient at transferring energy but it is not very good at storing energy over long periods of time.
It is more efficient for cells to store energy in a molecule such as glucose.
A glucose molecule has more than 90 times the chemical energy of a molecule of ATP
ATP AS A CHARGED BATTERY
When a phosphate group is added to a ADP molecule, ATP is produced. ADP contains some energy, but not as much as ATP. In this way, ADP is like a partially charged battery that can be fully charged by the addition of a phosphate group.
• Where is the energy stored in the molecule of ATP?
• How would you change the figure to show a molecule of ADP?
Autotrophs & Heterotrophs
Autotrophs: organisms able to use light energy from the sun to make their own food.
Examples: plants, algae, and some bacteria.
Hetertrophs: organisms that obtain food by consuming other living things.
Examples: fungi, animals
Both autotrophs & heterotrophs must convert the energy that is stored in the bonds of their food into ATP.
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How Do Organisms Use Energy?
Characteristic of living organisms:– Obtain and use energy
Types of Organisms– Autotroph
An organism - capture energy from sunlight or chemicals and use it to produce its own food from inorganic compounds
A.k.a. producer– Heterotroph
An organism that obtains energy from the food it consumes A.k.a. consumer
What is Photosynthesis?
The process of photosynthesis is a chemical reaction
It is the most important chemical reaction on our planet!!
Life on Earth is made possible by the SUN and PHOTOSYNTHESIS
Photosynthetic Organisms
In blue-green algae (cyanobacteria) no special organelles
In protists (e.g., euglena) and plants: P-S occurs in Chloroplasts
P-S
plantsSome
protists;cyano-
bacteria
Light
Light energy must be captured We see “white” light from the sun
– Mixture of different wavelengths
– We see the “visible spectrum”
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Pigment
Pigment: light absorbing molecules which allow plants to gather energy from the sun absorbs some wavelengths of light but reflects others
to produce color Pigment: Chlorophyll
Two types: Chlorophyll a and chlorophyll b Plants are green because the green wavelength is
reflected, not absorbed.
Chlorophyll Absorption Spectrum
Chlorophyll absorbs blue-violet & red light best
Chloroplasts Photosynthesis occurs in plant organelles called
chloroplasts Thylakoids: saclike photosynthetic membranes in
chloroplasts Grana: stacks of thylakoids
How is Energy Collected?
Light is a form of energy– Other forms: heat and sound
We need chloroplasts to convert light energy to energy that organisms can use– Chemical Energy
During photosynthesis light energy is transferred to electrons
These electrons are carried by an electron carrier (NADP+) to other molecules
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Carrying Electrons
NADP+ is a carrier molecule
Transports pairs of electrons
Describe Photosynthesis
Method of converting sun energy into chemical energy usable by cells
Uses sunlight to convert H2O and CO2into sugars and O2
Energy is stored as sugar
Plants need light energy, CO2, and H2O
Photosynthesis Reactions
(requires energy, like driving a car. Fuel = light)
Light-Dependent Reactions
Photosynthesis has many steps
Light-dependent reactions require light
Happen in thylakoid membrane
Oxygen produced from water
Energy from light stored in ATP and NADPH
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Light-Independent Reactions
Light-independent reactions does not require light
Carbon dioxide used to make glucose
Glucose holds energy Happens in Stroma
Why do we need Plants and Other Photosynthetic organisms?
Here are just 2 reasons (there are others):
Without P-S organisms, we’d suffocate : WHY?- The oxygen released during photosynthesis is necessary for all living things.
Without P-S organisms, we’d starve : WHY?- We cannot make our own food (glucose, energy), we must get our food from plants.- Plants are the first step in the food chain.
So: Animals and plants are interdependent
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