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Photosynthesis and Cellular Respiration

+Energy

Energy that living things gain from eating comes indirectly from the sun.

Plants receive this energy directly, while we receive the energy indirectly.

This energy makes organic compounds found in our food.

+Flow of Energy

+Autotrophs

Organisms that use energy from sunlight to make organic compounds

Most are photosyntheticEx: Plants

Some do not have access to sunlight, and use chemical energy insteadEx: bacteria in extreme environments

+Photosynthesis

The process by which light energy is converted to chemical energy

+Heterotrophs

Organisms that must get energy from food

Humans and other animals

Go through cellular respiration processes for energy

+Cellular Respiration

Releases energy from food to make ATP

Energy released gradually through chemical reactions

ATP is a result of these reactions

ATP goes wherever it is needed in the cells

+ATP

ATP (Adenosine Triphosphate) goes to the areas that need energy in the cell

A phosphate group breaks off to release the energy needed and forms ADP.

ATP ADP + P + Energy

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Let’s Look at Photosynthesis and

Cellular Respiration a little closer!

+Photosynthesis

All foods that we eat eventually lead back to plants.

These plants go through photosynthesis to get their energy.

Ex: Hamburger Beef comes from cow that ate grass.

+Photosynthesis

Photosynthesis occurs in chloroplasts of plant cells and cell membrane of bacteria.

3CO2 + 3H2O C3H6O3 + 3O2

+Three Stages of Photosynthesis

1.) Energy is captured from sunlight

2.) Light energy is converted to chemical energy (stored in ATP and NADPH)

3.) Chemical energy in ATP and NADPH power the formation of organic compounds

Steps 1 & 2 are light-dependent

NADPH is an energy carrier molecule

+Stage 1: Energy is Captured From Sunlight

When sun shines on us, there are several types of radiation hitting us at different wavelengths. We can only see visible light and sunlight contains all of the wavelengths of visible light.

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+Stage 1: Energy is Captured From Sunlight

How do we see light?

+Stage 1: Energy is Captured From Sunlight

We see light through light-absorbing substances called pigments. These absorb and reflect certain wavelengths.

These pigments are held in disk-shaped thylakoids in chloroplasts. These pigments are held in clusters.

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+Two Types of Pigments to Know

ChlorophyllReflects green and yellow light so we see leaves as green.

CarotenoidsReflects yellow and red light so we see leaves as yellow and orange in fall.

+Stage 1: Energy is Captured From Sunlight Light strikes thylakoid

Energy transferred to electrons in pigments

Electrons now “excited” and jump to higher energy level

These electrons used to power Stage 2

Electrons used now replaced through water molecules

This forms oxygen gas (O2)

+Stage 2: Light Energy is Converted to Chemical Energy

The excited electrons from Stage 1 jump through molecules along the thylakoid membrane.

Like a basketball being passed down a line of people

This is known as an electron transport chainOne chain helps make ATPOne chain helps make NADPH

+Electron Transport Chain: ATP

Excited electrons move through protein

Electrons lose energy, energy used to pump in H+ ions

Eventually these ions diffuse out of the thylakoid through a carrier protein

This protein causes ADP to add a phosphate group and it becomes ATP

+Electron Transport Chain: NADPH

Excited electrons combine with hydrogen ions and NADP+

Forms NADPH

+Stage 3: Energy Stored in Organic Compounds

Carbon dioxide fixation: transfer of carbon dioxide to organic compounds

“dark reaction” or light-independent

Most common method of carbon dioxide fixation is the Calvin Cycle

+Calvin Cycle

1.) Each carbon dioxide molecule is added to a five-carbon compound.

2.) Each of the three resulting six-carbon compounds is unstable and immediately splits, forming a total of six three-carbon compounds.

3.) One of the resulting three-carbon sugars is used to make organic compounds that the organism uses for energy.

4.) The five other three-carbon sugars are used to regenerate the five-carbon compound that began the cycle.

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+Factors that Affect Photosynthesis

Light Rate of Photosynthesis increases as light intensity increases

Carbon Dioxide Concentration Same as light

Temperature Enzymes assist reactions and have to stay within certain

temperature range