Ecosystem: Life Energy

Ecosystem: Life Energy

Lesson 1: Photosynthesis and Respiration

Fill in the Blanks

Multiple Select

Autotophic organisms require _____, _____, _____, _____, to make food.

• Sunlight

• Chlorophyll

• Water

• CO₂

• Sugar

Fill in the Blanks

Multiple Choice

A leaf has 3 layers. Among the three layers, which is considered the most important one?

• Lower epidermis

• Mesophyll

• Upper epidermis

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The Light Reaction of Photosynthesis

- is a series of steps that start with the trapping of light energy. It takes place only when light is present. The end products of the phase are the needed materials in the dark reaction simultaneously.

Light Reaction

• 1. Chlorophyll absorbs the units of light called PHOTONS.

• 2. The energy from the photons "excites" the electrons of the chlorophyll molecules causing the electrons to transfer to a higher energy level.

• 3. Electrons from a high energy level move to lower energy level. Electrons release energy. This energy is utilized to form ADENOSINE TRIPHOSPHATE (ATP).

• 4. Water molecules split into HYDROGEN and OXYGEN.

The Dark Reaction of Photosynthesis

-takes place even without light. Here, light is unnecessary anymore once the hydrogen atom had been formed.

Calvin Cycle

• The series of chemical events in the dark reactions forms a cycle known as the CALVIN CYCLE.

• In the stroma, carbon dioxide combines with a five carbon (5-C) sugar molecule and eventually forms two molecules of a three-carbon (3-C) acid. The 3-C acid is then reduced by NADPH (nicotinamide adenine dinucleotide phosphate hydrogen) with the use of the energy from ATP into two molecules of a 3-C sugar.

Calvin Cycle

• As a result, of dark reactions, the energy is previously stored in ATP and NADPH is now in the sugar molecules. The dark reactions complete the transformation of light energy to chemical energy.

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Activity 1

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