Photosynthesis and Chloroplast Function

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Questions and Answers

What is the primary function of chloroplasts in photosynthesis?

To synthesize proteins

To convert light energy into chemical energy (correct)

To store glucose

To absorb carbon dioxide

Where do the light-dependent reactions of photosynthesis occur?

In the outer membrane of chloroplasts

In the thylakoid membranes (correct)

In the stroma

In the cytoplasm

Which substance is produced as a byproduct of photolysis during the light-dependent reactions?

Glucose

Oxygen (correct)

ATP

Carbon dioxide

What role do ATP and NADPH play in photosynthesis?

They are energy carriers used in the light-independent reactions Signup and view all the answers

What is the significance of chlorophyll in the photosynthesis process?

It captures light energy and initiates electron transport Signup and view all the answers

Which component of chloroplast structure is responsible for housing the light-dependent reactions?

Grana Signup and view all the answers

What environmental condition is necessary for the light-dependent reactions to occur?

Presence of light Signup and view all the answers

What defines the thylakoid membranes in chloroplasts?

They contain chlorophyll and are the sites of light-dependent reactions. Signup and view all the answers

What is the primary role of RuBisCO in the Calvin Cycle?

To attach carbon dioxide to RuBP. Signup and view all the answers

Which of the following processes occurs during the Calvin Cycle?

Synthesis of glucose from G3P. Signup and view all the answers

In a photosynthesis experiment, what would be considered an independent variable?

The intensity of light provided to the plant. Signup and view all the answers

What is typically measured as a dependent variable in photosynthesis experiments?

The rate of oxygen production. Signup and view all the answers

Which compound is formed directly after RuBP is fixed with carbon dioxide?

3-Phosphoglycerate (3-PGA). Signup and view all the answers

What occurs to some G3P molecules in the Calvin Cycle?

They exit the cycle to form glucose. Signup and view all the answers

What does the stroma of the chloroplast contain?

Enzymes for the Calvin Cycle. Signup and view all the answers

Which of the following statements regarding light-independent reactions is true?

They convert carbon dioxide into organic compounds. Signup and view all the answers

Study Notes

Photosynthesis

Biochemical process where plants, algae and some bacteria convert light energy into chemical energy
Produces glucose and oxygen as byproducts
Foundation of life on Earth - powers most ecosystems and produces oxygen

Chloroplasts

Organelles where photosynthesis occurs
Contain chlorophyll - pigment that absorbs light (blue and red wavelengths)
Chlorophyll absorbs light energy and transfers it into a chemical form that the plant can use to make glucose.
Outer membrane, inner membrane and thylakoid membrane
Thylakoids are stacked into structures known as grana
Space around grana is called stroma
Light-dependent reactions occur in the thylakoid membranes
Light-independent reactions occur in the stroma

### Light-Dependent Reactions

First stage of photosynthesis and occurs in thylakoid membranes
Photons are absorbed by chlorophyll
Energy excites electrons which are passed along the electron transport chain
Water molecules are split (photolysis) releasing oxygen and provides the electrons to replace those lost by chlorophyll
Excited electrons are used to create ATP and NADPH, energy carriers for the next stage
These reactions require light

Light-Independent Reactions (Calvin Cycle)

Second stage of photosynthesis and occurs in the stroma
Doesn't require light directly
RuBisCO fixes carbon dioxide from the atmosphere by attaching it to a 5-carbon sugar, RuBP
The resulting compound is broken down into two molecules of 3-phosphoglycerate (3-PGA)
3-PGA converted into glyceraldehyde-3-phosphate (G3P), a 3-carbon sugar.
Some G3P molecules exit to form glucose and other carbohydrates, while others are recycled to regenerate RuBP

Scientific Investigation

Scientists often experiment with different variables to understand how photosynthesis works
Independent variable: factor you change or manipulate
Dependent variable: factor you measure in response to changes in the independent variable

Example of a Photosynthesis Experiment

Independent variable: would be light intensity
Dependent variable: would be rate of oxygen production
Collect data by measuring the amount of oxygen produced in a set period

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Description

Explore the intricate processes of photosynthesis, including the essential roles of chloroplasts and the stages of light-dependent and light-independent reactions. Understand how light energy is converted into chemical energy, powering ecosystems and sustaining life on Earth.