Photosynthesis Lecture Notes

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Questions and Answers

What is CAM in plants?

Crassulacean acid metabolism

CAM plants open their stomata during the day.

False

Which of the following plants utilize CAM? (Select all that apply)

Cacti (correct)

Rose

Pineapples (correct)

Lily

What factors can affect the rate of photosynthesis?

Water, temperature, light intensity Signup and view all the answers

At what temperature range do enzymes work best during photosynthesis?

0°C to 35°C Signup and view all the answers

Light intensity does not affect the rate of photosynthesis.

False Signup and view all the answers

Water is required in the ______ dependent reactions.

light Signup and view all the answers

What happens to photosynthesis at very low or very high temperatures?

Photosynthesis may stop entirely. Signup and view all the answers

What are autotrophs?

Organisms that can make their own food using light energy from the sun. Signup and view all the answers

What do heterotrophs need to do to obtain energy?

Heterotrophs must consume food. Signup and view all the answers

What is the energy source for autotrophs?

Sunlight Signup and view all the answers

What is the main product of photosynthesis?

Glucose. Signup and view all the answers

The main pigment involved in photosynthesis is ______.

chlorophyll Signup and view all the answers

Chlorophyll reflects green light.

True Signup and view all the answers

Which of the following is a chemical compound used to store energy in cells?

ATP Signup and view all the answers

ADP is considered to be ______ in energy.

energy poor Signup and view all the answers

Match the following components with their functions in photosynthesis:

Chlorophyll = Absorbs sunlight Stomata = Gas exchange Thylakoids = Site of light-dependent reactions Stroma = Site of Calvin cycle Signup and view all the answers

What gas is released as a byproduct of photosynthesis?

Oxygen Signup and view all the answers

What happens to ADP when a phosphate group is added?

It becomes ATP Signup and view all the answers

The Calvin Cycle takes place in the thylakoids.

False Signup and view all the answers

What is NADPH used for in photosynthesis?

To carry high-energy electrons to chemical reactions. Signup and view all the answers

Photosynthesis utilizes the equation ______.

6CO2 + 6H2O + sunlight -> C6H12O6 + 6O2 Signup and view all the answers

What are the two main types of chlorophyll?

Chlorophyll-a and Chlorophyll-b. Signup and view all the answers

What is the main function of the stomata in leaves?

To allow gas exchange. Signup and view all the answers

What do C4 plants have that allows them to maintain photosynthesis while conserving water?

Oxaloacetic acid. Signup and view all the answers

Study Notes

Autotrophs and Heterotrophs

Autotrophs produce their own food using sunlight, primarily converting it into glucose.
Examples of autotrophs include green plants, certain bacteria, and some protists.
Heterotrophs, including all animals and fungi, cannot make their own food; they must consume other organisms.
Photosynthesis is the process by which plants convert sunlight into chemical energy stored in glucose, with oxygen released as a by-product.

Chemical Energy and ATP

Living cells store energy in chemical compounds, primarily ATP (Adenosine Triphosphate) and ADP (Adenosine Diphosphate).
ATP is an energy-rich molecule, while ADP is considered energy-poor.
ATP consists of adenine, ribose (a sugar), and three phosphate groups; removing a phosphate releases energy for cellular activities.
Cells regenerate ATP continuously, with muscle cells producing up to 10 million ATP molecules per second.

Overview of Photosynthesis

Photosynthesis converts water and carbon dioxide into high-energy sugar molecules and oxygen using sunlight.
The general equation for photosynthesis: 6CO2 + 6H2O + sunlight → C6H12O6 + 6O2.
Plants absorb carbon dioxide from the atmosphere and water from the soil to drive this process.

Light and Pigments

Light energy from the sun, along with chlorophyll, is essential for photosynthesis.
The electromagnetic spectrum includes visible light, which drives photosynthesis; colors include red, orange, yellow, green, blue, indigo, and violet.
Chlorophyll absorbs most visible light wavelengths except green, making plants appear green.

Photosynthetic Membranes

Leaves are the primary site for photosynthesis, housing approximately half a million chloroplasts per square millimeter.
The leaf structure includes cuticles to prevent water loss, mesophyll cells for photosynthesis, stomata for gas exchange, and vascular bundles for nutrient transport.
Chloroplasts consist of outer membranes, thylakoids (where light reactions occur), and stroma (where the Calvin cycle occurs).

Electron Carriers

High-energy electrons generated by chlorophyll in sunlight-driven reactions need transport via electron carriers.
NADP+ serves as a key electron carrier, converting to NADPH by accepting high-energy electrons and a hydrogen ion.
NADPH is utilized in the Calvin cycle to synthesize glucose.

Stages of Photosynthesis

Photosynthesis occurs in two main stages: Light Dependent Reactions and Light Independent Reactions (Calvin Cycle).
Light Dependent Reactions occur in thylakoids, creating ATP and NADPH, while the Calvin Cycle takes place in the stroma to produce glucose.

The Light Dependent Reactions

Photosystems I and II are integral to the light reactions, absorbing light and energizing electrons.
Water molecules are split into electrons, hydrogen ions, and oxygen (waste product) to replenish lost electrons.
ATP synthase uses proton flow to generate ATP during these reactions.

The Calvin Cycle

Occurs in the stroma, utilizing carbon dioxide, ATP, and NADPH to produce glucose through a series of reactions.
Involves carbon fixation using RuBP and converting PGA to PGAL, with PGAL either forming glucose or regenerating RuBP.

Alternative Pathways in Photosynthesis

Plants face dehydration risks; stomata must open for carbon intake, leading to water loss.
C4 plants (e.g., corn, sugarcane) convert carbon dioxide to oxaloacetic acid for later use, maintaining photosynthesis while conserving water.
CAM plants (e.g., cacti, pineapples) absorb carbon dioxide at night and close stomata during the day to mitigate water loss.

Factors Affecting the Rate of Photosynthesis

Water shortages can hinder photosynthesis; plants have a waxy cuticle to reduce water loss.
Optimal temperature range for photosynthesis is between 0°C and 35°C; extreme temperatures can damage enzymes or halt the process.
Increasing light intensity enhances photosynthesis rates, reflecting its dependency on sunlight.

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Description

This quiz explores the concepts of autotrophs and heterotrophs in the process of photosynthesis. It details how autotrophs create their own food using sunlight while heterotrophs rely on other organisms for sustenance. Understanding these energy flows is crucial for appreciating ecosystem dynamics.