Photosynthesis Overview and Chloroplast Structure
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Questions and Answers

What is the primary role of glucose produced during photosynthesis?

  • It is used directly for photosynthesis.
  • It serves as a source of energy and can be stored. (correct)
  • It is solely released into the atmosphere as oxygen.
  • It replaces the need for water in plant cells.

Which statement accurately describes autotrophs?

  • They are organisms that consume other organisms for energy.
  • They rely entirely on decomposition for energy.
  • They can only derive energy from sunlight directly.
  • They produce their own food and store energy compounds. (correct)

In which part of the plant does photosynthesis primarily occur?

  • In the roots.
  • In the flowers.
  • In the stems.
  • In the chloroplasts. (correct)

What is the function of light-dependent reactions in photosynthesis?

<p>To capture light energy and convert it into chemical energy. (C)</p> Signup and view all the answers

What is the difference between light-dependent and light-independent reactions?

<p>Light-dependent reactions produce ATP, while light-independent reactions use ATP. (D)</p> Signup and view all the answers

What is the primary function of chlorophyll in the chloroplast?

<p>To absorb light energy for photosynthesis (A)</p> Signup and view all the answers

Which statement accurately describes the function of ATP in photosynthesis?

<p>ATP releases energy when a phosphate bond is broken (C)</p> Signup and view all the answers

What is the end product of the light-dependent reactions that exits the chloroplast?

<p>Oxygen (B)</p> Signup and view all the answers

Which of the following best describes the structure known as the granum?

<p>An orderly stack of thylakoids (C)</p> Signup and view all the answers

Which type of plant maintains its leaves year-round and has needle-like leaf structures?

<p>Coniferous Forest plants (B)</p> Signup and view all the answers

At what temperature do plants typically stop utilizing photosynthesis?

<p>0°C (A), 32°F (C)</p> Signup and view all the answers

How does NADP+ function in photosynthesis?

<p>It carries electrons and hydrogen ions (B)</p> Signup and view all the answers

Which part of the chloroplast is a jelly-like fluid that supports the thylakoids?

<p>Stroma (C)</p> Signup and view all the answers

Flashcards

Photosynthesis

The process by which plants, algae, and some bacteria convert light energy from the sun into chemical energy stored in glucose (sugar). This process involves using carbon dioxide (CO2) from the air and water (H2O) from the soil.

Autotrophs

Organisms that can produce their own food (glucose) through photosynthesis. They are the base of all food chains.

Heterotrophs

Organisms that obtain their food by consuming other organisms. They cannot make their own food.

Chlorophyll

The green pigment found in plants that absorbs light energy for photosynthesis. It is responsible for the green color of plants.

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Calvin Cycle

The light-independent reactions of photosynthesis, where carbon dioxide is used to produce glucose. This process is driven by the energy stored in ATP from the light-dependent reactions.

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Chloroplast Structure

The chloroplast is a membrane-bound organelle found in plant cells responsible for photosynthesis. It has three key parts: the outer membrane, stroma, and thylakoids. The outer membrane encloses the entire organelle. The stroma is a jelly-like fluid that fills the space between the thylakoids and contains enzymes for photosynthesis. Thylakoids are flattened membrane-bound sacs that contain photosynthetic pigments like chlorophyll.

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Thylakoid Stack

Thylakoids are flattened membrane-bound sacs within chloroplasts. A stack of thylakoids is called a granum (plural: grana). These stacks are the sites where light-dependent reactions of photosynthesis take place.

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Light-Dependent Reaction (LDR)

The first stage of photosynthesis, where light energy is absorbed by chlorophyll, which is then used to split water molecules. This produces oxygen as a waste product, and also generates ATP (energy) and NADPH (electron carrier) for the next stage.

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Light-Independent Reaction (LIR)

The second stage of photosynthesis, also known as the Calvin Cycle. Here, the energy (ATP) and electrons (NADPH) produced in the LDR are used to convert carbon dioxide into glucose (sugar).

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ATP vs. ADP

ATP is the primary energy currency of cells. It consists of an adenosine molecule attached to three phosphate groups. ADP is similar, but has only two phosphate groups. Breaking the bond of one phosphate group in ATP releases energy, converting it to ADP. Conversely, adding a phosphate group back to ADP stores energy, creating ATP.

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NADP+ vs. NADPH

NADP+ is an electron carrier that plays a crucial role in photosynthesis. It picks up electrons and hydrogen ions, becoming NADPH. In the LIR, NADPH releases these electrons and hydrogen ions, returning to its original form (NADP+).

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Endosymbiont Theory

This theory proposes that chloroplasts, like mitochondria, were originally free-living prokaryotic cells that were engulfed by larger cells and formed a symbiotic relationship. Over time, they evolved to become integrated parts of the host cells.

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Study Notes

Photosynthesis Overview

  • Photosynthesis is the process by which plants convert light energy into chemical energy (glucose).
  • The overall reaction is: CO2 + H2O + light energy → glucose + O2.
  • CO2 comes from the atmosphere, and H2O from the soil.
  • Plants use glucose for energy (ATP) or storage.
  • Plants release O2 as a waste product.
  • Plants are autotrophs, meaning they make their own food; they form the base of all food chains/webs.
  • Heterotrophs consume other organisms for energy.

Chloroplast Structure

  • Photosynthesis occurs in chloroplasts.
  • Chloroplasts contain thylakoids (membrane-bound sacs with photosynthetic pigment chlorophyll) stacked into grana.
  • The stroma is the fluid surrounding the thylakoids.
  • Chloroplasts have their own DNA, supporting the endosymbiotic theory.

Light and Photosynthetic Pigments

  • Light energy comes from the sun, mimicking it with grow lamps (red and blue light).
  • Visible light has different wavelengths, corresponding to colors in the ROYGBIV spectrum (red, orange, yellow, green, blue, indigo, violet).
  • Plants primarily absorb red and blue light.
  • Green light is not absorbed and reflected, which is why plants appear green.
  • Light can be reflected, refracted, or absorbed.

Photosynthesis Stages

  • Photosynthesis is a two-stage process: light-dependent reactions and light-independent reactions (Calvin Cycle).
  • Light-dependent reactions require light energy, split water, and generate ATP and NADPH.
  • Light-independent reactions use ATP and NADPH to synthesize glucose.
  • These stages are interdependent.

ATP and ADP

  • ATP (adenosine triphosphate) stores energy.
  • ADP (adenosine diphosphate) is created when ATP releases energy.
  • ATP is essential for many cellular processes, including active transport.

Types of Plants

  • Plants in deciduous forests drop leaves to conserve energy when sunlight decreases and water freezes.
  • Broad, flat leaves increase sunlight absorption surface area.
  • Coniferous forest plants, including pines, keep their leaves year-round.
  • Needle-like leaves increase the number of leaves to compensate for the lack of broad surface area.
  • The temperature at which plants stop photosynthesis is 0°C/32°F.

Light-Dependent Reactions (LDR)

  • LDR requires light energy
  • Splits water into hydrogen ions (2H+) and electrons
  • Produces O2 as a byproduct.
  • NADP+ + H+ + 2e- → NADPH
  • The electrons and hydrogen ions are sent to the Calvin Cycle.

Light-Independent Reactions (LIR)/ Calvin Cycle

  • LIR (Calvin cycle) does NOT require light energy to run, but uses ATP.
  • NADPH provides the electrons and hydrogen ions.
  • ATP provides energy.
  • Results in synthesis of glucose.
  • The ADP and NADP+ produced in this process are sent back to the LDR.

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Description

Explore the essential processes of photosynthesis and the structural components of chloroplasts. Understand how plants convert light energy into chemical energy and the role of various pigments in this vital process. This quiz will test your knowledge of plant biology and energy transformation.

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