Intro to Photosynthesis - JC -22-23

Introduction to Photosynthesis

  • Life on Earth is dependent on solar energy.

Types of Photosynthetic Organisms

  • Examples include:

    • (a) Plants

    • (b) Multicellular algae

    • (c) Unicellular eukaryotes

    • (d) Cyanobacteria

    • (e) Purple sulfur bacteria

Oxidation and Reduction Processes

  • Key questions:

    • What is being oxidized?

    • What is being reduced?

  • Hint: Follow the hydrogen atoms; process involves multiple steps.

Sources for Photosynthesis

  • How do plants obtain:

    • Carbon dioxide (CO2)?

    • Water (H2O)?

  • Outcomes:

    • What happens to sugars produced?

    • What happens to oxygen (O2)?

Leaf Structure Overview

  • Internal structure includes:

    • Mesophyll

    • Stomata

    • Chloroplasts

    • Vascular veins

  • Stomata control gas exchange and water loss.

  • Guard cells regulate stomata based on turgor pressure.

  • Waxy coatings on leaves prevent water loss.

Chloroplast Structure

  • Key components:

    • Mesophyll cell

    • Stroma

    • Thylakoids (and lumen)

    • Granum (stack)

    • Outer and inner membranes

  • All photosynthesis reactions occur within chloroplasts.

Photosynthesis Steps

  • Overview and components involved in light reactions and Calvin cycle.

Light Reactions

  • Inputs:

    • Light

    • H2O

  • Outputs:

    • O2

    • ADP ➜ ATP

    • NADP+ ➜ NADPH

  • Functionality of light interaction with thylakoids.

Calvin Cycle

  • Processes carbon fixation and sugar production through:

    • Inputs like CO2 and H2O.

  • Outputs include sugars and energy carriers (ATP, NADPH).

Nature of Light

  • Light is composed of electromagnetic waves.

    • Defined by magnetic and electric fields.

    • Photons represent light energy traveling as waves.

Types of Electromagnetic Energy

  • Electromagnetic spectrum includes:

    • Gamma rays

    • X-rays

    • UV light

    • Visible light (380-750 nm)

    • Infrared

    • Micro and Radio waves

  • Wavelength impacts energy levels: shorter wavelengths are higher in energy.

Interaction of Light with Pigments

  • Light interactions occur within chloroplasts, involving:

    • Reflected light

    • Absorbed light

    • Transmitted light

  • Pigments determine colors and absorption characteristics.

    • Plants appear green due to specific pigment absorption spectrum.

Pigment Absorption and Action Spectrum

  • Different pigments absorb specific wavelengths:

    • Chlorophyll a, Chlorophyll b, Carotenoids

  • Importance of absorption spectra in understanding photosynthesis effectiveness.

Photosynthesis Mechanism

  • Pigments organized in clusters called photosystems facilitate energy transfer.

  • Electrons in pigments become excited by light energy, passing energy to neighboring molecules, essential for starting photosynthesis.

Detailed Structure of Photosynthesis

  • Two main processes outlined:

    1. Light Reactions

    2. Calvin Cycle

  • Each stage has specific roles and contributions to the overall process of photosynthesis.