Biology 1002B Chapter Notes - Chapter 1: Chlamydomonas Reinhardtii, Electromagnetic Spectrum, Conjugated System
3 May 2018
School
Department
Course
Professor
1.1 The Physical Nature of Light
Light serves two important functions for life
1. Source of energy
2. Provides info about the physical world
Chlamydomonas reinhardtii
• Clamy is a single-celled photosynthetic eukaryote
• Single large chloroplast that undergoes photosynthesis
• A light sensor called eyespot that gathers info about location and intensity of light source
• With info, chlamy can move towards or away from light to optimize light harvesting for
photosynthesis
1.1a What Is Light?
• Light: portion of the electromagnetic spectrum that humans can detect with eyes
o In physics, definition of light includes visible, UV, IR
• Electromagnetic spectrum: range of wavelengths of electromagnetic radiation
• Light is composed of a stream of photons (discrete particles or packets of energy)
• Relationship between wavelength of light and energy of photons is inverse
1.1b Light Interacts with Matter
• Absorption of light - energy of photon transferred to e- within a molecule
o E- is excited and moves from ground state to higher energy level
o Photon can only be absorbed if energy of photon matches amount of energy needed
to move e- from its ground state to a specific excited state
o If energies do not match, photon is transmitted through molecule or reflected
o Pigments: molecules that are very efficient at absorbing photons
• Common structure is having C atoms covalently bonded to each other with
alternating single and double bonds (conjugated system)
• Results in delocalization of e- thus e- are available to interact with photon
• Pigments absorb light at different wavelengths because difference in structure
• Reflection of light - energy of photon not transferred to e-
o If energies do not match, photon is transmitted through molecule or reflected
o A pigment's colour is the result of photons of light that it DOES NOT absorb
o Photons are reflected off pigment or transmitted through pigment to reach eyes
• Transmission of light through object is also possible if photons not absorbed
1.4 The Uniqueness of Light
Visible light is only a small portion of the total electromagnetic spectrum yet it is essential for
life on Earth
1. It is the most dominant form of electromagnetic radiation reaching Earth's surface
o Shorter wavelengths absorbed by ozone layer
o Longer wavelengths absorbed by water vapour and CO2
2. The energy that visible light contains is important for life
o Living things are made up of molecules held together by chemical bonds
o Shorter wavelengths contain too much energy to destroy bonds
find more resources at oneclass.com
find more resources at oneclass.com
