BSC 314 Lecture Notes - Lecture 27: Oxaloacetic Acid, Disaccharide, Hexose
27 Jun 2018
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Most Important Process in the World
Photosynthesis is the process by which organisms convert light energy into chemical
energy. The most common and critical type of photosynthesis takes place in chlorophyll ‐
containing plants, algae, and cyanobacteria. These organisms capture radiant energy
of the sun and, by utilizing carbon dioxide and water, convert it to chemical energy
stored in molecules of carbohydrates. Oxygen and water are released as by products. ‐
The generalized equation is:
The other photosynthesizers are green and purple bacteria, which convert light energy
to chemical energy, but use other raw materials and pigments in an oxygen free ‐
( anaerobic) environment to make carbohydrates. Different by products result.‐
A generalized equation for all kinds of photosynthesis therefore is:
Photosynthesis is the single most important process on earth, for without it neither
plants nor animals (including humans) could survive. The energy stored in organic
molecules by photosynthesizers is the fuel of life for most living things and the oxygen
released during photosynthesis makes cellular respiration—and therefore life—possible
on earth.
Overview of Eukaryote Photosynthesis
Photosynthesis in plants and algae takes place in chloroplasts and entails two steps:
1. Energy transferring (energy transduction) reactions‐ (commonly called the light‐
dependent or light reactions)
2. Carbon fixation reactions (sometimes inappropriately called the dark reactions)
Step one: Energy transfer
The energy transferring reactions are photochemical processes that take place in two
physically separate but chemically linked photosystems: Photosystem I (PsI) and Photosystem II
(PsII). Photosystems are pigment molecules that capture energy from the sun and are
arranged in the thylakoid membranes of the chloroplasts. The chlorophyll and other
pigments of both photosystems absorb light energy, most of which is stored temporarily in
energy‐rich chemical bonds of ATP (adenosine triphosphate) and the electron
carrier NADPH (reduced nicotinamide adenine dinucleotide phosphate). ATP and NADPH
supply the energy for the resultant carbon fixation reactions of step two. Oxygen (O 2) is a
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Document Summary
Photosynthesis is the process by which organisms convert light energy into chemical energy. The most common and critical type of photosynthesis takes place in chlorophyll containing plants, algae, and cyanobacteria. These organisms capture radiant energy of the sun and, by utilizing carbon dioxide and water, convert it to chemical energy stored in molecules of carbohydrates. Oxygen and water are released as by products. The other photosynthesizers are green and purple bacteria, which convert light energy to chemical energy, but use other raw materials and pigments in an oxygen free ( anaerobic) environment to make carbohydrates. A generalized equation for all kinds of photosynthesis therefore is: Photosynthesis is the single most important process on earth, for without it neither plants nor animals (including humans) could survive. The energy stored in organic molecules by photosynthesizers is the fuel of life for most living things and the oxygen released during photosynthesis makes cellular respiration and therefore life possible on earth.
