Photosynthesis Vocabulary Terms and Definitions

Photosynthesis is the process by which plants and certain other organisms make glucose from carbon dioxide and water. In order to understand and remember how photosynthesis works, it helps to know the terminology. Use this list of photosynthesis terms and definitions for review or to make flashcards to help you learn important photosynthesis concepts.

ADP - ADP stands for adenosine diphosphate, a product of the Calvin cycle that is used in the light-dependent reactions.

ATP - ATP stands for adenosine triphosphate. ATP is a major energy molecule in cells. ATP and NADPH are products of the light-dependent reactions in plants. ATP is used in reduction and regeneration of RuBP.

autotrophs - Autotrophs are photosynthetic organisms which convert light energy into the chemical energy they need to develop, grow, and reproduce.

Calvin cycle - The Calvin cycle is the name given to the set of chemical reactions of photosynthesis that does not necessarily require light. The Calvin cycle takes place in the stroma of the chloroplast. It involves the fixing of carbon dioxide into glucose using NADPH and ATP.

carbon dioxide (CO₂) - Carbon dioxide is a gas naturally found in the atmosphere that is a reactant for the Calvin Cycle.

carbon fixation - ATP and NADPH are used to fix CO₂ into carbohydrates. Carbon fixation takes place in the chloroplast stroma. 

chemical equation of photosynthesis - 6 CO₂ + 6 H₂O → C₆H₁₂O₆ + 6 O₂

chlorophyll - Chlorophyll is the primary pigment used in photosynthesis. Plants contain two main forms of chlorophyll: a & b. Chlorophyll has a hydrocarbon tail that anchors it to an integral protein in the thylakoid membrane of the chloroplast. Chlorophyll is the source of the green color of plants and certain other autotrophs.

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Photosynthesis Basics - Study Guide

By Anne Marie Helmenstine, Ph.D.

chloroplast - A chloroplast is the organelle in a plant cell where photosynthesis occurs.

G3P - G3P stands for glucose-3-phosphate. G3P is an isomer of PGA formed during the Calvin cycle

glucose (C₆H₁₂O₆) - Glucose is the sugar that is the product of photosynthesis. Glucose is formed from 2 PGAL's.

granum - A granum is a stack of thylakoids (plural: grana)

light - Light is a form of electromagnetic radiation; the shorter the wavelength the greater amount of energy. Light supplies the energy for the light reactions of photosynthesis.

light harvesting complexes (photosystems complexes) -  A photosystem (PS) complex is a multi-protein unit in the thylakoid membrane that absorbed light to serve as energy for reactions

light reactions (light dependent reactions) - The light dependent reactions are chemical reactions requiring electromagnetic energy (light) that occur in the thylakoid membrane of the chloroplast to convert light energy into chemical forms ATP and NAPDH.

lumen - The lumen is the region within the thylakoid membrane where water is split to obtain oxygen. The oxygen diffuses out of the cell, while the protons remain inside to build positive electrical charge inside the thylakoid. 

mesophyll cell - A mesophyll cell is a type of plant cell located between the upper and lower epidermis that is the site for photosynthesis

NADPH - NADPH is a high-energy electron carrier used in reduction

oxidation - Oxidation refers to the loss of electrons

oxygen (O₂) - Oxygen is a gas that is a product of the light-dependent reactions

palisade mesophyll - The palisade meophyill is the area of the mesophyll cell without many air spaces

PGAL - PGAL is an isomer of PGA formed during the Calvin cycle.

photosynthesis - Photosynthesis is the process by which organisms convert light energy into chemical energy (glucose).

photosystem - A photosystem (PS) is a cluster of chlorophyll and other molecules in a thylakoid that harvest the energy of light for photosynthesis

pigment - A pigment is a colored molecule. A pigment absorbs specific wavelengths of light. Chlorophyll absorbs blue and red light and reflects green light, so it appears green.

reduction - Reduction refers to the gain of electrons. It often occurs in conjunction with oxidation.

rubisco - Rubisco is an enzyme that bonds carbon dioxide with RuBP

thylakoid - The thylakoid is a disc-shaped portion of chloroplast, found in stacks called grana.