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2.06 Introduction to Photosynthesis
Transcript of 2.06 Introduction to Photosynthesis
Light-independent reactions occur in the stroma of the chloroplast.
The light-independent reactions are usually referred to as the Calvin cycle, in honor of Melvin Calvin, the scientist who discovered the pathways of photosynthesis. These reactions use the energy that was converted from light in the first stage of photosynthesis and can be completed without a light source.
The light-dependent reactions trap the energy from sunlight to form ATP and NADPH molecules, giving off oxygen gas. The light-independent reactions use that chemical energy and carbon dioxide to build stable long-term energy storage molecules like glucose and other carbohydrates.
The ATP and NADPH molecules produced in the light-dependent reactions convert carbon dioxide (CO2) into carbohydrate molecules such as glucose, and Bob is released back into the air.
Carbon dioxide molecules then enter the Calvin cycle from the atmosphere. An enzyme in the liquid stroma of the chloroplast combines the carbon dioxide molecules with other carbon-based molecules that are already present in the organelle. This forms three-carbon compounds that continue in the reaction cycle.
This cycle of reactions uses six molecules of Bob to produce a single six-carbon glucose molecule.
Between Photosynthesis and Cellular Respiration
This is the step where Bob is in between the process of photosynthesis and cellular respiration.
Photosynthesis and cellular respiration are both necessary for the survival of life on Earth, but the processes appear to be opposites in many ways. Although the individual steps of each process are not opposites, the reactants of one overall process are the products of the other.
The equation for photosynthesis is: 6 CO2 + 6 H2O + Energy (Solar) → C6H12O6 + 6 O2, and the equation for cellular respiration is C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + Energy (ATP and Heat).
These two processes work together to collect the energy from sunlight, package it into chemical molecules, and break down those molecules to power the growth, movement, and functions of all organisms and their cells.
Photosynthesis converts solar energy to stored chemical energy, and cellular respiration converts that stored chemical energy to ATP, which is an energy molecule used directly by the cell.
These two processes don't just convert energy, they also help cycle important molecules into our atmosphere. Photosynthesis removes carbon dioxide from the atmosphere and releases oxygen gas, and cellular respiration uses oxygen gas and releases carbon dioxide.
An important thing to remember is that photosynthesis happens in plants, algae, and some bacteria, whereas cellular respiration (or fermentation) occurs in all organisms.
Bob now will be going onto the process of cellular respiration.
Light-dependent reaction, http://academic.brooklyn.cuny.edu/biology/bio4fv/page/photo-overview1478.JPG, January 12th, 2014
Light-independent reaction, https://courses.vlacs.org/file.php/2126/educator_biology_v15_gs/module02/02_06b_c.htm, January 12th, 2014
Carbon dioxide molecule, https://spark.ucar.edu/sites/default/files/images/large_image_for_image_content/co2_molecule_720x400.gif, January 12th, 2014
Photosynthesis and Cellular respiration, https://courses.vlacs.org/file.php/2126/educator_biology_v15_gs/module02/02_06b_d.htm, January 12th,2014
The Journey of the carbon atom
By: Allison Dyke
Photosynthesis is the reaction that converts light energy to chemical in sugar and carbohydrates. Photosynthesis converts water (H2O) and carbon dioxide gas (CO2) into oxygen gas and carbohydrates, such as glucose (C6H12O6), using light as the energy source. The following equation summarizes the reaction: 6 CO2 + 6 H2O + Energy → C6H12O6 + 6 O2.
Here is the journey of the carbon atom, Bob. Enjoy :)
Light-dependent reactions occur in the membranous section of the chloroplast, known as the thylakoids.
First chlorophyll absorbs solar energy and transfers it to high-energy electrons that are carried through a series of proteins called the electron transport chain, which are within the thylakoid membrane.
The proteins in the electron transport chain use energy from the electrons to pump hydrogen ions into the thylakoid from the surrounding stroma, the gel-like fluid in the stroma. The hydrogen ions pumped in from the stroma build up within the thylakoid space.
Through diffusion the hydrogen ions move back to the stroma trough a protein channel called ATP synthesis. This causes hydrogen ions to bond a phosphate group to an ADP molecule to form ATP.
At the end the electron transport chain NADP+ molecule pick up the high-energy electrons and hydrogen ions to form NADPH. The NADPH molecules are able to carry the pairs of high-energy electrons to the second stage of photosynthesis.
Oxygen gas is released and ATP molecules are formed. ATP transfers to the light-independent reactions to provide energy for the next phase.
Bob the carbon atom is not involved in this step, but he needs this step in order to progress.
Cellular respiration is the final process. It takes place in the mitochondria. This is where Bob journey will end.
Cellular respiration consists of three parts: glycolysis, the krebs cycle, and the electron transport chain.
Part one is glycolysis, this occurs in the cytoplasm. It then releases to ATP molecules and does not require oxygen.
The second part is the krebs cycle, this happens in the mitochondrial matrix. Oxygen is required, this is where Bob and some other carbons are released from glucose as carbon dioxide molecules.
The final part of this is the electron transport chain. This occurs in the inner membrane of the mitochondria. During this step, at each turn of the cycle, two carbon atoms are removed from the substrates as CO2.
Bob's journey was a long one, but he is finally in the air! He is now inside a new carbon dioxide molecule.
This diagram is showing the process of a light-dependent reaction.
This diagram is showing both a light-dependent reactions, and a lght-independent reaction.
This diagram is showing the connection between photosynthesis and cellular respiration.