They sustain themselves without eating anything derived from other living beings. They produce their organic molecules from CO2 and other inorganic raw materials obtained from the environment. They are the ultimate sources of organic compounds for all nonautotrophic organisms, and for this reason, biologists refer to them as the producers of the biosphere.
Process by which plants and some other organisms use light energy to convert water and carbon dioxide into oxygen and high-energy carbohydrates such as sugars and other organic compounds. This process nourishes almost the entire living world directly or indirectly. This consists of two processes, each with multiple steps. These two stages of photosynthesis are known as the light reactions (the photo part of photosynthesis) and the Calvin cycle (the synthesis part).
Almost all of them are autotrophs. They are specifically photoautotrophs.
organism that uses energy from sunlight to convert carbon dioxide and water to carbon compounds
In what organisms can photosynthesis occur in?
Plants, algae (such as kelp), certain other protists (Euglena), and some prokaryotes (cyanobacteria, and purple sulfur bacteria).
They live on compounds produced by other organisms. They are the biosphere's consumers.
The most obvious form of this "other-feeding" occurs when an animal eats plants or other animals. Almost all of them, including humans, are completely dependent, either directly or indirectly, on photoautotrophs for food-and also for oxygen, a by-product of photosynthesis.
What are some subtle forms of heterotrophic nutrition?
Some heterotrophs consume the remains
of dead organisms by decomposing and feeding on organic litter such as carcasses, feces, and fallen leaves; they are known as decomposers. Most fungi and many types of prokaryotes get their nourishment this way.
How is the structural organization of a cell important to ability to drive photosynthesis?
Photosynthetic enzymes and other molecules are grouped together in a biological membrane, enabling the necessary series of chemical reactions to be carried out efficiently.
Origins of Photosynthesis
The process ofphotosynthesis most likely originated in a group of bacteria that had infolded regions of the plasma membrane containing clusters of such molecules. In existing photosynthetic bacteria, infolded photosynthetic
membranes function similarly to the internal membranes of the chloroplast.
Believed to have been a photosynthetic prokaryote that lived inside a eukaryotic cell, this organelle is present in a variety of photosynthesizing organisms.
The green pigment located within chloroplasts which gives leaves their distinctive green color. It is the light energy absorbed by this pigment that drives the synthesis of organic molecules in the chloroplast.
The tissue in the interior of the leaf. It is in the cells of this that most of the chloroplast are found.
Microscopic pores through which carbon dioxide enters the leaf, and oxygen exits.
Through these structures water that was absorbed by the roots is delivered to the leaves, and they also export sugar from the leaves to the
roots and other nonphotosynthetic parts of the plant.
Typicial mesophyll cell
Has about 30 to 40 chloroplasts, each organelle measuring about 2-4 um by 4-7 um.
Dense fluid within the chloroplast, which is enclosed by an envelope of two membranes. The Calvin Cycle happens here.
An elaborate system of interconnected membranous sacs that segregates the stroma from the interior of the thylakoids, or the thylakoid space. This is the specific location where chlorophyll resides. This also refers to the infolded photosynthetic membranes of prokaryotes. Light reactions happen hear.
Granum (pl. Grana)
Column of thylakoid sacs.
Overall Photosynthethic Equation
6C02 + 12 H20 + Light energy--> C6H1206 +602 + 6H20
What is special about glucose in the Photosynthethic equation?
The direct product of photosynthesis is actually a three-carbon sugar that can be used to make glucose.
Simplified Photosynthethic Equation
6C02 + 6 H20 + Light energy--> C6H1206 +602
Where is the O2 product derived from?
From the H20 reactant, not the CO2.
C. B. van Niel
Challenged the idea that O2 was from the splitting of CO2. He investigated photosynthesis
in bacteria that make their carbohydrate from CO2
but do not release O2. from H2S, 2S was realesed. Therefore, since no O2 was released, then Carbon dioxide is not compound that is split in photosynthesis for the purpose of giving off a waste product. The compound that is split is the Hydrogen containing compound (H2O, H2S, etc.).
How was van Neil's hypothesis confirmed?
By using oxygen-18 , a heavy isotope, as a
tracer to follow the fate of oxygen atoms during photosynthesis. The experiments showed that the O2 from plants was labeled with oxygen-18 only if water was the source of the tracer. If the oxygen-18 was introduced to the plant in the form of CO2, the label did not turn up in the released O2.
Comparative Analysis of Photosynthesis and Cellular Respiration
Both processes involve redox reactions. During cellular respiration, energy is released from sugar when electrons associated with hydrogen are transported by carriers to oxygen, forming water as a by-product. The electrons lose potential
energy as they "fall" down the electron transport chain toward electronegative oxygen, and the mitochondrion harnesses that energy to synthesize ATP (see Figure 9.16). Photosynthesis
reverses the direction of electron flow. Water is split, and electrons are transferred along with hydrogen ions from the water to carbon dioxide, reducing it to sugar. Because the electrons increase in potential energy as they move from water to sugar, this process requires energy, in other words is endergonic. This energy boost is provided by light.
The steps that convert solar energy to chemical energy. energy. Water is split, providing a source
of electrons and protons (hydrogen ions, H+) and gives of O2 as a by product. Light absorbed by chlorophyll drives a transfer of
the electrons and hydrogen ions from water to an acceptor called NADP+. Solar power is used to reduce NADP+ to NADPH by adding a pair of electrons along with an H+. These reactions also generate ATP, using chemiosmosis to power to phosphorylate ADP. Thus, light energy is initially converted to chemical energy in the
form of two compounds: NADPH, a source of electrons as "reducing power~ that can be passed along to an electron acceptor, reducing it, andATP, the versatile energy currency ofceUs.
Nicotinamide adenine dinucleotide phosphate, This electron acceptor NADP+ is a first
cousin to NAD+, they differ only by a phosphate group.
Part of photosynthesis that produces sugar. First step is carbon fixation. The fixed carbon is then reduced to carbohydrate by the addition of electrons.The reducing power is provided for by NADPH. To convert CO2 to carbohydrate, the Calvin cycle also requires chemical energy
in the form of ATP, which is also generated by the light reactions.
The incorporation of CO2 from the air into organic molecules already present in the chloroplast.
Epic Calvin Cycle Paragraph
Thus, it is the Calvin cycle that makes sugar, but it can do so only with the help of the NADPH and ATP produced by the light reactions. The metabolic steps of the Calvin cycle are sometimes referred to as the dark reactions, or light independent reactions, because none of the steps requires light directly. Nevertheless, the Calvin cycle in most plants occurs during daylight, for only then can the light reactions provide the NADPH and ATP that the Calvin cycle requires. In essence, the chloroplast uses light energy to make sugar by coordinating the two stages of photosynthesis.