Algae are aquatic, plant-like organisms. They encompass a variety of simple structures, from single-celled phytoplankton floating in the water, to large seaweeds macroalgae attached to the ocean floor 2. Algae can be found residing in oceans, lakes, rivers, ponds and even in snow, anywhere on Earth. So what makes algae only plant-like, instead of plants?
Chloroplast and Thylakoid In photosynthetic bacteria, the proteins that gather light for photosynthesis are embedded in cell membranes. In its simplest form, this involves the membrane surrounding the cell itself.
A typical plant cell contains about 10 to chloroplasts. The chloroplast is enclosed by a membrane. This membrane is composed of a phospholipid inner membrane, a phospholipid outer membrane, and an intermembrane space.
Enclosed by the membrane is an aqueous fluid called the stroma. Embedded within the stroma are stacks of thylakoids granawhich are the site of photosynthesis.
The thylakoids appear as flattened disks. The thylakoid itself is enclosed by the thylakoid membrane, and within the enclosed volume is a lumen or thylakoid space. Embedded in the thylakoid membrane are integral and peripheral membrane protein complexes of the photosynthetic system.
Plants absorb light primarily using the pigment chlorophyll. The green part of the light spectrum is not absorbed but is reflected which is the reason that most plants have a green color.
Besides chlorophyll, plants also use pigments such as carotenes and xanthophylls.
These pigments are embedded in plants and algae in complexes called antenna proteins. In such proteins, the pigments are arranged to work together. Such a combination of proteins is also called a light-harvesting complex.
Although all cells in the green parts of a plant have chloroplasts, the majority of those are found in specially adapted structures called leaves.
Certain species adapted to conditions of strong sunlight and ariditysuch as many Euphorbia and cactus species, have their main photosynthetic organs in their stems. The cells in the interior tissues of a leaf, called the mesophyllcan contain betweenandchloroplasts for every square millimeter of leaf.
The surface of the leaf is coated with a water-resistant waxy cuticle that protects the leaf from excessive evaporation of water and decreases the absorption of ultraviolet or blue light to reduce heating.
The transparent epidermis layer allows light to pass through to the palisade mesophyll cells where most of the photosynthesis takes place.
Light-dependent reactions Main article: Light-dependent reactions In the light-dependent reactionsone molecule of the pigment chlorophyll absorbs one photon and loses one electron.
This electron is passed to a modified form of chlorophyll called pheophytinwhich passes the electron to a quinone molecule, starting the flow of electrons down an electron transport chain that leads to the ultimate reduction of NADP to NADPH.
In addition, this creates a proton gradient energy gradient across the chloroplast membranewhich is used by ATP synthase in the synthesis of ATP. The chlorophyll molecule ultimately regains the electron it lost when a water molecule is split in a process called photolysiswhich releases a dioxygen O2 molecule as a waste product.
The overall equation for the light-dependent reactions under the conditions of non-cyclic electron flow in green plants is: The photosynthetic action spectrum depends on the type of accessory pigments present.
For example, in green plants, the action spectrum resembles the absorption spectrum for chlorophylls and carotenoids with absorption peaks in violet-blue and red light.
In red algae, the action spectrum is blue-green light, which allows these algae to use the blue end of the spectrum to grow in the deeper waters that filter out the longer wavelengths red light used by above ground green plants.Chlorophyll B is mainly found in land plants, aquatic plants and green algae benjaminpohle.com most of these organisms, the ratio of chlorophyll A to chlorophyll B is Due to the presence of this molecule, some organizations will group the green algae into the Plant Kingdom.
Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that can later be released to fuel the organisms' activities. This chemical energy is stored in carbohydrate molecules, such as sugars, which are synthesized from carbon dioxide and water – hence the name photosynthesis, from the Greek φῶς, phōs, "light", and σύνθεσις.
Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that can later be released to fuel the organisms' activities (energy transformation).This chemical energy is stored in carbohydrate molecules, such as sugars, which are synthesized from carbon dioxide and water – hence the name photosynthesis.
Chlorophyll B is mainly found in land plants, aquatic plants and green algae benjaminpohle.com most of these organisms, the ratio of chlorophyll A to chlorophyll B is Due to the presence of this molecule, some organizations will group the green algae into the Plant Kingdom.