Chloroplast

  • ∗∗Chloroplasts∗∗**Chloroplasts** arefoundinallorganismsthatcarryoutphotosynthesis.are found in all organisms that carry out photosynthesis. This means that they aren’t only found in plants. They are also found in algae, phytoplankton, and some bacteria.

Photosynthesis

  • ∗∗Photosynthesis∗∗**Photosynthesis** istheprocessofturninglightenergyfromtheSunintochemicalenergyis the process of turning light energy from the Sun into chemical energy, which can then be used by cells for energy. The formula for photosynthesis is:

 

  • This means that plants require both carbon dioxide (CO2) and water (H2O) in addition to light energy as reactants, or ingredients, for photosynthesis and produce glucose (C6H12O6) and oxygen (O2) as products. Theproduct∗∗glucose∗∗hasstoredenergy,whichcanthenbeusedbyanycell,notjustplantcells,topowercellactivities.The product **glucose** has stored energy, which can then be used by any cell, not just plant cells, to power cell activities.
  • Photosynthesis has two sets of reactions: lightanddarkreactionslight and dark reactions. The light reactions require light, but the dark reactions do not. Darkreactionscanoccurinthepresenceoflight,butitisnotrequired.Dark reactions can occur in the presence of light, but it is not required.

Structure

  • Chloroplastsaretheplaceinthecellwherephotosynthesistakesplace.Chloroplasts are the place in the cell where photosynthesis takes place.
  • Like the mitochondria, chloroplastshavetheirownDNAchloroplasts have their own DNA. It is thought that mitochondria and chloroplasts were once free-living, single-celled organisms that developed a relationship with early cells and eventually became part of the cell (see Endosymbiosis).
  • ChloroplastshaveaninnerandanoutermembraneChloroplasts have an inner and an outer membrane, which is known as a bi-layer membrane. Mitochondria, cells, and the nucleus have a similar membrane. Inthemiddleofthechloroplastisaninter−membranespacethatincludesathickfluidcalled∗∗stroma∗∗.In the middle of the chloroplast is an inter-membrane space that includes a thick fluid called **stroma**. The stroma houses the chloroplast’s DNA, its ribosomes, sugars, enzymes, and thylakoids.
  • In the center of the chloroplasts are thylakoids, which areanetworkofinterconnectedsacsthatcontainphotosyntheticpigmentsare a network of interconnected sacs that contain photosynthetic pigments. Photosynthesis occurs in the thylakoids. These sacs are arranged in stacks called grana (singular: granum).
  • Thylakoidscontainthepigments∗∗chlorophylla∗∗and∗∗b∗∗,whichcapturelightforthecell.Thesetwopigmentsreflectgreenlight,whichiswhatmakesplantsappeargreen.Thylakoids contain the pigments **chlorophyll a** and **b**, which capture light for the cell. These two pigments reflect green light, which is what makes plants appear green.

 Edited: 05 October 2022