Chloroplasts

Chloroplasts are specialised organelles involved in the process of photosynthesis, the conversion of light into cellular energy. As such, they are characteristic of green plants and algae. Like mitochondria, chloroplasts are surrounded by a double membrane, and serve as the location for energy-generating reactions. Inside the chloroplast are

Outer

Grana (thylakoi

Strorr

Outer

Grana (thylakoi

Strorr

Inner membrane

Figure 3.16 Chloroplast structure. Adenosine triphosphate generation from photosynthesis occurs on the thylakoid membranes. In green algae these take the form of discrete structures called grana. The enzyme ribulose bisphosphate carboxylase, responsible for fixing carbon dioxide via the Calvin cycle (see Chapter 6) is located in the stroma. The outer membrane of chloroplasts is relatively permeable, allowing the diffusion of the products of photosynthesis into the surrounding cytoplasm. Reproduced by permission of Dr Lance Gibson, Iowa State University

Inner membrane

Figure 3.16 Chloroplast structure. Adenosine triphosphate generation from photosynthesis occurs on the thylakoid membranes. In green algae these take the form of discrete structures called grana. The enzyme ribulose bisphosphate carboxylase, responsible for fixing carbon dioxide via the Calvin cycle (see Chapter 6) is located in the stroma. The outer membrane of chloroplasts is relatively permeable, allowing the diffusion of the products of photosynthesis into the surrounding cytoplasm. Reproduced by permission of Dr Lance Gibson, Iowa State University flattened membranous sacs known as thylakoids, which contain the photosynthetic pigment chlorophyll. Thylakoids are arranged in stacks called grana (Figure 3.16).

Mitochondria and chloroplasts both contain 70S ribosomes (similar to those found in procaryotes), a limited amount of circular DNA and the means to replicate themselves. This is seen as key evidence for the endosymbiotic theory of eucaryotic evolution, which envisages that specialised organelles within eucaryotic cells arose from the ingestion of small procaryotes, which over a long period of time lost their independent existence.

Was this article helpful?

0 0
How To Win Your War Against Bronchitis

How To Win Your War Against Bronchitis

Sick And Tired Of Your Constant Cough? Is Your Bad Immune System Leading You To The Path Of Fever And Sore Chest? You Sure Have A Reason To Panic BronchitisThere Is Always A Way Out And, This Is It Finally Discover Some Of The Most Effective Tips That Can Curb Bronchitis, And Its Repeated Bouts Learn How To Keep The Chronic Cough, And Sore Chest Away Breathe Free, And Feel The Whiff Of Fresh Air, With No Hassles

Get My Free Ebook


Post a comment