Info

3.13 Membrane-Bound Organelles

Figure 3.55 Mitochondria These harvest the energy released during the degradation of organic compounds to synthesize ATP. (a) Diagrammatic representation. (b) Electron micrograph.

Figure 3.55 Mitochondria These harvest the energy released during the degradation of organic compounds to synthesize ATP. (a) Diagrammatic representation. (b) Electron micrograph.

Outer membrane Inner membrane

Outer membrane Inner membrane

Figure 3.56 Chloroplasts These harvest the energy of sunlight to generate ATP. The then used to convert CO2 to an organic form.

extruded through a special gated pore in the membrane of the ER. Within the lumen, they fold to assume their three-dimensional shape. Vesicles that bud off from the ER transfer the newly synthesized molecules to the Golgi apparatus for further modification and sorting.

Some regions of the ER are smooth. This smooth endo-plasmic reticulum provides a variety of functions including lipid synthesis and degradation, and calcium ion storage. The quantity of the smooth ER varies according to cell type; it is particularly prevalent in cells that specialize in the synthesis and secretion of steroid hormones. As with material made in the rough ER, vesicles transfer compounds from the smooth ER to the Golgi apparatus.

The Golgi Apparatus

The Golgi apparatus consists of a series of membrane-bound flattened sacs (figure 3.58). It is the site where macromolecules synthesized in the endoplasmic reticulum are modified before they are transported to other destinations. These modifications, such as the addition of carbohydrate and phosphate groups, take place in a sequential order in different Golgi sacs. Much like an assembly line, the molecules are transferred in vesicles from one Golgi sac to another. These various molecules are then sorted and delivered in vesicles destined either for specific cellular compartments or to the outside of the cell.

Lysosomes and Peroxisomes

Lysosomes are organelles that contain a number of powerful degradative enzymes. These include various proteases and nucle-ases that could destroy the cell if not contained within the organelle. Recall that material brought into the cell through endocytosis is digested when the endosome or phagosome fuses with the lysosome. In a similar manner, exhausted organelles can fuse with a lysosome so that their contents are digested.

Chapter 3 Microscopy and Cell Structure

Rough endoplasmic reticulum

Figure 3.57 Endoplasmic Reticulum Site of synthesis of macromolecules destined for other organelles or the external environment.

Rough endoplasmic reticulum

Smooth endoplasmic reticulum

Smooth endoplasmic reticulum

0.08 mm

Figure 3.57 Endoplasmic Reticulum Site of synthesis of macromolecules destined for other organelles or the external environment.

0.08 mm

Peroxisomes are the organelles in which oxygen is used to oxidize substances, breaking down lipids and detoxifying certain chemicals. As a consequence, their enzymes generate highly reactive molecules such as hydrogen peroxide and superoxide. The peroxisome contains these molecules and ultimately degrades them, protecting the cell from their toxic effects. ■ hydrogen peroxide, p. 89 ■ superoxide, p. 89

How To Cure Yeast Infection

How To Cure Yeast Infection

Now if this is what you want, you’ve made a great decision to get and read this book. “How To Cure Yeast Infection” is a practical book that will open your eyes to the facts about yeast infection and educate you on how you can calmly test (diagnose) and treat yeast infection at home.

Get My Free Ebook


Post a comment