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Cellular structure and function ii


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Cell Structure - All of the organelles of a eukaryotic cell

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Cellular structure and function ii

  1. 1. • Prokaryotic cells lack membrane-bound organelles that are found in eukaryotic cells. These pictures compare prokaryotic and eukaryotic cells.
  2. 2. The Nucleus and Cell Control • The nucleus is the leader of the eukaryotic cell because it contains the directions to make proteins. Every part of the cell depends on proteins, so by containing the blueprint to make proteins, the nucleus controls the activity of the organelles.
  3. 3. The Nucleus and Cell Control • The master set of directions for making proteins is contained in the chromatin, which are strands of genetic material, DNA. When a cell divides , the chromatin condenses to form chromosomes.
  4. 4. The Nucleus and Cell Control • Within the nucleus is a prominent organelle called the nucleolus, which makes ribosomes. Ribosomes are the sites where the cell produces proteins according to the directions of the DNA. Unlike other organelles, ribosomes are not bound by a membrane.
  5. 5. The Nucleus and Cell Control • Cytoplasm is the clear, gelatinous fluid inside a cell. As the ribosomes and the copied DNA are transported into the cytoplasm, they pass through the nuclear envelope through pores in the nuclear envelope.
  6. 6. Assembly, Transport, and Storage • The endoplasmic reticulum (ER) is the site of cellular chemical reactions. • The ER is arranged in a series of highly folded membranes suspended in the cytoplasm. The folding allows for a large amount of folded ER to fit in a small space.
  7. 7. Assembly, Transport, and Storage • Ribosomes in the cytoplasm are attached to the surface of the endoplasmic reticulum, called rough ER, where they carry out the function of protein synthesis. • The ribosome’s only job is to make proteins.
  8. 8. Assembly, Transport, and Storage • Areas of the ER that are not studded with ribosomes are known as smooth endoplasmic reticulum. The smooth ER is involved in numerous biochemical activities, including production and storage of lipids.
  9. 9. Assembly, Transport, and Storage • The Golgi apparatus is a flattened stack of tubular membranes that modify proteins. The Golgi apparatus sorts proteins into packages and packs them into membrane-bound structures called vesicles, to be sent to the appropriate destination.
  10. 10. Vacuoles and Storage • Cells have membrane-bound compartments, called vacuoles, for temporary storage of materials. A vacuole is a sac surrounded by a membrane. Vacuoles often store food, enzymes, and other materials needed by the cell and some vacuoles store waste products.
  11. 11. Lysosomes and Recycling • Lysosomes are organelles that contain digestive enzymes. They digest excess or worn out organelles, food particles, and engulfed viruses or bacteria. The membrane surrounding a lysosome prevents the digestive enzymes inside from destroying the cell.
  12. 12. Energy Transformers • Chloroplasts are cell organelles that capture light energy and convert it to chemical energy. A chloroplast has a double membrane. There is an outer membrane and a folded inner membrane system. It is within these inner thylakoid membranes that the energy from sunlight is trapped. These membranes are arranged in stacks of membranous sacs called grana, which resemble stacks of coins.
  13. 13. Energy Transformers • The chloroplast belongs to a group of plant organelles called plastids, which are used for storage. Plastids are named according to their color or the pigment that they contain. Chloroplasts contain the green pigment chlorophyll. Chlorophyll traps light energy and gives leaves and stems their green color.
  14. 14. Energy Transformers • Mitochondria are membrane-bound organelles in plant and animal cells that transform energy for the cell. This energy is then stored in the bonds of other molecules that cell organelles can access easily when energy is needed.
  15. 15. Energy Transformers A mitochondrion has an outer membrane and a highly folded inner membrane. The folds of the inner membrane provides a large surface area that fits inside a small space. Energy-storing molecules are produced on the inner folds of the mitochondria. The number of mitochondria within a cell depends on the function of the cell.
  16. 16. The Cytoskeleton • The cytoskeleton forms a framework for the cell, like the skeleton forms a framework for your body. The cytoplasm is a constantly changing structure. • The cytoskeleton is a network of tiny rods and filaments. Microtubules are thin, hollow cylinders made of protein. Microfilaments are smaller, solid protein fibers. Together, they help maintain the shape of a cell like poles help maintain the shape of a tent.
  17. 17. Centrioles • Centrioles are organelles found in the cells of animals and most protists. They occur in pairs and are made up of microtubules. Centrioles play an important role in cell division.
  18. 18. Locomotion • Some cell surfaces have cilia and flagella, which are organelles made of microtubules that aid the cell in locomotion or feeding. Cilia and flagella can be distinguished by their structure and by the nature of their action.
  19. 19. Locomotion • Cilia are short, numerous projections that look like hairs. Their motion is similar to that of oars in a rowboat.
  20. 20. Locomotion • Flagella are longer projections that move with a whip-like motion. A cell usually only has one or two flagella. In unicellular organisms, cilia and flagella are the major means of locomotion.