1. Copyright © 2009 Pearson Education, Inc.. Lectures by Gregory Ahearn University of North Florida Chapter 4 Cell Structure and Function

2. Copyright © 2009 Pearson Education Inc. 4.1 What Features Are Shared By All Cells?  Cells are the smallest unit of life.  Cells are enclosed by a plasma membrane.  Cells use DNA as a hereditary blueprint.  Cells contain cytoplasm, which is all the material inside the plasma membrane and outside the DNA-containing region.  Cells obtain energy and nutrients from their environment.

3. Copyright © 2009 Pearson Education Inc. 4.1 What Features Are Shared By All Cells?  Cell function limits cell size. Diffusion of molecules across cell membranes limits the diameter of cells. As cells get bigger, their nutrient and waste elimination needs grow faster than the membrane area to accommodate them.

4. Copyright © 2009 Pearson Education Inc. 4.1 What Features Are Shared By All Cells?  The volume of cytoplasm grows faster than the plasma membrane area. Fig. 4-2

5. Copyright © 2009 Pearson Education Inc. 4.2 How Do Prokaryotic And Eukaryotic Cells Differ?  There are two kinds of cells. Prokaryotic cells Are found only in two groups of single- celled organisms—the bacteria and archaea Eukaryotic cells Are structurally more complex cells Possess a membrane-enclosed nucleus Probably arose from prokaryotic cells

6. Copyright © 2009 Pearson Education Inc. 4.3 What Are The Main Features Of Eukaryotic Cells?  Eukaryotic cells differ from prokaryotic cells because the former possess a number of membrane-enclosed organelles that perform specific cell functions. Nucleus: contains DNA Mitochondria: produce energy Endoplasmic reticulum: synthesizes membrane components and lipids Golgi apparatus: molecule sorting center Lysosomes: digest cellular membranes or defective organelles Microtubules: make up the cytoskeleton

7. Copyright © 2009 Pearson Education Inc. 4.3 What Are The Main Features Of Eukaryotic Cells?  A generalized animal cell Fig. 4-3 mitochondrion vesicle cytoplasm flagellum lysosome centriole intermediate filaments Golgi apparatus vesicle nuclear pore nuclear envelope chromatin (DNA) nucleolus nucleus plasma membrane rough endoplasmic reticulum ribosome free ribosome smooth endoplasmic reticulum microtubules

8. Copyright © 2009 Pearson Education Inc. 4.3 What Are The Main Features Of Eukaryotic Cells?  A generalized plant cell Fig. 4-4 central vacuole mitochondrion vesicle plasmodesma cell wall plasma membrane intermediate filaments free ribosome ribosomes nucleus nucleolus nuclear pore chromatin nuclear envelope rough endoplasmic reticulum smooth endoplasmic reticulum Golgi apparatus chloroplast microtubules (part of cytoskeleton)

9. Copyright © 2009 Pearson Education Inc. 4.4 What Role Does The Nucleus Play?  The nucleus is the largest organelle in the cell. It is bounded by a nuclear envelope. It contains granular-looking chromatin. It contains the nucleolus.

10. Copyright © 2009 Pearson Education Inc. 4.4 What Role Does The Nucleus Play?  The nucleus nucleus nuclear pores (b) Yeast cell nuclear envelope nuclear pores nucleolus chromatin (a) Structure of the nucleus Fig. 4-5

11. Copyright © 2009 Pearson Education Inc. 4.4 What Role Does The Nucleus Play?  The nuclear envelope is a double membrane. The membrane is perforated with channels called nuclear pores. Some smaller materials can move through the pores, while others, such as DNA, are excluded.

12. Copyright © 2009 Pearson Education Inc. 4.4 What Role Does The Nucleus Play?  The nucleus contains chromosomes. DNA and protein are closely associated in the nucleus in chromatin. Chromatin can become condensed into chromosomes. Fig. 4-6 chromatin chromosome

13. Copyright © 2009 Pearson Education Inc. 4.4 What Role Does The Nucleus Play?  Ribosomes are composed of RNA and proteins, and serve as a “workbench” for the manufacture of proteins.

14. Copyright © 2009 Pearson Education Inc. 4.4 What Role Does The Nucleus Play?  Ribosome components are made at the nucleolus. A darkly staining region in the nucleus is called a nucleolus. The nucleolus contains DNA, RNA, proteins, and ribosomes in various stages of construction. This is the site where components of ribosomes are constructed. Ribosome components leave the nucleus and are assembled in the cytoplasm.

15. Copyright © 2009 Pearson Education Inc. 4.5 What Roles Do Membranes Play In Eukaryotic Cells?  The plasma membrane isolates the cell, and alternately, helps it interact with its environment. The phospholipid bilayer contains globular proteins that regulate the transport of molecules into and out of the cell. Plant cells also have a rigid structure outside the plasma membrane, called a cell wall, which forms a protective coating.

16. Copyright © 2009 Pearson Education Inc. 4.5 What Roles Do Membranes Play In Eukaryotic Cells?  The endoplasmic reticulum (ER) forms channels within the cytoplasm. There are two kinds of ER membranes: Rough endoplasmic reticulum: is studded with ribosomes Smooth endoplasmic reticulum: has no ribosomes

17. Copyright © 2009 Pearson Education Inc. 4.5 What Roles Do Membranes Play In Eukaryotic Cells?  The endoplasmic reticulum Fig. 4-7 (a) (b) Endoplasmic reticulum may be rough or smooth Smooth and rough ER ribosomes smooth ER rough ER vesicles

18. Copyright © 2009 Pearson Education Inc. 4.5 What Roles Do Membranes Play In Eukaryotic Cells?  The rough ER is the site where proteins are made.  The smooth ER makes phospholipids and cholesterol.  Together, the rough and smooth ER are the sites of new membrane synthesis for the cell.

19. Copyright © 2009 Pearson Education Inc. 4.5 What Roles Do Membranes Play In Eukaryotic Cells?  The Golgi apparatus sorts, chemically alters, and packages important molecules. This organelle looks like a stack of flattened sacs. Its membranes are derived from the ER. Vesicles containing preformed molecules from the ER are transferred to the Golgi for further processing.

20. Copyright © 2009 Pearson Education Inc. 4.5 What Roles Do Membranes Play In Eukaryotic Cells?  The Golgi apparatus Fig. 4-8 Golgi apparatus Protein-carrying vesicles from the ER merge with the Golgi apparatus Vesicles carrying modified proteins leave the Golgi apparatus

21. Copyright © 2009 Pearson Education Inc. 4.5 What Roles Do Membranes Play In Eukaryotic Cells?  Once the molecular work of the Golgi has been done, new vesicles bud off and travel elsewhere in the cytoplasm, where they fuse with membranes of other organelles, such as the plasma membrane.  A major role of the Golgi is to add sugar molecules to proteins formed in the ER and to pass them on to other places in the cell.

22. Copyright © 2009 Pearson Education Inc. 4.5 What Roles Do Membranes Play In Eukaryotic Cells?  We can follow the travels of a secreted protein. An antibody protein is synthesized on ribosomes of the rough ER. Formed antibody is packaged into vesicles that travel to the Golgi, where carbohydrates are attached to protein to make an antibody.

23. Copyright © 2009 Pearson Education Inc. 4.5 What Roles Do Membranes Play In Eukaryotic Cells?  We can follow the travels of a secreted protein (continued). The vesicle containing antibody leaves the Golgi and goes to the plasma membrane, where it fuses with it. The antibody inside the vesicle is released to the outside of the cell (to the blood), where it helps defend the body against infection.

24. Copyright © 2009 Pearson Education Inc. 4.5 What Roles Do Membranes Play In Eukaryotic Cells?  Lysosomes are vesicles that serve as the cell’s digestive system. They are formed as buds from the Golgi. Lysosomes contain digestive enzymes that they receive from Golgi during their production. In the cytoplasm, they digest defective organelles or pieces of membrane into component parts that can be recycled.

25. Copyright © 2009 Pearson Education Inc. 4.6 What Other Structures Play Key Roles In Eurkaryotic Cells?  Vacuoles regulate water and store substances. They are fluid-filled sacs surrounded by a single membrane. Many plant cells have a large central vacuole. Vacuoles hold water and help maintain the proper water balance of the cell. Vacuoles can also serve as dump sites for hazardous waste that can’t be excreted. They can also store sugars and amino acids, which can be used for energy.

26. Copyright © 2009 Pearson Education Inc. 4.6 What Other Structures Play Key Roles In Eurkaryotic Cells?  Mitochondria extract energy from food molecules. Mitochondria provide the energy needed for all cellular processes. Energy is obtained from sugar molecules in mitochondria and is stored in ATP molecules. Once formed, ATP can be used anywhere in the cell where energy is needed. Mitochondria have a complex set of outer and inner membranes, and both sets are used in the process of energy production.

27. Copyright © 2009 Pearson Education Inc. 4.6 What Other Structures Play Key Roles In Eurkaryotic Cells?  Chloroplasts capture solar energy. Only plant cells contain chloroplasts. Chloroplasts capture energy from sunlight and store it in sugar molecules. They are the site of photosynthesis, the process upon which all life depends. Like mitochondria, chloroplasts contain both outer and inner membranes.

28. Copyright © 2009 Pearson Education Inc. 4.6 What Other Structures Play Key Roles In Eurkaryotic Cells?  The cytoskeleton provides shape, support, and movement. All organelles in the cell do not float about the cytoplasm, but instead, are attached to a network of protein fibers called the cytoskeleton.

29. Copyright © 2009 Pearson Education Inc. 4.6 What Other Structures Play Key Roles In Eurkaryotic Cells?  Several type of protein fibers make up the cytoskeleton. Microfilaments: thin fibers Intermediate filaments: medium-sized fibers Microtubules: thick fibers

30. Copyright © 2009 Pearson Education Inc. 4.6 What Other Structures Play Key Roles In Eurkaryotic Cells?  The cytoskeleton Fig. 4-9 plasma membrane microfilaments mitochondrion intermediate filaments ribosomes endoplasmic reticulum microtubule vesicle (a) Components of the cytoskeleton (b) Cell with stained cytoskeleton microtubules (red) nucleus microfilaments (blue)

31. Copyright © 2009 Pearson Education Inc. 4.6 What Other Structures Play Key Roles In Eurkaryotic Cells?  Cilia and flagella move the cell or move fluid past the cell. Cilia and flagella are slender, movable extensions of the plasma membrane. They contain microtubules that extend along their length. They may be used to move small animals or particle-containing fluids past a surface.

32. Copyright © 2009 Pearson Education Inc. 4.6 What Other Structures Play Key Roles In Eurkaryotic Cells?  Cilia and flagella move the cell or move fluid past the cell (continued). Differences between cilia and flagella lie in their length, number, and the direction of force generated. Cilia are shorter and more numerous than flagella.

33. Copyright © 2009 Pearson Education Inc. 4.6 What Other Structures Play Key Roles In Eurkaryotic Cells?  Cilia provide force parallel to the plasma membrane, which can be described as a “rowing” motion. Fig. 4-10a return stroke cilia lining the trachea plasma membrane power stroke (a) Cilium propulsion of fluid

34. Copyright © 2009 Pearson Education Inc. 4.6 What Other Structures Play Key Roles In Eurkaryotic Cells?  Flagella provide a force perpendicular to plasma membrane, like the engine on a motorboat. flagellum of human sperm continuous propulsion direction of locomotion (b) Flagellum propulsion of fluid Fig. 4-10b

35. Copyright © 2009 Pearson Education Inc. 4.7 What Are The Features Of Prokaryotic Cells?  Prokaryotic cells are much smaller than eukaryotic cells, are more abundant, and are very reproductively successful.  The are very small and have a simple internal structure.  They are surrounded by a stiff cell wall, which provides shape and protection.  Some move with a whiplike flagellum.

36. Copyright © 2009 Pearson Education Inc. 4.7 What Are The Features Of Prokaryotic Cells?  A single, circular strand of DNA is attached to the plasma membrane and is concentrated in an area called the nucleoid, which lacks a membrane.  There are no membrane-enclosed organelles.  The cytoplasm contains ribosomes used for protein synthesis.

37. Copyright © 2009 Pearson Education Inc. 4.7 What Are The Features Of Prokaryotic Cells?  A generalized prokaryotic cell chromosome (nucleoid region) ribosomes food granule prokaryotic flagellum cell wall plasma membrane cytoplasm Fig. 4-11