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A Tour of the Cell

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A Tour of the Cell LECTURE PRESENTATIONS For CAMPBELL BIOLOGY, NINTH EDITION Jane B. Reece, Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, Robert B. Jackson Chapter 6 A Tour of the Cell Lectures by Erin Barley Kathleen Fitzpatrick © 2011 Pearson Education, Inc. Overview: The Fundamental Units of Life • All organisms are made of cells • The cell is the simplest collection of matter that can be alive • Cell structure is correlated to cellular function • All cells are related by their descent from earlier cells © 2011 Pearson Education, Inc. Figure 6.2 10 m Human height 1 m Length of some nerve and muscle cells 0.1 m Chicken egg 1 cm eye Unaided Frog egg 1 mm Human egg 100 m Most plant and animal cells 10 m Nucleus Most bacteria microscopy Light Mitochondrion 1 m Smallest bacteria 100 nm Super- Viruses resolution microscopy Ribosomes 10 nm microscopy Electron Proteins Lipids 1 nm Small molecules 0.1 nm Atoms Concept 6.2: Eukaryotic cells have internal membranes that compartmentalize their functions • The basic structural and functional unit of every organism is one of two types of cells: prokaryotic or eukaryotic • Only organisms of the domains Bacteria and Archaea consist of prokaryotic cells • Protists, fungi, animals, and plants all consist of eukaryotic cells © 2011 Pearson Education, Inc. Comparing Prokaryotic and Eukaryotic Cells • Basic features of all cells – Plasma membrane – Semifluid substance called cytosol – Chromosomes (carry genes) – Ribosomes (make proteins) © 2011 Pearson Education, Inc. • Prokaryotic cells are characterized by having – No nucleus – DNA in an unbound region called the nucleoid – No membrane-bound organelles – Cytoplasm bound by the plasma membrane © 2011 Pearson Education, Inc. Figure 6.5 Fimbriae Nucleoid Ribosomes Plasma membrane Bacterial chromosome Cell wall Capsule 0.5 m (a) A typical Flagella (b) A thin section rod-shaped through the bacterium bacterium Bacillus coagulans (TEM) Figure 6.5a 0.5 m (b) A thin section through the bacterium Bacillus coagulans (TEM) • Eukaryotic cells are characterized by having – DNA in a nucleus that is bounded by a membranous nuclear envelope – Membrane-bound organelles – Cytoplasm in the region between the plasma membrane and nucleus • Eukaryotic cells are generally much larger than prokaryotic cells © 2011 Pearson Education, Inc. • The plasma membrane is a selective barrier (semi-permiable) that allows sufficient passage of oxygen, nutrients, and waste to service the volume of every cell • The general structure of a biological membrane is a double layer of phospholipids © 2011 Pearson Education, Inc. Figure 6.6 (a) TEM of a plasma Outside of cell membrane Inside of cell 0.1 m Carbohydrate side chains Hydrophilic region Hydrophobic region Hydrophilic Phospholipid Proteins region (b) Structure of the plasma membrane • Metabolic requirements set upper limits on the size of cells • The surface area to volume ratio of a cell is critical • As the surface area increases by a factor of n2, the volume increases by a factor of n3 • Small cells have a greater surface area relative to volume • Elongating the cell increases SA without changing the volume. (microvilli) © 2011 Pearson Education, Inc. Figure 6.7 Surface area increases while total volume remains constant 5 1 1 Total surface area [sum of the surface areas (height width) of all box 6 150 750 sides number of boxes] Total volume [height width length number of boxes] 1 125 125 Surface-to-volume (S-to-V) ratio [surface area volume] 6 1.2 6 A Panoramic View of the Eukaryotic Cell • A eukaryotic cell has internal membranes that partition the cell into organelles • Plant and animal cells have most of the same organelles © 2011 Pearson Education, Inc. BioFlix: Tour of an Animal Cell © 2011 Pearson Education, Inc. BioFlix: Tour of a Plant Cell © 2011 Pearson Education, Inc. Figure 6.8a ENDOPLASMIC RETICULUM (ER) Nuclear Rough Smooth envelope Flagellum ER ER NUCLEUS Nucleolus Chromatin Centrosome Plasma membrane CYTOSKELETON: Microfilaments Intermediate filaments Microtubules Ribosomes Microvilli Golgi apparatus Peroxisome Mitochondrion Lysosome Figure 6.8c Nuclear Rough envelope endoplasmic reticulum Smooth NUCLEUS Nucleolus endoplasmic reticulum Chromatin Ribosomes Central vacuole Golgi apparatus Microfilaments Intermediate CYTOSKELETON filaments Microtubules Mitochondrion Peroxisome Plasma membrane Chloroplast Cell wall Plasmodesmata Wall of adjacent cell Concept 6.3: The eukaryotic cell’s genetic instructions are housed in the nucleus and carried out by the ribosomes • The nucleus contains most of the DNA in a eukaryotic cell- majority of the time DNA does not leave the Nucleus • Ribosomes use the information from the DNA to make proteins © 2011 Pearson Education, Inc. The Nucleus: Information Central • The nucleus contains most of the cell’s genes and is usually the most conspicuous organelle • The nuclear envelope encloses the nucleus, separating it from the cytoplasm • The nuclear membrane is a double membrane; each membrane consists of a lipid bilayer © 2011 Pearson Education, Inc. • Pores regulate the entry and exit of molecules from the nucleus • The shape of the nucleus is maintained by the nuclear lamina, which is composed of protein © 2011 Pearson Education, Inc. Figure 6.9 1 m Nucleus Nucleolus Chromatin Nuclear envelope: Inner membrane Outer membrane Nuclear pore Rough ER Pore complex Surface of nuclear envelope Ribosome Close-up m of nuclear Chromatin envelope 0.25 m 1 Pore complexes (TEM) Nuclear lamina (TEM) Figure 6.9a Nucleus Nucleolus Chromatin Nuclear envelope: Inner membrane Outer membrane Nuclear pore Rough ER Pore complex Ribosome Close-up of nuclear Chromatin envelope Figure 6.9b 1 m Nuclear envelope: Inner membrane Outer membrane Nuclear pore Surface of nuclear envelope Figure 6.9c m 0.25 Pore complexes (TEM) Figure 6.9d m 1 Nuclear lamina (TEM) • In the nucleus, DNA is organized into discrete units called chromosomes • Each chromosome is composed of a single DNA molecule associated with proteins • The DNA and proteins of chromosomes are together called chromatin • Chromatin condenses to form discrete chromosomes as a cell prepares to divide • The nucleolus is located within the nucleus and is the site of ribosomal RNA (rRNA) synthesis- what makes the ribosomes… different. © 2011 Pearson Education, Inc. Ribosomes: Protein Factories • Ribosomes are particles made of ribosomal RNA and protein • Ribosomes carry out protein synthesis in two locations – In the cytosol (free ribosomes) – On the outside of the endoplasmic reticulum or the nuclear envelope (bound ribosomes) © 2011 Pearson Education, Inc. Figure 6.10 0.25 m Free ribosomes in cytosol Endoplasmic reticulum (ER) Ribosomes bound to ER Large subunit Small subunit TEM showing ER and ribosomes Diagram of a ribosome Figure 6.10a 0.25 m Free ribosomes in cytosol Endoplasmic reticulum (ER) Ribosomes bound to ER TEM showing ER and ribosomes Concept 6.4: The endomembrane system regulates protein traffic and performs metabolic functions in the cell • Components of the endomembrane system – Nuclear envelope – Endoplasmic reticulum – Golgi apparatus – Lysosomes – Vacuoles – Plasma membrane • These components are either continuous or connected via transfer by vesicles © 2011 Pearson Education, Inc. The Endoplasmic Reticulum: Biosynthetic Factory • The endoplasmic reticulum (ER) accounts for more than half of the total membrane in many eukaryotic cells • The ER membrane is continuous with the nuclear envelope • There are two distinct regions of ER – Smooth ER, which lacks ribosomes – Rough ER, surface is studded with ribosomes © 2011 Pearson Education, Inc. Figure 6.11 Smooth ER Nuclear envelope Rough ER ER lumen Cisternae Transitional ER Ribosomes Transport vesicle 200 nm Smooth ER Rough ER Figure 6.11a Smooth ER Rough ER Nuclear envelope ER lumen Cisternae Transitional ER Ribosomes Transport vesicle Figure 6.11b Smooth ER Rough ER 200 nm Functions of Smooth ER • The smooth ER – Synthesizes lipids – Metabolizes carbohydrates – Detoxifies drugs and poisons – Stores calcium ions © 2011 Pearson Education, Inc. Functions of Rough ER • The rough ER – Has bound ribosomes, which secrete glycoproteins (proteins covalently bonded to carbohydrates) – Distributes transport vesicles, proteins surrounded by membranes – Is a membrane factory for the cell © 2011 Pearson Education, Inc. The Golgi Apparatus: Shipping and Receiving Center • The Golgi apparatus consists of flattened membranous sacs called cisternae • Functions of the Golgi apparatus – Modifies products of the ER – Manufactures certain macromolecules – Sorts and packages materials into transport vesicles © 2011 Pearson Education, Inc. Figure 6.12 cis face (“receiving” side of 0.1 m Golgi apparatus) Cisternae trans face (“shipping” side of TEM of Golgi apparatus Golgi apparatus) Figure 6.12a 0.1 m TEM of Golgi apparatus Lysosomes: Digestive Compartments • A lysosome is a membranous sac of hydrolytic enzymes that can digest macromolecules • Lysosomal enzymes can hydrolyze proteins, fats, polysaccharides, and nucleic acids • Lysosomal enzymes work best in the acidic environment inside the lysosome © 2011 Pearson Education, Inc. Animation: Lysosome Formation Right-click slide / select “Play” © 2011 Pearson Education, Inc. • Some types of cell can engulf another cell by phagocytosis; this forms a food vacuole • A lysosome fuses with the food vacuole and digests the molecules • Lysosomes also use enzymes to recycle the cell’s own organelles and macromolecules, a process called autophagy
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