Chapter 7 Cell Structure And Function PDF

Chapter 7 Cell Structure and Function Lecture Presentations by Nicole Tunbridge and © 2018 Pearson Education Ltd....

Chapter 7 Cell Structure and Function Lecture Presentations by Nicole Tunbridge and © 2018 Pearson Education Ltd. Kathleen Fitzpatrick The Fundamental Units of Life  All organisms are made of cells  The cell is the simplest collection of matter that can be alive  All cells are related by their descent from earlier cells  Cells can differ substantially from one another but share common features © 2018 Pearson Education Ltd. Concept 6.1: Biologists use microscopes and the tools of biochemistry to study cells  Cells are usually too small to be seen by the naked eye © 2018 Pearson Education Ltd. Microscopy  Microscopes are used to visualize cells  In a light microscope (LM), visible light is passed through a specimen and then through glass lenses  Lenses refract (bend) the light so that the image is magnified © 2018 Pearson Education Ltd.  Three important parameters of microscopy:  Magnification, the ratio of an object’s image size to its real size  Resolution, the measure of the clarity of the image, or the minimum distance of two distinguishable points  Contrast, visible differences in brightness between parts of the sample © 2018 Pearson Education Ltd. Figure 6.2a 10 m Human height 1m Length of some Unaided eye nerve and muscle cells 0.1 m Chicken egg 1 cm Frog egg 1 mm LM 100 μm Human egg © 2018 Pearson Education Ltd. Figure 6.2b 100 μm Most plant and animal cells 10 μm Nucleus LM Most bacteria 1 μm Mitochondrion EM 100 nm Smallest bacteria Super- Viruses resolution microscopy Ribosomes 10 nm Proteins Lipids 1 nm Small molecules 0.1 nm Atoms © 2018 Pearson Education Ltd. Figure 6.2c Electron microscopy Super- Light microscopy resolution microscopy Unaided eye Nucleus Length Most Smallest Small of some Most bacteria bacteria Proteins molecules nerve plant Viruses and and Human muscle Chicken Frog Human animal Mito- Ribo- height cells egg egg egg cells chondrion somes Lipids Atoms 10 m 1m 0.1 m 1 cm 1 mm 100 μm 10 μm 1 μm 100 nm 10 nm 1 nm 0.1 nm © 2018 Pearson Education Ltd.  Light microscopes can magnify effectively to about 1,000 times the size of the actual specimen  Various techniques enhance contrast and enable cell components to be stained or labeled  The resolution of standard light microscopy is too low to study organelles, the membrane-enclosed structures in eukaryotic cells © 2018 Pearson Education Ltd. Figure 6.3 Brightfield Brightfield Phase-contrast Differential (unstained 50 μm (stained specimen) interference contrast specimen) (Nomarski) 50 μm 10 μm Fluorescence Confocal Confocal (with) 10 μm (without) Deconvolution 1 μm Super-resolution Super-resolution Scanning Transmission 2 μm 2 μm (without) (with) electron electron microscopy (SEM) microscopy (TEM) © 2018 Pearson Education Ltd.  Two basic types of electron microscopes (EMs) are used to study subcellular structures  Scanning electron microscopes (SEMs) focus a beam of electrons onto the surface of a specimen, providing images that look 3-D  Transmission electron microscopes (TEMs) focus a beam of electrons through a specimen  TEMs are used mainly to study the internal structure of cells © 2018 Pearson Education Ltd.  Recent advances in light microscopy:  Labeling individual cells with fluorescent markers improve the level of detail that can be seen  Confocal microscopy and deconvolution microscopy provide sharper images of three-dimensional tissues and cells  New techniques for labeling cells improve resolution  Super-resolution microscopy allows one to distinguish structures as small as 10–20 nm across © 2018 Pearson Education Ltd. Cell Fractionation  Cell fractionation takes cells apart and separates the major organelles from one another  Centrifuges fractionate cells into their component parts  Cell fractionation enables scientists to determine the functions of organelles  Biochemistry and cytology help correlate cell function with structure © 2018 Pearson Education Ltd. Figure 6.4 Homogenization Tissue cells Homogenate Centrifugation 1,000 g Supernatant poured into next tube 10 min 20,000 g 20 min 80,000 g Pellet rich in 60 min nuclei and cellular debris 150,000 g 3 hr Pellet rich in mitochondria (and chloroplasts) Pellet rich in Differential “microsomes” Pellet rich in centrifugation ribosomes © 2018 Pearson Education Ltd. Figure 6.4a Homogenization Tissue cells Homogenate Centrifugation © 2018 Pearson Education Ltd. Figure 6.4b 1,000 g Supernatant poured into next tube 10 min 20,000 g 20 min 80,000 g Pellet rich in 60 min nuclei and cellular debris 150,000 g 3 hr Pellet rich in mitochondria (and chloroplasts) Pellet rich in Differential “microsomes” Pellet rich in centrifugation ribosomes © 2018 Pearson Education Ltd. 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 © 2018 Pearson Education Ltd. Comparing Prokaryotic and Eukaryotic Cells  Basic features of all cells:  Plasma membrane  Semifluid substance called cytosol  Chromosomes (carry genes)  Ribosomes (make proteins) © 2018 Pearson Education Ltd.  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 © 2018 Pearson Education Ltd. Figure 6.5 Fimbriae Nucleoid Ribosomes Plasma membrane Bacterial Cell wall chromosome Glycocalyx 0.5 μm Flagella (a) A typical rod-shaped (b) A thin section through the bacterium bacterium Corynebacterium diphtheriae (colorized TEM) © 2018 Pearson Education Ltd. Figure 6.5a Nucleoid Ribosomes Plasma membrane Cell wall 0.5 μm (b) A thin section through the bacterium Corynebacterium diphtheriae (colorized TEM) © 2018 Pearson Education Ltd.  Eukaryotic cells are characterized by having  DNA in a nucleus that is bounded by a double membrane  Membrane-bound organelles  Cytoplasm in the region between the plasma membrane and nucleus  Eukaryotic cells are generally much larger than prokaryotic cells © 2018 Pearson Education Ltd.  The plasma membrane is a selective barrier that allows sufficient passage of oxygen, nutrients, and waste to service the volume of every cell © 2018 Pearson Education Ltd. Figure 6.6 Outside of cell (a) TEM of a plasma membrane Inside of cell 0.1 μm Carbohydrate side chains (cytoplasm) Phospholipid Hydrophilic region Hydrophobic region Hydrophilic region Proteins (b) Structure of the plasma membrane © 2018 Pearson Education Ltd. Figure 6.6a Outside of cell Inside of cell 0.1 μm (cytoplasm) (a) TEM of a plasma membrane © 2018 Pearson Education Ltd.  Metabolic requirements set upper limits on the size of cells  The surface area to volume ratio of a cell is critical  As a cell increases in size, its volume grows proportionately more than its surface area © 2018 Pearson Education Ltd. 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 1 125 125 × number of boxes] Surface-to-volume (S-to-V) ratio 6 1.2 6 [surface area ÷ volume] © 2018 Pearson Education Ltd. A Panoramic View of the Eukaryotic Cell  A eukaryotic cell has internal membranes that divide the cell into compartments—the organelles  The basic fabric of biological membranes is a double layer of phospholipids and other lipids  Plant and animal cells have most of the same organelles © 2018 Pearson Education Ltd. Figure 68a ENDOPLASMIC RETICULUM (ER) Nuclear Rough ER Smooth ER envelope Nucleolus NUCLEUS Flagellum Chromatin Centrosome Plasma membrane CYTOSKELETON: Microfilaments Intermediate filaments Microtubules Ribosomes Microvilli Golgi apparatus Peroxisome Lysosome Mitochondrion © 2018 Pearson Education Ltd. Figure 6.8b Nuclear envelope NUCLEUS Nucleolus Rough ER Chromatin Smooth ER Ribosomes Golgi Central vacuole apparatus Microfilaments CYTOSKELETON Microtubules Mitochondrion Peroxisome Plasma membrane Chloroplast Cell wall Plasmodesmata Wall of adjacent cell © 2018 Pearson Education Ltd. 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  Ribosomes use the information from the DNA to make proteins © 2018 Pearson Education Ltd. 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 envelope is a double membrane; each membrane consists of a lipid bilayer © 2018 Pearson Education Ltd. Figure 6.9 1 μm Nucleus Nucleus Nucleolus Chromatin Nuclear envelope: Outer membrane Inner membrane Nuclear pore Rough ER Pore Surface of complex nuclear envelope Ribosome (TEM) Close-up 0.25 μm Chromatin of nuclear envelope 0.5 μm Pore complexes (TEM) Nuclear lamina (TEM) © 2018 Pearson Education Ltd. Figure 6.9a Nucleus Nucleolus Chromatin Nuclear envelope: Outer membrane Inner membrane Nuclear pore Rough ER Pore complex Ribosome Close-up of nuclear Chromatin envelope © 2018 Pearson Education Ltd. Figure 6.9b 1 μm Nuclear envelope: Outer membrane Inner membrane Nuclear pore Surface of nuclear envelope (TEM) © 2018 Pearson Education Ltd. Figure 6.9c 0.25 μm Pore complexes (TEM) © 2018 Pearson Education Ltd. Figure 6.9d 0.5 μm Nuclear lamina (TEM) © 2018 Pearson Education Ltd.  Pores, lined with a structure called a pore complex, regulate the entry and exit of molecules from the nucleus  The nuclear side of the envelope is lined by the nuclear lamina, which is composed of proteins and maintains the shape of the nucleus © 2018 Pearson Education Ltd.  In the nucleus, DNA is organized into discrete units called chromosomes  Each chromosome contains one DNA molecule associated with proteins, 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 © 2018 Pearson Education Ltd. Ribosomes: Protein Factories  Ribosomes are complexes 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) © 2018 Pearson Education Ltd. Figure 6.10 0.25 μm Free ribosomes in cytosol Ribosomes ER Endoplasmic reticulum (ER) Ribosomes bound to ER TEM showing ER and ribosomes Large subunit Small subunit Diagram of Computer model a ribosome of a ribosome © 2018 Pearson Education Ltd. Figure 6.10a 0.25 μm Free ribosomes in cytosol Endoplasmic reticulum (ER) Ribosomes bound to ER TEM showing ER and ribosomes © 2018 Pearson Education Ltd. Figure 7.10b Large subunit Small subunit Computer model of a ribosome © 2018 Pearson Education Ltd. Concept 6.4: The endomembrane system regulates protein traffic and performs metabolic functions in the cell  The endomembrane system consists of  Nuclear envelope  Endoplasmic reticulum  Golgi apparatus  Lysosomes  Vacuoles  Plasma membrane  These components are either continuous or connected via transfer by vesicles © 2018 Pearson Education Ltd. 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, whose surface is studded with ribosomes © 2018 Pearson Education Ltd. Figure 7.11 Smooth ER Rough ER Nuclear envelope Smooth ER Rough ER 0.2 μm ER lumen Cisternae Ribosomes Transitional ER Transport vesicle © 2018 Pearson Education Ltd. Figure 6.11a Smooth ER Rough ER 0.2 μm © 2018 Pearson Education Ltd. Functions of Smooth ER  The smooth ER  Synthesizes lipids  Metabolizes carbohydrates  Detoxifies drugs and poisons  Stores calcium ions © 2018 Pearson Education Ltd. Functions of Rough ER  The rough ER  Has bound ribosomes, which secrete glycoproteins (proteins covalently bonded to carbohydrates)  Distributes transport vesicles, secretory proteins surrounded by membranes  Is a membrane factory for the cell © 2018 Pearson Education Ltd. The Golgi Apparatus: Shipping and Receiving Center  The Golgi apparatus consists of flattened membranous sacs called cisternae  The Golgi apparatus  Modifies products of the ER  Manufactures certain macromolecules  Sorts and packages materials into transport vesicles © 2018 Pearson Education Ltd. Figure 6.12 Golgi apparatus cis face (“receiving” side of 0.1 μm Golgi apparatus) Cisternae trans face (“shipping” side of TEM of Golgi apparatus Golgi apparatus) © 2018 Pearson Education Ltd. Figure 6.12a 0.1 μm TEM of Golgi apparatus © 2018 Pearson Education Ltd. Lysosomes: Digestive Compartments  A lysosome is a membranous sac of hydrolytic enzymes that can digest macromolecules  Lysosomal enzymes work best in the acidic environment inside the lysosome  Hydrolytic enzymes and lysosomal membranes are made by rough ER and then transferred to the Golgi apparatus for further processing © 2018 Pearson Education Ltd.  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 © 2018 Pearson Education Ltd. Figure 6.13 Vesicle containing Nucleus 1 μm two damaged 1 μm organelles Mitochondrion fragment Peroxisome fragment Lysosome Digestive Lysosome enzymes Lysosome Plasma Peroxisome membrane Digestion Food Mitochondrion Digestion vacuole Vesicle (a) Phagocytosis (b) Autophagy © 2018 Pearson Education Ltd. Figure 6.13a Nucleus 1 μm Lysosome Digestive enzymes Lysosome Plasma membrane Digestion Food vacuole (a) Phagocytosis © 2018 Pearson Education Ltd. Figure 6.13aa Nucleus 1 μm © 2018 Pearson Education Ltd. Figure 6.13b Vesicle containing two 1 μm damaged organelles Mitochondrion fragment Peroxisome fragment Lysosome Peroxisome Mitochondrion Digestion Vesicle (b) Autophagy © 2018 Pearson Education Ltd. Figure 6.13ba Vesicle containing two damaged 1 μm organelles Mitochondrion fragment Peroxisome fragment © 2018 Pearson Education Ltd. Vacuoles: Diverse Maintenance Compartments  Vacuoles are large vesicles derived from the ER and Golgi apparatus  Vacuoles perform a variety of functions in different kinds of cells © 2018 Pearson Education Ltd.  Food vacuoles are formed by phagocytosis  Contractile vacuoles, found in many freshwater protists, pump excess water out of cells  Central vacuoles, found in many mature plant cells, hold organic compounds and water © 2018 Pearson Education Ltd. Figure 6.14 Central vacuole Cytosol Central Nucleus vacuole Cell wall Chloroplast 5 μm © 2018 Pearson Education Ltd. Figure 6.14a Cytosol Central Nucleus vacuole Cell wall Chloroplast 5 μm © 2018 Pearson Education Ltd. The Endomembrane System: A Review  The endomembrane system is a complex and dynamic player in the cell’s compartmental organization © 2018 Pearson Education Ltd. Figure 6.15 Nucleus Nuclear envelope Rough ER Smooth ER cis Golgi Plasma membrane trans Golgi © 2018 Pearson Education Ltd. Concept 6.5: Mitochondria and chloroplasts change energy from one form to another  Mitochondria are the sites of cellular respiration, a metabolic process that uses oxygen to generate ATP  Chloroplasts, found in plants and algae, are the sites of photosynthesis  Peroxisomes are oxidative organelles © 2018 Pearson Education Ltd. Mitochondria: Chemical Energy Conversion  Mitochondria are found in nearly all eukaryotic cells  They have a smooth outer membrane and an inner membrane folded into cristae  The inner membrane creates two compartments: intermembrane space and mitochondrial matrix  Some metabolic steps of cellular respiration are catalyzed in the mitochondrial matrix  Cristae present a large surface area for enzymes that synthesize ATP © 2018 Pearson Education Ltd. Figure 6.17 Mitochondrion 10 μm Intermembrane space Mitochondria Outer membrane DNA Inner Free membrane Mitochondrial ribosomes DNA in the Cristae mitochondrial Matrix Nuclear DNA matrix 0.1 μm (a) Diagram and TEM of mitochondrion (b) Network of mitochondria in Euglena (LM) © 2018 Pearson Education Ltd. Figure 6.17a Mitochondrion Intermembrane space Outer membrane DNA Inner Free membrane ribosomes in the Cristae mitochondrial matrix Matrix 0.1 μm (a) Diagram and TEM of mitochondrion © 2018 Pearson Education Ltd. Figure 6.17aa Outer membrane Inner membrane Cristae Matrix 0.1 μm © 2018 Pearson Education Ltd. Figure 6.17b 10 μm Mitochondria Mitochondrial DNA Nuclear DNA (b) Network of mitochondria in Euglena (LM) © 2018 Pearson Education Ltd.