A Tour of the Cell Lecture 3, Chapter 4 PDF

Lecture 3 Chapter 4 A Tour of the Cell PowerPoint® Lectures created by Edward J. Zalisko for Campbell Essential Biology, Sixth Edition, Global Edition, and Campbell Essential Biology with Physiology, Fifth Edition, Global Edition – Eric J. Simon, Jean L. Dick...

Lecture 3 Chapter 4 A Tour of the Cell PowerPoint® Lectures created by Edward J. Zalisko for Campbell Essential Biology, Sixth Edition, Global Edition, and Campbell Essential Biology with Physiology, Fifth Edition, Global Edition – Eric J. Simon, Jean L. Dickey, Kelly A. Hogan, and Jane B. Reece © 2017 Pearson Education, Ltd. © 2017 Pearson Education, Ltd.  The Microscopic World of Cells Organisms are either Single-celled, such as most prokaryotes (like Bacteria) and protists, or Multicelled, such as plants, animals, and most fungi. The human body is cooperative society of trillions of cells of many specialized types © 2017 Pearson Education, Ltd. Figure 4.1 10 m Human height 1m Length of some nerve and muscle cells 10 cm Chicken egg Visible with the naked eye 1 cm Frog eggs 1 mm 100 mm Plant and animal cells 10 mm Most cells are between Visible only with a Nuclei 1 and100 μm in diameter microscope Most bacteria 1 mm Mitochondria Measurement Equivalents Smallest bacteria 1 meter (m) = 100 cm = 1,000 mm = about 39.4 inches 100 nm Viruses 2 1 1 centimeter (cm) = 10 100 m = about 0.4 inch Ribosomes 10 nm 1 1 Proteins 1 millimeter (mm) = 103 1,000 m = 10 cm Lipids 1 nm 6 3 Small molecules 1 micrometer (mm) = 10 m = 10 mm 0.1 nm Atoms 1 nanometer (nm) = 109 m = 103 µm © 2017 Pearson Education, Ltd.  The Microscopic World of Cells How do new living cells arise? The cell theory states that all living things are composed of cells and that all cells come from earlier cells. So every cell in your body (and in every other living organism on Earth) was formed by division of a previously living cell. © 2017 Pearson Education, Ltd.  The Two Major Categories of Cells The countless cells on Earth fall into two basic categories. Prokaryotic cells include Bacteria and Archaea. Eukaryotic cells include 1. protists, 2. plants, 3. fungi, and 4. animals. © 2017 Pearson Education, Ltd. Table 4.1 © 2017 Pearson Education, Ltd.  The Two Major Categories of Cells All cells have several common features. They are all bounded by a thin plasma membrane. Inside all cells is a thick, jelly-like fluid called the cytosol, in which cellular components are suspended. All cells have one or more chromosomes carrying genes made of DNA. All cells have ribosomes, tiny structures that build proteins according to the instructions from the genes. © 2017 Pearson Education, Ltd.  The Two Major Categories of Cells Eukaryotic cells Only eukaryotic cells have organelles, membrane- enclosed structures that perform specific functions. The most important organelle is the nucleus, which houses most of a eukaryotic cell’s DNA and is surrounded by a double membrane. A prokaryotic cell lacks a nucleus. Its DNA is coiled into a nucleus-like region called the nucleoid, which is not partitioned from the rest of the cell by membranes. © 2017 Pearson Education, Ltd.  Prokaryotic cells Surrounding the plasma membrane of most prokaryotic cells is a rigid cell wall, which protects the cell and helps maintain its shape. Prokaryotes can have short projections called pili, which can also attach to surfaces, and/or flagella, long projections that propel them through their liquid environment. © 2017 Pearson Education, Ltd. Figure 4.2 Plasma membrane (encloses cytoplasm) Cell wall (provides rigidity) Capsule (sticky coating) Flagella (for propulsion) Ribosomes (synthesize proteins) Colorized TEM Nucleoid (contains single circular bacterial chromosome) Pili (attachment structures) © 2017 Pearson Education, Ltd.  Eukaryotic Cells Eukaryotic cells are fundamentally similar. The region between the nucleus and plasma membrane is the cytoplasm. The cytoplasm of a eukaryotic cell consists of various organelles suspended in the liquid cytosol. Most organelles are found in both animal and plant cells. But there are some important differences. Only plant cells have chloroplasts (where photosynthesis occurs). Only animal cells have lysosomes (bubbles of digestive enzymes surrounded by membranes). © 2017 Pearson Education, Ltd. Figure 4.3 IDEALIZED ANIMAL CELL Centriole Not in most Ribosomes plant cells Lysosome Cytoskeleton Plasma membrane Nucleus Cytoplasm Mitochondrion Rough endoplasmic Smooth reticulum (ER) endoplasmic IDEALIZED PLANT CELL Golgi reticulum (ER) Cytoplasm apparatus Cytoskeleton Mitochondrion Central vacuole Not in Cell wall animal cells Nucleus Chloroplast Rough endoplasmic reticulum (ER) Ribosomes Plasma membrane Smooth endoplasmic Channels between cells reticulum (ER) Golgi apparatus © 2017 Pearson Education, Ltd.  Structure/Function: The Plasma Membrane The plasma membrane separates the living cell from its nonliving surroundings. The plasma membrane and other membranes of the cell are composed mostly of phospholipids, which group together to form a two-layer sheet called a phospholipid bilayer. Each phospholipid is composed of two distinct regions: 1. a “head” with a negatively charged phosphate group and 2. two nonpolar fatty acid “tails.” © 2017 Pearson Education, Ltd. Figure 4.4-1 Outside of cell Hydrophilic head Hydrophobic tail Phospholipid Cytoplasm (inside of cell) (a) Phospholipid bilayer of membrane © 2017 Pearson Education, Ltd.  Structure/Function: The Plasma Membrane Suspended in the phospholipid bilayer of most membranes are proteins that help regulate traffic across the membrane and perform other functions. The plasma membrane is a fluid mosaic: fluid because molecules can move freely past one another and a mosaic because of the diversity of proteins in the membrane. © 2017 Pearson Education, Ltd. Figure 4.4-2 Embedded Outside of cell proteins Phospholipid Hydrophilic bilayer head Hydrophobic tail Cytoplasm (inside of cell) (b) Fluid mosaic model of membrane © 2017 Pearson Education, Ltd.  Cell Surfaces Surrounding their plasma membranes, plant cells have a cell wall made from cellulose fibers. Plant cell walls protect the cells, maintain cell shape, and keep cells from absorbing too much water. © 2017 Pearson Education, Ltd.  Cell Surfaces Animal cells lack cell walls and most secrete a sticky coat called the extracellular matrix. Fibers made of the protein collagen hold cells together in tissues and can have protective and supportive functions. In addition, the surfaces of most animal cells contain cell junctions, structures that connect cells together into tissues, allowing the cells to function in a coordinated way. © 2017 Pearson Education, Ltd.  The Nucleus and Ribosomes: Genetic Control of the Cell The nucleus is the control center of the cell. Each gene is a stretch of DNA that stores the information necessary to produce a particular protein. The nucleus is separated from the cytoplasm by a double membrane called the nuclear envelope. Pores in the envelope allow certain materials to pass between the nucleus and the surrounding cytoplasm © 2017 Pearson Education, Ltd.  The Nucleus Within the nucleus, long DNA molecules and associated proteins form fibers called chromatin. Each long chromatin fiber constitutes one chromosome. The nucleolus is a prominent structure within the nucleus and the site where the components of ribosomes are made. © 2017 Pearson Education, Ltd. Figure 4.6 Nuclear Nuclear Chromatin fiber envelope Nucleolus pore TEM TEM Surface of nuclear envelope Nuclear pores © 2017 Pearson Education, Ltd. Figure 4.7 DNA molecule Proteins Chromatin fiber Chromosome © 2017 Pearson Education, Ltd.  Ribosomes Ribosomes are responsible for protein synthesis. In eukaryotic cells, the components of ribosomes are made in the nucleus (specifically the nucleolus) and then transported through the pores of the nuclear envelope into the cytoplasm, where ribosomes begin their work. © 2017 Pearson Education, Ltd. Figure 4.8 Ribosome mRNA Protein © 2017 Pearson Education, Ltd.  Ribosomes Although structurally identical, some ribosomes are: suspended in the cytosol, making proteins that remain within the fluid of the cell. Others are: attached to the outside of the nucleus or an organelle called the endoplasmic reticulum (ER), making proteins that are incorporated into membranes or secreted by the cell. © 2017 Pearson Education, Ltd. Figure 4.9 TEM Ribosomes attached to endoplasmic reticulum visible as tiny dark blue dots © 2017 Pearson Education, Ltd.  How DNA Directs Protein Production DNA transfers its coded information to a molecule called messenger RNA (mRNA). mRNA exits the nucleus through pores in the nuclear envelope and travels to the cytoplasm, where it binds to a ribosome. A ribosome moves along the mRNA, translating the genetic message into a protein with a specific amino acid sequence. © 2017 Pearson Education, Ltd. Figure 4.10-s3 DNA 1 Synthesis of mRNA in the nucleus mRNA Nucleus https://www.youtube.co m/watch?v=oCp9IK6iB Cytoplasm To&t=5s 2 Movement of mRNA mRNA into Ribosome cytoplasm via nuclear pore 3 Synthesis of protein in the cytoplasm Protein © 2017 Pearson Education, Ltd.  The Endomembrane System: Manufacturing and Distributing Cellular Products The endomembrane system in a cell consists of the nuclear envelope, the endoplasmic reticulum, the Golgi apparatus, lysosomes, and vacuoles. These membranous organelles are either physically connected or linked by vesicles, sacs made of membrane. © 2017 Pearson Education, Ltd.  The Endoplasmic Reticulum The endoplasmic reticulum (ER) is one of the main manufacturing facilities in a cell. The ER produces an enormous variety of molecules, is connected to the nuclear envelope, and is composed of interconnected rough and smooth ER that have different structures and functions. © 2017 Pearson Education, Ltd. © 2017 Pearson Education, Ltd.  Rough ER The “rough” in rough ER refers to ribosomes that stud the outside of its membrane. The ER makes more membrane: Phospholipids made by enzymes of the rough ER are inserted into the ER membrane. In this way, the ER membrane grows, and portions of it can bubble off and be transferred to other parts of the cell. Ribosomes attached to the rough ER produce proteins that will be inserted into the growing ER membrane, transported to other organelles, and eventually exported. © 2017 Pearson Education, Ltd.  Rough ER Some products manufactured by rough ER are chemically modified and then packaged into transport vesicles, sacs made of membrane that bud off from the rough ER. Then these transport vesicles may be dispatched to other locations in the cell. © 2017 Pearson Education, Ltd. © 2017 Pearson Education, Ltd.  Smooth ER The smooth ER lacks surface ribosomes, produces lipids, including steroids the cells in ovaries or testes that produce the steroid sex hormones are enriched with smooth ER. helps liver cells detoxify circulating drugs As liver cells are exposed to a drug, the amounts of smooth ER and its detoxifying enzymes increase. © 2017 Pearson Education, Ltd.  The Golgi Apparatus The Golgi apparatus works in partnership with the ER and receives, refines, stores, and distributes chemical products of the cell. The Golgi apparatus consists of a stack of membrane plates. Products made in the ER reach the Golgi apparatus in transport vesicles. Proteins within a vesicle are usually modified by enzymes during their transit from the receiving to the shipping side of the Golgi apparatus. The shipping side of a Golgi stack is a depot from which finished products can be carried in transport vesicles to other organelles or to the plasma membrane. © 2017 Pearson Education, Ltd. © 2017 Pearson Education, Ltd.  Lysosomes A lysosome is a membrane-enclosed sac of digestive enzymes found in animal cells. Most plant cells do not contain lysosomes. Enzymes in a lysosome can break down large molecules such as proteins, polysaccharides, fats, and nucleic acids. © 2017 Pearson Education, Ltd.  Lysosomes Lysosomes have several types of digestive functions. Many single-celled protists engulf nutrients in tiny cytoplasmic sacs called food vacuoles. Lysosomes fuse with the food vacuoles, exposing the food to digestive enzymes. Small molecules that result from this digestion, such as amino acids, leave the lysosome and nourish the cell. © 2017 Pearson Education, Ltd. Figure 4.14-1 Digestive enzymes Lysosome Digestion Food vacuole Plasma membrane (a) A lysosome digesting food © 2017 Pearson Education, Ltd.  Lysosomes Lysosomes can also destroy harmful bacteria For instance, your white blood cells ingest bacteria into vacuoles, and lysosomal enzymes that are emptied into these vacuoles rupture the bacterial cell wall engulf and digest parts of another organelle sculpt tissues during embryonic development, helping to form structures such as fingers In an early human embryo, lysosomes release enzymes that digest webbing between fingers of the developing hand. © 2017 Pearson Education, Ltd. Figure 4.14-2 Lysosome Digestion Vesicle containing damaged organelle (b) A lysosome breaking down the molecules of damaged organelles © 2017 Pearson Education, Ltd.  Lysosomes The importance of lysosomes to cell function and human health is made clear by hereditary disorders called lysosomal storage diseases. A person with such a disease is missing one or more of the digestive enzymes normally found within lysosomes and has lysosomes that become engorged with indigestible substances, which eventually interfere with other cellular functions Ex: In Tay-Sachs disease, lysosomes lack a lipid-digesting enzyme. As a result, nerve cells die as they accumulate excess lipids, ravaging the nervous system. Most of these diseases are fatal in early childhood. © 2017 Pearson Education, Ltd.  Vacuoles Vacuoles are large sacs made of membrane that bud off from the ER or Golgi apparatus. Vacuoles have a variety of functions food vacuoles bud from the plasma membrane certain freshwater protists have contractile vacuoles that pump out excess water that flows into the cell from the outside environment. © 2017 Pearson Education, Ltd. Figure 4.15-1 A vacuole filling with water LM A vacuole contracting LM (a) Contractile vacuole in Paramecium © 2017 Pearson Education, Ltd.  Vacuoles A central vacuole can account for more than half the volume of a mature plant cell. The central vacuole of a plant cell is a versatile compartment that may store organic nutrients, absorb water, and contain pigments that attract pollinating insects or poisons that protect against plant-eating animals. © 2017 Pearson Education, Ltd. Figure 4.15-2 Colorized TEM Central vacuole (b) Central vacuole in a plant cell © 2017 Pearson Education, Ltd. © 2017 Pearson Education, Ltd.  Energy Transformations: Chloroplasts and Mitochondria One of the central themes of biology is the transformation of energy: how it enters living systems, is converted from one form to another, and is eventually given off as heat. Two organelles act as cellular power stations: 1. chloroplasts 2. mitochondria © 2017 Pearson Education, Ltd.  Chloroplasts Most of the living world runs on the energy provided by photosynthesis. Photosynthesis is the conversion of light energy from the sun to the chemical energy of sugar and other organic molecules. Chloroplasts are unique to the photosynthetic cells of plants and algae and the organelles that perform photosynthesis. © 2017 Pearson Education, Ltd.  Chloroplasts Chloroplasts are divided into compartments by two membranes, one inside the other (double-membrane envelope). The stroma is a thick fluid found inside the innermost membrane. Suspended in that fluid is a network of membrane-enclosed disks (thylakoids) and tubes, which form another compartment. Thylakoids occur in interconnected stacks called grana (singular granum) that resemble stacks of poker chips These structures contain the green pigment chlorophyll which absorbs energy from the sun  photosynthetic pigments The grana are a chloroplast’s solar power packs, the structures that trap light energy and convert it to chemical energy. © 2017 Pearson Education, Ltd. Figure 4.17 Inner and outer membranes Space between membranes Stroma (fluid in Granum chloroplast) © 2017 Pearson Education, Ltd. TEM  Mitochondria Mitochondria are found in almost all eukaryotic cells, are the organelles in which cellular respiration takes place, and produce ATP from the energy of food molecules. Cells use molecules of ATP as the direct energy source for most of their work. © 2017 Pearson Education, Ltd.  Mitochondria Found in almost all eukaryotic cells, including those of plants and animals. Like chloroplasts, mitochondria have an envelope of two membranes (double-membrane envelope), and the inner membrane encloses a thick fluid called the mitochondrial matrix. The inner membrane of the envelope has numerous infoldings called cristae. The folded surface of the membrane includes many of the enzymes and other molecules that function in cellular respiration and creates a greater area for the chemical reactions of cellular respiration. during cellular respiration, energy is harvested from sugars and transformed into another form of chemical energy called ATP (adenosine triphosphate) (more in Chapter 6). © 2017 Pearson Education, Ltd. Figure 4.18 TEM Outer membrane Inner membrane Cristae Matrix Space between membranes © 2017 Pearson Education, Ltd.  Mitochondria Mitochondria and chloroplasts contain their own DNA that encodes some of their own proteins made by their own ribosomes. Each chloroplast and mitochondrion contains a single circular DNA chromosome that resembles a prokaryotic chromosome and can grow and pinch in two, reproducing themselves. © 2017 Pearson Education, Ltd.  Mitochondria This is evidence that mitochondria and chloroplasts evolved from ancient free-living prokaryotes that established residence within other, larger host prokaryotes. This phenomenon, where one species lives inside a host species, is a special type of symbiosis. Over time, mitochondria and chloroplasts likely became increasingly interdependent with the host prokaryote, eventually evolving into a single organism with inseparable parts. The DNA found within mitochondria and chloroplasts is therefore likely remnants of this ancient evolutionary event. © 2017 Pearson Education, Ltd.  The Cytoskeleton Cells have an infrastructure called the cytoskeleton: a network of protein fibers extending throughout the cytoplasm. The cytoskeleton serves as both skeleton and “muscles” for the cell, functioning in support and movement. The cytoskeleton provides mechanical support to the cell and helps a cell maintain its shape. This is especially important for animal cells, which lack rigid cell walls. © 2017 Pearson Education, Ltd.  The Cytoskeleton The cytoskeleton contains several types of fibers made from different proteins. Microtubules are hollow tubes of protein. The other kinds of cytoskeletal fibers, called intermediate filaments and microfilaments, are thinner and solid. The cytoskeleton provides anchorage and reinforcement for many organelles in a cell The nucleus is held in place by a “cage” of cytoskeletal filaments. Other organelles use the cytoskeleton for movement. For example, a lysosome might reach a food vacuole by gliding along a microtubule track. Microtubules also guide the movement of chromosomes when cells divide © 2017 Pearson Education, Ltd. Figure 4.19-1 LM (a) Microtubules in the cytoskeleton © 2017 Pearson Education, Ltd.  The Cytoskeleton A cell’s cytoskeleton is dynamic. It can be quickly dismantled in one part of the cell by removing protein subunits and re-formed in a new location by reattaching the subunits. Such rearrangement can provide rigidity in a new location, change the shape of the cell, or even cause the whole cell or some of its parts to move. This process contributes to the amoeboid (crawling) movements of the protist Amoeba and movement of some of our white blood cells. © 2017 Pearson Education, Ltd. © 2017 Pearson Education, Ltd.  Cilia and Flagella In some eukaryotic cells, microtubules are arranged into structures called flagella and cilia, extensions from a cell that aid in movement. Eukaryotic flagella propel cells through an undulating, whiplike motion. They often occur singly, such as in human sperm cells, but may also appear in groups on the outer surface of protists. © 2017 Pearson Education, Ltd. Figure 4.20-1 (a) Flagellum of a human sperm cell © 2017 Pearson Education, Ltd. Colorized SEM  Cilia and Flagella Cilia (singular, cilium) are generally shorter and more numerous than flagella and move in a coordinated back-and-forth motion, like the rhythmic oars of a crew team. Both cilia and flagella propel various protists through water. Cilia may extend from nonmoving cells. On cells lining the human trachea, cilia help sweep mucus with trapped debris out of the lungs. © 2017 Pearson Education, Ltd. Figure 4.20-2 Colorized SEM (b) Cilia on a protist © 2017 Pearson Education, Ltd.  Animation: Cilia and Flagella © 2017 Pearson Education, Ltd. Figure 4.20-3 Colorized SEM (c) Cilia lining the respiratory tract © 2017 Pearson Education, Ltd.  Cilia and Flagella Because human sperm rely on flagella for movement, it is easy to understand why problems with flagella can lead to male infertility. Some men with a type of hereditary sterility also suffer from respiratory problems because of a defect in the structure of their flagella and cilia. © 2017 Pearson Education, Ltd.