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Chapter 4 A Tour of the Cell PowerPoint® Lectures for Campbell Essential Biology, Fourth Edition – Eric Simon, Jane Reece, and Jean Dickey Campbell Essential Biology with Physiology, Third Edition – Eric Simon, Jane Reece, and Jean Dickey Lectures by Chris C. Romero, updated by Edward J. Zalisko © 2010 Pearson Education, Inc. • Cells were first described in 1665 by Robert Hooke. • 200 years later, the accumulation of scientific evidence led to the cell theory. – All living things are composed of cells. – All cells come from other cells. © 2010 Pearson Education, Inc. The electron microscope (EM) uses a beam of electrons, which results in better resolving power than the light microscope. The electron microscope can Magnify up to 100,000 times Distinguish between objects 0.2 nanometers apart TYPES OF MICROGRAPHS Light micrograph of a protist, Paramecium Transmission Electron Micrograph (TEM) (for viewing internal structures) Colorized SEM Colorized TEM Scanning Electron Micrograph (SEM) (for viewing surface features) LM Light Micrograph (LM) (for viewing living cells) Scanning electron micrograph of Paramecium Transmission electron micrograph of Paramecium Two kinds of electron microscopes reveal different parts of cells. Figure 4.1 10 m 1m Length of some nerve and muscle cells 10 cm Chicken egg Unaided eye Human height 1nm = 1/1,000 um 1 cm 1nm = 1/1,000,000mm Frog eggs 1 mm Plant and animal cells 1mm = 1,000 um 10 um 1um = 1,000 nm 1 um SO 100 nm Nucleus Most bacteria Mitochondrion Smallest bacteria Viruses Ribosomes 1 meter = 1 Billion nm Or 1 meter = 1x109 nm 10 nm 1nm = 1/1,000,000,000m Electron microscope 100 um Light microscope 1 meter = 1,000 mm Proteins Lipids 1 nm 0.1 nm Small molecules Atoms Figure 4.3 The Two Major Categories of Cells • The countless cells on earth fall into two categories: – Prokaryotic cells — Bacteria and Archaea – Eukaryotic cells — protists, plants, fungi, and animals • All cells have several basic features. – They are all bound by a thin plasma membrane. – All cells have DNA and ribosomes, tiny structures that build proteins. © 2010 Pearson Education, Inc. • Prokaryotic and eukaryotic cells have important differences. • Prokaryotic cells are older than eukaryotic cells. – Prokaryotes appeared about 3.5 billion years ago. – Eukaryotes appeared about 2.1 billion years ago. © 2010 Pearson Education, Inc. • Prokaryotes – Are smaller than eukaryotic cells – Lack internal structures surrounded by membranes – Lack a nucleus – Have a rigid cell wall © 2010 Pearson Education, Inc. Prokaryotes Plasma membrane (encloses cytoplasm) Cell wall (provides Rigidity) Capsule (sticky coating) Colorized TEM Prokaryotic flagellum (for propulsion) Ribosomes (synthesize proteins) Nucleoid (contains DNA) Pili (attachment structures) Figure 4.4 • Eukaryotes – Only eukaryotic cells have organelles, membrane-bound structures that perform specific functions. – The most important organelle is the nucleus, which houses most of a eukaryotic cell’s DNA. © 2010 Pearson Education, Inc. An Overview of Eukaryotic Cells • Eukaryotic cells are fundamentally similar. • The region between the nucleus and plasma membrane is the cytoplasm. • The cytoplasm consists of various organelles suspended in fluid. © 2010 Pearson Education, Inc. • Unlike animal cells, plant cells have – Protective cell walls – Chloroplasts, which convert light energy to the chemical energy of food © 2010 Pearson Education, Inc. Ribosomes Cytoskeleton Centriole Lysosome Flagellum Not in most plant cells Plasma membrane Nucleus Mitochondrion Rough endoplasmic reticulum (ER) Golgi apparatus Cytoskeleton Mitochondrion Nucleus Rough endoplasmic reticulum (ER) Idealized animal cell Smooth endoplasmic reticulum (ER) Central vacuole Cell wall Not in animal cells Chloroplast Ribosomes Plasma membrane Smooth endoplasmic reticulum (ER) Channels between cells Idealized plant cell Golgi apparatus Figure 4.5 MEMBRANE STRUCTURE • The plasma membrane separates the living cell from its nonliving surroundings. © 2010 Pearson Education, Inc. The Plasma Membrane: A Fluid Mosaic of Lipids and Proteins • The membranes of cells are composed mostly of – Lipids – Proteins © 2010 Pearson Education, Inc. Outside of cell Hydrophilic head Hydrophobic tail Hydrophilic region of protein Outside of cell Hydrophilic head Proteins Phospholipid bilayer Hydrophobic tail Phospholipid Cytoplasm (inside of cell) (a) Phospholipid bilayer of membrane Hydrophobic regions of protein Cytoplasm (inside of cell) (b) Fluid mosaic model of membrane Figure 4.6 • Most membranes have specific proteins embedded in the phospholipid bilayer. • These proteins help regulate traffic across the membrane and perform other functions. “selective permeability” © 2010 Pearson Education, Inc. Cell Surfaces • Plant cells have rigid cell walls surrounding the membrane. • Plant cell walls – Are made of cellulose – Protect the cells – Maintain cell shape – Keep the cells from absorbing too much water © 2010 Pearson Education, Inc. THE NUCLEUS AND RIBOSOMES: GENETIC CONTROL OF THE CELL • The nucleus is the chief executive of the cell. – Genes in the nucleus store information necessary to produce proteins. – Proteins do most of the work of the cell. © 2010 Pearson Education, Inc. Structure and Function of the Nucleus • The nucleus is bordered by a double membrane called the nuclear envelope. • Pores in the envelope allow materials to move between the nucleus and cytoplasm. • The nucleus contains a nucleolus where ribosomes are made. © 2010 Pearson Education, Inc. Nuclear envelope Nucleolus Pore TEM Chromatin TEM Ribosomes Surface of nuclear envelope Nuclear pores Figure 4.8 • Stored in the nucleus are long DNA molecules and associated proteins that form fibers called chromatin. • Each long chromatin fiber constitutes one chromosome. • The number of chromosomes in a cell depends on the species. © 2010 Pearson Education, Inc. DNA molecule Proteins Chromatin fiber Chromosome Figure 4.9 Ribosomes • Ribosomes are responsible for protein synthesis. • Ribosome components are made in the nucleolus but assembled in the cytoplasm. © 2010 Pearson Education, Inc. • Ribosomes may assemble proteins: – Suspended in the fluid of the cytoplasm or – Attached to the outside of an organelle called the endoplasmic reticulum © 2010 Pearson Education, Inc. How DNA Directs Protein Production • DNA directs protein production by transferring its coded information into messenger RNA (mRNA). • Messenger RNA exits the nucleus through pores in the nuclear envelope. • A ribosome moves along the mRNA translating the genetic message into a protein with a specific amino acid sequence. © 2010 Pearson Education, Inc. DNA Synthesis of mRNA in the nucleus mRNA Nucleus Cytoplasm Movement of mRNA into cytoplasm via nuclear pore Synthesis of protein in the cytoplasm mRNA Ribosome Protein Figure 4.12-3 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 composed of smooth and rough ER © 2010 Pearson Education, Inc. Nuclear envelope Ribosomes TEM Rough ER Smooth ER Ribosomes Figure 4.13 Rough ER • The “rough” in the rough ER is due to ribosomes that stud the outside of the ER membrane. • These ribosomes produce membrane proteins and secretory proteins. • After the rough ER synthesizes a molecule, it packages the molecule into transport vesicles. © 2010 Pearson Education, Inc. Proteins are often modified in the ER. Secretory proteins depart in transport vesicles. Ribosome Vesicles bud off from the ER. Transport vesicle Protein A ribosome links amino acids into a polypeptide. Rough ER Polypeptide Figure 4.14 Vacuoles • Vacuoles are membranous sacs that bud from the – ER – Golgi – Plasma membrane • Contractile vacuoles of protists pump out excess water in the cell. • Central vacuoles of plants – Store nutrients – Absorb water – May contain pigments or poisons © 2010 Pearson Education, Inc. LM Vacuole filling with water LM Vacuole contracting Colorized TEM (a) Contractile vacuole in Paramecium Central vacuole (b) Central vacuole in a plant cell Figure 4.17 CHLOROPLASTS AND MITOCHONDRIA: ENERGY CONVERSION • Cells require a constant energy supply to perform the work of life. © 2010 Pearson Education, Inc. 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. • Chloroplasts are the organelles that perform photosynthesis. © 2010 Pearson Education, Inc. Inner and outer membranes Space between membranes Granum TEM Stroma (fluid in chloroplast) Figure 4.19 Mitochondria • Mitochondria are the sites of cellular respiration, which produce ATP from the energy of food molecules. • Mitochondria are found in almost all eukaryotic cells. chemical energy © 2010 Pearson Education, Inc. usable energy TEM Outer membrane Inner membrane Cristae Matrix Space between membranes Figure 4.20 Maintaining Cell Shape • The cytoskeleton – Provides mechanical support to the cell – Maintains its shape © 2010 Pearson Education, Inc. • The cytoskeleton contains several types of fibers made from different proteins: – Microtubules – Are straight and hollow – Guide the movement of organelles and chromosomes – Intermediate filaments and microfilaments are thinner and solid. © 2010 Pearson Education, Inc. LM (a) Microtubules in the cytoskeleton LM (b) Microtubules and movement Figure 4.21 Cilia and Flagella • Cilia and flagella aid in movement. – Flagella propel the cell in a whiplike motion. – Cilia move in a coordinated back-and-forth motion. – Cilia and flagella have the same basic architecture. © 2010 Pearson Education, Inc. Colorized SEM (a) Flagellum of a human sperm cell Colorized SEM Colorized SEM (b) Cilia on a protist (c) Cilia lining the respiratory tract Figure 4.22 • Cilia may extend from nonmoving cells. • On cells lining the human trachea, cilia help sweep mucus out of the lungs. © 2010 Pearson Education, Inc. Figure 4.UN1 Plasma membrane © 2010 Pearson Education, Inc. Figure 4.UN1 Figure 4.UN2 Nucleus © 2010 Pearson Education, Inc. Figure 4.UN2 Figure 4.UN3 Ribosome © 2010 Pearson Education, Inc. Figure 4.UN3 Figure 4.UN4 Endoplasmic reticulum © 2010 Pearson Education, Inc. Figure 4.UN4 Figure 4.UN7 Vacuole © 2010 Pearson Education, Inc. Figure 4.UN7 Figure 4.UN8 Chloroplast © 2010 Pearson Education, Inc. Figure 4.UN8 Figure 4.UN9 Mitochondrion © 2010 Pearson Education, Inc. Figure 4.UN9 Figure 4.UN10 Cytoskeleton © 2010 Pearson Education, Inc. Figure 4.UN10 Figure 4.UN11 Cilia and flagella © 2010 Pearson Education, Inc. Figure 4.UN11