© 2010 Pearson Education, Inc. Lectures by Chris C. Romero, updated by Edward J. Zalisko 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 Chapter 4 A Tour of the Cell

© 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.

Light Micrograph (LM) (for viewing living cells) Light micrograph of a protist, Paramecium LM Colorized SEM Scanning Electron Micrograph (SEM) (for viewing surface features) Scanning electron micrograph of Paramecium TYPES OF MICROGRAPHS Transmission Electron Micrograph (TEM) (for viewing internal structures) Transmission electron micrograph of Paramecium Colorized TEM Figure 4.1 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 Two kinds of electron microscopes reveal different parts of cells.

10 m 1 m 10 cm 1 cm 1 mm 100 um 10 um Human height Chicken egg Frog eggs Length of some nerve and muscle cells Unaided eye Light microscope Plant and animal cells Most bacteria Nucleus Mitochondrion 1 um 100 nm 10 nm 1 nm 0.1 nm Smallest bacteria Viruses Ribosomes Proteins Lipids Small molecules Atoms Electron microscope Figure meter = 1,000 mm 1mm = 1,000 um 1um = 1,000 nm SO 1 meter = 1 Billion nm Or 1 meter = 1x10 9 nm 1nm = 1/1,000 um 1nm = 1/1,000,000mm 1nm = 1/1,000,000,000m

© 2010 Pearson Education, Inc. 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

Plasma membrane (encloses cytoplasm) Cell wall (provides Rigidity) Capsule (sticky coating) Prokaryotic flagellum (for propulsion) Ribosomes (synthesize proteins) Nucleoid (contains DNA) Pili (attachment structures) Colorized TEM Figure 4.4 Prokaryotes

© 2010 Pearson Education, Inc. 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

Cytoskeleton RibosomesCentriole Lysosome Flagellum Nucleus Plasma membrane Mitochondrion Rough endoplasmic reticulum (ER) Golgi apparatus Smooth endoplasmic reticulum (ER) Idealized animal cell Idealized plant cell Cytoskeleton Mitochondrion Nucleus Rough endoplasmic reticulum (ER) Ribosomes Smooth endoplasmic reticulum (ER) Golgi apparatus Plasma membrane Channels between cells Not in most plant cells Central vacuole Cell wall Chloroplast Not in animal cells Figure 4.5

© 2010 Pearson Education, Inc. MEMBRANE STRUCTURE The plasma membrane separates the living cell from its nonliving surroundings.

The Plasma Membrane: A Fluid Mosaic of Lipids and Proteins The membranes of cells are composed mostly of –Lipids –Proteins © 2010 Pearson Education, Inc.

(a) Phospholipid bilayer of membrane (b) Fluid mosaic model of membrane Outside of cell Hydrophilic head Hydrophobic tail Hydrophilic region of protein Hydrophilic head Hydrophobic tail Hydrophobic regions of protein Phospholipid bilayer Phospholipid Proteins Cytoplasm (inside of cell) Figure 4.6

© 2010 Pearson Education, Inc. 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

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.

Ribosomes Chromatin Nucleolus Pore Nuclear envelope Surface of nuclear envelopeNuclear pores TEM Figure 4.8

© 2010 Pearson Education, Inc. 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.

DNA molecule Chromosome Proteins Chromatin fiber Figure 4.9

© 2010 Pearson Education, Inc. 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.

Synthesis of mRNA in the nucleus Nucleus DNA mRNA Cytoplasm mRNA Movement of mRNA into cytoplasm via nuclear pore Ribosome Protein Synthesis of protein in the cytoplasm Figure

© 2010 Pearson Education, Inc. 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

Nuclear envelope Smooth ER Rough ER Ribosomes TEM Figure 4.13

© 2010 Pearson Education, Inc. 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.

Proteins are often modified in the ER. Secretory proteins depart in transport vesicles. Vesicles bud off from the ER. A ribosome links amino acids into a polypeptide. Ribosome Transport vesicle Polypeptide Protein Rough ER Figure 4.14

© 2010 Pearson Education, Inc. 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

Vacuole filling with water Vacuole contracting (a) Contractile vacuole in Paramecium (b) Central vacuole in a plant cell Central vacuole Colorized TEM LM 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.

Inner and outer membranes Space between membranes Stroma (fluid in chloroplast) Granum TEM Figure 4.19

© 2010 Pearson Education, Inc. 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 usable energy

Outer membrane Inner membrane Cristae Matrix Space between membranes TEM Figure 4.20

© 2010 Pearson Education, Inc. 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.

(a) Microtubules in the cytoskeleton (b) Microtubules and movement LM Figure 4.21

© 2010 Pearson Education, Inc. 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.

(a) Flagellum of a human sperm cell Colorized SEM (b) Cilia on a protist (c) Cilia lining the respiratory tract Colorized SEM Figure 4.22

© 2010 Pearson Education, Inc. Cilia may extend from nonmoving cells. On cells lining the human trachea, cilia help sweep mucus out of the lungs.

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© 2010 Pearson Education, Inc. Figure 4.UN1 Plasma membrane

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© 2010 Pearson Education, Inc. Figure 4.UN2 Nucleus

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© 2010 Pearson Education, Inc. Figure 4.UN3 Ribosome

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© 2010 Pearson Education, Inc. Figure 4.UN4 Endoplasmic reticulum

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© 2010 Pearson Education, Inc. Figure 4.UN7 Vacuole

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© 2010 Pearson Education, Inc. Figure 4.UN8 Chloroplast

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© 2010 Pearson Education, Inc. Figure 4.UN9 Mitochondrion

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© 2010 Pearson Education, Inc. Figure 4.UN10 Cytoskeleton

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© 2010 Pearson Education, Inc. Figure 4.UN11 Cilia and flagella