Chapter 6 A Tour of the Cell

Fig. 6-1 Figure 6.1 How do cellular components cooperate to help the cell function?

Microscopy Scientists use microscopes to visualize cells too small to see with the naked eye In a light microscope (LM), this is the type of scope you use, which magnifies about up to 1,000x the actual size The quality of an image depends on 3 things: Magnification Resolution (clarity) Contrast (visible differences), can be enhanced with stains Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

10 m 1 m 0.1 m 1 cm 1 mm 100 µm 10 µm 1 µm 100 nm 10 nm 1 nm 0.1 nm Fig. 6-2 10 m Human height 1 m Length of some nerve and muscle cells 0.1 m Unaided eye Chicken egg 1 cm Frog egg 1 mm 100 µm Most plant and animal cells Light microscope 10 µm Nucleus Most bacteria 1 µm Mitochondrion Figure 6.2 The size range of cells Smallest bacteria Electron microscope 100 nm Viruses Ribosomes 10 nm Proteins Lipids 1 nm Small molecules 0.1 nm Atoms

Cheek epithelial cells Fig. 6-3 TECHNIQUE RESULTS (a) Brightfield (unstained specimen) Cheek epithelial cells 50 µm (b) Brightfield (stained specimen) (c) Phase-contrast (d) Differential-interference- contrast (Nomarski) (e) Fluorescence Figure 6.3a-d Light microscopy 50 µm (f) Confocal 50 µm

Electron microscopes (EMs) are used to study subcellular structures Scanning electron microscopes (SEMs) focus e- onto the surface of a specimen, providing images that look 3-D Transmission electron microscopes (TEMs) focus e- through a specimen, used to study internal cellular structures Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

(b) Transmission electron microscopy (TEM) Longitudinal section of Fig. 6-4 TECHNIQUE RESULTS 1 µm (a) Scanning electron microscopy (SEM) Cilia (b) Transmission electron microscopy (TEM) Longitudinal section of cilium Cross section of cilium 1 µm Figure 6.4 Electron microscopy

What do you remember about Prokaryotic and Eukaryotic Cells????? Eukaryote Prokaryote Both

Prokaryotic = bacteria and Archaea Eukaryotic = everything else Concept 6.2: Eukaryotic cells have internal membranes that compartmentalize their functions Prokaryotic = bacteria and Archaea Eukaryotic = everything else Basic features of all cells: Plasma membrane Semifluid substance called cytosol (aka cytoplasm) Chromosomes (carry genes) Ribosomes (make proteins) Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Prokaryotic cells are characterized by having No nucleus DNA in an unbound region called the nucleoid No membrane-bound organelles Cytoplasm Circular chromosome called a plasmid Eukaryotic cells are characterized by having DNA in a nucleus that is bounded by a membranous nuclear envelope Membrane-bound organelles Cytoplasm Eukaryotic cells are generally much larger than prokaryotic cells Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Which class of cell is this? Fig. 6-6 Which class of cell is this? Fimbriae Nucleoid Ribosomes Plasma membrane Bacterial chromosome Cell wall Capsule 0.5 µm Flagella (a) A typical rod-shaped bacterium (b) A thin section through the bacterium Bacillus coagulans (TEM) Figure 6.6 A prokaryotic cell

Generally made up of a bilayer of phospholipids The plasma membrane is a selective barrier that allows sufficient passage of oxygen, nutrients, and waste to service the volume of every cell Generally made up of a bilayer of phospholipids Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Carbohydrate side chain Fig. 6-7 (a) TEM of a plasma membrane Outside of cell Inside of cell 0.1 µm Carbohydrate side chain Hydrophilic region Figure 6.7 The plasma membrane Hydrophobic region Hydrophilic region Phospholipid Proteins (b) Structure of the plasma membrane

The surface area to volume ratio of a cell is critical The logistics of carrying out cellular metabolism sets limits on the size of cells (what does this mean????) 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

BioFlix: Tour Of An Animal Cell Fig. 6-9a Nuclear envelope ENDOPLASMIC RETICULUM (ER) Nucleolus NUCLEUS Rough ER Smooth ER Flagellum Chromatin Centrosome Plasma membrane CYTOSKELETON: Microfilaments Intermediate filaments Microtubules Ribosomes Figure 6.9 Animal and plant cells—animal cell Microvilli Golgi apparatus Peroxisome Mitochondrion Lysosome BioFlix: Tour Of An Animal Cell

BioFlix: Tour Of A Plant Cell Fig. 6-9b Nuclear envelope Rough endoplasmic reticulum NUCLEUS Nucleolus Chromatin Smooth endoplasmic reticulum Ribosomes Central vacuole Golgi apparatus Microfilaments Intermediate filaments CYTO- SKELETON Microtubules Figure 6.9 Animal and plant cells—plant cell Mitochondrion Peroxisome Chloroplast Plasma membrane Cell wall Plasmodesmata Wall of adjacent cell BioFlix: Tour Of A Plant Cell

Is there any organelle you are unclear about from your pre-reading? You should know the major components of the cell and their fxns, do you? Is there any organelle you are unclear about from your pre-reading? Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Close-up of nuclear envelope Fig. 6-10 Nucleus 1 µm Nucleolus Chromatin Nuclear envelope: Inner membrane Outer membrane Nuclear pore Pore complex Rough ER Surface of nuclear envelope Ribosome 1 µm Figure 6.10 The nucleus and its envelope 0.25 µm Close-up of nuclear envelope Pore complexes (TEM) Nuclear lamina (TEM)

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 A net-like array of protein filaments that maintains the shape of the nucleus by mechanically supporting the nuclear envelope Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Components of the endomembrane system: 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

How are they related? We mentioned that all of these are part of the endomembrane system, so what does that mean? Can you determine any similarities that there may be between them? What would they be made of?

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, with ribosomes studding its surface For the Cell Biology Video ER and Mitochondria in Leaf Cells, go to Animation and Video Files. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Smooth ER Nuclear envelope Rough ER ER lumen Cisternae Transitional ER Fig. 6-12 Smooth ER Nuclear envelope Rough ER ER lumen Cisternae Transitional ER Ribosomes Transport vesicle 200 nm Smooth ER Rough ER Figure 6.12 Endoplasmic reticulum (ER)

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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Functions of Smooth ER and Golgi Apparatus The smooth ER Synthesizes lipids Metabolizes carbohydrates Detoxifies poison Stores calcium Functions of the Golgi apparatus: Modifies products of the ER Manufactures certain macromolecules Sorts and packages materials into transport vesicles Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

(“receiving” side of Golgi apparatus) 0.1 µm Fig. 6-13 cis face (“receiving” side of Golgi apparatus) 0.1 µm Cisternae Figure 6.13 The Golgi apparatus trans face (“shipping” side of Golgi apparatus) TEM of Golgi apparatus

Fig. 6-14a Nucleus 1 µm Phagocytosis – “ingestion” of food/solid materials into the cell thru vesicles Lysosome Digestive enzymes Lysosome Figure 6.14a Lysosome—phagocytosis Plasma membrane Digestion Food vacuole (a) Phagocytosis

Vacuoles: Diverse Maintenance Compartments A plant cell or fungal cell may have one or several vacuoles 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Endomembrane system Nucleus Rough ER Smooth ER cis Golgi Fig. 6-16-3 Nucleus Rough ER Smooth ER cis Golgi Figure 6.16 Review: relationships among organelles of the endomembrane system Endomembrane system Plasma membrane trans Golgi

Other Organelles Peroxisomes are oxidative organelles Mitochondria and chloroplasts Are not part of the endomembrane system Have a double membrane Have proteins made by free ribosomes Contain their own DNA Question: anyone know why mitochondria and chloroplasts contain their own DNA? Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Peroxisomes: Oxidation Peroxisomes are specialized metabolic compartments bounded by a single membrane Peroxisomes produce hydrogen peroxide and convert it to water Oxygen is used to break down different types of molecules Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Chloroplast Peroxisome Mitochondrion 1 µm Fig. 6-19 Figure 6.19 A peroxisome 1 µm

It is composed of three types of molecular structures: Concept 6.6: The cytoskeleton is a network of fibers that organizes structures and activities in the cell The cytoskeleton is a network of fibers extending throughout the cytoplasm It organizes the cell’s structures and activities, anchoring many organelles It is composed of three types of molecular structures: Microtubules Microfilaments Intermediate filaments Use motor proteins (dynein) to move For the Cell Biology Video The Cytoskeleton in a Neuron Growth Cone, go to Animation and Video Files For the Cell Biology Video Cytoskeletal Protein Dynamics, go to Animation and Video Files. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Video? Microtubule Microfilaments 0.25 µm Fig. 6-20 Figure 6.20 The cytoskeleton Microfilaments 0.25 µm

Components of the Cytoskeleton Three main types of fibers make up the cytoskeleton: Microtubules – thickest, shape cell, guide organelle mvmt, separate chroms during cell division Microfilaments, also called actin filaments, are the thinnest components (make up micro-villi in your intestines) Intermediate filaments are fibers with diameters in a middle range, more permanent, fix organelles in place and help with cell shape For the Cell Biology Video Actin Network in Crawling Cells, go to Animation and Video Files. For the Cell Biology Video Actin Visualization in Dendrites, go to Animation and Video Files. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Video: Paramecium Cilia Cilia and Flagella Microtubules control the beating of cilia and flagella, locomotor appendages of some cells Cilia and flagella differ in their beating patterns Video: Chlamydomonas Video: Paramecium Cilia Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Direction of organism’s movement Fig. 6-23 Direction of swimming (a) Motion of flagella 5 µm Direction of organism’s movement Figure 6.23a A comparison of the beating of flagella and cilia—motion of flagella Power stroke Recovery stroke (b) Motion of cilia 15 µm

Animation: Cilia and Flagella Cilia and flagella share a common ultrastructure: (what would this suggest?) A core of microtubules sheathed by the plasma membrane A basal body that anchors the cilium or flagellum Animation: Cilia and Flagella Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Notice the arrangement of the microtubules Fig. 6-24 Outer microtubule doublet Plasma membrane 0.1 µm Dynein proteins Central microtubule Radial spoke Protein cross-linking outer doublets Microtubules (b) Cross section of cilium Plasma membrane Basal body 0.5 µm (a) Longitudinal section of cilium 0.1 µm Notice the arrangement of the microtubules Figure 6.24 Ultrastructure of a eukaryotic flagellum or motile cilium Triplet (c) Cross section of basal body

Cell Wall Plant cell walls may have multiple layers: Primary cell wall: relatively thin and flexible Middle lamella: thin layer between primary walls of adjacent cells Secondary cell wall (in some cells): added between the plasma membrane and the primary cell wall Plasmodesmata are channels between adjacent plant cells For the Cell Biology Video E-cadherin Expression, go to Animation and Video Files. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Secondary cell wall Primary cell wall Middle lamella Central vacuole Fig. 6-28 Secondary cell wall Primary cell wall Middle lamella 1 µm Central vacuole Cytosol Plasma membrane Figure 6.28 Plant cell walls Plant cell walls Plasmodesmata

The Extracellular Matrix (ECM) of Animal Cells Animal cells lack cell walls but are covered by an elaborate extracellular matrix (ECM) The ECM is made up of glycoproteins such as collagen, proteoglycans, and fibronectin ECM proteins bind to receptor proteins in the plasma membrane called integrins For the Cell Biology Video Cartoon Model of a Collagen Triple Helix, go to Animation and Video Files. For the Cell Biology Video Staining of the Extracellular Matrix, go to Animation and Video Files. For the Cell Biology Video Fibronectin Fibrils, go to Animation and Video Files. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Figure 6.30 Extracellular matrix (ECM) of an animal cell, part 1 Collagen Proteoglycan complex Polysaccharide molecule EXTRACELLULAR FLUID Carbo- hydrates Fibronectin Core protein Integrins Proteoglycan molecule Plasma membrane Proteoglycan complex Figure 6.30 Extracellular matrix (ECM) of an animal cell, part 1 Micro- filaments CYTOPLASM

Functions of the ECM: Support Adhesion Movement Regulation Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Intercellular Junctions Neighboring cells in tissues, organs, or organ systems often adhere, interact, and communicate through direct physical contact Intercellular junctions facilitate this contact There are several types of intercellular junctions Plasmodesmata (cell with cell walls) – perforate cell walls Tight junctions -membranes of neighboring cells are pressed together, preventing leakage of extracellular fluid Desmosomes – anchoring junctions Gap junctions – communicating junctions Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Cell walls Interior of cell Interior of cell 0.5 µm Plasmodesmata Fig. 6-31 Cell walls Interior of cell Interior of cell Figure 6.31 Plasmodesmata between plant cells 0.5 µm Plasmodesmata Plasma membranes

Tight junctions prevent fluid from moving across a layer of cells Fig. 6-32a Tight junctions prevent fluid from moving across a layer of cells Tight junction Intermediate filaments Desmosome Gap junctions Figure 6.32 Intercellular junctions in animal tissues—tight junctions Extracellular matrix Space between cells Plasma membranes of adjacent cells

You should now be able to: Distinguish between the following pairs of terms: magnification and resolution; prokaryotic and eukaryotic cell; free and bound ribosomes; smooth and rough ER Describe the structure and function of the components of the endomembrane system Briefly explain the role of mitochondria, chloroplasts, and peroxisomes Describe the functions of the cytoskeleton Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Describe the structure of a plant cell wall Compare the structure and functions of microtubules, microfilaments, and intermediate filaments Explain how the ultrastructure of cilia and flagella relate to their functions Describe the structure of a plant cell wall Describe the structure and roles of the extracellular matrix in animal cells Describe four different intercellular junctions Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings