Chapter 4 Lecture Outline See PowerPoint Image Slides for all figures and tables pre-inserted into PowerPoint without notes.

The Cell Theory All living things are made of cells. A cell The basic unit of all living things. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

The Historical Context of the Cell Theory Robert Hooke coined the term “cell.” Look at cork cells under a simple microscope. Anton van Leeuwenhoek Made better microscopes Used them to look at a variety of substances and identified animalcules Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

The Historical Context of the Cell Theory Mathias Jakob Schleiden Concluded that all plants were made of cells Theodor Schwann Concluded that all animals were made of cells Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Initial Observations of Cells Cell wall Outer non-living part of plant cells Protoplasm Interior living portion of the cell Nucleus Contains the genetic information of the cell Cytoplasm Fluid part of the protoplasm Organelles “Little organs” within the protoplasm Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Different Kinds of Cells Prokaryotic Structurally simple cells Lack a nucleus Lack most other organelles Bacteria Eukaryotic cells More complex Have a nucleus Have a variety of organelles Plants, animals, fungi, protozoa and algae Typically much larger than prokaryotic cells Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Major Cell Types Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Cell Size Prokaryotic cells Eukaryotic cells 1-2 micrometers in diameter Eukaryotic cells 10-200 micrometers in diameter Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Surface Area-to-Volume Ratio Cell size is limited. Cells must get all of their nutrients from their environment through their cell membranes. Volume increases more quickly than surface area. Surface area-to-volume ratio must remain small. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

The Structure of Cell Membranes Thin sheets composed of phospholipids and proteins Fluid-mosaic model Two layers of phospholipids Fluid Has an oily consistency Things can move laterally within the bilayer. Mosaic Proteins embedded within the phospholipid bilayer Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

The Phospholipid Bilayer Phospholipid structure Hydrophobic tails Hydrophilic heads Bilayer Hydrophobic tails of each layer associate with each other. Hydrophilic heads on the surface of the bilayer Cholesterol Hydrophobic Found within the hydrophobic tails Keeps the membrane flexible Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Membrane Proteins Some are on the surface Some are partially embedded. Protrude from one side Some are completely embedded. Protrude from both sides Functions Transport molecules across the membrane Attachment points for other cells Identity tags for cells Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Organelles Composed of Membranes Plasma membrane (cell membrane) Different cellular membranous structures serve different functions Endoplasmic reticulum Golgi apparatus Lysosomes Peroxisomes Vacuoles and vesicles Nuclear membrane Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

The Plasma Membrane Composed of a phospholipid bilayer Separates the contents of the cell from the external environment Important features Metabolic activities Moving molecules across the membrane Structurally different inside and outside Identification: Self vs. nonself Attachment sites Signal transduction Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

The Endoplasmic Reticulum Consists of folded membranes and tubes throughout the cell Provides a large surface area for important chemical reactions Because it is folded, it fits into a small space. Two types of ER Rough Has ribosomes on its surface Sites of protein synthesis Smooth Lacks ribosomes Metabolizes fats Detoxifies damaging chemicals Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

The Golgi Apparatus Stacks of flattened membrane sacs Functions Modifies molecules that were made in other places Manufactures some polysaccharides and lipids Packages and ships molecules Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Traffic Through the Golgi Vesicles bring molecules from the ER that contain proteins. Vesicles fuse with the Golgi apparatus. The Golgi finishes the molecules and ships them out in other vesicles. Some are transported to other membrane structures. Some are transported to the plasma membrane. Some vesicles become lysosomes. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Lysosomes Vesicles containing enzymes that digest macromolecules Carbohydrates Proteins Lipids Nucleic acids Interior contains low pH These enzymes only work at pH=5. The cytoplasm is pH=7. If the lysosome breaks open, these enzymes will inactivate and will not damage the cell. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Functions of Lysosomes Digestion Of food taken into the cell Destruction Disease-causing organisms Old organelles Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Peroxisomes Not formed from golgi membrane, but from ER membrane Contain the enzyme catalase Breaks down hydrogen peroxide Breaks down long-chain fatty acids Synthesizes cholesterol and bile salts Synthesizes some lipids Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Vacuoles and Vesicles Membrane-enclosed sacs Vacuoles Vesicles Larger sacs Contractile vacuoles found in many protozoa Forcefully expel excess water from the cytoplasm Vesicles Smaller vesicles Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Vacuoles and Vesicles Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

The Nuclear Membrane Separates the genetic material from the rest of the cell Filled with nucleoplasm Composed of two bilayers Contains holes called nuclear pore complexes Allow large molecules like RNA to pass through the membrane into the cytoplasm Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

The Endomembrane System ̶ Interconversion of Membranes Membranes are converted from one membranous organelle to another. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Energy Converting Organelles Mitochondrion A small bag with a large bag stuffed inside Larger internal bag is folded into cristae Cristae contain proteins for cellular respiration. Releases the energy from food Requires oxygen Uses the energy to make ATP Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Energy Converting Organelles Chloroplasts Sac-like organelle Contain chlorophyll Perform photosynthesis Uses the energy in light to make sugar Contain folded membranes called thylakoids Thylakoids stacked into grana Thylakoids contain chlorophyll and other photosynthetic proteins. Thylakoids surrounded by stroma Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Nonmembranous Organelles Ribosomes Cytoskeleton Centrioles Cilia flagella Inclusions Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Ribosomes Made of RNA and proteins Composed of two subunits Large Small Are the sites of protein production Found in two places Free floating in the cytoplasm Attached to endoplasmic reticulum Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Cytoskeleton Provides shape, support and movement Made up of Microtubules Microfilaments (actin filaments) Intermediate filaments Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Centrioles Two sets of microtubules arranged at right angles to each other Located in a region called the centrosome Microtubule-organizing center near nucleus Organize microtubules into spindles used in cell division Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Cilia and Flagella Hair-like projections extending from the cell Composed of microtubules covered by plasma membrane Flagella Long and few in number Move with an undulating whip-like motion Cilia Small and numerous Move back and forth like oars on a boat 9 + 2 arrangement of microtubules Cell can control their activity Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Cilia and Flagella Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Inclusions Collections of miscellaneous materials Can be called granules Temporary sites for the storage of nutrients and waste Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Nuclear Components Contains chromatin DNA + proteins Becomes condensed during cell division into chromosomes Surrounded by double layer of membrane Nuclear membrane contains pores to control transport of materials in and out of nucleus Contains one or more nucleoli Site of ribosome synthesis Contains nucleoplasm Water, nucleic acids, etc. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Getting Through Membranes Diffusion Facilitated diffusion Osmosis Active transport Endocytosis Exocytosis Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Diffusion Molecules are in constant, random motion. Molecules move from where they are most concentrated to where they are less concentrated. This is called diffusion. Involves a concentration gradient (diffusion gradient) No concentration gradient=dynamic equilibrium Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

The Rate of Diffusion Depends on The size of the molecule Smaller molecules diffuse faster. The size of the concentration gradient The greater the concentration difference, the faster the diffusion. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Diffusion in Cells Diffusion can only happen if there is no barrier to the movement of molecules. Can only happen across a membrane if the membrane is permeable to the molecule Membranes are semi-permeable; they only allow certain molecules through. Membrane permeability depends on the molecules size, charge, and solubility. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

The Direction of Diffusion Determined solely by the concentration gradient Diffusion that does not require energy input is passive. Example: Oxygen diffusion Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Osmosis The diffusion of water through a selectively-permeable membrane Occurs when there is a difference in water concentration on opposite sides of the membrane. Water will move to the side where there is less water Or more solute Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Osmotic Influences on Cells If a cell has less water (more solute) than its environment It is hypertonic to its surroundings. If a cell has more water (less solute) than its environment It is hypotonic to its surroundings. If a cell has equal amounts of water (and solute) as its environment It is isotonic to its surroundings. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Osmotic Influences on Cells Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Osmosis in Animal and Plant Cells Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Facilitated Diffusion Some molecules have to be carried across the membrane. Accomplished by carrier proteins Still involves diffusion Follows a concentration gradient Is passive transport Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Active Transport Opposite of diffusion Moves molecules across a membrane UP their concentration gradient Uses transport proteins in the membrane Specific proteins pump specific molecules Requires the input of energy Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Endocytosis Moves large molecules or sets of molecules into the cell Phagocytosis Cell eating Food engulfed by the membrane Material enters the cell in a vacuole. Pinocytosis Cell drinking Just brings fluid into the cell Receptor-mediated endocytosis Molecules entering the cell bind to receptor proteins first. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Exocytosis Moves large molecules or sets of molecules out of the cell Vesicles containing the molecules to be secreted fuse with the plasma membrane. Contents are dumped outside the cell. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Endocytosis and Exocytosis Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Prokaryotic Cells Two different types of prokaryotes Domain eubacteria Contains bacteria Domain archaea Contains prokaryotes that live in extreme environments Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Prokaryotic Cell Structure Contain DNA and enzymes Able to reproduce Engage in metabolism Surrounded by a plasma membrane Plasma membrane surrounded by a cell wall Maintains the shape of the cell Cell wall surrounded by a capsule Helps them adhere to hosts Protects them from destruction Contain ribosomes May contain flagella Facilitates movement Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Different Types of Eukaryotic Cells Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Summary of Cell Organelles and Their Functions Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.