Slide 1 Chapter 4 A Tour of the Cell Slide 2 State Standards Standard 1.c. Standard 1.e. Slide 3 Introduction to Cells Organisms are either - Single-celled, such as - Multicelled, such as The human body is made up of trillions of cells many of which are specialized - Muscle cells - Nerve cells - Blood cells
Slide 4 The Cell Theory Cells were first discovered in 1665 by Robert Hooke. The accumulation of scientific evidence led to the cell theory Slide 5 Microscopes provide windows to the world of the cell The Light Microscope Light passes through the specimen Lenses enlarge, or magnify, the image Magnification Resolving power Slide 6 Microscopes provide windows to the world of the cell The Electron Microscope Uses a beam of electrons Resolving power is higher than the light microscope Can magnify up to 100,000X
Slide 7 Microscopes provide windows to the world of the cell Scanning Electron Microscope (SEM) Used to study the details of the surface of the cell Used to study cell and organelle surfaces Slide 8 Microscopes provide windows to the world of the cell Transmission Electron Microscope (TEM) An electron beam is aimed through a thin section Used to explore the Slide 9 The Two Major Categories of Cells
Slide 10 The Two Major Categories of Cells There are 2 major categories of cells - Prokaryotic cells - Eukaryotic cells Both cells - Prokaryotic and eukaryotic cells differ in several ways Slide 11 The Size of Cells Most cells are 10-100 micrometers in size Cell size and shape are related to their function Ex: red blood cells, nerve cells, eggs Slide 12 The Size of Cells The lower limit of cell size is determined by the fact that a cell must be large enough to The maximum size of a cell is limited by the
Slide 13 Prokaryotic Cells Smaller than eukaryotic cells (2-8 um) Enclosed by a plasma membrane that is usually surrounded by a rigid cell wall The cell wall may be covered by a sticky capsule Ribosomes (70S) are present Slide 14 Structures of the Prokaryotic Cell Nucleoid region area where DNA is coiled in the cytoplasm. DNA is in direct contact with the rest of the cell Plasmid smaller circular DNA molecules Ribosomes where proteins are made Plasma membrane encloses the cytoplasm of the prokaryotic cell Cell wall rigid, composed of lipids, carbohydrates and protein. Protects the cell and maintains its shape Slide 15 Structures of the Prokaryotic Cell Capsule sticky outer coat that surrounds some prokaryotes. Protects the cell surface. Helps bacteria attach to surfaces Pili short surface projections found in some prokaryotes. Helps attach bacteria to surfaces Flagella long whiplike extensions found in some prokaryotes. Propel cell through liquid environments
Slide 16 The Role of Bacteria in the Nitrogen Cycle Slide 17 Eukaryotic Cells Larger than prokaryotic cells (10-100 um) More complex in structure Ribosomes (80S) Slide 18 Comparing Animal and Plant Cells Animal cells contain Plant cells contain a
Slide 19 Comparing Eukaryotic and Prokaryotic Cells Slide 20 Viruses are biological particles Slide 21 Structure of Viruses A typical virus is composed of 1. Genetic material 2. Capsid
Slide 22 Structure of Viruses Some viruses also have 1. Glycoprotein found on surface, specific for each type of virus 2. Membrane envelope surrounds protein coat, comes from membrane of host cell 3. Enzymes needed for transcription of virus genes Slide 23 Types of Viruses DNA Viruses Ex: Adenoviruses (cold) Slide 24 Types of Viruses RNA Viruses Contain single strand of RNA Ex:
Slide 25 Types of Viruses Retroviruses Type of The enzyme reverse transcriptase changes viral RNA to viral DNA that becomes part of the hosts DNA Ex: Slide 26 Slide 27 Virus Reproduction Cycles Lytic cycle 1. Virus attaches to receptor sites on host cell and genetic material enters host cell 2. Virus genetic material directs host cell to produce more virus genetic material and virus proteins 3. New virus particles are put together 4. New viruses are released
Slide 28 Virus Reproduction Cycles Lysogenic cycle 1. Virus genetic material enters cell 2. Virus DNA attaches to cell s DNA (prophage) 3. External stimuli (radiation, chemicals) cause prophage to become active or virulent 4. Virus enters lytic cycle Slide 29 Comparing Viruses, Prokaryotic Cells and Eukaryotic Cells