Chapter 4 – A Tour of the Cell

Intro

Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings The Microscopic World of Cells Organisms are either: –Single-celled, such as most bacteria and protists –Multicelled, such as plants, animals, and most fungi

Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings Life’s 3 Domains Scientist’s study of different organisms’ cell structure and DNA lead them to group organisms into 3 different domains

Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings Life’s 3 Domains First cells (prokaryotic) 3.5 billion years ago Archaebacteria: Oldest bacteria Eubacteria: common bacteria First Eukaryotes -- Protists Plants Animals Fungi

Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings My Thoughts (Complete one of the following statements on the left side opposite the notes you just took) I can picture… A question I have is… This is like… This reminds me of… I am confused about… The big idea here is… I think/wonder …. I predict that …

Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings The Microscopic World of Cells The human body is made up of trillions of cells many of which are specialized –Muscle cells, Nerve cells, & blood cells…

The Cell Theory Cells were first discovered in 1665 by Robert Hooke. The accumulation of scientific evidence led to the cell theory - All living things are composed of one or more cells - All cells are formed from previously existing cells Cell theory 6 minute video: history-of-cell-theoryhttp://ed.ted.com/lessons/the-wacky- history-of-cell-theory

Microscopes provide windows to the world of the cell The Light Microscope Light passes through the specimen Lenses enlarge, or magnify, the image Magnification – the increase in the specimen’s apparent size Resolving power – the ability to show 2 objects as being separate

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

The Size of Cells Most cells are micrometers (µm) in size Cell size and shape are related to their function Ex: red blood cells, nerve cells, eggs

The Size of Cells The lower limit of cell size is determined by the fact that a cell must be large enough to house the parts (DNA, organelles) it needs to survive and reproduce. The maximum size of a cell is limited by the amount of surface needed to obtain nutrients from the environment and dispose of wastes. 10 µm 30 µm

The Two Major Categories of Cells

There are 2 major categories of cells - Prokaryotic cells - Eukaryotic cells Both cells - Are surrounded by a plasma membrane - Consist of cytoplasm and organelles and contain DNA Prokaryotic and eukaryotic cells differ in several ways

Comparing Eukaryotic and Prokaryotic Cells- ProkaryotesEukaryotes Differences Commonalities

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 DNA is found inside the cell but it is not housed in a nucleus Ribosomes (70S) are present Internal structures surrounded by membranes are not present

Eukaryotic Cells Larger than prokaryotic cells ( um) More complex in structure DNA housed in the nucleus Ribosomes (80S) Membrane bound organelles

Comparing Animal and Plant Cells Animal cells contain centrioles, lysosomes, flagella Plant cells contain a central vacuole, cell wall, chloroplasts

Comparing Eukaryotic and Prokaryotic Cells- ProkaryotesEukaryotes Differences Commonalities

Comparing Eukaryotic and Prokaryotic Cells- Differences in parallel statements Prokaryotic Cells Date back at least 3.5 BYA Ex include: Bacteria & Archaeabacteria Simpler Structure (all single celled organisms) Naked DNA (not wrapped around histone proteins) Circular Chromosomes DNA in cytoplasm (nucleoid region) 70S ribosomes No internal membrane compartments (no membrane bound organelles)-ex: no mitochondria, no Rough ER Eukaryotic Cells Descended from ancient prokaryotes 2.1 BYA Ex organisms: plants, animals, fungi, protists More Complex Structure (mostly multicellular organisms but some single celled organism) DNA associated with histone proteins Chromosomes linear DNA separated from cytoplasm (in nucleus) 80S ribosomes Internal membrane compartments (membrane bound organelles) – ex: yup mitochondria and Rough ER

Comparing Eukaryotic and Prokaryotic Cells- Commonalities: Prokaryotes & Eukaryotes Smallest units of Life (therefore has the characteristics of life Chapter 1!) Requires energy (to run metabolic reactions of life) Grows and develops Independently reproduce DNA stores genetic information Can evolve over generations Order: internal organization Responds to environmental stimuli Ribosomes build proteins for the cells Contains plasma membrane to regulate what enters and leaves the cell Filled with cytosol (fluid)