chapter 4 – a tour of the cell. intro copyright © 2007 pearson education inc., publishing as...
TRANSCRIPT
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 DomainsScientist’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: http://ed.ted.com/lessons/the-wacky-history-of-cell-theory
Microscopes provide windows to the world of the cell
The Light MicroscopeLight passes through the specimenLenses enlarge, or magnify, the imageMagnification – the increase in the specimen’s apparent sizeResolving power – the ability to show 2 objects as being separate
Microscopes provide windows to the world of the cell
The Electron MicroscopeUses a beam of electronsResolving power is higher than the light microscopeCan magnify up to 100,000X
The Size of CellsMost cells are 10-
100 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 µm30 µm
The Two Major Categories of Cells
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-Prokaryotes Eukaryotes
Differences 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 CellsLarger than
prokaryotic cells (10-100 um)
More complex in structure
DNA housed in the nucleus
Ribosomes (80S)
Membrane bound organelles
Comparing Animal and Plant CellsAnimal cells
contain centrioles, lysosomes, flagella
Plant cells contain a central vacuole, cell wall, chloroplasts
Comparing Eukaryotic and Prokaryotic Cells-Prokaryotes Eukaryotes
Differences Differences
Commonalities
Comparing Eukaryotic and Prokaryotic Cells- Differences in parallel statements Prokaryotic CellsDate back at least 3.5 BYAEx include: Bacteria & ArchaeabacteriaSimpler Structure (all single celled organisms)
Naked DNA (not wrapped around histone proteins)
Circular Chromosomes
DNA in cytoplasm (nucleoid region)
70S ribosomesNo internal membrane
compartments (no membrane bound organelles)-ex: no mitochondria, no Rough ER
Eukaryotic CellsDescended from ancient prokaryotes 2.1 BYAEx organisms: plants, animals, fungi, protistsMore Complex Structure (mostly multicellular organisms but some single celled organism)
DNA associated with histone proteins Chromosomes linear
DNA separated from cytoplasm (in nucleus)
80S ribosomesInternal membrane
compartments (membrane bound organelles) –ex: yup mitochondria and Rough ER
Comparing Eukaryotic and Prokaryotic Cells-
Commonalities: Prokaryotes & EukaryotesSmallest units of Life (therefore has the characteristics of life Chapter 1!)
Requires energy (to run metabolic reactions of life)Grows and developsIndependently reproduce
DNA stores genetic informationCan evolve over generations
Order: internal organizationResponds to environmental stimuli
Ribosomes build proteins for the cellsContains plasma membrane to regulate what enters and leaves the cellFilled with cytosol (fluid)