cells. what is a cell? simplest unit of life structural and functional component of living things...
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CELLS
What is a cell?
• simplest unit of life
• structural and functional component of living things
• all organisms are made of cells
• single celled: unicellular
• many cells: multicellular>>specialization
• all cells are related by their descent from other cells
Studying Cells
• cells are tiny• light microscope—passes visible light through specimen
– LM up to 1000X– resolving limit 200 nm (bacterium)– live cell observation
• electron microscope—focuses beam of e- through or on– SEM– TEM– prep kills cell
c
green alga
Cell Fractionation
• study of cell structure and function
• isolate components of cells based on size and density
• biochemistry & cytology– presence of cellular respiration enzymes– large numbers of mitochondria
cell fractionation campbell fig6.5 pg 97
Major Cell Types• prokaryotic
– bacteria– plasma membrane, cytosol, chromosomes, ribosomes– DNA in cytoplasm, region called nucleoid (no nuclear
membrane)
• eukaryotic– protists, fungi, plants, animals– plasma membrane, cytosol, chromosomes, ribosomes– DNA in nucleus (surrounded by nuclear membrane)– membrane bound organelles
Size of Cells
• prokaryotic: typically 1-5 μm
• eukaryotic: typically 10-100 μm
• surface to volume ratio: generally keeps cells small– as cell grows, volume grows more than s.a.– larger organisms--more not larger cells
• selective barrier of plasma membrane– limited amount of substance crosses/sec.
campbell fig 6.8 pg 99 surface to vol ratio
A Closer Look at Cells
• The cell is the lowest level of organization that can perform all activities of life
• The ability of cells to divide is the basis of all reproduction, growth, and repair of multicellular organisms
LE 1-5
25 µm
The Cell’s Heritable Information
• Cells contain DNA, the heritable information that directs the cell’s activities
• DNA is the substance of genes
• Genes are the units of inheritance that transmit information from parents to offspring
LE 1-6
Sperm cell
NucleicontainingDNA
Egg cell
Fertilized eggwith DNA fromboth parents
Embryo’s cells With copies of inherited DNA
Offspring with traits inherited from both parents
• Each DNA molecule is made up of two long chains arranged in a double helix
• Each link of a chain is one of four kinds of chemical building blocks called nucleotides
LE 1-7
DNA double helix Single strand of DNA
Nucleotide
Cell
Nucleus DNA
A Hierarchy of Biological Organization
1. Biosphere: all environments on Earth
2. Ecosystem: all living and nonliving things in a particular area
3. Community: all organisms in an ecosystem
4. Population: all individuals of a species in a particular area
5. Organism: an individual living thing
A Hierarchy of Biological Organization (continued)
6. Organ and organ systems: specialized body parts made up of tissues
7. Tissue: a group of similar cells8. Cell: life’s fundamental unit of structure
and function9. Organelle: a structural component of a
cell10. Molecule: a chemical structure
consisting of atoms
Ecosystems
The biosphere
Organisms
Populations
Communities
Cells
Organelles
Molecules
Tissues
Organs and organ systems
Cell1 µm
Atoms
10 µm
50 µm
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