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Chapter 4

BIOA01H3 Chapter Notes - Chapter 4: Periplasm, Gram Staining, Glycerol


Department
Biological Sciences
Course Code
BIOA01H3
Professor
Mark Fitzpatrick
Chapter
4

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Chapter 4: Cells t The Working Units of Life
4.1 What features of cells make them the fundamental unit of life?
x Cell theory has three important implications:
o Studying cells is similar to studying life
o Life is continuous
o Origin of life marked by the origin of first cells
x Cells are generally small (exceptions: eggs of birds and neurons)
x It is a practical necessity arising from the change in the surface area to volume ratio
o The volume of a cell determines the amount of chemical activity it carries out
o The surface area of a cell determines the amount of transfer across the membrane
x As the cell increases in size, its chemical activity grows faster than the rate it can transfer
molecules in and out t which results in waste build up.
x Also the cell must transfer materials from one end of the cell to another, smaller cells achieve
this better
x Things are grouped together via various factors: structure, organization, methods of acquiring
energy, reproduction and gene sequence of cells
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x Bacteria:
o Single-celled
o Lack double membrane bound organelles
o Have either no cell walls (Gram negative) or a cell wall containing peptidoglycan (Gram-
positive)
x Archaea
o Single-celled organisms
o Lack double membrane bound organelles
o Have cell walls but none with peptidoglycan
x Eukarya
o Can be single-celled or multiceullar
o Double membrane bound organelles
o ooÁoo}v[ZÀ]}PoÇv
x The Plasma Membrane - all cells are surrounded by a membrane
x Composed of a phospholipid bilayer with the hydrophobic tails projecting inward, and the
hydrophilic heads projecting outwards
x Proteins and other molecules are embedded in the lipids
x Selectively permeable barrier
x Embedded proteins facilitate communication, adhesion, and selective passage across membrane
x Helps cell maintain homeostasis
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