Unformatted text preview: CHAPTER TWO
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TEM provides greater magnification and resolution than LM, allowing details of
structures inside cells and attachments to the cell surface to be studied.
The basic functions of cells are covering, lining, storage, movement, connection,
defense, communication, and reproduction.
The three main regions of a cell are (1) the plasma membrane, a vital boundary
around the cell; (2) cytoplasm, composed of all cellular contents between the
plasma membrane and the nucleus; and (3) the nucleus, the cell's control center.
Phospholipids, cholesterol, and glycolipids are found in the plasma membrane.
Ions, nutrients, wastes, and secretory products may cross a selectively permeable
Diffusion is the tendency of molecules to move down their concentration
gradients (from regions of higher concentration to regions of lower
Osmosis is a special type of passive transport by which water diffuses from one
side of the selectively permeable membrane to the other side of the membrane.
Both facilitated diffusion and receptor-mediated endocytosis require a transport
protein within the plasma membrane.
Cytosol is the viscous, syruplike fluid of the cytoplasm that contains many solutes
(ions, nutrients, proteins, carbohydrates, lipids, and other small molecules).
Lysosomes are membrane-bound sacs that contain catalysts (digestive enzymes)
used by the cell to digest waste products and other macromolecules.
Mitochondria are double-membrane-bound organelles that produce large amounts
of ATP. Centrioles are responsible for organizing microtubules that attach to
chromosomes during cell division (mitosis).
Proteins synthesized by free ribosomes remain within the cell and function for
cellular activities. Proteins synthesized on fixed ribosomes (1) are exported
outside of the cell, (2) are incorporated into the plasma membrane, or (3) form
enzymes within a new lysosome.
Cilia are cytoplasmic projections whose beating-like movement moves materials
along the exposed cell surface.
The nuclear envelope is the boundary around the nucleus that controls the entry
and exit of materials between the nucleus and the cytoplasm.
Chromatin is a strand of unwound DNA and its associated proteins.
Chromosomes are the highest level of organization of genetic material. Within
them, the molecule of DNA and associated proteins are tightly wound.
The parts of interphase are: the Gi phase, characterized by cell growth, protein
production, and metabolic activities; the S phase, during which DNA is replicated
prior to cell division and growth activities continue; and the G2 phase,
characterized by completion of centriole replication, organelle production, and
synthesis of proteins needed for cellular division....
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- Fall '15