Transcript Anatomy of a cell

Anatomy of a cell
Chapter 3
Typical Cell
Cells vary due to function. The typical cell
exhibits the most important characteristics
of many distinctive cell types.
 Examples of cell types:
Nerve cells, muscle cells, red blood cells,
gland cells, and immune cells
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Functional Anatomy of Cells
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Cell structures
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Plasma membrane—separates the cell from
its surrounding environment
Cytoplasm—thick gel-like substance inside of
the cell composed of numerous organelles
suspended in watery cytosol; each type of
organelle is suited to perform particular
functions
Nucleus—large membranous structure near
the center of the cell
Cell Membranes
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Each cell contains a variety of
membranes:
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Plasma membrane
Membranous organelles—sacs and canals
made of the same material as the plasma
membrane
Cell Membranes
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Fluid mosaic model—theory explaining
how cell membranes are constructed
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Molecules of the cell membrane are arranged
in a sheet
The mosaic of molecules is fluid; that is, the
molecules are able to float around slowly
This model illustrates that the molecules of
the cell membrane form a continuous sheet
Cell Membranes

Primary structure of a cell membrane is a
double layer of phospholipid molecules
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Heads are hydrophilic (water-loving)
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Tails are hydrophobic (water-fearing)
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Molecules arrange themselves in bilayers in water
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Cholesterol molecules are scattered among the phospholipids
to allow the membrane to function properly at body
temperature
Most of the bilayer is hydrophobic; therefore water or watersoluble molecules do not pass through easily
Plasma Membranes and Proteins
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A cell controls what moves through any
section of membrane by means of proteins
embedded in the phospholipid bilayer.
The protein acts as a gate allowing watersoluble molecules to pass through the
membrane.
Cytoplasm and Organelles

Cytoplasm—gel-like internal substance of
cells that includes many organelles
suspended in watery intracellular fluid
called cytosol
Cytoplasm and Organelles
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Two major groups of organelles:
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Membranous organelles are specialized sacs
or canals made of cell membranes
Nonmembranous organelles are made of
microscopic filaments or other
nonmembranous materials
Organelles
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Endoplasmic reticulum (Highway system
of the cell)
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Made of canals with membranous walls and
flat, curving sacs arranged in parallel rows
throughout the cytoplasm; extend from the
plasma membrane to the nucleus
Proteins move through the canals
ER
Two types of ER:
1) Rough ER: Ribosomes on the outer
surface of the organelle
2) Smooth ER: Synthesizes certain lipids and
carbohydrates and creates membranes for
use throughout cell
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nonmembranous structure
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Ribosomes in the endoplasmic reticulum make
proteins for “export” or to be embedded in the
plasma membrane; free ribosomes make
proteins for the cell’s domestic use
Golgi apparatus
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Golgi apparatus (UPS of cell): flat-like
pancake organelle that packages and
delivers proteins and other organic
molecules throughout the cell.
Lysosomes
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Lysosomes (miniature stomach)- enzymes
in lysosomes digest the protein structures
of defective cell parts, including plasma
membrane proteins, and particles that
have become trapped in the cell
Mitochondria
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Mitochondria (power plant of cell)mitochondrial enzymes catalyze series of
oxidation reactions that provide about
95% of cell’s energy supply
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Each mitochondrion has a DNA molecule,
allowing it to produce its own enzymes and
replicate copies of itself
Nucleus
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Consists of nuclear envelope (composed of
two membranes each with essentially the
same molecular structure as plasma
membrane) surrounding nucleoplasm;
nuclear envelope has holes called nuclear
pores
Cytoskeleton
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The cell’s internal supporting framework
made up of rigid, rodlike pieces that
provide support and allow movement and
mechanisms that can move the cell or its
parts (Figure 3-13)
Centrosome
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An area of the cytoplasm near the nucleus
that coordinates the building and breaking of
microtubules in the cell- Important in cell
division