Bio1100
Chapter 4
A tour of the cell
Living
organisms
are made of
cells
, with or without a
nucleus
.
The
plasma
membrane that encloses all cells consists of a
phospholipid
bilayer
.
The
nucleus
contains the hereditary material
DNA
and serves as the genetic control
center
.
The
endomembrane
system
forms a connected network of membranous organelles within the cell.
The
mitochondrion
is the site of cellular
respiration
, providing energy for the cell.
Plant cells have several structures not present in animal cells.
The
chloroplast
is the site of
photosynthesis
.
A
central
vacuole
provides storage.
Cell
walls
support and protect the cell.
The interior of the cell is supported by a
network
of protein fibers called the
cytoskeleton
.
Materials pass into and out of the cell passively
through
diffusion
and
osmosis
.
Active
transport
requires energy to move substances
up
(against) concentration gradients.
Large substances move into and out of the cell through
endocytosis
and
exocytosis
without crossing the
plasma
membrane.