Download Compartments/Containers

Chapter 4 Essays
• Comopartments/Containers
• Membranes
• Molecular Movement
Compartments/Containers
• Has an internal environment that is kept
separate from the external environment
• Barriers separate the internal and external
environment
– Create conditions within the organism that may vary
greatly from those on the outside.
– Skin (animals)
– Membranes (cells)
– Walls (plant and other cells)
– Shells (eggs)
• The presence of many compartments within one
cell or one organism allows for the presence of
many different internal environments
• Each compartment can contain different
substances that are required for specialized
cellular functions.
–
–
–
–
–
–
Mitochondria
Nucleus
Lysozome
Stomach
Liver
pancreas
Membranes pages 231• Forms a boundary that separates the inside of the cell
from the outside
• Impermeable to most substances or prevent most
substances from being able to pass into or out of the
compartment (cell)
• Some substances that cells need must pass into and out
of the cell
• Molecules of Life
– Large Proteins, Lipids, Carbohydrates, Nucleic Acids
– Small Molecules like water, carbon dioxide and oxygen and Ions
include; sodium, potassium, and chloride
• Selective Permeability– Only permeable to certain molecules
• depends on the structure of the membrane
– Lipid molecules
• are not locked rigidly in place
• do not mix well with water
– Lipid bilayer
• made up of two layers of lipids
• The parts of the lipid molecules with the lowest tendency to interact
with water orient toward the interior of the membrane
• The parts of the lipid molecules with the highest tendency interact
with water are oriented toward the inside and outside of the cell
• The interior of the membrane prevents water soluble molecules
from passing easily through it
• Fat soluble molecules move through it with ease
• Even though water molecules are not fat soluble they can make it
through the membrane because they are very small and their
charges are very slight.
• The membrane contains many proteins
– positioned among the lipid molecules
– Large molecules made of amino acids linked
together to form a long folded chain
– Some act as receptors –
• bind to specific chemicals like hormones which can
cause a response from inside the cell.
• This way the cell’s internal components can
respond to conditions outside the cell
– Can span all the way through the lipid bilayer
• Some proteins allow specific molecules to
move into or out of the cell or allow the
membrane to be selectively permeable.
– Channels through which large molecules like
sugars, glucose and other carbohydrates can
pass through the cell
– Channels through which ions (molecules with
an electrical charge) can pass through the
membrane
• Membranes are complex and perform an
important role in regulating internal
conditions.
Molecular Movements
• Concentration Gradient
– The difference in the concentration of certain molecules over a
distance.
– The more crowded the molecules the more concentrated they are
then they move DOWN
• Entropy or the tendency toward disorder. Molecules drift to a less
ordered state. Energy is required to keep order.
• Passive Transport- Does not require energy
– Diffusion is the movement of molecules from where they are
more concentrated to an area where they are less concentrated
“down there concentration gradient” until they are equally
distributed. Occurs in liquids as well as in the air.
• Osmosis the movement of water through a membrane from
an area of high concentration to an area of low concentration
– Can result in a build up of water “osmotic pressure” inside
the cell or outside the cell causing the cell to shrink or
burst.
• Facilitated Diffusion uses a protein channel in the cell
membrane to move large or charged molecules across the
membrane from an area of high concentration to an area of
low concentration.
• Active Transport
– Requires Energy
– Protein pump uses a protein channel to move molecules “up or
against” their concentration gradient (from an area of low
concentration to an area of high concentration)
– Endocytosis uses entire sections of cell membrane to surround
and take in many large substance. These substances can be
moved up or down their concentration gradients
– Exocytosis transports large substances encased in membrane
“vesicle” to the cell membrane. The vesicle membrane fused with
the cell membrane and releases it’s contents outside the cell.
These materials can be moved up or down their concentration
gradients.