Two types of proteins in membranes:
• Integral proteins that are embedded or
inserted into the cell membrane.
• Peripheral proteins that are attached to the
surface of the cell membrane.
• The functions of these proteins include
transportation, enzymes, receptor sites, cell
adhesion and attachment to the cytoskeleton.
Through the cell membrane
• Diffusion (passive)
• Osmosis (passive)
• Facilitated diffusion (passive)
• Active transport (requires energy)
• Bulk transport (requires energy)
• Passive movement of molecules from an area
of high concentration to low concentration.
• Concentration gradient is the difference in
concentration between the two regions.
• Small, uncharged molecules (CO2, H20 and O2)
move easily through the membrane.
• Works well over short distances, but slows
once molecules enter the cell.
• Limits cell size.
• Osmosis is the process by which water moves
through a semi-permeable membrane from an
area of high concentration (of water) to lower
• It is a passive process and therefor does not
• Channel mediated - Some substances diffuse
with the assistance of protein channels
• Carrier mediated - Substances move down
the concentration gradient via specific carrier
molecules. Slower than channel-mediated as
the protein carrier has to change shape for
each molecule it transports.
• Movement of dissolved substances into or out
of cells against a concentration gradient.
• Active transport requires energy and involves
a carrier protein for each substance that is
• Includes endocytosis (into cell) and exocytosis
(out of cell).
• Transport vesicles fuse with the membrane to
consume or excrete substances.
• Pinocytosis is when a liquid is consumed or
• Phagocytosis is when a solid substance is
consumed or excreted.
• Cell walls lie outside the plasma membrane in
plant, fungal and prokaryotic cells.
• Endocytosis and exocytosis can occur into and
out of the cell vacuole.
• Ribosomes are cell
of RNA and proteins,
found in the
• Ribosomes are responsible for assembling the
proteins in a cell.
Nucleus with Rough Endoplasmic
• Lysosomes serve as the cells digestive system.
• They are membrane-bound organelles
containing enzymes that can break down
individual proteins or complete micro-organisms.
• They are released from the golgi apparatus.