Prokaryotic vs Eukaryotic Cells
• Some organisms are unicellular (single celled);
the cell carries out all life functions. Unicellular
organisms are prokaryotic.
• Multicellular organisms have many cells that
work together to carry out life processes.
• Tissues are groups of cells that perform the
same function. Organs are several types of
tissue working together to perform specific
• An organ system is a group of organs
working together for a particular function.
For example, your digestive system
breaks down food and puts it in the blood.
Your circulatory system moves blood
throughout your body. Your respiratory
system puts O2 into your blood to be used
by cells for respiration, and removes H20
Organelles in unicellular organisms…
• Work like the organ
• Each organelle has a
specific function that
helps keep the one-
celled organism alive.
• Are found in ALL cells.
• Help cell to maintain homeostasis
(keeping a balance of solutes within a
• Are selectively permeable, meaning that
only certain substances can go through in
• Made of phospholipid bilayer.
• Does NOT require energy.
• Molecules move through the cell
membrane from areas of higher
concentration to areas of lower
• There are 3 types of passive transport –
diffusion, facilitated diffusion, and osmosis.
Diffusion & Facilitated Diffusion
• Diffusion is the process by which
substances move directly through the cell
• Facilitated diffusion involves the help of
a carrier protein to move a substance from
one side of the cell wall to the other.
• The movement of water from an area of
high water concentration to an area of low
water concentration through a semi-
• Hypotonic has a lower concentration of
solute (higher of water).
• Hypertonic has a higher concentration of
solute (lower of water).
• Isotonic means the solute concentration
is the same inside and outside the cell.
Osmosis ALWAYS occurs from
hypotonic to hypertonic…
• A process of moving material across the
cell membrane from an area of low
concentration to an area of high
• Requires energy to happen.
• Exocytosis removes materials from a cell.
• Endocytosis brings materials into a cell.
The membrane “absorbs” the material.
Factors Affecting Cellular Activity
• Volume – cells with large internal volume
cannot efficiently transport materials to the
organelles that need them.
• Surface Area – the greater the surface
area, the more efficient the cell.
• Environmental Factors – most cells
function best within a specific range of
temperature, light, and pH. (ex – plants)
Fluid Pressure in Cells
• Fluids are liquids and gases. Pressure is
a force (push or pull) applied uniformly
over an area.
• Blood Pressure – pressure exerted by
blood on the walls of blood vessels.
• Turgor Pressure – pressure that plant
cells put on each other when full of water;
allows plants to stand up and move water
up the stem or trunk to the top of the plant.
• Unicellular organisms have one cell; multicellular have
• Cells make tissues, which make organs, which make
• Organelles act as organs in a cell.
• Passive transport (diffusion/osmosis) does not require
energy. Active transport does.
• Volume, surface area, and environmental factors
(temperature, light, pH) affect cellular activity.
• The amount of fluid pressure in a cell affects its