Download The cell and its environment

The Cell and its Environment
The cell membrane is like a
Gatekeeper
• The cell membrane is
selectively permeable, which
means that some substances
can pass through it while
others cannot
Transport in Cells
• Substances that can move into and
out of a cell do so by one of two
methods
1) Passive Transport
2) Active Transport
What is Passive Transport??
• Driven by “diffusion” natural
spread of particles from and
area of high concentration to
low concentration
• Always travels “down a
concentration gradient”
• Not using energy (cell doesn’t
have to do anything to make it
happen)
BrainPOP | Passive Transport
What is diffusion ?
• Diffusion is a special case of
passive transport by which
molecules tend to move from
an area of higher
concentration to a area of
lower concentration
BrainPOP | Diffusion
What is Osmosis?
• The diffusion of water
molecules through a
selectively permeable
membrane from high
to low concentration is
osmosis.
Osmosis
• Because cells cannot
function properly without
adequate water, many
cellular processes depend
on osmosis.
What is Active Transport?
• Active transport is the
movement of materials
through a cell membrane using
energy from low concentration
to high concentration.
BrainPOP | Active Transport
Active Transport
• Use transport proteins
• Transport proteins in the cell
membrane “pickup” molecules
outside the cell and carry
them in using energy.
Transport by Engulfing
Active Transport
Process by Engulfing
1) First, the cell membrane surrounds and
engulfs, or encloses, a particle.
2) Once the particle is engulfed, the cell
membrane wraps around the particle and
forms a vacuole within the cell.
**The cell must use energy in this** process.
Engulfing
• The main difference between
passive and active transport is that
active transport requires the cell to
use energy while passive transport
does not.
• Osmosis and Diffusion are both
Passive transport