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Biology – The Building
Blocks of Life

Objective:
Describe how the structure of the
plasma membrane allows it to
function as a regulatory structure
and/or protective barrier for a cell.
Cell (Plasma) Membrane

Parts of the Membrane:
– 1: Phospholipid Bilayer…2 layers of
phospholipids.
They have a “hydrophillic” head… that
attracts water
 And they have a “hydrophobic” tail…that
repels water

Cell (Plasma) Membrane

Parts of the Membrane
– 2: Proteins
Transport Proteins. A channel or a pump to
get molecules in or out of the cell.
 Surface proteins: can act as identification or
for signals.

Cell (Plasma) Membrane

Parts of the Membrane
– 3: Carbohydrates. Usually bonded to
protein…used for identification by your
immune cells.
Biology – The Building
Blocks of Life

Objective
Demonstrate the process of
diffusion, and tell how
osmosis is related to diffusion
Passive vs. Active
Transport

Passive Transport
– Does NOT use energy
– From an area of high concentration
to an area of low concentration
 Flowing “downhill” = no energy
needed
Passive vs. Active
Transport

Active Transport
–Uses energy
–Molecules move from an area of
low concentration to an area of
high concentration
Going “uphill” – must use
energy
Passive Transport

Diffusion
– Movement of molecules from an area
of high concentration to an area of low
concentration, until equilibrium is
reached.
– Equilibrium is “dynamic” = meaning the
molecules still move back and
forth…but the end totals remain the
same.
Passive Transport

Facilitated Diffusion
– Molecules move across the
membrane with the assistance of
helper protein molecules.
– Molecules can easily slip through
protein channels.
– Remember…No Energy is Used!!
Passive Transport

Osmosis
– Special kind of diffusion involving
water molecules moving across a
membrane
– Still…from high
concentration to low
concentration.
Active Transport

Endocytosis
– Cells actively bringing in substances
by the pinching off of the cell
membrane
– Cell membrane pinches off to form a
vacuole
Pinocytosis – Pino = “drink” = liquids
Phagocytosis – Phage = “eat” = solids
Endocytosis – “into”
Active Transport

Exocytosis
– Cell moving molecules out of the cell
membrane
– Uses energy
– Vacuole fuses with the membrane and
pushes the material out
Exocytosis – “out”
Exocytosis – “out”