Transcript Cell Membrane

Phospholipid Bilayer
 Water soluble Phosphate
Heads (hydrophilic)
 Can interact with water
environment
 Water insoluble fatty acid tail
(hydrophobic)
 Repels (not attracted) to water
environments
Selectively Permeable
 The bilayer only allows certain things to
cross into the cell.
 This is because of the water-loving and
water-hating parts of the phospholipids
 OK: TINY molecules ( CO2, H2O, O2)
 Not OK: water soluble molecules (amino
acids, sugars, proteins, nucleic acids and
ions) and very large molecules.
Other things in the membrane
 Carbohydrate
markers (label the
cells)
 Proteins ****
 These help get
water soluble
molecules through
the membrane.
Passive (no energy) Movement
across the membrane
 Diffusion: Molecules move from a higher
concentration to a lower concentration.
 Equilibrium ****
 Concentration is equal throughout.
Passive (no energy) Movement
across the membrane
 Facilitated
Diffusion
 Protein channels
open to allow
water soluble
molecules to pass
through
membrane by
diffusion
Passive (no energy) Movement
across the membrane
 Osmosis: Water
moves from a
high
concentration of
water to a low
concentration of
water.
Tonicity and Osmosis - Isotonic
 Cells are always in an
aqueous environment.
 When the solute
concentration outside
is equal to the solute
concentration inside
it is called Isotonic
Tonicity and Osmosis – Hypertonic
 Hyper means : Above
 If the solute
concentration outside
the cell is higher than
the solute concentration
inside it is a hypertonic
solution.
 If the molecules outside
are not permeable,
osmosis will occur out
of the cell
Tonicity and Osmosis - Hypotonic
 Hypo means: Below
 When the solute
concentration outside
the cell is lower than
the solute
concentration inside,
this a Hypotonic
solution
 If the molecules
outside the cell are not
permeable, water
moves out of the cell
Questions
 Selectively Permeable means:
1. Only some things can get through
2. All things can get through
 Facilitated diffusion is used for:
1. Small molecules
2. Large polar molecules
 When a molecule such as Oxygen goes from a higher
concentration to a lower concentration, this is:
1. Diffusion
2. Osmosis
 When water moves into the cell during osmosis, this
means the outer solution was
1. Hypotonic
2. Hypertonic
Active Transport
 Moves particles from LOW concentration
to high concentration
 Requires Energy
 Uses proteins called carrier molecules.
Active Transport of LARGE molecules
Endocytosis
 Molecules that are too large to
enter by passive transport
mechanisms.
Exocytosis
 Secretes (pushes out) a
substance stored in a vesicle.
Types of Endocytosis
 Phagocytosis
 “cell eating”
 Solid materials are engulfed by the cell membrane.
 Pinocytosis
 “Cell drinking”
 Liquids are engulfed by the cell membrane.
Questions
 What type of transport uses energy?
1. Passive Transport
2. Active Transport
 Active transport moves things from
1. Higher concentration to lower concentration
2. Lower concentration to higher concentration
 Endocytosis brings LARGE molecules
1. Into the cell
2. Out of the cell
 Pinocytosis is
1. Cell Eating (bringing in solids)
2. Cell drinking (bringing in liquids)