Download Homeostasis and Cellular Transport Cell Membrane A phospholipid

Homeostasis and Cellular
Transport
Cell Membrane
• A phospholipid bilayer that forms
the outer membrane of a cell
• Is selectively permeable
• Controls which substances pass into
or out of the cell
Lipids
• A type of organic molecule that is
insoluble in water
• Ex. Fats, oils, waxes
Phospholipid
• A type of lipid found in the cell
membrane. Has a phosphate group
attached to it.
• Phospholipids have polar,
hydrophilic heads and nonpolar,
hydrophobic tails.
Hydrophilic
• Molecular attraction to water
• (water loving)
Hydrophobic
• Molecular repulsion to water
• (water fearing)
• The cell membrane is formed by a
double layer of phospholipids
arranged with their tails facing each
other and their polar heads oriented
toward the watery environment
inside and outside the cell
Membrane Proteins
• Peripheral proteins- proteins located
either on the inner surface or outer
surface of the cell membrane
Membrane Proteins
• Integral proteins- proteins that are
embedded within the cell membrane;
extend from the outer surface to the
inner surface; play an important role
in transporting substances across the
cell membrane
Fluid Mosaic Model
• States that the phospholipids and
membrane proteins move with in the
cell membrane. The movement of
the phospholipids and proteins
creates tiny pores where certain
substances can diffuse into the cell.
Solution
• a mixture in which one or more
substances are uniformly distributed
Solute
• The substance that is dissolved in a
solution
Solvent
• The substance in which a solute is
dissolved
Sample Problems
• Identify the solvent and solute in
each of these solutions
• 1. sugar water solution
• 2. salt water solution
Aqueous solution
• Solution in which the water is the
solvent
Concentration
• Measurement of the amount of
solute dissolved in a fixed amount of
the solution
Isotonic solution
• The concentration of dissolved
substances in the solution is the same
as the concentration of dissolved
substances inside the cell
Hypertonic solution
• The concentration of solute
molecules in the solution outside the
cell is higher than the concentration
inside the cell.
Hypotonic solution
• A solution where the concentration
of dissolved substances in the
solution is lower outside the cell than
the concentration of solute molecules
inside the cell
Diffusion
• The movement of molecules from an
area of high concentration to an area
of lower concentration
Osmosis
• The movement of water molecules
across a membrane from an area of
high concentration to an area of low
concentration
Equilibrium
• Occurs when the concentration of a
substance is the same throughout a
space
• When a cell is placed in an isotonic
solution, there is no net movement of
water. The cell size remains the
same
• When a cell is placed in a hypertonic
solution, water diffuses out of the cell
and the cell shrinks.
• When a cell is placed in a hypotonic
solution, water diffuses into the cell
and the cell swells and may burst.
Passive Transport
• Movement of substances across the
cell membrane that does not require
any energy.
• Substances move down their
concentration gradient.
Types of Passive Transport
•
•
•
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Diffusion
Osmosis
Facilitated diffusion
Ion channels
Facilitated Diffusion
• Substances move down their
concentration gradient across the
cell membrane with the assistance of
carrier proteins
Facilitated Diffusion
Carrier Proteins
• Proteins embedded in the cell
membrane that aid in the transport
of substances across the cell
membrane
Ion channels
• Proteins embedded in the cell
membrane that provide a
passageway across the cell
membrane for the diffusion of ions
Active Transport
• Movement of substances across the
cell membrane that requires energy.
• Substances move against their
concentration gradient from an area
of low concentration to high
concentration.
Types of Active Transport
• Sodium- Potassium Pump
• Endocytosis
• Exocytosis
Sodium- Potassium Pump
• Carrier proteins transport sodium
(Na+) and potassium (K+) ions
across the cell membrane against
their concentration gradients.
• Moves Na+ out of the cell and K+
inside the cell
Sodium- Potassium Pump
Endocytosis
• Process where cells ingest
substances.
• The substances are enclosed by a
portion of the cell membrane that
folds into itself to form a pouch that
separates from the cell membrane.
Vesicle
• Membrane “pouch” containing
either ingested substances or
substances to be released from the
cell.
Exocytosis
• Process where cells release
substances to the outside of the cell.
• The substances are contained inside
a vesicle that fuses with the cell
membrane releasing the substance to
the outside of the cell.
Exocytosis