Download Notes - Cell Processes

Cell Processes
The Cell Membrane
• The membrane that surrounds the cell and its
organelles.
– Acts as a gateways between the outside environment
and a cell’s cytoplasm.
– Selectively permeable – allow only certain
substances in and out of the cell, not all substances.
Solutions
• Substances entering and leaving a cell,
through the cell membrane, are dissolved in a
liquid – solution.
– Solutions are mixtures of two or more substances.
• Substance that does the dissolving = solvent.
– Water is the universal solvent.
• Substance that is being dissolved = solute.
Solvent = water
Solute = sugar
Solution
Concentrations
• The amount of substances being dissolved compared
to the amount of substance doing the dissolving =
concentration.
– High concentration = high solute, little solvent
• Ex. Very sweet lemonade = lots of mix (solute), little
water (solvent)
– Low concentrations = little solute, high solvent
• Ex. Weak tasting lemonade = small amount of mix
(solute), lots of water (solvent)
Cell Transport
• Substances are transported into or out of a
cell in two ways:
– Passive Transport – No energy is required to move
the substances.
– Active Transport – Energy IS required by the cell
to move the substances.
BrainPop – Active Transport
Passive Transport
• Cells move materials from areas of high
concentration to areas of low concentrations
– concentration gradient.
• Depending on the substance being moved,
transport occurs in two ways:
– Diffusion = movement of particles
– Osmosis = movement of water
Diffusion
• When particles in a solution are in constant
motion, colliding, causing them to spread out.
– continue to move until concentration is the same =
Equilibrium.
Examples:
1. Oxygen moving from your lungs to your bloodstream
2. Carbon dioxide moving from your bloodstream to your lungs
3. Nutrients moving from your small intestine into your
bloodstream.
Equilibrium
Diffusion Through a Membrane
• Process of Diffusion – animation
Osmosis - Passive
• The movement of water into or out of the cell
from regions of high concentration to regions
of low concentration - Osmosis.
– Perhaps the most important substance that
passes through the cell membrane is WATER.
– Cells can’t function properly without adequate
amount of water.
BrainPop – Passive Transport
Osmosis
Water is at equilibrium!
Three solution types: Osmosis
1. Hypertonic Solution – higher water
concentration inside the cell than outside
a. Water will move out of the cell = shrink
Three solution types: Osmosis
2. Hypotonic Solution – higher water concentration
outside the cell than inside.
a. Water will move into the cell = swell
Three solution types: Osmosis
3. Isotonic Solution – equal concentrations of
water inside and outside the cell.
a. Water moves equally in and out of the cell.
Osmosis in Blood Cells
Isotonic
Hypotonic
Hypertonic
Active Transport
• Some materials must be moved against the
concentration gradient by active transport.
– Energy IS required!
• Two Methods:
– Molecule Transport
• The use of proteins in the membrane to move
substances across the membrane.
Cell Transport – Active Transport
– Endocytosis and Exocytosis
• Some cells take in or release materials through
movements of the cell membrane using energy.
Exocytosis