Transport - Valhalla High School

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Transcript Transport - Valhalla High School

• The movement of
molecules and ions
across a membrane
Molecules in motion
• At all times molecules and ions are
moving into and out of your cells.
• The nutrients and oxygen your cells
need for respiration move in, and the
waste products move out.
• This activity is regulated by the cell
• As we learned earlier, transport (the intake
and distribution of materials throughout an
organism) is one of the life processes.
• All molecules are not transported the same.
• Some types of transport require energy and
others do not.
• Sometimes molecules need a little help
getting from one side of the cell membrane to
the other.
Types of transport
I. Passive transport
II. Active transport
III. Endocytosis (Phagocytosis and
IV. Cyclosis
Passive transport
• In passive transport there are two things that
you must remember.
1. There is no energy required.
2. Molecules move from areas of high concentration
to low concentration.
– Small molecules easily pass through the cell
membrane while larger ones need help.
– With ions, the charge of the particles can also
determine if they can diffuse across a cell
Simple Diffusion
• Small molecules, such as dissolved
oxygen, carbon dioxide and glucose
pass through the cell membrane.
• They always move with the
concentration gradient, from high to low.
• No energy is required.
Facilitated diffusion
• Sometimes molecules are too big to pass
through the cell membrane on their own.
• These larger molecules require the help of
carrier proteins. Carrier or channel forming
proteins are embedded in the cell membrane.
• As with simple diffusion, no energy is
required, and molecules and ions move with
the concentration gradient.
• Osmosis refers to the passive transport of
water molecules across a cell membrane.
• As with the other times of passive transport
the water molecules move from high
concentration to low concentration.
• No energy is required for Osmosis.
Diffusion summation
• No energy
• Molecules move with the gradient
• Continues until equilibrium is reached.
This means that the concentration of
molecules are the same on both sides
of the membrane.
Passive transport video
Active transport
• Active transport is fundamentally
different from passive transport.
• In active transport, molecules move
against the concentration gradient,
which means they move from areas of
low concentration to high concentration.
• It also requires energy.
• Endocytosis simply means the ingestion of solids or
liquids into a cell.
• Phagocytosis is the process by which solids are
taken into a cell. An amoeba eats paramecium by
the process of phagocytosis.
• Pinocytosis is the process by which liquids are taken
into a cell.
• Both phagocytosis and pinocytosis lead to the
production of vacuoles.
• The reverse process, of materials leaving a cell is
called exocytosis.
Passive v. active transport
• Cyclosis is the swirling motion of the
cytoplasm that helps to distribute
materials throughout a cell.
• Cyclosis does not directly require any
energy. The normal motion of the cell or
organism helps to create this motion.