Lesson Overview 7.3 Cell Transport

Welcome to the border patrol of the cell:) THE CELL MEMBRANE How do cells move materials in and out,? Think of the cell a nation (they have borders) Cells have borders-separates from the surroundings & lets things in & out  

Passive Transport Every living cell exists in a liquid environment. One important function of cell membrane is to keep cell’s internal conditions constant (homeostasis) *Regulates movement of molecules from 1 side of the membrane to the other side. Cell Membrane is like the border patrol-lets things in & out

Diffusion ***particles tend to move from an area where they are more concentrated to an area where they are less concentrated. Diffusion-the process by which particles move from an area of high concentration to an area of lower concentration

Diffusion 1.) a substance is present in unequal concentrations on either side of a cell membrane. 2.) If the substance can cross the cell membrane, its particles will tend to move until it is evenly distributed. 3.) Even when equilibrium is reached, particles of a solution will continue to move across the membrane in both directions.  

Diffusion

Diffusion Passive Transport-the movement of materials across the cell membrane WITHOUTUSING ENERGY!!! NO ENERGY NEEDED, IT JUST HAPPENS

Facilitated Diffusion Facilitate-to make easier (help) Membranes have proteins carriers (channels) that make it easy for certain molecules to cross. ** Facilitated diffusion- process where molecules that cannot directly diffuse across the membrane pass through special protein channels. -A form of passive transport(NO ENERGY REQUIRED)

Osmosis: An Example of Facilitated Diffusion Cell membrane= *lipid bilayer (lipid=fat bilayer 2 layers) *hydrophobic—“water-hating.” -H2O molecules have a tough time passing through the cell membrane. osmosis!!!!!! NO WE ARE NOT WATCHING OSMOSIS JONES!!!!

Osmosis: An Example of Facilitated Diffusion Osmosis-the diffusion of water through a selectively permeable membrane. Osmosis involves the movement of water molecules from an area of higher concentration to an area of lower concentration.

How Osmosis Works Semi-permeable -lets certain substances pass and other substances not to pass Below, the barrier is permeable (let pass)-water Impermeable (does not let pass)-sugar

How Osmosis Works More sugar molecules on the right side of the barrier. concentration of water is lower. Water is crowded! If membrane lets water pass & not sugar, where will water go? Water wants to go from are of high concentration to low

How Osmosis Works Net movement of water into the are with the concentrated sugar solution. Water will move until equilibrium is reached. Equilibrium-concentrations of water will be the same on both sides.

How Osmosis Works isotonic-“same strength.” same on both sides. hypertonic- “above strength” blood cell in salt water hypotonic-“below strength.” blood cell in fresh water

Osmotic Pressure Organisms must have a way to balance the intake and loss of water. osmotic pressure- The net movement of water out of or into a cell exerts a force.

Osmotic Pressure Cells are filled with salts, sugars, proteins, &other molecules -hypertonic cell (above concentration) to fresh water hypotonic solution (below concentration) Resulting in water moving into a cell -causing it to swell -even burst In plants movement of water into the cell causes the central vacuole to swell, but cell wall will hold it in place. Most cells in large organisms do not come in contact with fresh water, they are not in danger of bursting.

Osmotic Pressure Cells are bathed in fluids Blood cells are isotonic (concentrations of materials outside equal to those inside the cell.) Cells placed in an isotonic solution neither gain nor lose water.

Osmotic Pressure Hypertonic solution-water rushes out of the cell, causing animal cells to shrink and plant cell vacuoles to collapse.

Osmotic Pressure Other cells, including those of plants and bacteria, that come into contact with fresh water are surrounded by tough cell walls that prevent the cells from expanding, even under tremendous osmotic pressure.

Passive Transport What is passive transport?

Passive Transport What is passive transport? The movement of materials across the cell membrane without using energy is called passive transport.

Active Transport Cells sometimes move materials against a concentration difference. Active transport -the movement of material against a concentration difference. (requires energy (ATP) )

Active Transport The active transport of small molecules or ions is carried out by transport proteins, or protein “pumps,” Larger molecules and clumps of material can also be actively transported by endocytosis and exocytosis

Active Transport

Molecular Transport Many cells use such proteins to move calcium, potassium, and sodium ions across cell membranes.

Endocytosis-stuff going in Endocytosis-taking material into the cell Phagocytosis- extensions of cytoplasm surround a particle and package it within a food vacuole. In pinocytosis, cells take up liquid from the surrounding environment by forming tiny pockets along the cell membrane. The pockets fill with liquid and pinch off to form vacuoles within the cell.

Endocytosis

Exocytosis -stuff going out Exocytosis-cells also release large amounts of material from the cell   During exocytosis, the membrane of the vacuole surrounding the material fuses with the cell membrane, forcing the contents out of the cell.

Active Transport What is active transport?

Active Transport What is active transport? The movement of materials against a concentration difference is known as active transport. Active transport requires energy.