Maintenance of Homeostasis “Cellular Transport”

Homeostasis is… A biological balance

Passive Transport Passive Transport is the movement of molecules with out using energy –The way the food coloring moves when dropped in water. –The way perfume makes its way through the classroom.

Diffusion To remain alive cells, tissues, and organs must maintain a balance between themselves and the environment. This balance is called homeostasis.

Molecules are in constant motion. This motion is called Brownian motion. Molecules tend to move from areas of high concentration to areas of low concentration. This is called diffusion. Examples  Ink in water  Sugar in tea  Perfume in the airBrownian motion

Concentration gradient is the difference in the concentration of a substance across space. Equilibrium is when the concentrations across space are equal. This is the goal of diffusion.

Concentration Gradient and Equilibrium Concentration Gradient Gradient is lessening Equilibrium has been reached

Diffusion across a membrane o Some molecules move freely across membranes. o Some membranes are selectively permeable; they allow some molecules to pass through while others may not.

Why is it incorrect to say that there is no movement during equilibrium? Atoms are always in motion – even in a solid

Osmosis Osmosis is the diffusion of water.

Hypertonic Higher concentration of solutes outside of cell Water will move out of the cell Plant: Plasmolysis (wilting)Plasmolysis Animal: Shrivel

Hypotonic higher concentration of solutes inside of cell Water will move into the cell Plant: Turgid Animal: Cytolysis (Cell rupture)

Isotonic equal concentration of solutes inside and outside of cell Water will move into and out of the cell equally Plant: flaccid Animal: equilibrium

Role of Osmosis o Turgor pressure- the pressure of the water in the cell membrane against the cell wall. o Contractile vacuoles- found in freshwater unicellular organisms. The function to remove excess water.

Your Cells Have a membrane made of a lipid bilayer that is selectively permeable. –Lipids are a class of organic molecules that are hydrophobic. –Lipids include: fats, oils, waxes and steroids. Please write this on your notes…

Your Cells Not everything can get into or out of the cell as quickly or as easily as it needs to by passive transport, so other methods are needed. Do Not Write This

Facilitated Diffusion Facilitated diffusion uses Carrier Molecules to speed up diffusion of some molecules across the cell membrane. Ex. glucose, water Carrier Molecules change shape to transport the molecules across Facilitated diffusion Insulin is a hormone that makes the molecule change shape to let glucose into the cell Insulin

Active transport  Moves molecules against concentration gradients, using energy in the form of Adenosine Tri-Phosphate (ATP)  Molecules use the energy to change shape

Endocytosis and Exocytosis Endocytosis- Where cells surround materials too large to pass through the membrane. o Pinocytosis- movement of liquids o Phagocytosis – movement of food Exocytosis- Where cells pass waste molecules out of the cell.