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 air

• 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)• 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

• Insulin is a hormone that makes the molecule change shape to let glucose into the cell

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.