Homeostasis

Homeo-What? Homeo= Same Stasis= State Homeostasis: Maintaining a constant internal balance Example: When your body temperature is over 98.6o, your body is out of homeostasis Example: When you are dehydrated, your body is out of homeostasis

How do we maintain homeostasis? Cell Membranes! Surrounds the outer portion of an animal cell Is found inside of the cell wall of a plant cell

Cell Membrane Structure Phospholipid- Phosphate and lipid that forms the “wall” portion of the membrane Small molecules such as H2O and O2 can pass through Phosphate- Is polar and hydrophilic Lipid- Is non-polar and hydrophobic Protein-Protein portion that forms the “door” portion of the membrane Allows large molecules (such as Na and K) to pass into or out of the cell

Phospholipid Structure Phosphate-hydrophilic Outside portion of the cell membrane Lipid-hydrophobic Inside portion of the cell membrane

Semi-Permeable Membrane Cell membrane allows some molecules to enter and others to exit the cell Keeps unneeded molecules out of the cell Is also called selectively permeable membrane Outside of cell Inside of cell

Fluid Mosaic Model Cell membranes are in constant motion Is called the Fluid Mosaic Model Are moving to maintain homeostasis Letting certain molecules in and out as needed

How do cells move molecules? Cells maintain homeostasis by moving molecules in and out of the cell membrane Passive Transport Requires no cellular energy (ATP made by the mitochondria) Example: Osmosis and Diffusion Active Transport Requires the usage of ATP Example: Na/K pumps

Concentration Gradient

Passive Transport Also called unassisted transport No cellular energy (ATP) is used Diffusion The movement of molecules from an area of high concentration to low concentration

Equilibrium: When the concentration of molecules on both sides of the membrane are equal No more movement will happen Molecule of dye Membrane Equal on both sides

Facilitated Diffusion: Facilitate- “to help” Molecules that can not pass through the phospholipid layer pass through proteins Glucose Blood sugar

Fick’s Law of Diffusion The greater the steepness of the concentration gradient, the quicker diffusion occurs The more CO2 in the blood causes you to exhale more CO2 The larger the surface area of a membrane, more diffusion can occur Microvilli in intestine lining The more lipids in a substance, the quicker the substance can diffuse through a membrane The higher the molecular weight of a substance, the slower it will diffuse O2 and CO2- low molecular weights As the distance the molecules must travel increases, diffusion decreases

Osmosis: The diffusion of H2O across a cell membrane H2O moves from high concentration to lower concentration –With the concentration gradient Less H2O=Lower concentration Greater amount of H2O=Higher concentration

Just a reminder….. Solute: What is being dissolved Solvent: What is doing the dissolving Water is the universal solvent When making sweet tea- The water is the solvent The tea and sugar are the solutes

Osmosis creates different conditions for cells Hypotonic: Hypo= lower Concentration of solute molecules is lower in the environment than in the cell H2O moves into the cell and it swells Eventually the cell will burst if H2O does not move out of the cell (cytolysis)

Environment is 90% H2O 90% +10% NaCl= 100% Solution is 80% H2O 90% +20% NaCl= 100%

Hypertonic Hyper= Higher Concentration of solute molecules is higher in the environment than in the cell H2O will leave the cell and it will shrink Example: Dehydration

Environment is 80% H2O 80% +20% NaCl= 100% Cell is 90% H2O 90% +10% NaCl= 100%

Isotonic Iso= equal The concentration of the solute molecules is equal on both sides of the cell membrane Cells neither gain or lose H2O Cells are in homeostasis

Turgor Pressure: A plant cell is restricted by the cell wall A plant cell in a hypotonic environment will stand up to gain access to more sunlight Cells do not burst due to the cell wall

Plasmolysis: When a plant cell is in a hypertonic environment, water leaves the cell and the vacuole shrinks Plant wilting

Active Transport Cellular Energy (ATP) is used Moving molecules from an area of low concentration to an area of high concentration Na/K pumps in neurons

Endocytosis: Endo= into Cyto= cell Cell membranes change shape to allow large molecules to enter the cell Example: cells engulf protein molecules

Types of Endocytosis Pinocytosis Pino= Drinking Cyto= Cell The movement of solutes or fluids into the cell

Phagocytosis Phag= to eat Cyto= cell The movement of large particles or entire organisms into a cell Example: White Blood Cells (wbc), Amoeba

Exocytosis Exo= exit Cyto= cell Passage of large molecules to the outside of the cell The cell membrane changes shape Example: Waste products are secreted into the environment, Golgi Body secretions, Hormones

Type of cell - ___________ Animal Type of cell - ___________ 8.5% NaCl hypertonic Type of solution - _____________ 91.5% H2O out How will water move? _____ 45% NaCl osmosis 55% H2O By what process? ______________ in How will salt move? ______ diffusion By what process? _______________ shrink in size What will happen to the cell? _____________ plasmolysis Biological term - __________________

Type of cell - ___________ Plant Type of cell - ___________ 8.5% NaCl hypotonic Type of solution - _____________ 91.5% H2O in How will water move? _____ 0% NaCl Distilled water osmosis By what process? ______________ 100% H2O out How will salt move? ______ diffusion By what process? _______________ swell and become rigid What will happen to the cell? _____________ turgor pressure Biological term - __________________