Homeostasis HomeoWhat Homeo Same Stasis State Homeostasis Maintaining

Homeostasis

Homeo-What? • Homeo= Same • Stasis= State • Homeostasis: Maintaining a constant internal balance – Example: When your body temperature is over 98. 6 o, 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 H 2 O and O 2 can pass through – Phosphate- Is polar and hydrophilic (water loving) – Lipid- Is non-polar and hydrophobic (water hater) • 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

Comp Book Time! Complete Catch It Questions 1 -2

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 http: //telstar. ote. cmu. edu/biology/Membrane. Page/index 2. html

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 • 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

• Osmosis: – The diffusion of H 2 O across a cell membrane – H 2 O moves from high concentration to lower concentration Not a lot of H 2 O=Lower concentration A lot of H 2 O=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 1. Hypotonic: – Hypo= lower – Concentration of solute molecules is lower in the environment than in the cell – H 2 O moves into the cell and it swells • Eventually the cell will burst if H 2 O does not move out of the cell (cytolysis)

Environment is 90% H 2 O 90% +10% Na. Cl= 100% Solution is 80% H 2 O 90% +20% Na. Cl= 100%

2. Hypertonic – Hyper= Higher – Concentration of solute molecules is higher in the environment than in the cell – H 2 O will leave the cell and it will shrink – Example: Dehydration

Environment is 80% H 2 O 80% +20% Na. Cl= 100% Cell is 90% H 2 O 90% +10% Na. Cl= 100%

3. Isotonic – Iso= equal – The concentration of the solute molecules is equal on both sides of the cell membrane – Cells neither gain nor lose H 2 O – Cells are in homeostasis

Comp Book Time! Complete Catch It Questions 3 -6

• Cytolysis: – An animal cell in a hypotonic environment will eventually swell and burst • 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 1. – – – Pinocytosis Pino= Drinking Cyto= Cell The movement of solutes or fluids into the cell

2. 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

Comp Book Time! Complete Catch It Questions 7 -10

Animal Type of cell - ______ hypertonic Type of solution - _______ 8. 5% Na. Cl 91. 5% H 2 O out How will water move? _____ 45% Na. Cl osmosis By what process? _______ 55% H 2 O in How will salt move? ______ diffusion By what process? ________ shrink in size What will happen to the cell? _______ plasmolysis Biological term - _________

Plant Type of cell - ______ 8. 5% Na. Cl hypotonic Type of solution - _______ 91. 5% H 2 O in How will water move? _____ osmosis By what process? _______ 0% Na. Cl Distilled water 100% H 2 O out How will salt move? ______ diffusion By what process? ________ swell and become rigid What will happen to the cell? _______ turgor pressure Biological term - _________