How organisms maintain balance

Essential Standards 1.2 Analyze the cell as a living system Explain how homeostasis is maintained in the cell and within an organism in various environments (including: temperature and pH)

The case of Jennifer Strange  On January 12, 2007, she participated in a radio contest – “hold your wee for a wii”- so she could win the game system for her children

Strange case cont’d  She won 2 nd place and won 2 tickets to Justin Timberlake  She complained of a headache before leaving the station  Her body was discovered a few hours later at her home, no physical trauma

The death of Andy Warhol  Famous for paintings of Campbell’s soup cans and Marilyn Monroe  Died in the hospital while recovering from gallbladder surgery on Feb. 22 nd 1987

Mysterious deaths  What killed these people???  …both of these people died from the same thing

Transport  Transport- describes all the processes that move materials within an organism into and out of cells  ALL organisms use transport, prokaryotic, eukaryotic, unicellular, multicellular  Life processes take place inside of cells of organisms

Cells and Transport  Materials must enter and leave cells through the plasma membrane (aka. cell membrane)  Moves through diffusion, osmosis, active transport

Homeostasis  Cells must be able to maintain “balance” internally  Aka: equilibrium  Plasma membrane controls homeostasis  Cells need to maintain proper pH, glucose levels, water balance, and temperature

pH  pH describes how acidic or basic a substance is  Hydrogen ions (H+) and hydroxide ions (OH-)  Cells need to maintain a constant pH  pH affects the rates of many biochemical reactions

Buffer  A substance used to maintain a stable pH  Adding acid or base to a buffered solution has almost no effect on the pH

Temperature  Cells cannot function if temperature is too high  Shivering and sweating are used to maintain homeostasis

Plasma membrane  Protective barrier  Regulates transport  Semi-permeable  Allows cell recognition  Provides anchoring sites for cytoskeleton

Plasma membrane structure PhospholipidsCarbohydrates Cholesterol Proteins (integral & peripheral)

Phospholipids  Make up the cell membrane  Have a phosphate head -PO 4  Hydrophillic (water loving)  Fatty acid tails  Hydrophobic (water fearing)

Fluid Mosaic Model  Fluid – individual phospholipids and proteins can move side to side in the layer like a liquid  Mosaic – due to pattern produced by phospholipids when viewed from above

Selectively permeable  “Selectively”- membrane only allows certain materials in and out  “Permeable” – materials can cross into and out of the membrane

Solubility  Materials that are soluble in lipids (fats) can pass easily through the membrane  Small molecules and larger hydrophobic molecules can move through easily  O 2, CO 2, H 2 O,

Solubility cont’d  Ions and larger hydrophilic molecules do not pass through the membrane on their own  Larger than water  Such as proteins

Passive transport  Passive – no energy is required  Molecules have a natural kinetic energy  Simple Diffusion – requires no energy  High concentration  low concentration

Diffusion of liquids

Diffusion through a membrane High  low

Osmosis  Diffusion of water across a membrane  High water potential  low water potential Water Solute

Water  One of the most important substances organisms must transport  Most of the cytoplasm is made of water  Many materials are dissolved in water  Cells need to take in enough but not too much  Helps maintain salt concentrations and pH

Cell in isotonic solution 10% NaCl 90% H2O Cell 10% NaCl 90% H2O Which way does the water move?

Cell in Hypertonic Solution 80% H2O 20% NaCl Cell 90% H2O 10% NaCl Which way will the water move?

Cell in Hypotonic solution 10% NaCl 90% H2O Cell 25% NaCl 75% H2O Which way will the water move?

Diffusion in Red Blood Cells IsotonicHypotonicHypertonic

Isotonic Solution NO NET MOVEMENT OF H 2 O (equal amounts entering & leaving) Hypotonic Solution CYTOLYSIS Hypertonic Solution

3 types of diffusion 31

Facilitated Diffusion  Doesn’t require energy – still passive transport  High concentration  low concentration  Uses transport proteins  Examples: glucose and amino acids

Transport proteins  Channel proteins – embedded in the membrane and have a pore for materials to cross  Carrier proteins – change shape to move materials from one side to the other  Bond and drag materials to the other side

Purposes of protiens

Active Transport  Uses energy in the form of ATP  Moves materials from low  high concentration  What’s the difference in active and passive transport?  Move AGAINST concentration gradient

Sodium potassium pump  Cellular membrane pump  Example of active transport  Na+ ions and K+ ions are pumped AGAINST their gradient  3 Na pumped in for every 2 K+ pumped out

Moving larger materials  Exocytosis – materials are moved out of the cell by vesicles that fuse with the cell membrane This is the way hormones are secreted and nerve cells communicate

Endocytosis  Materials are taken into the cell using vesicles formed from the plasma membrane  3 forms  Pinocytosis  Phagocytosis  Receptor mediated endocytosis

Pinocytosis  Most common form of endocytosis  Takes in dissolved molecules using a vesicle  “drinking” function

Phagocytosis  “eating” function  Engulfs large particles  Such as food, bacteria, etc…

Receptor mediated endocytosis  Integral proteins in the cell membrane have receptors that can detect and recognize various molecules  Hormones, cholesterol, etc…