Chapter 7.3 & 7.4

7.3 All organisms and all cells must maintain homeostasis (stable internal environment) and adjust to their environment. Cell membrane = plasma membrane  description – a lipid bi-layer (has 2 layers) w/ proteins that are stuck w/in it  Is selectively permeable – allows some things in & not others  Functions 1. Controls what gets into & out of the cell 2. Protects & supports the cell

Solution – mixture of 2 or more substances 1. solute – dissolved substance 2. solvent – does the dissolving 3. concentration – mass of solute in a given volume -12g/31 saline (salt) solution - 2x more concentrated -12g/61 saline solution 4. particles move constantly & randomly Cytoplasm – solution of many different substances Cell wall is found in plants, algae, fungi & many prokaryotes  located outside of the membrane  will allow water, O 2 & CO 2 to pass through easily  Main function → support & protection of the cell  Made by the cell

Diffusion – movement across a cell membrane from an area of high concentration to low concentration Facts  depends on random movement → requires NO energy  when concentration is the same throughout, equilibrium exists  when equilibrium is reached, there is no change in concentration & particles continue to move in both directions at the same rate

Osmosis – diffusion of water Sugar molecules are large & can NOT pass through the membrane Water molecules are small & pass easily Water will flow from high concentration to low concentration until equilibrium is reached

Types of Solutions Isotonic – same strength Hypotonic – below strength Hypertonic – above strength Direction of movement of water depends on the concentration of solutes

 For organisms to survive, it must balance intake & loss of water  Cell is filled w/ salts, sugars, proteins & other substances and is hypertonic to fresh water.  Water will move → the cell and it would burst Osmotic pressure –The pressure exerted by the flow of water through a semi permeable membrane separating two solutions with different concentrations. Turgidity -The state of being swollen, especially due to high fluid content. Ways to control swelling and/or bursting: 1. Plant & fungal cells – cell walls 2. Unicellular eukaryotes use contractile vacuoles – pumps out excess water 3. Animal cells – remove dissolved particles from the cytoplasm

Active Transport  Used when cells need to move substances against the concentration difference  Requires energy  Some processes use transport proteins or “pumps” to move molecules from low concentration to high concentration.

 Endocytosis – movement is from an area of lower concentration to higher concentration. A. Process 1. Cell membrane forms a vesicle around particles. vesicle = vacuole 2. Vesicle travels to the target organelle. 3. Vesicle may fuse with the organelle & release its contents. B. Two types B. Two types 1. phagocytosis – cell membrane forms a vesicle around large particles. example: white blood cell eating bacteria

2. Pinocytosis- cell membrane forms a vesicle around small particles to bring into the cell. ex: moving liquid into the cell Exocytosis – movement is out of the cell A. Process 1. Vesicle forms around small particles. 2. Vesicle moves to the cell membrane and fuses with it. 3. Vesicles releases contents outside of the cell B. Used to export proteins released by the ER or Golgi apparatus.

7.4 Diversity of Cellular Life Sometime the cell is the organism → Unicellular organism – one celled organism They do everything other organisms do Ex. Yeast, bacteria

Multi-cellular Organisms – more than one cell (many cells) –Need specialized cells –Cell specialization – process of cells developing in different ways to perform different tasks –Ex:  red blood cells – carry oxygen  Muscle cells – packed with cytoskeleton fibers to allow movement

Levels of organization 1. Cell 2. Tissue – similar cells that perform a particular function 4 types include: 1.Epithelial 2.Muscle 3.Nervous 4.Connective 3. Organ – group of tissues that work together to perform a job Ex: stomach 4. Organ system – a group of organs that work together to perform a specific function Ex: digestive system