Cell consists of nucleus and cytoplasm. • In cytoplasm - organelles (“little organs”)
Cell membrane – boundary of cell. • Membrane thin but selectively permeable (allows certain materials to pass through but not others).
Membrane has receptors that help receive messages (i.e. hormones) • Called phospholipid bilayer (composed of phospholipids); also various proteins in membrane.
1Endoplasmic Reticulum – increased surface area for reactions to take place. • ARough ER – Makes proteins (holds ribosomes) • BSmooth ER – Makes lipids.
2Ribosomes – some attached to rough ER (bound); some scattered throughout cytoplasm (free). • Function - protein synthesis.
3Golgi apparatus – proteins modified and packaged, then sent into cytoplasm.
Modified protein http://web.mit.edu/esgbio/www/cb/org/golgi.gif
4Mitochondria – cellular respiration. • Transform glucose into form of energy cell can use.
5Lysosomes – contain enzymes that break down molecules of foreign particles (“garbage cans” of cell)
6Centrosome – consists of 2 hollow cylinders (centrioles) - function in reproduction by separating chromosomes to new cells.
7Cilia and 8flagella – extensions of cells; used for cell movement. • Flagella - longer and fewer. • Cilia - smaller and more numerous.
http://pediatrics.med.unc.edu/div/infectdi/pcd/images/cilia.jpghttp://pediatrics.med.unc.edu/div/infectdi/pcd/images/cilia.jpg Respiratory cilia
9Vacuoles – vesicles found in cell that have various functions. • AFood vacuole – breakdown of food. • BCentral vacuole – storage of waste. • CContractile vacuole – removal of water (osmoregulation).
10Microfilaments and microtubules – responsible for movement within cell (also responsible for structure)
11Nucleus – center of cell. • Covered by nuclear envelope with pores to allow substances to pass through. • Contains 12nucleolus (ribosome production) and chromatin (loose DNA).
Membrane Structure • Plasma membrane of cell selectively permeable (allows some substances to cross more easily than others) • Made mostly of proteins and lipids (phospholipids). • Phospholipids and proteins create unique physical environment (fluid mosaic model)
Membrane - bilayer - hydrophilic (water loving) heads pointing outwards, hydrophobic (water fearing) tails pointing inwards. • Proteins help membrane to stick to water.
Fluid because lipids and proteins can move laterally. • As temperatures drop, liquid membrane can solidify. • Saturated fatty acid tails - more solid than unsaturated fatty acid tails.
Cholesterol found in membrane helps with fluidity of membrane. • Membranes need to be fluid to work properly - systems in place to help keep it fluid.
Two different types of proteins are found in membrane. • 1Peripheral proteins not in membrane, bound to surface of protein. • 2Integral proteins in membrane often spanning entire membrane.
Membrane helps keep cell’s shape. • Also aids in cell-to-cell recognition (ability of a cell to distinguish one type of neighboring cell from another)
Some substances move steadily across membrane (sugars, ions, and wastes like CO2) • Hydrophobic molecules (i.e. hydrocarbons, CO2, and O2) can dissolve in lipid bilayer and cross easily.
Charged particles and polar molecules have more difficulty passing. • Specific ions and polar molecules can cross lipid bilayer by passing through transport proteins that span membrane.
Diffusion - tendency for substance to spread out in open area. • Permeable membrane separating a solution with dye molecules from pure water, dye molecules will cross barrier randomly.
No force acting upon it - substance will tend to move down it’s concentration gradient from where it is more concentrated to less concentrated (passive transport).
Diffusion of molecules with limited permeability through lipid bilayer may be assisted by transport proteins (facilitated diffusion)
Difference in concentration - ions move from one area to other. • Solution with higher [ ] solutes - hypertonic. • Solution with lower [ ] solutes -hypotonic. • [ ] equal - isotonic.