Larger cells do not function as efficiently – The surface is the only way cells interact with the environment – Surface-area-to-volume ratio As cell size increases, volume grows much more rapidly Why are cells so tiny? Cell radius (r)Surface area (4πr 2 )Volume ((4/3)πr 3 ) 1 units12.57 units units 3 10 units1,257 units 2 4,189 units 3

Cell Theory Schleiden and Schwann Three principles – All living things are composed of cells – Cells are the smallest living things (Functional units of the body) – Cells come from pre-existing cells

Prokaryotes – Lack a nucleus and membrane bound organelles – MUCH smaller than eukaryotes – Bacteria Eukaryotes – Have a nucleus and organelles – Much bigger than prokaryotes Cell Types

Cell membrane – Semi-permeable Cytoplasm— “cell blood” – Fluid matrix surrounding nucleus – Surrounded by a cell membrane Nucleus— “cell brain” – Contains chromatin (loosely coiled DNA) Cell Organelles

Interconnected membranes forming canals and flattened sac-like spaces Functions: – Communications system – Rough ER: studded with ribosomes Involved in protein synthesis – Smooth ER: has no ribosomes Involved in synthesizing lipid Endoplasmic reticulum

Composed of protein and RNA May be free in the cytoplasm or attached to ER Function: – Involved in protein synthesis Ribosomes

Stack of flattened membranes Function: – Package and transports proteins from the cell Golgi apparatus

“Cell powerhouse” Contains its own DNA – Capable of self-reproduction Composed of 2 membranes Contains enzymes used in cell respiration Function: – Produce ATP for cellular energy (cell respiration) Mitochondria

Small sacs from the Golgi apparatus Contains enzymes capable of breaking down breaking down nutrients or toxins Function: – Digestion Lysosomes

Twin hollow cylinders (centrioles) Function: – Involved in cell division Centriole

Tiny sacs formed by the cell membrane folding in and pinching off Function: – Intake or excretion of large materials (endocytosis and exocytosis) Vesicles

Tiny rods usually arranged in meshes or bundles Function: – Involved in cell movement – Provides structure to the cell Microfilaments and Microtubules

Fine, long, threadlike organelles protruding from the cell surface Function: – Cell movement Cillia and Flagella

nucleus smooth ER lysosome Golgi apparatus vesicles centrosome mitochondria flagella rough ER

Selectively permeable (semi-permeable) – Allows some substances in, excludes others Composed of phospholipid bilayer (containing cholesterol) and protein inclusions – Fat soluble molecules pass through the lipid part – Water soluble molecules must move through protein component Pores, channels or receptors Cell Membrane

Passive Transport Movement of a material into or out of a cell without the use of energy. – Diffusion – Osmosis – Facilitated diffusion – *** NO ENERGY REQUIRED***

The process by which molecules move down a concentration gradient – Move from area where there is more concentration to areas that are less concentrated – Rate limited by concentration Diffusion

Diffusion using special carrier molecules to allow usually non-permeable molecules to pass through a selectively permeable membrane – Example: Insulin facilitates glucose movement Rate of passage is limited by the number of carrier molecules and concentration Facilitated Diffusion

The diffusion of water through a selectively permeable membrane which may not allow dissolved substances to pass May result in changing volumes on either side of the membrane Osmotic pressure – The amount of pressure needed to stop osmosis Osmosis

Hypertonic – A solution which has a greater concentration of solute particles than a given cell or solution Hypotonic – A solution which has a lesser concentration solute particles than a given cell or solution Isotonic – A solution which has an identical concentration of solute particles to a given cell or solution Concentration Types

The forcing of permeable molecules through a membrane by hydrostatic pressure – Example: Blood pressure Filtration

The movement of molecules against a concentration gradient using cellular energy and carrier molecules – Proton pump – Sodium-potassium pump Active Transport ***ENERGY REQUIRED***

Endocytosis – The inward movement of molecules through a membrane by infolding and pinching off vesicles Pinocytosis: taking in tiny droplets of liquid Phagocytosis: taking in solid material Receptor Mediated: molecule bonds with receptor protein Exocytosis Bulk Passage

Prokaryotes – Binary fision DNA replicated in parent Parent divides Fast Eukaryotes – Mitosis Complicated Lots of DNA – Form chromosomes (compact structures, composed of DNA and histone proteins, that can be manipulated easily during cell division Cell division

Interphase – Period “Inbetween” cell division – Majority of cell’s life Cell growth Protein synthesis Cell cycle

Cell division that Is Mighty Common Makes all cells EXCEPT gametes (reproductive cells) DNA is doubled then – Cells divide once Mitosis

Cells Prepares to divide Chromatin condenses into chromosomes Nuclear membrane disappears Prophase

Chromosomes line up in the Middle Spindle Apparatus stretches from pole to pole Metaphase

Sister chromatids move Away to opposite poles Anaphase

Cell “Tears” in two Nuclear membrane reforms Chromosomes disperse into chromatin Cytokinesis (cytoplasmic division) (separate phase?) – Produces 2 identical “daughter cells” Telophase

Process by which cells develop different characteristics in structure and function Differences in outcome – Directed by cell’s DNA – Determined by cell’s position in the body and its chemical environment Cell differentiation