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Some Major Concepts in Biology: 

Some Major Concepts in Biology Evolution Living things share characteristics Cells are the basic unit of life Hierarchical organization Chapter 1 in textbook

Living organisms possess all of these characteristics: 

Cellular organization Living things consists of one or more cells Cells are organized Change over time Many living things grow Living things evolve or go extinct Interaction Within an organism (cells, organs) Between organism and its environment Between different organisms Living organisms possess all of these characteristics

Slide3: 

Reproduction Have a blueprint of their characteristics (genes) Produce offspring similar to themselves Transformation of energy Acquire and use energy Carry out and control numerous chemical reactions Emergent properties The whole is equal to greater than the sum of the parts Living organisms possess all of these characteristics

3. Cells are the basic unit of life: 

3. Cells are the basic unit of life All organisms consist of cells Cell membranes separate an organism from the external environment All cells originate from preexisting cells Organisms have evolved from single celled to multicellular

4. Hierarchy of organization: 

4. Hierarchy of organization Biology is organized into a hierarchy of levels: Atomic particles - elements Elements – molecules Molecules – cells Cells – tissues Tissues – organs Organs – systems Systems – organisms Organisms – populations Populations – communities Communities - biosphere

Biological Chemistry: 

Biological Chemistry Why are we studying it? Water Polar structure Hydrogen bonds between water molecules Carbon & biologically important molecules Carbohydrates Lipids Proteins Nucleic acids

B. The importance of water chemistry in biology: 

B. The importance of water chemistry in biology Water is the most abundant molecule in living organisms Water has chemical properties important for life An individual water molecule (H2O) is polar: Neither positive or negative One end is slightly negative Other end slightly positive

Polarity of water molecules makes it a good solvent: 

Polarity of water molecules makes it a good solvent Water molecules surround other molecules & forms bonds with them – dissolves them Polar and charged molecules dissolve easily (Na+, Cl-) Non-polar substances do NOT dissolve easily (oil) Polarity of water also means that it can be contained in membranes (which are non-polar) Salt dissolving in water

b) Water molecules form hydrogen bonds with each other: 

b) Water molecules form hydrogen bonds with each other Bonds form between slightly negative oxygen of one molecule with slightly positive hydrogen of another nearby water molecule forming hydrogen bonds hydrogen bonds Many hydrogen bonds together are fairly strong Large amount of energy required to break hydrogen bonds Large amount of energy stored in formation of hydrogen bonds This energy exchange

Because hydrogen bonds strongly bind H2O molecules, water has certain properties important for life:: 

Because hydrogen bonds strongly bind H2O molecules, water has certain properties important for life: Cohesion: Water molecules stick together Water can be pulled up vessels – plants, tree tops Surface tension: Surface of water difficult to puncture Skimming insects Density of water: Maximum density of water at 4oC H-bond orientation increases space between molecules when frozen Ice floats – bodies of water freeze from top down Life persists under ice

Because large amount of energy required to break hydrogen bonds between water molecules water has Thermal properties important for life:: 

Melting and freezing High energy input to melt ice or freeze water Moderates earth’s temperature – slow melting and freezing Heating and cooling High specific heat – energy required to change water temp 1oC Temperature of bodies of water heat & cool slowly Temperature of animal bodies are stable Evaporation High heat of vaporization – energy required to change water to gas Evaporation of water releases large amount of heat Evaporative cooling - sweating Because large amount of energy required to break hydrogen bonds between water molecules water has Thermal properties important for life:

C. Ionization of water molecules: 

C. Ionization of water molecules Water ionizes (splits) to form a proton, H+, and a hydroxyl ion, OH- Reaction is reversible Some substances dissolve in water and release H+ (acids) Some dissolve in water & release hydroxyl ions OH- (bases) HCl is an Acid Increases H+

Ionization & pH: 

Ionization & pH pH scale indicates strength of a solution of an acid or base Scale 1-14 H+ & OH- concentrations in water are about equal (10-7 moles/liter) Water has a pH of 7 & is neutral – neither an acid or base Low pH (acidic) = greater concentration of H+ High pH (basic) = greater concentration of OH- Most biological fluids have a pH between 6-8