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The Importance of Chemistry in Biological Systems

Understanding the role of chemistry in biology is essential for appreciating life. It begins with atoms, the fundamental particles that combine to form elements like carbon, hydrogen, and oxygen—key to living organisms. Chemical compounds form through bonds like covalent and ionic interactions, crucial for molecular structure. Water's unique properties, influenced by its polar nature and hydrogen bonds, are vital for life, affecting everything from cellular composition to temperature regulation. This interplay between chemistry and biology explains how life functions on a molecular level.

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The Importance of Chemistry in Biological Systems

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  1. Why Study Chemistry in Biology?

  2. I. The Atom A. Definition: smallest particle of an element

  3. B. Composition

  4. Location of Electrons Valence electrons: outermost electrons, participate in BONDING

  5. II. Elements A. Definition: substance that cannot be broken down into other substances B. Biologically important elements i. Major: C H O N P S ii. Minor: Ca Fe Mg I Se P K Na Cl

  6. III. Chemical Compounds A. Compound definition: a substance containing two or more elements in a fixed ratio • Ex: H2O, NaCl

  7. B. Bonds: • Atoms want to fill their outer energy levels to be • To do this, they will meet up with other atoms and either or electrons complete exchange share

  8. C o v a l e n t B o n d : 
s h a ri n g I s c a r I n g • Atoms share electrons so that both atoms fill their outer energy level

  9. Examples of covalent molecules

  10. ii. Ionic Bonds: gimme’ that electron! • Atoms transfer electrons, becoming (+) or (-) charged • This attraction brings them together • Ex: Na and Cl

  11. iii. Molecules definition: two or more atoms held together by COVALENT bonds

  12. V. WATER LIFE DEPENDS ON THE UNIQUE PROPERITIES OF WATER

  13. Questions to think about • Why do put salt on the roads? • Why do we add salt to a pot of pasta water? • At a higher altitude why must we cook “boil” something longer?

  14. Human Composition: Cells are 70–90% water

  15. B. Plant Composition As much as 95% plants can be made of water

  16. C. Formula: H2O

  17. D. Bonds: i. Hydrogen bonds: the slightly (+) H atoms are attracted to nearby (-) O atoms, and develop a weak bond.

  18. Hydrogen Bonds • Hydrogen Bonds- weak bondsslightly positive H is attracted to the slightly negative O of another water molecule

  19. E. Polarity • Polar molecule: molecule in which opposite ends have opposite electric charges • Why? Water is a polar molecule: because Oxygen holds electrons closer

  20. The polar nature of water and the effects of hydrogen bonding explain most of water's unique properties. • Cohesion • Adhesion • Solubility • Temperature moderation • The lower density of ice

  21. 1-inchpaperclip over-filled water 3oz Dixie cup i. Cohesion 1. Definition: Water “sticks” to each other Ex.: Surface tension

  22. Jesus Christ Lizard

  23. ii. Adhesion 1. Definition: Water molecules are also attracted to certain other molecules. 2. Ex. In trees/plants water goes against gravity Called capillary action

  24. iii. Temperature and Water Boiling Point: 100 oC / 212 oF • When you heat molecules move faster • When you cool molecules move slower • Water takes more energy to heat because energy must break hydrogen bonds

  25. Does water boil faster if you add salt to it? • Water Boils when it has enough energy for the molecules to leave

  26. Freezing Point 0 oC or 32 oF • What would happen if our oceans did not have salt in them? • Why do we put salt on our roads? • Why at effect does salt have on FREEZING POINT?

  27. LOW DENSITY OF ICE • Density- amount of matter in a volume • In most substances the solid state is more dense than the liquid state • Water is the opposite ICE IS LESS DENSE THAN WATER and will FLOAT

  28. LOW DENSITY OF ICE • WHY? • Hydrogen bonds in ice (solid) keep molecules spaced out

  29. LOW DENSITY OF ICE • Floats • Ice insulates the liquid water below allowing life to persist

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