Lecture on Biological Hierarchy and Chemistry

Introduction

• Review the lecture slides in detail, especially those quickly covered.
• The focus begins with the first level of biological hierarchy: chemical structures.

Key Concepts

• Atoms and Molecules:

  • Atoms combine to form molecules.
  • Emergent properties arise from new combinations.
  • Matter is composed of elements, the smallest unit retaining properties.

• Examples of Emergent Properties:

  • Sodium (toxic) + Chlorine (toxic) = Sodium Chloride (non-toxic).

Elements and Compounds

• Common Elements in Biology:

  • Oxygen, Carbon, Hydrogen, Nitrogen (~96% of body mass).
  • Other elements like Potassium, Sodium, Phosphorus, Sulfur also important but in smaller quantities.

• Trace Elements:

  • Important in minute amounts (e.g., Iodine, Iron).

Atomic Structure

• Basic Atomic Composition:

  • Composed of protons (positive), neutrons (neutral), and electrons (negative).
  • Protons determine the atomic number and identity of an element.
  • Atomic mass includes protons, neutrons, and electrons.

• Isotopes:

  • Variants of elements with different neutron counts, some are radioactive.

Electron Configuration

• Electrons exist in shells around the nucleus.
• Electron Shells:
  • First shell: max 2 electrons.
  • Second and third shells: max 8 electrons.
• Valence Shell:
  • The outermost shell, determines reactivity.

Chemical Bonds

• Types of Bonds:

  • Covalent Bonds: Strongest, share electrons (e.g., H2O, CH4).
  • Ionic Bonds: Weaker, result from electron transfer (e.g., NaCl).
  • Hydrogen Bonds: Weaker, form between polar molecules.
  • Van der Waals Interactions: Very weak, temporary attractions.

• Electronegativity:

  • Oxygen and nitrogen are highly electronegative, leading to polar covalent bonds.

Chemical Reactions

• Definition: Making and breaking of chemical bonds to form new substances.
• Must be balanced (same number of each atom in reactants and products).
• Reversibility and Equilibrium:
  • Reactions can be reversed; equilibrium is when forward and reverse rates are equal.

Applications and Examples

• Biochemical Reactions:
  • Photosynthesis and respiration are key examples involving these chemical principles.

Conclusion

• The lecture covers the foundational chemistry for biological systems.
• Next focus will be on water molecules and their role in supporting life.

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Note: Pay attention to periodic trends and element reactivity, as well as the significance of chemical bonds in biological systems.