Chemistry Grading System Overview

Grading System

• Minimum passing grade is 60% of total scores.
• Criteria breakdown:
  • Performance Task (40%): includes attendance, assignments, seatwork, and research/critique paper.
  • Recitation/Class Participation (15%).
  • Major Examination (30%).
  • Quizzes (15%).

Chemical Composition of Cells

• Cells consist of a limited number of atom types.
• Atoms are composed of protons, neutrons, and electrons.
• Electrons exist in continuous motion around the nucleus, occupying discrete states in electron shells.

Atomic Interactions and Stability

• Atoms with filled outer shells are stable and chemically inert (e.g., Helium, Neon, Argon).
• Hydrogen is highly reactive due to its half-filled outer shell.

Chemical Bonds

• Ionic Bonds: Formed between oppositely charged ions through electron transfer.
• Covalent Bonds:
  • Atoms share electrons; more stable than ionic bonds.
  • Non-polar Covalent: Electrons shared equally (e.g., CO2).
  • Polar Covalent: Electrons shared unequally, creating polar molecules (e.g., H2O).
  • Hydrogen Bonds: Weak interactions crucial for biological processes, such as water cohesion.

Non-Covalent Interactions

• Help to facilitate molecular interactions within cells, including hydrogen bonds and van der Waals attractions.

Major Organic Molecules

• Four fundamental families of small organic molecules exist in cells:
  • Carbohydrates: Energy source, monomer is monosaccharide (C, H, O in 1:2:1 ratio).
    • Examples: Sugars (glucose, fructose), starch, cellulose.
  • Lipids: Basic unit is fatty acids, important in cell membranes, energy storage.
    • Types include triglycerides (3 fatty acids + 1 glycerol), waxes, and steroids.
    • Provide more energy than carbohydrates (9 cal/g for lipids vs. 4 cal/g for carbs).
  • Proteins: Monomer is amino acid, vital for structure and function in cells.
    • Composed of C, H, O, N (and sometimes S, P). Make up 50% of dry weight.
    • Types include enzymes, structural proteins, contractile proteins, transport proteins, and hormones.
  • Nucleic Acids: Monomer is nucleotide, subunits of DNA and RNA.

Carbohydrates

• Monosaccharides: Simple sugars like glucose (C6H12O6).
• Disaccharides: Composed of two monosaccharides (e.g., sucrose, lactose).
• Polysaccharides: Complex carbohydrates; storage forms include glycogen (in animals) and starch (in plants).

Lipids

• Primarily made of carbon and hydrogen, linked by nonpolar covalent bonds, making them insoluble in water.
• Saturated fats contain only single bonds; usually solid at room temperature.
• Unsaturated fats possess one or more double bonds; typically liquid at room temperature.

Proteins

• Essential for numerous biological functions.
• Each amino acid consists of an amino group, a carboxyl group, and a distinct R group determining its properties.
• Joined by peptide bonds to form polypeptides (proteins).

Protein Structure

• Primary Structure: Sequence of amino acids in a polypeptide.
• Tertiary Structure: Overall three-dimensional shape of the folded polypeptide.