CHEM 119 & CHEM 119.1

• Cell - The basic unit of life.
• Protoplasm - The living substance inside a cell, surrounded by the cell membrane. And is divided into two parts: the cytoplasm and the nucleus.
• Cytoplasm - Everything inside the cell membrane except the nucleus.
• Nucleus - The part of the cell that controls its functions.
• Types of Cells - Prokaryotic and Eukaryotic
• Prokaryotic Cell:

  • Meaning: "False nucleus."
  • Characteristics:
  • No membrane-bound nucleus.
  • Typically unicellular (single-celled)
• Eukaryotic Cell:

  • Meaning: "True nucleus."
  • Characteristics:
  • Has a membrane-bound nucleus.
  • Usually multicellular (many cells).
• Plasma Membrane

  • Function:
  • Provides shape and strength to the cell.
  • Protects the cell from its environment.
  • Controls what enters and exits the cell, ensuring that essential substances stay in and unwanted substances stay out
• The cell membrane controls what enters and exits the cell through several processes: diffusion, osmosis, dialysis, and surface tension.
• Diffusion - The movement of particles from an area of higher concentration to an area of lower concentration.
• Small molecules and ions move quickly and spread out in a solvent, while larger molecules (macromolecules) move more slowly.
• The rate of diffusion depends on factors such as the size, weight, shape of the molecules, and the concentration gradient.
• Factors Affecting Diffusion

  • External Factors:
  • Viscosity: In less viscous liquids, diffusion is faster (e.g., water at high temperature). In more viscous liquids, diffusion slows down (e.g., cooking oil at low temperature).
  • Temperature: Higher temperatures increase the movement of particles, enhancing diffusion.
• Osmosis - The movement of water (the solvent) across a semi-permeable membrane from a region with fewer osmotically active particles to a region with more.
• Cell Membranes are made up of phospholipid bilayers, proteins, carbohydrates, and cholesterol.
• Concentration Gradient: Water moves from a solution with low solute concentration (fewer particles) to one with high solute concentration (more particles).

  Example: Salt moves from an area of lower concentration to an area of higher concentration.
• Osmotic Concentration: This measures the number of osmotically active particles in a solution per unit volume, which helps characterize its osmotic properties.
• Movement of Water:

  • Water will flow from a solution with lower osmotic pressure (fewer particles) to one with higher osmotic pressure (more particles) when separated by a semi-permeable membrane.
• Hypertonic Solution: If the surrounding solution has a higher osmotic pressure than the cell, the cell will lose water and shrink.
• Hypotonic Solution: If the surrounding solution has a lower osmotic pressure than the cell, the cell will gain water, swell, and possibly burst.
• Dialysis - The diffusion of solute molecules across a differentially permeable membrane.
• Function: Dialysis acts like the semi-permeable membranes found in the body, such as in the kidneys (specifically in the nephron, which filters blood).
• • Permeability: The ability of the membrane determines which particles can pass through.
  • Small solute molecules can often move through the membrane.
  • Larger molecules are typically retained.
• Types of Permeability:

  • Impermeable: No particles can pass through.
  • Semi-permeable: Only certain particles can leave.
  • Permeable: Both types of particles can pass through freely.
• Surface Tension

  • Definition: Surface tension is the tendency of liquid surfaces to contract and behave like a stretched membrane due to strong intramolecular forces.
• Intramolecular Forces: Strong intermolecular forces (IMFs) lead to higher surface tension. The stronger the IMFs, the greater the surface tension.

  • Example: In a mixture of water and oil, soap acts as an emulsifier. It helps mix the two liquids by reducing their surface tension and preventing separation.
• Behavior of Surface Molecules:

  • Molecules at the surface of a liquid experience unbalanced attractions, pulling them inward. This inward pull causes surface molecules to come closer together, contributing to the liquid's overall surface tension.
• Interaction of Miscible Liquids:

  • When two partially miscible liquids come into contact, they can dissolve in each other to some extent, which can significantly alter their surface tension.
• Types of Permeability:

  • Impermeable: No particles can pass through.
  • Semi-permeable: Only certain particles can leave.
  • Permeable: Both types of particles can pass through freely.
• Importance of Water

  • Composition: Water makes up about 70% of the human body and many other animals, serving as a vital component for life.
  • Medium for Reactions: Most biochemical reactions occur in water, making it essential for metabolism and cellular processes.
• pH Levels: The acidity (low pH) or alkalinity (high pH) of a solution significantly affects biological processes. This is measured by the concentration of hydrogen ions (H⁺) in the solution.
• Regulation: Our bodies need to maintain a stable pH level, as even slight changes can disrupt important biological functions.
• Buffers are solutions that resist changes in pH when small amounts of acid or base are added.
• Components: They typically consist of a weak acid and its conjugate base (or a weak base and its salt). For example, a mixture of carbonic acid (H₂CO₃) and bicarbonate (HCO₃⁻) is a common buffer in the body.
• Carbonate Buffer System: This is one of the key buffering systems in the human body, helping to maintain pH balance. It regulates pH by neutralizing excess acids or bases.

  
  

  Function: When an acid is introduced, the weak base in the buffer can react with it, minimizing changes in pH. Similarly, if a base is added, the weak acid component can neutralize it.
• High pH: A significant increase in pH (alkalinity) can lead to the destruction of molecules and can disrupt cellular function.
• Homeostasis: Buffers play a crucial role in maintaining pH homeostasis, allowing biological processes to function optimally.
• Example of a Base

  • Sodium Hydroxide (NaOH): This is a strong base that can dramatically change pH if added to a solution. Buffers prevent such drastic changes by neutralizing small amounts of NaOH or other acids/bases.
• A conjugate base is what remains after an acid donates a proton (H⁺). Essentially, when a weak acid loses a hydrogen ion, it forms its conjugate base.
• Buffer Composition: A buffer typically consists of a weak acid and its conjugate base (or a weak base and its conjugate acid).