Biology Chapter: Enzyme Activity and Diffusion

Enzyme Activity and Temperature

• Enzymes function optimally at a specific temperature.
• For the human body, this optimum is 37°C.
• High temperatures disrupt the bonds holding the enzyme together, causing it to lose its shape (denaturation).
• Lower temperatures decrease the kinetic energy of enzymes and substrates, leading to fewer collisions, reduced activity, and fewer products.
• Enzyme activity increases with rising temperature until the optimum is reached, then decreases beyond it due to denaturation.

Diffusion

• Diffusion is the movement of particles from high to low concentration due to random motion.
• Substances move into and out of cells via diffusion through the cell membrane.
• Gaseous Exchange in Lungs: Oxygen diffuses from the alveoli (lungs) into red blood cells.
• Gaseous Exchange in Plants: Carbon dioxide diffuses into leaves for photosynthesis, and oxygen diffuses out.
• Factors Affecting Diffusion:
  • Larger surface area increases diffusion rate. (e.g., alveoli, root hair cells)
  • Higher temperatures speed up particle movement and diffusion.
  • A steeper concentration gradient leads to faster diffusion.

Active Transport

• Active transport moves particles against their concentration gradient (low to high).
• This process requires energy from respiration.
• Crucial for transporting molecules and ions across membranes.
• Example: Ion uptake by root hair cells (plant roots absorb ions from low-concentration soil).

Biological Molecules

• Carbohydrates: Carbon, Hydrogen, Oxygen (CHO)
• Proteins: Carbon, Hydrogen, Oxygen, Nitrogen, Sulfur (CHONS)
• Fats: Carbon, Hydrogen, Oxygen (CHO)
• Large molecules (polymers) are built from smaller molecules (monomers).
  • Starch and glycogen are made of glucose.
  • Proteins are made of amino acids.
  • Fats are made of fatty acids and glycerol.
• Examples of Polymers and Monomers:
  • Starch (glucose — plants, storage)
  • Glycogen (glucose — animals, storage in liver & muscles)
  • Cellulose (glucose — plant cell walls, structural)
  • Proteins (amino acids — muscle, hair, cell membranes, enzymes like insulin)
  • Fats (fatty acids & glycerol — cell membranes, hormone storage, long-term energy)

Biochemical Tests

• Iodine Test for Starch: Orange/yellow → Blue/black (positive)
• Benedict's Test for Glucose: Blue → Brick red (positive)
• Biuret Test for Proteins: Blue → Purple (positive)
• Ethanol Test for Lipids: Colorless → Cloudy (positive)

Osmosis

• Osmosis is the movement of water through a partially permeable membrane from high water potential (dilute solution) to low water potential (concentrated solution).
• Effect on Plant Cells:
  • Pure water → Water enters, becomes turgid.
  • Same concentration → No net movement, flaccid.
  • Concentrated solution → Water leaves, becomes plasmolysed.
• Effect on Animal Cells:
  • Pure water → Water enters, becomes lysed (bursts).
  • Same concentration → No net movement, normal.
  • Concentrated solution → Water leaves, becomes crenated (shrinks).
• Key terms: turgid, flaccid, plasmolysed, osmosis

This quiz covers key concepts related to enzyme activity and diffusion processes in biological systems. Learn how temperature affects enzyme functionality and explore the mechanisms of diffusion in cells, including gas exchange in lungs and plants. Test your understanding of these fundamental biological principles.