Biochemistry Review - Macromolecules and Enzymes

Exam Announcement Details

• Exam Date: Thursday, 10th
• Time: Midday for 50 minutes reading time (to be confirmed if inclusive or exclusive).
• Format: 40 multiple-choice questions (MCQs)
• Weighting: 25% of final assessment.
• Content Covered: Lecture materials up to the end of week six (not including practical class content).
• Exam Conditions: Closed book, all materials remain in the exam room.
• Room Allocations: Most students will be in the college assembly hall, with overflow into another room (likely at Teachers College). Details will be communicated via Canvas announcements.
• Arrival Instructions: Arrive reasonably early to facilitate entry of large number of students (approx. 180).
• Attendance Check: QR codes will be used as a backup for attendance verification; bring student card to place on the table during the exam.
• Invigilation: There will be multiple invigilators in each room to ensure normal exam conditions.
• Additional Information: Any announcements on Canvas regarding exam details will be updated once confirmed.

Macromolecule Discussion

• Overview of Today’s Topics:
  • Discussion on different macromolecules.
  • Introduction to enzyme catalysis.
• Connection Between Topics:
  • Enzymes are proteins and their function is closely related to their structure, including characteristics such as shape and regulation.

Macromolecule Types

1. Carbohydrates
   • Composition: Comprised of sugars.
   • Roles: Store chemical energy.
     • Glycogen: Key energy store in animals.
     • Starch: Plant equivalent of glycogen; important energy source for animals, especially ruminants.
   • Mucopolysaccharides: Composite molecules (protein + carbohydrate) with roles in lubrication in joints, respiratory tract, gastrointestinal tract, and reproductive tract.
2. Structure of Carbohydrates:
   • Monosaccharides: Simple sugars.
   • Disaccharides: Formed by two monosaccharides (e.g., sucrose, lactose, maltose).
     • Bonds formed are glycosidic bonds.
   • Polysaccharides: Long chains of sugars including glycogen (animals) and starch (plants).
     • Glycogen Structure: Highly branched allowing rapid mobilization of glucose.
     • Starch Structure: Composed of amylose (linear) and amylopectin (branched). Digestion rates of starch affect glycemic index, thus influencing energy release and absorption rates.

Role of Glycogen and Starch

• Glycogen:
  • Stored in liver and muscle.
  • Important for maintaining glucose levels in blood.
  • Serves as an energy source for muscle contraction.
• Comparison of Glycogen and Starch:
  • Glycogen: Highly branched, allowing for rapid energy release. Critical for metabolic homeostasis.
  • Starch: Slower breakdown due to branched structure, affecting energy access in animals.

Other Polysaccharides

• Cellulose: Structural component in plant cell walls (fiber, insoluble).
• Peptidoglycan: Found in bacterial cell walls, combination of carbs/proteins; target for antibiotics.

Enzymes in Catalysis

• Enzyme Overview: Enzymes are proteins that catalyze biochemical reactions (lowering activation energy).
  • They bind substrates (reactants) at active sites, facilitating reactions while remaining unchanged themselves.
• Mechanism of Catalysis:
  • Enzymes create a transient state to lower activation energy needed for the reaction to proceed.
  • Enzymes can change the shape (conformation) of the substrate or alter charge stability to enhance reactivity.
• Factors Affecting Enzyme Activity:
  • Temperature, pressure, pH, substrate concentration, and enzyme concentration influence reaction rates.
  • Specific enzymes influence specific metabolic pathways; understanding their action helps in appreciating metabolic regulation.

Regulation of Enzyme Activity

• Phosphorylation/Dephosphorylation: Rapid processes affecting enzyme activity that take place in seconds, contrasting the slower rate of enzyme production and degradation,
• Enzyme Specificity:
  • Each enzyme has a specific substrate it acts upon due to the specific shape of its active site.

Conclusion on Enzymes

• Enzymes significantly influence biochemical pathways by providing specific routes that substrates can take, thus regulating metabolism effectively.
• Upcoming Topics: Next discussions will focus on enzyme kinetics and dive deeper into metabolic processes.