Biochemistry Review - Macromolecules and Enzymes

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.

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.

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.
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.

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.

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

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.

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.

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.