Introduction to Biology Assignments Sample

Introduction to Biology Assignments Sample

Metabolism

• Biochemical reactions that occur in a cell to sustain life are cohesively referred to as ‘metabolism’ (Judge and Dodd, 2020).
• There are two main processes which compose it Catabolism and Anabolism.
• Catabolism – The process of breaking down complex molecules into simpler ones and getting the energy (Stork, Friedl and Cena, 2020).
• Examples of catabolic reactions include- Protein Digestion and Glycolysis
• Anabolism – Synthesis of complex molecules from simpler ones requiring energy.
• Examples of anabolic reactions include Protein synthesis and DNA replication

This Biology Assignments Sample explains metabolism, the biochemical reactions that sustain life, focusing on catabolism and anabolism. An Assignment writing helper can help students understand energy production, protein digestion, glycolysis, protein synthesis, and DNA replication.

Speaker Notes:

The sum of all chemical reactions that take place in a cell that keep the cell alive is called metabolism. Catabolism is the breakdown of large molecules into smaller ones and the release of energy, and anabolism is the building of complex molecules from simpler ones with the use of energy.

The image shows the left side as being catabolism. In this case, there is a breaking down of a large molecule into smaller subunits that release energy. Examples of catabolic reactions include- Protein Digestion and Glycolysis. The breakdown of proteins into amino acids by proteases is known as Protein Digestion. The breakdown of glucose into pyruvate and the release of ATP is referred to as glycolysis.

On the right side, anabolism involves smaller molecules combining to form a greater, more complicated structure that takes energy. Examples of anabolic reactions include-

Protein synthesis – The formation of proteins from amino acids.

DNA replication – The synthesis of new DNA strands from nucleotides.

Adenosine Triphosphate (ATP)

• ATP has an adenine base, ribose sugar and three phosphate groups.
• By breaking the bond of the second and third phosphate groups, ATP releases energy through hydrolysis to form ADP + Pi (Dunn and Grider, 2023).
• ATP synthesis which is an endothermic reaction, stores energy.
• ATP is an important procedure in Muscle Contraction (LibreTexts, 2024)

Speaker Note:

Adenosine triphosphate is composed of adenine, ribose, and three groups of phosphate. Hydrolysis of ATP releases energy. For instance, ATP is generated by glycolysis and oxidative phosphorylation from glucose in skeletal muscle cells. Cellular respiration allows ATP to be regenerated from ADP to make sure there is no power source for movement. This is where ATP binds to myosin, making it bind to contract. Energy for muscle relaxation and ion transport required for sustained function is obtained from ATP hydrolysis. It is an important process for skeletal muscle function.

Energy Pathway

Information on Detailed ATP Production

• In glycolysis, a net of 2 molecules of ATP is produced per molecule of glucose.
• Within the Krebs Cycle, a total of 1 ATP is produced per pyruvate molecule. Due to two pyruvate molecules being produced by each glucose molecule, the Krebs Cycle results in 2 ATP per glucose.
• The Electron Transport Chain produces about 32-34 molecules of ATP per molecule of glucose, and this is the point where most ATP is produced.
• The full amount of ATP made in aerobic respiration, by adding the products of glycolysis, the Krebs Cycle and the Electron Transport Chain, is about 36 to 38 ATP per molecule of glucose.
• During anaerobic respiration, only two ATP molecules are formed from a single glucose molecule. The reason behind this is that anaerobic respiration does not need the Krebs Cycle or the Electron Transport Chain because their functioning depends on the presence of oxygen.

The Reason Aerobic Respiration Has a Greater Production of ATP

During aerobic respiration, the final electron acceptor in the Electron Transport Chain is oxygen, and this enables complete oxidation of glucose with high yield of ATP.

Anaerobic respiration, on the other hand does not require oxygen. This lack of oxygen causes the Electron Transport Chain to cease its functional purpose, which restricts the production of ATP to glycolysis only, and produces a much reduced yield of ATP.

EPOC

• EPOC is the excess oxygen ‘burnt’ after exercise to come back to the same resting state (Cleveland Clinic, 2023).
• Factors contributing to EPOC:
• Replenishment of ATP and phosphocreatine stores.
• Removal of lactic acid by the Cori cycle.
• Differences between light and heavy exercise:
• Recovery of greater oxygen consumption.
• In heavy exercise, heat production increases, demand for oxygen for thermoregulation remains prolonged.

Speaker Note:

EPOC is the excess oxygen consumed after exercise to return the body to its resting state. In high intensity activity, the oxygen demand is greater than their supply resulting in an oxygen debt which has to be repaid after exercise.

Factors contributing to EPOC are-

• Oxygen was used to restore body ATP and phosphorylated creatine that were depleted during exercise.
• The Cori cycle also converts the accumulated lactic acid back into pyruvate or glucose in the liver by using oxygen.

Difference between EPOC in light and heavy exercise-

• To recover from heavy exercise more oxygen is consumed, thus more ATP will be needed.
• Heavy exercise prolongs oxygen demand for thermoregulation due to increased heat production.

Overall, restoring homeostasis and energy balance is what EPOC supports in terms of recovery.

ENZYMES: Activation energy

• Activation energy is lowered to speed up reactions by enzymes.
• They display substrate specificities and convert specific substrates to products.
• The activity of enzymesenzymes is affected by factors such as temperature, pH and substrate concentration (Koshland and Haurowitz, 2024).

Speaker note:

In the metabolic process, enzymes are biological catalysts that lower activation energy and make chemical reactions faster. This raises the reaction rate at which essential biochemical processes can take place efficiently. Specific substrates are bound to enzymes, which convert them to products without consumption by the enzymes. All these factors affect their activity and they even depend on temperature, pH and substrate concentration. Enzymes speed up and make reactions most efficient to achieve the best possible outcome including good digestion, cellular repair and energy.

ENZYMES: mechanism of action:

• The enzymes are biological catalysts, made of proteins.
• Lock and key hypothesis

This model suggests a fixed shape of the enzyme’s active site, that fits the substrate perfectly, as it were a key fitting into a lock (Biology Online, 2020).

• Induced Fit Hypothesis

The active site shape is slightly adjusted to accommodate the substrate to improve the binding efficiency and the reaction (Karki, 2023).

Speaker Note:

Proteins with an active site that binds to a substrate and transform it into products are called enzymes. The lock and key hypothesis claims that the substrate fits perfectly in the enzyme’s active site like a key in a lock. Instead of induced fit hypothesis says that the enzyme slightly changes the shape to accept the substrate and make it bind more efficiently. Both models explain enzyme specificity, however, the induced fit model takes into regard flexibility which increases catalytic activity.

Variables influencing enzyme activity: temperature:

Temperature ()	Reaction Rate (Units/Min)	Observation
20	5 (Low)	Enzyme activity increases but remains slow.
37	15 (High)	Maximum enzyme activityThe best temperature for function.
50	4 (Moderate)	As it is partially denatured, the enzyme begins to lose efficiency.

Speaker note:

In the mock experiment, it was revealed that enzyme activity is highly dependent on temperature. At a temperature of 20 °C, the rate of this reaction was found to be 5 units/minute, which implies that the reaction was slower due to the slower movement of molecules since there were fewer enzyme-substrate collisions. The reaction rate at an optimal temperature of 37 °C was 15 units per minute, indicating the maximum activity as the kinetic energy at this temperature is optimal, so that the collisions between the molecules are maximum. Nonetheless, at 50 °C, the rate of the reaction rapidly declined to 4 units per minute. This is due to the fact that the enzyme started to denature, and it lost its functional three-dimensional structure, thus decreasing its capacity to bind substrates efficiently. As the data indicates, we can observe that optimal activity of the enzyme has been reached at the optimal temperature, and the enzyme activity was much lower at both lower and higher temperatures. Such outcomes verify that temperature is a very essential factor that determines the effectiveness of enzymes and that enzyme reactions are sensitive to temperature.

Variables influencing enzyme activity: pH

• The best pH conditions for enzymes make sure they are in the right shape to bind substrates and make the reaction go fast.
• Optimal pH inactivates the enzyme through deviation of charge distribution, resulting in loss of enzyme-substrate interactions (Kaiser, 2022).
• Reaction rates are slowed by extreme pH levels as extreme pH disrupts the efficiency of the enzyme and the binding of substrates (Clark and Harvey, 2025).

Speaker Notes:

Optimal pH is the pH at which enzymes work best, it is the pH that enzyme is most compatible with substrate. Enzyme substrate interactions are weakened due to changes in pH which change the charge distribution. The reaction efficiency decreases as pH moves further from optimal. An enzyme will have a slower rate of product formation and lower enzyme performance.

Variables influencing enzyme activity: Non-competitive inhibitors

• Non-competitive inhibitors bind to an enzyme away from the site where the active site is, changing the shape of the enzyme (Delaune and Alsayouri, 2022).
• It improves enzyme efficiency, but thereby also reduces reaction rate regardless of substrate concentration.
• Arsenic is a potent poison because it inhibits essential enzymes, thereby disrupting metabolism, and blocking cellular function.

Speaker Notes:

At a separate site, non-competitive inhibitors attach themselves to an enzyme so that the structure of the enzyme is changed and substrates cannot bind effectively. The reaction rate is lowered, and more substrate cannot reverse this. It is the poisoning due to arsenic that blocks important enzymes that enable energy production and the result is cell dysfunction and severe toxicity.

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References

• Biology Online (2020). Lock-and-key model Definition and Examples - Biology Online Dictionary. [online] Biology Articles, Tutorials & Dictionary Online. Available at: https://www.biologyonline.com/dictionary/lock-and-key-model [Accessed 15 Mar. 2025].
• Clark, J. and Harvey, D. (2025). The Effect of pH on Enzyme Kinetics. [online] Chemistry LibreTexts. Available at: https://chem.libretexts.org/Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Map%3A_Physical_Chemistry_for_the_Biosciences_(Chang)/10%3A_Enzyme_Kinetics/10.07%3A_The_Effect_of_pH_on_Enzyme_Kinetics [Accessed 15 Mar. 2025].
• Cleveland Clinic (2023). How To Calculate EPOC (and Why It Matters). [online] Cleveland Clinic. Available at: https://health.clevelandclinic.org/understanding-epoc.
• Delaune, K.P. and Alsayouri, K. (2022). Physiology, Noncompetitive Inhibitor. [online] Nih.gov. Available at: https://www.ncbi.nlm.nih.gov/books/NBK545242/.
• Dunn, J. and Grider, M.H. (2023). Physiology, Adenosine Triphosphate. [online] PubMed. Available at: https://www.ncbi.nlm.nih.gov/books/NBK553175/.
• Judge, A. and Dodd, Michael S. (2020). Metabolism. Essays in Biochemistry, 64(4), pp.607–647. doi:https://doi.org/10.1042/ebc20190041.
• Kaiser, G. (2022). Factors Affecting Enzyme Activity. [online] Biology LibreTexts. Available at: https://bio.libretexts.org/Courses/Prince_Georges_Community_College/PGCC_Microbiology/07%3A_Microbial_Metabolism/7.01%3A_Introduction_to_Metabolism_and_Enzymes/7.1.01%3A_Factors_Affecting_Enzyme_Activity.
• Karki, P. (2023). Induced Fit Model- Definition, Mechanism, Advantages. [online] microbenotes.com. Available at: https://microbenotes.com/induced-fit-model-definition-mechanism-advantages/.
• Koshland, D.E. and Haurowitz, F. (2024). Protein - Role of enzymes in metabolism. In: Encyclopædia Britannica. [online] Available at: https://www.britannica.com/science/protein/Role-of-enzymes-in-metabolism.
• LibreTexts (2024). 38.17: Muscle Contraction and Locomotion - ATP and Muscle Contraction. [online] Biology LibreTexts. Available at: https://bio.libretexts.org/Bookshelves/Introductory_and_General_Biology/General_Biology_(Boundless)/38%3A_The_Musculoskeletal_System/38.17%3A_Muscle_Contraction_and_Locomotion_-_ATP_and_Muscle_Contraction [Accessed 15 Mar. 2025].
• Stork, B., Friedl, E. and Cena, C. (2020). Anabolism and Catabolism: Definitions & Examples - Video & Lesson Transcript | Study.com. [online] Study.com. Available at: https://study.com/academy/lesson/anabolism-and-catabolism-reactions-definitions-examples.html [Accessed 15 Mar. 2025].