Term 1 Accelerated Biology Assessment Task

Identify the role of enzymes in cellular processes.

"Enzymes act as biological catalysts that speed up chemical reactions without being consumed, allowing cells to efficiently regulate metabolic activities."

Define activation energy and explain its significance in cellular reactions.

"Activation energy is the minimum amount of energy required for a chemical reaction to occur. Enzymes lower this energy, allowing reactions to proceed efficiently at body temperature."

Describe how enzyme specificity ensures precise cellular function.

Enzyme specificity occurs because each enzyme has an active site that only fits a specific substrate, forming an enzyme-substrate complex. This ensures that only necessary reactions occur, maintaining cellular efficiency."

Explain how enzymes coordinate cellular activities by regulating reaction rates.

Enzymes speed up reactions by lowering activation energy, allowing essential biochemical processes like respiration, digestion, and DNA replication to occur efficiently. Without enzymes, these reactions would be too slow to sustain life."

Compare the lock-and-key model and the induced fit model of enzyme action.

In the lock-and-key model, the enzyme's active site has a rigid shape that perfectly fits the substrate. In contrast, the induced fit model suggests that the enzyme’s active site is flexible and adjusts to fit the substrate more precisely. The induced fit model is now considered more accurate."

Analyse how enzyme activity is influenced by internal and external factors.

"Enzyme activity is regulated by internal factors like pH, temperature, and substrate concentration. External signals, such as hormones, can also regulate enzyme production. When conditions deviate from optimal ranges, enzymes may denature, affecting cellular processes and homeostasis."

Assess the importance of enzymes in maintaining cellular homeostasis.

Enzymes maintain homeostasis by regulating metabolic pathways to balance energy production, waste removal, and biosynthesis. Without enzymes, essential reactions would be too slow, leading to cellular dysfunction and organismal imbalance. Their specificity and ability to function under controlled conditions make them indispensable for life."

Evaluate the role of enzyme-substrate interactions in ensuring efficient biochemical pathways.

Enzyme-substrate interactions optimize reaction rates by reducing activation energy and ensuring specificity. The induced fit model increases reaction efficiency by adapting the active site to substrates. While enzymes allow precise metabolic control, they are sensitive to environmental changes, requiring regulatory mechanisms to maintain function."

Identify one way cells communicate with their external environment.

"Cells communicate through signal molecules (e.g., hormones, neurotransmitters), which bind to receptor proteins on the membrane to trigger a response."

Define homeostasis and its importance for cellular function.

Homeostasis is the process of maintaining a stable internal environment despite external changes. It ensures optimal enzyme activity, nutrient availability, and waste removal for cellular function."

Describe how cell membranes contribute to internal coordination.

✅ "The plasma membrane regulates movement of molecules via passive and active transport, ensuring nutrient uptake, waste removal, and communication through embedded receptor proteins."

Describe the effect of enzyme inhibitors on cellular function.

✅ "Enzyme inhibitors slow or stop reactions by blocking the active site (competitive inhibition) or altering enzyme shape (non-competitive inhibition), reducing metabolic efficiency."

Explain how feedback mechanisms regulate enzyme activity.

✅ "Feedback mechanisms control enzyme function by inhibiting or activating enzymes in response to internal conditions. For example, in negative feedback, excess product binds to an enzyme, reducing further production and maintaining balance."

Compare passive and active transport in maintaining cellular function.

✅ "Passive transport (diffusion, osmosis, facilitated diffusion) moves molecules down a concentration gradient without ATP, while active transport requires ATP to move substances against the gradient, ensuring essential nutrients enter the cell and waste is expelled."

Analyse the role of ATP in cellular coordination.

✅ "ATP provides immediate energy for cellular processes such as active transport, enzyme function, and cell signaling. Without ATP, essential metabolic activities would cease, disrupting homeostasis and cellular communication."

Analyse how changes in pH affect enzyme activity and metabolic efficiency.

✅ "Enzymes function best at an optimal pH, where their active site maintains the correct shape. A pH imbalance alters enzyme structure (denaturation), reducing reaction rates and disrupting cellular function."

Assess the importance of signal transduction pathways in cellular coordination.

"Signal transduction allows cells to respond to external signals by activating intracellular pathways. This ensures coordinated responses, such as hormone regulation (e.g., insulin) or immune activation. Without this process, cells would fail to adapt to environmental changes, affecting homeostasis."

Evaluate the role of transport proteins in maintaining cellular homeostasis.

"Transport proteins facilitate the movement of molecules across membranes, ensuring the correct balance of ions, nutrients, and waste. While highly efficient, these proteins can be affected by mutations or inhibitors, disrupting homeostasis and leading to diseases such as cystic fibrosis."

Identify the role of catalase in cellular function.

"Catalase is an enzyme that breaks down hydrogen peroxide (H₂O₂) into water and oxygen, preventing cellular damage from toxic by-products of respiration."

Define an enzyme and explain how catalase functions as one

An enzyme is a biological catalyst that speeds up chemical reactions without being consumed. Catalase functions by lowering the activation energy required to break down hydrogen peroxide into non-toxic water and oxygen

Describe how cells use catalase to coordinate internal homeostasis.

✅ "Cells continuously produce hydrogen peroxide as a by-product of metabolism. To prevent damage, catalase rapidly breaks it down, maintaining a stable internal environment and preventing oxidative stress."

Describe the experimental method for testing catalase activity at different pH levels.

✅ "Catalase is extracted from plant cells (e.g., spinach), mixed with hydrogen peroxide, and exposed to different pH conditions. The rate of reaction is measured by observing the height of oxygen bubbles formed."

Explain how pH affects catalase activity and enzyme function.

✅ "Catalase functions best at an optimal pH of around 7, similar to cytoplasmic pH (7.2). Deviations from this pH alter enzyme structure, reducing reaction efficiency and affecting cellular detoxification processes."

Explain how the breakdown of hydrogen peroxide by catalase helps cells respond to external environmental changes.

✅ "Hydrogen peroxide levels fluctuate based on metabolic activity. Catalase allows cells to rapidly break down excess peroxide, preventing oxidative damage and enabling adaptive responses to changing metabolic demands."

Compare the efficiency of measuring catalase activity in a school experiment vs. university-level research.

"In schools, catalase activity is measured using the height of bubbles in a test tube. At the university level, an oxygen probe quantifies oxygen concentration changes digitally. While the school method provides a rough estimate, the university approach increases accuracy and reliability."

Analyse how catalase enzyme activity ensures coordination between metabolic pathways.

"Catalase activity prevents toxic hydrogen peroxide accumulation, ensuring continuous cellular respiration. This regulation allows metabolic pathways such as glycolysis and oxidative phosphorylation to function without disruption, maintaining energy production and homeostasis."

Assess the importance of catalase in protecting cellular structures.

"Catalase prevents oxidative stress by neutralizing hydrogen peroxide, protecting vital cellular components like DNA, proteins, and membrane lipids. Without catalase, cells would suffer damage, leading to apoptosis or impaired function, demonstrating its essential role in maintaining cellular integrity."

Evaluate the effectiveness of enzyme regulation in coordinating internal cellular activities.

"Enzymes like catalase regulate metabolic reactions efficiently by adjusting to cellular conditions. While effective under normal physiological conditions, extreme environmental changes (e.g., altered pH or temperature) can denature enzymes, compromising metabolic control. Therefore, enzyme regulation is crucial but also dependent on external stability."

Justify why catalase activity must be tightly regulated in aerobic organisms.

✅ "Aerobic organisms continuously generate hydrogen peroxide as a by-product of respiration. Since H₂O₂ is highly reactive and can cause cellular damage, catalase must be tightly regulated to maintain detoxification efficiency while avoiding unnecessary energy expenditure on excess enzyme production."

Define the catalase equation for hydrogen peroxide

✅ "The catalase equation represents the breakdown of hydrogen peroxide (H₂O₂) into water (H₂O) and oxygen (O₂) using the enzyme catalase. The balanced chemical equation is:"

✅ "This reaction prevents the accumulation of toxic hydrogen peroxide, protecting cells from oxidative damage."

What are the things that you have to focus on in order to answer for reliability?

• Have I done multiple trials? 

• Have I found an average to eliminate random errors?

• Have I obtained consistent results across multiple trials?

What are the things that you have to focus on in order to answer with accuracy?

• Do the results of the investigation agree with the scientifically accepted value?

• Have I used the best available measuring equipment?

• Does the method of measurement minimize random errors?

What are the things that you have to focus on in order to answer with validity?

• Does my experiment measure the variable of interest?

• Does it actually test the hypothesis that I want it to?

• Have all variables apart from those being tested been kept constant?

• Have errors been kept to a minimum?

• Are all of my results accurate and reliable?

What is an enzyme?

An enzyme is a biological catalyst that speeds up the reaction rates within the body.

What does the diagram show?

The diagram demonstrates how the enzyme denatures after performing its catalytic role as heat and the pH level alters. This change results in the enzyme's active site changing and therefore unable to function anymore for that substrate.

How do changes to enzyme shape affect function?

Primarily, it changes the physical shape and the active site of the enzyme and means that it is unable to function anymore for that substrate

Identify the substrate that the enzyme catalase works on.

Hydrogen Peroxide

Explain why catalase is an important enzyme for most living organisms.

Catalyse is vital as hydrogen peroxide is toxic to the body, however, it is a byproduct of cellular respiration necessary for most living organisms to survive. Therefore, the catalase enzyme splits the hydrogen peroxide into oxygen and water, which is essential for the organism to function, and without the catalase enzyme, the body will build up the toxic material and die quickly.

At which pH will catalase work optimally at? Why?

• The catalase works optimally at a pH level of 7

• as the active site of the enzyme is built to function efficiently when the pH level is neutral

• when it gets too acidic or alkaline, it can disrupt the enzyme’s activity and negatively affect the body by increasing the levels of hydrogen peroxide in the body

• As a result, the organism dies of waste build-up.

What makes an experiment reliable?

An experiment is reliable when it consistently produces similar results under the same conditions.

Why would an experiment be reliable?

• The experiment is reliable as it produced consistent results over 3 trials under similar conditions

• included an average within the results to ensure that outliers are eliminated.

Suggest how the reliability of an experiment could be improved.

The reliability of the experiment can be improved by including more trials within, to ensure absolute or precise results.

What makes an experiment valid?

• The experiment is valid if it includes accurate control of variables,

• ensures that it addresses the aim of the experiment by relating to the method

• minimises errors during the experiment.

• For the experiment to be valid, it must be accurate and reliable.

Define an extraneous variable.

•  any factor other than the independent variable that can potentially influence the dependent variable -> leading to inaccurate conclusions, and the relationship between the variables

Identify three factors that affect enzyme activity.

• The three factors affecting enzyme activity are temperature, pH, and substrate concentration

• Each of these influences enzyme efficiency and reaction rates by altering molecular interactions and enzyme stability.

Define 'denaturation' in the context of enzyme activity.

• Denaturation is the irreversible structural change of an enzyme

• due to extreme temperature or pH

• causing the active site to lose its shape and preventing substrate binding

• leading to loss of function."

Describe how temperature influences enzyme activity.

• As temperature increases, enzyme activity rises due to higher kinetic energy

  → leading to more frequent enzyme-substrate collisions

• However, beyond the enzyme’s optimum temperature, excessive heat disrupts hydrogen bonds

  → denaturing the enzyme and reducing activity

Explain the effect of substrate concentration on enzyme activity.

• At low substrate concentrations, there are fewer molecules available to bind to enzymes, so reaction rates are slow.

• As more substrate is added, enzyme activity increases because more active sites are occupied.

• However, at a certain point, all enzymes are working at full capacity, meaning adding more substrate won’t speed up the reaction further."

Compare the effects of pH and temperature on enzyme activity.

• Both pH and temperature affect enzyme activity by altering the shape of the active site.

• Temperature changes affect how fast molecules move, while extreme heat denatures enzymes.

• pH changes affect chemical interactions within the enzyme, altering how well it binds to its substrate.

• Enzymes function best within a narrow pH and temperature range, specific to their environment."

Analyse the relationship between enzyme structure and its shape

• Enzymes have a specific 3D shape, especially in their active site, which fits only one type of substrate—like a lock and key.

• Performing either an anabolic or catabolic reaction

• This ensures enzymes only catalyze one type of reaction, preventing unwanted chemical changes.

• If the enzyme's shape is altered (e.g., by pH or temperature changes), it loses its specificity and won’t function properly."

Assess the importance of enzymes in metabolic reactions.

• Enzymes are essential for metabolism because they speed up reactions that would otherwise be too slow to sustain life.

• For example, digestion relies on enzymes to break down food into nutrients, while respiration depends on enzymes to release energy (ATP).

• Without enzymes, cells couldn’t function efficiently, leading to a failure in homeostasis.

Evaluate the impact of enzyme inhibition on metabolic pathways.

• Enzyme inhibition is important for controlling reaction rates in metabolic pathways.

• Competitive inhibitors temporarily block the active site, slowing down reactions, while non-competitive inhibitors change the enzyme’s shape, permanently reducing function.

• While inhibition helps regulate metabolism, excessive inhibition can cause diseases or metabolic disorders, proving that enzyme activity must be carefully balanced for homeostasis

Describe the graph for temperature and its effect on enzyme activity.

• The graph for temperature shows a bell-shaped curve.

• At low temperatures, enzyme activity is slow because molecules have low kinetic energy and fewer collisions occur.

• As temperature increases, enzyme activity rises until it reaches the optimum temperature, where reaction rates are highest.

• Beyond this point, excessive heat denatures the enzyme, causing a rapid drop in activity as the active site loses its shape and can no longer bind to substrates.

Describe the graph for pH and its effect on enzyme activity.

• The graph for pH also forms a bell-shaped curve.

• Enzymes work best at their optimum pH, where the active site is correctly shaped for substrate binding.

• Moving away from this pH (too acidic or too alkaline) disrupts chemical bonds, altering the enzyme’s shape and reducing activity.

• Extreme pH levels cause denaturation, leading to a sharp decline in reaction rate."

Describe the graph for substrate concentration and its effect on enzyme activity.

• The graph for substrate concentration shows a rapid increase in enzyme activity at low substrate levels, as more molecules collide with enzymes.

• However, as substrate concentration continues increasing, the graph levels off (plateaus) when all enzyme active sites are occupied.

• At this point, adding more substrate does not increase reaction rate because enzymes are already working at maximum capacity (Vmax)."

Compare the effects of pH and substrate concentration on enzyme activity.

• Both pH and substrate concentration influence enzyme activity by affecting reaction rates.

• Enzymes function best at an optimal pH, where their active site maintains its correct shape.

• Any deviation from this pH alters the enzyme's chemical interactions, reducing its ability to bind with substrates, and extreme pH changes can cause denaturation, making the enzyme permanently non-functional.

• In contrast, substrate concentration affects the frequency of enzyme-substrate collisions.

• At low substrate levels, enzyme activity is slow due to insufficient interactions.

• As substrate concentration increases, enzyme activity rises until all active sites are occupied (Vmax), at which point further increases in substrate do not enhance reaction rates.

• While both factors impact enzyme efficiency, pH primarily affects enzyme structure, while substrate concentration controls reaction speed.

• Cells regulate both to ensure optimal enzyme function and maintain homeostasis.

Compare the effects of temperature and substrate concentration on enzyme activity

• Both temperature and substrate concentration influence enzyme activity by determining reaction rates.

• Temperature affects the kinetic energy of molecules, increasing enzyme-substrate collisions at moderate heat levels.

• However, excessive heat denatures enzymes, altering the active site and preventing substrate binding.

• In contrast, substrate concentration does not alter enzyme shape but determines how frequently enzymes interact with substrates.

• At low temperatures, enzyme activity slows as molecules move less, reducing reaction frequency.

• Similarly, low substrate concentrations limit reaction rates due to fewer available molecules binding to enzymes.

• Increasing substrate levels initially enhances enzyme activity, but once all active sites are occupied (Vmax), the reaction rate plateaus.

• While both factors influence reaction speed, temperature directly affects enzyme structure, whereas substrate concentration only influences reaction rates up to a saturation point.

• Cells regulate these conditions to maintain efficient enzyme activity and prevent metabolic disruption.

Identify (1–2 marks)

Definition: Recognize and name.
✅ Template:
"[Concept] is [definition]. For example, [example]."

Define (1–2 marks)

Definition: State the precise meaning of a term.
✅ Template:
"[Term] is defined as [concise explanation]."

🔹 Example Question: Define transcription.
✅ Full-Mark Answer:
"Transcription is the process where DNA is used as a template to synthesize messenger RNA (mRNA) in the nucleus."

Describe (2–4 marks)

Definition: Provide characteristics or features → occuring in a location → provide purpose
✅ Template:
"[Concept] involves [key feature 1] and [key feature 2]. This process occurs in [location] and functions to [purpose]."

Explain (3–6 marks)

Definition: Relate cause and effect, why or how something happens.
✅ Template:
"[Concept] occurs because [cause]. This leads to [effect], which results in [outcome]."

Compare (4–6 marks)

Definition: Identify similarities and differences.
✅ Template:
"Both [concept 1] and [concept 2] share [similarity 1] and [similarity 2]. However, [concept 1] differs in that it [difference 1], while [concept 2] [difference 2]."

Analyse (6–8 marks)

Definition: Break down a concept into its components and examine relationships.
✅ Template:
"[Concept] consists of [component 1], [component 2], and [component 3]. The relationship between these is [analysis of how they interact]. This results in [final effect or conclusion]."

Evaluate (6–9 marks)

Definition: Make a judgment based on criteria.
✅ Template:
"The effectiveness of [concept] can be assessed based on [criterion 1] and [criterion 2]. While [advantage 1] supports its use, [limitation 1] presents a challenge. Overall, [final judgment based on evidence]."

Justify (5–8 marks)

Definition: Provide reasons for a choice or decision.
✅ Template:
"[Choice] is the most appropriate because [reason 1] and [reason 2]. Evidence supporting this includes [example or scientific explanation]."

Assess (6–9 marks)

Definition: Make a judgment by weighing evidence.
✅ Template:
"The significance of [concept] can be assessed by considering [factor 1] and [factor 2]. While [positive aspect] demonstrates its effectiveness, [limitation] suggests improvements are needed. Based on the evidence, [final judgment]."

🔹 How to Score Full Marks in Prelim Biology

✔ Use precise scientific terminology
✔ Structure responses logically (PEEL: Point, Explain, Example, Link)
✔ Address all parts of the question
✔ Use examples or experimental evidence when relevant
✔ Write concisely while covering depth

"Discuss" (6–9 marks)

Key Elements of a Full-Mark Response:
✔ Introduction – Define the concept and state the main ideas you'll discuss.
✔ Arguments For (Advantages/Benefits) – Provide supporting evidence.
✔ Arguments Against (Limitations/Challenges) – Provide counterpoints.
✔ Scientific Examples or Evidence – Use real-world applications, data, or experiments.
✔ Conclusion – Summarize the discussion and make a final judgment.

Define the modern cell theory

The cell is the smallest living unit in all organisms. All living things are made up of cells. All cells come from pre-existing cells.

Define MR GREEN

Movement, reproduction, growth, response, excretion, exchange of gases, nutrition.

Identify the optimal pH range for the activity of:
a) Amylase
b) Pepsin

a) Amylase: pH 6.7 - 7.5 (neutral/slightly basic)
b) Pepsin: pH 1.5 - 2.5 (acidic)

Explanation:

• Amylase functions in the mouth and small intestine, where pH is neutral/slightly basic.

• Pepsin functions in the stomach, where pH is highly acidic due to HCl.

Define the term "enzyme specificity" in relation to amylase and pepsin.

Enzyme specificity refers to the ability of an enzyme to catalyse only one specific reaction due to the complementary shape of its active site and substrate.

Application:

• Amylase only breaks down starch into maltose, as its active site is specific to starch molecules.

• Pepsin only hydrolyses proteins into peptides because its active site binds only to protein molecules.

Outline how substrate concentration affects enzyme activity.

• As substrate concentration increases, enzyme activity also increases, as more substrate molecules collide with enzyme active sites.

• However, at high substrate concentrations, enzyme activity levels off as all active sites are occupied (saturation point).

• Beyond this point, increasing substrate concentration does not increase the reaction rate, as enzymes are working at maximum capacity.

Describe how temperature affects the function of amylase and pepsin.

• At low temperatures: Enzyme activity is slow due to reduced molecular movement and fewer enzyme-substrate collisions.

• At optimal temperature (~37°C for amylase, ~37-40°C for pepsin): Enzymes function most efficiently, with maximum reaction rate.

• At high temperatures (>50°C): Enzymes denature, meaning their active site loses shape, causing a permanent loss of function.

a) Analyse the graph showing enzyme activity vs. temperature: b) Explain why pepsin shows maximum activity at a lower temperature compared to amylase. c) Predict what would happen to both enzymes at 80°C and justify your answer.

a) Describe the trend shown for each enzyme.

• Both enzymes increase in activity as temperature rises until reaching their optimal temperature (~37°C).

• Beyond this, enzyme activity declines sharply, as denaturation occurs at high temperatures.

b) Explain why pepsin shows maximum activity at a lower temperature compared to amylase.

• Pepsin functions in the stomach, where conditions are acidic and slightly cooler.

• Amylase functions in the mouth and small intestine, which have a higher temperature tolerance.

c) Predict what would happen to both enzymes at 80°C and justify your answer.

• Both enzymes would be denatured, as extreme heat disrupts the protein structure of enzymes, changing the shape of the active site and preventing substrate binding.

Examine the experimental data on substrate concentration and reaction rate.

a) Describe the pattern shown in the table.

• The reaction rate initially increases with increasing substrate concentration.

• However, at high substrate concentrations, the rate levels off as enzymes reach their saturation point.

b) Explain why the reaction rate does not continue to increase indefinitely as substrate concentration rises.

• Enzyme saturation occurs, meaning all active sites are occupied.

• No additional substrate molecules can bind until enzymes release products.

Investigate how changes in pH affect the activity of pepsin.

Aim: To determine the effect of different pH levels on pepsin activity.

Hypothesis: Pepsin will exhibit highest activity at pH ~2 and lose function at neutral/alkaline pH.

Method:

1. Prepare test tubes with pepsin and protein substrate.

2. Adjust pH levels (e.g., pH 2, pH 5, pH 7, pH 9) using buffers.

3. Incubate at 37°C for 15 minutes.

4. Measure the rate of protein breakdown using a spectrophotometer (absorbance method).

5. Compare reaction rates across different pH levels.

Expected Results:

• Highest activity at pH 2.

• Reduced activity at pH 5 and 7.

• No activity at pH 9 (denaturation).

Assess how the differences in pH environments of the stomach and small intestine influence the digestion of carbohydrates and proteins.

• Stomach (pH 2, acidic):

  • Pepsin is active and breaks down proteins into peptides.

  • Amylase denatures due to acidity, so carbohydrate digestion stops.

• Small intestine (pH 7-8, neutral/slightly basic):

  • Pepsin is inactive, so protein digestion is completed by trypsin.

  • Amylase resumes starch digestion into maltose.

Conclusion:

• The pH environment determines enzyme activity.

• Acidic conditions support protein digestion, while neutral conditions support carbohydrate digestion.

Explain the role of temperature, pH, and substrate concentration in enzyme activity. Use graphs or tables to support your response.

Temperature:

• Graph: Bell-shaped curve with peak at optimal temp (~37°C).

• Too low → slow reaction; too high → denaturation.

pH:

• Graph: Peak at pH 2 for pepsin, pH 7 for amylase.

• Too high or low → denaturation.

Substrate Concentration:

• Graph: Increases until saturation point.

• After saturation, enzyme activity remains constant.