BIO 2.1 /AS91153

To carry out a practical investigation in a biological context with guidance

In this Achievement Standard, you must complete a practical biological investigation with supervision. This means you will be instructed on how to complete the investigation and be provided with all practical equipment required as well as reference material to help with your conclusion. The biological investigation you will undertake explores factors which affect enzyme activity.

WHAT ARE ENZYMES?

Enzymes are biological catalysts made up of large protein molecules. They speed up the chemical reactions inside the cell. The enzyme is made up of a combination of amino acids which for a chain of polypeptides between each other.
Enzymes are similar to other chemical catalysts. They participate in the reaction without getting affected. In other words, they speed up the chemical reactions inside the cells without getting consumed. Enzymes are affected by the hydrogen ion concentration (pH) and the temperature. Enzymes are highly specific compared to other catalysts, and each enzyme is specialized for one reactant substance. This reactant substance is called substrate, and it is specialized for one type of reaction or a few reactions. Enzymes lower the activation energy required to get the reaction started. Collectively, these are the most important properties of the enzyme.

FACTORS WHICH AFFECT ENZYME ACTION

Factor 1: Concentration of Enzyme

As the concentration of the enzyme is increased, the velocity of the reaction proportionately increases. This property is used for determining the activities of serum enzymes during the diagnosis of diseases.

Factor 2: Concentration of Substrate

In the presence of a given amount of enzyme, the rate of enzymatic reaction increases as the substrate concentration increases until a limiting rate is reached, after which further increase in the substrate concentration produces no significant change in the reaction rate. At this point, so much substrate is present that essentially all of the enzyme active sites have substrate bound to them.
In other words, the enzyme molecules are saturated with substrate. The excess substrate molecules cannot react until the substrate already bound to the enzymes has reacted and been released (or been released without reacting).

Factor 3: Effect of Temperature

The protein nature of the enzymes makes them extremely sensitive to thermal changes. Enzyme activity occurs within a narrow range of temperatures compared to ordinary chemical reactions. As you have seen, each enzyme has a certain temperature at which it is more active. This point is called the optimal temperature, which ranges between 37 to 40C°.
The enzyme activity gradually lowers as the temperature rises more than the optimal temperature until it reaches a certain temperature at which the enzyme activity stops completely due to the change of its natural composition.
On the other hand, if the temperature lowers below the optimal temperature, the enzyme activity lowers until the enzyme reaches a minimum temperature at which the enzyme activity is the least. The enzyme activity stops completely at 0C°, but if the temperature rises again, then the enzyme gets reactivated once more.

Factor 4: Effect of pH

The potential of hydrogen (pH) is the best measurement for determining the concentration of hydrogen ion (H+)in a solution. It also determines whether the liquid is acidic, basic or neutral. Generally, all liquids with a pH below 7 are called acids, whereas liquids with a pH above 7 are called bases or alkalines. Liquids with pH 7 are neutral and equal the acidity of pure water at 25 C°. You can determine pH of any solution using the pH indicators.

Enzymes are protein substances that contain acidic carboxylic groups (COOH–) and basic amino groups (NH2). So, the enzymes are affected by changing the pH value.
Each enzyme has a pH value that it works at with maximum efficiency called the optimal pH. If the pH is lower or higher than the optimal pH, the enzyme activity decreases until it stops working. For example, pepsin works at a low pH, i.e, it is highly acidic, while trypsin works at a high pH, i.e, it is basic. Most enzymes work at neutral pH 7.4.

Factor 5: Effect of Activators

Some of the enzymes require certain inorganic metallic cations, like Mg2+, Mn2+, Zn2+, Ca2+, Co2+, Cu2+, Na+, K+ etc., for their optimum activity. Rarely, anions are also needed for enzyme activity, e.g. a chloride ion (CI–) for amylase.

How Does Temperature Affect the Rate of Reaction?How does temperature affect the rate of reaction? The effect of temperature on rate of reaction is to speed it up, mainly by increasing the number of particles that achieve enough energy to cross the activation energy threshold. Whether colliding molecules react depends on their orientation.

HOW ENZYMES WORK USING THE LOCK AND KEY MECHANISM?

Enzyme | Biology SimulationsEnzymes are proteins that increase the rate of biological reactions. This simulation can be used to test how factors such as temperature, pH, and concentrations affect the reaction rates of two different enzymes in a biochemical pathway.

Enzymes - 1

PROTEIN STRUCTURE

Knowing how proteins are made and the different levels of structure they have is necessary to understanding how they can be affected by either a change in amino acid sequence or changes to the environment such as temperature or pH. Any alteration to the structure of the protein can affect its ability to function as required. Enzymes are proteins that act as catalysts for biochemical reactions within the body. Should the structure of the enzyme be altered it will be less able to catalyse the reaction efficiently.

THE PROCESS OF DENATURATION

What is Denaturation?

Denaturation is the process where a protein (or enzyme) loses its shape, which stops it from functioning properly. This usually happens due to factors like heat, pH changes, or chemicals.

Think of it like a key and a lock:
Normal enzyme = key (substrate).that fits into a specific lock (substrate).
Denatured enzyme = key is melted or bent out of shape—it no longer fits!

How Does Denaturation Happen?

💥 1. Heat:

Enzymes have an optimum temperature (usually around 37°C in the human body).
If the temperature gets too high (above 40-45°C), the enzyme’s bonds break, changing its shape.
Example: When you cook an egg, the clear egg white turns solid because the proteins are denatured!

🧪 2. pH Changes:

Enzymes also have an optimum pH (e.g., pepsin in the stomach works best at pH 2).
Too much acid or base disrupts the enzyme’s structure, causing denaturation.
Example: Lemon juice (acidic) curdling milk proteins.

🧴 3. Chemicals (e.g., alcohol, heavy metals):

Some chemicals break the bonds in proteins, denaturing them.
Example: Hand sanitizers use alcohol to denature bacterial proteins, killing germs!

Why is Denaturation Important?

⚠️ In Humans:

High fevers (above 40°C) can be dangerous because enzymes in the body start denaturing, affecting metabolism.

🏭 In Industry:

Enzymes in washing powders work best at specific temperatures—too hot, and they denature!

Temperature has a significant impact on enzyme activity. Here's a breakdown:

1. Increased Temperature (Initially)

Increased Kinetic Energy: As temperature rises, enzyme and substrate molecules gain kinetic energy, moving faster.
More Collisions: This leads to more frequent collisions between enzymes and their substrates.
Increased Reaction Rate: The likelihood of successful collisions (where the substrate binds to the enzyme's active site) increases, boosting the reaction rate.

2. Optimal Temperature

Peak Activity: For most enzymes, there's an optimal temperature where they function at their maximum rate.
Enzyme Specificity: This optimal temperature varies depending on the enzyme and the organism it's from.

3. High Temperatures (Beyond Optimal)

Denaturation: Excessive heat disrupts the weak bonds (hydrogen bonds) that maintain the enzyme's three-dimensional shape.
Loss of Function: This alters the shape of the active site, preventing the substrate from binding effectively. The enzyme essentially becomes non-functional.

In Summary

Mild Warming: Generally increases reaction rate.
Extreme Heat: Leads to enzyme denaturation and loss of activity.

REACTION OF ENZYME CATALASE WITH HYDROGEN PEROXIDE

REACTION BETWEEN HYDROGEN PEROXIDE AND CATALASE (YEAST)

EFFECT OF TEMPERATURE ON ENZYME CATALASE

How Does Temperature Affect Catalase Enzyme Activity?Catalase functions best at around 37 degrees Celsius -- as the temperature gets warmer or cooler than that, its ability to function will decrease.

FAIR TEST EXPERIMENT

A fair test experiment ensures that only one variable is changed while keeping all other factors constant to obtain reliable and valid results. Here are the steps to conduct a fair test experiment:

1. Identify the Question or Problem

Clearly define what you want to investigate.
Example: How does the amount of sunlight affect plant growth?

2. Identify the Variables

Independent Variable (IV): The factor you change (e.g., amount of sunlight).
Dependent Variable (DV): The factor you measure (e.g., plant height).
Controlled Variables (CVs): Factors that must remain the same (e.g., soil type, amount of water, type of plant).

3. Develop a Hypothesis

Make a prediction based on prior knowledge.
Example: If a plant receives more sunlight, then it will grow taller.

4. Plan the Experiment

Decide on the materials and method.
Ensure only the independent variable changes while everything else stays constant.
Example: Place plants in different sunlight conditions but give them the same amount of water and soil.

5. Conduct the Experiment

Follow the procedure carefully.
Record observations and measurements systematically.

6. Analyze the Results

Compare data to see if the independent variable affected the dependent variable.
Use tables, graphs, or charts for analysis.

7. Draw a Conclusion

State whether the hypothesis was supported or not.
Explain what was learned from the experiment.

8. Repeat for Reliability

Conduct multiple trials to ensure consistent results.
The more repetitions, the more reliable the data.

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