Effects of temperature and pH

Five tubes holding cooked egg-white are arranged as shown in the diagram. Protease solutions with different pH values are added to each tube. Which diagram represents the result of this experiment for a protease from the stomach?

May/June 2015

Which graph illustrates how temperature affects the rate of a reaction catalysed by amylase?

May/June 2019

Which word is used for an enzyme whose active site is altered by high temperature?

May/June 2021

The graph illustrates how the reaction rate of a protease from the stomach changes with pH. What best describes the pH at point X?

May/June 2022

A dilute starch solution becomes blue after a very dilute iodine solution is introduced. As amylase breaks down the starch, this colour fades away. The graph shows how the blue colour disappears at different temperatures. Which statement explains the pattern of the curve?

May/June 2022

Amylase is an enzyme which converts starch into maltose. The students arranged an experiment to examine how different temperatures affect the action of amylase on starch solution. They recorded how much starch was still present after $30$ minutes at a range of temperatures. Which graph would you expect the students to draw from their results?

May/June 2022

Which statement shows the optimum (best) temperature for enzyme activity?

May/June 2022

The graph indicates the concentration of maltose formed as amylase breaks down starch at different pH values. What accounts for the pattern of the graph between point X and point Y?

May/June 2023

The enzyme amylase speeds up the decomposition of starch into maltose. The influence of different pHs on the time needed for this decomposition to happen, while all other variables were kept constant, was investigated. Which graph shows the results of this investigation?

May/June 2025

Which enzyme catalyses the breakdown of its substrate most efficiently at a low pH?

May/June 2025

The graph illustrates the activity rate of enzyme X at a range of pH values. All other conditions are held constant. Using the data presented in the graph, which statement is correct?

May/June 2025

What is the name of the enzyme that regulates a reaction in which both the enzyme and the substrate may denature at high temperatures?

Oct/Nov 2015

The graph illustrates how the rate at which the fungus Penicillium produces penicillin changes with temperature at two different oxygen concentrations. What conclusion can be drawn from the graph?

Oct/Nov 2018

Describe and explain how each of the following influences enzyme activity: pH; temperature.

Oct/Nov 2018

Starch digestion takes place in the mouth cavity and in the duodenum, but it does not continue in the stomach. Why is this?

Oct/Nov 2020

Starch digestion takes place in the mouth cavity and in the duodenum, but it comes to an end in the stomach. What is the reason for this?

Oct/Nov 2020

A few laundry detergents used for cleaning clothes include enzymes. Those enzymes digest the molecules responsible for stains.

Oct/Nov 2021

The diagram illustrates the effect of temperature on the rate of an enzyme-controlled reaction. What explains the part of the graph labelled X?

Oct/Nov 2022

The graph shows how the activity of four enzymes, A, B, C and D, changes as $\text{pH}$ varies. Which enzyme functions in the stomach?

Oct/Nov 2022

Which graph most accurately shows how pH affects the activity of gastric protease?

Oct/Nov 2023

As illustrated, five test-tubes are prepared with cooked egg white. Cooked egg white contains a protein. Protease solutions at different pH values are then placed into each tube. Which diagram represents the outcome of this experiment for a protease from the stomach?

Oct/Nov 2024

Some students carried out an investigation into how temperature affects the breakdown of starch into maltose. They placed equal volumes of amylase and starch solution into several test-tubes. For 30 minutes, the test-tubes were kept at temperatures ranging from $10\,^{\circ}\text{C}$ to $60\,^{\circ}\text{C}$. After this, they measured the starch concentration in each test-tube. Which graph would be produced from these results?

Oct/Nov 2024

Single-cell protein may be made by culturing a fungus in a fermenter. Why does the fermenter need a cooling unit?

Oct/Nov 2024

Catalase is an enzyme present in potato tissue. It speeds up the decomposition of hydrogen peroxide into water and oxygen. Five identical potato discs were placed into $15\text{ cm}^3$ of a $3\%$ hydrogen peroxide solution at a temperature of $20\degree\text{C}$. The time needed to produce $5\text{ cm}^3$ of oxygen was measured. The same method was then carried out at $30\degree\text{C}$, $40\degree\text{C}$, $50\degree\text{C}$, $60\degree\text{C}$ and $70\degree\text{C}$. Which graph would represent the findings of the investigation?

Oct/Nov 2024