Biology Masterclass

Consider an enzyme- facilitated reaction in which the concentration of the enzyme is constant. Which one of the following graphs shoes the effect of increasing substrate concentration on the rate of product formation

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Which one of the following is a correct summary of the main events in photosynthesis?

• Light is required to join carbon dioxide to hydrogen ( which was split from water using ATP) in carbohydrate production

• Oxygen reacts with a carbohydrate to produce water and carbon dioxide in the presence of light

• Light splits Carbon dioxide producing oxygen gas, and the resulting carbon then combines with oxygen and hydrogen obtained from water to produce carbohydrate

• Carbon dioxide combines with hydrogen split from water by light to produce carbohydrate using ATP

Tryptophan is an amino acid that is used by many bacteria. Genes that code for the production of tryptophan are found on bacterial DNA together ( trp operon). In the process of gene regulation, a repressor protein binds to the trp operon. When binding occurs, the process of tryptophan production stops. This is seen in the diagram below. When this binds, which of the following would be blocked from functioning normally

• DNA polymerase

• RNA polymerase

• Endonuclease

• DNA ligase

s. anatum is not a common cause of food poisoning. The graph blow displays the average monthly notification rate per 100,000 of the population for the illness over a 5 year period. it can be concluded from the data that

• there are four periods in which the notification rate is greater than six per 100,000

• the notification rate is always lowers during September of each year

• the notification rate is fairly steady over the 5 year period

• the notification rate in 2001 was highest in may

In the production of isoleucine from threonine in bacteria ( Biochemical Pathway 1 = BP1) the end product acts as an inhibitor of the first enzyme in the pathway. In the production of arginine (BP2) the end product has no influence on other enzymes. It is reasonable to conclude that

• BP 1, if the production of enzyme 3 stops there would be continuous production of isoleucine

• BP2, providing all enzymes are present, the production of arginine would be continuous if there was a continuous supply of substrate

• BP2, if the production of enzyme 3 stops there would be continuous production of arginine

• BP1, providing all enzymes are present, the production of isoleucine would be continuous if there was a continuous supply of threonine

The diagram shows a summary of steps in the insulin signalling pathway that results in increased glucose. A scientist studied this pathway in Eleni and Shani. Elenis pathway is the same as the diagram above. The scientist discovered the gene that encodes for the insulin receptor in Shani has a mutation and insulin cannot bind. From this information it is correct to conclude

• Insulin acts as a hydrophobic signalling molecule in Eleni and Shani

• Insulin will bind to a different receptor and activate different secondary messengers in Shani

• Shani is unable to produce the secondary messengers required for transduction

• The presence of insulin in Eleni would cause an increase in the concentration of secondary messenger molecules

Hybridoma cells are used to produce monoclonal antibodies because:

• They do not replicate

• They act on multiple antigens

• Their antibodies replicate

• Plasma cells are short-lived

In India, scientists was studying fossils from a coal deposit formed during the Permian period (290–245 million years ago). They found three fossil species from the same genus in different levels (strata) of the coal. When radiocarbon dating on these fossils was performed, it showed exactly the same levels of carbon-14 in all three fossil species. The data is summarised in the table. Which of the following is the correct conclusion to draw from these findings

• There is no evolutionary relationship between these three fossil species.

• G. clarkeana is the common evolutionary ancestor of G. major and G. obliqua

• As carbon dating is a more reliable dating technique than analysis of strata in coal deposits, the fossils of G. major, G. obliqua and G. clarkeana are all of the same age.

• An analysis of strata in coal deposits is a more reliable dating technique than carbon dating for Permian fossils; the fossil of G. major is younger than the fossil of G. obliqua.

Cells break down hydrogen peroxide into water & oxygen gas with the help of the enzyme catalase. The optimum pH is 7. Student used potato mixed with distilled water and hydrogen peroxide added

Test 1 used 5 mL of 3% hydrogen peroxide solution and 0.5 mL of catalase suspension at 20 °C in a buffer solution (pH 7) Test 2 was carried out under identical conditions to Test 1, except for one factor that the student changed. An explanation for the results of test 2 would be:

• Increased the concentration of catalase by adding less water to the ground potato

• increased the temperature by placing the test tube in a water bath set at 30 °C.

• used a hydrogen peroxide solution with a higher concentration

• added a catalase suspension made from a cooked potato chip.

A class of Biology students were investigating antibiotic resistance in the bacteria Escherichia coli. Each of the students carried out identical tests at the same time and in the same environment. The results were consistent across the class except for the results of one student. What type of error caused this one different result?

• Random Error

• Systematic Error

• Selection Bias

• Repeatability