Uncategorized Questions
Explore questions in the Uncategorized category that you can ask Spark.E!
A student reading the researcher's report concluded that the difference between the resultsfor 30 seconds and 45 seconds was significant. Do you agree with his conclusion? Explainyour answer.
The presynaptic knob contains actin filaments and myosin molecules.The myosin molecules can attach to mitochondria and move them towards the presynapticmembrane, as shown in the diagram.Use your knowledge of how myosin and actin interact to suggest how the myosin moleculemoves the mitochondrion towards the presynaptic membrane.Do not include the roles of calcium ions and tropomyosin in your answer.
AMP-activated protein kinase (AMPK) is an enzyme that regulates a number of cellularprocesses. Exercise leads to activation of AMPK.The diagram shows one effect of activation of AMPK during exercise.CPT1 is a channel protein that transports fatty acids into mitochondria.Using the diagram above, explain the benefit of activation of AMPK during exercise.
The acidic pH conditions created by osteoclasts cause the inactive form of the proteinosteocalcin to change into the active form of osteocalcin.Suggest how.
The image shows glycogen granules present in skeletal muscle.Explain their role in skeletal muscle.
More than 99% of biological molecules are reabsorbed from the filtrate in the proximalconvoluted tubule.Despite this, the concentration of fluid in this tubule remains constant.Explain why.
The scientists also compared the diameter of samples of muscle fibres taken from youngmice and adult mice.Some of their results are shown in the graph.Describe two differences between these samples of muscle fibres.
Other than temperature, give two factors that affect the speed of nerve impulseconduction.
After observing the behaviour of the insect in Figure 2, the scientists hypothesised that ifan insect had one of its antennae removed it would have a tendency to turn to one side andmove in circles. The scientists tested this hypothesis by cutting one antenna off anotherinsect and observing its movement.The result of this experiment can be seen in Figure 3.Does the movement observed in Figure 3 support the scientists' hypothesis?Give the reason for your answer.
The scientists then compared the length of time that the control mice and the trained micecould carry out prolonged exercise. The trained mice were able to exercise for a longertime period than control mice.Explain why.
The body loses heat quickly in cold water. A researcher investigated the effect of length of time ina bath of ice-cold water on the reaction times of 20 healthy people aged between 21 and 23years of age.She measured each person's reaction time after being left in ice-cold water for 15, 30 or 45seconds. She also recorded each person's reaction time before being placed in the ice-coldwater (0 seconds).The table shows her results.One reason that reaction time is slower when body temperature falls is becausenerve impulse conduction is slower. Explain how a lower temperature leads to slowernerve impulse conduction.
One scientific study which analysed chromosome 14 involved 102 individuals. Thescientists recorded a sample size of 204. In this sample they detected 75 E280A mutationsbut only 74 potential AD cases (lines 19-21).Suggest explanations for the figures the scientists recorded.
Each year, a few people with type I diabetes are given a pancreas transplant. Pancreastransplants are not used to treat people with type II diabetes.Give two reasons why pancreas transplants are not used for the treatment of type IIdiabetes.
Give the name of the structure shown between points A and B.
Ten percent of the population on the Pacific island of Pingelap are affected by completeachromatopsia (lines 3-6).Use the Hardy-Weinberg equation to calculate the percentage of this population who areheterozygous for this disorder.Show your working.
This movement of mitochondria happens when nerve impulses arrive at the synapse.Suggest and explain one advantage of the movement of mitochondria towards thepresynaptic membrane when nerve impulses arrive at the synapse.
The pancreas produces the hormone insulin.Put a tick (✔) in the box next to the statement which describes incorrectly the action ofinsulin.
Explain why natural selection has not reduced the frequency of the E280A mutation in thepopulation (lines 16-17).
Scientists investigated the use of induced pluripotent stem cells (iPS cells) to treat type Idiabetes in mice. The scientists used four transcription factors to reprogramme skin cells toform iPS cells. The scientists then stimulated the in vitro differentiation of iPS cells intopancreatic cells.The scientists set up three experimental groups:• Group A - 30 mice with type I diabetes received pancreatic cell transplants derivedfrom iPS cells.• Group B - 30 mice with type I diabetes were left untreated.• Group C - 30 mice without diabetes were left untreated.The scientists measured the blood glucose concentration of all the mice on a weekly basisfor 12 weeks.The results the scientists obtained are shown in the graph.Suggest how transcription factors can reprogramme cells to form iPS cells.
Scientists investigated the effect of regular exercise on skeletal muscle fibres in mice. Thescientists compared the muscle fibres of mice after six weeks of regular exercise (trained mice)with those of mice that had not exercised (control mice). The scientists stained the muscle fibresfrom both sets of mice to show succinic acid dehydrogenase activity. The darker the stain thegreater the succinic acid dehydrogenase activity.The diagram below shows a typical set of results they obtained.Succinic acid dehydrogenase is an enzyme used in the Krebs cycle.Suggest one reason for the difference in the staining between the muscle fibres of thecontrol mice and the trained mice.