IB Biology HL Paper 3 Question Bank
The IB Biology HL Paper 2 Question Bank is a great resource for students preparing for their IB Biology HL exams. The question bank contains a wealth of questions, covering all the topics in the IB Biology HL syllabus. This makes it an invaluable resource for students who want to make sure they are fully prepared for their exams. Overall, the IB Biology HL Paper 2 Question Bank is an excellent resource for any student taking their IB Biology HL exams.
Biology Higher Level Paper 3
Time: 1 hour and 15 minutes
Instructions to candidates
- Do not open this examination paper until instructed to do so.
- Section A: answer all questions.
- Section B: answer all of the questions from one of the options.
- Write your answers in the boxes provided.
- A calculator is required for this paper.
- The maximum mark for this examination paper is [45 marks].
Answer all questions
1 – 3
Answer all of the questions from one of the options.
Option A – Neurobiology and behaviour
4 – 9
Option B – Biotechnology and bioinformatics
10 – 14
Option C – Ecology and conservation
15 – 19
Option D – Human physiology
20 – 24
1.) During muscular activity, the heart must deliver more blood to the tissues due to increased oxygen demand. Graph 1 shows the distribution of total blood flow (cardiac output) between muscles (gray-shaded bars) and all other parts of the body (black-shaded bars) in resting men and in both average men and top athletes doing heavy exercise. Graph 2 shows oxygen consumption by the muscles and all other parts of the body in the three groups. The value given for each bar represents the total body values.
A. Describe the relationship between exercise and total cardiac output.
B. (i) Calculate the percentage of cardiac output to the muscles for an average man during heavy exercise as compared to the total body value.
(ii) Calculate the increase in total oxygen consumption (ml min−1) for a top athlete during heavy exercise as compared to a resting man.
C. Using the data, explain how training affects an athlete’s body with respect to cardiac output and oxygen consumption.
Cardiac output to muscles / overall cardiac output increases. More in top athletes / with training. Training / top athletes decrease cardiac output to the rest of the body. Training increases oxygen consumption in muscles/ overall oxygen consumption during heavy exercise.
2.) An experiment was conducted to investigate the effect of temperature on the rate of cellular respiration in yeast cells. Cellular respiration is the process by which cells break down glucose to release energy in the form of ATP.
The experiment was set up as follows:
- A solution of yeast cells was prepared and divided equally into five test tubes.
- Each test tube was incubated at a different temperature (10°C, 20°C, 30°C, 40°C, and 50°C) for 10 minutes.
- After incubation, each test tube was tested for the presence of CO2 using a pH indicator.
The following results were obtained:
CO2 production (pH units)
a) (i) Which temperature had the highest rate of CO2 production?
The temperature of 30°C had the highest rate of CO2 production.
(ii) Which temperature had the lowest rate of CO2 production?
The temperatures of 10°C and 50°C had the lowest rate of CO2 production.
(iii) Why might changes in temperature affect the rate of cellular respiration?
Changes in temperature can affect the activity of enzymes involved in cellular respiration, as enzymes have an optimal temperature range in which they function best. At temperatures outside this range, enzyme activity can decrease, leading to a decrease in the rate of cellular respiration.
b) Calculate the average rate of CO2 production at each temperature.
Average rate of CO2 production at 10°C: 0.5 pH units
Average rate of CO2 production at 20°C: 1.0 pH units
Average rate of CO2 production at 30°C: 1.5 pH units
Average rate of CO2 production at 40°C: 1.0 pH units
Average rate of CO2 production at 50°C: 0.5 pH units
c) Based on the results, what can you conclude about the effect of temperature on the rate of cellular respiration in yeast cells?
The results indicate that the rate of cellular respiration in yeast cells is highest at a temperature of 30°C, and decreases as the temperature becomes either colder or hotter.
d) How might these results be useful in a real-world context?
These results may be useful in industries that use yeast cells, such as bread-making and beer-brewing, where temperature conditions can be optimized to maximize the rate of cellular respiration and therefore the efficiency of these processes.
3.) The table below shows the stomatal density and stomatal index in three different plant species.
Stomatal Density (per mm2)
Stomatal Index (%)
a) Define stomatal density and stomatal index.
Stomatal density is the number of stomata per unit area of leaf surface. Stomatal index is the percentage of epidermal cells that are stomata.
b) Which plant species has a higher stomatal density and what does this suggest about its environment?
Plant B has a higher stomatal density, which suggests that it grows in a drier or more arid environment where water is limiting. A higher stomatal density allows for more efficient gas exchange, but also results in higher water loss.
c) Which plant species has a higher stomatal index and what does this suggest about its water status?
Plant A has a higher stomatal index, which suggests that it has a higher water status compared to the other plant species. Stomatal index reflects the proportion of stomata to total epidermal cells and can be used as an indicator of the water status of the plant. A higher stomatal index indicates a higher proportion of open stomata, which allows for increased gas exchange and photosynthesis, but also results in higher water loss.
Answer all of the questions from one of the options.
Option A: Neurobiology and Behaviour
1.) Alcohol is a widely consumed substance that can have significant effects on the nervous system. In a recent study, the effects of alcohol on the function of neurons in the hippocampus, a brain region important for learning and memory, were investigated. The study was conducted using rat brain slices. The hippocampus was isolated from each rat brain and then divided into two groups: one group was treated with alcohol, and the other was used as a control. Neuronal activity was recorded using electrophysiology techniques.
The following results were obtained:
- Neuronal firing rate was significantly increased in the alcohol-treated group compared to the control group.
- The amplitude of neuronal signals was decreased in the alcohol-treated group compared to the control group.
a) How might the increased firing rate observed in the alcohol-treated group affect neuronal function in the hippocampus?
The increased firing rate observed in the alcohol-treated group may lead to increased excitatory activity in the hippocampus, which could impair cognitive function and lead to memory impairment.
b) How might the decreased amplitude of neuronal signals observed in the alcohol-treated group affect neuronal function in the hippocampus?
The decreased amplitude of neuronal signals observed in the alcohol-treated group may reflect reduced synaptic activity, which could also impair cognitive function and contribute to memory impairment.
c) What are the potential implications of these findings for individuals who regularly consume alcohol?
The findings of this study suggest that regular alcohol consumption may have negative effects on neuronal function in the hippocampus, potentially leading to cognitive impairments and memory deficits.
d) What further research could be done to better understand the effects of alcohol on neuronal function?
Further research could be done to investigate the effects of different levels and types of alcohol consumption on neuronal function in the hippocampus, as well as the potential for these effects to be reversible with abstinence or other interventions.
2.) The table below shows the results of a study investigating the effect of caffeine on the heart rate of rats.
Caffeine Dose (mg/kg body weight)
HR before (beats/min)
HR after (beats/min)
Difference in HR (beats/min)
a) Calculate the difference in heart rate for each caffeine dose.
The difference in heart rate for each caffeine dose is as follows:
- For 10 mg/kg body weight dose: 20 beats/min
- For 20 mg/kg body weight dose: 60 beats/min
- For 30 mg/kg body weight dose: 80 beats/min
b) Calculate the percentage increase in heart rate for each caffeine dose.
The percentage increase in heart rate for each caffeine dose is as follows:
- For 10 mg/kg body weight dose: (20/310) x 100% = 6.45%
- For 20 mg/kg body weight dose: (60/300) x 100% = 20%
- For 30 mg/kg body weight dose: (80/310) x 100% = 25.81%
c) Discuss one potential limitation of using animal models to study human physiology.
One potential limitation of using animal models to study human physiology is that the results obtained from animal studies may not always be applicable to humans due to differences in anatomy, physiology, and genetics between species.
3.) The table below shows the results of a study investigating the effect of different levels of light intensity on the activity level of fruit flies.
Light Intensity (lux)
Activity level (number of movements per minute)
a) Calculate the range of activity levels observed in this study.
The range of activity levels observed in this study is 50-80 (i.e., the difference between the minimum and maximum values in the table).
b) Calculate the mean activity level for the fruit flies across all levels of light intensity tested.
The mean activity level for the fruit flies across all levels of light intensity tested is calculated as follows:
((30 + 40 + 70 + 80 + 75 + 60) / 6) = 59.17 movements per minute.
c) Explain how this study could be modified to determine if the observed effect of light intensity on fruit fly activity level is due to a direct effect of light on the fruit flies or a secondary effect of light on other environmental factors.
To determine if the observed effect of light intensity on fruit fly activity level is due to a direct effect of light on the fruit flies or a secondary effect of light on other environmental factors, the study could be modified as follows: Fruit flies could be exposed to different light intensities in a controlled environment where all other environmental factors (e.g., temperature, humidity, sound) are held constant. The same experiment could also be conducted in a dark environment with the only variable being light intensity. By comparing the results of the two experiments, it would be possible to determine whether the observed effect of light intensity on fruit fly activity level is due to a direct effect of light or a secondary effect of other environmental factors.
4.) The table below shows the results of an experiment investigating the effect of different neurotransmitters on the activity of a neuron.
Frequency of neuron firing (Hz)
a) Which neurotransmitter had the greatest effect on the neuron’s activity?
Glutamate had the greatest effect on the neuron’s activity, increasing the frequency of neuron firing to 60 Hz.
b) Which neurotransmitter had the least effect on the neuron’s activity?
GABA had the least effect on the neuron’s activity, decreasing the frequency of neuron firing to 5 Hz.
c) Explain the mechanism by which neurotransmitters affect neuron activity.
Neurotransmitters bind to receptors on the postsynaptic membrane of a neuron, which can either increase or decrease the probability of the neuron firing an action potential. For example, glutamate is an excitatory neurotransmitter that binds to ionotropic receptors, causing an influx of positively charged ions and depolarizing the membrane potential, whereas GABA is an inhibitory neurotransmitter that binds to ionotropic receptors, causing an efflux of negatively charged ions and hyperpolarizing the membrane potential.
5.) The table below shows the results of an experiment investigating the effect of different types of music on heart rate in humans.
Type of music
Average heart rate (beats per minute)
a) Which type of music had the highest average heart rate?
Heavy metal had the highest average heart rate of 85 beats per minute.
b) Which type of music had the lowest average heart rate?
Classical had the lowest average heart rate of 60 beats per minute.
c) Explain the possible mechanism by which music affects heart rate.
Music may affect heart rate through its ability to stimulate the sympathetic nervous system, which can increase heart rate and blood pressure, or through its ability to induce relaxation and decrease stress, which can decrease heart rate and blood pressure. The specific mechanisms by which different types of music affect heart rate may vary depending on factors such as tempo, rhythm, and lyrics.
6.) Discuss the role of neurotransmitters in the communication between neurons and their effect on behaviour.
Neurotransmitters are chemical messengers that transmit signals between neurons and other cells in the nervous system. They play a crucial role in the communication between neurons and are involved in a wide range of behaviors.
When an action potential reaches the end of a neuron, it triggers the release of neurotransmitters into the synaptic cleft. These neurotransmitters then bind to receptors on the post-synaptic neuron, triggering a response. The specific type and amount of neurotransmitters released can vary depending on the type of neuron and the context of the communication.
Some neurotransmitters are associated with specific behaviors. For example, dopamine is often associated with reward and motivation, while serotonin is associated with mood regulation and sleep. Imbalances in neurotransmitter levels have been linked to various disorders, including depression, anxiety, and schizophrenia.
Drugs that affect neurotransmitter levels can also have significant effects on behavior. For example, drugs that increase dopamine levels can lead to increased feelings of pleasure and reward, while drugs that decrease dopamine levels can lead to depression and anhedonia.
In conclusion, neurotransmitters play a crucial role in the communication between neurons and are closely linked to behavior. The specific neurotransmitters involved and their levels can have a significant impact on behavior, and imbalances or disruptions in neurotransmitter levels can lead to a range of disorders.
Option B: Biotechnology and Bioinformatics
7.) Cancer is a complex disease that arises from genetic mutations in cells. Genomic analysis is used to identify these mutations and develop targeted therapies. Biotechnology and bioinformatics play a crucial role in genomic analysis of cancer by providing tools to analyze large amounts of genomic data.
Here is the following table:
Frequency in Cancer
a) What is the significance of the mutations in TP53, KRAS, PIK3CA, BRAF, and EGFR in cancer?
TP53, KRAS, PIK3CA, BRAF, and EGFR are oncogenes or tumor suppressor genes that are frequently mutated in cancer cells. These mutations can lead to uncontrolled cell growth and division, which can result in tumor formation.
b) How can bioinformatics be used to identify mutations in cancer cells?
Bioinformatics can be used to analyze large amounts of genomic data and identify mutations in cancer cells. Tools such as genome sequencing and data mining can be used to identify mutations that are associated with cancer.
c) What are the advantages of targeted therapies for cancer patients?
Targeted therapies are designed to target specific mutations in cancer cells, which can result in more effective treatment with fewer side effects compared to traditional chemotherapy. Targeted therapies can also be personalized based on the genetic profile of individual tumors.
d) Using the data in the table, if a tumor has mutations in both KRAS and PIK3CA, what percentage of cancer cases is this consistent with?
This is consistent with approximately 7.8% of cancer cases, calculated by multiplying the frequencies of mutations in KRAS and PIK3CA (0.30 x 0.26 = 0.078).
8.) The table below shows the amino acid sequences of two related proteins, A and B.
Protein Amino Acid Sequence
a) Identify the type of mutation that has occurred between proteins A and B.
The mutation that occurred between proteins A and B is a missense mutation.
b) Determine the nucleotide sequence change that led to the mutation.
The nucleotide sequence change that led to the mutation is the substitution of the codon GAA (Glu) in protein A with the codon AAA (Lys) in protein B.
c) Explain how this mutation could potentially affect the function of the protein.
The substitution of the Glu residue with Lys could potentially affect the function of the protein by altering the protein’s 3D conformation, affecting its ability to bind to other molecules or altering its enzymatic activity.
9.) The table below shows the results of a microarray experiment investigating the gene expression in two different types of cancer cells, A and B.
Cancer Cell Type A
Cancer Cell Type B
a) Explain what is meant by upregulation and downregulation of a gene.
Upregulation of a gene refers to an increase in the expression of the gene, while downregulation of a gene refers to a decrease in the expression of the gene.
b) Based on the results, which gene(s) could potentially be used as a diagnostic marker for distinguishing between the two types of cancer cells?
Gene G1 could potentially be used as a diagnostic marker for distinguishing between the two types of cancer cells since it is upregulated in Cancer Cell Type A and downregulated in Cancer Cell Type B.
c) Discuss one potential limitation of using microarray technology in gene expression analysis.
One potential limitation of using microarray technology in gene expression analysis is that it assumes that all genes are expressed at the same level in both samples being compared. However, this may not always be the case, and variability in gene expression between samples can lead to inaccurate results.
10.) The table below shows the DNA sequence of a gene and the corresponding amino acid sequence of the protein it codes for.
DNA Sequence: ATG GCA TCT GAA ATG ACG TTC GGG GTG AGG
Amino Acid Sequence: Met Ala Ser Glu Met Thr Phe Gly Val Arg
a) Identify the start codon and the stop codon in the DNA sequence.
The start codon in the DNA sequence is ATG, and the stop codon is not present.
b) Determine the total number of nucleotides and the total number of amino acids in the gene.
The total number of nucleotides in the gene is 27 (9 codons x 3 nucleotides per codon), and the total number of amino acids is 9.
c) Explain how a frameshift mutation could potentially affect the amino acid sequence of the protein.
A frameshift mutation could potentially affect the amino acid sequence of the protein by shifting the reading frame, resulting in a different sequence of codons being read. This can cause a premature stop codon to be read, truncating the protein and potentially altering its function.
11.) Explain the principles of genetic engineering and how it has been used to produce insulin.
Genetic engineering is a powerful tool that allows scientists to manipulate the DNA of organisms in order to create new traits or modify existing ones. The principles of genetic engineering involve identifying the gene of interest, isolating and cloning the gene, inserting it into the host organism’s DNA, and allowing the organism to express the gene. One application of genetic engineering is the production of insulin. Insulin is a hormone that regulates blood sugar levels, and is normally produced by the pancreas. However, in people with type 1 diabetes, the pancreas does not produce enough insulin, and they need to inject insulin to manage their blood sugar levels.
To produce insulin, scientists isolate the human insulin gene, which codes for the production of insulin, and then insert it into bacteria or yeast cells. These cells act as “factories” that produce human insulin. The process involves several steps, including the creation of a recombinant DNA molecule, which contains the human insulin gene and the bacterial or yeast DNA, and the introduction of this DNA into the host cell using various techniques, such as transformation or electroporation.
Once the recombinant DNA is introduced into the host cell, the cell is grown in a culture, and the insulin is extracted and purified from the culture medium. This process has revolutionized the production of insulin, as it allows for the large-scale production of human insulin at a lower cost than extracting it from animal sources. It has also enabled the development of new forms of insulin, such as rapid-acting insulin analogs, which have improved the treatment options for people with diabetes. The principles of genetic engineering have been applied to many other areas of biotechnology, and have the potential to provide solutions to a wide range of challenges in fields such as medicine, agriculture, and environmental science.
Option C: Ecology and Conservation
12.) The Amazon rainforest is one of the most biodiverse regions in the world, with an estimated 16,000 species of trees and over 2.5 million species of insects. However, climate change is expected to have a significant impact on the biodiversity of the Amazon rainforest.
Here is the following Table:
a) How does climate change affect biodiversity in the Amazon rainforest?
Climate change affects biodiversity in the Amazon rainforest by altering temperature and precipitation patterns, which can cause changes in the timing of plant growth, pollination, and migration of animals. These changes can disrupt ecological interactions and lead to declines in species abundance and diversity.
b) What are the consequences of a decrease in precipitation for the Amazon rainforest ecosystem?
A decrease in precipitation can lead to drought, which can increase the risk of wildfires and reduce plant growth, leading to declines in primary productivity and species diversity.
c) Using the data in the table, what is the percentage decrease in species richness projected by climate change?
The percentage decrease in species richness projected by climate change is approximately 18.75%, calculated by dividing the difference in species richness between the current value and projected value by the current value and multiplying by 100 [(16,000-13,000)/16,000 x 100 = 18.75%].
d) How can conservation efforts mitigate the impact of climate change on the Amazon rainforest?
Conservation efforts can mitigate the impact of climate change on the Amazon rainforest by protecting key habitats, promoting sustainable land use practices, and supporting reforestation efforts. Protected areas can provide refuge for species that are vulnerable to climate change, while sustainable land use practices can help to reduce deforestation and mitigate the effects of climate change.
e) What are some challenges in implementing effective conservation efforts in the Amazon rainforest?
Challenges in implementing effective conservation efforts in the Amazon rainforest include limited funding and resources, conflicting interests among stakeholders, and lack of effective governance and enforcement of regulations. Additionally, conservation efforts must be tailored to the local context and take into account the cultural and economic needs of local communities.
13.) The table below shows the biomass and diversity of three different trophic levels in a food web.
Diversity (number of species)
a) Calculate the total biomass and diversity of the entire food web.
Total Biomass = 100 + 10 + 1 = 111 kg/m²
Total Diversity = 10 + 5 + 3 = 18 species
b) Which trophic level has the highest diversity? Justify your answer.
Producers have the highest diversity with 10 species.
c) Discuss one potential limitation of using biomass as a measure of ecosystem health.
One potential limitation of using biomass as a measure of ecosystem health is that it does not provide information about the diversity or distribution of species within the ecosystem. A high biomass may indicate a high abundance of a single species, rather than a diverse and healthy ecosystem.
14.) The table below shows the concentration of dissolved oxygen and the number of fish observed in a stream at different locations.
Dissolved Oxygen (mg/L)
Number of Fish
a) Calculate the total number of fish observed in the stream.
Total number of fish = 20 + 10 + 5 + 0 = 35 fish
b) Which location has the highest concentration of dissolved oxygen? Justify your answer.
Location A has the highest concentration of dissolved oxygen with 10 mg/L.
c) Discuss one potential limitation of using fish population data to make conclusions about water quality.
One potential limitation of using fish population data to make conclusions about water quality is that it does not provide information about other factors that may be affecting fish populations, such as predation, competition, or habitat quality. Additionally, some fish species may be more tolerant of poor water quality than others, which can affect population data.
15.) The table below shows the population size and birth rate for two different bird species over three years.
Species A Population Size
Species A Birth Rate
Species B Population Size
Species B Birth Rate
a) Calculate the total number of individuals for each bird species across all three years.
Total Species A population size = 100 + 120 + 150 = 370 individuals
Total Species B population size = 50 + 60 + 70 = 180 individuals
b) Which bird species has the highest average birth rate? Justify your answer.
Species A has the highest average birth rate with 0.18 births/individual/year.
c) Discuss one potential limitation of using birth rate as a measure of population growth.
One potential limitation of using birth rate as a measure of population growth is that it does not take into account mortality or emigration. A population with a high birth rate may still have a low overall growth rate if there are high rates of mortality or emigration. Additionally, birth rates may fluctuate over time due to environmental factors or other variables.
16.) Explain the concept of ecological succession and how it relates to ecosystem development.
Ecological succession is a natural process that occurs over time in ecosystems, whereby a series of changes in plant and animal communities occur, leading to a more complex and diverse ecosystem. It is the process by which an ecosystem develops, matures and changes in response to changes in environmental conditions.
There are two types of ecological succession, primary and secondary succession. Primary succession is the process by which an ecosystem develops on bare rock, newly formed land or other areas that have no soil. Secondary succession, on the other hand, is the process by which an ecosystem develops on previously established ecosystems that have been disturbed by natural or human-induced events such as fires, logging or farming.
In both primary and secondary succession, the process begins with pioneer species, which are the first organisms to colonize an area. These organisms are usually lichens or mosses, which are adapted to living in harsh, nutrient-poor environments. As these organisms die, they release nutrients and organic matter into the soil, which allows for the growth of other plants.
Ecological succession is important for ecosystem development because it allows for the establishment of a stable and sustainable community of organisms that can maintain itself over time. Each stage of succession plays an important role in creating the conditions necessary for the next stage to occur, and ultimately leads to the development of a more complex and diverse ecosystem. The process of ecological succession can take hundreds or even thousands of years, and is influenced by factors such as climate, soil, topography and the presence of other organisms in the ecosystem.
Option D: Human Physiology
17.) Exercise has numerous benefits for human health, including improving cardiovascular function. One way to measure cardiovascular function is by monitoring heart rate and blood pressure during exercise.
Heart Rate (beats/min)
Systolic Blood Pressure (mmHg)
Diastolic Blood Pressure (mmHg)
a) How does exercise affect heart rate and blood pressure?
Exercise increases heart rate and blood pressure due to the increased demand for oxygen and nutrients by working muscles. This causes the heart to pump more blood and the blood vessels to constrict to maintain blood flow to the muscles.
b) What is the relationship between exercise intensity and heart rate and blood pressure?
There is a positive relationship between exercise intensity and heart rate and blood pressure, meaning that as exercise intensity increases, heart rate and blood pressure also increase. This relationship is due to the increased demand for oxygen and nutrients by working muscles.
c) Using the data in the table, what is the difference in systolic blood pressure between resting and high-intensity exercise?
The difference in systolic blood pressure between resting and high-intensity exercise is 60 mmHg, calculated by subtracting the resting systolic blood pressure (120 mmHg) from the high-intensity systolic blood pressure (180 mmHg).
d) What is the significance of changes in heart rate and blood pressure during exercise for cardiovascular health?
Changes in heart rate and blood pressure during exercise can indicate the health of the cardiovascular system. Regular exercise can help to improve cardiovascular function by increasing the strength of the heart and blood vessels, reducing the risk of cardiovascular disease.
e) How can regular exercise help to improve cardiovascular function and reduce the risk of cardiovascular disease?
Regular exercise can help to improve cardiovascular function by strengthening the heart and blood vessels, reducing inflammation, and improving blood lipid levels. These benefits can reduce the risk of cardiovascular disease and improve overall health. However, it is important to start slowly and gradually increase exercise intensity to avoid injury and allow the body to adapt to the increased demand for oxygen and nutrients.
18.) The table below shows the concentrations of ions in a cell at rest and during an action potential.
Ion Concentration at rest
Concentration during action potential
Na+ 15 mM
K+ 150 mM
K+ 150 mM
Cl- 5 mM
a) Explain how the concentrations of Na+, K+, and Cl- ions change during an action potential.
During an action potential, there is a rapid depolarization phase followed by a repolarization phase. During depolarization, Na+ ions rapidly enter the cell, causing a spike in their concentration. This is followed by a rapid efflux of K+ ions during the repolarization phase, leading to a drop in their concentration. The concentration of Cl- ions also increases slightly during the depolarization phase.
b) What is the main factor responsible for the change in the concentration of Na+ during an action potential?
The main factor responsible for the change in the concentration of Na+ during an action potential is the opening of voltage-gated Na+ channels in the cell membrane, which allows Na+ ions to flow into the cell down their concentration gradient.
c) What is the main factor responsible for the change in the concentration of K+ during an action potential?
The main factor responsible for the change in the concentration of K+ during an action potential is the opening of voltage-gated K+ channels in the cell membrane, which allows K+ ions to flow out of the cell down their concentration gradient.
19.) The table below shows the partial pressures of gases in the alveoli and the pulmonary capillaries.
Alveolar Partial Pressure (mm Hg)
Pulmonary Capillary Partial Pressure (mm Hg)
a) Explain how oxygen is transported from the alveoli to the pulmonary capillaries.
Oxygen is transported from the alveoli to the pulmonary capillaries by diffusion. Since the partial pressure of oxygen is higher in the alveoli (100 mm Hg) than in the pulmonary capillaries (40 mm Hg), oxygen moves down its concentration gradient from the alveoli into the capillaries.
b) Explain how carbon dioxide is transported from the pulmonary capillaries to the alveoli.
Carbon dioxide is transported from the pulmonary capillaries to the alveoli by diffusion. Since the partial pressure of carbon dioxide is higher in the capillaries (45 mm Hg) than in the alveoli (40 mm Hg), carbon dioxide moves down its concentration gradient from the capillaries into the alveoli.
c) What would happen to the partial pressure of oxygen in the alveoli if the partial pressure of carbon dioxide in the alveoli increased?
If the partial pressure of carbon dioxide in the alveoli increased, it would lead to a decrease in the partial pressure of oxygen in the alveoli, as the two gases are in equilibrium. This would make it harder for oxygen to diffuse from the alveoli into the pulmonary capillaries, potentially leading to hypoxia.
20.) The table below shows the concentrations of various hormones in the blood before and after a meal.
Concentration before meal
Concentration after meal
a) What is the main function of insulin in the body?
The main function of insulin in the body is to decrease blood glucose levels by promoting the uptake of glucose by cells, particularly in the liver, muscle, and adipose tissue, and the conversion of glucose to glycogen for storage.
b) What is the main function of glucagon?
The main function of glucagon is to increase blood glucose levels by promoting the breakdown of glycogen in the liver into glucose and the production of glucose from amino acids and other sources through gluconeogenesis.
c) Explain the role of leptin in regulating appetite and weight.
Leptin is a hormone produced by adipose tissue that plays a role in regulating appetite and weight by signaling to the hypothalamus in the brain to decrease food intake and increase energy expenditure. Higher levels of leptin in the blood signal to the brain that the body has sufficient energy stores, which leads to a decrease in appetite and an increase in energy expenditure. In contrast, lower levels of leptin signal to the brain that the body needs to consume more food and conserve energy, leading to an increase in appetite and a decrease in energy expenditure.
24.) Outline the method of ATP production used by muscle fibers during the exercise of varying intensity and duration.
During exercise, muscle fibers utilize ATP (adenosine triphosphate) to provide energy for muscle contractions. However, the amount of ATP stored in muscle fibers is limited and can only sustain muscle contraction for a short period. Therefore, the body uses various energy systems to produce ATP to meet the energy demands of the muscle fibers during exercise.
For short-term, high-intensity exercises lasting less than 10 seconds, muscle fibers rely primarily on the phosphagen system to produce ATP. In this system, stored creatine phosphate (CP) is used to quickly regenerate ATP. This system is most efficient for high-intensity activities such as sprinting, jumping, or weightlifting.
For exercises lasting up to 2-3 minutes at high intensity, the glycolytic system is the primary source of ATP. This system breaks down glucose or glycogen (stored glucose in muscles and liver) to produce ATP. However, this process does not require oxygen, which makes it anaerobic. It produces lactic acid as a by-product, which can cause fatigue and muscle soreness.
For low to moderate-intensity exercises lasting longer than 3 minutes, the oxidative system is the primary source of ATP. This system requires oxygen and breaks down glucose, glycogen, or fats to produce ATP. This process takes longer but is more efficient in producing ATP. It is also the primary energy system used during endurance exercises such as long-distance running, cycling, or swimming.