Photosynthesis
Cellular Respiration
Enzymes and Metabolism
Punnett squares and Pedigrees
2
State the Formula of Photosynthesis.
6CO2+6H2O+sunlight→C6H12O6+6O2
Carbon dioxide + water + sunlight → glucose + oxygen
2
State the formula of cellular respiration.
C6H12O6 + 6O2 → 6CO2 + 6H2O + Energy
glucose + oxygen → carbon dioxide + water + ATP
2
Zymase is an enzyme found in yeast which is important in respiration.
The image below shows a model of zymase and five different sugars: fructose, glucose, sucrose, lactose and maltose. (4 marks)
Predict which sugar is most likely to be respired by the yeast. Justify your answer.
Glucose fits in the active site of the enzyme in a lock and key model. Other sugars don’t fit.
2
Several genes have been discovered that are known to be responsible for hearing loss in humans.
Parents with normal hearing have a child with genetically determined hearing loss. Deduce and justify whether this characteristic is controlled by a dominant allele H or a recessive h allele .
Recessive/h because the parents do not have the condition but the child does or
because if it was dominant the parents would be affected too.
4
Select all the factors needed for plant growth.
Glucose
Light
Oxygen
Water Nutrients
Carbon dioxide
Outline the role of one factor in plant growth.
Light, Carbon Dioxide, Water, Nutrients
Light provides energy for photosynthesis, driving the conversion of carbon dioxide and water into organic matter and oxygen.
Carbon dioxide serves as the primary source of carbon for plants to synthesize glucose.
Water splits to produce oxygen.
Proper nutrient availability ensures optimal photosynthetic efficiency and overall plant health.
4
Yeast is a microorganism that is commonly used to make bread and beer. Yeast must respire to survive. Respiration is a reaction that occurs in the cells of living things, and is controlled by specific enzymes.
Some students planned a simple experiment to find out how temperature affects respiration in yeast. The students collected the carbon dioxide produced during respiration in a balloon. They suggested the following research question:
How does temperature affect the rate of respiration in yeast as measured by the volume of carbon dioxide produced in 15 minutes?
The image below shows how they have set their experiment up and the results they obtained:
The image below shows how they have set their experiment up and the results they obtained:
State the variables in this experiment.
Independent variable
Dependent variable Control variable 1
Control variable 2
IV: temperature
DV: size of balloon or volume of balloon or volume of CO2 produced
Any two reasonable control variables:
• volume of solutions
• concentration of sugar or type of sugar
• duration of reaction
• starting temperature of solution
4
In order for enzymes to effectively control reactions in the human body, the temperature must remain constant in the range OF 36.5C to 37.5C. Explain why enzyme-based reactions in the body are dependent on the temperature not moving outside this range.
Enzymes have an optimum temperature for them to be able to catalyse the chemical reaction at the highest rate.
Too cold and reactions do not occur fast enough. The substrate binds to the active site at a slower pace.
Too hot and enzymes change shape and no longer function. The enzymes denature.
4
Use the symbols H and h to show the genotype of the parents and child.
6
After the students had completed all of these investigations they wanted to conduct one final investigation. In the back of the science room they found an apparatus that had been donated to the school that looked like the image below.
Design an investigation that would use this apparatus to study
photosynthesis. Your plan should:
- state a problem to be studied
- formulate and explain a testable hypothesis
- identify relevant variables
- describe how to measure and manipulate the variables
- describe the method
- list any safety considerations.
Does photosynthesis work with the absence of CO2?
Hypothesis: If we stop inserting carbon dioxide in the apparatus with the plants, then photosynthesis will not function correctly and no oxygen will be produced, because carbon dioxide is essential for the photosynthesis.
Dependent variable: Carbon dioxide concentration
Independent variable: Oxygen produced
Control variables:
-Same plants, same soil, same conditions, same amount of water and soil.
Method:
-We will stop the carbon dioxide from entering the apparatus.
-Then, we will add water to the plants and connect the apparatus for measuring the quantities of oxygen and carbon dioxide.
-We will write the results on a table.
-The next step will be repeat the same process but with carbon dioxide entering the apparatus.
-We will then mesure the quantities of carbon dioxide and oxygen and write them in the table.
Finally, we will compare both results and find the conclusions.
Caution: It will be important to use carefully the apparatus that contains the carbon dioxide, if not the experiment will not result as ima gined.
6
Outline if the method in the graphic above will give sufficient data to answer the research question. Include 2 factors.
Any two of the following points:
• no and range is insufficient
• no and no repeats are shown
• no and no numerical data is generated
• no and no graph is possible
• no and the increment is too large
• yes and there is a range of temps used or the size of the balloons can be
compared
6
Predict what will happen to lactose in the intestines of adults who do not produce the enzyme lactase.
Explain how lactase secretion in adulthood could have become common in populations that keep cattle or other mammals and drink their milk.
Lactose is not digested (by human enzymes/digestive juices); bacteria/microbes in the gut digest the lactose.
Adults that continue to secrete lactase into adulthood have an advantage; they are better nourished on a diet containing milk; they avoid harmful effects of lactose intolerance; they are healthier so produce more children; their children inherit the trait of secreting lactase in adulthood.
6
Gene PAX3 is one of the genes that control hearing. The normal form of PAX3 is recessive (symbol , normal hearing). The mutated form of PAX3 is dominant (symbol , hearing loss).
Explain why a person with hearing loss possessing two dominant alleles for this characteristic (genotype ) would only have children with hearing loss.
NOTE: This form of hearing loss is controlled by a dominant allele.
The parent with the AA genotype will pass on an A (allele) to every child. The child will always inherit an A or dominant allele.
8
Suggest two improvements to this experiment. Justify your improvements.
SUGGESTIONS
• use a better measuring tool
• more trials
• larger temperature range
• control the mass of yeast or sugar
JUSTIFICATION
• this will give more precise data / quantitative data
• reduces experimental uncertainty
• this will give reliable or repeatable data
8
A group of students wanted to investigate the effect of pH on enzyme based reactions.(1 mark)
Formulate a research question for this investigation.
Identify the variables in this investigation.
Independent variable
Dependent variable Control variable 1
Control variable 2
How does pH affect reaction rate?
Independent variable: pH
Dependent variable: Reaction rate
Control variables (any two):
• amount of lactose/substrate
• surface area of lactose/substrate
• amount of enzyme/lactase
• volume of water
• concentration of enzyme solution
• temperature
• type of enzyme
8
The pedigree above tracks the presence of attached earlobes through a family's generations. Having attached earlobes is an autosomal recessive trait.
If individual III-6 married a man who was homozygous for unattached earlobes, what is most likely to be true regarding their children?
a) The children would all have partially attached earlobes.
b) All of their children would have attached earlobes.
c) All of their children would have unattached earlobes.
d) All the female children will have unattached earlobes, and all the male children will have attached earlobes.
c) All of their children would have unattached earlobes.