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BIOLOGY - TERM 2 ASSESSMENT ​
INDIVIDUAL COMPONENT​
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ABHINAV KONDAPAVULOORI ​
YEAR 11 - BIOLOGY
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INDEX
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Inquiry question - Pg. 2​
Research:
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What is PKU? - Pg. 2
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PAH enzyme’s ideal conditions? - Pg. 3
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What is the enzyme associated with PKU? - Pg. 2
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Why and how does the mutation of the PAH enzyme cause PKU? - Pg. 3
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What happens if the PAH enzyme doesn’t break down phenylalanine?​
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Why can’t the reaction just happen slowly without PAH, as enzymes are only there
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- Pg. 4
to ‘speed up’ reactions? - Pg. 5
What are the contributing environmental and non-environmental factors to
genetic mutations in the PAH gene that lead to enzyme deficiency? - Pg. 6
How do people diagnosed with PKU live, and what precautions do they take (diet)?
- Pg. 7
PKU statistics : - Pg. 8​
APA 7 Referencing:
-​ Information - Pg. 8
-​ Statistics - Pg. 10
-​ Images - Pg. 10​
Progress Log - Pg. 10 ​
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Group contributions : - Pg. 14​
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Inquiry question:
“How can environmental factors affect an enzyme and lead to a disease in humans?”
Research:​
What is PKU?​
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PKU—short for phenylketonuria—is a rare genetic disease that arises due to an enzyme that
stops working effectively because of a mutation in its gene. This halts the decomposition of a
specific amino acid that plays a very critical role in the human body. As a result of this faulty
(denatured) enzyme activity (or no activity at all), normal metabolic processes are disrupted,
preventing the body from processing this amino acid properly. Without the enzyme, the
undecomposed amino acid accumulates in the blood and organs of the diagnosed individual ,
where high amounts of the amino acid can be toxic. Because of this, PKU makes a clear
example of how even a small change or abnormality in enzyme functionality can have serious
repercussions . (Further details about the enzyme, substances, disease, etc., are given below.)​
(Mayo Clinic, 2022)​
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What is the enzyme associated with PKU?​
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Phenylalanine Hydroxylase - (PAH) is the enzyme responsible for the breaking down of
phenylalanine (an amino acid that is found in protein-containing food) into a substance
called tyrosine (a byproduct substance that is produced after PAH breaks down
phenylalanine, which is important for many biological functions).​
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Phenylalanine hydroxylase is primarily located in the liver, where it plays a crucial role in
maintaining amino acid balance. When PAH is deficient or non-functional due to genetic
mutation, phenylalanine builds up in the body, leading to serious health effects associated
with PKU. (Better Health Clinic, 2022)​
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As shown in the picture above, phenylalanine hydroxylase (PAH) is a tetrameric enzyme,
meaning it is made up of four subunits that work together to perform its function. It also
requires iron and tetrahydrobiopterin cofactors, which are essential for its catalytic activity
in converting phenylalanine to tyrosine. (Iron helps in the chemical reaction, and BH4 helps
give PAH energy to break down phenylalanine.) (Science Direct, 2010)​
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Individuals that are diagnosed with PKU have a mutation in their PAH gene - which leads to
very little or no activity of the enzyme.
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PAH enzyme’s ideal conditions?
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The PAH enzyme is primarily found in the liver and functions best in the liver’s natural
conditions—around 37°C and at a slightly alkaline pH of about 7.4. These conditions help
maintain the enzyme’s proper shape and efficiency. When the temperature rises above or
falls below this optimal range, the enzyme’s structure can become unstable - can become
“Denatured” - ‘Out of shape’, where the protein unfolds and loses its functional shape.
Similarly, deviations from the ideal pH can disrupt the ionic bonds and hydrogen bonding
that stabilize the enzyme’s three-dimensional structure, causing the active site—the region
where the substrate binds—to become distorted. ​
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This distortion reduces the enzyme’s ability to bind phenylalanine effectively, lowering its
catalytic activity. As a result, even small changes in temperature or pH can significantly
impair PAH function. ​
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(National Institute of Health, 2023)
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Why and how does the mutation of the PAH enzyme cause PKU?
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The mutation of the PAH enzyme is passed down by a process called ‘autosomal
recessive pattern’—meaning that both the biological parents must have the mutated
PAH gene for the child to be diagnosed with PKU. (This is one of the reasons why
PKU is so rare—it isn’t common that both the mother and father have the recessive
gene mutation.) ​
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(National institute of child health and human development, 2024)​
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(Retina Australia, 2025)​
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The inherited variation of genes can change the structure of the PAH enzyme,
causing it to:
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Misfold or become unstable.
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Lose a significant amount of activity.
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Or not be productive at all.​
What happens if the PAH enzyme doesn’t break down phenylalanine?​
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1. If the substance phenylalanine is not converted, it accumulates in the blood, brain, and
other organs, leading to organ damage. High levels of phenylalanine accumulation are toxic
(especially to children and babies). The buildup of phenylalanine causes:
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Interference with brain development and function.
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Leads to intellectual disability, seizures, behavioural issues, and abnormal skin
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Damaged neurones.
pigmentation.
This may even lead to autistic or other underdeveloped behaviour in young children
due to brain damage.
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***This graph provides context of the prevalence of intellectual disability among adults with
phenylketonuria (PKU), diabetes mellitus (DM), and within the general population (GP).​
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(Research Gate (Deborah Bider), 2017) ​
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2. The human body cannot naturally produce tyrosine, so it’s essential that the body
somehow receive it for many metabolic and biological activities in the human body, such as :
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Helping in the making of neurotransmitters, such as : dopamine (hormone of
happiness), norepinephrine (hormone of maintaining alertness), epinephrine
(hormone for stress response), etc.
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Helping in the making of Thyroid hormones (important for metabolism)
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Melanin, the pigment in skin, eyes, and hair
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Tyrosine helps in the making of other proteins that are of importance
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Why can’t the reaction just happen slowly without PAH, as enzymes are only
there to ‘speed up’ reactions?​
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In most cases, enzymes function as biological catalysts - substances that ‘speed up’ metabolic
reactions, while the reactions themselves can still occur without them but at a significantly
slower rate. However, in the case of PKU, the absence or malfunction of the PAH enzyme
presents a far more serious issue. Although enzymes are not consumed during reactions,
they play a crucial role in lowering the activation energy required for those reactions to
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occur. Without PAH, the conversion of phenylalanine to tyrosine proceeds so slowly that it is
virtually non-existent in the human body. This is particularly dangerous because
phenylalanine accumulates in the body more rapidly than it can be broken down. Therefore,
even if the reaction technically continues at an extremely slow rate, it is nowhere near
efficient enough to prevent toxic buildup.​
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(National Institute of Health, 2012)
What are the contributing environmental and non-environmental factors to
genetic mutations in the PAH gene that lead to enzyme deficiency? ​
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In biological terms the gene mutation is generally caused by errors during DNA replication
or exposure to mutagens (agents, such as radiation or chemical substances).​
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Though environmental factors don’t generally cause the mutation itself, they can strongly
influence how the disease expresses in the body and how severe it affects the diagnosed
patient.​
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Environmental factors that affect the mutation directly include :
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Exposure to radiation: Radiation causes alterations in genes, which may affect the
gene sequencing of DNA molecules, meaning that
Exposure to mutagens: Mutagens are chemical substances that can
(Temperature (surroundings): temperature is an important factor, as it highly
influences enzyme activity; extremely high or low temperatures can slow down or
denature enzymes and their activity. - (Environmental temperature usually doesn’t
affect the scale that enzymes can get denatured)
Environmental factors that influence the severity of the disease may include:
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pH levels: pH levels are also very important factors in enzyme activity, as extremely
high or low pH levels can slow down or denature enzymes and their activity.
(Enzymes have optimal pHlevels - a level of acidity or alkalinity where they work
best).
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Bodily temperature: body temperature is a very important factor, as it can drastically
affect the severity. This is because it highly influences enzyme activity; extremely
high or low temperatures can slow down or denature enzymes. (Enzymes have
optimal temperatures—a temperature where they work best in the body—this is
usually around 37 degrees Celsius.)
Non-environmental factors include :
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Genetic inheritance: The primary cause of PKU is a mutation in the PAH gene,
passed down through an autosomal recessive inheritance pattern. Both biological
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parents must be carriers of the mutated gene for the child to develop PKU.
Spontaneous mutations: Although most cases are inherited, new spontaneous
mutations during DNA replication may also occur, albeit rarely. These can result in a
dysfunctional PAH enzyme even without a family history.
-​ Epigenetic changes: Modifications in gene expression that do not change the DNA
sequence itself, such as DNA methylation or histone modification, can potentially
influence how severely the PAH enzyme is expressed. These changes can interact
with environmental factors, amplifying disease effects.
(Mayo Clinic, 2022)
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How do people diagnosed with PKU live, and what precautions do they take
(diet)?​
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People with PKU can still live full and healthy lives, but only if they take the right
precautions from an early age. Since there’s no cure, the condition needs to be managed for
life. Most countries now test babies for PKU within the first few days of birth, which means
treatment can start early. The biggest thing people with PKU have to manage is their
diet—because phenylalanine is found in pretty much all high-protein foods like meat, dairy,
eggs, nuts, and even things like bread and pasta. This means they need to follow a very strict
low-protein diet and avoid artificial sweeteners, which also contains phenylalanine. They
also have regular blood tests to check how much phenylalanine is in their system, so it
doesn’t build up to dangerous levels.
To get the nutrients they miss from a low-protein diet, people with PKU usually take special
medical formulas—these give them the vitamins, minerals, and amino acids they need,
without any phenylalanine. Some people with milder PKU can take medications like
sapropterin, which can help their PAH enzyme work better—but this doesn’t work for
everyone. Even though the condition is serious, if people stick to their treatment—especially
during childhood and pregnancy—they can avoid brain damage and other long-term
problems. ​
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(Cleveland Clinic, 2025)
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PKU statistics : ​
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PKU is a rare condition—but rare doesn’t mean it doesn’t matter. According to the National
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PKU Alliance, it affects about 1 in every 10,000 to 15,000 births in the United States. In
Australia, around 1 in 10,000 babies are born with PKU, based on data from newborn
screening programs. ​
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The NPKUA also says that “over 50,000 people worldwide” are currently living with PKU.
What’s even more shocking is how dangerous it can be if it’s left untreated—“by the end of
the first year of life, irreversible brain damage can occur” (YourGenome, 2023). ​
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But the good news is, early diagnosis changes everything. Studies have shown that when
PKU is managed properly, “people with PKU can have IQs within the normal range and live
completely independent lives” (Cambridge, 2022). ​
(MDDA, 2025)​
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(NPKUA, 2020)
APA 7 Reference List
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INFORMATION
1.​ Better Health Channel. (n.d.). Phenylketonuria (PKU). Victorian State Government.
https://www.betterhealth.vic.gov.au/health/conditionsandtreatments/phenylketonuria-pku​
2.​ Mayo Clinic. (2024, March 12). Phenylketonuria (PKU): Symptoms & causes.
https://www.mayoclinic.org/diseases-conditions/phenylketonuria/symptoms-causes/syc-203
76302​
3.​ National Institutes of Health. (n.d.). What causes PKU? Eunice Kennedy Shriver National
Institute of Child Health and Human Development.
https://www.nichd.nih.gov/health/topics/pku/conditioninfo/causes​
4.​ Metabolic Dietary Disorders Association. (n.d.). What is PKU? Understanding a rare but
life‐changing condition.
https://mdda.org.au/what-is-pku-understanding-a-rare-but-life%E2%80%91changing-conditi
on/​
5.​ ScienceDirect. (n.d.). Phenylalanine hydroxylase.
https://www.sciencedirect.com/topics/biochemistry-genetics-and-molecular-biology/phenyl
alanine-hydroxylase​
6.​ Cambridge University Press. (n.d.). Cambridge science for Queensland 11 biology.
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https://www.cambridge.org/go/ereader/read/9781108970402/?groupId=0&bookid=2246&r
oot=anon#book/2246​
7.​ Genome Research Limited. (n.d.). Different types of mutations. YourGenome.
https://www.yourgenome.org/theme/different-types-of-mutations/​
8.​ National PKU Alliance. (n.d.). About PKU. https://www.npkua.org/about-pku/​
9.​ Fernandez, M. R., & Braverman, N. (2019). Phenylketonuria. In M. P. Adam, H. H. Ardinger, R.
A. Pagon, S. E. Wallace, L. J. H. Bean, K. Stephens, & A. Amemiya (Eds.), GeneReviews®.
University of Washington, Seattle. https://www.ncbi.nlm.nih.gov/books/NBK535378/​
10.​Mayo Clinic. (2022, September 1). Phenylketonuria (PKU).
https://www.mayoclinic.org/diseases-conditions/phenylketonuria/symptoms-causes/syc-203
76302​
11.​MedlinePlus. (2021, June 27). Phenylketonuria. U.S. National Library of Medicine.
https://medlineplus.gov/genetics/condition/phenylketonuria/​
12.​Better Health Channel. (2017, October). Phenylketonuria (PKU). Victorian Government,
Department of Health.
https://www.betterhealth.vic.gov.au/health/conditionsandtreatments/phenylketonuria-pku​
13.​Cleveland Clinic. (2021, October 4). Phenylketonuria (PKU).
https://my.clevelandclinic.org/health/diseases/17816-phenylketonuria​
14.​ScienceDirect. (n.d.). Phenylalanine.
https://www.sciencedirect.com/topics/neuroscience/phenylalanine​
15.​Weglage, J., Möller, H. E., Wiedermann, D., Feldmann, R., Ullrich, K., & Kölker, S. (2013).
Neuropsychiatric comorbidities in adults with phenylketonuria: A retrospective cohort study.
Orphanet Journal of Rare Diseases, 8(1), 1–7. https://doi.org/10.1186/1750-1172-8-61​
16.​van Spronsen, F. J., & Blau, N. (2013). Phenylketonuria: A challenge for researchers and
clinicians. Current Opinion in Neurology, 26(6), 577–582.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3664513/
STATISTICS
17.​van Wegberg, A. M. J., MacDonald, A., Ahring, K., Bélanger-Quintana, A., Blau, N., Bosch, A.
M., Campistol, J., Feillet, F., Giżewska, M., Huijbregts, S. C. J., de Laet, C., Leuzzi, V., Maillot, F.,
Muntau, A. C., Trefz, F., van Spronsen, F. J., & Walter, J. H. (2023). A guideline for the
diagnosis and management of phenylketonuria in Europe. PubMed.
https://pubmed.ncbi.nlm.nih.gov/37105048/
IMAGES
18.​Tan, J. (2020). Phenylalanine hydroxylase (PAH) reaction and Phenylketonuria (PKU) [Figure].
ResearchGate.
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https://www.researchgate.net/figure/Phenylalanine-hydroxylase-PAH-reaction-and-Phenylke
tonuria-PKU_fig1_342131784​
19.​RCSB Protein Data Bank. (2004, February). Phenylalanine hydroxylase (PAH).
https://pdb101.rcsb.org/motm/61​
20.​PDB‑101: RCSB Protein Data Bank. (n.d.). Phenylalanine hydroxylase (PAH) [Molecule of the
Month]. PDB‑101. https://pdb101.rcsb.org/motm/61​
21.​Retina Australia. (n.d.). Inheritance patterns. Retina Australia.
https://retinaaustralia.com.au/resources/inheritance‑patterns/
22.​
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Progress Log
Depth Study - 11 Biology, 2025
Date
Achieved this session
●​ Description of what was achieved by you and/or your group
●​ Sources used (links and other sources)
●​ Screenshots, images and/or photos of progress
What to
achieve
next
(“To do” list)
5/7/25
Trying to gain an initial understanding of the task :I was trying to
understand what exactly I was supposed to submit in the end so that I
could prepare for it in the given time.​
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TO DO: Decide on a disease.
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7/7/25
Me and my group finally decided on the disease we were going to do we had initially discussed it in the class before. But we finally decided on
PKU after research on which topic would be the most impressive and
high scoring.​
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TO DO : Plan ahead to meet in the Holidays
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9/7/25
Me and Sean met at Blacktown Library to discuss our plans for the
models and video; Kayden couldn’t make it due to an issue at his house.​
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(Kayden couldn’t communicate a lot with us because of him being in a
different class and not being able to meet)​
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TO DO : finish off initial research​
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EVIDENCE
19/7/25
We finished ourinitial research parts and were starting to write our
individual components.​
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TO DO : Finish off Individual component and start models.
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24/7/25
When we had time in class, we worked on our individual components
most of the time.​
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TO DO : Start models and group component​
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EVIDENCE
31/7/25
I went to Westpoint and procured the necessary materials for our models
($15).​
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TO DO : start the transcript and models
1/8/25
When we had time in class, we worked on our individual components
most of the time.​
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TO DO : Start models and group component
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4/8/25
We had time in class so I started writing the group transcript and had
finished off my individual component. (Kayden had initially written script but it wasn’t very effective - so I had to rewrite it (with telling the group
prior))​
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TO DO : Start the models and group component
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5/8/25
We stayed back at the learning centre and had finished the models.​
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TO DO : Start the filming
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6/8/25
We stayed back at the learning centre and I had finished the script
while Sean and Kayden were wrapping up the models.
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We did film ourselves but there was a buzzing noise.​
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TO DO : Re-film and edit. (For me).
7/8/25
We met in the library at recess to reshoot the video.​
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TO DO : Edit (My job)
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8/8/25
I submitted the group component at about 1 A.M (I had to stay up late to
check through the work and editing took a long time.)​
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I submitted the individual component at about 3:30 AM - I checked
through it and the guidelines to ensure that I had everything according to
the guidelines. (It’s still 3:10 now)​
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TO DO : NONE
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GROUP CONTRIBUTIONS
Abhinav Kondapavuloori
VIDEO PLANNING
VIDEO FILMING
Abhinav Kondapavuloori
VIDEO EDITING
Abhinav Kondapavuloori
MATERIAL PROCUREMENT
Abhinav Kondapavuloori
PAH ENZYME MODEL
Kayden Aranda
BRAIN - TOXICITY MODEL
Sean Healy
Abhinav Kondapavuloori
BLOOD VESSEL MODEL
Abhinav Kondapavuloori
DNA STRAND MODEL
Abhinav Kondpavuloori
SUBSTRATE - COMPLEX MODEL
- (GENERIC)
Abhinav Kondapavuloori
RESEARCH
Abhinav Kondapavuloori
Sean Healy
Kaden Aranda
SCHEDULING
Abhinav Kondapavuloori​
Sean Healy
STATISTICAL RESEARCH
Sean Healy​
Kaeden Aranda
GRAPHICAL DATA
Sean Healy
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Abhinav Kondapavuloori​
Proofreading by Sean and Kayden
TRANSCRIPT
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