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Biology IB HL - D1 Human Nutrition Part 2

Biology25 CardsCreated about 1 month ago

This flashcard deck covers key concepts related to human nutrition, focusing on genetic conditions like PKU, essential fatty acids, and the transport of fats and cholesterol in the body.

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What is PKU?

Phenylketonuria (PKU) is a genetic condition that results in the impaired metabolism of the amino acid phenylalanine
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Key Terms

Term
Definition
What is PKU?
Phenylketonuria (PKU) is a genetic condition that results in the impaired metabolism of the amino acid phenylalanine
What does PKU affect regarding genetics?
It is an autosomal recessive disease caused by a mutation to the gene encoding the enzyme phenylalanine hydroxylase
What is the typical role of PAH?
Phenylalanine hydroxylase (PAH) normally converts excess phenylalanine within the body into tyrosine
What happens as a result of the lack of PAH?
In people with PKU, the excess phenylalanine is instead converted into phenylpyruvate (also known as phenylketone)
What happens when phenylalanine is constantly being converted into phenylketone?
This results in a toxic build up of phenylketone in the blood and urine (hence phenylketonuria)
What can untreated PKU lead to?
Untreated PKU can lead to brain damage and mental retardation, as well as other serious medical problems
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Biology IB HL - D1 Human Nutrition Part 2
TermDefinition
What is PKU?
Phenylketonuria (PKU) is a genetic condition that results in the impaired metabolism of the amino acid phenylalanine
What does PKU affect regarding genetics?
It is an autosomal recessive disease caused by a mutation to the gene encoding the enzyme phenylalanine hydroxylase
What is the typical role of PAH?
Phenylalanine hydroxylase (PAH) normally converts excess phenylalanine within the body into tyrosine
What happens as a result of the lack of PAH?
In people with PKU, the excess phenylalanine is instead converted into phenylpyruvate (also known as phenylketone)
What happens when phenylalanine is constantly being converted into phenylketone?
This results in a toxic build up of phenylketone in the blood and urine (hence phenylketonuria)
What can untreated PKU lead to?
Untreated PKU can lead to brain damage and mental retardation, as well as other serious medical problems
How are infants with PKU at birth?
Infants with PKU are normal at birth because the mother is able to break down phenylalanine during pregnancy
How is PKU diagnosed?
Diagnosis of PKU is made by a simple blood test for elevated phenylalanine levels shortly after birth
How is PKU treated?
PKU is treated by enforcing a strict diet that restricts the intake of phenylalanine to prevent its build up within the body
What does a PKU diet contain?
This low-protein diet should include certain types of fruits, grains, vegetables and special formula milk
What should a PKU diet be supplemented with?
This diet should be supplemented with a medical formula that contains precise quantities of essential amino acids
Is a person able to live normally with PKU?
Patients who are diagnosed early and maintain this strict diet can have a normal life span without damaging symptoms
Why are most fatty acids non-essential? What are the exceptions (general)?
Humans can synthesise most fatty acids from carbohydrates, but two (cis)-polyunsaturated fatty acids are considered essential
What are the 2 essential fatty acids?
Alpha-linolenic acid (an omega-3 fatty acid) and linoleic acid (an omega-6 fatty acid) cannot be synthesised by the body
Why are these 2 fatty acids essential?
This is because humans lack the enzyme required to introduce double bonds at the required position of the carbon chain
What are essential fatty acids used for?
Essential fatty acids are modified by the body to make important lipid-based compounds (such as signalling molecules)
What is linked to a deficiency of essential fatty acids?
There is evidence to suggest dietary deficiencies of these fatty acids may be linked to impaired brain development (e.g. depression) and altered maintenance of cardiac tissue (e.g. abnormal heart function) – although this evidence is contested
What are foods rich in essential fatty acids?
Foods rich in essential fatty acids (omega-3 and omega-6) include fish, leafy vegetables and walnuts
How are fats and cholesterol transported?
Fats and cholesterol cannot dissolve in the bloodstream and so are packaged with proteins (to form lipoproteins) for transport
What are LDLs?
Low density lipoproteins (LDLs) carry cholesterol from the liver to the body (hence raise blood cholesterol levels)
What are HDLs?
High density lipoproteins (HDLs) carry excess cholesterol back to the liver for disposal (hence lower blood cholesterol levels)
What does the mix of fatty acids consumed affect?
The mix of fatty acids consumed as part of a diet directly influences the levels of cholesterol in the bloodstream:
How do saturated fatty acids affect the levels of cholesterol in the bloodstream?
Saturated fats increase LDL levels within the body, raising blood cholesterol levels
How do trans fats affect the levels of cholesterol in the bloodstream?
Trans fats increase LDL levels and lower HDL levels, significantly raising blood cholesterol levels
How do Cis-polyunsaturated fats affect the levels of cholesterol in the bloodstream?
Cis-polyunsaturated fats raise HDL levels, lowering blood cholesterol levels