enzymes and genetics

What are enzymes?

Biological catalysts, primarily proteins, that speed up the rate of biochemical reactions without being consumed in the process.

What is the primary function of an enzyme?

To lower the activation energy of a specific biochemical reaction, thereby increasing its rate.

Describe enzyme specificity.

Enzymes typically catalyze only one or a few very specific reactions, often binding to a particular substrate at their active site, as explained by the "lock and key" or "induced fit" model.

List three factors that can affect enzyme activity.

1. Temperature (optimal temperature for maximum activity)
2. pH (optimal pH for maximum activity)
3. Substrate concentration (reaction rate increases with concentration until saturation)
4. Presence of inhibitors or activators.

What happens to an enzyme if it is exposed to extreme temperatures or pH?

It can denature, meaning its 3D structure (especially the active site) changes, leading to a loss of its catalytic function.

What is a gene?

A segment of DNA that carries the genetic information to make a specific protein or RNA molecule, determining a particular trait or characteristic.

What is the structure and primary role of DNA?

DNA (Deoxyribonucleic Acid) is a double-helix polymer composed of nucleotides (deoxyribose sugar, phosphate group, and one of four nitrogenous bases: Adenine, Guanine, Cytosine, Thymine). Its primary role is to store and transmit genetic information.

How does RNA differ from DNA, and what are its main types?

RNA (Ribonucleic Acid) is typically single-stranded, contains ribose sugar instead of deoxyribose, and Uracil (U) instead of Thymine (T). Main types include messenger RNA (mRNA), ribosomal RNA (rRNA), and transfer RNA (tRNA), all involved in protein synthesis.

Explain the Central Dogma of Molecular Biology.

It describes the flow of genetic information: DNA is transcribed into RNA, and RNA is then translated into protein. (DNA \to RNA \to Protein)

Define 'genotype' and 'phenotype'.

• Genotype: The genetic makeup of an organism, referring to the specific set of alleles an individual possesses for a particular trait.
• Phenotype: The observable physical or biochemical characteristics of an organism, resulting from the interaction of its genotype with the environment.

A rare genetic mutation changes a single amino acid in an enzyme's active site. How might this affect the enzyme's function and the overall reaction it catalyzes?

• Enzyme Function: The mutation could alter the shape or chemical properties of the active site, potentially reducing or eliminating the enzyme's ability to bind its substrate or catalyze the reaction efficiently.
• Overall Reaction: The reaction rate would likely decrease significantly, or the reaction might not occur at all, potentially leading to a buildup of substrate or a deficiency of product, with downstream metabolic consequences.

Phenylketonuria (PKU) is a genetic disorder where individuals cannot properly metabolize phenylalanine due to a defective enzyme, phenylalanine hydroxylase. Explain the genetic basis and how enzyme deficiency leads to health problems.

• Genetic Basis: PKU is inherited in an autosomal recessive pattern, meaning individuals must inherit two copies of the defective gene (one from each parent) to express the disorder. The defective gene carries incorrect instructions for producing the phenylalanine hydroxylase enzyme.
• Enzyme Deficiency & Health Problems: Without a functional enzyme, phenylalanine (an amino acid) accumulates in the body to toxic levels, especially in the brain, leading to severe intellectual disability and other neurological problems if not treated with a specialized diet.

Imagine a plant species has a gene that codes for an enzyme crucial for producing a red pigment in its flowers. If this plant is grown in unusually cold temperatures, its flowers might appear white. Explain this observation by relating enzyme activity, genes, and environment.

• Genetic Basis: The plant possesses the gene for the red pigment enzyme, so its genotype allows for red flowers.
• Enzyme Activity & Environment: However, enzymes have optimal temperatures for activity. Extreme cold might cause the red pigment-producing enzyme to become denatured or significantly reduce its activity.
• Phenotype: Consequently, even though the gene is present, the enzyme cannot function effectively to produce the red pigment, resulting in a white flower phenotype under these environmental conditions. This demonstrates how phenotype is a product of both genotype and environment.