Topic 2: Enzymes, Proteins, and Chemical Reactions

Comprehensive vocabulary flashcards covering enzyme structure and function, mechanisms of reaction, protein types, environmental influences on enzyme activity (pH and temperature), and denaturation.

Enzyme

An organic catalyst made of protein that speeds up chemical reactions by lowering the activation energy required, without being consumed or permanently altered in the process.

Catalyst

A substance that increases the rate of a chemical reaction without undergoing any permanent chemical change itself.

Substrate

The specific molecule or reactant that an enzyme binds to and acts upon during a chemical reaction.

Active Site

The specific region on an enzyme where the substrate binds; its shape fits only one specific substance.

Enzyme-Substrate Complex

The temporary intermediate structure formed when a substrate molecule attaches to the active site of its specific enzyme.

Lock and Key Model

A model illustrating enzyme specificity, where the enzyme acts as a lock and the substrate acts as a key that fits precisely into the active site.

Denaturation

A permanent, irreversible change in the shape of a protein or enzyme caused by extreme temperature or pH, rendering it ineffective because the substrate can no longer fit.

Activation Energy

The minimum amount of energy needed to start a chemical reaction, which enzymes lower to allow reactions to occur faster.

Optimal Temperature

The temperature at which an enzyme functions at its highest level of activity and achieves the greatest rate of reaction (e.g., $37\,^{\circ}\text{C}$ or $98.6\,^{\circ}\text{F}$ for human enzymes).

Optimal pH

The specific pH level at which a particular enzyme works most effectively before being denatured by excessive acidity or alkalinity.

Dehydration Synthesis

A chemical reaction in which two substrate molecules combine to form one product and release a molecule of water ($H_2O$).

Hydrolysis (Digestion)

A breakdown reaction in which one substrate combines with water ($H_2O$) to split into two separate products.

Pepsin

A stomach enzyme that digests proteins and operates optimally in a highly acidic environment with a pH between $1.0$ and $3.0$.

Trypsin

A protein-digesting enzyme located in the small intestine that functions optimally at a slightly basic pH of $7.5\text{--}9.0$.

Ptyalin

An enzyme secreted in the mouth that digests carbohydrates, functioning optimally at a temperature of $36.7\text{--}37.0\,^{\circ}\text{C}$ and a pH of $6.5\text{--}7.0$.

Hormones

Protein-based chemical messengers that travel through the body to regulate physiological processes (such as insulin and adrenaline).

Cell Receptors

Proteins embedded in the cell membrane that receive and transmit signals across the membrane, allowing cells to communicate with one another.

Structural Proteins

Proteins that provide physical support, structure, and shape to cells and tissues (such as collagen and keratin).

Antibodies

Proteins of the immune system that identify, target, and attack foreign invaders to defend the body.

Essential Amino Acids

The 8 specific types of amino acids (out of 20 total types needed to build proteins) that the human body cannot synthesize on its own and must obtain through the diet.

Acid

A chemical compound that donates hydrogen ions ($H^+$) to a solution, corresponding to values between 0 and 6 on the pH scale.

Base (Alkaline)

A chemical compound that accepts hydrogen ions ($H^+$) and removes them from solution, often by donating hydroxide ions ($OH^-$), corresponding to values between 8 and 14 on the pH scale.

pH Scale

A logarithmic measurement scale changing in increments of 10 used to indicate the concentration of hydrogen ions in a solution, where a value of 7 represents a neutral solution.