Topic 2: Exchange of Nutrients and Wastes

How are metabolic processes (digestion) controlled and regulated by enzymes?

Enzymes act as biological catalysts, speeding up chemical reactions by lowering the activation energy required to speed up breakdown of larger molecules (proteins, fats, carbohydrates) into smaller components.

Describe the structure of enzymes.

Enzymes are protein molecules made of amino acids folded into a unique 3D structure to create active sites for specific substrate binding.

Describe the function of enzymes, including role of active site.

Enzymes catalyse reactions by binding to substrates (reactant) at their active sites, allowing for specific interactions that lower activation energy and increase reaction rates, ultimately transforming substrates into products.

Compare the induced-fit and lock-and-key models of enzyme functions.

The induced-fit model suggests that the active site of an enzyme changes shape to accommodate the substrate, while the lock-and-key model posits that the enzyme's active site is a perfect fit for a specific substrate, allowing for easy binding.

Explain how enzyme activity is affected by temperature

With increased temperature, increased enzyme activity occurs (increased substrate and enzyme collisions). This occurs until optimum enzyme temperature (max enzyme activity) then if temperature continues rising, enzyme denatures by changing its active site structure, not allowing the substrate to bind anymore.

Explain how enzyme activity is affected by pH

Enzymes denature at extreme pH and have low activity at low pH. Optimum pH is where rate of enzyme reaction is the highest.

Explain how enzyme activity is affected by presence of inhibitors

Inhibitors are molecules that decrease enzyme activity by binding to the enzyme and preventing substrate binding, either by blocking the active site permanently (non-competitive) or altering the enzyme's shape and competing with normal substrate (competitive).

Explain how enzyme activity is affected by substrate concentration

As substrate concentration increases, the rate of enzyme activity also increases, up to a point where all active sites are occupied (maximum limiting value). Beyond this saturation point, rate of enzyme action plateaus.

Describe the role of amylase in chemical digestion

Amylase is an enzyme that catalyzes the breakdown of starches into simple sugars during the process of chemical digestion. Produced in the salivary glands in mouth, it converts starch to maltose (sugars).

Describe role of protease in chemical digestion

Protease is an enzyme that catalyzes the breakdown of proteins into amino acids during chemical digestion. Produced in the stomach, pepsin begins chemical breakdown of proteins.

Describe role of lipase in chemical digestion

Lipase is an enzyme that catalyzes the breakdown of fats and lipids into fatty acids and glycerol during chemical digestion. It is primarily secreted by the pancreas and acts in the small intestine by breaking down fats in foods to be absorbed by intestines.

Explain how structural features of exchange surfaces in the digestive and cirulatory systems of mammals allow for efficient nutrient exchange.

Large surface area provided by villi and microvilli in the intestines, thin barriers that minimise diffusion distance, and rich blood supply that enhances transport of absorbed nutrients are essential features for efficient nutrient exchange.

What is catabolism?

Metabolic pathways that break down larger molecules into smaller ones, releasing energy (carbohydrates to glucose).

What is anabolism?

Metabolic pathways that build larger molecules from smaller ones, using energy.

Explain how ATP allows energy from catabolic reactions to be used in anabolic reactions.

During a catabolic reaction, energy is released and captured in the form of ATP, which can then be utilized to fuel anabolic reactions.

What is aerobic respiration?

The process by which organisms release energy by converting glucose and oxygen into energy, producing carbon dioxide, water and ATP.

What is anaerobic respiration?

The process of generating energy without oxygen, typically resulting in the conversion of glucose into energy, carbon dioxide, and various byproducts such as lactic acid or alcohol.

Compare aerobic and anaerobic respiration.

Aerobic respiration requires oxygen and produces more ATP and byproducts like carbon dioxide and water, while anaerobic respiration occurs without oxygen, yielding less ATP and byproducts such as lactic acid or alcohol.