3.16
Introduction to Chemical Reactions
All chemical reactions begin with a reactant, the general term for one or more substances entering the reaction. Sodium and chloride ions, for example…
A chemical reaction is a process where atoms in one or more substances, known as reactants, change their arrangement by breaking their chemical bonds and forming new bonds to create the products.
Reactions which result in a net release of energy are exergonic, while endergonic reactions are net absorbers of energy.
The biochemical reactions occurring in the human body are categorized as either synthesis or anabolic, such as protein synthesis, decomposition, or catabolic, such as the breakdown of polysaccharides into simple sugars, or exchange reactions, such as the transfer of ATP's phosphate to glucose to form glucose-phosphate.
Many biochemical reactions use enzymes as catalysts to speed up the reaction.
All biochemical reactions progress towards equilibrium — a state where no net change in the concentrations of reactants and products occurs because the forward and reverse reactions are happening at the same rate.
The biochemical reactions provide energy to maintain homeostasis and perform essential functions such as growth and repair.
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Q1: What happens to atoms during a chemical reaction?
During a chemical reaction, atoms in reactants break their chemical bonds and rearrange to form new bonds, creating products. This process involves the rearrangement of matter rather than its creation or destruction, following the law of conservation of mass. The atoms present in reactants remain present in products, just in different combinations.
Q2: How do exergonic and endergonic reactions differ in energy?
Exergonic reactions release energy as a net result, while endergonic reactions absorb energy. Both types occur in the human body to maintain homeostasis and support essential functions like growth and repair. The direction of energy flow determines whether a reaction is exergonic or endergonic.
Q3: What are the main categories of biochemical reactions in the human body?
Biochemical reactions fall into three categories: synthesis or anabolic reactions like protein synthesis, decomposition or catabolic reactions like polysaccharide breakdown, and exchange reactions like phosphate transfer to glucose. These types of chemical reactions anabolic and catabolic reactions provide energy and building blocks for maintaining homeostasis and performing vital functions.
Q4: Why do enzymes matter in biochemical reactions?
Enzymes act as catalysts in biochemical reactions, speeding up the rate at which reactions occur without being consumed themselves. This acceleration is crucial for maintaining the rapid metabolic processes necessary for life. Enzymes enable reactions to proceed efficiently at body temperature and pH.
Q5: What is chemical equilibrium and why does it matter?
Chemical equilibrium occurs when forward and reverse reactions proceed at equal rates, resulting in constant concentrations of reactants and products. In biological systems, true equilibrium is rare because reactants and products continuously change as one reaction's product becomes another's reactant. This dynamic state is essential for maintaining homeostasis in blood and other body systems.
Q6: What is activation energy and how does it start a reaction?
Activation energy is the minimum energy required to break chemical bonds in reactants and initiate a reaction. Reactants must collide with sufficient force and precision to overcome this energy barrier. Temperature and concentration of reactants influence whether molecules possess enough kinetic energy to meet activation energy requirements.
Q7: How do reversible reactions differ from irreversible ones?
Reversible reactions can proceed in both forward and reverse directions, while irreversible reactions proceed primarily in one direction. In biological systems, reactions like the carbonic acid-bicarbonate equilibrium in blood are reversible but driven toward products when one product leaves the system, such as carbon dioxide during exhalation. This directional shift maintains homeostasis.