Metabolism and Chemical Reactions Quiz

Metabolism

• Metabolism is all the chemical reactions within each cell of an organism
• It provides energy for life processes and creates key molecules
• Chemical reactions involve breaking and forming bonds between substances
• Reactions absorb or release energy; breaking a bond absorbs energy, forming a bond releases energy
• The law of conservation of energy applies; energy isn't lost, it changes form (e.g. heat, light)

Metabolic Reactions

• Biochemical reactions are either catabolic or anabolic
• Catabolic reactions break down larger molecules into simpler compounds, releasing energy (exergonic)
• Anabolic reactions build larger molecules from smaller ones, consuming energy (endergonic)
• All reactions require activation energy to start — the minimum energy needed for a reaction to occur

Chemical Reactions

• Reactants are the substances changed during a chemical reaction
• Products are the substances formed during a chemical reaction
• Reactions can either absorb (endothermic) or release (exothermic) energy

Types of Reactions

• Endothermic reactions absorb energy (e.g., photosynthesis—light energy is stored as chemical energy in sugar)
• Exothermic reactions release energy (e.g., cellular respiration—chemical energy in sugar is converted to chemical energy released as ATP)

Enzymes

• Metabolic reactions are controlled by enzymes—mostly proteins
• Enzymes speed up biochemical reactions by lowering activation energy
• They act as catalysts, speeding up reactions without being changed themselves
• Enzymes are specific, binding to specific reactants (substrates) at their active site
• Enzymes are not changed during the reaction and can be reused
• Enzymes are crucial for regulating life processes in all organisms. Binding fits into an active site and then creates an induced fit within the enzyme and substrate

Enzyme Specificity and Function

• Enzymes have very specific active sites that can only fit specific substrates
• Once a substrate connects, a tighter binding (induced fit) occurs
• Enzymes can break bonds in substrates to form new products
• Enzymes can form bonds between substrates to form new products

Enzyme Denaturation

• An enzyme's active site can be deformed, losing its shape and biological activity, due to environmental changes like extreme pH, temperature, or ion strength
• Some enzymes can be renatured, but not always

Factors Affecting Reaction Rate

• Temperature—higher temperatures increase the rate of reaction as molecules move faster and collide more often
• pH—enzymes work best at specific pH values, and changes in pH can affect reaction speed
• Substrate concentration—higher substrate concentration leads to faster reactions due to increased collisions
• Catalysts (enzymes)—lower activation energy needed for reactions to start, thereby increasing the reaction rate
• Competitive inhibitors—slow down reactions by competing with substrates for the active site on the enzyme