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metabolism and enzymes
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Chapter 4, Metabolism
Section 1, Chapter 4
Cellular Metabolism
metabolism is the sum of all reactions in the body
AnabolismIn anabolic reactions energy is used to synthesize large molecules from smaller molecules.
Anabolic reactions create materials for growth and repair.
In catabolic reactions large molecules are decomposed into smaller molecules
Catabolic reactions release energy for cellular use
Catabolism
metabolic reactions are of two types
Amino acids are joined by dehydration synthesis
Dehydration SynthesisDehydration synthesis is a type of anabolic reaction.
triglycerides, polysaccharides, and proteins are synthesized through dehydration synthesis
A molecule of water is released from dehydration synthesis.
Dehydration Synthesis
Synthesizes
polysaccharides from monosaccharides
proteins from amino acids
nucleic acids from nucleotides
fats by joining fatty acids to glycerol
dehydration synthesis
Hydrolysis
hydrolysis is the reverse of dehydration synthesis
water is used to break apart molecules
hydrolysis releases energy from chemical bonds
hydrolysis
HydrolysisDecomposes Polysaccharides into monosaccharides & disaccharides
Decomposes proteins into amino acids
Decomposes Fats into fatty acids & glycerol
Decomposes Nucleic Acids into nucleotides
The critical amount of energy required for a reaction to occur is called the activation energy.
Enzymes are biological catalystsThey greatly reduce the activation energy required to start a reaction.
A substrate is the target molecule of an enzyme
Characteristics of enzymes
Most enzymes are Proteins
Enzymes lower the activation energy of a reaction
Enzymes catalyze reactions – they increase the rate of reactions, but are not consumed by the reaction
Enzymes are specific to one substrate.
Examples of enzymes:Lipase: decomposes lipidsProtease: decomposes proteinsNuclease: decomposes nucleic acidsATP Synthase: synthesizes ATP molecules
Enzyme NamesEnzymes are named for substrate they act upon and their name usually ends with _____ase.
The Active site of an enzyme is the region that binds to the substrate
The enzyme temporarily binds to the substrate forming an Enzyme-Substrate Complex
The Enzyme releases the product and enzyme is reused for a new reaction.
Enzymes
The rate of a reaction is limited by:
1. The concentration of substrate
2. The concentration of enzyme
3. The efficiency of enzymesSome enzymes handle 2-3 molecules per secondOther enzymes handle thousands per second
Rate of enzyme-catalyzed reactions
Example: The catabolic pathway for the breakdown of glucose is highly complex.
Metabolic PathwaysA metabolic pathway is a complex series of reactions leading to a product
Metabolic Pathways are controlled by several enzymes
The product of each reaction becomes the substrate of next reaction.
Each step requires its own enzyme
The least efficient enzyme is the “Rate-Limiting Enzyme” Rate-limiting enzyme is usually first in sequence
• Enzyme A = Rate-limiting Enzyme
Metabolic Pathways
Negative feedback prevents too much product from being produced.
The product of the metabolic pathway often inhibits the rate-limiting enzyme.
Negative Feedback in Metabolic Pathway
Cofactorsubstance that increases the efficiency of an enzyme
Cofactors include ions (zinc, iron, copper) and coenzymes
Coenzymes are organic cofactors Coenzymes include Vitamins (Vitamin A, B, D)
Reusable – required in small amounts
Vitamins are essential organic molecules that humans cannot synthesize, so they must come from diet
Many vitamins are coenzymes
Vitamins can function repeatedly, so can be used in small amounts.
Example: Coenzyme A
Energy: is the capacity to change something, or ability to do work.
Common forms of energy: HeatLightSoundChemical energyMechanical energyElectrical energy
Energy for Metabolic Reactions
Energy cannot be created or destroyed, but it may be transferred from one form to another.
Fuel (chemical energy) +
Oxygen = Kinetic Energy + CO2 + H2O
example of energy transfer: combustion engine
The combustion of fuel converts chemical energy in the gasoline into kinetic energy, heat, sound. Water and CO2 are produced as waste.
Cellular Respiration
Cell Respiration is the transfer of energy from food molecules into a form the cells can use
Energy from foods such as glucose is used to make ATP for the cell.
End of Section 1, Chapter 4
Reaction of Cell Respiration
Initial fuel or energy source
ATP = Energy currency for cells
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