Metabolism

Cell Energetics Cell do three main kinds of work Cell do three main kinds of work Mechanical – move themselves Mechanical – move themselves Transport – move something else Transport – move something else Chemical – convert stuff to other stuff Chemical – convert stuff to other stuff Work requires energy Work requires energy Where does the energy come from and how do cells use it? Where does the energy come from and how do cells use it?

Cell Energetics Energy is ______ Energy is ______ Metabolism Metabolism 2 types of metabolism 2 types of metabolism Two forms of energy Two forms of energy How do cells use the 2 forms How do cells use the 2 forms 2 Laws of Thermodynamics 2 Laws of Thermodynamics Entropy Entropy 2 types of reactions 2 types of reactions

Cell Energetics Metabolism = total of all the chemical reactions taking place in an organism

Metabolism Anabolism = ‘ build up’ processes; ‘consume’ (store) energy by assembling macromolecules Anabolism = ‘ build up’ processes; ‘consume’ (store) energy by assembling macromolecules Photosynthesis Photosynthesis Catabolism = ‘break down’ reactions; release energy by breaking down (lyse) molecules Catabolism = ‘break down’ reactions; release energy by breaking down (lyse) molecules Digestion Digestion

Energy Energy – the ability to do work Energy – the ability to do work Potential = capacity to do work (move something); due to position or stored (chemical energy; glucose, glycogen) Potential = capacity to do work (move something); due to position or stored (chemical energy; glucose, glycogen) Kinetic = motion Kinetic = motion Equilibrium = energy runs out Equilibrium = energy runs out

Kinetic and potential energy

What does the types of energy have to do with biology?

Thermodynamics 1 st Law – energy cannot be created nor destroyed 1 st Law – energy cannot be created nor destroyed Energy can be transformed Energy can be transformed 2 nd Law – ‘Law of Entropy’ whenever energy is transformed, some of it becomes ‘unusable’ 2 nd Law – ‘Law of Entropy’ whenever energy is transformed, some of it becomes ‘unusable’ Entropy - amount of usable energy decreases each time it is used Entropy - amount of usable energy decreases each time it is used ‘Lost’ as heat ‘Lost’ as heat Energy is running down, universe is tending towards disorder Energy is running down, universe is tending towards disorder

Biological Order and Disorder Organisms are open systems Organisms are open systems Use energy to maintain order and organization Use energy to maintain order and organization Trade organization for heat (increase entropy in the environment) Trade organization for heat (increase entropy in the environment)

Metabolism: Reactions Two types of reactions: Two types of reactions: Exergonic, endergonic Exergonic, endergonic Exergonic reaction - release of free energy Exergonic reaction - release of free energy Less stable, more work Less stable, more work Fire, respiration Fire, respiration

Metabolism: Reactions Endergonic reaction - energy is absorbed/stored Endergonic reaction - energy is absorbed/stored Photosynthesis Photosynthesis

Chemical Reactions Equilibrium is eventually reached in closed systems Equilibrium is eventually reached in closed systems Reduced free energy Reduced free energy No work is done No work is done You’re dead! You’re dead!

What cells do..

Review What are the 2 forms of energy? What are the 2 forms of energy? _____ is the ability to do work _____ is the ability to do work Energy is lost in chemical reactions as __ Energy is lost in chemical reactions as __ A reaction that stores/absorbs energy is said to be _____ A reaction that stores/absorbs energy is said to be _____ A reaction that releases energy is _____ A reaction that releases energy is _____ The total of all chemical reactions in an organism is called ____ The total of all chemical reactions in an organism is called ____

Coupled Reactions Living systems use coupled reactions Living systems use coupled reactions Endergonic reactions are linked (coupled) with exergonic reactions Endergonic reactions are linked (coupled) with exergonic reactions Energy from an exergonic reaction (respiration) is stored in chemical bonds Energy from an exergonic reaction (respiration) is stored in chemical bonds

Coupled Reactions ATP – Adenosine triphosphate ATP – Adenosine triphosphate Cyclical Cyclical Catabolic pathways drive the regeneration of ATP from ADP and phosphate Catabolic pathways drive the regeneration of ATP from ADP and phosphate Controlled by enzymes Controlled by enzymes

Uses of Energy Mechanical - moving of cilia/flagella, muscle, cytoplasm, chromosomes (mitosis), mousetrap Mechanical - moving of cilia/flagella, muscle, cytoplasm, chromosomes (mitosis), mousetrap Transport - H+ ‘pump’, receptors Transport - H+ ‘pump’, receptors Chemical – polymerization Chemical – polymerization Bioluminescence Bioluminescence

Enzymes control metabolism – If enzymes are present, reactions take place, if not, they don’t. Enzymes speed up reactions by lowering activation energyEnzymes control metabolism – If enzymes are present, reactions take place, if not, they don’t. Enzymes speed up reactions by lowering activation energy

Biological catalysts Biological catalysts Accelerate a reaction without being changed Accelerate a reaction without being changed Proteins (700) Proteins (700) Catabolic or anabolic reactions Catabolic or anabolic reactions Enzymes

Enzymes All chemical reactions require activation energy All chemical reactions require activation energy Activation energy (E A ) - the initial amount of energy needed to start a chemical reaction Activation energy (E A ) - the initial amount of energy needed to start a chemical reaction Transition state = reactants have absorbed energy Transition state = reactants have absorbed energy Have become unstable Have become unstable Reaction takes place Reaction takes place

Enzymes Some reactions occur spontaneously due to heat from the environment (rust) Some reactions occur spontaneously due to heat from the environment (rust) Cellular T needs to remain low Cellular T needs to remain low Metabolism is too slow at low T Metabolism is too slow at low T Starch to glucose Starch to glucose Enzymes used to reduce activation energy (metabolism at lower T) Enzymes used to reduce activation energy (metabolism at lower T)

Enzymes Substrate = substance enzyme acts on Substrate = substance enzyme acts on Active site = area on the enzyme where substrate binds Active site = area on the enzyme where substrate binds Verryyy specific Verryyy specific Groove, pocket = 3d shape Groove, pocket = 3d shape

Enzymes Lock and key mechanism Lock and key mechanism Induced Fit = enzyme may change shape to allow better reaction on substrate Induced Fit = enzyme may change shape to allow better reaction on substrate

Factors That Affect Enzyme Activity Temperature Temperature pH pH Inorganic salts – Inorganic salts – Disrupt H bonds, ionic bonds, hydrophobic interactions Disrupt H bonds, ionic bonds, hydrophobic interactions Cofactors Cofactors Inhibitors Inhibitors

Temperature and pH affect enzyme activity

Cofactors Cofactors - nonprotein enzyme helpers Cofactors - nonprotein enzyme helpers Metals – Fe, Zn, Cu Metals – Fe, Zn, Cu Coenzymes - organic cofactors Coenzymes - organic cofactors Vitamins Vitamins

Inhibitors = substances that inhibit the actions of enzymes (2 kinds:) Inhibitors = substances that inhibit the actions of enzymes (2 kinds:) Competitive inhibitors Competitive inhibitors Noncompetitive inhibitors Noncompetitive inhibitors Enzymes

Competitive inhibitors - resemble substrate, block active site Neurotoxin, Disulfiram

Noncompetitive inhibitors - causes enzyme to change shape Noncompetitive inhibitors - causes enzyme to change shape Destroys conformation (active site) Destroys conformation (active site) DDT, nerve gas (DSF) DDT, nerve gas (DSF) May be allosteric regulation May be allosteric regulation Enzymes

Allosteric Regulation of Enzymes Allosteric regulation - a protein’s function at one site is affected by binding of a regulatory molecule at another site Allosteric regulation - a protein’s function at one site is affected by binding of a regulatory molecule at another site Receptor site located away from the active site (quatenary structure) Receptor site located away from the active site (quatenary structure) Allosteric site has to be activated, (may be inhibited) Allosteric site has to be activated, (may be inhibited)

Allosteric activator

Allosteric inhibitor

Cooperativity - one substrate molecule can activate all other subunits of an enzyme Cooperativity - one substrate molecule can activate all other subunits of an enzyme Induced fit Induced fit Only requires a small concentration of substrate to activate enzyme Only requires a small concentration of substrate to activate enzyme Enzymes

Enzyme Activity Helps Control Metabolism A cell’s metabolic pathways must be tightly regulated A cell’s metabolic pathways must be tightly regulated DNA codes for proteins (enzymes) DNA codes for proteins (enzymes) Amount of enzyme can determine rate of reaction Amount of enzyme can determine rate of reaction Feedback Inhibition - end product of the pathway inhibits the pathway Feedback Inhibition - end product of the pathway inhibits the pathway

Regulation Metabolic pathways – series of enzymes creates small steps to a final product Metabolic pathways – series of enzymes creates small steps to a final product Controlling the enzymes (activity or production) controls the pathway and product(s) Controlling the enzymes (activity or production) controls the pathway and product(s)

Feedback Inhibition Final product of the pathway shuts off the pathway Final product of the pathway shuts off the pathway Feedback inhibition prevents cells from wasting resources Feedback inhibition prevents cells from wasting resources “don’t need gas if you don’t have a car.” “don’t need gas if you don’t have a car.” Isoleucine – allosteric inhibitor