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An introduction to metabolism. Totality of an organisms chemical reactions.

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Presentation on theme: "An introduction to metabolism. Totality of an organisms chemical reactions."— Presentation transcript:

1 An introduction to metabolism

2 Totality of an organisms chemical reactions

3 An introduction to metabolism Totality of an organisms chemical reactions The chemical factory

4 Key concepts An organism’s metabolism transforms matter and energy, according to the laws of thermodynamics The free energy change of a reaction tells us whether the reaction occurs spontaneously ATP powers cellular work by coupling endergonic and exergonic reactions Enzymes speed up chemical reactions Regulation of enzyme activity helps control metabolism

5 Matter review Something that has mass and occupies space Matter consists of atoms that are bound together to form molecules Atoms are never created or destroyed in biological systems (Conservation of matter) but molecules can be

6 Definition: Energy is the ability to do work First law of thermodynamics: Energy cannot be created or destroyed but, it can be converted to other forms Forms Energy review Kinetic: energy in motion Potential: stored energy

7 Definition: Energy is the ability to do work First law of thermodynamics: Energy cannot be created or destroyed but, it can be converted to other forms Forms Energy review Chemical energy Kinetic

8 Definition: Energy is the ability to do work First law of thermodynamics: Energy cannot be created or destroyed but, it can be converted to other forms Forms Energy review Heat and light Chemical energy

9 Definition: Energy is the ability to do work First law of thermodynamics: Energy cannot be created or destroyed but, it can be converted to other forms Second law of thermodynamics: –Some energy becomes unusable with every energy transfer –Another way to state this: every energy transfer increases entropy (a measure of disorder and randomness) –I.e. hot pan and cold sink Energy review

10 What does this have to do with metabolism?

11 Metabolism Metabolism involves metabolic pathways that change in matter and energy Begin with a specific molecule which is then altered in a series of defined steps. Each step is catalyzed by an enzyme.

12 Metabolism Metabolism involves metabolic pathways that change in matter and energy –Anabolic pathways build complicated molecules from simple molecules. They consume energy! –Catabolic pathways breakdown molecules. They release energy!

13 An organism’s metabolism transforms matter and energy, according to the laws of thermodynamics

14 The free energy change of a reaction tells us whether the reaction occurs spontaneously

15 The energy available to do work

16 The free energy change of a reaction tells us whether the reaction occurs spontaneously This means that the reaction does not require energy…it doesn’t necessarily happen fast though.

17 Free energy change Unstable systems have a high G, stable systems have a low G All systems will go to a more stable state…unless something prevents this from happening

18 Free energy change Unstable systems have a high G, stable systems have a low G All systems will go to a more stable state…unless something prevents this from happening

19 Free energy change Unstable systems have a high G, stable systems have a low G Change in free energy of a system is symbolized by ∆G ∆G=G final state - G initial state The ∆G is negative when the process involves a loss of free energy. This occurs spontaneously. All systems will go to a more stable state…unless something prevents this from happening Equilibrium is the maximum stability

20 Free energy change and chemical reactions Exergonic reaction Proceeds with a net release of energy ∆G is negative Occurs spontaneously Endergonic reaction Absorb free energy ∆G is positive Not spontaneous (requires energy) Reactants Energy Free energy Products Amount of energy released (∆G < 0) Progress of the reaction (a) Exergonic reaction: energy released Products Reactants Energy Free energy Amount of energy required (∆G > 0) (b) Endergonic reaction: energy required Progress of the reaction

21 The free energy change of a reaction tells us whether the reaction occurs spontaneously

22 ATP powers cellular work by coupling exergonic and endergonic reactions

23 Types of cellular work Chemical work (pushing of endergonic reactions) Transport work Mechanical work

24 Types of cellular work Chemical work (pushing of endergonic reactions) Transport work Mechanical work Cells accomplish all of these things by energy coupling- using an exergonic reaction to drive an endergonic one ATP is usually involved Adenine triphosphate Contains a ribose sugar, adenosine, and three phosphate groups Bonds with phosphate groups can be broken to release energy (generates ADP + Pi)

25 How ATP performs chemical work Typically ATP aids in the driving endergonic chemical reactions through phosphorylation –Transfers a phosphate group to the reactant –Reactant becomes unstable –Reactant reacts forming a new product Ammonia displaces the phosphate group, forming glutamine. P P Glu NH 3 NH 2 Glu i ADP + P ATP + + Glu ATP phosphorylates glutamic acid, making the amino acid less stable. Glu NH 3 NH 2 Glu + Glutamic acid Glutamine Ammonia ∆G = +3.4 kcal/mol + 1

26 How ATP performs transport and mechanical work (b) Mechanical work: ATP binds noncovalently to motor proteins, then is hydrolyzed Membrane protein P i ADP + P Solute Solute transported P i VesicleCytoskeletal track Motor protein Protein moved (a) Transport work: ATP phosphorylates transport proteins ATP

27 Regeneration of ATP P i ADP + Energy from catabolism (exergonic, energy-releasing processes) Energy for cellular work (endergonic, energy-consuming processes) ATP + H2OH2O

28 ATP powers cellular work by coupling exergonic and endergonic reactions

29 Enzymes speed up metabolic reactions by lowering energy barriers

30 A macromolecule, typically a protein, that speeds up a chemical reaction without being used up

31 Activation energy All chemical reactions involve bond formation and breaking Bonds need to be in an unstable (high free energy state) to change An initial investment in energy is required to destabilize bonds New bonds formed will be more stable (energy is released)

32 Activation energy Progress of the reaction Products Reactants ∆G < O Transition state Free energy EAEA DC BA D D C C B B A A Even in exergonic reactions, activation energy is a barrier

33 How do enzymes function? Substrate binds to the enzyme’s active site Substrate specificity is based on protein shape While they are bound the enzyme converts the reactant to the product After the product is created, the enzyme releases it and can catalyze another reaction Most metabolic reactions are reversible, the same enzyme can catalyze the reverse reaction Substrates Enzyme Products Enzyme-substrate complex 2

34 How does this interaction speed up the rate of a chemical reaction? Enzymes orient reactants properly for the reaction to occur Enzymes can stretch the substrate (causing unstable bonds) Enzymes can create micro environments The active site can participate directly in the chemical reaction Substrates Enzyme Products Enzyme-substrate complex 2

35 Remember, proteins are sensitive to environmental conditions Rate of reaction Optimal temperature for enzyme of thermophilic (heat-tolerant) bacteria Optimal temperature for typical human enzyme (a) Optimal temperature for two enzymes (b) Optimal pH for two enzymes Rate of reaction Optimal pH for pepsin (stomach enzyme) Optimal pH for trypsin (intestinal enzyme) Temperature (ºC) pH 54 3210 678910 0 20 40 80 60100

36 What other factors impact enzyme function? Cofactors-non-protein helpers aid catalytic activity –If organic called a coenzyme i.e. Catalase, an antioxidant that neutralizes free radicals in the cell, contains an iron atom which aids in bringing the substrate to the transition state

37 What other factors impact enzyme function? Inhibitors Competitive inhibitors bind to the enzyme’s active site Non-competitive inhibitors bind elsewhere on the molecule, but change the shape of the active site Can be reversible or irreversible (impacts can very) (a) Normal binding (c) Noncompetitive inhibition (b) Competitive inhibition Noncompetitive inhibitor Active site Competitive inhibitor Substrate Enzyme

38 Enzymes speed up metabolic reactions by lowering energy barriers

39 Regulation of enzyme activity helps control metabolism

40 Allosteric Cooperativity Positive and negative feedbacks

41 Regulation of enzyme activity helps control metabolism Cells can regulate biochemical pathways by Making more or less of an enzyme Regulating enzyme function –Cooperativity Substrate bind to the active site of one subunit of a multi sub-unit enzyme Amplifies the catalytic response –Allosteric regulation similar to non-competitive inhibition (molecules bind at an allosteric site to alter the shape of the active site) Can inhibit or stimulate enzyme function Allosteric enyzme with four subunits Active site (one of four) Regulatory site (one of four) Active form Activator Stabilized active form Oscillation Non- functional active site Inhibitor Inactive form Stabilized inactive form (a) Allosteric activators and inhibitors Substrate Inactive form Stabilized active form (b) Cooperativity: another type of allosteric activation

42 Regulation of enzyme activity helps control metabolism Feedback regulation Negative feedback  Excess D blocks a step D D D A B C Enzyme 1 Enzyme 2 Enzyme 3 D (a) Negative feedback W Enzyme 4 X Positive feedback Enzyme 5 Y + Enzyme 6 Excess Z stimulates a step Z Z Z Z (b) Positive feedback

43 Regulation of enzyme activity helps control metabolism

44 Key concepts An organism’s metabolism transforms matter and energy, according to the laws of thermodynamics The free energy change of a reaction tells us whether the reaction occurs spontaneously ATP powers cellular work by coupling endergonic and exergonic reactions Enzymes speed up chemical reactions Regulation of enzyme activity helps control metabolism

45 Concept map Water Hydrogen bonds High specific heat Cohesion

46 Water Hydrogen bonds High specific heatCohesion forms give water special properties including Concept map

47 Metabolism concept map Metabolism Metabolic pathway Enzyme inhibitor Enzymes Cooperativity Allosteric Feedback Chemical reaction anabolic Catabolic Metabolic regulation cell Endergonic Exergonic ATP


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