Lecture 5 Energy and Enzymes Flashcards Preview

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Flashcards in Lecture 5 Energy and Enzymes Deck (27)
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1

Metabolism

total of all chemical reactions in the body

2

Catabolic reactions

break down large molecules into smaller ones ex: glycogen -> glucose

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Anabolic reactions

Build up larger molecules from smaller ones amino acids -> proteins

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Exergonic reactions

release energy

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endergonic reactions

require energy

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Name the types of metabolic reactions

Hydrolysis & Dehydration Phophorylation & Dephosphorylation Oxidation-Reduction Reactions

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Hydrolysis 

Add H20 to break bonds between monomer units 

catabolic 

A-B + H20 -> A-OH + H-B

e.g. surcose + H20 -> glucose + fructose 

8

Dehydration 

Remove H20 to join monomers 

anabolic 

A-OH + H-B -> A-B +H20

e.g. peptide bond formation 

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Phosphorylation 

addition of a phosphate group (Pi)

C+Pi -> C-P+H20

e.g. ATP synthesis 

10

Transfer of phosphate from ATP 

catalyzed by kinase enzyme 

C+ATP -> C -P +ADP

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Dephosphorylation 

removal of a phosphate group

C-P + H20 -> C + Pi

e.g. ATP hydrolysis 

12

Oxidation-Reducation (redox) Reactions

Electron transfer reactions: Oxidation is loss, Reduction is gain of electrons 

major energy source of cells: Oxidation of sugars, fatty acids, and amino acids

 

13

Redox reactions

are coupled: one molecule is oxidized another is reduced 

in cells usually involve transfer of H atoms (not H+ ions)

e.g. reduction of pyruvate to lactate 

14

Coenzymes in redox reactions

role in cellular respiration 

act as temporary carriers of H atoms and their electrons 

NAD+ + 2 H (oxidized) -> NADH + H+(reduced)

FAD + 2H (oxidized) -> FADH2 (reduced)

oxygen is the final electron acceptor in cellular respiration 1/2 O2 + 2H -> H20

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Energy Metabolism 

cells use chemical energy to do biological work: movement, synthesis, transport 

energy is released in exergonic reactions that convert high-energy to lower-energy molecules 

e.g. oxidation of glucose 

16

ATP energy currency of cells 

role in energy metabolism 

(production of ATP)

energy captured from oxidation of substrates is used to produce ATP 

energy released from ATP hydrolysis powers energy-required processes 

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Enzymes 

are biochemical catalyst - speed up chemical reactions

most enzymes are proteins 

increase reaction rate by lowering activation energy or providing an alternative chemical pathway for the reaction

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Name the 4 functional properites of enzymes

Substrate specificity 

Sensitivity to temp and pH

Saturation kinetics 

Regulation 

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Substrate Specificity 

substrate (reactant) binds reversibly to active site of the enzyme

specific fit between substrate and active site (shape and charge polarity)

induced fit: enzyme pulls on chemical bonds of substrates 

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Sensitivity to temp and pH

effects on tertiary structure of proteins 

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Saturation Kinetics 

low and high [s] what happens 

limited by? 

reaction rate depends on substrate concentration (non-linear) 

at low [s] reaction rate increases w/ increasin [s]

at high [s] reaction rate reaches maximum level 

at the saturation point, all active sites are occupied 

maximum rate is limited by number of available enzymes 

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Regulation 

Covalent Regulation 

Involves? 

 

regulation of enzyme via covalent binding of a chemical group 

usually involves addition of phosphate group which activates the enzyme 

E (inactive enzyme) + ATP -> E-P (acitve enzyme) + ADP 

 

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Allosteric Regulation 

regulation by non-covalent binding of a modulator to a regulatory site on the enzyme 

can be either allosteric activation or allosteric inhibition 

reaction rate depends on concentration of the modulator as well as substrate 

 

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Feedback inhibition 

product of a reaction pathway can act as a modulator which inhibits an enzyme in an earlier step (via allosteric inhibiton) 

regulates formation of products 

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Example of enzymes 

Catalase 

2 H202 -> 2 H20 + 02

Carbonic anhydrase 

H20 + C02 ->

Hexokinase 

glucose + ATP -> glucose-6-phosphate + ADP 

26

Clinical applications 

abnormal enzyme levels may be associated with disease (e.g. liver enzyme tests)

Genetic deficiency in an enzyme -> inborn errors of metabolism (e.g. PKU)

27

Kinase 

protein kinase enzymes catalyze phosphorylation of other enzymes; important in cell signaling