Metabolism of enzymes Flashcards by Joanne Ogbebor

Define Metabolism

sum total of all chemical reactions involved in maintaining the living state of the cells, and thus the organism
Metabolism manages the material and energy resources in the cell

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Catabolic pathways [energy conserving]

degradative processes that release energy by breaking down complex molecules to simpler compounds (energy release and conservation as ATP)

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Anabolic pathways

processes of building (synthesis) complicated molecules from simpler ones that require energy (requires ATP and electron source stored in a form of reducing power)

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what are metabolites- fun fact

reactants, inter-mediates, and products of metabolic reactions
over 2000 known metabolic reactions

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Phototrophs use what as their energy source

light

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chemotrophs receive their energy from what

organic [chemoorganotrophs] or inorganic [chemolithotrophs] compounds

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what is carbon source of autotrophs

CO2

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what is the carbon source of heterotrophs

organic molecules from other organisms

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electron source of lithotrophs

reduced inorganic compounds

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organotrophs electron source

reduced organic compounds as electron source

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oxidizing agent of aerobes

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oxidizing agent of anaerobes

sulfate or nitrate

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facultative anaerobes can grow?

in presence or absence of O2 i.e. E.coli

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obligate anaerobes

poisoned by O2

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DEFINITION of energy- units

capacity to do work- calories of joules [J]

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ATP id the energy x of the cell

currency

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what are the 3 major types of work carried out by living cells

-Chemical work - synthesis of all cell components i.e. anabolism
-Transport work - take up nutrients/ions, eliminate waste
-Mechanical work - motility

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what are metabolic pathways

series of chemical oxidation-reduction reactions

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role of enzymes in metabolic pathways

mediated by enzymes

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what is metabolic channelling

localising metabolites and enzymes into different parts of the cell

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amount an enzyme that is synthesised is regulated by?

transcription and translation

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direct stimulation or inhibition of critical enzymes is controlled by?

posttranslational regulation

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role of oxidoreductases

catalyse the transfer of electrons from one molecule (the reductant, also called the hydrogen or electron donor) to another (the oxidant, also called the hydrogen or electron acceptor)

transferases

catalyse the transfer of a functional group (e.g. a methyl or phosphate group) from one molecule (called the donor) to another (called the acceptor)

Hydrolases

catalyse the hydrolysis of a chemical bond

lysases

catalyse the breaking of various chemical bonds by means other than hydrolysis and oxidation

isomerases

catalyse the structural rearrangement of isomers

Ligases

: catalyse the joining of two large molecules by forming a new chemical bond, usually with accompanying hydrolysis of a small chemical group pendant to one of the larger molecules

what are the 2 forms of cofactors

Prosthetic group – cofactor firmly attached to the apoenzyme Coenzyme – cofactor loosely attached to the apoenzyme and can dissociate after product is formed

what are 4 examples of iron cofactors and give 1 e.g. of enzymes they work with [inorganic]

Iron – catalase Magnesium – DNA polymerase Manganese - arginase Copper – cytochrome oxidase

give 4 examples of organic cofactors

NAD+, NADP+ [Niacin B3], biotin [Biotin], ascorbic acid [on vit C] and cobalamine [B12]

full name of ATP - function - it is a .. type of energy molecule it is?

adenosine 5'-triphosphate ATP - stores energy produced form exergonic reactions to drive endergonic reactions [links the reactions] - is a nucleotide - high energy molecule

ATP can be hydrolysed -> what 2 forms

ADP and P or AMP and energy = released [ delta G = -7.3mmol/l

definition of -delta G

high phosphate group transfer potential

what is substrate-level phosphorylation

Process of transferring a phosphate group from a high-energy molecule to ADP to form ATP Observed during catabolic processes

ATP chemiosmosis

ATP synthase = used -> synthesise ATP and the energy used for this is made from proton motive force produced by electron transport chain

release of energy from an energy source normally involves?

oxidation-reduction reactions

what is a redox couple

electron donor and acceptor

standard reduction potential Eo is what?

tendency of a donor to loose electrons

standard reduction potential Eo is what?

tendency of a donor to loose electrons

electron carriers are organised into ?

electron transport chain

what is the precursor for NAD and NADP- what does it accept from donor

niacin - 2e- and 1H+...... a second proton is released -- 320mB - begining of electron transfer chain

carbohydrate catabolism /glycolysis reaction[stage 1 and 2 of catabolism

glucose/fructose -> pyruvate + ATP + NADH + smaller 3-C molecules

LIPID CATABOLISM REACTION- GIVE 2 e.g.s of essential fatty acids that must be obtained from diet [stage 1 and 2 of catabolism]

Lipids - fatty acids + glycerol linoleic, arachidonic, linolenic acids

protein catabolism reaction how many Essential A.A. are there and where are they obtained from [stage 1+2 of catabolism]

protein -> A.A 10 ess. A.A. obtained from diet

Tricarboxylic acid cycle [other names - TCA, krebs or citric acid] is what type of pathway and what is it used for? - stage 3 of catabolism processes

amphibolic pathway [catabolism + anabolism for oxidation of F.acids-> CO2 [NADH, FADH2 and ATP = also produced]

Oxidative phosphorylation = in stage 3 of catabolic process give e.g.s of molecules reduced

is a catabolic pathway that provides ATP for anabolic processes high energy molecules like NADH and FADH2 = reduced -> drive phosphorylation of ADP -> ATP

for food to be oxidised during catabolism something else must be?

reduced

reduced NADH and NADPH function as?

sources of electrons during anabolic reactions

cellular respiration is a ? process that transfers energy from x -> form y

exergonic process x= glucose bonds y= ATP

Stage 1: * x molecules (proteins, CHO, etc.) are broken down into y * - - energy is generated in this phase Stage 2: * Small molecules (sugars, fatty acids, glycerol, some amino acids) are - * Mostly converted into the ? * A x ATP is generated at this stage Stage 3: * The x and y , final common pathways in the cell’s oxidation of fuel molecules * Acetyl CoA brings acetyl units into the x and they are completely oxidized to y * x pairs of electrons are transferred to the electron acceptors, NAD+ and FAD, for each acetyl group oxidized: * ATP is generated as the electrons x of these coenzymes to y in the process called oxidative phosphorylation * Over ?% of the ATP generated by the oxidation of foodstuffs = generated in this stage

large, smaller units no-useful energy = generated in this stage stage 2 - degraded into to simple units that play key role in metabolism - acetyl unit of acetyl coenzyme A - little stage 3 - citric acid cycle and oxidative phosphorylation - citric acid cycle ---completely oxidized to CO2 - flow from reduced forms of these coenzymes -> O2 - 4 - 90%

regulation of metabolic processes = controlled by controlling ? x3

1. The amounts of the different enzymes present * Regulation of transcription and translation 2. The catalytic activities of the various enzymes * Direct stimulation or inhibition (allosteric regulation) * Posttranslational regulation (+/- phosphoryl, methyl or adenyl groups) 3. The accessibility of substrates * Metabolic channelling – localising metabolites & enzymes into different parts of the cell

the amount of enzyme present depends on

rate of synthesis versus the rate of degradation of the enzyme

control of enzyme catalytic activity involves reversible covalent modifications how is this done? also controlled by feed-back inhibition/reversible allosteric inhibition- how is this one done

Enzyme activation/ inactivation by the addition or removal of a functional group * Fast method of enzymatic control (secs) - first reaction of the pathway is inhibited by the final product of the pathway - milliseconds

accessibility of substrate helps regulate metabolic processes

regulates the availability of the substrate

synthesis of ATP is x favourable and energy released can be coupled with - to link x with y

thermodynamically favourable [does not require energy] - thermodynamically unfavourable reaction-> link exergonic and endergonic reactions