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MEH > Energy reactions in cells > Flashcards

Energy reactions in cells Flashcards

1
Q

define cell metabolism

A

highly integrated network of chemical reactions that occur within cells

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2
Q

what is metabolism

A

set of processes that derive energy and raw materials from food stuffs and use them to support repair, growth and activity of the tissues in the body to sustain life

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3
Q

what are the functions of cell metabolism

A
  • energy for cell function and synthesis of cell components (ATP)
  • building block molecules for synthesis of components needed for growth, maintenance, repair and division of cell
  • organic precursor molecules to allow interconversion of building block molecules
  • biosynthetic reducing power for synthesis of cell components (NADPH)
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4
Q

what is shown in a metabolic map

A
  • start points
  • intermediates
  • end points
  • interconnections
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5
Q

catabolism

A
  • breakdown of larger molecules into smaller ones
  • produce intermediary metabolites
  • release large amounts of free energy
  • oxidative
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6
Q

what is anabolism

A
  • smaller molecules are built up into larger ones
  • use intermediary metabolites and energy (ATP) from catabolism to synthesise important cell components
  • reductive
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7
Q

sources of cell nutrients circulating the blood

A
  • diet
  • synthesis in body tissues from precursors
  • released from storage in body tissues
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8
Q

metabolism of cell nutrients

A
  • Degradation to release energy – all tissues
  • Synthesis of cell components – all tissues except mature erythrocytes
  • Storage – liver, adipose tissue, skeletal muscle
  • Interconversion to other nutrients – liver, adipose tissue, kidney cortex
  • Excretion – liver, kidney, lungs
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9
Q

humans are isothermal

A

can’t use heat energy for work so use chemical bond energy

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10
Q

exergonic reactions

A
  • reactions that release energy
  • occur spontaneously
  • ∆G < 0
  • catabolic pathways
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11
Q

endergonic reactions

A
  • requires energy input
  • ∆G > 0
  • anabolic pathways
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12
Q

enthalpy change (∆H)

A

difference in energy between products and reactants of a reaction

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13
Q

entropy (∆S)

A

measure of the disorder of the products relative to the reactants

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14
Q

Gibbs free energy

A

energy released in an exergonic reaction that is available to do work

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15
Q

free energy change (∆G)

A

∆G = ∆H - T∆S
reaction can only occur spontaneously if ∆G is negative

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16
Q

how is chemical bond energy released from fuel molecules

A

oxidation reactions
(accompanied by a reduction reaction REDOX)

17
Q

oxidation reactions

A
  • addition of oxygen
  • removal of H atoms or electrons
18
Q

reduction reactions

A
  • addition of H atoms or electrons
  • removal of oxygen
19
Q

what are H-carrier molecules

A
  • when fuel molecules are oxidised electrons and protons are transferred to carrier molecules
  • complex molecules that are synthesised from vitamins in diet
  • act as carriers of ‘reducing power’ for ATP production and biosynthesis
  • NAD+, NADP+, FAD
20
Q

H-carrier redox cycles

A
  • total concentration of oxidised and reduced carriers is constant
  • converted to reduced for by adding two H atoms
  • carrier molecules cycle between oxidative and reductive processes to maintain cell function
21
Q

what is ATP

A
  • adenosine triphosphate
  • adenine, ribose, triphosphate
  • energy carrier
  • ATP <> ADP <> AMP
22
Q

Coupling of exergonic and endergonic reactions using ATP

A
  • free energy from oxidation of fuel molecules used to drive synthesis of ATP
  • energy conserved as chemical bond energy in covalent bond of terminal phosphate group
  • energy released when phosphate group removed by hydrolysis
  • large amounts of free energy available so bond is known as ‘high energy of hydrolysis bond’
23
Q

ATP ADP cycle

A
  • limited amounts of ATP and ADP in cell
  • conc of ATP only sufficient for a few seconds of activity
  • rate of ATP turnover is very high
  • ATP rapidly resynthesised from ADP using free energy released by catabolism
  • ATP acts as carrier of free energy not a store
24
Q

high energy signals

A
  • activate anabolic pathways
  • ATP, NADH, NADPH, FAD2H
  • ATP signals that the cell has adequate enrgy levels for its immediate needs
25
Q

low energy signals

A
  • activate catabolic pathways
  • ADP+AMP, NAD+, NADP+, FAD
  • ADP and AMP signal that cell doesn’t have sufficient energy levels for its immediate needs
26
Q

AMP

A
  • adenylate kinase activated when ATP levels dropping, producing more AMP
  • increases ATP generation by glycolysis
  • important activator of AMP dependent kinase which regulated gene expression switching from anabolic to catabolic pathways
27
Q

other phosphorylated compounds with high energies of hydrolysis

A
  • phosphoenolpyruvate
  • 1,3-bisphosphoglycerate
  • creatine phosphate
  • ATP
28
Q

creatine phosphate

A
  • acts as a small store of free energy in muscle cells (skeletal and cardiac)
  • creatine + ATP —> creatine phosphate + ADP
  • when ATP concentration is high, creatine phosphate is formed (catalysed by creatine kinase)
  • used when ATP concentration falls suddenly
29
Q

creatine kinase as a marker of muscle damage

A
  • cytosolic enzyme that appears in blood soon after cell damage
  • made of two subunits - **M + B **
  • 3 different isoform combinations possible - MM, BB, MB
  • CK-MB used as marker for cardiac muscle damage but replaced by cardiac specific troponin tests
  • CK activity is a marker for any condition causing myocyte damage and used for patients with muscle injury or myopathy
30
Q

creatinine

A
  • breakdown product of creatine and creatine phosphate
  • no function in body and excreted via kidneys in urine
  • creatinine excretion is **proportional **to skeletal muscle mass
  • increased excretion of creatinine may indicate active muscle wasting
  • creatinine concentrations in blood and urine are good indicators of kidney function
  • abnormally high blood creatinine with low urinary creatinine may indicate reduced kidney function
31
Q

metabolism summary

A
  • interconversion of biological molecules in small chemical steps
  • involves series of reactions in defined metabolic pathways (catabolic and anabolic)
  • catabolism involves breakdown of chemicals to release reducing power and energy
  • reducing power is converted to ATP by oxidative phosphorylation
  • energy and reducing power used to drive synthesis of new molecules (anabolism) or produce work
  • reducing power and enrgy are transferred between pathways by carriers

MEH (26 decks)

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