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The Dynamic Cell > Metabolism > Flashcards

Metabolism Flashcards

1
Q

What is bioenergetics

A

Quantitative study of energy transduction occurring in living cells. Study of the nature and function of the chemical processes that are responsible for these energy transduction

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2
Q

What is the first law of thermodynamics

A

energy cannot be created or destroyed, but it can be converted from one form to another

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3
Q

What is gibbs free energy

A

the amount of energy in a system available to do work.

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4
Q

What does free energy change derive from

A
  1. Changes in heat content (DH) = enthalpy change
  2. Changes in the state of order (DS) = entropy change
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5
Q

What doe sit mean if delta G is negative

A

energy is liberated and the reaction is said to be exergonic and can occur spontaneously

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6
Q

What does it mean if delta G is positive

A

reaction is endergenic and requires energy input

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7
Q

What biological processes do we require energy for

A
  1. Mechanical work e.g., muscle contraction
  2. Active transport
  3. Synthesis of complex biomolecules from simple precursors
  4. Also signal transduction (environmental responses), generation of light (fire flies) and electricity (eels)
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8
Q

How is energy obtained

A
  1. Phototrophs – obtain energy by trapping light e.g., photosynthesis
  2. Chemotrophs – obtain energy by oxidation of food stuffs e.g., catabolism
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9
Q

Where do chemoorganotrophs ge4t their energy from

A

organic compounds by oxidation (e.g., respiration)

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10
Q

Calories in food groups

A
  1. Fats – 9kcal/g
  2. Carbohydrates – 4kcal/g
  3. Proteins – 4kcal/g
  4. Alcohol – 7kcal/g
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11
Q

Why do we control the extraction of energy from food

A

so we don’t release all the energy at once and increase body temperature excessively

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12
Q

Extraction of energy from food

A
  1. Large molecules broken down into smaller units. No useful energy captured
  2. Small molecules degraded into a few simple units that play a role in central metabolism. Some ATP generated
  3. ATP produced from the complete oxidation of simple units by the final common pathways for oxidation of fuel
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13
Q

Reduction reactions as an organic compound is degraded

A

electrons flow through intermediates to oxygen (the final electron acceptor) or are used to reduce other cellular components

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14
Q

Biological redox reaction

A

1) 1. Direct electron transfer e.g. Fe2+ + Cu2+ ——> Fe3+ + Cu+

  1. Direct transfer of hydrogen ions e.g.AH2 + B ——-> A + BH2
  2. Direct combination with oxygen as with mono-oxygenase reactions e.g.R-CH3 + ½O2 ——–> R-CH2OH
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15
Q

What do dehydrogenases do

A

oxidise organic compounds by abstracting 2H+ and 2 e- and passing them to a mobile carrier in biodegradation and energy abstraction (I.e., respiration)

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16
Q

How can dehydrogenases reduce

A

can reduce organic compounds by adding 2H+ and 2 e- from a mobile electron carrier typically in biosynthetic pathways

17
Q

Synthesis and use of NADH

A

produced in catabolic reactions and by TCA cycle. Used in the generation of ATP by OxPhos. Usually found inside the mitochondria

18
Q

Use and synthesis of NADPH

A

produced by PPP. Used primarily for reductive biosynthesis (e.g., FA synthesis). Usually found in the cytoplasm

19
Q

Use and synthesis of FADH2

A

produced in catabolic reactions and by TCA cycle. Used in the generation of ATP by OxPhos (generates less energy than NADH)

20
Q

What bonds does ATP contain

A

2 phosphoanhydride bonds on its triphosphate unit

21
Q

ATP equations

A

ATP + H2O ——> ADP + Pi + energy. ATP + H2O ——–> AMP + PPi + energy

22
Q

Stability of free energy

A

free energy is negative and therefore thermodynamically unstable but is kinetically stable.

23
Q

Use of ATP

A

principal immediate donor of free energy in biological systems rather than long-term storage form. Consumed within minutes of formation, very high turnover. Around 50kg of ATP consumed in 24h period

24
Q

How is ATP produced - substrate level phosphorylation

A

Transfer of phosphoryl group from metabolites with high – phosphoryl transfer potential to ADP producing ATP

25
Q

How is ATP produced - oxidative phosphorylation

A

Process of ATP formation as a result of transfer of electrons from fuels via electron carriers (NADH or FADH2) to the final electron acceptor oxygen

26
Q

4 functions of metabolism

A
  1. Obtain energy e.g., ATP
  2. Convert nutrients into own characteristic molecules
  3. Polymerize monomeric precursors e.g., polysaccharides
    4.Synthesise and degrade molecules required for special cellular functions e.g., intracellular messengers
27
Q

what are catabolic reactions

A

transform fuels into usable cellular energy

28
Q

What are anabolic reactions

A

utilize the useful energy formed by catabolism to generate complex structures from simple ones

29
Q

Catabolic v anabolic - ATP

A

catabolic - produces ATP, anabolic requires ATP

30
Q

Catabolic v anabolic -free energy

A

catabolic - negative free energy change. Anabolic - positive free energy change

31
Q

Catabolic v anabolic - reducing potential

A

catabolic - produces reducing potential, anabolic - requires reducing potential

32
Q

Catabolic v anabolic - generating NAD

A

catabolic - generates NADH and FADH2. Anabolic - uses NADPH

33
Q

Why is metabolic regulation required

A

because we need energy to function but we do not have a constant supply of energy but the expenditure is continuous so we need to store and release when it is required

34
Q

What does metabolic regulation cover

A

distribution and storage of nutrients after meals, release, delivery and utilisation. Works on a molecular level by modulation of enzyme activities

35
Q

How is metabolism regulated

A
  1. Levels and accessibility of substrates (thermodynamics and compartmentation)
  2. Amounts of metabolic enzymes (rate of transcription and degradation)
  3. Modulation of catalytic activities of enzymes (allosteric regulation, covalent modification, association with regulatory proteins)
36
Q

What is the amount of enzyme present determined by

A
  1. Alteration (production) of transcription factor by external signals
  2. Stability of mRNA species
  3. Rate of translation (dependent on various factors)
  4. Rate of protein degradation
37
Q

Allosteric regulation

A

An allosteric enzyme has a site distinct from the substrate-binding site. Ligands which bind to the allosteric site are termed allosteric effectors or modulators. Binding causes conformational changes so affinity for substrate or other ligands change. Can be positive (activator) or negative (inhibitor)

38
Q

What is binding of the end-product dependent on

A

concentration, and binding affinity induces conformational change affecting active site

The Dynamic Cell (8 decks)

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