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MED-103 Biology I (2024-25) > Topic 8: metabolism > Flashcards

Topic 8: metabolism Flashcards

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1
Q

What is earth’s energy flow?

A

Sun > producer > consumer > decomposer

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2
Q

Define metabolism

A
  • Totality of an organism’s chemical reaction
  • Energy is stored = anabolic processes
  • Energy is released = catabolic processes
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3
Q

Define metabolic pathways

A
  • Begins with specific molecules = ends with products
  • Each step catalyzed by specific enzyme
  • Controlled according to cellular demands
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4
Q

Define catabolic pathways

A
  • Break down complex molecules = simpler molecules
  • Release energy e.g. cellular respiration
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5
Q

Define anabolic pathways

A
  • Simple molecules = synthesized into complex molecules
  • Consume energy e.g. photosynthesis + protein synthesis
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6
Q

What are the 3 forms of energy?

A

1) KE = associated with motion
2) Heat = associated with random movement of atoms
3) PE = energy stored due to location + structure of matter + chemical energy stored in molecular structure

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7
Q

Define free energy

A
  • Living system’s energy that can do work under cellular conditions
  • Organisms live by spending free energy
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8
Q

Define free energy change

A
  • Indicates whether reaction occurs spontaneously or not
  • ΔG = Gfinal- Ginitial
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9
Q

Describe exergonic reactions

A
  • Spontaneous reactions
  • Free energy released
  • ΔG = negative
  • Therefore Gfinal < Ginitial
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10
Q

Describe endergonic reactions

A
  • Non-spontaneous reactions
  • Absorb free energy from surroundings
  • ΔG = positive
  • Therefore Gfinal > Ginitial
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11
Q

Describe equilibrium in metabolism

A
  • Reaction in closed systems = equilibrium
  • Cells in body = open system
  • Metabolic pathways many stages = constant flow of materials in + out = NOT equilibrium
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12
Q

Describe ATP + function + structure

A
  • Nucleotide that stores energy in phosphate bonds
  • It is energy-rich = unstable = tends to break down
  • Function = provides energy for cellular functions
  • Structure = phosphate groups + ribose + adenine
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13
Q

Define ATP hydrolysis

A

ATP > ADP + Pi = enery release

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14
Q

Define ATP synthesis

A

ADP + Pi > ATP = energy stored in phosphate bonds

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15
Q

Explain energy coupling

A
  • Done by ATP to power cellular work
  • Is the use of exergonic process to drive endergonic process
  • ATP mediated coupling = endergonic process driven by ATP hydrolysis which is exergonic process = provides energy required
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16
Q

3 types of endergonic cellular work powered by ATP hydrolysis

A
  • By phosphorylation
    1) Mechanical = phosphorylates motor proteins
    2) Transport = phosphorylates transport proteins
    3) Chemical = phosphorylates key reactants
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17
Q

Explain ATP hydrolysis

A
  • Exergonic reaction = energy released = either 2 terminal phosphate bonds of ATP broken
  • Can be coupled to endergonic reactions
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18
Q

Explain ATP synthesis

A

1) Catabolic pathways = energy
2) Energy required to regenerate ATP from ADP + Pi

19
Q

Give the formula for cellular respiration

A

C6H12O6 + Ο2 —-> CO2+ H2O+ ΑΤP

20
Q

Define catalyst

A
  • Chemicaagent = speeds up reaction without being consumed
21
Q

Define enzyme

A
  • Catalytic protein = speeds up metabolic reactions by lowering activation energy
  • E.g. sucrase hydrolyzing sucrose
22
Q

Define activation energy

A
  • Initial amount of energy needed to start a chemical reaction
  • Needed to de-stabilize the structure of reactants = react more easily
  • Supplied as heat = increase speed of molecules = frequent collisions
23
Q

Explain how enzymes lower AE

A
  • Reaction is catalyzed by lowering AE = speeds up reaction
  • Enzyme doesn’t affect if reaction is spontaneous not only speed up reaction already happening
24
Q

Define substrate

A
  • Reactant of enzyme to act on
  • E.g. sucrose is substrate for sucrase
25
Q

Describe substrate specificity

A
  • Enzyme binds to substrate = enzyme-substrate complex
  • Enzyme will only recognize it’s specific substrate
  • Enzyme 3D shape = determine function
26
Q

Describe the active site + induced fit model

A
  • Region on enzyme where substrate binds
  • Induced fit = enzyme changes shape when substrate binds to AS = brings chemical groups of AS to positions = enhance ability to catalyze reaction
27
Q

Explain the catalytic cycle of enzyme

A

1) Substrate enter AS = enzyme change shape = induced fit
2) Substrate held in AS = by weak H/ionic bonds
3) AS + R group lower AE by:
- Acting as template for substrate orientation
- Stressing substrate + stabilizing transition state
- Providing favorable environment
- Directly participate in catalytic reaction
4) Sustrate converted to products
5) Products released
6) AS back to original shape + available for new substrates

28
Q

Give environmental factors that effect enzyme activity

A
  • pH
  • Temp
  • Cofactors
29
Q

Define co-factors

A
  • Non-protein enzyme helpers required for enzyme activity
    1) Inorganic cofactors = metal ions
    2) Coenzymes = organic = vitamins
30
Q

Define denaturation

A
  • Loss of protein conformation due to unraveling = loss of function
31
Q

Why does temp + pH affect enzyme activity?

A
  • Each enzyme has optimal temp/pH which it functions
  • Optimal temp for human enzymes = 37.5
  • Optimal pH for pepsin = 2
  • Optimal pH trypsin = 8
32
Q

Describe irreversible inhibitors

A
  • Bind to enzyme via covalent bonding = inhibition permanent
  • Toxins + antibiotics + poisons
  • Sarin + DDT + parathion = inhibit NS enzymes
  • Penicillin derivatives = inhibit enzyme transpeptidase = synthesize bacterial cell wall
33
Q

Describe reversible inhibitors

A
  • Bind to enzyme via weak bonds = inhibition not permanent can be removed
    1) Competitive
    2) Non-competitive
34
Q

Describe competitive inhibitors

A
  • Bind to AS
  • Compete with substrate = mimics substrate = inhibits substrate from binding
  • Overcome = adding excess substrate
35
Q

Describe non-competitive inhibitors

A
  • Bind to other part of enzyme = change shape = inhibit function
  • Cannot be overcome by adding excess substrate
36
Q

2 Methods of enzyme regulation

A

1) Regulation of enzyme production by regulation of gene production
2) Regulation of enzyme activity by feedback inhibition = allosteric regulation

37
Q

Explain feedback inhibition

A
  • End product of metabolic pathway = inhibits the pathway
  • Role = prevents cell from wasting resources by synthesizing more product than needed
  • E.g. Inhibition of catabolic pathways by ATP + inhibition of anabolic pathways by end product
38
Q

Explain allosteric regulation

A
  • Reversible modulation in enzyme = made of polypeptide subunits
  • Can be +ve = activation OR -ve = inhibition
  • Proteins function at AS affected by binding of regulatory molecules at allosteric site via non-covalent binding = change shape
  • Can be hererotropic = allosteric site OR homotropic = substrate is regulatory molecule = bind to AS
39
Q

Describe heterotropic allosteric regulation

A
  • Activators = stabilize active form
  • Inhibitors = stabilize inactive form
40
Q

Describe homotropic allosteric regulation

A
  • Binding of substrate to AS of 1 subunit = conformation to active state = locks all other subunits in active state
  • Cooperativity = +ve allosteric regulation = binding of substrate to 1 subunit increases binding affinity in other subunits = e.g. O2
41
Q

Give an example of heterotropic allosteric activator/inhibitor

A
  • Activator = AMP activates PFK = glycolysis enzyme
  • Inhibitor = CO2 of haemoglobin = reduces haemoglobins affinity for O2 = O2 released in tissues
42
Q

Give an example of homotropic allosteric activator/inhibitor

A
  • Activator = O2 of haemoglobin
  • Competitive inhibitor = CO binds to haemoglobin in O2 site = increases CO affinity = O2 not released into tissues
42
Q

What are the locations of enzymes in cells?

A
  • Enzymes participating in same pathway = located close to each other
    1) Grouped in complexes
    2) Incorporated into membranes
    3) Contained inside organelles

MED-103 Biology I (2024-25) (10 decks)

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