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AEBI 122 > Chapter 8 > Flashcards

Chapter 8 Flashcards

1
Q

what is metabolism?

A

is the totality of an organisms chemical reactions

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2
Q

what is a metabolic pathway?

A

begins with a specific molecule and ends with a product

- each step is catalyzed by a specific enzyme

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3
Q

what is a catabolic pathway?

A

release energy by breaking down complex molecules into simpler compounds
- cellular respiration the breakdown of glucose in the presence of oxygen is an example of catabolic pathway

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4
Q

what is an anabolic pathway?

A

consumes energy to build complex molecules from simpler ones
- the synthesis of a protein from amino acids is an example of anabolism

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5
Q

what is bioenergetics?

A

is the study of how organisms manage their energy resources

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6
Q

what is energy?

A

the capacity to cause change

- energy exist in various forms, some which can perform work

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7
Q

what is kinetic energy?

A

is energy associated with motion

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8
Q

what is thermal energy (heat)?

A

is kinetic energy associated with random movement of atoms or molecules

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9
Q

what is potential energy?

A

is energy that matter possesses because of its location or structure

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10
Q

what is chemical energy?

A

is potential energy available or released in a chemical reaction

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11
Q

what is thermodynamics?

A

is the study of energy transformations

  • in a closed system, such as that approximated by liquid in a thermos, is isolated from its surroundings
  • in an open system, energy and matter can be transferred between the system and its surroundings
  • ORGANISMS ARE OPEN SYSTEMS
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12
Q

what is the first law of thermodynamics ( The principle of conservation of energy)?

A

The energy of the universe is constant: energy can be transferred and transformed, but it cannot be created or destroyed

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13
Q

what is the second law of thermodynamics?

A

every energy transfer or transformation increases the entropy (disorder) of the universe
- for a process to occur without energy input, it must increase the entropy of the universe

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14
Q

what is biological order and disorder?

A
  • cells create ordered structures from less ordered materials
  • energy flows into an ecosystem in the form of light and leaves in the form of heat
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15
Q

what is entropy (disorder)?

A

may decrease in an organism, but he universe’s total entropy increase

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16
Q

what is free energy?

A

is energy that can do work when temperature and pressure are uniform, as in a living cell

  • is the measure of a systems inability, its tendency to change to a more stable state
  • the change in free energy (ΔG) during a process is related to the change in enthalpy, or change in total energy (ΔH), change in entropy (ΔS), and temperature in kelvin (T)

ΔG = ΔH -TΔS

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17
Q

what is a spontaneous process?

A
  • only process with a negative ΔG are spontaneous
  • spontaneous processes can be harnessed to perform work
  • during a spontaneous free energy decreases and the stability of a system increases (Gfinal smaller than Ginitial)
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18
Q

what is an exergonic reaction?

A

proceeds with a net release of free energy and is spontaneous

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19
Q

what is an endergonic reaction?

A

absorbs free energy from its surroundings and is non-spontaneous; its net free energy is positive

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20
Q

equilibrium and metabolism?

A
  • reactions in a closed system eventually reach equilibrium and then do work
  • cells are not in equilibrium, they are open systems experience a constant flow of materials
  • a defining feature of life is that metabolism is never at equilibrium
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21
Q

A catabolic pathway in a cell does what?

A

A catabolic pathway in a cell releases free energy in a series of reactions

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22
Q

A cell does three main kinds of work what are they?

A
  1. chemical - pushes endergonic reactions
  2. transport - pumps substances across membranes
  3. mechanical - movement of cilia
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23
Q

what is energy coupling?

A

the use of an exergonic process to drives and endergonic one
- most coupling in cells is mediated by ATP- as in immediate source of energy

24
Q

what is ATP?

A

adenosine triphosphate is the cell’s energy shuttle

- ATP is composed of ribose (a sugar), adenine ( a nitrogen base) and three phosphate groups

25
Q

how does the hydrolysis of ATP work?

A
  • the bonds between the phosphate groups of ATP’s tail can be broken by hydrolysis
  • energy is released when the terminal phosphate bond is broken
26
Q

when the terminal phosphate bond is broken in ATP why does this release energy?

A
  • this release of energy comes from the chemical change to a state of lower free energy, not from the phosphate bonds themselves (by hydrolysis the three negative phosphate groups is eliminated)
27
Q

The hydrolysis of ATP is what type of reaction?

A
  • the energy from the exergonic reaction of ATP hydrolysis can be used to drive an endergonic reaction
  • OVERALL, the coupled reactions are exergonic
28
Q

what is phosphorylation?

A

transferring a phosphate group to some other molecule, such as a reactant

  • ATP drives endergonic reactions by phosphorylation
  • the phosphorylated intermediate is more reactive (less stable) than the original
29
Q

what is a catalyst?

A

is a chemical agent that speeds up a reaction without being consumed by the reaction

30
Q

what is an enzyme?

A

an enzyme is a catalytic protein

  • hydrolysis of sucrose by the enzyme sucrase is an example of an enzyme-catalyzed reaction
  • most reactions are reversible to enzymes can catalyze both forwards and backwards reactions
31
Q

what is free energy of activation, or activation energy (Ea)?

A

the initial energy needed to start a chemical reaction is called the activation energy
- activation energy is usually supplied in the form of heat from the surroundings

32
Q

what is a substrate?

A

the reactant that an enzyme acts on is called the enzyme’s substrate

33
Q

what is an enzyme-substrate complex?

A

the enzyme binds to its substrate, forming an enzyme-substrate complex

34
Q

what is an active site?

A

is the region on the enzyme where the substrate binds

35
Q

what does specificity mean?

A

the specificity of an enzyme results from its shape and its amino acid sequence

36
Q

what does induced fit mean?

A

induced fit of a substrate brings chemical groups of the active site into positions that enhance their ability to catalyze the reaction

37
Q

The active site can lower an Ea barrier by?

A
  • orienting substrates correctly
  • straining substrate bonds
  • providing a favourable microenvironment
  • covalently boding to the substrate
38
Q

what does substrate orientation mean?

A

it means enzymes hold substrates in the optimal position of the reaction

39
Q

what are come characteristics of R groups on enzymes?

A
  • acidic or basic R groups on the enzyme may change the charge of the enzyme
  • Charged R groups may attract the substrate
  • Cofactors of the enzyme increase the reactivity of the substrate by removing or donating electrons
40
Q

Inducing strain in the substrate does what?

A
  • shifts in the conformation after binding cause an induced fit between the enzyme and the substrate
  • covalent bonds of the substrate are strained
41
Q

what is the Michaelis Constant (Km)?

A

is the substrate concentration at one half of Vmax

  • units of Km are concentration units
  • the Km reflect the affinity of the enzyme for the substrate
42
Q

what is the Michaelis-Menten equation?

A

maximum velocity of an enzymatic equation results from the formation of the enzyme-substrate complex

v = Vmax [S]/ [S] + Km

43
Q

what are the predictions one can assume from the Michaelis-Menten equation?

A
  • At low substrate concentration the velocity is proportional to the substrate concentration
  • At intermediate substrate concentration the velocity depends on substrate as indicated by graph
  • At high substrate concentration, reaction velocity independent of substrate concentration
44
Q

An enzymes activity can be affected by?

A
  • general environmental changes such as temperature and pH

- Chemicals that specifically influence the enzyme

45
Q

what are Cofactors?

A

are non-protein enzyme helpers; cofactors can be inorganic (such as a metal in ionic form) or organic

46
Q

What is a Coenzyme?

A

an organic cofactor is called a coenzyme; it plays a crucial role in catalysis
- coenzymes include vitamins

47
Q

what is reversible inhibition?

A

weak interactions (Enzyme inhibitor)

48
Q

what is irreversible inhibition?

A

covalent bonding (Enzyme inhibitor)

49
Q

what are competitive inhibitors?

A

bind to the active site of an enzyme, competing with the substrate
- to overcome this type of inhibition, increase the concentration of substrate which will increase the availability of active sites

50
Q

what are non-competitive inhibitors?

A

bind to another part of an enzyme, causing the enzyme to change shape and making the active site less effective
- ie: toxins, poisons, pesticides, and antibiotics

51
Q

what is an effector?

A

any molecule or ion that changes the activity of an enzyme

52
Q

what is an allosteric effector?

A

if an effector binds to a different site than the active site it is called an allosteric effector

53
Q

what is allosteric regulation?

A

occurs when a regulatory molecule binds to a protein at one site and affects the proteins function at another site
- may either inhibit or stimulate an enzymes activity

54
Q

what is cooperativity?

A

is a form of allosteric regulation that can amplify enzyme activity
- in cooperativity, binding y a substrate to one active site stabilizes favourable conformational changes at all other subunits

55
Q

what is feedback inhibition?

A

the end product of a metabolic pathway shuts down the pathway
- feedback inhibition prevents a cell from wasting chemical resources by synthesizing more product than is needed

AEBI 122 (6 decks)

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