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BIO 101 EXAM 2 > CHAPTER 8 > Flashcards

CHAPTER 8 Flashcards

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1
Q

chemical reaction

A

-occurs when atoms have enough energy to combine or change bonding partners
-reactants –> products
-chemical reactions in cells are organized in metabolic pathways that er interconnected

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2
Q

metabolism

A

-sum total of all chemical reactions occurring in a biological system at a given time

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3
Q

metabolic reactions

A

involve energy changes

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4
Q

energy

A

-is the capacity to do work, or the capacity for change
-potential or kinetic energy
-energy can be converted from one form to another

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5
Q

potential energy

A

energy stored as chemical bonds, concentration gradient, or change imbalance

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6
Q

kinetic energy

A

the energy of movement

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7
Q

anabolic reactions

A

complex molecules are made from simple molecules; energy is required

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8
Q

catholic reactions

A

complex molecules are broken down to simpler ones; energy is released

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9
Q

how are catabolic and anabolic reactions linked?

A

the energy released in catabolic reactions is used to drive anabolic reactions to do biological work; its an on going cycle

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10
Q

laws of thermodynamics

A

-apply to all matter and all energy transformations in the universe
-energy is neither created nor destroyed
-when energy is converted from one form to another, some of that energy becomes unavailable to do work

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11
Q

entropy

A

(S): a measure of the disorder in a system

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12
Q

in biological systems:

A

-total energy is called enthalpy (H)
-free energy (G) is the usable energy that can do work
-unusable energy is represented by entropy (S) multiplied by the absolute temperature (T)
- H = G + TS

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13
Q

change in energy can be measured in?

A

-calories or joules

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14
Q

change in free energy (ΔG) of a chemical reaction

A

ΔG = ΔH -TΔS

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15
Q

if ΔG is -

A

free energy is released

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16
Q

if ΔG is +

A

free energy is required

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17
Q

if free energy is not available

A

the reaction does not occur

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18
Q

what does the second law of thermodynamics also state

A

-that disorder tends to increase because of energy transformations

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19
Q

exergonic reactions

A

-release free energy (-ΔG)
-cell respiration
-catabolism

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20
Q

catabolism

A

-breaks down an ordered reactant into smaller, more randomly distributed products –> complexity decreases (generates disorder)

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21
Q

endergonic reactions

A

-consume free energy (+ΔG)
-active transport
-cell movements
-anabolism

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22
Q

anabolism

A

-makes a single product (a highly ordered substance) out of many smaller reactants (less ordered) –>complexity (order) increases.

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23
Q

chemical equilibrium

A

balance between forward and reverse reactions, a state of no net change
ΔG = 0

24
Q

ΔG is related to the equilibrium point

A

-the further towards completion the point of equilibrium is, the more free energy is released
-ΔG values near zero are characteristic of readily reversible reactions
-final equilibrium does not change, and ΔG does not change

25
Q

ATP

A

(adenosine triphosphate)
-captures and transfers free energy
-can be hydrolyzed to ADP and P, releasing a lot of energy for endergonic reactions
-can also phosphorylate (donate a phosphate group to) other molecules, which gain some energy

26
Q

formation of ATP

A

-it is endergonic
-ADP + P + free energy —> ATP +H2O

27
Q

catalyst

A

increases rates of chemical reactions; they are no altered by the reactions

28
Q

most biological catalysts are?

A

-enzymes (proteins) that act as a framework in which reactions can take place
-enzyme lower the energy barrier for reactions
-enzymes can increase reaction rates by 1 million to 10^17 times

29
Q

activation energy (Ea)

A

-the amount of energy required to start a reactions
-some reactions are slow because of an energy barrier
-can come from heating the system
-enzymes lower the energy barrier by bringing the reactants together

30
Q

transition state

A

activation energy puts the reactants in a reactive mode

31
Q

transition state intermediates

A

activation energy changes the reactants into unstable forms with higher free energy

32
Q

substrates

A

-another name for reactants
-substrate molecules bind to the active site of the enzyme

33
Q

what determines an enzymes specificity

A

-the 3D shape determines it
-changes in the shape changes the function
-depends on precise interlocking of molecular shapes and interactions of chemical groups at the active site

34
Q

six categories of enzymes

A

-oxidoreductases
-transferases
-hydrolases
-lyases
-isomerases
-ligases

35
Q

enzyme-substrate complex (ES)

A

-is held together by hydrogen bonds, electrical attraction, or covalent bonds
- E + S –> ES –> E + P
-enzyme may change while bound to the substrate but returns to its original form

36
Q

an enzyme may use on or more mechanisms to catalyze a reaction:

A

-orient substrates so they can react
-induce strain by stretching the substrate– makes bonds unstable and more reactive to other substrates
-temporarily add chemical groups

37
Q

adding chemical groups:

A

-acid-base catalysis: side chains in the active site transfer H+ to or from the substrate, destabilizing covalent bonds (shift change)
-covalent catalysis: a functional group in a side chain forms a temporary covalent bond with the substrate (break down over time)
-metal ion catalysis: metal ions such as copper, iron, and manganese lose or gain electrons without detaching from the enzymes (important for oxidation-reduction reactions)

38
Q

induced fit

A

some enzymes change shape when it binds the substrate, which alters the shape of the active site

39
Q

ribozymes

A

-RNA molecules acting as biological catalysts
-EX: RNA molecule catalyzes formation of peptide bonds between amino acids

40
Q

some enzymes require “partners”

A

-prosthetic groups: non-amino acid groups bound to enzymes
-inorganic cofactors: ions permanently bound to enzymes
-coenzymes: small carbon-containing molecules; not permanently bound

41
Q

what does the rate of catalyzed reactions depend on?

A

-depends on substrate concentration
-concentration of an enzyme is usually much lower than the substrate
-at saturation, all enzyme is bound to substrate; it is working at maximum rate

42
Q

maximum rate is used to calculate enzyme efficiency:

A

-molecules of substrate converted to product per unit time (turnover number)
-range 1 to 40 milion molecules/second

43
Q

enzyme activity can be controlled in two ways:

A

-regulation of gene expression: how many enzyme molecules are made
-regulation of enzyme activity: enzyme may change shape, or be blocked by regulators

44
Q

systems biology

A

-the complex pathways are modeled using computer algorithms
-enzymes help organize and regulate metabolic pathways

45
Q

enzyme inhibitors

A

-molecules that bind to the enzyme and slow reactions rate
-naturally occurring inhibitors regulate metabolism
-artificial ones can be used to read disease, kill pests, or study how enzymes work

46
Q

irreversible inhibition

A

-inhibitor covalently bonds to side chains in the active site and permanently inactivates the enzyme

47
Q

reversible inhibition

A

-inhibitor bonds non-covalently to the active site and prevents substrate from binding

48
Q

competitive inhibitors

A

-compete with the natural substrate for binding sites
-degree of inhibition depends on concentration of substrate and inhibitor
-EX: cancer drug methotrexate

49
Q

uncompetitive inhibitors

A

-bind to the enzyme – substrate compex, preventing release of products

50
Q

noncompetitive inhibitors

A

-bind to enzyme at a different site (not the active site)
-the enzyme changes shape and alters the active sire (allostery)

51
Q

allosteric regulation

A

-a non-substrate molecule binds enzyme at a site different from the active site, which changes enzyme shape
-active form: proper shape to bind substrate
-inactive form: cannot bind substrate
-non-substrate molecules may be an inhibitor or an activator

52
Q

allosteric enzymes

A

-reaction rate is very sensitive to substrate concentration
-they are very sensitive to low concentrations of inhibitors
-making them important in regulating metabolic pathways

53
Q

metabolic pathways

A

-first reaction is the commitment step – other reactions then happen in sequence
-feedback inhibition: the final product acts as a noncompetitive inhibitor of the first enzyme, which shuts down the pathway

54
Q

how are enzymes regulated? and activated or deactivated?

A

-many enzymes are regulated through reversible phosphorylation
-can be activated when protein kinase adds a phosphate group, and activated by a protein phosphatase

55
Q

when are enzymes most active?

A

-most active at a particular pH, which influences ionization of functional group

56
Q

enzymes in relation to temperature

A

-every enzyme has an optimal temperature; high temps, non covalent bonds begin to break; warming up –> speeds up, but too much warming denatures it
-some are adapted to warm temps and do not denature
-ex: most human enzymes are more stable at high temps

BIO 101 EXAM 2 (4 decks)

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