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IB HL Biology I > Unit 7 > Flashcards

Unit 7 Flashcards

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1
Q

Metabolism (4)

A
  • life-sustaining chemical reactions in an organism
  • converts food to energy
  • converts food to monomers of proteins, lipids, and carbs
  • elimination of nitrogenous wastes
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2
Q

What do the chemical reactions of our metabolism require?

A

an initial input of energy to take place

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3
Q

activation energy

A

amount of energy reactants must absorb to start a chemical reaction

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4
Q

How can we increase the rate of chemical reactions?

A

enzymes

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5
Q

What is another name for enzyme?

A

biological catalysts

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6
Q

enzyme functions (3)

A
  • catalyze/speed up reactions
  • mostly proteins (some RNA)
  • reduce activation energy
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7
Q

How do enzymes work?

A

by binding to reactants and speeding up their conversion to products

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8
Q

substrate

A

reactant which binds to enzyme

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9
Q

active site

A

region where substrate bind and undergoes a chemical reaction

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10
Q

enzyme-substrate complex

A

temporary association between enzyme and substrate

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11
Q

enzyme facts (3)

A
  • must COLLIDE with reactants for binding to occur
  • remain UNCHANGED after they release products
  • are REUSABLE
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12
Q

What types of reactions to enzymes catalyze? (2)

A
  • hydrolysis
  • condensation
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13
Q

sucrase

A

breaks down sucrose

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14
Q

proteases

A

break down proteins

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15
Q

lipases

A

break down lipids

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16
Q

DNA polymerase

A

builds DNA adds nucleotides to DNA strand

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17
Q

What is an important characteristic of enzymes?

A

they are highly specific

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18
Q

Why are enzymes substrate-specific? (2)

A
  • active sites have 3D shapes that determine which substrate can bind
  • active sites hold substrates in the optimum position to carry out reactions
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19
Q

The shape of the active site is…(2)

A
  • determined by the tertiary structure of the protein
  • complementary to the substrate and facilitates binding
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20
Q

What do R groups have to do with enzyme-substrate specificity? (2)

A
  • R groups lining the enzyme active sites use chemical attraction to facilitate substrate biding
  • R group interactions temporarily hold the substrate in active site
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21
Q

How are substrates held in place?

A

by weak interaction between amino acids

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22
Q

What weak reaction hold substrates in place? (3)

A
  • hydrogen bonds
  • hydrophobic interactions
  • ionic interactions
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23
Q

Hexokinase

A

catalyzes first step of glycolysis (cellular respiration)

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24
Q

How does hexokinase lower activation energy? (3)

A
  • glucose and ATP are both negatively charged
  • it takes energy to bring 2 negatively charged objects together
  • hexokinase lowers this energy barrier with positive charges in its active site
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25
Q

Substrates are held in the active site of hexokinase through which interaction?

A

Ionic

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26
Q

What about hexokinase facilitates the binding of the enzyme and its substrates?

A

the shape of the active site is complementary to the shape of the substrate molecule

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27
Q

Lock and Key Hypothesis (2)

A
  • active site and substrate have complementary shapes like puzzle pieces
  • enzymes specifically react with only one or a very few substrates
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28
Q

Analogy for Lock and Key Hypothesis

A

only the correctly sized key fits into the keyhole of the lock

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29
Q

What does the lock and key hypothesis explain phenomena wise? (2)

A
  • enzyme specificity
  • activity loss when enzymes denature/change shape
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30
Q

Why can’t the lock and key hypothesis explain all experimental evidence?

A

in the lock and key hypothesis, the active site is not favorable to product formation

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31
Q

What does the induced fit hypothesis say?

A

when a substrate binds with an enzyme, it causes the enzymes active site to change shape and form products

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32
Q

Change in shape of active site lowers activation energy and favors product formation by… (3)

A
  • Providing a favorable microenvironment for active site to attract the substrate
  • Orienting substrates correctly for the reaction to occur
  • Straining substrate bonds & stabilizing transition state
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33
Q

What are the steps of the induced fit hypothesis? (3)

A

1) The complementary shapes and weak interactions between substrate and active site lead to initial binding.
2) The enzyme and substrate change their shape to facilitate a stronger bond, favoring product formation.
3) Products are released from the active site and active site goes back to original conformation

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34
Q

Lactose

A

disaccharide produced in lactating mammals as an energy source for newborns

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35
Q

Lactase (enzyme)

A

breaks down lactose into glucose and galactose in the small intestine

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36
Q

lactose intolerance

A

inability to digest and absorb lactose that results in gastrointestinal symptoms when consumed

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37
Q

What are causes for lactose intolerance?

A

a reduction or complete loss of lactase activity

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38
Q

What happens to lactose when an individual does not have lactase?

A

lactose will pass into the large intestine, where it is broken down by bacteria

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39
Q

What are some symptoms of lactose intolerance? (4)

A
  • Abdominal bloating
  • Abdominal cramps
  • Gas
  • Nausea
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40
Q

What are treatments for lactose intolerance? (3)

A
  • Removing milk from diet
  • Add lactase to milk or take in capsule/chewable form
  • Consume lactose-free milk products (lactose-free milk is sweeter)
41
Q

Lactose-Free milk can be produced by… (2)

A
  • placing lactase from yeast directly into milk
  • attaching lactase to immobilized alginate beads and repeatedly passing milk over the enzyme
42
Q

Alginate

A

natural polymer extracted from seaweed that forms a gel beads that holds lactase

43
Q

What are advantages of using immobilized alginate beads bound with lactase for producing lactose-free milk? (3)

A
  • Enzymes are conserved and can be reused
  • high concentrations of enzymes can be used for a faster rate of reaction
  • enzymes can be recycled, reducing costs
44
Q

Where can immobilized enzymes be applied?

A

industrial practices

45
Q

What are the advantages of converting lactose to glucose and galactose? (4)

A
  • as a source of dairy for lactose-intolerant individuals
  • a means of increasing sweetness without artificial sweeteners
  • as a way of reducing the crystallization of ice-creams
  • as a means of reducing production time for cheeses and yogurts
46
Q

How is enzyme activity measured?

A

reaction rate

47
Q

reaction rate

A

products formed OR substrates used up in a given amount of time

48
Q

What happens to a graph showing the relationship between reaction rate and time when there are no enzymes present?

A

increasing reactant concentration increases reaction rate

49
Q

How does substrate concentration affects reaction rate? (2)

A
  • as ↑ substrate = ↑ reaction rate
  • reaction rate levels off when enzyme is saturated
50
Q

What can cause proteins to denature? (2)

A
  • high temperatures
  • changes in pH
51
Q

What can denatured proteins lead to?

A
  • change in active site shape
  • inability of substrate to bind to active site
52
Q

What has to be disrupted to denature proteins?

A

weak interactions

53
Q

Which weak interactions do proteins denature when disrupted? (3)

A
  • hydrogen bonds
  • ionic interactions
  • hydrophobic interactions
54
Q

What levels of protein structure are disrupted when a protein denatures? (3)

A
  • secondary
  • tertiary
  • quaternary
55
Q

Why do primary structures remain intact?

A

because it is stabilized by
covalent bonds

56
Q

Why does pH affect enzyme function? (3)

A
  • Changes in pH add or remove H+ from solution
  • Changing H+ in solution disrupts interactions between charged amino acids R groups
  • Disrupting interactions changes
    overall protein shape and active
    site shape; disrupts
    interactions between substrate
    and active site.
57
Q

optimum pH

A

pH at which the reaction rate is highest

58
Q

What are most human enzyme optimal pHs?

A

between 6-8

59
Q

Why are there varying optimal pHs for human enzymes?

A

it depends on localized conditions

60
Q

Where is pepsin located?

A

stomach

61
Q

What is the optimal pH for pepsin?

A

2-3

62
Q

Where is trypsin located?

A

small intestine

63
Q

What is the optimal pH for trypsin?

A

8

64
Q

Optimal temperature

A

temperature at which the rate of an enzyme-catalyzed reaction is highest

65
Q

What happens when an enzyme is at optimal temperature?

A

greatest number of effective collisions between substrate and active site

66
Q

What happens as temperature increases to optimal?

A

molecules move faster and collisions increase between substrates & active sites
producing more products

67
Q

What happens as temperature goes above optimal? (2)

A
  • the increased energy disrupts weak forces that determine active site shape & enzyme/substrate binding
  • enzymes start to denature
68
Q

Why would enzymes have different optimal temperatures?

A

because there are organisms that live in different environments

69
Q

What is the optimal temperature for human enzymes?

A

35-40 degrees C

70
Q

Why are human enzymes’ optimal temperature in that range?

A

the human body temp is 37 degrees C

71
Q

What other factors affect enzyme function? (2)

A
  • activators
  • inhibitors
72
Q

activators (2)

A
  • molecules or ions some enzymes require to function
  • These activate enzymes by stabilizing their shape, or by participating in the chemical reaction directly
73
Q

Inhibitors

A

molecules that reduce enzyme activity

74
Q

What are the 2 types of inhibitors?

A
  • competitive inhibition
  • noncompetitive inhibition
75
Q

Competitive Inhibitors (4)

A
  • bind to the active site
  • are similar in shape to the substrate
  • “compete” to bind to active site against substrate
  • bind to an active site reversibly (can unbind)
76
Q

How can competitive inhibition be overcome?

A

by increasing substrate concentration

77
Q

What is are examples of competitive inhibition? (2)

A
  • disulfiram
  • ethanol
78
Q

Disulfiram

A

treats chronic alcoholism

79
Q

How is disulfiram a competitive inhibitor? (2)

A
  • Ethanol is metabolized to acetaldehyde, which is further metabolized to acetate by specific enzymes.
  • Disulfiram inhibits aldehyde dehydrogenase, causing the accumulation of acetaldehyde with unpleasant side-effects
80
Q

Ethanol

A

treats methanol/antifreeze poisoning

81
Q

How is ethanol a competitive inhibitor? (2)

A
  • Normally, methanol is metabolized (broken down) and its by-products cause blindness
  • Ethanol competes with methanol for the same binding site on alcohol dehydrogenase
82
Q

Noncompetitive inhibitors (3)

A
  • bind to sites other than active sites (do not resemble substrate)
  • prevents substrate binding by causing active site to change shape
  • can’t be overcome by increases in substrate concentration
83
Q

What is noncompetitive inhibition a form of?

A

allosteric regulation

84
Q

Allosteric regulation

A

non-substrate molecule binds to a regulatory site (allosteric site) other than active site and changes enzyme shape to prevent substrate binding

85
Q

What is an example of a noncompetitive inhibitor?

A

cyanide

86
Q

Cyanide

A

causes death by preventing ATP production via aerobic respiration

87
Q

How is cyanide a noncompetitive inhibitor? (2)

A
  • binds to molecule (cytochrome c) in electron transport chain
  • When bound, the electron transport chain cannot function and ATP is not produced via aerobic respiration
88
Q

What are the rates of the chemical reactions of metabolism regulated by?

A

enzymes

89
Q

Catabolic Pathways (3)

A
  • breakdown of complex molecules into simpler, usable forms
  • involves hydrolysis of macromolecules into monomers/ digestion
  • Energy released can be stored in molecules or released as heat
90
Q

Anabolic Pathways (3)

A
  • chemical reactions that synthesize complex molecules from simpler molecules
  • involves condensation reactions and forming macromolecules from monomers
  • typically use energy
91
Q

Metabolic Pathways

A

Metabolic pathways are organized into chains or cycles of enzyme-catalyzed reactions with each step controlled by an enzyme.

92
Q

What is an example of a chain involved in metabolic pathways?

A

glycolysis

93
Q

What is an example of a cycle involved in a metabolic pathway?

A

Krebs cycle

94
Q

Why are metabolic pathways beneficial? (2)

A
  • ↑ control because of enzymes can be regulated independently
  • ↑ efficiency because it allows products to be used in multiple reactions/pathways
95
Q

Why are chemical reactions broken into steps? (2)

A
  • ↑ control because of enzymes can be regulated independently
  • ↑ efficiency because it allows products to be used in multiple reactions/pathways
96
Q

End Product Inhibition (3)

A
  • final product is inhibitor of earlier step in pathway
  • Switches off pathway when product is plentiful
  • no unnecessary accumulation of product
97
Q

What is an example of feedback inhibition?

A

synthesis of isoleucine from threonine (amino acids)

98
Q

How is the synthesis of isoleucine from threonine (amino acids) feedback inhibition? (2)

A
  • isoleucine is the allosteric inhibitor(noncompetitive) of the first step
  • as product accumulates it collides with enzyme more often than substrate does

IB HL Biology I (10 decks)

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