Unit 7 Flashcards
(98 cards)
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
2
Q
What do the chemical reactions of our metabolism require?
A
an initial input of energy to take place
3
Q
activation energy
A
amount of energy reactants must absorb to start a chemical reaction
4
Q
How can we increase the rate of chemical reactions?
A
enzymes
5
Q
What is another name for enzyme?
A
biological catalysts
6
Q
enzyme functions (3)
A
- catalyze/speed up reactions
- mostly proteins (some RNA)
- reduce activation energy
7
Q
How do enzymes work?
A
by binding to reactants and speeding up their conversion to products
8
Q
substrate
A
reactant which binds to enzyme
9
Q
active site
A
region where substrate bind and undergoes a chemical reaction
10
Q
enzyme-substrate complex
A
temporary association between enzyme and substrate
11
Q
enzyme facts (3)
A
- must COLLIDE with reactants for binding to occur
- remain UNCHANGED after they release products
- are REUSABLE
12
Q
What types of reactions to enzymes catalyze? (2)
A
- hydrolysis
- condensation
13
Q
sucrase
A
breaks down sucrose
14
Q
proteases
A
break down proteins
15
Q
lipases
A
break down lipids
16
Q
DNA polymerase
A
builds DNA adds nucleotides to DNA strand
17
Q
What is an important characteristic of enzymes?
A
they are highly specific
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
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
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
21
Q
How are substrates held in place?
A
by weak interaction between amino acids
22
Q
What weak reaction hold substrates in place? (3)
A
- hydrogen bonds
- hydrophobic interactions
- ionic interactions
23
Q
Hexokinase
A
catalyzes first step of glycolysis (cellular respiration)
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
25
Substrates are held in the active site of hexokinase through which interaction?
Ionic
26
What about hexokinase facilitates the binding of the enzyme and its substrates?
the shape of the active site is complementary to the shape of the substrate molecule
27
Lock and Key Hypothesis (2)
- active site and substrate have complementary shapes like puzzle pieces
- enzymes specifically react with only one or a very few substrates
28
Analogy for Lock and Key Hypothesis
only the correctly sized key fits into the keyhole of the lock
29
What does the lock and key hypothesis explain phenomena wise? (2)
- enzyme specificity
- activity loss when enzymes denature/change shape
30
Why can't the lock and key hypothesis explain all experimental evidence?
in the lock and key hypothesis, the active site is not favorable to product formation
31
What does the induced fit hypothesis say?
when a substrate binds with an enzyme, it causes the enzymes active site to change shape and form products
32
Change in shape of active site lowers activation energy and favors product formation by... (3)
- 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
33
What are the steps of the induced fit hypothesis? (3)
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
34
Lactose
disaccharide produced in lactating mammals as an energy source for newborns
35
Lactase (enzyme)
breaks down lactose into glucose and galactose in the small intestine
36
lactose intolerance
inability to digest and absorb lactose that results in gastrointestinal symptoms when consumed
37
What are causes for lactose intolerance?
a reduction or complete loss of lactase activity
38
What happens to lactose when an individual does not have lactase?
lactose will pass into the large intestine, where it is broken down by bacteria
39
What are some symptoms of lactose intolerance? (4)
- Abdominal bloating
- Abdominal cramps
- Gas
- Nausea
40
What are treatments for lactose intolerance? (3)
- 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
Lactose-Free milk can be produced by... (2)
- placing lactase from yeast directly into milk
- attaching lactase to immobilized alginate beads and repeatedly passing milk over the enzyme
42
Alginate
natural polymer extracted from seaweed that forms a gel beads that holds lactase
43
What are advantages of using immobilized alginate beads bound with lactase for producing lactose-free milk? (3)
- 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
Where can immobilized enzymes be applied?
industrial practices
45
What are the advantages of converting lactose to glucose and galactose? (4)
- 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
How is enzyme activity measured?
reaction rate
47
reaction rate
products formed OR substrates used up in a given amount of time
48
What happens to a graph showing the relationship between reaction rate and time when there are no enzymes present?
increasing reactant concentration increases reaction rate
49
How does substrate concentration affects reaction rate? (2)
- as ↑ substrate = ↑ reaction rate
- reaction rate levels off when enzyme is saturated
50
What can cause proteins to denature? (2)
- high temperatures
- changes in pH
51
What can denatured proteins lead to?
- change in active site shape
- inability of substrate to bind to active site
52
What has to be disrupted to denature proteins?
weak interactions
53
Which weak interactions do proteins denature when disrupted? (3)
- hydrogen bonds
- ionic interactions
- hydrophobic interactions
54
What levels of protein structure are disrupted when a protein denatures? (3)
- secondary
- tertiary
- quaternary
55
Why do primary structures remain intact?
because it is stabilized by
covalent bonds
56
Why does pH affect enzyme function? (3)
- 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
optimum pH
pH at which the reaction rate is highest
58
What are most human enzyme optimal pHs?
between 6-8
59
Why are there varying optimal pHs for human enzymes?
it depends on localized conditions
60
Where is pepsin located?
stomach
61
What is the optimal pH for pepsin?
2-3
62
Where is trypsin located?
small intestine
63
What is the optimal pH for trypsin?
8
64
Optimal temperature
temperature at which the rate of an enzyme-catalyzed reaction is highest
65
What happens when an enzyme is at optimal temperature?
greatest number of effective collisions between substrate and active site
66
What happens as temperature increases to optimal?
molecules move faster and collisions increase between substrates & active sites
producing more products
67
What happens as temperature goes above optimal? (2)
- the increased energy disrupts weak forces that determine active site shape & enzyme/substrate binding
- enzymes start to denature
68
Why would enzymes have different optimal temperatures?
because there are organisms that live in different environments
69
What is the optimal temperature for human enzymes?
35-40 degrees C
70
Why are human enzymes' optimal temperature in that range?
the human body temp is 37 degrees C
71
What other factors affect enzyme function? (2)
- activators
- inhibitors
72
activators (2)
- molecules or ions some enzymes require to function
- These activate enzymes by stabilizing their shape, or by participating in the chemical reaction directly
73
Inhibitors
molecules that reduce enzyme activity
74
What are the 2 types of inhibitors?
- competitive inhibition
- noncompetitive inhibition
75
Competitive Inhibitors (4)
- 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
How can competitive inhibition be overcome?
by increasing substrate concentration
77
What is are examples of competitive inhibition? (2)
- disulfiram
- ethanol
78
Disulfiram
treats chronic alcoholism
79
How is disulfiram a competitive inhibitor? (2)
- 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
Ethanol
treats methanol/antifreeze poisoning
81
How is ethanol a competitive inhibitor? (2)
- 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
Noncompetitive inhibitors (3)
- 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
What is noncompetitive inhibition a form of?
allosteric regulation
84
Allosteric regulation
non-substrate molecule binds to a regulatory site (allosteric site) other than active site and changes enzyme shape to prevent substrate binding
85
What is an example of a noncompetitive inhibitor?
cyanide
86
Cyanide
causes death by preventing ATP production via aerobic respiration
87
How is cyanide a noncompetitive inhibitor? (2)
- 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
What are the rates of the chemical reactions of metabolism regulated by?
enzymes
89
Catabolic Pathways (3)
- 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
Anabolic Pathways (3)
- chemical reactions that synthesize complex molecules from simpler molecules
- involves condensation reactions and forming macromolecules from monomers
- typically use energy
91
Metabolic Pathways
Metabolic pathways are organized into chains or cycles of enzyme-catalyzed reactions with each step controlled by an enzyme.
92
What is an example of a chain involved in metabolic pathways?
glycolysis
93
What is an example of a cycle involved in a metabolic pathway?
Krebs cycle
94
Why are metabolic pathways beneficial? (2)
- ↑ control because of enzymes can be regulated independently
- ↑ efficiency because it allows products to be used in multiple reactions/pathways
95
Why are chemical reactions broken into steps? (2)
- ↑ control because of enzymes can be regulated independently
- ↑ efficiency because it allows products to be used in multiple reactions/pathways
96
End Product Inhibition (3)
- final product is inhibitor of earlier step in pathway
- Switches off pathway when product is plentiful
- no unnecessary accumulation of product
97
What is an example of feedback inhibition?
synthesis of isoleucine from threonine (amino acids)
98
How is the synthesis of isoleucine from threonine (amino acids) feedback inhibition? (2)
- isoleucine is the allosteric inhibitor(noncompetitive) of the first step
- as product accumulates it collides with enzyme more often than substrate does
