Lecture 4 - Molecules, Energy, and Biosynthesis Flashcards
1
Q
what are the four biomolecules
A
- lipids
- carbohydrates
- proteins
- nucleic acid
2
Q
diverse group of water-insoluble biological molecules
A
lipids
3
Q
energy stores
A
fats
4
Q
major components of membrane
A
- phospholipids
- sterols
5
Q
- sugar molecules
- polyhydroxy aldehydes and ketones with the general formula of (CH2O)n
A
carbohydrates
6
Q
most complex and most abundant organic molecules containing at least one carboxyl group and one amino group
A
proteins
7
Q
store and express genomic information
A
nucleic acids
8
Q
carries coded information
A
DNA
9
Q
arranged DNA
A
genes
10
Q
instrumental in translating the coded message of DNA into sequences of amino acids during synthesis of protein molecules
A
RNA
11
Q
process of increasing the rate of reaction with the use of a catalyst
A
catalysis
12
Q
any substance that increases rate of reaction upon addition to a certain reaction
A
catalyst
13
Q
- catalyst of biochemical reactions
- neither used up in the reaction nor do they appear as reaction products
- proteins of very specific amino acid composition and sequence
A
enzymes
14
Q
how are enzymes denatured and precipitated
A
salts, solvents, other reagents
15
Q
effect of enzymes on energy of activation
A
lower
16
Q
- kinetic energy required to bring the reactants into position to interact
- measured as the number of calories required to bring all the molecules in a mole of reactant at a given temperature to a reactive state
A
activation energy / free energy of activation
17
Q
how do enzymes hasten reactions
A
lower activatiion energy
18
Q
each enzyme is specific for a certain __
A
substrate
19
Q
example of enzyme specificity
A
- stereospecific
- single product
- specific bonds
20
Q
- reaction in which the stereochemistry of the reactants controls the outcome of the reaction
- one stereoisomer of certain reactant produces one stereoisomer of a certain product, whereas a different stereoisomer of the same reactant produces a different stereoisomer of the same product
A
stereospecific
21
Q
molecules that are chemically identical but whose functional groups are attached in different configurations around central carbon atoms
A
stereoisomer
22
Q
hydrolyses any peptide bond in which the carbonyl group belongs to a phenylalanine, tyrosine, or tryptophan residue
A
chymotrypsin
23
Q
what does chymotrypsin hydrolyses
A
- phenylalanine
- tyrosine
- tryptophan residue
24
Q
what does chymotrypsin reduce
A
- energy used up by cell
- build-up of toxic by-products
25
- highly specific nature of most enzyme
- arises from the close and complementary fit between enzymes and substrate in a special portion of the enzyme surface
- substrate can fit like a lock-and-key mechanism
active site
26
Different models of the active site
1. lock-and-key model
2. induced-fit model
27
- early theory for enzyme action
- enzyme-substrte have specific shape to fit exactly into another
lock-and-key model
28
- enzymes are flexible structures
- active site can change the shape to fit the substrate
- better, widely accepted theory
induced-fit model
29
catalytic potency of an enzyme
enzyme activity
30
number of reactions catalyzed per second by the enzyme
turnover number
31
enzymatic reaction
1. substrate to active site
2. enzyme-substrate complex (ES) formation
3. product separates from enzyme
4. free enzyme can form another ES
32
how do enzymes accelerate reactions
1. hold substrates in close proximity to enhance probability of a reaction
2. form unstable intermediate that readily undergoes second reaction
3. presence of protons donors and acceptors in active site
33
Factors affecting enzyme activity
1. temperature
2. pH
34
increase in temperature
- increase average molecular velocity
- increase no. of molecular collisions per unit
- increase probability of successful interaction
35
as velocities increase, the molecules possess __ __ __ and thus are more likely to react upon collision
higher kinetic energies
36
as temperature increases, reaction rate __ __
initially increases
37
as temperature increases further, reaction rate __
decreases
38
why does the reaction rate decrease when the temperature increases further
onset of denaturation
39
where is the reaction rate maximal
optimal temperature
40
what happens when there is drop in pH
exposes more positive sites on an enzyme for interaction with negative groups on a substrate molecule
41
what happens when there is rise in pH
binding of positive groups on a substrate to negative sites on the enzymes
42
- facilitates enzyme reactions but is not required
- small organic compounds or metals primarily used to support the action of enzymes
Cofactors
43
small organic molecules that act as cofactors
coenzymes
44
- enzyme minus its cofactor
- cannot function without its cofactor/coenzyme
apoenzyme
45
ex. of cofactors
vitamins
46
cofactor + apoenzyme
holoenzyme
47
Six major classes of enzymes
1. oxidoreductases
2. transferases
3. hydrolases
4. lyases
5. isomerases
6. ligases
48
type of reaction of oxidoreductases
oxidation-reduction
49
type of reaction of transferases
group transfer
50
type of reaction of hydrolases
hydrolysis reactions (transfer of function groups to water)
51
type of reaction of lyases
addition or removal of groups to form double bonds
52
type of reaction of isomerases
isomerization (intramolecular group transfer)
53
type of reaction of ligases
ligation of two substrates at the expense of ATP hydrolysis
54
example of oxidoreductases
lactate dehydrogenase
55
example of transferases
nucleoside monophosphate kinase (NMP kinase)
56
example of hydrolases
chymotrypsin
57
example of lyases
fumarase
58
example of isomerases
triose phosphate isomerase
59
example of ligases
aminoacyl-tRNA synthetase
60
where does the rate at which an enzymatic reaction proceeds depend on
concentrations of
- substrate
- product
- active enzymes
61
molecules that interact with enzymes (temporary or permanent) in some way and reduce the rate of an enzyme-catalyzed reaction or prevent enzymes to work in a normal manner.
Enzyme inhibitors
62
irrevirsible enzyme inhibition
toxins
63
two types of enzyme inhibition
1. competitive inhibition
2. noncompetitive inhibition
64
- caused by molecules that react directly with the active site of the enzyme
- can be reversed by an increase in substrate concentration
- most are substrate analogs
competitive inhibition
65
how is competitive inhibition reversed
increase in substrate concentration
66
- caused by molecules that bind to a region(s) of the enzyme outside the active site
- reversed by dilution or removal of inhibitor
- chemical structure typically differs from that of the substrate
noncompetitive inhibition
67
how is noncompetitive inhibition reversed
dilution or removal of inhibitor
68
regulation of metabolic reactions
1. control of enzyme synthesis
2. regulated by modulator molecules
69
how is enzyme synthesis controlled
modulation of rate of transcripton
70
when are enzyme synthesized
only when needed
71
distinct from the active site
allosteric site
72
how is enzyme activity controlled by modulator molecules
by binding to the allosteric site affecting affinity of enzyme for its substrate
73
acts as the regulatory enzyme
first enzyme
74
inhibit the activity of the first enzyme
end product of pathway
75
what is the end product of the pathway
allosteric inhibitor
76
several cation cofactors act as __ __ for some enzymes
allosteric activators
77
example of where ATP is used for
- biosynthesis
- mechanical work
- transport work
78
two kinds of energy-yielding metabolic pathways in animal tissues
1. aerobic metabolism
2. anaerobic metabolism
79
- food molecules are completely oxidized to carbon dioxide and water by molecular energy
- energy yield is far greater
aerobic metabolism
80
- food molecules are oxidized incompletely to lactic acid (lactate)
- absence of oxygen
anaerobic metabolism
81
products of aerobic respiration
- CO2
- water
- ATP
82
products of anaerobic respiration
- Mammalian muscle - lactic acid (and ATP)
- Yeast and some plants - ethanol and CO2 (and ATP)
83
net ATP produced in aerobic respiration
32 ATP molecules
84
net ATP produced in anaerobic respiration
2 ATP molecules
