Midterm 2 Flashcards
(223 cards)
1
Q
How many carbons do monosaccharides range between?
A
3 to 8 carbons
2
Q
Most common number of carbons in monosaccharides?
A
Hexoses - 6 carbons
Pentoses - 5 carbons
3
Q
What is an Aldose?
A
Carbonyl at the end of the carbon chain
4
Q
What is a Ketose?
A
Carbonyl at any location or elsewhere
5
Q
What are chiral centers?
A
Carbons with four different substituents
6
Q
What do chiral centers partly determine?
A
the type of monossacharide
7
Q
What are the two types of chiral centers?
A
Epimers
Enantiomers
8
Q
What are Epimers?
A
Monosaccharides that only differ in configuration at one chiral center
9
Q
What are examples of Epimers?
A
glucose and mannose
10
Q
What are Enantiomers?
A
Monosaccharides that differ in configurations at all chiral centers
11
Q
What are examples of Enantiomers?
A
D- and L- glucose
12
Q
Most carbohydrates in living organisms are _____________.
A
D- isomers
13
Q
What structure do most monosaccharides have?
A
Cyclical structure
— ≥ 4 Carbons have cyclical structure
— they are not written as straight chains
14
Q
In monosaccharides, what are the two forms of anomers
A
ß anomer (beta)
∂ anomer (alpha)
15
Q
What are ß anomers?
A
-OH of anomeric carbonyl C up
- same side as C-6
16
Q
What are ∂ anomers?
A
-OH of anomeric carbonyl D down
- Opposite side from C-6
17
Q
Why learn about ∂ vs. ß anomers?
A
Anomeric configuration determines structural properties.
—— Example:
- Starch (good for eating) = contains ∂- glucose
- Cellulose (good for wearing) = contains ß - glucose
18
Q
What is Pyranose?
A
5 carbons + 1 oxygen ring
Example: glucopyranose (glucose)
19
Q
What is Furanose?
A
4 carbons + 1 oxygen in ring
Example: fructofuranose (fructose)
20
Q
What structure do most monosaccharides have?
A
Cyclical structure
— ≥ 4 Carbons have a cyclical structure
— they are not written as straight chains
21
Q
Since some monosaccharides are reducing sugars, What are reducing sugars?
A
- Easily reduce copper ions and other compounds
- Sugar is itself oxidized during the process - The site of oxidation is the anomeric carbon (carbonyl)
- Oxizided to carboxyl
+ Example: glucose (carbon 1)
22
Q
Why are reducing sugars introduced or important?
A
- They are important for detecting sugars + historically in detecting diabetes.
- in detecting sugars, an oxidizing agent that turns color when reduced
- Common agent: 3,5 dinitrosalicylic agent (easy way to detect glucose in the sample)
— old way of detecting diabetes would be Drs. tasting urine
23
Q
Monosaccharides have many derivatives, what are the four derivatives talked about in class?
A
- Amino Sugars (-OH to -NH2)
- Deoxy Sugars (-OH to -H)
- Acidic Sugars (-CH2OH to -COO-)
- Sugar Phosphates (-OH to -OPO3^2-)
24
Q
What are the building blocks for more complex carbohydrates?
A
Monosaccharides
25
Simple Sugar
Monosaccharide
26
2 Monosaccharides
Disaccharides
27
Oligosaccharides
3 to ~9 monosaccharides
28
Many monosaccharides (~10 or more)
Polysaccharides
29
How are Disaccharides formed?
Formed when anomeric carbon of one monosaccharide is linked with another monosaccharide
30
What is the linkage called in forming a disaccharide?
glycosidic bond
Example: condensation reaction (forming water)
31
What are the Common Disaccharides?
- Maltose (from starch)
- Lactose (from milk sugar)
- Sucrose (from photosynthesis) - storage in plants
- Cellobiose (from cellulose)
32
How are glycosidic bonds named?
- position of carbons involved
- anomeric configuration of the carbons
Example: Glc (∂1-->4) Glc
33
What is the glycosidic bond of Maltose
Glc (∂1-->4) Glcq
34
What is the glycosidic bond of Cellobiose?
Glc (ß1-->4) Glc
35
What is the glycosidic bond of Sucrose?
Glc (∂1 <-->ß2) Fru
36
What is the glycosidic bond of Lactose?
Gal (ß 1---> 4) Glc
37
What kind of arrow would it be if there are 2 anomeric carbons?
<––>
38
What kind of arrow would it be if there is 1 anomeric carbon?
––>
39
What is a reducing end?
- End of a disaccharide with a free anomeric carbon
- Detectable with DNS or oxidizing agent
- It is not present in all disaccharides
40
What is an example of a reducing end?
Sucrose
- Resistance to oxidation makes sucrose good storage compound in plants
41
Why are polysaccharides important biomolecules?
Location of most carbohydrates in organisms
42
What is the most abundant biomolecule on Earth?
Cellulose
43
What is the second most abundant biomolecule on Earth?
Chitin
44
Since polysaccharides take on many forms, What are the structural classes?
- Homopolysaccharides
- Heteropolysaccharides
- Branched
- Unbranched
45
What type of structural class of polysaccharide is made out of single monosaccharides?
- Simplest and made out of a straight chain
Homopolysaccharides
46
What type of structural class of polysaccharide is made out of different monosaccharides?
Heteropolysaccharides
47
What type of structural class of polysaccharide is made out of single monosaccharides?
Homopolysaccharides
48
What type of structural class of polysaccharide is made out of either homo/hetero-polysaccharides that are branched?
Branched
49
What type of structural class of polysaccharide is made out of either homo/hetero-polysaccharides that are in a straight chain?
Unbranched
50
What are examples of polysaccharides that are used for storage?
- Starch, Glycogen and Fructan
51
What are the two components of starch?
Amylose - unbranched Glc(∂1-->4) Glc
(homopolysaccharides)
Amylopectin - Glc(∂1-->6) Glc branches every 24 to 30 residues
- similar to amylose
-branched polysaccharide
52
What is Corn Starch made out of?
24% amylose and 76% amylopectin
53
Where is starch found?
Found in plant endosperm
-- seed tissue containing starch granules in grains
-- protein matrix surround starch granule
54
Glycogen is ......
- similar structure ti amylopectin but more frequent branching (every 8 to 12 residues)
- found in animal liver and muscle
- also found in microbes
55
Why store glucose in polysaccharides?
- Protects cells from high osmolarity
- Glycogen in human liver
- if hydrolyzed, it would form concentrated (0.4M) glucose solution and it would burst the cell
56
Fructan is .....
Fru (ß2-->6) Fru and Fru (ß2-->1) Fru
Found in plants
Slightly to highly soluble
Up to 30% of grass dry weight --- good source of carbs for herbivores
57
What are examples of polysaccharides that are used in structural forms?
Cellulose, Hemicellulose, Pectin,ß- glucan, Chitin, Peptidoglycan, and Agarose
58
Cellulose have the following characteristics
- Unbranched Glc(ß1--> 4)Glc
---- identical to amylose, except the ß linkage
- Tough, insoluble and indigestible
- Found in cotton, plant cell wall (with other polysaccharides
59
What are the components of the plant cell wall?
- cellulose
- pectin
- hemicellulose
- ß- glucan
60
Hemicellulose has.....
- Xylose core: Xyl(ß1-->4)Xyl
- Branches that include arabinose and other sugars
---- similar to glucose + branched heteropolysaccharide
61
Pectin has.......
- Galacturonic acid core: GalA (∂1-->4) GalA
- Branched that include arabinose, galactose and other sugars
62
ß-glucan........
- Glc(ß1-->4)Glc CORE with Glc(ß1-->3)Glc
- Found in plants and microbes
63
Plant cell wall is
- Indigestible by mammalian enzymes
- Digested by Gastrointestinal microbes (bacteria in cows rumen) and some arthropods
64
Chitin
- Unbranched N-acetylglucosamine: GlcNAc(ß1-->4) GlcNAc
- found in exoskeletons of arthopods
- second most abundant biomolecule on Earth (after cellulose)
65
Peptidoglycan
- Unbranched N-acetylglucosamine and acetylmuramic acid: GlcNAc(ß1-->4) Mur2Ac
- contains (crosslinked to) peptide side chain
-found in cell wall of bacteria
- broken down by lysozyme (in human tears = antibacterial)
66
Agarose
- Make up of D- galactose and an L-galactose derivative
- contains charged groups (sulfates and pyruvate)
- red algae
- used in gel electrophoresis
67
"Other" functional class of polysaccharides
glycosaminoglycans
68
What are Glycosaminoglycans?
-Polysaccharides from the extracellular matrix of animals
(extracellular matrix =space between cells)
- made of alternating acidic and amino sugars
- some contain charged groups (sulfates), forcing an extended configuration
Example: chondroitin sulfate
- do not exist in free form
- they are attached to proteins to form proteoglycans
69
Role of glycosaminoglycans in cells
Adhesion
Recognition
signaling
70
_____________ are covalently attached to glycoproteins
Oligosaccharides
71
Oligosaccharides are
- rare, except when attached to proteins
- Glycosylation = attachment
- proteins forms are glycoproteins
---> common in mammals = 50% of total proteins
72
What are glycoproteins?
- oligosaccharides that are short and highly branched
- acetylated residues (e.g., N-acetylglucosamine) common
- Carbohydrate - protein linkages involves the following:
---> Sef/Thr or Asn on protein
---> O- or N- on oligosaccharide
73
Examples of glycoproteins
Mucin
- component of mucus
- hold water and form gels
74
Glycoproteins are recognized by
- viruses
- toxins
- bacteria
- other mammalian cells (leukocytes)
!!! important to virulence and immunity
75
Lipids are __________
structurally diverse
76
What the definition of a lipid
- Biomolecules that are soluble in organic solvents.
= ether, benzene, chloroform
- no other shared feature
77
What are the two classifications of lipids
- lipids that contain fatty acids
- lipids that do not contain fatty acods
78
What are examples of lipids that DO have fatty acids?
- Fatty acids
- Triacylglycerols
- Waxes
- Membrane lipids
79
What are examples of lipids that DO NOT contain fatty acids?
- Sterols
- Fat soluble vitamins
- Pigments
- Polyketides
80
What is the major class of lipid?
Fatty acid
81
Fatty acid is made of?
Carboxylic acids with hydrocarbon chains between 4 to 36 carbons
- Saturated = no double bonds
- Unsaturated = one or more double bonds
82
Nomenclature (lipid number)
- Palmitic acid
- Oleic acid
83
Palmitic acid has (16:0)
(16:0) = 16 carbons with 0 double bonds
84
Oleic acid
(18:1 cis -9) = 18 carbons with 1 double bond in cis configuration beginning at carbon 9
85
Omega 3
- double bond at 3rd carbon from end of the chain
86
how to write the lipid number
- lipid number could be written as 18:3(n-3)
- could also be written as 18:3 all cis-9,12,15
87
An example of an Omega 3 is required in the diet
- ∂-linolenic acid
- Eicosapentaenoic acid (EPA)
- Docosahexaenoic acid (DHA)
88
∂- linolenic acid
cannot be synthesized
- animals lack desaturase enzymes to form the unsaturated bonds
89
Eicosapentaenoic acid (EPA) (20:5 n-3)
- can be synthesized from ∂-linolenic acid to form the unsaturated bonds
- otherwise required in diet
90
Docosahexaenoic acid (DHA) (22:6 n-3)
same as EPA
91
What would happen if there is a deficiency in Omega 3
dermatitis, skin lesions, poor growth, reproductive failure
92
Omega - 6
- double bonds at 6th carbon from the end of the chain
93
Examples of Omega-6 that are required in the diet
- Linoleic acid
- Arachidonic acid (AA) (20:4 n-6)
94
Arachidonic acid (AA) (20:4 n-6)
- if not enough linoleic acid available as a precursor
- Always required in cats
Cats lack enzymes to synthesize from linoleic acid
95
Where can Omega 3 and 6 be found
Fish oil
96
Conjugated linoleic acid
- Family of 28 isomers of linoleic acid
- conjugated double bonds
- alternating between single and double bonds
- formed in rumen by microbes
---- the process is known as biohydrogenation
97
What is Cis configuraton
same side of double bond
98
What is trans configuration
opposite side of the double bond
99
Melting point
- Decreases as the number of unsaturated bonds increases
- Decreases as the chain length decreases
100
Why does the melting point decrease as the number of unsaturated bonds increases?
- This is especially for unsaturates bonds in cis configuration
---- the kinks prevents close packing of fatty acids
101
_________________ store fatty acids
Triacylglycerols
102
What is a Triacylglycerol?
- ester of glycerol and fatty acids
- it is the location of most fatty acids in cells
103
Triacylglycerol is/are
- Major form of energy storage in plants and in animals
- Used over polysaccharides because of fatty acids
104
Why are triacylglycerols used over polysaccharides ?
because fatty acids:
- are more reduced carry more energy per carbon
- are nonpolar and carry less water per gram
105
________________ store fatty acids and repel water?
Waxes
106
What are waxes
- Ester of long-chain fatty acids with long-chain alcohols
- Insoluble and have high melting points
107
Functions of waxes
Storage of fatty acids in plankton
Protection and pliability for hair and skin in vertebrates
Waterproofing of feathers in birds
Protection from evaporation in plants
--- useful as lotions, ointments, and polishes
108
________ lipids that envelopes cells
Membrane Lipids
109
Components of membrane lipids
- phospholipids
- glycolipids
- archeal ether lipids
110
Phospholipids
- a similar structure to triacylglycerols
-- one fatty acid is substituted with the polar head group
- Backbone may or may not be glycerol
- Has a polar head group - contains phosphate and it may contain other constituents as well
111
What is the backbone of glycerophospholipids?
Glycerol
112
What is the backbone of sphingolipids?
Sphingosine
113
What are the two phospholipids?
- Phospohotidylcholine
- Sphingomyelin
114
Phospohotidiylcholine
- glycerpphosophilid (glycerol back bone)
- has a phosphocholine head group
- one fatty acid = unsaturated
- major membrane lipid for animals
- absent in most bacteria - lack enzymes for synthesis
115
Sphingomyelin
- sphingolipid
- like phosphotidylcholine, it has a phosphocholine head group
116
Glycolipids have
- similar structure to phospholipids but its polar head group is a carbohydrate NOT phophate
117
Examples of a Glycolipid
- Galactolipids
- Glycosphingolipids
118
What are Galactolipids?
- Polar head group is one or two galactose residues
- major membrane lipid in plants ( very important in plants)
119
What are Glycophingolipids?
- its polar head group is an oligosaccharide
- it determines the blood type
---> O antigen - Type O blood
---> B antigen - type B blood
---> A antigen - type A blood
- Difference is only due to a single residue
--- A antigen has an extra N-acetylgalactosamine
--- B antigen has an extra galactose
120
In glycosphingolipids, A antigen has an extra ________________.
extra N- acetylgalactosamine
121
In glycosphingolipids, B antigen has an extra _________________.
extra galactose
122
Archeal ether lipids
- Found in archaea
- have unusual structures
- have Diphytanyl groups
123
Why do Archaeal ether lipids have an unusual structure?
- does not contain fatty acids --> hydrocarbons is instead diphytanyl
- contains three glycerol residues ++ one is a head group and the other two are linked to the diphytanyl hydrocarbons
- linkages are ether --> not amides or ester
124
What is a Diphytanyl group?
- Long (32 carbons) and span the entire membrane
------ do not form lipid bilayer found in most organsims
125
What are the reasons why Archaeal ether lipids have an unusual structure?
- more stable under low pH and hot environments of some archaea
---- ether linkage are more resistant to hydrolysis than ester
---- the lipid "unilayer" they form is more stable than a bilayer
126
Lipids
diverse biomolecules that only share one feature (solubility in organic solvents)
127
Fatty acids are
Building block of many lipids
128
Triacylglycerols, waxes, and membrane lipids differ in
structure and roles
129
What are examples of lipids that do not contain fatty acids?
- sterols
- fat soluble vitamins
- pigments
- polyketides
130
What lipid that does not contain a fatty acid contain a fused ring?
Sterols
131
What is a steroid nucleus?
rings that make up structure
132
Steroid nucleus has
3 rings with 6 carbons
1 ring with 5 carbons
structure is flat (planar) and rigid
133
Sterols have
a polar head group (hydroxyl group) and nonpolar side chains (alkyl side chain)
134
what are the types of sterols?
- cholesterol
- steroid hormones
- bile acid
- vitamin D precursor
135
Cholesterol
- most abundant sterol in animal tissue
- component of cell membranes = controls fluidity in the membrane
- can be obtained from the diet or synthesized in liver
- transported in the blood via lipoproteins
136
Lipoproteins include
HDL (good) and LDL (bad)
137
Steroid hormones
- Examples: estrogen and testosterone
- do not contain an alkyl side chain = more polar than cholesterol
- synthesized from cholesterol in gonads and adrenal glands
- Carried through the body ain the bloodstream, usually attached to carrier proteins
- many are sex hormones or reduce inflammation
138
Other examples of sterols
testosterone, ß- estradiol, cortisol, prednisone, aldosterone, prednisolone, brassinolide
139
What are bile acids?
- Secreted by the gallbladder
- emulsifiers (breaks up) fat droplets during digestion in small intestines
140
Why do bile acids have to break down fat droplets?
- fats need to be broken up so that enzymes can attack it
141
What are fat soluble vitamins?
- includes vitamins A,E,D & K
- they have range of structures == the only shared feature is that they are fat soluble
142
Vitamin D
- sterol
- precursor ( 7-dehydrocholesterol) synthesized from cholesterol
- Synthesis of active form (calcitriol) is completed by
- UV light in skin
- Hydroxylation in liver and kidneys
143
Where can Vitamin D be synthesized by
uv light
hydroxylation in liver and kidneys
144
What are the functions of Vitamins D
- Elevates plasma Ca ( and P)
- Mechanism
- stimulates intestinal absorption
- bone resorption
- Kidney tubular reabsorption
145
What are the deficiency signs of Vitamin D?
- skeletal deformities (rickets in children) + in adults weak bones
146
Vitamin A has different forms
retinol (alcohol form)
ß- carotene ( 2 vitamin A molecules joined)
Others
147
What are the functions of vitamin A?
- normal night vision due to its role in formation of rhodopsin (pigment in rod photoreceptors of the eye)
- hormone-like growth factor
148
Deficiency signs of Vitamin A
- poor night vision
149
What vitamin is toxic in high amounts?
Vitamin A - don't eat polar bear liver
150
What is the structure of VItamin E?
most active form is ∂-tocopherol
151
What are the functions of Vitamin E
free radical scavenger/ antioxidant
152
What are the deficiency signs of vitamin E?
Nutritional muscular dystrophy ( weakness and awkward gait)
153
What is the structure of Vitamin K
Major forms
K1 (phylloquinone) - plant
K2 (menaquinone) - animals
Synthetic form
K3 (menadione) - synthetic
154
What are the functions of Vitamin K?
- normal blood clotting
---- involved in enzyme systems for the synthesis of prothrombin (factor II) and other clotting factors (IX, VII, X)
155
What are the deficiency signs of Vitamin K?
- prolonged clotting times, hemorrhage and death
156
Vitamin K is illustrated in ___________
Rat poison - vitamin k antagonist --- it kills rats because it interferes with the function of vitamin K
---- if they fall off the table and suffer from a small injury they will bleed to death
Heart disease patients get warfarin - low dose of rat poison -- decreases blood clotting
157
Natural pigments
- have conjugated dienes = double bonds separated by a single bonds
158
Natural pigments
- pigments have conjugated dienes = double bonds separated by a single bond
159
What are conjugated dienes?
- excite by visible light and produce color
160
____________ are secondary metabolites with medicinal uses
Polyketides
161
What are polyketides?
lipids synthesized via reaction called Claisen reaction
162
What is Claisen condensation reaction?
- Same reaction used to synthesize fatty acids
- lipids that are synthesized like fatty acids but are NOT fatty acids
163
Polyketides are
secondary metabolites = metabolites are not essential to life but still beneficial
- medicinal properties
164
Example of polyketide medical properties
Erythromycin (antibiotics)
Lovastatin (statin)
Amphotericin B (antifungal)
165
Why are enzymes important?
- Metabolism is impossible with enzymes
- Enzymes are catalysts
- They have high specificity
- they can be regulated
- they are effective under mild (physiological) conditions
166
Enzymes are catalysts, what does this mean?
they speed up reactions to useful rates 10^5 vs 1
10^5 is faster than 1
167
Enzymes have high specificity, what does this mean?
they carry out the reaction intended, not other, due to active site
168
T/F: Most enzymes are proteins
TRUE
169
When were enzymes first discovered?
late 1800s/ early 1900s
170
What did Eduard Buchner do?
Yeast carry out fermentation even when cells are broken apart
- molecules (enzymes) inside yeast must be responsible
-- vitalism is wrong
Zymase - breaking down cells
171
What did James Sumner do?
- he purified one enzyme (urease) and showed it was entirely protein
-other investigators also showed other enzymes were protein
172
How many amino acids per enzyme?
around 100 to 10,000
173
Since enzymes also have cofactors, what do cofactors mean?
non-amino acids molecules required for activity
174
What are the types of cofactors?
Inorganic ions and Organic molecule
175
What are the inorganic ions?
Fe 2+ (iron)
Mg 2+ (magnesium)
Mn 2+ (manganese)
Zn 2+ (zinc)
176
What are the organic molecules (coenzymes)
- mostly vitamins
- carry functional groups during reactions
177
what is a holoenzyme?
Enzyme + cofactor
178
What is an Apoenzyme?
Enzyme alone
179
What are Ribozymes?
- involved in gene expression
180
example of a ribozyme?
rRNA= Ribosomal RNA
= catalyzes the synthesis of protein
181
How are enzymes classified?
by the reactions they catalyze
182
when there are only a few enzymes known naming was easy
like urease
183
Things got more difficult as more enzymes were discovered (21 enzymes were urea
sol: classify and name enzymes by the reactions they catalyze
Example: hydrolase
urea is now named urea amidohydrolase
184
What does hydrolase do?
Carry out hydrolysis reaction
185
What are the 7 classes in classifying enzymes?
1. Oxidoreductases - transfer electrons
2. Transferase - group transfer reactions
3. Hydrolases - hydrolysis reactions
4. Lyase -
5. Isomerase
6. Ligase
7. Translocases
186
EC means
Enzyme commission number - unqiue number ID for enzymes
187
What is the first number in EC. 3.5.1.5 indicate?
3 is the class number
188
What is the last three numbers in EC. 3.5.1.5 indicate?
5.1.5 are the Subclasses
189
_________ affect reaction rate, not direction
Enzymes
190
How do catalysts increase rate of reaction?
- lowering activation energy (∆G dagger)
- they cannot change the total energy released (∆G)
---- they do not make unfavorable reactions more favorable
191
How does enzymes start a reaction?
Enzymes bind to substrates to start reaction and they continue to bind as substrates transformed into products
192
Where does binding happen?
All binding occurs in active site
---> has amino acids complementary to substrates, intermediates and product
- this gives enzymes their specificity
193
What does binding do?
Lowers activation energy --> faster reaction rate
194
Transition state
is even more important than binding to a substrate
195
How can you tell when a reaction can proceed?
- bringing substrates to the transition state
196
Why is it important to lower the activation energy is there are multiple substrates?
It brings them closer proximity
197
What are the specific catalytic groups that contribute to catalysis?
1. Acid-base
2. Covalent
3. Metal ion
198
what does acid-base catalysis do?
proton transferred from enzyme to reactants and vice versa
199
What does Covalent Catalysis do?
- transient covalent bond formed between enzyme and substrate
- changes the reaction pathway
- uncatalyzed A-B --> A+B
catalyzed (X: = nucleophile catalyst) A-B+X: --> -X+B---> A+B + X:
- requires a nucleophile (X:) on the enzyme
Example: neg charged oxygen (O-) that can form on serine
200
Metal Catalysis
- involves a mnetal ion bound to the enzyme
- interacts with substrate to facilitate binding
- stabilizes negative charges
- participates in oxidation reactions
201
Chymotrypsin
breaks down dietary proteins to peptises during digestion
uses both acid-base catalysis + covalent catalysis
202
Step 1: substrate enters
- peptide enters and is bound to the enzyme ( at the hydrophobic pocket)
203
step 2: Colavent catalysis
Enzyme (Ser 195) forms covalent bonds with peptide (at carbonyl group)
- enzyme (His 57 and Gly 193 ) stabilize transition state by hydrogen bonding to peptide
204
step 3 Acid base catalysis
- Enzyme (His57) donates proton to peptide
- Protonation cleaves peptide bond
- Product 1 (shortened peptide) leaves
205
step 4 water enters
water enters enzyme active site
206
step 5 cont acid base catalysis
- Water donates a proton to enzyme (His57) to replace proton at step 3
- hydroxyl is leftover and this attacks enzyme-substrate complex (ester linkage)
207
step 6 cont covalent catalysis
covalent bond between peptide and enzyme (ser 195) is broken
208
step 7 product 2 leaves
- Product 2 (the shortened peptide) is replaced
- Free enzyme is regenerated
209
Enolase
- removes water during glycolysis
- uses acid-base and metal catalysis
210
Step 1 acid base and metal catalysis
- Substrate (2-phosphoglycerate) enters
- Enzyme (Lys345) accepts proton
- Metal ion (Mg2+) stabilizes intermediat
211
step 2 Acid base and metal catalysis cont
- Metal ion (Mg2+) continues to stabilize intermediate
- Enzyme (Glu211) donates proton to intermediate
- Product (phosphoenolpyruvate) and water leave
212
What are the factors that affect the rates of enzymatic reactions?
- enzyme concentration
- substrate concentration
- Modulators and concentration
- temperature
- pH
213
What is the study of reactions and the factors affecting them called?
Enzyme kinetics
214
What is the most important part in doing experiments when determining the rate of reaction?
Initial rate
215
Why is the initial rate important?
The substrate is still at concentration added by the experimenter.
216
What is the relationship between initial rate and concentration called?
Michaelis- Menten Kinetics
217
What are the two parameters in Michaelis-Menten kinetics?
V max = maximal rate of reaction
Km = substrate concentration at 1/2 Vmax
218
What is the simple equation in michaelis menten kinetics?
v = (Vmax [S]) / (km+ [S])
219
what is Vmax?
unit is mol L^-1 s^-1
higher value = faster the rate
220
Under Vmax, what is the enzyme concentration is known (kcat)?
Kcat = Vmax/ [E]
221
Why is Kcat better than Vmax?
it accounts for different concentrations of enzymes across experiments
222
What is the unit for kcat?
s^-1
223
Km
units: mol L^-1
higher value, the slower rate
Does not affect the rate of substrate concentration is very high (v = V max)
