Lecture 2 Flashcards
(115 cards)
1
Q
What are enzymes
A
biological catalysts
- all proteins except some RNAHo
2
Q
By how much can a catalyst increase the rate of a reation
A
10^20
3
Q
Rate of reaction depends on what
A
activation energy (delta G)
4
Q
What is activation energy
A
amount of energy required to start the rxn
- puts reactant in same transition state
- lower for enzyme catalyzed rxn
5
Q
active site in enzyme catalyzed rxn
A
small portion of enzyme surface where substrate is bound
6
Q
substrate in enzyme catalyzed reaction
A
reactant binds to active site of enzyme
7
Q
enzyme substrate complex
A
held together by hydrogen bonding, electrostatic attractions, and van der waal interactions
8
Q
Lock and key model
A
substrate binds to portion of enzyme w complementary shape
9
Q
Induced fit model
A
binding of substrate induced change in conformation of enzyme that results in complementary fit
10
Q
How do enzymes work
A
- concentration of enyzme usually lower than concentration of substrate
- rate of catalyzed rxn depends on substrate concentration
11
Q
when are enzymes working at max rate
A
at saturation when all enzymes are bound to the substrate
12
Q
What factors affect rate of reaction
A
- temp
- pH
- enzyme concentration
- substrate concentration
- presence of controlling molecules
13
Q
how doe pH affect rate or rxn
A
- every enzyme is most active at particular pH
- pH influences ionization of functional group
14
Q
How does temp affect rate of rxn
A
- every enzyme has optimal temp
- increase temp = increase rate of rxn
15
Q
what happens to enzymes @ high temps
A
noncovalent bonds begin to break which affects enzyme structure and function
16
Q
at what temp do noncovalent bonds begin to break
A
50 - 55º c
17
Q
enzyme concentration and rate of rxn
A
- directly proportional
- if enough substrate, enzymes will double with wil cause Vm to double
18
Q
substrate concentration and rate of rxn
A
rate of enzyme depends on substrate concentration
- @ low substrate concentration, adding more substrate increases rate f reaction
- constant rate (vmax) is reached when enzyme is completely saturates with substrate
19
Q
the higher the Km value..
A
the lower the affinity for substrate
20
Q
the lower the Km value…
A
the higher the affinity for substrate
21
Q
Reversible inhibitor
A
substance that binds to enzyme to inhibit it, but can be released
22
Q
competitive inhibitor
A
- reversible
- binds to active site and blocks access by substrate
23
Q
noncompetitive inhibitor
A
binds to site other than active site, inhibits enzyme by chaging conformation
24
Q
irreversible inhibitor
A
substance that causes inhibition that cannot be reversed
25
competitive inhbition
substrate must compete with inhibitor for active site
- more substrate required to reach given rxn velocity
26
allosteric enzymes
oligomer whose biological activity is affected by other substances binding to it
- change the enzymes activity by altering conformation of 4 degree structureal
27
allosteric effector
substance that modifies behavior of allosteric enzyme
- can be allosteric inhibitor or activator
28
Zygomens
inactive precursos of enzyme where proteolytic cleavage of one or more covalent bonds transforms it into active enzyme
29
examples of zygomens
digestive enzymes, complement proteins, blood factors and capses in apoptosis
30
Chymotrypsinogen origin
- synthesized and stores in pancreas
31
what is Chymotrypsinogen
single polypeptide chain of 245 amino acid residues cross linked by five disulfide bonds
32
what happens when Chymotrypsinogen is secreted into the small intestine
the digestive enyzme trypsin cleaves a 15 unit polypeptide from the N terminal end to give it to pi-chymotrypsin
33
apoptotic signals
signals that initiate apoptosis - can be hormones, growth factors, viral infections, toxins, extensive DNA damage
34
what can get activated during apoptosis
proteases called caspases
35
what are regulatory proteins
when several proteins act to control the activity of other proteins in the cell
36
when are G proteins activated
during signal transduction once a hormone binds its receptor and the receptor activates the G protein
37
What is transducin
a regulatory G protein in retinal rods and cones that is involved in transduction of the visual signals
38
Isozymes
different structural forms of a protein that catalyze the same reaction
39
Cofactors
enzymes that require partners
40
prosthetic groups:
cofactors that are non-amino acid groups bound to enzymes
41
inorganic cofactors
ions permanently bound to enzymes
42
coenzymes
small carbon containing molecules - not permanently bound
43
B6 vitamins
coenzymes involved in amino group transfer from one molecule to another
- important in amino acid biosynthesis
44
What is a lipid
heterogenous class of naturally occurring organic compounds
45
are lipids soluble in water
no, they are insoluble in water, but soluble in aprotic organic solvents
46
open chain form lipids
fatty acids, triaglycerols, sphingolipids, phosphacylglycerols, glycolipids, lipid soluble vitamins, prostaglandins, leukotrienes, and thrombaxens
47
cyclic chain form lipids
cholesterol, steroid hormones, and bile acids
48
Fatty acids
unbranched-chain carboxylic acid, most commonly of 12 - 20 carbons
49
which is more rare: cis fatty acids or trans
trans
50
triaglycerols
ester of glycerol wirh 3 fatty acids
- can be hydroluzed by base to yield glycerol and soaps
- lipases are enzymes that hydrolyze esters in triglycerides
51
Phosphoacylglycerols
- second most abundant group of naturally occuring lipids - found in plant and animal membranes
52
Phospholipases
enzymes that hydrolyze specific bonds in phospholipids
53
waxes
- complex mixture if esters of long chains carboxylic acids and alcohols
- found as protective coatings for plants and animals
54
Sphingolipids
- contain sphingosine
- found in plants and animals
- abdundant in nervous system
- bares structureal similarity to phospholipids
55
Glycolipids
compound in which carb is bound to -OH of the lipid
55
What are most glycolipids derived from
ceramides
56
what are gangliosides
glycolipids with complex carb moiety that contains more than 3 sugars
57
Functions of membrane proteins
- transport substances across membrane
- act as receptor sites, and site of enzyme catalysis
57
Lipid bilayers
- polar surface of bilayer contains charged groups
- hydrophobic tails lie in the interior of the bilayer
57
Steroids
a group of lipids that have fused ring structure of 3 six membered rings, and 1 five membered rings
58
Integral proteins
embedded in lipid bilayer
59
perpheral proteins
only loosely associated with the membrane
60
Passive transport
driven by concentration gradient
61
simple diffusion
molecule or ions move through an opening
62
facilitated diffusion
molecule or ions is carried across a membrane by a carrier protein
63
active transport
substance moved against concentration gradient
64
primary active transport
transport is linked to hydrolysis of ATP or other high energy moleculee
65
example of primary active transport
Na/K ion pump
66
secondary active transport
driven by concentration gradient established by primary active transport
67
channel proteins
integral membrane proteins that form a channel
68
ion channels
channel protein with hydrophillic pores
69
when are gates in channel proteins opened
when protein is stimulated to change shape by chemical signal or electrical charge difference
70
Vitamin A
serves as site of primary photochemical reaction in vision
71
Vitamin D
regulates calcium (and phosphorus) metabolism
72
Vitamin E
serves as antioxidant, necessary for reproduction in rats and may be necessary for reproduction in humans
73
Vitamin K
has a regulatory function in blood clotting
74
Retinol
- vitamin A
-
75
What is a precursor for vitamin A
beta - carotene
76
Rhodopsin
- pigment required for vision
- active molecule is retinal reacts with the protein opsin to form rhodopsi m
77
what is the active molecule in retinal
vitamin a aldehyde
78
How does vitamin E work
as an antioxidant - traps HOO and ROO radicals formed as result of oxidation by O2 of unsaturates hydrocarbon chains in membrane phospholipids
79
What is the chemical composition of vitamin K
long unsaturated hydrocarbon side consisting of repeating isopropene units
80
What are prostaglandins
family of compounds that have 20 carbon skeleton of prostanoic acid
81
where was prostaglandin first discovered
in seminal fluid from a prostatwe
82
what is the metabolic precursor for prostalandin
arachinodonic acid (20 carbon atoms; 4 double bonds) `
83
Leukotrienes
- cmpnds derived from arachnidonic acid
- found in WBC
- consists of 3 conjugated double bonds
84
What are leukotrienes important in
constriction of smooth muscle ** ESP in lungs
85
what are carbohydrates
a polyhydroxyaldehyde or polyhyrdroxyjeton, or a substance that gives these compounds on hydrolysis
86
what are monosaccharides
a carb that cannot be hydrolyzed to a simpler carb
87
what is the general formula for a carb
CnH2nOn
* n can vary from 3 - 8 *
88
what are the simplest types of monosaccharides
trioses
89
what makes a cyclic hemiacetal
cyclization of sugars whihc happens to make interactions b/n funtional groups on distanct carbons
90
hemiketal
cyclization using C2 to C5
91
during cyclization, the carbonyl carbon is the new chiral center and becomes...
anomeric carbon
92
Sorbitol Pathway
minor pathway for glucose metabolism
- importan in uncontrolled diabetic eye where high glucose levels exist and aldose reductase activity is significant
93
What does rising level of sorbitol do
affects osmotic balance in lens which leads to a diabetic cataract
94
normal levels of glucose in the lens leads to what
aldose reductase activity is very low and very little sorbitol is formed
95
Glycoside
a carb in which -OH of the anomeric carbon is replaced by -OR
96
Glycosidic bond
bond from the anomeric carbon to the -OR group
97
Polysaccharide
when many monosaccharides are linked together
98
cellulose
- polysaccharide of glucose with Beta 1,4 glycosidic linkages
- very stable, good for structural components
99
Starch
-polysaccharide of glucose w alpha, 1-4- glycosidic linkages
- unbranched or moderately branched
- storage of glucose in plants
100
Glycogen
- highly branches polysaccharide of glucose with alpha- 1,4- glycocidic bonds and branches created by alpha - 1,6 glycosidic bonds
- storage of glucose in animals
101
Glycosaminoglycans
polysaccharides based on repeating dissacharide where one of the monomer is an amino sugar and the other has a negative charge due to a sulfate or carboxylate group
102
Heparin
natural anticoagulant
103
Hyaluronic acid
component of vitreous humor of the eye and lubricating fluid of the joint
104
Chondoitin sulfate and keratin sulfate
components of connective tissue
105
exergonic reactions
breakdown of complex molecules releases energu
106
endergonic reaction
formation of single product from smaller reactants requires energy
107
what it metabolism
sum total of the chemical reactions of biomolecules in an organism
108
anabolic reactions
complex molecules are made from simple molecules, and energy input is required
109
catabolic reactios
complex molecules are broken down to simpler ones and energy is released
110
when does ATP release a large amount of energy
when it is hydrolyzed
111
equation for the hydrolysis of ATP
ATP + H20 --> ADP + pi + free energy
112
