Lecture 1 Flashcards
(126 cards)
1
Q
Isoform
A
Proteins that perform the same function but have different primary structures
2
Q
Isozymes
A
Proteins isoforms that function as enzymes recall that isoforms are proteins that perform the same function but have different primary structures
3
Q
Protein folding is…
A
A complex trial and error process that sometimes results in improper folding
4
Q
What happens to misfolded proteins?
A
They are usually tagged and degraded by the cell however sometimes the aggregates of misfolded proteins can accumulate especially as we age— causing diseases
5
Q
Misfolding of proteins can cause what diseases?
A
Amyloid and prion diseases
6
Q
Amyloid disease (protein misfolding)
A
Disease where there is an accumulation of insoluble spontaneously aggregating misfolded proteins called amyloids consisting of beta pleated sheets
7
Q
Examples of amyloid diseases
A
Alzheimer’s and Parkinson’s (neurodegenerative)
8
Q
Prion disease (protein misfolding)
A
Disease caused by the prion protein (PRP), infectious PRP is highly resistant to proteolytic degradation and tends to form insoluble aggregates of fibroids similar to the amyloid found in some other diseases of the brain
9
Q
Examples of prion diseases
A
TSE (spongiform), scrapie in sheep, creutzfeldt jakob in people, bovine spongiform in cattle
10
Q
Creutzfeldt Jakob disease
A
Prion disease in humans
11
Q
Scrapie
A
Prion disease in sheep
12
Q
Bovine spongiform encephalopathy
A
Prion disease in cattle (mad cow disease)
13
Q
Non-infectious prion protein
A
Prp C (prion protein cellular)
14
Q
Infectious prion protein
A
Prp Sc (prion protein scrapie)
15
Q
Prp Sc does what to make it infectious?
A
It induces a 3-D confirmational change in prion proteins cellular (prp C) resulting in resistance to degradation
16
Q
Where is Prp C?
A
It is found in cell membranes and seems to play an important role in the brain
17
Q
What are specialized group of proteins that contain the prosthetic group heme?
A
Hemoglobin and myoglobin
18
Q
Heme _______ binds oxygen
A
Reversibly
19
Q
Structure of heme
A
Iron can form six bonds four with nitrogen and two additional bonds one above and one below the porphyrin ring; above iron binds oxygen and below iron binds histidine
20
Q
In globular proteins, heme ________ binds
A
Reversibly
21
Q
Where is myoglobin found?
A
Heart and muscle
22
Q
What are the two myoglobin functions?
A
- It is a reservoir for oxygen
- An oxygen carrier that increases the rate of transport of oxygen within the muscle cell
23
Q
Myoglobin consists of
A
A single polypeptide chain
24
Q
What makes tissues red?
A
Myoglobin
25
Where is hemoglobin found
RBCs
26
Hemoglobin main function
Transport oxygen from the lungs to the capillaries of tissues
27
Hemoglobin can transport
Hydrogen and carbon dioxide from tissues to the lungs as well
28
How many molecules of oxygen can hemoglobin transport from the lungs to the cells?
4
29
How many molecules of oxygen can myoglobin bind?
1
30
Hemoglobin A (the main hemoglobin in adults) is composed of…
4 polypeptide chains: 2 alpha and 2 beta chains held together by noncovalent interactions
31
What kind of interactions hold together for two alpha and two beta chains in myoglobin?
Non covalent
32
Oxygenated form of hemoglobin
R or relaxed state
- ionic or hydrogen bonds broken
33
Deoxygenated form of hemoglobin
T or taut state (more bonds in this state)
- hydrogen bonds form and hydrophobic pull together
34
The oxygen dissociation curve of hemoglobin has what shape?
Sigmoidal
35
What is cooperative binding
As the first oxygen binds to the hemoglobin the binding of additional oxygen to the same molecule is enhanced
36
Where is hemoglobin quickly saturated?
In lungs where o2 is high
37
What happens to hemoglobin in tissues depleted of oxygen?
Hemoglobin gives up half its oxygen
38
__________ Has a greater affinity for oxygen causing oxygen to move from blood to muscle
Myoglobin
39
When does myoglobin give up oxygen?
Only when muscle cell oxygen is very low such as during strenuous exercise
40
The Bohr effect
The effect of a change in the oxygen binding affinity of hemoglobin due to the binding of other ligands to hemoglobin
41
What do the Ligands do in the Bohr effect?
The leg and stabilize the taut state a.k.a. the deoxygenated form
42
Is the deoxygenated form the taut or relaxed state?
Taut
43
Increase H (lower pH)
Decrease affinity for O2
44
Increase 2,3 BPG
Decrease affinity for O2
45
Increase CO2
Decrease affinity for O2
46
What happens when carbon monoxide binds to one or more of the heme sites?
Hemoglobin shifts to the R state causing the other heme sites to buy in to oxygen tightly
47
What does Carbon monoxide do for oxygen affinity
Increases (extreme) it… Hb won’t let go of oxygen to tissues
48
Family genetic disorders caused by the production of
1. Structurally abnormal hemoglobin molecule
2. Insufficient quantities of normal hemoglobin
3. Both (rare)
49
Examples of hemoglobinopathies
Sickle cell anemia (Hb S)= val instead glu
Hemoglobin C disease = lys instead of glu
Hemoglobin SC disease= both above
Thalassemia= decreased normal hemoglobin
50
Fibrous proteins typically contain what
Regular secondary structural elements mostly structural proteins
51
Fibrous proteins are mostly
Structural
52
Structural proteins are mostly
Functional
53
Examples of fibrous proteins
Collagen, elastin, keratin
54
What is the most abundant protein in the human body?
Collagen
55
Collagen is composed of
Three polypeptide helices that are twisted around each other to form a right handed triple helix
56
There are more than ___ collagen types but most of them are type ____
25, 1
57
Collagen type one is found in what?
Teeth bone skin and tendons
58
What is the amino acid composition of collagen?
Glycine, proline, 4 hydroxyproline, 3 hydroxyproline, 5 hydrolysine
59
What is present in collagen but not present in most other proteins?
Hydroxyproline and hydrolysine
60
Biosynthesis of collagen
1. Nucleus
2. Translated then enters RER
3. Proline and lysine residues hydroxylated
4. Hydroxylysine residues are glycosylated
5. Three pro alpha chains assemble
6. Triple helix (pro collagen) formed and enter golgi
7. Secrets into ECM
8. Tropocollagen formation
9. Multiple tropocollagen forms collagen by cross linking
61
Name two collagen defects
1. EDS- fragile skin and joints
2. OI- bones bend and fracture
62
What is elastin?
A connective tissue proteins with rubber like properties
63
Where are elastin fibers found?
Lungs, walls of large arteries and elastic ligaments
64
How does elastin stretch?
It can be stretched several times the normal length but recoil to the original shape when the stretching force is relaxed
65
Keratin is made of what?
Alpha helical polypeptides
66
keratin is found in
Hair, wool, skin, horns
67
Enzymes
Protein catalyst that increase the rate of reactions without being changed in the overall process
68
RNA with catalytic activity
Ribozymes
69
How many kinds of enzymes?
6
70
Oxidoreductase
Redux rxns (alcohol dehydrogenase)
71
Transferase
Add groups (hexokinase)
72
Hydrolase
Chymotrypsin
73
Lyase
Lyse or break apart (pyruvate decarboxylase)
74
Isomerase
D to L (alanine racemase)
75
Ligase
Join or add (pyruvate carboxylase)
76
What are additional enzyme classes?
Synthase, phosphatase, phosphorylase, kinase
77
Synthase
Catalyzes a synthesis process
78
Phosphatase
Removes a phosphate group
79
Phosphorylase
breaks bond by using inorganic phosphate PI (adds phosphate)
80
Kinase
Adds a phosphate group from a high energy molecule such as ATP
81
Oxidase
catalyzes oxidation reduction reactions using oxygen as the electron acceptor but oxygen atoms are not incorporated into the substrate… they remove electrons and make it positive
82
Oxygenase
Oxidize a substrate by transferring oxygen atoms to it
83
Enzymes have an active site which contains…
Amino acids side chains that participate in substrate binding and catalysis
84
What is the efficiency of enzymes?
10^3-10^8 times faster
85
Enzymes are _____
Specific (only one type of reaction with one or few substrates)
86
What does it mean to say enzyme activity can be regulated?
Increased or decreased
87
Where are most enzymes located?
Specific organelles within a cell
88
Holoenzyme
Enzyme with its non-protein component (active)
89
Apoenzyme
Enzyme without its non-protein component (inactive)
90
Cofactor
Non-protein moiety that is in organic or organic of the enzyme
91
Coenzyme
non-protein small organic molecule frequently derived from vitamins such as NAD plus and FAD
92
Prosthetic group versus co-substrate
A prosthetic group refers to coenzymes that are permanently associated with an enzyme while cosubstrate refers to coenzymes that are only transiently associated with the enzyme
93
Allosteric enzymes
Can be activated or inhibited
94
An Apoenzyme, coenzyme and cofactor are all considered what?
Holoenzyme
95
Organic
Coenzyme
96
In organic
Cofactor
97
Chemical reactions have an energy barrier called what?
The free energy of activation and it has the energy difference between that of the reactants and a high energy intermediate that occurs during the formation of the product
98
Free energy of activation
Energy difference between the reactants (starting material) and a high energy intermediate (transition state) that occurs during the formation of the product
99
What must be overcome for molecules to react?
Sufficient energy to overcome the transition state
100
What does an enzyme do?
Lowers the free energy of activation
101
What factors affect reaction velocity?
Substrate concentration, temperature, pH
102
Increased substrate concentration does what to an enzyme catalyzed reaction?
Increases the rate of the reaction until the max velocity is reached
103
Most enzymes follow the Makaylas Menton kinetics hyperbolic curve
Single active site
104
Allosteric enzymes do not follow what?
Michaelis mentin bc they have multiple active sites
105
Increase temperature does what to reaction velocity?
Increase is it by increasing the number of molecules to have sufficient energy to pass over the energy barrier but too much can cause denaturation
106
PH and reaction velocity
Different PH’s are better for different enzymes but catalytic activity may require an amino group to be in the protonated form
107
What foremost the amino group of the enzyme be in for catalytic activity to occur?
Protonated
108
What does the Michael is menten equation describe?
It describes how velocity varies with substrate concentration
109
Km
Affinity of the enzyme for the substrate
110
A higher Km value means what?
Lower affinity of the enzyme for the substrate
111
1st order
When substrate is much less than Km (it’s the little box)
112
0 order
Everything after the little box and it’s one substrate is greater than Km
113
LineweaverBurke plots help us to see when _____ has been achieved
Vmax
114
Lineweaver x and y axis
X is 1/S
Y is 1/V0
115
In lineweaver plot….
The numbers get larger moving closer to the origin
116
X axis intercept
-1/Km
117
Y axis intercept
1/Vmax
118
_______ Are the most abundant and diverse molecules
Proteins
119
Proteins are______ made of_____ made of ________
Polymers, monomers, amino acids
120
______ common or standard amino acids coded by DNA
20
121
Which group determines the property of an amino acid?
R group
122
_______ has an H for the R group
Glycine
123
Standard amino acids have a 1° amino group except for
Proline (2° amino group has a ring shape)
124
_______ forms extended fibrous structure of collagen
Proline
125
Protein contains what
Polyproline type two helix more than alpha helix
126
