Week 1 Flashcards
(100 cards)
1
Q
What are the four major features of interactions between ligand and receptor?
A
1) Specificity
2) Affinity
3) Saturation
4) Competition
2
Q
What is cytoskeleton?
A
A filamentous network associated with processes that mantain and change cell shape.
3
Q
How are lipid soluble (nonpolar) ligand transported in the blood?
A
They are poorly solube in water so some travel in blood assiste by a carrier protein.
4
Q
What are the three different types of primary structure?
A
Alpha Helix
Beta plated sheet
Random coil conformation
5
Q
Describe intermediate filaments:
A
Composed of twisted strand of keratin, desmin or lamin. they contribute to cell shape and anchor the cell nucleus.
6
Q
What are tight junctions?
A
Forms when extracellular surfaces of two adjacent plasma membrane join together.
7
Q
How can the ligand-receptor complex induce its effect in the nucleus?
A
- delivering the messenger to another nuclear protein
- be the receptor itself.
8
Q
What are first messengers:
A
Chemical messengers that binds to plasma membrane proteins.
9
Q
What is signal transduction?
A
The sequence that leads to the cell final response the the chemical messenger
10
Q
Describe affinity:
A
The strength with which a chemical messenger binds to its receptor
11
Q
What are hemidesmosomes?
A
They connect cell to non-cellular material outside the cell (half of a desmosome).
12
Q
Describe transmembrane proteins:
A
Span the entire membrane and can function as channel, signal receptors or help anchoring the cell filaments.
13
Q
How are G-protein and the recpeto at rest?
A
They are bound but inactive.
14
Q
What does the replacemente of GDP to GTP initiate (step 2)?
A
It induce a conformational change in the alpha subunit. It cause it to detach from the rest of G proteins.
15
Q
What is the primary structure of a protein?
A
It is defined sequence and number of amino acids.
16
Q
What are the two types of chemical bonds
A
Ionic bond and covalent bond
17
Q
What are protein channels?
A
Integral proteins that span the lipid bilayer and can be formed by either a signle dounout shaped protein or several protein aggregats (each forming a subunit of the wall of the channel).
18
Q
What are the two classes of membrane proteins?
A
Integrals and peripherals.
19
Q
What are protein kinases:
A
An enzyme that phosporylate other proteins by transfering a phosphate group from an ATP to them.
20
Q
Describe the first step in receptors that functions as enzymes:
A
Receptor activation activate the enzymatic portion located on the cytoplasmic side and this result in the atophosphorylation of the receptor.
21
Q
What are GDP and GTP?
A
High energy phosphates, they store considerable potential chemical energy in the bonds between guanosine and each phosphates.
22
Q
Describe desmosomes:
A
Consist of a dense plaque along the cytoplasmic surface that serve as anchoring point for cadherins.
23
Q
Describe competition:
A
The ability of a molecule to compete with ligands to bind to its receptor.
24
Q
Describe ionic bond:
A
When one or more electrons are lost by a given atom the atom gains an electric charge and become an ion. When two ions attache they form an ionic bond.
25
What is the conformation of a protein?
Is the final shape of a functional protein
26
What is the secondary structure of a protein?
The basic folding or coiling of all or a region of a protein.
27
What is the first step of any intracellular chemical messenger?
Binding of a messenger (ligand) to a specific recepotr that has a binding site for it. This change the conformation of the receptor, activating it.
28
What are the three subunits of G-protein complex?
alpha, beta, gamma
29
Why does alpha subunit detach from other G proteins?
Because its tertiary structure is not compatible with the quaternary structure of the multi subunit complex.
30
Describe receptors that interact with Cytoplasmic Janus Kinases:
The tyrosine kinase activity resides in Janus Cytoplasmic Kinases associated with the receptor and activated in response to its activation.
31
What happen once the lipidsoluble ligand crossed the membrane?
It is carried to the nucleus by a binding protein.
32
What are cadherins?
Proteins that extend from the cell to extracellular space where they link up and bind with cadherins of another cell.
33
Describe the third step in receptors that function as enzymes:
The bound docking proteins activate other proteins that activate a signal pathway within the cell.
34
Describe the structure of a phospholipid:
The third hydroxil group of the glycerol backbone is linked to a negatively charge phosphate group which is bound to a polar or ionized nitrogen containing molecule.
35
What are the three different types of ion channels?
1) Ligand gated ion channels
2) Voltage gated ion channels
3) Mechanically gated ion channels
36
What is the first step of any intercellular chemical messneger (also called receptor activation)
The binding of the messenger to specific receptor proteins that cause the receptor conformation to change, activating it.
37
What are the factors that influence the final structure of a proteins embedded in the membrane:
The hydrophobic and relatively non polar interior of the membrane
The acqueous polar environment on each side of the bilayer
Other moelcuels found within the membrane, including other proteins.
38
What are the three fluxes that can be identified in diffuion?
The two way flux occuring in opposite direction
| The net flux
39
Describe hydrogen bond:
the molecular attraction between two polar molecules one of which has to contain
40
How is down regulation achieved?
Through internalization
41
What are essential amino acid?
Amino acids that are not produced by the body and therefore must be absorbed by diet.
42
Describe up regulation:
Cell's exposed for prolonged period to very low concentration of messenger may come to have more receptors for that messanger resulting in an increase sensibility.
43
What are nuclear receptors?
Intracellular receptor for nonpolar and lipid solube ligands.
44
What does cAMP do inside the cell?
It binds to cAMP dependend protein kinases and these kinases bring about cell response.
45
Describe saturation:
The degree to which receptors are occupied by ligands
46
What are the two forces by which a ligand can be bound to a receptor?
1) Electrical attraction between oppositely charged ionic or polarized groups
2) Weaker hydrophobic force between nonpolar regions of the molecule
47
Describe internalization:
The binding of a chemical messenger to its receptor cause the receptor to be taken up by receptor mediated endocytosis.
48
What are the 3 components of the cytoskeleton?
1) Actin filaments (microfilaments)
2) Intermediate filaments
3) Microtubules.
49
What are phosphatases:
Enzymes that dephosphorylate proteins and serve as stop signal once a cell response has occured.
50
What are integrins?
Transmembrane proteins in the plasma membrane tha tbind to specific proteins in the extracellular matrix or to plasma membrane proteins of other cells.
51
Tertiary structure:
Three dimensional shape of the protein formed once the secondary structure has been formed due to additional associations between amino acids side chains.
52
Describe peripheral proteins:
Not amphipatic and do not associate with the nonpoalr region of the lipids in the interior of the membrane. instead they are bound to polar region fo the integral membrane proteins.
53
Quaternary structure:
estabilished when a large protein is formed by multiple subunits.
54
What is an agonist receptor?
A molecule that compete with a ligand and do activate the receptor triggering cell's response.
55
Describe the second step in receptors that function as enzymes:
The phosphotyrosine serve as docking site for other cytoplasmic proteins.
56
What are the two ways of changing cAMP concentration?
- Altering the rate of its messenger-mediated synthesis
| - Altering the rate of its phosphodiesterase mediated breakdown.
57
What are the two important points about the gene expression exerted by the ligand-receptor complex?
1) more than one gene may be subject to control by a single receptor type.
2) transcription of a gene may be decreased instead of increased.
58
What happen once the alpha subunit activates its effect protein?
A GTPase activity inherent in the subunit cleaves GTP to GDP. This make the alpha subunit inactive allowing it to recombine with beta and gamma.
59
What are proteins:
Polymeric strings of amino acids bound together by peptide bonds.
60
What is diffusion?
the movement of molecules from one location to another due to random thermal motion.
61
What is an antagonist competitor?
A molecule that blocks the action of a chemical messenger binding to its receptor without activating it
62
Describe actin filaments:
Composed of monomers of G-actin that assemble into a a two twisting chain known as F-actin
63
What are the two types of receptors?
Plasma membrane and intracellular receptors
64
What are gap junctions?
Consists of a protein channel linking the cytosols of two adjancent cells.
65
What is the net flux?
Is the difference between the two fluxes occuring in opposite direction.
66
Describe specificity:
The ability of a receptor to bind to only one type of structural related chemical messengers.
67
What are the three aspects that determine specificity of a protein channel?
- Pore size
- Charge
- Binding site.
68
What happen when the ligand bind to the receptor (step 1)?
The receptor undergoes conformational change leading to a conformational change in the G protein as well. This allow the exchange of GDP for GTP.
69
What are the three types of membrane junction?
Desmosomes
Tight Junctions
Gap Junctions
70
What are the two hydrogen bonds type that influence the secondary structure of a protein?
The hydrogen bonds formed between polar R groups of the side chain
The hydrogen bonds formed between the ammino and carboxyl group of amino acids 5 residues apart from each other on the primary structure.
71
Describe covalent bond:
Electrons are shared between the outer shell of two atoms.
72
Describe integral proteins:
Are embedded or closely associated with the membrane lipids and are amphpatic.
73
What is the only exception in receptors that function as enzymes:
The receptor function as a receptor and as a guanylil cclase to catalyze the formation of cyclic GMP.
74
Describe receptors that function as enzymes:
They are all protein kinases (except one) and the majority phosphorylate tyrosine residues so they are known as receptor tyrosine kinases.
75
What does intercellular means?
Something that happens between cells
76
How is the final respose to a messenger called?
Transduction.
77
What is the role of alpha subunit?
It can bind to GDP and GTP.
78
Describe plasma membrane receptors:
They are transmembrane proteins and the arriving chemical messenger bind to the binding sites located on the extracellular region whereas the intracellular region initiate the transduction.
79
Molecules can be:
Polar
Nonpolar
Amphipatic
80
What is the conformation of a protein?
The final shape of a functional protein.
81
Describe amphipatic molecules:
They have a polar charged or ionic region and a nonpolar region
82
What is channel gating?
Process of closing and opening ion channels
83
Describe down regulation:
When a high extracellular concentration of a messenger is maintained for some time, the toal number of receptor fot that messenger decrese
84
What does cGMP does?
Function as a second messenger to activate a protein kinase known as cGMP-dependent protein kinase.
85
What are the two states in which ion channels can exist=
Open or closed.
86
What is the role of beta and gamma subunit?
They help anchor the alpha subunit in the membrane.
87
What are the five major factors that determine the tertiary structure of a protein?
1) hydrogen bonds between side groups of amino acids or with surrounding water molecules
2) ionic interactions between ionized regions of the chain
3) interactions between nonpolar regions
4) covalent disulphide bonds linking the sulfur-containing side chain of two cystein amino acids
5) Van der Waals forces between electrons on the outer shells of two atoms in close proximity on the chain.
88
Cellular response to receptor activation may be:
1) Permeability, transport properties or electrical state of plasma membrane
2) Metabolism
3) Secretory activity
4) Rate of proliferation and differentiation
5) Contractile or other activities
89
What are the 4 types of receptor:
1) Receptors that are ligand-gated ion channels.
2) Receptors that functions as enzymes.
3) Receptors that interact with Cytoplasmi Janus Kinases
4) G-protein coupled receptors.
90
Describe cholesterol and its function in the membrane:
It is made of many C-C o hydrocarbon bonds and therefore it is nonpolar. For this reason it is immersed in the phospholipid bilayer. It determines the fluidity of the membrane being bulky (due to its several rings and hydroxyl, methyl and isoheptane substitutions groups) make it difficult to hydrocarbon tails to pack too closely together.
91
What happen once the messenger reaches the nucleus?
The ligand-receptor complex acts directly on gene exression to induce cellular response.
92
Explain the two reasons why cell membranes must be fluid:
1) So that the membrane can be deformed as the body move
| 2) So that substances can be released or taken up into the cell via exocytosis and endocytosis.
93
What are second messengers:
Substances tht enter or are generated in the cytoplasm as a result of receptor activation of a first messenger.
94
What are the two ways of regulation of receptors?
Down regulation
| Up regulation
95
What is the usual result of receptors that interact with Cytoplasmi Janus Kinases?
The result of this pathway is the synthesis of new proteins.
96
Describe intracellular receptors:
They exists either in the cytosolo or in the cell nucleus and have a binding and a regulatory site. They especially have a segment that binds to DNA because they transduce signals through interactions with genes.
97
What does intracellular means?
Something that happen within the cell
98
What does alpha subunit does once detached? (step 3)
alpha subunit link with another plasma membrane protein called G-protein-coupled receptor.
99
What are microtubules?
Hollow tubes composed of tubulin and they are the most rigid cytoskeletal filament.
100
Describe receptors that are ligand-gated ion channels:
The protein that acts as a receptor is also an ion channel tha open or close in response to receptor activation.
