Cells And Proteins Flashcards
1
Q
What is centrifugation used for?
A
To separate materials in suspension according to their density.
2
Q
How does paper and thin layer chromatography work?
A
Amino acids are spectated according to their characteristics of solubility.
3
Q
How does affinity chromatography work?
A
Used for the separation of one specific protein from a mixture of proteins.
4
Q
How does protein electrophoresis work?
What factors affect the rate at which any particular protein migrates through a gel?
A
It uses a current flowing through a buffer to superset proteins.
Size and charge.
5
Q
What is the isoelectric point of a protein?
A
The pH at which it has an overall neutral charge.
6
Q
How can proteins be separated using their isoelectric point?
A
At their isoelectric point they precipitate out of solution.
7
Q
Why are antibody techniques used?
A
For the detection and identification of specific proteins.
8
Q
How do immunoassay techniques work?
What does the reporter enzyme do?
A
They use monoclonal antibodies linked with reported enzymes to cause a colour change in the presence of a specific antigen.
9
Q
What are monoclonal antibodies?
A
Antibodies that are identical and will bind to exactly the same feature of the antigen.
10
Q
How are monoclonal antibodies produced?
A
From hybridomas.
11
Q
How are hybridomas produced?
A
B lymphocytes fused with myeloma cells using polyethylene glycol (PEG).
12
Q
What is the proteome?
A
The entire set of proteins that can be expressed from a genome and this is much larger than the number of genes.
13
Q
Why is the proteome much larger than the genome?
A
Due to alternative RNA splicing and post-translational modification.
14
Q
What are the four classes of amino acids?
A
- acidic- eg. COOH
- basic- eg. NH2
- polar- eg. OH
- hydrophobic- eg. Hydrocarbon
15
Q
What determines the proteins structure?
A
The amino acid sequence.
16
Q
What is the bond that links amino acids together called?
A
A peptide bond.
17
Q
What stabilises secondary structure?
A
The hydrogen bonds along the backbone of the polypeptide strand.
18
Q
What are the three types of secondary structure?
A
Alpha helix
Beta sheets
Turns
19
Q
What is the tertiary structure?
A
The final folded shape of the polypeptide.
20
Q
What are regions of secondary structure stabilised by?
A
Interactions between R groups of amino acids.
21
Q
Four interactions between R groups?
A
Hydrophobic
Ionic bonds
Van der waals
Disulphide bridges
22
Q
What is quaternary structure?
A
Where two or more polypeptide chains interact to form the protein.
23
Q
What is a prosthetic group?
A
A non-protein group which is strongly bound to a polypeptide unit and is essential for the proteins function.
24
Q
Three important roles of R groups?
A
Determine the structure of a protein.
Can allow the binding of ligands.
R groups at the surface of a protein determine it’s location within a cell.
25
What is the position of R groups determined by?
The primary structure.
26
Where do hydrophilic R groups predominate?
At the surface of a cytoplasmic protein.
27
What molecules can pass through the hydrophobic region of the phospholipid bilayer?
Non polar molecules.
28
What does the hydrophobic centre of the phospholipid bilayer acts as a barrier to?
Charged ions and most polar molecules.
29
What do integral proteins do?
Transporter proteins which penetrate the phospholipid bilayer.
30
What do peripheral proteins do?
Form weak bonds to the surface of the membrane.
31
What is a ligand?
Any substance that can bind to a protein.
32
Why are ligands important?
Bonding of a ligand causes a conformational change to the protein, causing a functional change to the protein.
33
What are nucleosomes composed of?
DNA tightly coiled around histones.
34
What are allosteric enzymes?
Enzymes in which their activity is regulated by altering their conformation.
35
What is a modulator?
A substance that binds to an allosteric site on the enzyme away from the active site.
36
What do positive modulators do?
Increase the affinity of the active site for its substrate, increasing enzyme activity.
37
What do negative modulators do?
Decrease the affinity of the active site for its substrate and decrease enzyme activity.
38
What is cooperativity?
When the binding of a ligand to one subunit of the protein increases the affinity of another subunit.
39
What can activate or inactivate a protein?
The addition or removal of a phosphate depending on how the conformation of the protein is changed.
40
What do kinases do?
Catalyse phosphorylation.
41
What do phosphatases do?
Catalyse dephosphorylation.
42
What is the sequence of events of a muscle contraction?
Myosin binds to actin.
The myosin head detaches from the actin and swings forward.
The myosin head rebinds to the actin.
The myosin head swings back, dragging the actin filament along, generating a muscle contraction.
43
The passage of molecules through channel proteins is through...
Facilitated diffusion.
44
Example of channel protein
Aquaporin
45
What are the two types of gated channel proteins?
Ligand-gated channel & voltage-gated channels.
46
Why do the gated channel proteins open and close?
The conformation of the protein is changed.
47
That passage of molecules through transporter proteins is through...
Facilitated diffusion.
48
Transporter proteins undergo..
Conformational change.
49
Example of transporter protein
Sodium potassium pump
50
How does signal transduction occur?
When an extra cellular signal molecule binds to its receptor causing an intracellular response.
51
Sodium potassium pump stages
```
The protein has a high affinity for sodium ions and three sodium ions inside the cell.
Binding occurs.
Phosphorylation occurs.
Conformational change.
Low affinity for sodium.
Sodium released out of cell.
High affinity for potassium outside the cell.
Binding occurs.
Dephosphorylation occurs.
Conformational change.
Low affinity for potassium.
Potassium released into the cell.
```
52
Why is the movement of sodium and potassium ions so important?
Maintaining the osmotic balance in animal cells.
Generation of sodium ion gradient in kidney tubules.
Generation and maintenance of ion gradients for testing potential in neurons.
53
What is nerve transmission?
A wave of depolarisation due to sodium ion influx into the neuron.
54
What are the two principal forms of communication in multicellular organisms?
Hormonal and nervous
55
Different cell types produce...
Specific signals that can only be detected and responded to by cells with the specific receptor.
56
What are hormones?
Hydrophobic or hydrophillic extracellular signalling molecules that are secreted by one tissue into the blood.
57
Examples of hydrophobic hormones
Steroid hormones and thyroxine
58
Examples of hydrophillic hormones
ADH & insulin
59
Location of hydrophobic signalling molecule receptors
The cytoplasm or nucleus of the target cell.
60
What can hydrophobic signal directly influence?
The transcription of genes
61
How are integral proteins held within the membrane?
Hydrophobic interactions
62
What term describes the action of membrane receptors in which signal binding triggers an event in the cytoplasm that alter the behaviour of the cell.
Signal transduction.
63
What name is given to the electrical potential difference (voltage) across the plasma membrane of a cell?
Membrane potential.
64
What type of signalling molecule can stimulate nerve transmission?
Neurotransmitter
65
What type of membrane channel will open in response to a change in ion concentrations?
Voltage-gated
66
What name is given to proteins which are capable of sensing and responding to light?
Photoreceptor protwins
67
What do bacteriorhodopsin molecules do?
They generate potential differences by absorbing light to pump protons across the membrane.
68
Where are the target cells for ADH locates?
The collecting duct of the kidney.
69
Name the channel protein recruited to the membrane as a result of ADH binding to its receptor.
Aquaporin 2
70
Name the condition caused by lack of ADH production.
Diabetes insipidus
71
What are microtubules?
Hollow rods constructed of columns of a protein called tubulin.
72
A cell that passes the checkpoint towards the end of G1 will probably..
Undergo chromosomal duplication.
73
Describe the role of cyclin dependent kinases.
To cause the phosphorylation of target proteins that stimulate the cell cycle.
74
What type of disease may occur if there is a decrease in the rate of the cell cycle?
Degenerative
75
Metaphase anagram and steps
MSC
•Metaphase
•spindle fibres move chromosomes.
•chromosomes line up on the metaphase plate at the equator of the cell.
76
Telophase anagram and steps
TSNC
•Telophase
•spindle fibres pull chromosomes to opposite poles.
•nuclear membrane forms around each set of chromosomes.
•chromosomes start to uncoil.
77
Prophase anagram and steps
PCASN
•Prophase.
•Chromosomes condense
•appear as identical sister chromatids joined at the centromere.
•spindle fibres form and attach to kinetochores at the centromeres of the chromosomes.
•Nuclear membrane disintegrates. What
78
Anaphase anagram and steps
AS
•Anaphase
•spindle fibres pull sister chromatids apart.
79
Sequence of events when thyroxine not present
Thyroxine receptor protein binds to DNA.
Transcription of Na/K-ATPase gene is inhibited.
Less Na/K-ATPase is transcribed.
Metabolic rate reduces.
80
Sequence of events when thyroxine is present
Thyroxine binds to thyroxine receptor protein.
Receptor undergoes conformational change so it can no longer bind to DNA.
Gene for Na/K-ATPase is transcribed.
Metabolic rate increases.
81
Where are the receptors of hydrophillic signalling molecules?
The surface of the cell.
82
Describe the role of transmembrane receptors in responding to hydrophillic signals.
They change confirmation when the signalling molecule binds outside the cell. The signal molecule does not enter the cell but the signal is transduced across the membrane.
83
What do transduced hydrophillic signals often involve?
Cascades of G-proteins or phosphorylation by kinase enzymes.
84
Describe the role of insulin with reference to the GLUT4 transporter.
Binding of insulin to its receptor triggers the recruitment of GLUT4 glucose transporters.
85
What do GLUT4 transporters do?
Allow glucose to pass across the plasma membrane and enter the cell.
86
How does exercise reduce the impact of type 2 diabetes?
It triggers the recruitment of GLUT4 through other metabolic pathways: exercise improves the uptake of glucose to fat and muscle cells.
87
Describe the role of ADH with reference to the channel protein AQP2.
When ADH bind to receptors on the cells of the collecting ducts, a signal transduction process occurs which results in the recruitment of AQP2 to the membrane of cells.
88
What do aquaporins do?
Provide a highly efficient route for water to move across membranes.
89
What causes diabetes insipidus?
Caused by failure to produce ADH or insensitivity to its receptor.
Causes excessive watery urine.
90
Cytokinesis Anagram and steps
CC
| Cytoplasm divides to form two daughter cells.
91
What are the steps on interphase?
G1
S
G2
92
What happens during stages G1 &G2 of interphase?
Growth stages
| Proteins and organelles are synthesised.
93
What happens during the S phase?
DNA replication occurs.
94
What may an uncontrolled increase in the rate of the cell cycle cause?
Tumour formation.
95
Describe the G1 checkpoint
Sufficient cell growth must have occurred and other conditions must be satisfied before the cell can entered the S phase.
96
What happens to cell if it doesn't pass the G1 checkpoint?
It may switch to a non-dividing stage known as the G0 checkpoint.
97
How are CDKs formed?
As the cell size increases during the G1 stage, cyclin proteins accumulate and combine with kinases to form CDKs.
98
What is the role of CDKs?
They cause the phosphorylation of proteins that stimulate the cell cycle and if a sufficient threshold of phosphorylation is reached the cell moves into the next stage.
If an insufficient threshold of phosphorylation is reached the cell is held at a checkpoint.
99
What is retinoblastoma protein?
A transcription factor inhibitor.
100
Describe the role of the retinoblastoma protein in low levels of CDK activity.
It binds to the transcription factor E2F which inhibits the transcription of genes required to enter the S phase.
101
Describe the role of retinoblastoma when a sufficient threshold of CDK activity is reached.
The phosphorylation retinoblastoma protein can no longer bind to the transcription factors allowing the transcription of genes required for the cell to enter the S phase.
102
What are the roles of the p53 protein?
It is a transcription factor that can stimulate DNA repair, arrest the cell cycle of trigger cell death.
103
What does reverse transcriptase catalyse the production of?
DNA from RNA.
104
What is the sequence of events when a retinal molecule absorbs a photon of light?
Conformational change in rhodopsin activates hundreds of G-proteins.
G proteins activate hundreds of molecules of an enzyme.
Sodium channels close.
If there is sufficient buildup of sodium ions then the membrane will become hyper-polarised and a nerve impulse is generated.
105
What causes diabetes mellitus?
Caused by a deficient in the effect of insulin and results in the loss of control of blood glucose level.
106
What is the cytoskeleton?
A network of protein fibres that extends throughout the cytoplasm in all eukaryotic cells.
107
What is the function of the cytoskeleton?
It gives the cell mechanical support and shape.
108
What can happen if caspases are underactive/overactive?
Underactive- rumour formation
| Overactive-neurodegenerative disease
109
Explain the extrinsic pathway
Cell death signals originate out with the cell, for example from lymphocytes and bind to a surface receptor protein to activate a caspase cascade.
110
explain the intrinsic pathway
Cell death signals originate from within the cell, for example as a result of DNA damage the presence of the p53 protein can activate a caspase cascade.
In the absence of cell growth factors cells also may initiate apoptosis.
111
What triggers programmed cell death?
Cell death signals that activate inactive forms of DNAase and caspases that destroy the cell.
112
What are microtubules?
Hollow straight rods composed of the globular protein tubulin.
113
What is the function of microtubules?
They govern the location and movement of membrane bound organelles and other cell components.
114
Where are microtubules found?
All eukaryotic cells and radiate from the centrosome.
115
How are the spindle fibres active during cell division formed?
From microtubules.
116
Describe the mechanism by which absorption of a photon by chlorophyll results in the movement of H+ ions to the inside of the thylakoid membrane.
The light absorbed by the chlorophyll drives an electron flow that pumps hydrogen ions across the thylakoid membrane of the chloroplast.
117
Describe the mechanism by which the H+ ions return through the thylakoid membrane to the outside.
The hydrogen ions then diffuse back through the membrane through ATP synthase to generate ATP.
118
Name the substance aquaporin transports and describe how it's molecules move through the channel.
Water and move from a high concentration to a lower concentration.
119
What does phosphorylation provide energy for?
Active transport
120
Why must mouse B lymphocytes be hybridised with melanoma cells?
To produce an immortal cell line.
121
What are two uses of monoclonal antibodies in medical procedures?
Prevention diagnosis and treatment of disease
122
Name two degrading enzymes activating during apoptosis
DNAases and caspases
123
Stages of muscle contraction
ATP BINDS TO MYOSIN HEAD CAUSING IT TO DETACH FROM ACTIN FILAMENT.
MYOSIN HEAD SWINGS FORWARD AND ATTACHES TO ACTIN FILAMENT.
Phosphate ion released from myosin head.
Myosin head drags along actin filament.
124
What does a vital stain identify
Only stains dead cells
125
What happens to haemoglobin at a high temperature and low pH
Haemoglobin has lower affinity for oxygen so more is released into the tissues.
126
How does a hydrophobic signalling molecule cause an effect within the target cell?
It diffuses through the cell membrane and binds to a transcription factor.
127
Why is it important to return the target protein back to its inactive state?
So that sensitivity to the signal is restored.
