Mammalian Cell Biology Flashcards
1
Q
What contains specific proteins, lipids and sugars?
A
Plasm membranes
2
Q
What are does plasma membranes surround?
A
A cell
3
Q
What can you word can be used to describe phospholipids?
A
Amphipathic
4
Q
What is Amphipathic?
A
Having hydrophobic and hydrophilic parts
5
Q
What makes the bio-membrane?
A
Phospholipids
6
Q
What occurs to phospholipids in the presence of water?
A
Lipid bilayer
7
Q
Are plasma membranes fluid or solid?
A
Fluid
8
Q
What do steroids serve as?
A
Hormones
9
Q
What is the source for sex hormones?
A
Cholesterol
10
Q
What do steroids affect?
A
Membrane fluidity
11
Q
What model represents the phospholipid bilayers?
A
Fluid Mosaic Model
12
Q
What is the Fluid Mosaic Model?
A
-Applies to all membrane
-Membranes are fluid and flexible
-Proteins embedded in liquid environment
-
13
Q
How thick is a plasma membrane?
A
4nm
14
Q
Is the plasma membrane organised by itself or by other factors?
A
Itself
15
Q
How does plasma membranes self organise?
A
Due to interaction between the hydrophilic and hydrophobic parts the membrane with water and lipids in the cytoplasm
16
Q
What structural difference allows the identification of organelles?
A
Membranes differ in their lipid composition
17
Q
Do membranes contain particles?
A
Yes
18
Q
Using a microscope, what difference can you visualise when observing an exoplasmic extracellular membrane and the cytoplasmic face?
A
Less proteins embedded in the extracellular membrane
19
Q
What do fibres of cytoskeleton interact with on the plasma membrane
A
Proteins
20
Q
What are lipid rafts?
A
Membrane regions that assemble specialised lipids and proteins to preform a certain task
21
Q
What is an example of a lipid raft?
A
Sites of uptake in plasma membranes are rich in cholesterol and sphingolipids an receptors
22
Q
Why would use use Fluorescent Recovery After Photobleaching (FRAP)?
A
To investigate differences in membrane fluidity and protein mobility
23
Q
What are the various functions of a protein in plasma membrane?
A
- Anchorage with cytoplasm
- Communication with cytoplasm
- Anchorage at extracellular matrix
- Transport over membranes
- Cell-cell communication
24
Q
What are different types or proteins embedded in membranes?
A
- Transporters
- Enzymes
- Receptors
- Cell-cell recognition
- Intracellular joining
- Attachment to the extracellular matrix an intracellular cytoskeleton
25
Are biomembranes permeable, semi-permeable or impermeable?
Semi-permeable
26
What can passively pass through a bio-membrane?
Uncharges, small, hydrophobic molecule
27
What do channels mediate?
Communication and exchange of small molecules and ions
28
What are the difference between pumps and channels?
Pumps require/consume ATP
29
What does gating of ion channels control?
Permeability of ion channels
30
When are gates normal open or closed?
In response to stimuli
31
What are the different types of channels?
- Voltage gated channel
- Mechanically gated channel
- Temperature gated channel
- Ligand-gated channel
32
What do channels rely on whether closed or opened?
Depend on concentration gradient
33
Does facilitated glucose transport require ATP?
No
34
How much of E.coli plasma membrane covered by transporters?
2%
35
How do channels form a membrane potential over their plasma membrane?
Having an asymmetry of ionic charges over there membranes
- More positive charge outside
- More negative charge inside
36
What are cell called if they do not change their membrane potential?
Non-excitable cells
37
What is an example of non-excitable cells?
Epithelial cells
38
What is an example of excitable cells?
Muscle cells, neurones
39
What are excitable cells?
Membrane potential can dramatically change
40
What is required for a membrane potential?
- Difference in ion permeability of plasma membrane
| - Activity of ATO-dependent ion pumps
41
How do you establish a resting membrane potential?
- Na+ enter pump and bind
- ATP comes along changing the conformation of the pump
- Pump is a phosphorylated ADP + Pi produced, ATP leaves
- Na+ diffuse out of cell
- Inside more negative than outside
- K+ binds to K+/Na+ pump, Pi leaves
- K+ ion enters cell
- K+ ion higher concentration gradient inside so K+ leaves via K+ leakage pump
- Resting membrane potential reached
42
What is established in epithelium cells?
Tight lateral and basal contact
43
In epithelium cells what are the function of tight junctions?
Cells hold so tightly together there is no diffusion between the cells, have a high field of interacting proteins
44
Where can you find tight junctions?
In the blood brain barrier
45
What type of barrier do tight junctions act like?
Diffusion barrier
46
What are structures you can find in the epithelium cells which help establish high lateral and basal contact?
- Tight junctions
- Adherens junctions
- Gap junctions
- Desmosomes
- Hemidesmosomes
- Extracellular matrix
47
What is the function of adherents junctions?
Involved in controlling actin organisation
48
What do adherents junctions consist of?
Cadherins and catenin
49
Why do adherents contain cadherins?
To from cadherins bright between cells
50
Why do adherents contain catenin?
Catenins link to the actin cytoskeleton
51
What is the role of gap junctions in epithelium cells?
Supports exchange between the cytoplasm of adjacent cells
52
What makes up gap junctions?
A field of connecting channels, each made up of connexins
53
What do the channels of hap junctions allow the passage of?
Ions and small molecules
54
What is the function of desmosomes in epithelium cells?
Resist shear force in epithelia and in muscle
55
What do desmosomes consist of?
Specialised Catherine proteins that interact with each other and with intermediate filaments
56
Why are filaments important fibres?
Resist shared force
57
What is the function of hemidesmosome in epithelium cells?
Anchor the epithelia cell to basal lamina and involved in signalling
58
What do hemidesmosome consists of?
Many proteins (including ingrains) that interact with extracellular matrix
59
Where can you find hemidesmosomes structures?
In skin epithelial cells
60
What is the function of the extracellular matrix in epithelium cells?
-Holds tissues together, provides strength, directing cell migration
61
What is the extracellular matrix consistent of?
Fibres of secreted protein (collagen, matrix proteins and glycoproteins)
62
What can cells sense and react too?
Its environment
63
What are the two major intracellular signalling mechanisms ?
- Phosphorylation of protein
| - Signalling by GTP-binding protein
64
What proteins are involved in intracellular signalling pathway?
- Receptor protein
- Intracellular signalling proteins
- Effector proteins
65
What do metabolic enzymes alter?
Metabolism
66
What do gene regulatory proteins alter?
Gene expression
67
What do cytoskeletal protein alter?
Cell shape or movement
68
What are G-proteins?
Molecular switches
69
What are G-proteins activated by?
Guanine nucleotide exchange factor (GEF)
70
What are G-proteins inactivated by?
GTPase-activating protein (GAP)
71
Describe small monomeric G-proteins:
Receive signals from many receptors
72
What is an example of small monomeric G-proteins?
Rab-GTPase
73
Describe large trimeric G-proteins:
Interact with G-protein coupled receptors
74
What is an example of large trimeric G-proteins?
G-proteins that activate adenylyl cyclase
75
What a kinases often forming?
A signalling cascade
76
What can control the activity of effector protein?
Phosphorylated kinase or phosphatases
77
Does protein kinases and phosphatases have a specific or broad roles in control protein activity and cellular processes?
Broad role in control protein activity and cellular processes
78
What is kinase?
An enzyme that transfers phosphate groups from high-energy donor molecules to specific substrates (Phosphorylation)
79
What is phosphatase?
An enzyme that removes a phosphate group from a protein (dephosphorylation)
80
Is phosphorylation the adding or taking phosphates?
Adding phosphates
81
Is dephosphorylation the adding or taking phosphates?
Taking phosphates
82
What percentage of all human proteins carry a phosphate group?
30%
83
How many kinases does the human genome contain?
520
84
How many protein phosphatase does the human genome contain?
150
85
What can kinases act as?
Microchips
86
What can kinase act as microchips?
Can integrate information
87
What does cdk kinase control?
Control of cell progression
88
What does src-type kinase control?
Control of regulate various biological functions
89
What motion do particles and molecules undergo?
Brownian motion
90
What is Brownian motion?
Diffusional motion, random motion of particles
91
What does diffusion depend on?
The size of the molecule/organelle
92
Does the molecule have to be smaller or bigger in order to diffuse quicker?
Smaller
93
What is diffusion restricted by?
Crowded cytoplasms
94
How many subunits make up a ribosome?
2
95
What subunits make up prokaryotes 70S ribosome?
50S
| 30S
96
What subunits make up eukaryotes 80S ribosome?
60S
| 40S
97
What does the S stand for?
The Svedberg unit
98
What does the Scedberg unit describe?
The sedimentation behaviour of particles
99
What did Scedberg develop?
The technique of analytical ultracentrifugation
100
What factors determine the S value?
A particle is mass, density and shape
101
What does 50S of prokaryotic ribosome contain?
5S rRNA
23S rRNA
24 Proteins
102
What does 30S of prokaryotic ribosome contain?
16S rRNA
| 21 protein
103
What does 60S of eukaryotic ribosome contain?
5S rRNA
28S rRNA
49 Proteins
104
What does 40S of eukaryotic ribosome contain?
18S rRNA
| 33 Proteins
105
What are the subunits of ribosomes made up of?
Proteins and rRNA
106
Where can you find ribosomes?
In the cytoplasm
107
What is the role of ribosomes?
Translate information from mRNA to proteins
108
Describe protein translation:
- Matching tRNA to mRNA
- Release of elongation factor TU
- Formation of peptide bound
- Elongation factor G triggers a forward movement of ribosomes
109
What is a polysome?
Numerous ribosome operate along a single mRNA molecule
110
What is the largest organelle?
Nucleus
111
What is the average size of the nucleus in comparison to cell volume?
10% of cell volume
112
What makes up the nucleus?
- Euchromatin
- Heterochromatin
- Lamina
- Nuclear pore
113
How many membranes does the nucleus have?
two
114
What is the inner membrane of a nucleus?
Phospholipid bilayer
115
What is the outer membrane of a nucleus?
Lumen around nucleus (aka nuclear envelope)
116
What acts as gates controlling transport in and out of the nucleus?
Nuclear pores
117
What makes up the nuclear lamina?
Net work of fibres
118
What is the role of nuclear lamina?
Protects nucleus from damage, organises the distribution of nuclear pores and arranges interphase chromosomes
119
What happens if no lamina in the nuclear membrane?
Nuclear pores cluster
120
What happens to the nuclear envelope and nuclear lamina during mitosis?
Disassembles
121
Are nuclear pores highly organised or disorganised multi-protein complexes?
Highly organised
122
What do nuclear pore complexed composed of?
- 8-fold symmetry
| - Numerous proteins build pore
123
What are nucleoporines?
Proteins that make up a nuclear pore
124
How many different nucleoporins make up a pore?
30 nucleoporins
125
What structure does the inner pore of a nuclear pore have?
Cage-like structure
126
What structure does the outside pore of a nuclear pore have?
Extensions toward cytoplasm
127
What molecules can simple diffuse?
Small and uncharged
128
What molecules require active transport?
Large and charged
129
What does nuclear transport depend on?
- Smal GTPase
| - Soluble import/export receptors (aka helper proteins)
130
What can target specific organelles by localisation signals?
Fluorescent proteins
131
What does the nuclease realise during mitosis?
Its content = has to re-import nuclear proteins
132
What does nucleolus form?
Ribosome
133
What is the structure of a nucleolus?
- Granular components
- Fibrillar centres
- Heterochromatin
- Euchromatin
134
What is the function of granular component?
Ribosome assembly site
135
What is the function of fibrillar centres?
rRNA transcription
136
What is heterochromatin?
Remain packed after mitosis, transcriptional inactive, 10% of DNA
137
What is euchromatin?
Transcriptional active
138
Is chromosome DNA much bigger than the nucleus?
Yes 1000x
139
What must the chromosome be to fit into the nucleus?
highly folded
140
What is chromatin?
Interaction of structural proteins to fold chromosomes
141
Why is DNA tightly packed during mitosis?
- Takes least amount of space
- Best protected by protein
- Suitable for inheritance during mitosis
142
What is the size of DNA?
2nm diamete
143
Is DNA negatively or positively charged?
Negatively charged
144
Are histones negatively or positively charged?
Positively charged proteins
145
How many types of histones are there?
4 types
146
What are the 4 types of histones?
H2A, H2B, H3, H4
147
Histones are considered as small proteins. How many amino acids is that approximately?
100 amino acids
148
Where is DNA normally organised in?
Nucleosomes
149
Do nucleosomes tighten or loosen during transcription?
Loosen
150
What is the average size of nucleosomes?
30 nm
151
How is a 30nm fibre formed chromatin?
Interaction between DNA and histones = higher degrees of package
152
What is 200nm fibre of chromatin?
DNA is further packed around a scaffold that contains specialised proteins
153
Is there transcription during metaphase?
No
154
Why is there no transcription during metaphase?
A chromosome is tightly packed
155
What is the main process in nucleus?
Transcription
156
What is transcription?
Process of transcribing DNA nucleotide sequence information into RNA sequence information
157
What are the types of RNA polymerase in eukaryotes ?
- RNA polymerase I : ribosomal RNA
- RNA polymerase II: messenger RNA
- RNA polymerase III: transfer RNA
158
What is the RNA polymerase revenant to plants?
RNA polymerase IV: siRNAs, required for heterochromatin formation
159
How many types of RNA polymerase are there in prokaryotic cells?
1
160
Is linker DNA transcribed?
No
161
Describe the basic principle or transcription:
1. Numerous transcription factors bind to the TATA box in the promoter
2. RNA polymerase binds to the template strand and synthesis an exact copy of the coding stand
3. RNA is release, further processed and released from the nucleus (bound to RNA-binding proteins)
162
Where does transcription occur in prokaryotes?
Cytoplasm
163
Where does transcription occur in eukaryotes?
Nucleus
164
What is the difference of mRNA in prokaryotes and eukaryotes?
Prokaryotes: use mRNA directly
Eukaryotes: Pre-mRNA modified to mRNA where mRNA and RNA binding protein exposed via nuclear pores
165
Does translation occur immediately in cytoplasm of prokaryotes?
Yes
166
Which sentence is relevant to prokaryotes:
A. Many genes on one mRNA
B. One mRNA for one gene
A
167
Which sentence is relevant to eukaryotes:
A. Many genes on one mRNA
B. One mRNA for one gene
B
168
What does the endomebrane system contain?
- Nucleus
- Endoplasmic reticulum
- Golgi apparatus
- Lysosome/Vacuole
- Endosomal compartments
- Transport vesicles
169
What are compartments of endomembrane system connected by?
Transport vesicles
170
What is a cellular compartment?
Membrane-surronded space in the cell
171
What do you call a cellular compartment which has a specialised function?
Organelle
172
Are transport vesicles organelles?
No
173
Does the endoplasmic reticulum communicate directly or indirectly to the Golgi-apparatus?
Directly
174
What does the Golgi apparatus communicate with?
Late/early endosomal compartments
175
What doe endosomal compartment communicate with?
Lysosomes
176
How are communication between all compartments mediated?
Via transport vesicles
177
What is membrane trafficking?
Motors move transport vesicles and organelles within the cell
178
What are molecular motors?
Enzymes that use ATP to move along the cytoskeleton
179
What is secretion?
Transport from the interior to plasma membrane for release in to the environment
180
What do vesicles mediate?
Exchange of material between the cell and the environment
181
What is exocytosis?
Vesicles fusing with cell membrane to release material
182
What is endocytosis?
Vesicles forming at the membrane to transport material into the cell
183
What are the three types of trading pathways?
1. Secretory pathway (biosythesis)
2. Endocytic pathway
3. Retrieval-recycling pathway
184
What is secretory pathway?
Material from inside cell transported to outside cell
185
What is endocytic pathway?
Material from outside side transported to inside cell
186
How many secretory vesicles does a single human beta cell have?
10,000
187
What is the endoplasmic reticulum in contact with?
The nuclear envelope
188
What is endoplasmic reticulum?
Membranous synthesis and transport organelle that is an extension of the nuclear envelope
189
What makes up the endoplasmic reticulum?
Membrane sacs and bracnched tubules
190
What makes up 50% of all membranes of the cell?
Membrane sacs and branched tubules
191
Are the tubules of the endoplasmic reticulum motile or fixed?
Motile
192
What are the two types of endoplasmic reticulum?
- Smooth endoplasmic reticulum
| - Rough endoplasmic reticulum
193
What is the purpose of smooth endoplasmic reticulum?
- Calcium storage for cell signalling
- Lipid synthesis
- Detoxification of drugs/poisons
- Metabolism of carbohydrates
194
What is the purpose of rough endoplasmic reticulum?
Processing of secretory proteins
195
What can you visualise of rough endoplasmic reticulum using a microscope?
more organised and has dots representing ribosome on the surface of them
196
What can you visualise of smooth endoplasmic reticulum using a microscope?
Highly disorganised
197
Describe cotranslation translocation into the endoplasmic reticulum:
1. Ribosome assembles and binds mRNA
2. If polypeptide contains a signal sequence,
the ribosome is targeted to the ER membrane; If not it stays in the cytosol
3. The signal peptide is cleaved off and the protein is translated into the ER lumen where it is folded and further processed
4. Cytosolic proteins can contain signal sequences that target them to other organelles
(nucleus, mitochondria, peroxisomes, chloroplasts)
198
When are integral membrane proteins inserted at the endoplasmic reticulum?
During translation
199
What are many membrane receptors?
Type I, II and IV
200
What are the different types of transmembrane receptors?
```
Type I
Type II
Type III
Type IV
GPI-linked
```
201
What is transmembrane domain?
Consists of number of hydrophobic amino acids will integrate and stain in membrane
202
What are Golgi apparatus?
Disc-shaped stack of membranes
203
Describe the organisation of Golgi apparatus (cis face to trans face):
- Cis face
- Cis Golgi network
- Golgi stack (Cis cisterna -> medial cisterna -> trans cisterna)
- Trans Golgi network
- Trans face
204
What are glycoproteins?
Membrane contain proteins that are linked to sugar residues
205
What is the function of oligosaccharide?
- Provide protection against pathogens
- Serves in cell-cell recognition and signalling
- Marks progression of the protein
- Helps folding and interaction with other proteins
206
Where are oligosaccharides processed?
In the Golgi
207
Where are proteoglycans assembles?
In the Golgi
208
What do most proteins that arrive at Cis Golgi from endoplasmic reticulum contain?
N-linked oligosaccharide
209
Describe the process of oligosaccharide chains in the Golgi:
- Cis Golgi network: phosphorylation of oligosaccharide on lysosomal proteins
- Cis cisterna: Removal of Man
- Medial cisterna: removal of Man, addiction of GlcNAc
- Trans cisterna: Addition of Gal, addition of NANA
- Trans Golgi network: Sulfation of tyrosine and carbohydrates
210
What do oligosaccharide undergo in the Golgi?
Several glycosylation steps
211
What is glycosylation?
Adding and modifying sugar residues on protein
212
In what two ways can oligosaccharide be linked proteins?
- N-linked
| - O-linked
213
Where are N-linked oligosaccharide largely occur?
In endoplasmic reticulum
214
Where are O-linked oligosaccharide largely occur?
In Golgi apparatus
215
How many of all eukaryotic proteins glycosylated?
50%
216
What are the serval different types of endosomes?
- Late endosomes
- Early endosomes
- Recycling endosomes
217
What are the three types of endocytosis?
Phagocytosis
Pinocytosis
Receptor-mediate endocytosis
218
What is phagocytosis?
Large particles taken up in large vesicles
219
What are pinocytosis?
Small/liquid particles which are dissolved in liquid
220
What are receptor-mediate endocytosis?
Receptors are exposed and bind to specific molecules goths a coated pit (a vesicle formed with protein) and surrounded by coated proteins on the outside
221
Describe the membrane trafficking along the endocytic pathway:
1.Formation of a vesicle
at the plasma membrane (pH of cytosol 7)
2.Fusion of vesicle with early endosome (pH of cytosol 6.5)
3.Decision: degradation or recycling of receptors in vesicles to plasma membrane or recycling via endosome
4.Maturation of early endosome to late endosome (Internal pH 5.5 to 4.5)
5. Specific enzyme can become active due to low pH where enzymes digest molecules to small pieces
6.Recycling from late endosome to Golgi
7.Maturation of late endosome into lysosome
8.Majorityly of material ends in lysine (internal pH 4.5)
222
What is the last compartment of the endocytotic pathway?
Lysosomes
223
What is the equivalent of lysosome (which is present in animal cells) in a plant cell?
Vacule
224
What does phagocytosis fo in macrophages?
Cleans the body from invading pathogens and damaged cells
225
What can occur in phagocytosis which is a major problem?
Some pathogens stop the process and escape the phagosome to infect the host cell
226
What does incomplete phagocytosis underlies?
The endosymbiont hypothesis
227
What is endocytosis?
Uptake of material into the cell
228
What is autophagy?
Membrane vesicles fuse and form autophagosome which engulfs organelles which fuse with lysosome
229
Do organelles have a limited life time?
Yes
230
What do autophagy do to those organelles that have a limited life time?
Recycles organels
231
What do lysosomes serve as?
Disposal containers
232
Why do lysosomes serve as disposal containers?
- Low pH acid hydrolase have optimum activity
| - Degrade to fundamental structures to be transported out of lysosome and reused
233
What do transport vesicles do?
Deliver their content to compartments and to/from from the plasma membrane
234
What is the size of transport vesicles?
About 25-200 nm
235
Are transport vesicles moving around by diffusion?
No actively moving in the cell
236
What do transport vesicles carry various of?
Cargo
237
How many type of integral proteins are there in synaptic vesicles?
50
238
How many phospholipids are there in synaptic vesicles?
7000
239
How many cholesterol molecules are there in synaptic vesicles?
5700
240
What provides membrane specificity?
SNARE receptors
241
How do SNARE receptors provide membrane specificity?
- vSNARE forms a complex with tSNARE
| - Fusion of a vesicle with a target membrane
242
How does fusion of a vesicle with a target membrane occur?
1. Tethering
2. Docking
3. Fusion
243
What occurs in step 1. tethering of how does fusion of a vesicle with a target membrane occur?
Rab-binding tethering factor at target membrane binds the RAB-GTP vesicles (loosely links)
244
What occurs in step 2. docking of how does fusion of a vesicle with a target membrane occur?
vSNARE interacts with tSNARE (brings vesicle more closely to membrane)/interaction overcome replying forces
245
What occurs in step 3. fusion of how does fusion of a vesicle with a target membrane occur?
pH drops, ligand is release (some parts are recycled) a v-SNARE-tSNARE complex is formed
246
What are many vesicles coated in?
- Clathrin
- COPI
- COPII
247
What do vesicles coats do?
- Coat concentration specific proteins in patches
| - Coat holds the forming vesicles
248
Are coats generalised or specific for particular places in the endocytic and the exocytic pathway?
Specific
249
What coats are found on Golgi apparatus?
COPI
250
What coats are found on early endosomes, endocytic pathway?
Clathrin
251
When are coats formed?
Formed around emerging vesicles
252
What are involved in the molecular organisation of a Cathrin coat?
- Adaptin = which binds the receptor
- Clathrin coat = binds to adaption, shape vesicles
- Clathrin = subunits consists of triskelion structure of three heavy chain and three light chain of Cathrin proteins
253
Describe formation of a clathrin-coated vesicles:
- Receptors bind to cargo, more receptors binding more recognising
- More triskelion structure recruited (self assemble)
- Specificity is provided by adaptor-receptor interaction
- Self assemble bends the membrane forms the vesicles
- Coat formation curves the membrane and shapes the vesicles
- Coat is readily lost and vesicles interacts with the cytoskeleton for intracellular transport
254
Can coatings of vesicles be reused?
Yes
255
What delivers deeper into the cell coated or naked transport vesicles?
Naked transport vesicles
256
What are extracellular vesicles?
Transport vesicles which are released from cells
257
Where do you find extracellular vesicles?
In body fluids
258
What are examples of body fluids?
Fluids around brain and spinal chord, urine, blood
259
What do extracellular vesicles contain?
RNAs, porteins
260
What provides the RNAs and protein in extracellular vesicles?
Donor cells
261
Where do extracellular vesicles deliver their content to?
Recipient cells
262
What is an example of an extracellular vesicles in cell-cell communication?
Microvesicles
| Exosomes
263
What is another name for microvesicles?
Ectosomes
264
Describe cell-cell communication via microvesicles:
- Formation at donors plasma membrane
- Transfer proteins, mRNAs and miRNAs
- Uptake via fusion with plasma membrane
265
Describe cell-cell communication via exosomes:
- Formed at early endosomes, released from late endosomes
- Transfer protein, mRNAs and miRNAs
- Uptake via endocytosis or fusion with recipient's plasma membrane
266
What is the role of exosomes and microvesicles?
- In immunology
- In blood
- In CNS
- In bone
267
What can spread cancer?
Extracellular vesicles
268
What does cytoskeleton provide?
Tracks that link the region of the cell
269
What are the three different filaments that make up the cell?
- F-actin
- Microtubules
- Intermediate filaments
270
What is the size of F-actin?
7-9nm
271
Is F-actin short or long range communication?
Short range communication
272
Is microtubules short or long range communication?
Long range communication
273
What does intermediate filaments add to the cell?
Mechanical strength
274
What is the cytoskeleton?
Consists of filaments bio-polymers and of associated proteins that are modulating the activity, dynamics or organisation of the cytoskeleton
275
What is the role of the cytoskeleton?
- Connects all parts of the cell
- Support motility
- Helps spatial organisation
276
What does the cytoskeleton provide for intracellular trafficking?
Tracks
277
What is essential for cell function?
Exchange of material and information
278
Does the cytoskeleton provide stability for the cell?
Yes
279
What is structure of F-actin?
- Subunits G-actin (binds ATP in the centre)
| - Two pear strings twisted around each other (Two protofilaments)
280
Where is actin found?
In animal cells
281
What modifies actin organisation?
Actin-binding proteins
282
What are different types of actin-binding modifications?
- Sequestering/Recycling
- Capping
- Branching/Nucleating
- Depolymerising
- Nucleating/Polymerising
- Cross-linking
- Moving
- Severing
- Bunding
- Stabilising
283
How different types of actin-binding proteins are there?
+160
284
What is an example of ordered bunding?
Microvilli
285
What do actin form?
Cellular protrusions
286
Where does polymerisation occur at microtubules?
N plus end
287
What is the structure of microtubules?
- Dimers coasting of a-tubulin and B-tubulin
- Bind to a GTP
- B-tubulin = GTP hydrolysed to GDP
288
How many protofilaments to make up a microtubule?
13 protofilaments
289
Where are microtubules made and extended to?
Made at centrosome and sent towards periphery cell
290
What modifies microtubule organisation and function?
Microtubule-binding proteins
291
What are different types of microtubule-binding modifications?
- Nucleating
- Capping
- Cross-linking
- Depolymerising
- Attaching
- Moving
- Severing
- Stabilising
- Bunding
- Polymerising
- Sequestering
292
What does helioza from?
Microtubule-supported protrusions
293
What are helioza?
- Projection contain highly organised microtubules
| - Serves in capturing food, sensation, movement and attachement
294
How does polymerisation of microtubules work?
Plus-end binding proteins control dynamics of microtubules and participate in intracellular motility?
295
What happens at plus-end of microtubules?
- Attachment of microtubules to cell periphery
- Control of microtubule dynamic behaviour
- Control of intracellular trafficking by regulating dynein
296
What do microtubules nucleating from?
Microtubule organising centre near the nucleus
297
What do animal centromeres contain?
Centrioles
298
What do centrioles mainly consist of?
Microtubule
299
What do centrioles become of flagella and cilia?
Basal body
300
What does the centrioles organise?
Pericentriolar material together and ensures it inheritance
301
What does not have centrioles?
Fungi and plants
302
What do fungi and plants have instead of centrioles?
Gamma-tubulin
303
Do centrioles replicate during cell cycle?
Yes
304
What does peri-centriolar material contain?
Gamma-tubulin
305
What do tubules exists as?
Dimers and as polymers
306
What subunits build tubules?
a-tubulin
| B-tubulin
307
What does adding of tubules subunits do to microtubules?
Elongate it
308
What does subtracting of tubules subunits do to microtubules?
Shorten it
309
Describe the polymerisation and depolymerisation of microtubules:
1. Polymerisations
- B-tubulin is GTPase
- GTP bound tubules dimer gets added to "plus end"
- cap of GTP-tubulin stabilises growing molecule
2. Pausing
- If low amount of GTP-tubulin available process is paused and hydrolysis 'eats' the GTP-cap
- Tubulin hydrolyse bound GTP while microtubules polymerises
- When polymerisation slows down, the GTP-cap disappears
3. Depolymerisation
- Without GTP-cap, microtubule becomes unstable and depolymerises
- Moment of transition is called a catastrophe
4. Polymerisation
- GTP-tubulin can bind the shrinking microtubule and establish new cap
- Moment of transition is called a rescue event
310
What is dynamic instability of microtubules?
Microtubules constantly switch between growth and shrinkage
311
Describe the process of F-actin formation:
```
G-actin
to
Nucleation seed formation
to
F-actin
```
312
What does existing actin filaments show?
Treadmilling
313
What is treadmilling in actin filaments?
- Plus-end ATP bound G-actin can be added
- Minus-end ADP bound G-actin can be released
- Overal length is NOT changed
314
Where can you locate intermediate filaments?
Around the cell
| They have contact with desmosomes and other cytoskeleton
315
Is intermediate filaments less or more organised than the other filaments?
Less organised
316
What does intermediate filaments provide to the cell?
Mechanical strength
317
Intermediate filaments can be put into groups. What is the group on based on?
Central rod domain amino acid sequences, net acidic charge and secondary structure
318
Can several intermediate filaments xo-exist in the same cell?
Yes
319
What is the general function of intermediate filaments?
- Mechanical strength
- Organising cytoplasm
- Signalling
- Regulating transcription
320
What is shared by all types of intermediate filaments?
Domain structure
321
What does the coiled-coil of intermediate filaments consist of?
Alpha helices (around 2-3) wind around each other
322
What are the a helices often structures as?
Amphiphatic
323
What does a-helices in intermediate filaments being amphiphatic mean?
Protein interaction
324
Does intermediate filaments require ATP or GTP for assembly?
No
325
How does intermediate filaments assemble?
Self assemble into an apolar filament
326
What makes the nuclear lamina?
Intermediate filaments
327
What is the function of all lamina?
-Stabillity
-Organise
The nucleus
328
What occurs to intermediate filaments to able to reorganise?
intermediate filaments can disassemble into subunits to allow cell movement
329
What filaments make skin associated structures?
intermediate filaments
330
What skin like structure does B-keratin make?
Nails, scales and claws or reptiles, feathers, beaks
331
What skin like structure does a-keraton make?
Hair, horns and hooves of mammals
332
What is filament is a crucial part of you eye lens?
intermediate filaments
333
What does eye lens consist of that degrade their organelles?
Cells
334
How many types of intermediate filaments participate in development and function of vertebrate eye lens?
7
335
What do intermediate filaments determine in eye lens?
Optical properties
336
Does actin, microtubules or intermediate filaments consist of protein subunits?
Yes
337
Does intermediate filaments have more that one type of subunit?
Yes
338
Does actin, microtubules or intermediate filaments present in all eukaryotes?
Actin and microtubules
339
What eukaryotic cell is intermediate filaments present in?
Animal cell
340
Which filament actin, microtubules or intermediate filaments polymerise and depolymerise?
ALL
341
Which filament actin, microtubules or intermediate filaments cleave nucleoside triphosphate to control dynamics?
Actin and microtubules
342
Which filament actin, microtubules or intermediate filaments use phosphorylation to control dynamic?
Intermediate filaments
343
Which filament actin, microtubules or intermediate filaments provides stability?
All
344
Which filament actin, microtubules or intermediate filaments supports cell motility?
Actin and microtubules
345
Which filament actin, microtubules or intermediate filaments forms extracellular structures?
Intermediate filaments
346
What is another name for molecular motor?
Mechano enzymes
347
What is the purpose of molecular motor?
Transport vesicles and organ eels through cell
348
What are molecular motors?
Molecular scale of dimers or large proteins consistent of heavy and light chains
349
What does molecular motor utilise to walk along cytoskeleton?
ATP
350
How are molecular motor organised?
- Motor domain (2 heavy chains)
- Stalk (connects motor and cargo)
- Cargo-binding (light chains modify activity)
351
What are two different types of molecular motors?
- Microtubule - associated
| - Actin - associated
352
Give an example of microtubule-associated molecular protein:
Kinesin/Dynein
353
Give an example of actin-associated molecular protein:
Myosin
354
How can one prove that motors are mechanical-enzymes?
- Purified myosin molecules flushed underneath coverslips
- equally distributed, someone molecules attached to coverslip
- wash the solution to remove the molecules which are not attached
- add label actin filament (fluorescently labelled)
- actin filament interact with myosin
- Addition of ATP, actin motor protein walks along the actin filament
355
What direction do molecular motors move in?
Relative to charge
356
What direction does dynein move in?
Towards minus end
357
What direction does kinesis/myosin move in?
Towards plus end
358
Hoe can motor be grouped in to families?
By diverse functions
359
How may motor groups are there?
More than 25
360
How does kinesis walk along a microtubule?
- ATP interaction with motor head
- ATP binding leads to conformational change allowing other head forwards
- Head binds tightly to next tubules dimer ATP is cleaved
- New ATP comes along and head swings forwards
361
How are kinesis or dynein recycled?
Bind to cargo and actively or passively transported back
362
Can motors use more than one motor?
Yes
363
What does having more that one motor allow?
Allows long distance transport of vesicle
364
How do kinesis and dynein move to avoid collision?
Move differently
Dynein uses several filaments
Kinesin stays on same protofilamenst and moves in straight line
365
Does the nucleus move within the cell?
Yes
366
How does the colour of fish skin change?
Melanosome motility
| Dispersal and concentration depends on kinesis, dynein that move along the microtubule
367
What shapes endoplasmic reticulum?
Motors
368
How does endoplasmic reticulum reach nucleus to cell periphery?
Microtubules and kinesin organisation
Kinesis goes to plus end
369
How does Golgi apparatus stay concentrated at the nucleus?
Microtubules and dynein
Dynein goes to minus end
370
How does neurones cope with long distance?
- Axonal transports mediates motility in neurons
- Anterograde transport = negative end to positive end mediated by kinesin
- Retrograde transport = positive end to negative end mediated by dynein
371
What are the motor in muscle function?
Myosin motors
372
What % of you body is muscle?
40%
373
How much of muscle is protein?
20%
374
What does skeletal muscle mainly consist of?
Myosin and F-actin
375
How are muscles built?
Sarcomere -> muscle fibrille -> muscle cell -> muscle
376
What makes up a sarcomere?
Z-disc
Thin filament
Thick filament
377
What makes up a dark band of sarcomere?
Thick filament
378
What makes up a light band of sarcomere?
Z-disc
| Thin filament
379
What does thick filaments consist of?
Myosin II
380
What does thin filament consist of?
F-acton
381
When relaxed is there interaction between myosin and actin filaments?
No interaction
382
How is contraction controlled?
- Stimulus from neurons first over the plasma membrane of muscle cells
- Depolarisation of membrane release calcium from endoplasmic reticulum into cytoplasm
- Binding of calcium to tropic complex releases the block of myosin binding site on actin
- Myosin binds actin and walks towards Z-disc
- Calcium is removed by calcium pumps and myosin releases actin filaments
- Myosin releases actin and slide back (relaxation)
383
What does cardiac myocytes from?
Another type of straight muscle
384
How many times does the heart muscle contract over the course of a human lifetime?
3 billion
385
Is cardiac muscle organised?
No
386
What types of contractions do cardiac myocytes undergo?
Spontaneous contractions
387
Are flagella and cilia stationary or motile structures?
Motile
388
Do flagellum have a few or many per cell?
Few
389
Do cilium have few or many per cell?
Many
390
What do flagellum function in fluid/particle transport or cell locomotion?
Cell locomotions
391
What do cilium function in fluid/particle transport or cell locomotion?
Fluid and particle transport
392
What are cilia used for?
To move liquid within the body
393
What is the motion of flagellum?
Propeller-like motion
394
What is the motion of cilium?
Back and forth beating
395
How many beats per second do cilia beat?
12-30
396
How many beats per second do flagella beat?
10-40
397
What structural similarities do cilium and flagellum share?
- Axoneme (Core made of microtubules)
| - Basal body anchors structure at cell
398
What forms basal body of flagella?
Centrioles
399
What fo centrioles participate in?
Microtubule formation in interphase
400
What supports the formation and function of the cilium?
Intraflagellar transport
401
What travels along the axoneme?
Rafts
402
What drive bidirectional transport of rafts?
Kinesin and dynen
403
What is the ultrastructure of the standard cilium?
- 9x2 microtubules (next to each other)
- +2 microtubes in middle
- Outer arm dynein
- Inner arm dynein
- Radical spoke
404
Do dynein slide microtubules for or against each other?
Against
405
What occurs due to dynein sliding microtubule against each other?
Motor activity against protein bridges causes bending
406
Do most cells form motile or non-motile primary cilium?
Non-motile
407
How many primary cilium do many endothelial cells have?
One
408
What do primary cilium detect?
Signals that govern cell proliferation
409
Wha do primary cilium sense?
Flow and bending - triggering various regulation pathways
410
What are primary cilia essential for?
Developmental processes
411
Where can you find non-motile cilia in the human body?
- Inner ear
- Kidney
- Bile duct
- Pancreas
- Bone
- Eye
412
What is the main function of motile cilia?
Generating flow, cleaning surfaces
413
What is the main function of non-motile cilia?
Sensing environmental cues
414
How do motile and non-motile primary cilia differ?
- Motility
| - Number of microtubules pair
415
What sensing functions fo non motile cilia have?
- Chemosensation
- Mechanosensation
- Thermosensation
416
What does a stimulus result in?
Membrane depolarisation
417
What are found in eye retina?
Rods and cones
418
What are found in cilium in relation to the eye?
Rhodopsin discs
419
What are photo-receptor in the eye?
Specialised cilium
420
Do cones see in black and white or colour ?
Colour
421
How many cones do you have per retina?
4.5-6.5 million
422
How many rods do you have per retina?
110-130 million
423
Do rods seas in black and white or colour?
Black and white
424
Are actin dynamics involved in cell migration?
Yes
425
Where do you find a high concentration of actin?
At the tip of the cell
426
What are the stress fibres in a fibroblast like?
Contractile bundle
427
What are the cell cortex in a fibroblast like?
Gel-like network
428
What are filopdoium in a fibroblast like?
Tight parallel bundle
429
Where does treadmilling of actin occur?
At cell periphery
430
How do actin and actin-binding proteins move a cell?
1. Extension - Lamellipodium at leading edge moves forwards
2. Adhesion - new adhesion sites must established to move forwards
3. Translocation - causes contraction, end tail detaches (myosin interacts with actin moving against each other)
4. De-adhesion - adhesion site at rear gets dissolved
431
What helps healing wounds?
cell motility
432
What phase is mitosis of the cell cycle?
M Phase
433
What are the two different stages in M phase?
1. Mitosis (nuclei division)
| 2. Cytokinesis (cytoplasmic division)
434
What are inherited during mitosis?
Chromosomes
435
What are the different phases in mitosis?
```
Interphase
Prophase
Prometaphase
Metaphase
Anaphase
Telophase
```
436
What occurs at prophase?
- Chromosome condense
- Nuclear envelope disrupts
- Spindle is formed
437
What occurs at metaphases?
- Microtubules make contact with chromosomes
| - Chromosomes are position in one plane
438
What occurs at anaphase?
- Microtubules and motors pull on chromosomes
- Chromatids move to poles
- Rapid elongation of spindle fibres
- Formation of contractile ring
439
What occurs at telophase?
- Cell middle contact and separates (cytokinesis)
- Chromosomes decondense
- Nuclear envelope is formed
440
What distinct step do M phase occur?
- Chromosome alignment
- Chromosome separation
- Cell division
441
Why does the cell cycle have checkpoints?
Quality control
442
What are checkpoints?
Biological processes that recognise the status of the cell and control the transition from between cell cycle phases
443
What form the mitotic spindle?
Microtubules
444
What structures are involved in the organisation of the mitotic spindle?
- Centrosomes
- Kinetochor microtubules
- Polar microtubules
- Astral microtubules
445
What is formed when polar microtubules overlap?
Midzone
446
What interferes with the ability of microtubules?
Nocodazole
447
Do microtubules support chromosome serration in mitosis?
Yes, provide the force for chromosome segreafation
448
What is nocodazole?
A specific anti-microtubule drug
449
What mechanisms help microtubules provide the force for chromosome segregation?
Mechanism 1: De/polymerisation of microtubules
Exert force on attached chromosome
Mechanism 2: Molecular motors that act on the microtubules
450
What are the different motors in the spindle?
- Dynein
- Kinesin-14
- Kinesin-5
- Kinesin-4
- Kinesin-10
451
What does pulling on chromosomes exert?
Polar ejection force
452
What forms at the area of constrictions during mitosis?
Contractile ring
453
What is the contractile ring?
- Forms near the cortex at the end of anaphase
| - Contains myosin, actin, regulators and actin-binding proteins
454
At what stage of mitosis does the contractile ring form?
End of anaphase
455
What inhibits myosin II?
Blebbistatin
456
What does the inhibition of myosin II stop?
Cytokinesis
457
What does bebbistatin disturb?
Organisation of actomyosin ring
458
How does myosin II and actin make the contractile ring?
During early anaphase:
-Actin formed in middle of cell
-Actin is polymerised with plus end joined to plasma membrane
During late anaphase:
-Actin filaments recruits myosin II for local constriction
-Cell constricts until two cells are split in half
459
What are peroxisomes?
- Single-membrane bound organelles that contains man enzymes (crystalline core)
- Major sites of oxygen utilisation
- Scattered in the cell
460
Describe the model for peroxisome genesis:
-Site of formation at endoplasmic reticulum
-Precursor vesicle is formed acquiring cytoplasmic proteins and lipids by peroxisomal signal protein
-Fission splits structure into two
-
461
What are peroxisomes associated with?
Lipid droplets
462
How many different enzymes are contained in mammalian peroxisomes?
More than 50
463
How many peroxins are there on mammalian peroxisomes?
Over 20
464
What is detoxification in peroxisomes?
Generation of hydrogen peroxide which is degraded by catalase
465
What do peroxisomes play an important role in?
Lipid metabolism
466
What organelle plays a role in biosynthesis of cholesterol and break down of very ling chain fatty acids?
Peroxisomes
467
What converts fats into sugars in plant seeds?
Glyoxysomes
468
What are lipid droplets?
- Fat storage
- Vary in size and enclosed by a monolayer
- Organelles surrounded with membrane and protein involved metabolism in lipid droplets
469
What are nucleomorph?
DNA-containing relict of an engulfed eukaryote
470
Does algae contain nucleomorph?
Yes
471
Where are lipid droplets formed?
Endoplasmic reticulum
472
How are lipid droplets formed?
- Bilayer of smooth endoplasmic reticulum surrounds fatty acid
- Membrane formed and surrounded with proteins
473
What are fat-acid-binding protein?
- Makes fatty acid water soluble
| - Shield fatty acid by binding it in a hydrophobic pocket
474
What makes up 5% of all protein in liver cells?
Fat-acid-binding protein
475
What is a mitochondria?
- Double-membrane with an inner membrane fold
| - Produces ATP
476
What is the inner membrane fold called in mitochondria?
Cristae
477
What does mitochondria use to make ATP?
Sugars, fats, oxygen
478
What are essential functions of mitochondria?
- Producing ATP
- Fatty acid metabolism
- Control of programmed cell death/apoptosis
479
Why is ATP synthesised in the mitochondria?
Electrochemical garden over the inner mitochondrial membrane
480
How proposed the chemiosmotic hypothesis?
Peter D. Mitchell
481
Where is ATP synthesised?
Inner mitochondrial membrane
482
What does the breakdown of fatty acid and glucose result in?
NADH and FADH2
483
What does ATP synthase convert?
Energy of proton gradient into chemical-bond energy
484
Describe the steps in cellular respiration (OXIDATIVE PHOSPHORYLATION):
- NADH reaches complex I/FADH2 reaches complex II
- NADH --> NAD+ + H+ + e- / FADH2 --> FAD+ + 2H+ + e-
- Electron transferred into complex I or complex II ends up in CoQ
- Electron goes through complex II with the transfer of H+ to the inter membrane space then to CytoC
- Electron transferred to complex IV whilst again H+ pumped into intermembrane space creating a gradient of proton over membrane is formed
- 2H+ + O- --> H2O
- Protons flow through complex V to mitochondria matrix and ATP is formed
485
What is term for programmed cell death?
Apoptosis
486
What do mitochondria produce in low amounts of highly reactive molecules?
Reactive oxygen species (ROS)
487
How is ROS produced?
In mitochondria electrons not processed via complexes
- Stay in mitochondria matrix
- Electrons react with oxygen and produce ROS
488
What is ROS involved in?
Cell signalling that controls a broad range of cellular processes
489
What does a high quantity of ROS induce?
Apoptosis
490
What is apoptosis?
- In multi-cellular organisms
| - Mechanism by which cells die in a controlled way (building blocks recycled)
491
Why can apoptosis be advantages?
Separation of fingers and toes in a developing human embryo
492
How many cells on average die each day due to apoptosis?
50 and 70 billion cells
493
Describe the process of apoptosis:
- Stress triggers "apoptotic signalling"
- Apoptotic proteins cause damage to mitochondria which releases factors that activate atopic enzymes
- Enzymes cause blebbing and nucleus condenses
- Nucleus and DNA fragmentises
- Phagocytosis of apoptotic bodies by phagocytes
494
What is blebbing?
Myosin II process forming protrusions
