1
Q
What is one technique used to study cell biology?
A
• Biochemistry
- Whole cell extracts
- ‘Destroyed’ the cell
- Fractionation
- In vitro assays (cell free)
2
Q
What are forward genetics?
A
phenotype is known,
gene (genotype) is unknown
3
Q
What is reverse genetics?
A
Gene is known, determine
role of the gene and the phenotype of mutations.
4
Q
What is cell biology?
A
study of processes e.g. cll growth, division and maintenance. By maintenance we mean a cell us able to maintain itself shape and function.
Processes are controlled by mechanisms . Regulated system which can respond to intracellular and extracellular signals (other cells or surrounding environment).
5
Q
What do the signals enable the cell to do?
A
signals enable the cell to maintain itself in its environment.
- where this is a unicellular organism or wthether you are looking at a cell within a multicellular organism.
- How those cells respond within the context of the organ to enable the shapeof the organ and the shape of the organism itself to function and form correctly.
6
Q
Why are cells complex and dynamic?
A
Whole cell level.
- -Changes in morphology.
- -Complex at intracellular levels.
7
Q
Explain biochemistry in more detail.
A
Cells are lysed and destroyed and they are open.
- –contents are then extracted and are separated out into fractions. so this is usually the process. Whereby the contents of the cell are loaded onto a gradient.
- –This is then spun and the samples then separate out into different fractions according to their density within the gradient.
8
Q
What is another technique is used to study cell biology?
A
• Genetics
- Mutants versus control wild type- changes in proteins.
- Looking at mutants helps us to understand how mutants can change the function of a particular protein.
- Relationship between genotype and phenotype
9
Q
What is the context of imaging cells through microscopy?
A
To understand a particular process in a cell.
• The naked eye can only directly perceive the first two panels
• The resolution of the light microscope takes you to the 4th panel
• The electron microscope takes you to the 7th/8th panel
• X-ray crystallography allows you to go to the 9th
10
Q
Anything under ____ distance then you need to use a microscope.
A
2mm
11
Q
Why are microscopes important?
A
They magnify detail within a sample, and so light microscopes enable you to look at detail within a sample down around to the 200/250micrometer size.
12
Q
What would you use when looking at things closer than 200/250μm apart?
A
Electron microscope
13
Q
What would you use to look at how a protein folds/interacts with another?
A
Use an x-ray or crystallography.
14
Q
What is something you cant see under a light microscope?
A
Thylakoids
15
Q
What are the properties of microscopy?
A
- Observe ultrastructural detail
- Electron microscopy (resolution < 250nm)
- Transmission electron microscopy (TEM):
electrons pass through the sample. - Scanning electron microscopy (SEM):
electrons emitted from the surface of an
object shows topography
16
Q
Cell biology studies the
A
processes and mechanisms of cells
17
Q
Why is the cytoskeleton important?
A
dynamic structures, provide mechanical strength
18
Q
How do proteins reach there final destinations?
A
Proteins reach their final destination due to signal sequences (amino acid
‘postcodes’)
19
Q
What aids the transport to final destinations?
A
• Interaction with receptors aids transport to final destination
20
Q
How do proteins move?
A
• Proteins can move via sorting or in vesicles
21
Q
How is vesicle formation ordered and controlled?
A
Vesicle formation is ordered and controlled by a set of proteins which bend
the membrane, pinch off the vesicle and coordinate delivery
22
Q
Why is protein movement required?
A
Protein movement is therefore regulated and coordinated, and is required
for subcellular organisation
23
Q
How is swimming/ movement achieved?
A
: flagella and cilia
24
Q
How is crawling achieved?
A
: protrusion, attachment, traction
25
What is swimming and crawling dependent on?
Both dependent on cytoskeleton
26
How is organelle movement regulated and controlled?
- Regulated and controlled by cytoskeletal ‘tracks’ (actin and microtubules) and corresponding motor proteins (myosin, kinesin and dynein)
27
What is Protrusion?
- Actin polymerisation pushes the
| plasma membrane out
28
What is attachment?
- Extended cell becomes attached
29
What is traction?
- Trailing cytoplasm is ‘pulled’ forward
30
How is organelle movement achieved?
• Movement is controlled by 2 broad themes;
• Cytoskeleton and associated motor
proteins
• Tethers to hold organelles together ‘piggybacking
31
What do Motors – mechanoenzymes do?
turn chemical energy (ATP) into mechanical energy
32
What do ATP or ADP binding help with?
* ATP or ADP binding changes conformation of the motor
* Allows it to ‘walk’ along the cytoskeletal track
* ‘Pulls’ the cargo eg organelle
33
Cytoskeletal ‘tracks’ have a
polarity – plus and minus ends
34
Which direction does Kinesin and Dynein motors move along microtubules?
- Kinesin generally move towards MT plus ends
| - Dynein generally move towards MT minus ends
35
What are the functions of the cytoskeleton?
- -To assemble ribosomes
- -To provide scaffolding for the enzymes in certain areas of the cell
- -To organize the cell's activities
- -To provide movement of molecules in the cell
- -To provide the cell shape
36
The movement of vesicles along microtubules involves which of the following?
Dynein and Kinesin are motor proteins that move along a microtubule. Vesicles attach to these proteins and ATP is required for the motion.
37
```
What is the definition of the following:
1-cell division
2-Pattern formation
3-Differentiation
4-morphogenesis
```
1-Increasing the number of cells without increasing size/the formation of many cells from one cell.
2-Orientation of cells by the detection of positional information/ cells become oriented to the body plan by detecting positional cues to guide their fates
3-Cell specialization through selective gene expression/differential gene expression in cells leads to different cell types
4-Cell death, cell division, and differentiation are all aspects of this process which establishes body form/the formation of organs and anatomical features).
38
What are some aspects of Neurulation?
- -Development of dorsal nerve cord.
- -Ectodermal cells thicken to form a plate.
- -contracting actin filaments cause a groove to form.
- -A tube forms from the fusion of 2 edges of tissue.
- -Hox gene complexes regulate regional change.
39
What are some aspects of Somitogenesis?
- -Occurs from changes in mesoderm.
- -Forms on an anterior-posterior wave.
- -structure may be transient.
- -pattern is species-specific.
- -skeleton, skeletal muscles, and associated connective tissue structures are formed.
- -bands of mesoderm run laterally giving rise to other organs.
40
Describe the structure of hemoglobin.
- -Each heme group has a central Cu2+ ion.
- -Hemoglobin binds with O2 to transport it to the tissues.
- -Four alpha chains are present.
- -Four polypeptide chains are present.
41
What are characteristics of hemolymph?
It contains circulatory fluid
- -It contains extracellular fluid.
- -It drains into a central cavity
42
What is the definition of the following?
protrusion -
Attachment-
Traction-
protrusion - cell extends
Attachment- extended part of the cell attaches
Traction- the rear end of the cell is then pulled forward
43
How does a cell become polarized?
At this leading edge, within the lamellipodia the actin is rearranging to enable the cell to push forward and push that cell to move in a particular direction. The actin will polymerise and then depolymerise from the back and these monomers will then move towards the front of the cell toward the leading edge and allow new polymerization to occur. As the polymerization of the actin filaments occurs, it then pushes the cell formward.
44
What happens when a cell becomes polarized?
Cells within the multicellular organism will polarize, they will change their shape and move towards an external signal and that this is controlled within the organism by interaction of the surface of the cell with receptors which target its destination, its interaction with this new area.
45
What are aspects of the flagella and cilia?
So flagella and cilia are made up of microtubles, in both this is made up of a central core which is called an axoneme. And the axoneme is an arrangement of multiple microtubules. An axoneme is made up of an arrangement of microtubules called 9+2. 2 refers to the two central microtubules and around these are the additional 9 structures and these 9 structures contain a doublet microtubule and the doublet microtubule is not two separate microtubules joined together. One is a complete microtubule and the other one is an incomplete microtubule, theyre joined together. Radiating out from these microtubules are these dynein arms- a motor protein that enables it to attach to a microtubule and walk along the length of the microtubule. Dynein will walk towards the minus end of the microtubule, enabling microtubules to slide over one another.
46
Why does the cell need to move towards signals?
in order to feed.
47
What is the extracellular matrix in plants?
In plants the extracellular matrix is actually called the cell wall and in plants cells do not move, they stay in the same position. They divide, they change shape, but they do not move and migrate within the body in the same way as they do within mammals. Apart from pollen tubes that move
48
Outline protein targeting in the nucleus.
So protein that is being imported binds to the importin receptor, which then takes this complex- and moves to the nucleopore. This then passes through the nucleopore through interaction of the receptor with various proteins within the nucleopore- so controls that process, which enables that protein to pass into the nucleus. Once in the nucleus the cargo-complex, unbinds as Ran-GTP binds to the importin. Results in the cargo being released into the nucleus. The importin protein, the receptor binds Ran-GTP and this then triggers the recycling or exports of the receptor back into the cytosol. Once in the cytosol Ran-GTP encounters the protein which enables Ran to be transformed from a GTP bound to GDP bound form and the Ran-GDP then separates from the receptor.
49
What are exports and what is there function?
Exports- this protein has a nuclear export signal. Which binds to the receptor and the receptor here is an exporting and is bound to Ran-GTP. When exportin is bound to Ran-GTP, this promotes cargo binding. Complex exported into cytosol, when there the GTP on Ran is hydrolysed to form Ran-GDP which then enables the receptor cargo complex to dissociate. Nuclear export can be recycled back.
50
Outline protein targeting in the ER.
This signal sequence recognises a signal recognition particle, so the signal recognition particle is the receptor. The receptor, the signal recognition particle recognises the signal sequence the targeting sequence on the proteinwhich is being translated is destined to be associated with the ER. Now when this association occurs between signal sequence and signal recognition particle this causes translation of that protein to be pasued, it halts the translation. This whole complex and the ribosome moves and is targeted to the ER. SRP this signal recognition particle, this protein is actually recognised by another receptor in the membrane- this enables this complex of SRP, the ribosome and the protein mRNA which has been translated into this protein which is being targeted to the ER, it recognises it and docks the ribosome of the surface of the ER. This enables the translation of the protein to resume and this protein which emerges is then passed into the ER through the protein translocator, which is another protein. As translation continues it can then either pass through and into the ER, it can be a soluble protein which exists inside of the ER, or it could be a protein which is actually passed and then resides within the membranse of the ER- controlled by the signal recognition sequence which releases the protein into the nucleus or it can be used to enable the protein to pass laterally into the membrane. SRP is recycled.
51
What is a donor compartment?
Donor compartment is one organelle e.g. golgi. Vesicles from DC form, bud off, these vesicles then move to their target compartment. The vesicle then fuses with the target compartment and releases its contents into the target compartment. And so this process requires the vesicle to form by curvature of the donor membrane. Proteins could be soluble proteins or they could be proteins in the membrane of the DC. they proteins are released into the target compartment.
52
Why do vesicles move and fuse with the target membrane?
Vesicle moves and fuses with the target membrane and releases its contents, so it releases the molecule within the vesicle to the exterior of the cell so it secretes those molecules. Results in the membrane of the vesicle incorporating the surface of the vesicle into the plasma membrane . you can then change the protein content on the surface of the cell by incorporating the surface of the vesicle into the plasma membrane itself.
53
How does the cell maintain the size of its SA?
The cell might not want to increase in size and so if it wants to maintain the size of its SA, the size of the plasma membrane, then it also needs to internalize the surface of that cell, and so this process is called endocytosis. Curvature is changing in order to internalizes the molecules. Maintains SA of the cell.
When a vesicle forms on the surface of DC, coat proteins are recruited to the surface of that DC and this specifies and these coat proteins are specific for certain donor compartments. We have COP1, COP11 and Clathrin and so these help form and define a vesicle.
Vesicle trafficking occurs between organelles which are part of the endomembrane system.
Vesicles that move from the ER to Golgi involve COP11, golgi to ER- controlled by COP1.
Life Processes
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