Midterm 2 Bioc 212 Flashcards
What are the pros and cons of Confocal microscopy?
Pros:
1) 3-dimensional rendering of cells
2) Live cell imaging
3) Multiple snapshots per second
4) Can view and track them
Cons:
1) Limitation of specificity of markers
2) “co-localization” only implies co-function
3) Limited by the resolution ability because the wavelength of light is larger than the protein.
4) The wavelengths can be bleached because of over exposure.
What is the definition of resolution and in the context of electron microscopy?
Resolution is the ability to see that there are two separate objects. In electron microscopy, it provides the means to evaluate the quality of macromolecular structures computed from sets of their two-dimensional line projections.
How do we get energy?
Bacteria uses their two membranes (inner and out) to figure out a way to create a potential, separating and concentrating things, to create a gradient. This releases a gradient and you can use that energy, which is either potential or kinetic to generate a chemical energy source. Mammals use specialised organelle mitochondrion, plants do it using chloroplast.
What is respiration?
- Takes energy from food and derives electrons from it, pumps the protons into separate components and creates a gradient, when the protons are released we use them to derive electrical energy.
- Photosynthesis does this in reverse, and it also generates the gradient to generate the energy.
What is the energy cycle in Mitochondrion? What is the different between what is happening here vs in the Chloroplast?
At mitochondrion, there is fat, carbohydrate and protein degradation.
Once degraded, we can create substrate and break it down further.
Taking the sugar, six molecules of carbon in glucose and converting it to carbon dioxide.
We also need oxygen (terminal acceptor of electron transport chain), if we do not have it, the whole system will fall apart. Take all the carbon sources and pump them into the citric acid cycle, we convert the carbon sources into carbon dioxides, 6 in and 6 out, in the meantime we are reducing other things.
There is redox reaction creating the reduction equivalents (NADH holders of electrons), pass them into the electron transfer chain, couples transfer of electrons with pumping of protons which then creates a gradient, which we can now use to generate ATP from.
Final acceptor of electron is 02 which creates water.
Glucose and oxygen in.
Carbon dioxide and water out.
(Cell respiration)
In the chloroplast, the opposite takes place. Carbon dioxide and water is coming in and glucose and oxygen is coming out. The purpose of this cycle is to fix carbon and make sugars. (photosynthesis)
Where does cell respiration take place?
1) Cardiac Muscle. It can never stop and it beats every second of our life. It needs energy to beat and it is filled with mitochondria.
2) Sperm tail, they have to go there and do their job, and needs lots of energy. You can see mitochondria wrapped around the tail of the sperm.
What is Cristae?
- The inner membrane of mitochondria folds up into little loops called Cristae. These are important regions and there is a lot happening here. They provide a large amount of surface area for chemical reactions to take place on.
What tissue has a lot more mitochondria than another tissue and why?
Muscle tissues have a lot more mitochondria than adipose tissue which is fat. This is because fat does not need/have as much energy as muscle tissue.
Mitochondria undergo fission and fusion events, they are elongated (even though we draw them as ovals). Why would we want mitochondria to undergo these mechanisms?
- They could potentially undergo oxidative stress and not be well. So they need a fission event to throw all the garbage in one part of the mitochondria so they can cut it out and bring to lysosome for degradation (autophagy)
- They could sometimes fuse, during the cell cycle, this happens many times, they want to share recourses between mitochondria, there are specific proteins involved in this process.
What is an example of Mitochondrion undergoing a fission event?
- There is a protein called Dynamin (GTP dependent protein) that forms a polymer that wraps around the centre of mitochondria and eventually constricts it so it pops apart.
- There is GTP dependent constriction of microtubules mediated by Dynamin protein.
What is an example of cells fusing? (muscle cells)
There are myoctes, which fuse to form long muscle fibres of arms/legs. Once cell forms with others and becomes longer. They need to become longer. They need to get rid of nuclei, and the mitochondria also needs to fuse.
Describe the process of generating ATP by eating food.
Here we have the outer and inner mitochondrial membrane. It takes place in the cristae and mitochondial matrix (where most of the business is happening)
There is a carbon source (amino acids, fatty acids, pyruvate) or ketone bodies - which we use in the place of glucose in disease/starved states and we use as energy in the brain/RBCs.
All of these are used to derive Acetyl CoA (2 carbons and a tail) and we put it into the citric acid cycle. There is an enzyme called citrate synthase that combines with acetyl CoA (2 carbons) and Oxloacetate (4 carbons). We have now created a 6 carbon compound called citrate.
Citrate undergoes enzymatic steps and looses 2 carbons, the 2 carbons that came in acetyl CoA come out as carbon dioxide and we have generated 1 GTP, 2 NADH, and 1 FADH2.
For every NADH we have 3 ATP, and for every FADH2 we have 2 ATP. NADH is an electron carrier, we can donate electrons to the electron transport chain. It gets passed through different complexes and we pump 1 protein each time from the matrix inside to the inter-membrane space. We can use those protons to drive the formation of ATP.
It Acetyl CoA glucogenic?
It is not glucogenic, it cannot be turned back to glucose. The main reason for this is because there has been a mechanism developed where we maximise energy and we sacrifice the ability to regenerate as a result.
What are some important functions that the mitochondria has?
- Generate ATP through oxidative phosphorylation.
- Regenerates NAD+ which is an electron carrier
- Provision of precursors for biosynthesis of amino acids, nucleotides, fatty acids
- Participation in synthesis of heme and iron-sulfur clusters
- Cell signalling
- Generation of reactive oxygen species
- Regulation of apoptosis (many reasons for cells needing to die, a reason is if telomeres are too short. In the retina, when you wake up a layer of cells undergo apoptosis, this is why you cannot see right away when you wake up, fresh cells come in. Also during development, when you are very young, it looks like you have 5 fingers, but there is innervation and the skin between them is removed)
What is an example of a specialized phospholipid?
1) Cardiolipin. It takes a much broader position, if you look at the shape, they are usually cylinder shaped. This is because the two phospholipids joined via the second glycerol, it spreads out more and has a cone shape, a bigger tail than head group. It actively binds one or more complexes of the electron transport chain. If it is not there, they do not stick together, and you cannot get a proper electron transport chain. This is very essential for efficient mitochondrial electron transport function.
