How productive have I been? Not very. Remember that this is your life, one day at a time you are getting closer to where you will be. You can get that life that you want. The status, the impact, the renown, the influence, the admiration. It is hard. It is very hard. It will require every minute of every waking moment to get to where you want. There have been others before you that have overcome greater adversity to get to higher places.
Every decision you make takes you one step closer or farther from where you need to be. If you end up with nothing, it is your fault. Where you are right now in the exact moment of time - that is who you are. No need to apologize, no need to fantasize. Accept the truth and move forward. Don't set limits on how things are going to be. Don't have expectations of how things should be. Just take real actions and move forward. And then keep moving forward.
The most important thing is to just not give a fuck. Who cares if you look stupid? Who cares if you embarrass yourself? The only person that really cares is you, and you already hate yourself. This is you, this your life, and you are one minute closer to the end. What have i learned for the past 25 years? Life is fucking hard. It is beautiful, if you find that beauty. It is easy to squander. It is easy to have 7 years just pass you by without thinking twice about it.
You had a decently productive winter break, about 7/10. That is because you spent a lot of time become acquainted in the lab in addition to working a lot and do a few exercises and getting ready for your volunteering.
You can lift more, you can do more lab, you can read more. Remember, every decision makes you close to who you want to or who you should be.
Khan Academy MCAT prep looks pretty good.
Cell membrane overview.
- Small, non polar (O2 and CO2) are the fastest, followed by small polar, large non polar (slow) and large polar and charged molecules (not able to at all) in terms of rates of passive diffusion
- phosphate
+glycerol+ fatty acid = 5 types of phospholidpids, cis (with kink) vs trans (straight) fatty acids - phospholipid (cell permeability), cholesterol (changes fluidity), proteins (integral/transmembrane or peripheral, , membrane functions like receptors or molecular transport) and glycomolecules (communication)
- two types of integral proteins: carrier (against concentration gradient, yes ATP) and channel protein lets things pass through (down a concentration gradient, no ATP) and also peripheral, and lipid bound. Glycoproteins for signaling
- membrane fluidity: 1. temperature (low temp, crystallized, less) 2.cholesterol stabilizes the fluidity (inserts itself in between phospholipids, increases fluidity at low temp, at high temp, the phospholipids come together closer to the cholesterol, decreasing fluidity) 3. saturated (low) vs unsaturated fatty acids (higher)
- membrane dynamics, uncatalyzed, trans bi layer diffusion, "flip flop", slow, between leaflets. Also lateral diffusion, side to side, fast. The catalyzed movements are catalyzed by proteins. Uses ATP, similar to trans bi layer diffusion, catalyzed by protein (flippase) but outer to inner, fast. Another with floppase takes inner to outer and will be fast and with ATP. Scramblase does both flippase and floppase but does not need ATP
Cell-cell interactions
- cell junctions tight (complete fluid barrier, blocks everything from both sides, bladder, intestines, kidneys), desmosomes (attach inside of both cytoskeletons, attach two cells together, in between tight and gap, water and ions can flow in between the cell on the outside, space for stress relief, skin and intestines, spot welds), gap junctions (tunnel between cells, allow water and ions to flow within the junction between the cells, action potential cells or cells that use electrical coupling, cardiac cells, neurons)
- membrane receptors: integral proteins that communicate with the outside environment. ligand are neurotransmitter, or hormone or cell recognition molecule, they attach to membrane receptor and trigger a change within the cell. Ligand + membrane receptor = ligand receptor complex, they result in the intracellular response. Some pharm drugs can target only certain cells like liver because they associate with specific membrane receptor. Signal transduction. Ligand/receptor specificity (lock and key). New model is induced fit - receptors/ligand change conformation to fit. 1) ligand gated ion channels 2) g protein coupled receptors 3) enzyme linked receptors
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