Tutor profile: Alyssa R.
Can you explain how to know if I should use the preterite or imperfect tense?
This is a tricky concept to grasp, but there are some tell tale signs when to know to use the imperfect tense. First off, when you are talking about a habitual event. For example, "Every weekend I went to my grandma's house." You would use the imperfect tense here because you are talking about a recurring event, or a habitual event. Also use imperfect when talking about time and age, when describing a setting or character, for incomplete actions, or for things that "used to" happen. For example, "I used run with my friend often." In order to fully understand imperfect, a lot of practice will be necessary, but these are some things to be keeping your eye out for!
How does the Electron Transport Chain result in the formation of ATP after glycolysis and the Citric Acid Cycle has occurred?
So the ECT (Electron Transport Chain) will result in the formation of ATP by creating a strong gradient of H+ across the mitochondrial membrane in the intermembrane space. FADH2 and NADH get oxidized, which releases energy that is used to move H+ across the membrane using active transport. The concentration of H+ is so large, that as it passes back through the membrane through ATP synthase, it releases enough energy to force together ADP + Phosphate to create ATP. There is a lot more going on in the ETC, but this is an overview of how it results in ATP.
How does tonicity affect cells? I.e. isotonic, hypertonic, and hypotonic solutions.
A cell wants to maintain regulated conditions, or homeostasis. Because of this, evolution has adapted cell's function to best suit their environment depending on the tonicity of its surroundings. But let's talk about tonicity as a very basic level, so we can understand how it functions in a controlled environment. Let's consider a cell that has no adaptation towards any certain tonicity. If that cell is in an isotonic solution (iso meaning equal) the cell size and rigidity will remain the same. If that cell is in a hypertonic solution (hyper meaning above) then the cell will shrink and become more limp. This is because there is a higher concentration of solute outside the cell, and water will therefore leave the cell to try and balance out the two concentrations. That the cell is in a hypotonic solution (hypo meaning below) then the cell will grow and become rigid or firm. This is because the concentration of solute outside of the cell is lower than inside, so the water from outside will go into the cell to balance out the concentrations. This is just a preview into tonicity, which is definitely more complicated than this intro, but this is how it works at a basic level.
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