Biochemistry

Water, Acids, Bases & Buffers: Water: -"Water is the solvent of life", it performs many functions: transport, component of chemical reactions, and control of body temperature.  - Body water is almost constant at about 60% of our weight. - Adipose tissue contains little water, so obese individuals have less body water, children have more. Note: Lean muscle mass contains a lot of water but adipose tissue contains very little.    Fluid Compartments:  -There is a total of 40L of total body water ; 25L of body fluid is INSIDE the cell (most fluid in the body found here)  15L of body fluid is found OUTSIDE the cell Note: Most of the water is found in the cells -Extracellular is split between interstitial & blood (interstitial is in between the cells)  -Often times, disease results from the water going to where it is not supposed to be.    Polarity of Water:  -The shared electrons of the H-O bonds are attached to the oxygen molecule. -This gives the hydrogen atoms a partial positive charge  - It also gives the oxygen atom a partial negative charge  Note: Water is POLAR  Polar things dissolve in water, non polar things repel water (ex.oil)  Lipids are made from C and H mostly, which share the charges nicely, so they are non polar. Sodium chloride is ionic (each atom has charge) so it is compatible with water. Water is constantly forming (and breaking) H-bonds:  Hydrogen Bonds: the attractive force between partially negatively charged O and partially positively charged H molecules.  IMPORTANT: H bonds are weak on their own, but strong when there are a lot of them together    Properties of Water: -The polarity of water allows polar molecules to dissolve  -Hydrogen bonds are formed with polar compounds and "hydration shells" surround ions. -Hydrogen bonds are weak, constantly breaking and reforming, so that solutes can move in solution and water can move through pores in cell membranes. Note: Water dissolves polar, or ionic compounds. It forms "hydration shells" around the molecule. Example: Sodium has a positive charge, so the partially negative ends of the water molecules will move to surround that. (with chlorine- which has a negative charge, it is the opposite.)  When it dissolves, they break apart, and move around so that they are all equally distributed so that the solution has a constant concentration. Osmosis: Water always moves to where the higher concentration of solute is   Thermal Regulation: -Water helps maintain body temperature in the narrow range compatible with life it is resistant to temperature change and can dissipate heat from areas that generate it such as the brain. -Water also maintains or dissipates heat when blood vessels in the skin constrict or dilate, respectively.  Note: On a hot day- Sweating occurs, vessels at the top of the skin open and allow heart to dissipate. On a cold day- Vessels close to top of skin are contracting to keep the heat in.  Body temperature needs to stay in a normal range for good health.    Electrolytes & Osmolality:  -Electrolytes are anions (Cl-, HCO3-, Po4(2+) and cations (K+, Na+)  -Osmolality is the concentration of all dissolved solutes in the blood (electrolytes, proteins, etc...)  -Water  will move between compartments to keep the osmolality the same. Note:  Electrolytes: substances in the blood that have a charge Potassium is the major intracellular cation. Sodium is the major extracellular cation. K-Na pump Osmolality: sum total of all the substances dissolved in the blood  if this is off, water moves to dilute higher concentration. In the vessels there is blood flowing through, and when you get down to the capillary beds (the arterial end) there is higher pressure --> forces some of the fluid out In the venous end, there is less pressure --> so that water will move back in.   pH: -pH is a measure of the acidity or alkalinity of a solution -pH=-log[H+] -pH in the blood must be maintained in a narrow range -Most living cells have a very narrow range of tolerance for pH, (ex. [H+])  -the [H+] concentration will be important (either explicitly or implicitly) for many other topics in biology. -[H+] is controlled in all biological organisms, and in virtually all biochemical experiments. -Each pH unit represents a factor of difference in [H+]. Note: It moves opposite because it is negative