Life at the Cellular Level 4

Question 1

<p>What does water being a polar molecule allow it to do?</p>

Answer 1

<p>Bathe our cells</p>

<p>Dissolve and transport compounds</p>

<p>Allows compounds to move within and between our cells</p>

<p>Participate in chemical reactions</p>

<p>Dissipate heat</p>

Question 2

<p>Why is water polar?</p>

Answer 2

<p>Because O is more electronegative than H so it attracts the electrons of the covalent bond towards it causing partial charges</p>

Question 3

<p>What kind of bonds can water form due to being polar?</p>

Answer 3

<p>Hydrogen bonds</p>

Question 4

<p>What kind of molecules can form hydrogen bonds?</p>

Answer 4

<p>Any that contain electronegative atom bonded to H which is electropositive</p>

Question 5

<p>What do hydrogen bonds determine due to linking molecules in precise patterns in space?</p>

Answer 5

<p>3D structure</p>

Question 6

<p>Are bent or linear hydrogen bonds the strongest?</p>

Answer 6

<p>Linear</p>

Question 7

<p>Are molecules that can form hydrogen bonds water soluble or insoluble?</p>

Answer 7

<p>Water soluble</p>

Question 8

<p>What are some examples that can form hydrogen bonds?</p>

Answer 8

<p>Sugars</p>

<p>Alcohols</p>

<p>Aldehydes</p>

<p>Ketones</p>

<p>Compounds with N-H groups</p>

Question 9

<p>What happens when molecules with hydrogen bonds are dissolved in water?</p>

Answer 9

<p>Water-water hydrogen bonds and solute-solute hydrogen bonds are replaced with more energetically favourable solute-water hydrogen bonding</p>

Question 10

<p>Why are O₂and CO₂poorly water soluble?</p>

Answer 10

<p>O=O and O=C=O have no polarity</p>

<p>End molecules in the straight line are the same so no partial charge</p>

Question 11

<p>Why is O₂carried by haemoglobin and CO₂floats around as bicarbonate?</p>

Answer 11

<p>Because they are poorly water soluble</p>

Question 12

<p>Are charged molecules water soluble?</p>

Answer 12

<p>Yes, water forms 'screens' around each ion</p>

Question 13

<p>What is the hydrophobic effect?</p>

Answer 13

<p>Tendency of nonpolar substances to aggregate in an aqueous solution and exclude water molecules</p>

Question 14

<p>How do non polar molecules arrange themselves in water?</p>

Answer 14

<p>To minimise disruption of hydrogen bonding amount surrounding water molecules, because this is the most energetically favourable arrangement</p>

Question 15

<p>What does amphipathic mean?</p>

Answer 15

<p>Contains both hydrophobic and hydrophillic parts</p>

Question 16

<p>How do phospholipids minimise water-water hydrogen bonding?</p>

Answer 16

<p>By forming bilayers</p>

Question 17

<p>Why do proteins fold in on themselves?</p>

Answer 17

<p>So hydrophobic regions are on the inside and hydrophillic are on the outside, allowing them to be water soluble</p>

Question 18

<p>How are hydrophobic lipids transported in the blood?</p>

Answer 18

<p>In a chylomicron (phospholipid surface, triacylglycerols stored inside)</p>

Question 19

<p>How does water weakly dissociate?</p>

Answer 19

<p>H₂O⇔ H⁺+ OH^-</p>

Question 20

<p>What does dissociate mean?</p>

Answer 20

<p>Molecule splits into smaller pieces</p>

Question 21

What equation describes the equilbrium of water?

Answer 21

Question 22

<p>Why can the equilbrium of water equation be expressed as this?</p>

<p>K_w= [H⁺][OH^-]</p>

<p></p>

Answer 22

<p>Because the concentration of H₂O is very high and essentially constant so it can be removed from the original equilbrium of water equation</p>

Question 23

<p>What is K_wknown as?</p>

Answer 23

<p>The ionic product of water</p>

Question 24

<p>What is the value of K_w?</p>

Answer 24

<p>1x10^-14</p>

<p>The ratio of H⁺and OH^-in pure water is 1:1 so:</p>

<p>[H⁺] = [OH^-] = 1x10^-7mol/L</p>

Question 25

<p>Why do we use the log to express the concentration of H⁺inwater?</p>

Answer 25

<p>Because the concentration is so small, we use the negative log to avoid negatives:</p>

<p>-log[H⁺] = -log[OH^-] = 7</p>

<p>The negative log is appreciated to pH and pOH</p>

<p>pH = pOH = 7</p>

Question 26

<p>Why does water have a neutral pH?</p>

Answer 26

<p>Because the concentration of H⁺and OH^-is the same</p>

Question 27

<p>What is an acid?</p>

Answer 27

<p>A molecule capable of donating a proton</p>

<p>pH < 7</p>

<p>Greater concentration of H than OH</p>

Question 28

<p>What is a base?</p>

Answer 28

<p>Molecule capable of accepting a proton</p>

<p>pH > 7</p>

<p>Greater concentration of OH^- than H⁺</p>

Question 29

<p>What does an increase or decrease of 1pH represent?</p>

Answer 29

<p>A ten fold increase or decrease of [H⁺]</p>

Question 30

<p>What does pH + pOH equal?</p>

Answer 30

<p>pH + pOH = 14</p>

Question 31

<p>What is a strong acid/base, giving an example of each?</p>

Answer 31

<p>One which fully dissociates</p>

<p>HCl is a strong acid</p>

<p>NaOH is a strong base</p>

Question 32

<p>What is a weak acid/base, giving an example of each?</p>

Answer 32

<p>One which partly dissociates</p>

<p>Lactic acid is a weak acid</p>

<p>Ammonium hydroxide is a weak base</p>

Question 33

<p>What is a congugate acid?</p>

Answer 33

<p>Spieces after a base accepts a proton</p>

Question 34

<p>What is a congugate base?</p>

Answer 34

<p>Spieces after an acid donates a proton</p>

Question 35

<p>What makes up the conjugate acid/base pair?</p>

Answer 35

<p>A proton donor and the corresponding acceptor</p>

Question 36

<p>Does a strong or weak acid have a greater tendency to lose its proton?</p>

Answer 36

<p>The stronger an acid the greater its tendency go give up its proton</p>

<p>HA⇔H⁺+ A^-</p>

Question 37

<p>The tendency of an acid to lose its proton is defined by what? What expression describes this?</p>

Answer 37

<p>The equilbrium constant (K_eq) or acid dissociated constant (K_a)</p>

<p></p>

Question 38

<p>What are pK_avalues?</p>

Answer 38

<p>The negative log of K_avalue</p>

<p>pK_a= -logK_a</p>

Question 39

<p>What is a buffer?</p>

Answer 39

<p>Mixture of a weak acid and its conjugated base which can resist pH changes from the addition of an acid or base</p>

Question 40

<p>What two equilbriums are going on in a solution of a weak acid?</p>

Answer 40

<p>H₂O⇔ H⁺+ OH^-</p>

<p>HA⇔ H⁺+ A^-</p>

Question 41

<p>What are the steps of a titration curve of a weak acid?</p>

Answer 41

<ol> <li>As NaOH is added the OH^-combines with free H⁺to make H₂O</li> <li>HA dissociates further to replace the lost H⁺and maintain equilbrium</li> <li>Process continues and more HA ionises to A^-</li> <li>At midpoint pH = pK_a, beyond this HA continues to be used up until all of it is ionised to A^-</li></ol>

Question 42

<p>What happens to the pH during the buffering region?</p>

Answer 42

<p>pH barely changes with a large input of an acid or base</p>

Question 43

The Henderson-Hasselbalch equation relates the acid dissociation equation to the bufffering ability of a week acid/conjugate base, what does this look like?

Answer 43

Question 44

<p>What are important buffers in the body?</p>

Answer 44

<p>Phosphate</p>

<p>Bicarbonate</p>

Question 45

<p>Why are buffers important in the body?</p>

Answer 45

<p>They maintian physiological pH when acids and bases are added</p>