Life at the cellular level 4

Question 1

what are the general properties of water? (6)

Answer 1

• bathes cells (interstitial fluid)
• dissipates heat
• acts as a solvent
• participates in chemical reactions
• can hydrogen bond
• can stabilse enzyme substarte reactions (though H-bonding)

Question 2

what is the hydrophobic effect?

Answer 2

hydrophobic molecules aim to minimise disruption to hydrogen bonding by allowing cages of water to form around hydrophobic molecules

Question 3

what is a chylomicron?

Answer 3

a complex that transports hydrophobic lipids in the bloodstream

Question 4

what is Kw?

Answer 4

a constant that represnts the extent to which water dissociates
(= 1x10^ -14)

Question 5

what is Ka?

Answer 5

the tendency for an acid to lose its proton

Question 6

what is the equation for Ka?

Answer 6

Ka = [H+][A-] / [HA]

Question 7

how do buffers work?

Answer 7

• if extra acid is added it reacts with the A- to remove the extra hydrogen ions helping to maintain the pH
• if a base is added the OH- reacts witht he H+ ions and so more HA dissociates to replace the H+ ions lost maintaining the pH
• this can only occur until all of the A- or HA has reacted

Question 8

what is the henderson-hasselbach equation?

Answer 8

pH = pKa + log ([A-]/[HA])

Question 9

name some common buffers present in the body

Answer 9

• phosphate buffers: H2PO4 –> H+ + HPO4(^2-)

- bicarbonate buffers: H2CO3 –> H+ + HCO3(^1-)

Question 10

how do buffers help with drug absorption?

Answer 10

in the stomach a weak acid will be largely unprotanted (uncharged) which makes it easier for it pass through cell membranes