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Science for Medicine > Life at the Cellular Level 4 > Flashcards

Life at the Cellular Level 4 Flashcards

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1
Q

What does water being a polar molecule allow it to do?

A

Bathe our cells

Dissolve and transport compounds

Allows compounds to move within and between our cells

Participate in chemical reactions

Dissipate heat

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2
Q

Why is water polar?

A

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

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3
Q

What kind of bonds can water form due to being polar?

A

Hydrogen bonds

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4
Q

What kind of molecules can form hydrogen bonds?

A

Any that contain electronegative atom bonded to H which is electropositive

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5
Q

What do hydrogen bonds determine due to linking molecules in precise patterns in space?

A

3D structure

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6
Q

Are bent or linear hydrogen bonds the strongest?

A

Linear

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7
Q

Are molecules that can form hydrogen bonds water soluble or insoluble?

A

Water soluble

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8
Q

What are some examples that can form hydrogen bonds?

A

Sugars

Alcohols

Aldehydes

Ketones

Compounds with N-H groups

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9
Q

What happens when molecules with hydrogen bonds are dissolved in water?

A

Water-water hydrogen bonds and solute-solute hydrogen bonds are replaced with more energetically favourable solute-water hydrogen bonding

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10
Q

Why are O2 and CO2 poorly water soluble?

A

O=O and O=C=O have no polarity

End molecules in the straight line are the same so no partial charge

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11
Q

Why is O2 carried by haemoglobin and CO2 floats around as bicarbonate?

A

Because they are poorly water soluble

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12
Q

Are charged molecules water soluble?

A

Yes, water forms ‘screens’ around each ion

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13
Q

What is the hydrophobic effect?

A

Tendency of nonpolar substances to aggregate in an aqueous solution and exclude water molecules

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14
Q

How do non polar molecules arrange themselves in water?

A

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

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15
Q

What does amphipathic mean?

A

Contains both hydrophobic and hydrophillic parts

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16
Q

How do phospholipids minimise water-water hydrogen bonding?

A

By forming bilayers

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17
Q

Why do proteins fold in on themselves?

A

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

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18
Q

How are hydrophobic lipids transported in the blood?

A

In a chylomicron (phospholipid surface, triacylglycerols stored inside)

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19
Q

How does water weakly dissociate?

A

H2O ⇔ H+ + OH-

20
Q

What does dissociate mean?

A

Molecule splits into smaller pieces

21
Q

What equation describes the equilbrium of water?

A
22
Q

Why can the equilbrium of water equation be expressed as this?

Kw = [H+][OH-]

A

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

23
Q

What is Kw known as?

A

The ionic product of water

24
Q

What is the value of Kw?

A

1x10-14

The ratio of H+ and OH- in pure water is 1:1 so:

[H+] = [OH-] = 1x10-7mol/L

25
Q

Why do we use the log to express the concentration of H+ in water?

A

Because the concentration is so small, we use the negative log to avoid negatives:

-log[H+] = -log[OH-] = 7

The negative log is appreciated to pH and pOH

pH = pOH = 7

26
Q

Why does water have a neutral pH?

A

Because the concentration of H+ and OH- is the same

27
Q

What is an acid?

A

A molecule capable of donating a proton

pH < 7

Greater concentration of H than OH

28
Q

What is a base?

A

Molecule capable of accepting a proton

pH > 7

Greater concentration of OH- than H+

29
Q

What does an increase or decrease of 1pH represent?

A

A ten fold increase or decrease of [H+]

30
Q

What does pH + pOH equal?

A

pH + pOH = 14

31
Q

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

A

One which fully dissociates

HCl is a strong acid

NaOH is a strong base

32
Q

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

A

One which partly dissociates

Lactic acid is a weak acid

Ammonium hydroxide is a weak base

33
Q

What is a congugate acid?

A

Spieces after a base accepts a proton

34
Q

What is a congugate base?

A

Spieces after an acid donates a proton

35
Q

What makes up the conjugate acid/base pair?

A

A proton donor and the corresponding acceptor

36
Q

Does a strong or weak acid have a greater tendency to lose its proton?

A

The stronger an acid the greater its tendency go give up its proton

HA⇔H+ + A-

37
Q

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

A

The equilbrium constant (Keq) or acid dissociated constant (Ka)

38
Q

What are pKa values?

A

The negative log of Ka value

pKa = -logKa

39
Q

What is a buffer?

A

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

40
Q

What two equilbriums are going on in a solution of a weak acid?

A

H2O ⇔ H+ + OH-

HA ⇔ H+ + A-

41
Q

What are the steps of a titration curve of a weak acid?

A
  1. As NaOH is added the OH- combines with free H+ to make H2O
  2. HA dissociates further to replace the lost H+ and maintain equilbrium
  3. Process continues and more HA ionises to A-
  4. At midpoint pH = pKa, beyond this HA continues to be used up until all of it is ionised to A-
42
Q

What happens to the pH during the buffering region?

A

pH barely changes with a large input of an acid or base

43
Q

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

A
44
Q

What are important buffers in the body?

A

Phosphate

Bicarbonate

45
Q

Why are buffers important in the body?

A

They maintian physiological pH when acids and bases are added

Science for Medicine (55 decks)

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