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Nutrition Semester 1 > BMS1060 - Biochemsitry WK1-2 > Flashcards

BMS1060 - Biochemsitry WK1-2 Flashcards

1
Q

All atoms of a particular element all have the same number of _______.

What are isotopes?

A

protons

isotopes = atoms of the same elemt but a different number of neutrons.

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2
Q

Atomic weight =

A

number of protons + number of neutrons

(rarely a whole number - average of different isotopes)

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3
Q

What is the difference between intermolecular and intermolecular bonds?

A

INTERmolecular - act between molecules
INTRAmolecular - act within a molecule

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4
Q

Give two properties of compounds with ionic bonding.

A

High m.p ad b.p and water soluble

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5
Q

Do covalent structures or ionic structures have a higher b.p and why?

A

Ionic structures: Stronger bonds

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6
Q

What is a dative bond?

A

A covalent bond between two atoms where one atom gives both of its electrons to the bond.

e.g. haem

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7
Q

What is electronegativity?

What do the values range from?

A

A measure of the tendency of an atom to attract a bonding pair of electrons.

0.7-4.0

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8
Q

Where in the periodic table are elements most electronegative and why?

A

As you go ALONG (–>) the period, more protons so greater positive charge - greater attraction of electrons.

As you go UP the group, less electron shielding so greater attraction of electrons.

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9
Q

What causes the bond in a molecule to be polar?

A

Differences between the atoms in electronegativity.

Electron distribution skewed towards the more electronegative element.

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10
Q

What are the 3 types of intermolecular bonds?

A

Van der Waals
Dipole-dipole interactions
Hydrogen bonding

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11
Q

Describe Van der Waals

A

Electrons move around by chance - uneven distribution of electrons.
This causes an instantaneous slight negative charge in one side of the atom.

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12
Q

Describe Dipole-Dipole interactions

A

Found in polar molecules - differences in electronegativity between atoms.
Electrons pulled more towards one atom, causing slight neg and sligh pos charges at either end of molecule/bond.

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13
Q

Describe hydrogen bonding.

Which bonds commonly have H-bonding?

A

Weak electrostatic attraction formed between polar molecules which occurs when an H atom binds to a lone pair of electrons on a highly electronegative atom.

O-H, F-H, N-H, Cl-H

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14
Q

1 mole of a subsance contains…

A

The same number of atoms as in 12g of pure carbon-12 (6.02x10^23)

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15
Q

What is the equation to work out the n.o of moles of a substance using mass and Mr?

A

n.o. of moles = mass (g) / formular weight

n = m / Mr

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16
Q

1L = ? dm^3

A

1L = 1 dm^3

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17
Q

What is the equation to work out the n.o of moles of a substance using concentration and volume?

A

n.o. of moles = concentration x volume

n = cv

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18
Q

What is Collision Theory?

A

The concept that reactant molecules must collide with sufficient energy and in the correct orientation to react.

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19
Q

What is Activation Energy?

What are the two types? Enthalpy change?

A

Ea = the energy needed to react two reactants together.

Exothermic - energy released - neg ΔH
Endothermic - energy consumed - pos ΔH

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20
Q

What happens in exothermic and endothermic reactions?

A

Endothermic - energy consumed when bonds are broken (+ΔH)

Exothermic - energy released when bonds are formed (-ΔH)

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21
Q

What do catalysts do?

A

Lower activation energy - so a greater proportion of molecules can react.

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22
Q

In terms of the Maxwell Boltzmann Distribution, what happens to the % of molecules that react when temperature increases and decreases?

A

Temp increase - % of molecules with sufficient energy to react increases.

Temp decrease - % of molecules with sufficient energy to react decreases.

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23
Q

What determines the rate of a reaction?
(Maxwell Boltzmann Distribution)

A

The number of molecules with activation energy.

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24
Q

When is a reaction ‘feasible’?

A

When it is ‘energetically favourable’ at a certain temperature.

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25
Q

How are endothermic reactions still feasible?

A

Because there’s an increase in entropy.

Disorder is thermodynamically favourable (creating order requires energy/effort).

26
Q

What is entropy?

A

A measure of disorder.

27
Q

What two things affect entropy?

A

State of substance (e.g. gases have greatest E)

Size of molecule (small molecules have higher E)

28
Q

What is Gibbs free energy?

A

The energy available in a substance to do work.

29
Q

What is the equation to work out Gibbs free energy?

A

G = H - TS

G = Enthalpy - (Temp x Entropy)

note: enthalpy and entropy affect whether a reaction is feasible or not

30
Q

In terms of Gibbs free energy, when is a reaction thermodynamically feasible?

A

Negative ΔG - EXOGERNIC - thermodynamically feasible

Positive ΔG - ENDERGONIC - not thermodynamically feasible

31
Q

When can some positive ΔG reactions be feasible?

A

When the reaction is couple up wth a negative ΔG reaction and the energy is shared across.

e.g.
(Cellular respiration - 2280kj mol^-1
ATP synthesis +30.5 kj mol^-1
Energy from respiration given to ATP synthesis reaction)

32
Q

What are the two words in chemistry to describe ‘water loving’ and ‘water hating’ molecules?

A

Hydrophilic (water-loving)
Hyrophobic (water-hating)

33
Q

What is hydrolysis and condensation?

A

Hydrolysis - water used to break down a compound

Condensation - a bond is formed and a water molecule produced

34
Q

What happens in the dissociation of water?

A

H2O <–> H+ + OH-

H+ released associates with another H2O to form H3O+ ion.

2 H2O <–> H3O+ + OH-

At R.T. around 1 in 1 billion molecules of water dissociates (rare, but happens)

35
Q

What is an acid?

What is the difference between a strong and weak acid?

A

A substance that donates H+

Strong acids compeltel dissociate in water
(HCl + H2O –> H3O+ + Cl-)
Weak acids partially dissociate in water
(CH3COOH + H2O <–> CH3COO- + H3O+)

36
Q

What is a base?

What is the difference between a strong and weak base?

A

Bases either:
- directly produce OH- ions by dissociation
OR
- pull H+ awau from H2 to form OH-

Strong - completly dissociates in water
(KOH –> K+ + OH-)
Weak - partially dissociates in water
(NH3 + H2O <–> NH4+ + OH-)

37
Q

What is the equation for pH?

What is the scale?

A

pH = -log10[H+]

1M to 1x10^-14M (0-14 on pH scale)
M = molar conc (in this case of H+ in a solution)

38
Q

What pH does blood plasma have?

What happens to patients when their blood has a lower pH? When does this usually happen?

A

Around 7.4

Patients can have acidosis
In diabetic patients - fatty acids get broken down at a higher rate, or when fasting/heavy exercise.

39
Q

What do buffers do? What do they consist of?

A

They keep the pH constant by resisting changes with the addition of H+ or OH-.

Consist of (almost) equal concs of conjugate bases and acids.

40
Q

What is the buffering region?

A

Where the buffer works most efectively.

In buffering region, the pH is maintained around the pKa.

41
Q

What is pKa?

A

The pH where concs of acid and its conjugate bases are the same (in buffers)

42
Q

What are two physiological buffer systems?

A

Carbonic acid and Dihydrogen Phosphate

43
Q

What is the structure of an amino acid?

A

C - Chiral carbon -> superimposable
R - there are 20 different R groups that naturally occur in proteins

44
Q

Almost all amino acids are ___steroismers

A

L (literally makes an L shape)

45
Q

Describe the formation of a peptide bond (image):

A
46
Q

What are the 5 classifications of amino acids by R groups?

A

R-groups:

1) Non-polar (–CH3)
2) Polar (–CH2OH)
3) Aromatic (contain rings)
4) Positively charged (–CH2NH3+)
5) Negatively charged (–CH2COO-)

47
Q

What does cystine have that allows it to form disulphide cross-links with other cystine molecules?

A

S-H group (polar R group)

48
Q

What causes the charge of an amino acid to change?

A

Changes in pH

49
Q

What is the isoelctric point?

A

The pH where the net charge on the molecule is neutral (+ and - balanced)

50
Q

What is 1 Dalton (1Da) equal to?

A

1 amino acid (1 amn)

51
Q

Carbohydrates: what are their general formula?

What type of of steroisomers do they usually form?

What forms do they exist in?

A

Cn(H2O)n

D-steroisomers

Linear and Cyclic forms - in solution there is equalibrium between linear and cyclic forms.

52
Q

Here we have alpha and beta D-glucose. What is the overarching term for these molecules?

A

Anomers

‘OH look - Ants on the ground, Birds in the air!’

53
Q

What are the common disaccharides of glucose and their monomers?

A

Maltose - 2xD Glucose
Lactorse - D Glucose + D Galactose
Sucrose - D Glucose + D Fructose

54
Q

What are the common polysaccharides of glucose and their monomers?

A

Starch (amylose or amylopectin) - alpha-d glucose
Glycogen - branched - alpha-glucose
Cellulose - Beta-glucose

55
Q

Describe the structure of fatty acids - saturated and unsaturated: (image)

A
56
Q

Name 4 types of lipids

A
  • Triglycerides
  • Phopholipids
  • Glycolipids
  • Sterols
57
Q

Describe Triglycerides

A

3 fatty acids linked to glycerol

Most common way fats circulate as in the blood and stored in the body.

Can be burned for energy or used for insulation.

58
Q

Describe Phospholipids

A

Hydrophilic head and 2 hydrophobic fatty acid tails.

Make up membranes and envelopes (double membranes).

59
Q

Describe Glycolipids

A

Lipid covalently bonded to an oligosaccharide.

Parts of plant and animal cell membranes.

Particular glycolipids determine blood groups.

60
Q

Describe Sterols

A

Lipids found in membranes.

Series of hydrocarbon rings -> makes structure ‘stiffer’

Includes cholesterol and steroid hormones.

Nutrition Semester 1 (10 decks)

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