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3/4 Chemistry. > Food Chemistry+ proteins/enzymes > Flashcards

Food Chemistry+ proteins/enzymes Flashcards

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1
Q

aerobic respiration

A

requires oxygen and is the main source of energy for the human body

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2
Q

anaerobic respiration

A

does not require oxygen and yields less energy

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3
Q

energy content units

A

kJ/g kJ/mol or kJ/g (100g)

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4
Q

features of simple calorimetry

A

-measures change in temp of water in calorimeter pot and is used to determine energy of food being combusted
-major limitation is that heat is lost to the environment

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5
Q

where does the reaction take place in a bomb calorimeter

A

a sealed ‘bomb’ vessel

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6
Q

where does the reaction take place in solution calorimeters

A

in a solution

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7
Q

features of bomb calorimeter

A

-measures heat of combustion of GASEOUS products
-occurs in reaction chamber that withstands high pressure and temp whilst maintaining volume
-chamber is wired to a electrical circuit to ignite (start combustion)
-reaction chamber surround by a vessel of water so heat energy transferred can be measured
-insulation around reaction vessel ensures even distribution of heat in water
-kj/g

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8
Q

features of solution calorimeter

A

-can occur in a polystyrene cup (constant pressure)
-insulated container holds a known volume of water in which a reaction in solution occurs
-increase or decrease in temperature of surrounding water determines if the reaction is endothermic or exothermic

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9
Q

limitations of solution calorimeter

A

-polystyrene cup absorbs some energy and hence the delta T value is slightly lower than real value
-solution calorimeters can not measure energy content of food as they can’t be combusted in aqueous state

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10
Q

what do bomb calorimeters measure

A

heat content of fuels and food

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11
Q

what do solution calorimeters measure

A

heat of solution, neutralisation

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12
Q

what type of reactions occur in the two different calorimeters

A

only EXOTHERMIC in bomb whereas there are exo and endothermic reactions in solution calorimeters

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13
Q

define calorimetry

A

method by which chemists measure the heat released or absorbed by a chemical reaction, such as combustion

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14
Q

Random errors with calorimeters

A

-not all food substance was combusted/ incomplete combustion –> lower energy content
-the temperature recorded was incorrect (delta T changes) –> increase or decrease in energy content depending on change

REPEAT TO COUNTER THESE RANDOM ERRORS

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15
Q

Systematic errors arising with calorimeters

A

-poorly insulated calorimeter
-incorrect calibration –> low CF means low energy content and vice versa
-incorrect calibration measurements eg voltage, time, amperes

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16
Q

Elements in carbohydrates

A

CHO

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17
Q

carbohydrate general formula

A

Cx(H2O)y

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18
Q

what type of reaction are carbohydrate monomers joined by

A

condensation (polymerisation)

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19
Q

what bond forms when carbohydrate monomer join

A

glycosidic bond /ether link

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20
Q

what groups do carbohydrate monomers join by

A

adjacent OH groups

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21
Q

general formula for disaccharides

A

C12H22O11

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22
Q

general characteristics of monosaccharides

A

sweet, crystalline and water soluble

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23
Q

what unique bond does glucose contain
-Fischer rep.

A

aldehyde

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24
Q

what unique bond does fructose contain

A

ketone

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25
Q

endothermic reaction involving glucose

A

carbon dioxide + water –> glucose + oxygen

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26
Q

exothermic reaction involving glucose

A

glucose + oxygen –> carbon dioxide + water

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27
Q

structural difference between glucose and galactose

A

The OH group and H varies of the 4th carbon in the ring

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28
Q

maltose made of

A

glucose and glucose

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29
Q

sucrose made of

A

glucose and fructose

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30
Q

lactose made of

A

glucose and galactose

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31
Q

How many water molecules are released in a condensation reaction

A

n-1

where n is the number of monomers

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32
Q

Starch is made of

A

amylose and amylopectin
(ALPHA GLUCOSE)

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33
Q

Glycogen is made of

A

alpha glucose

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34
Q

Cellulose is made of

A

beta glucose

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35
Q

what is starch function

A

energy storage component of plants

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36
Q

Describe the structure of amylopectin

A

-occasional crosslinks between glucose molecules (glycosidic link forms between C1 and C4 and also C1 and C6)
-chained molecules means less effective packing and lower attraction between OH groups
-Weaker H bonds

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37
Q

Describe structure of amylose

A

-linear molecule that packs tightly
-more attraction between OH groups
-stronger H bonds between glucose molecules

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38
Q

Overall glycogen structure

A

Highly branched

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39
Q

Overall structure of cellulose

A

large, tightly packed consistent linear structure

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40
Q

What is aspartame made of

A

aspartic acid, phenylalanine, methanol

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41
Q

what functional groups are in aspartame

A

carboxyl, amine, amide, ester and phenyl

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42
Q

How can aspartame be beneficial

A

-aspartame is approx. 180x sweeter than any common sugar
-far less artificial sweetener can be used to ‘sweeten’ foods which means overall energy decreases (b/c similar energy content) aids diets that need to be low in energy/ low calories

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43
Q

what does amylase break down

A

salivary amylase breaks down starch in body to maltose (disaccharide)

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44
Q

how’s maltose broken down

A

maltase breaks down maltose in small intestine

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45
Q

what happens to excess glucose that isn’t utilised after hydrolysis

A

undergoes condensation reaction to form glycogen

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45
Q

what happens to excess glucose that isn’t utilised after hydrolysis

A

undergoes condensation reaction to form glycogen (stored in liver and muscle cells)

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46
Q

Why is cellulose indigestible

A

-b/c humans lack the enzyme (cellulase) to break down/hydrolyse/digest cellulose
-then the rate at which its broken down is at too slow of a rate and passes through the body quickly
-therefore humans can’t gain any nutritional value from cellulose

NB-cellulose can still be beneficial, for example adding bulk to faeces decreasing risk of cancers and constipation/ aid digestion(dietary fibre)

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47
Q

Why does lactose intolerance occur

A

-individuals with lactose intolerance are unable to synthesise a sufficient amount of the enzyme (lactase) that breaks down lactose into glucose and galactose

-> bloating, diarrhoea, cramps

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48
Q

Define GI

A

glycemic index
a measure of how quickly glucose is released into the bloodstream/hydrolysed after consuming a carbohydrate when compared to 100 grams of pure glucose

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49
Q

name a few low GI foods

A

lentils, fruit, beans, porridge

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50
Q

name a few high GI foods

A

lollies, white bread, potatoes

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51
Q

Explain how amylopectin and amylose impact GI of foods

A

-b/c amylose has a linear structure and is able to pack closer together than amylopectin which has a branched structure, there is a difference in rate of hydrolysis
-then amylose is hydrolysed into glucose at at a slower rate than amylopectin and glucose enters the bloodstream at a slower rate than glucose from amylopectin

52
Q

Why are low GI foods beneficial for diabetics

A

release glucose slowly into bloodstream and help reduce the risk of blood sugar levels spiking and rising (decrease stress on beta cells to produce insulin)

53
Q

list sugars in increasing sweetness order

A

glucose , sucrose, fructose, aspartame

54
Q

what class of molecules are triglycerides

A

esters

55
Q

how are triglycerides formed

A

a condensation reaction between three fatty acids and a glycerol molecule

56
Q

what link forms when a triglyceride forms

A

ester link between each OH group in the glycerol and COOH group of the fatty acids

57
Q

how many waters are released when a triglyceride forms

A

3H2O

58
Q

Define a saturated fatty acid

A

a fatty acid with only single bonds present between carbons, for example most animal fats

59
Q

Are triglycerides polar molecules

A

no, they are relatively large non polar molecules

60
Q

Monounsaturated vs polyunsaturated fatty acids

A

Monounsaturated contains one carbon carbon double bond whereas polyunsaturated contains more than one carbon carbon double bond

61
Q

general formula of saturated fatty acids

A

Cn H2n+1 COOH

62
Q

general formula of monounsaturated fatty acids

A

Cn H2n-1 COOH

63
Q

general formula of polyunsaturated fats

A

Cn H2n-x COOH

where x is 2 times the number of double bonds minus 1

For example lipid w 7 C=C has formula CnH2n-13COOH

64
Q

is hydrolysis endo/exo thermic

A

exothermic (breakdown) +catabolic

65
Q

two ways fatty acids are metabolised

A

-used to produce energy (respiration)
-adipose storage

66
Q

What is needed and produced from hydrolysis of triglycerides

A

-enzyme and 3water needed
-glycerol and 3x fatty acids are produced

67
Q

Why are enzymes needed for hydrolysis of triglycerides

A

lowers the Ea to a sufficient/sustainable amount/ensures the rate of reaction is sufficient

68
Q

What is the difference between essential and non essential fatty acids

A

essential fatty acids can’t be synthesised by the body whereas fatty acids that the body can synthesis are referred to as non essential.

69
Q

two categories of fatty acids

A

omega-3 and omega-6 fatty acids

70
Q

How are omega-3 and omega-6 fatty acids distinguished

A

the 3 and 6 refer to the position of the first carbon carbon double bond from the omega end (opposite of the alpha/acid end)

71
Q

How are trans fats produced

A

-because trans fats are rarely found in nature
-they can undergo hydrogenation, where the fat becomes partially saturated by adding H across the double bond and most cis bonds that remain unsaturated are converted into trans double bonds

72
Q

3 ways triglycerides are broken down

A

oxidative (near double bond)
microbial (e.g interaction with bacteria in gut)
hydrolytic (in body-stomach/small intestine)

73
Q

define oxidative rancidity

A

when a triglyceride reacts with oxygen, the carbon carbon double bonds (or bonds near) in unsaturated fatty acids are broken to form single bonds with oxygen, producing highly volatile aldehydes and ketones resulting in unpleasant smells and flavours.

74
Q

suggest ways to reduce the effect/rate of rancidity

A

-store food in cool, dark places-fridge
-vacuum packaging food
-use dark containers
-fill containers to lid

75
Q

Describe how antioxidants work

A

-antioxidants donate a free electron from their OH group to free radicals this means that the antioxidant is preferentially oxidised, interrupting the propagation of free radicals and delaying/slowing the oxidation of the triglyceride

76
Q

what class of compound are antioxidants

A

often vitamins eg E,C

77
Q

2-amino acid is another name for

A

alpha amino acid

78
Q

what reactions do amino acids undergo to form dipeptides

A

condensation

79
Q

essential vs non essential amino acids

A

Essential amino acids can not be synthesised by the body (must be obtained through food) whereas non essential amino acids are produced in the body.

80
Q

identify 4 protein functions

A

enzymes, proteins, antibodies, skin/cartilage/muscles

81
Q

what determines the function of the protein

A

the R group

82
Q

what’s the backbone for an amino acid

A

NH2-CH(R)-COOH

83
Q

what is a zwitterion

A

they exist in neutral pH and contain an equal number of positive and negative regions so that they have no net charge

84
Q

other name for zwitterion

A

dipolar ion

85
Q

What does a zwitterion do in alkaline conditions

A

Because the anion is more abundant then it donates a proton from the COOH and hence forms a COO- region

DEPROTONATES

86
Q

what does a zwitterion do in acidic conditions

A

-Because the cation is more abundant then it accepts a proton (acts as a base), the NH2 group forms +NH3
PROTONATES

87
Q

what bond forms between amino acids joined

A

peptide bond forms between H from (NH2) and O from (C=OO) of different amino acids

88
Q

what are amino acid residues

A

amino acids that are present within the protein

89
Q

what does the dipeptide bond look like

A

C=O N-H (amide)

90
Q

what’s the N and C terminal

A

amino acid commencing at NH2 end is N-terminal and the amino acid that finishes at COOH end is the C-terminal

91
Q

Identify protein structures

A

primary, secondary, tertiary and quaternary

92
Q

Define primary structure

A

the sequence of amino acids in the polypeptide chain with strong covalent (peptide) bonds linking each amino acid at the amide link

93
Q

Describe bonds in primary structure

A

strong covalent bonds between C and N in the peptide links between amino acids

94
Q

Define secondary structure

A

primary structure that is folded into alpha helix, beta pleated sheets and random folding

95
Q

Whats alpha helix

A

H bonds that occur between non adjacent N-H groups and -C=O groups at different points along the chain

96
Q

types of secondary structure

A

alpha helix, beta pleated sheets, random folding

97
Q

Describe bonds in Secondary structure

A

H bonds form between the O from C=O and H on N-H of different/adjacent peptide chains (in the backbone) in alpha helix or beta pleated sheets

98
Q

Define tertiary structure

A

the overall 3-d shape that allows the protein to carry out its specific and complementary function which is driven by the R group

99
Q

Identify bonds in tertiary structure

A

H bonds , dispersion forces, ion dipole interaction, ionic interactions, disulphide bridges, dipole dipole bonds

100
Q

Define quaternary structure

A

arrangement of multiple (two or more) folded protein subunits

101
Q

What happens to proteins in body

A

-absorbed into bloodstream and transported to cells of body to make new protein
-left over amino acids are broken down in liver (deamination) where NH2 becomes ammonia.
-rest of protein is stored as a secondary energy source

102
Q

briefly describe how proteins are digested

A

-proteins broken down into polypeptides in stomach by proteases eg trypsin
-polypeptides broken down into dipeptides in pancreas
-dipeptides broken down into amino acids in the small intestine

103
Q

Whats needed for hydrolysis of proteins

A

water and enzymes

104
Q

what protein level is changed in hydrolysis

A

primary

105
Q

Describe the role of an enzyme

A

The enzyme and substrate are specific and complementary (fit together perfectly)
The enzyme and substrate form a bond, the active site of the enzyme weakens the bonds of the substrate, lowering Ea and providing an alternative reaction pathway. (enzyme unchanged)

106
Q

Difference between lock and key vs induced fit model

A

in the lock and key model the substrate and enzyme fit together perfectly whereas in the induced fit model the enzymes active site changes to accomodate and fit the substrate

107
Q

define enzyme activity

A

the amount of substrate converted to product per unit time

108
Q

define coenzyme

A

organic molecule that attaches to the active site of an enzyme and changes the surface shape (active site) to allow substrate to bind (functions as intermediate carriers of electrons and/or groups of atoms.)

109
Q

what protein structures are impacted by denaturation

A

2,3,4

110
Q

Why isn’t the primary structure impacted by denaturation

A

bonds that hold primary structure together (covalent bonds/peptide bonds) require too much heat energy to disrupt

111
Q

How does temperature denaturation affect enzymes

A

Increase temperature
Increases average kinetic energy
Molecules vibrate so rapidly that H bonds of the secondary structure, forces in tertiary structure and quaternary structure is disrupted
Active site has changed 3d shape and is no longer specific and complementary to substrate

112
Q

How does pH denaturation affect enzymes

A

Changes to the pH solution can change the charge of the basic or acidic components of the R/side groups on the amino acids of the proteins
This causes a change to the tertiary structure of the protein and the active site has changed/been disrupted and is no longer specific and complimentary, reducing enzyme activity

113
Q

do enzymes catalyse enantiomers

A

only one of them (the one that is s+c to)

114
Q

Do coenzymes stay the same structure after reacting

A

no

115
Q

How are vitamins classified

A

fat soluble vs water soluble

116
Q

What is the difference between fat and water soluble vitamins

A

Water soluble vitamins contain a higher proportion of OH groups and need to be regularly consumed (because they pass through blood) whereas fat soluble vitamins have long hydrocarbon chains and hence are stores in fats (don’t need to be regularly consumed-can be toxic)

117
Q

what is aspartame made of

A

methanol
phenylalanine and aspartic acid

118
Q

what are free radicals

A

atoms/group of atoms with an unpaired electron in its outer shell

119
Q

Features of emulsifying agents

A

-Polar regions to increase solubility for water component
-Non polar regions to attract fatty components

120
Q

how does increase solubility improve drugs effectiveness.

A

can travel in the bloodstream and bind at a better rate hence inhibiting the ___

121
Q

balanced equation for fermentation of glucose

A

1glucose –> 2ethanol + 2Carbon dioxide

122
Q

why is glycine a unique a- amino acid

A

-no chiral carbon centre
-not a optical isomer
-super imposable
-no R group

123
Q

Why is aspartame good for low GI

A

-does not hydrolyse into glucose
-does not impact BGL

124
Q

why pump oxygen into bomb calimoreter at a high pressure

A

excess oxygen ensures sufficient oxygen for complete combustion
high pressure=high ror
all = ENSURES REACTION GOES TO COMPLETION

125
Q

how does an amino acid change in low ph

A

low ph= acidic so amino acid functions as a base and protonates so the amino group gains a proton(H+) to form NH3 +

126
Q

how does amino acid change in high ph

A

high ph=alkaline so amino acid function as acid and deprotonates so the carboxyl group loses a proton(H+) to form COO-

127
Q
A

3/4 Chemistry. (10 decks)

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