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Nutrition 1 (Semester I) > 3b. Biochemistry - Carbs & Lipids > Flashcards

3b. Biochemistry - Carbs & Lipids Flashcards

1
Q

What is biochemistry?

A

Science concerned with the chemical and physiochemical processes and substances that occur within living organisms

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2
Q

Which elements are carbohydrates made from?

A

C-H-O

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3
Q

How are the carbon atoms usually arranged?

A

In a ring with O2 and H attached

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4
Q

Why do carbohydrates have many -OH groups?

A

So they can form hydrogen bonds

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5
Q

What is the benefit of carbohydrates having many -OH groups?

A

Smaller carbs such as simple sugars can dissolve easily in water

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6
Q

What are the three classes of carbs?

A

Monosaccharides
Disaccharides
Polysaccharides

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7
Q

How are monosaccharides constructed?

A

With 3-7 C atoms

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8
Q

Examples of monosaccharides

A 
Glucose
Fructose
Galactose
Deoxyribose
Ribose
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9
Q

How are disaccharides constructed?

A

2 monosaccharides joined together by dehydration reaction

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10
Q

Examples of disaccharides

A

Sucrose
Lactose
Maltose

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11
Q

Which two monosaccharides make up sucrose?

A

Glucose

Fructose

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12
Q

Which two monosaccharides make up lactose?

A

Glucose

Galactose

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13
Q

Which two monosaccharides make up maltose?

A

Glucose

Glucose

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14
Q

How are polysaccharides structured?

A

10s-100s of monosaccharides joined together by dehydration reaction
Long chains of glucose

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15
Q

Examples of polysaccharides

A

Glycogen
Starch
Cellulose

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16
Q

What characteristic do most monosaccharides have?

A

Sweet taste

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17
Q

Which monosaccharide is the sweetest?

A

Fructose

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18
Q

How are monosaccharides grouped?

A

Into families named after the number of carbon atoms

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19
Q

What are the names of the monosaccharide groups?

A

Triose (3 carbons)
Pentose (5 carbons)
Hexose (6 carbons)
Heptose (7 carbons)

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20
Q

What are isomers?

A

They have the same chemical formula but different structures

same number of Lego bricks used to make different structures

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21
Q

Examples of isomers

A

Glucose
Galactose
Fructose

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22
Q

What is the name of the bond that joins two monosaccharides together to form a disaccharide?

A

Glycosidic bond

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23
Q

How is a glycosidic bond created?

A

Through dehydration synthesis

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24
Q

How is a disaccharide broken down?

A

Water is put back in during digestion

Known as hydrolysis

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25
Q

When is maltose formed?

A

During the hydrolysis of starch

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26
Q

What percentage of cow’s milk is lactose?

A

5%

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27
Q

What percentage of human milk is lactose?

A

7%

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28
Q

Why are polysaccharides normally insoluble in water?

A

They have given up so many -OH groups

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29
Q

Do polysaccharides taste sweet?

A

No

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30
Q

Where does the digestion of polysaccharides begin?

A

In the oral cavity

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31
Q

What is the most common type of polysaccharide in the body?

A

Glycogen

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32
Q

What is each glycogen molecule made up of?

A

Around 60,000 glucose molecules

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33
Q

What is the function of glycogen?

A

Short-term energy

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34
Q

Where is most glycogen made?

A

Liver

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35
Q

Where is most glycogen stored?

A

Liver

Muscles

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36
Q

What can glycogen in the liver be used for?

A

Maintain blood sugar levels

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37
Q

What can glycogen stored in the muscles be used for?

A

Energy for that particular muscle

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38
Q

What is cellulose?

A

Structural material of plants

Found in plant cell walls

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39
Q

How is cellulose constructed?

A

Flat, ribbon-like strands

Joined together with bonds

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40
Q

Why can’t we digest cellulose?

A

We don’t have the correct enzymes to break down the bonds

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41
Q

What is the function of cellulose?

A

Fibre to assist with the movement of materials through the intestine

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42
Q

Which polysaccharide is the main dietary source?

A

Starch

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43
Q

Which foods can starch be found in?

A

Bread
Rice
Pasta

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44
Q

Where does digestion of starch begin?

A

In the oral cavity

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45
Q

What is starch made up of?

A

20-25% amylose

75-80% amylopectin

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46
Q

How is amylose constructed?

A

Single chain of glucose units

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47
Q

How does the structure of amylose affect its digestion?

A

Straight chain which limits amount of surface area exposed for digestion

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48
Q

What is amylose also known as?

A

Resistant starch

as it is digested more slowly

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49
Q

What can some resistant starch end up doing in the large intestine?

A

Feeding the bacteria there

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50
Q

How is amylopectin constructed?

A

Glucose chains but with branches

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51
Q

How does the structure of amylopectin affect its digestion?

A

More surface area available for digestion

Broken down quickly

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52
Q

What affect does the digestion of amylopectin have in the body?

A

Broken down quickly
= rise in blood sugar levels
= rise in insulin

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53
Q

What are the functions of carbs?

A

Primary fuel for energy production
Also limited amount of energy stored
Fibre

54
Q

What are the therapeutic uses of carbs as fibre?

A 
Bowel function
Protect against colorectal cancer
Protect against CVD
Protect against diabetes
Increase satiety
55
Q

Which processes are carbs used for?

A

ATP production
Glycogen synthesis
Triglyceride synthesis
Amino acid synthesis

56
Q

How are carbs digested?

A

Oral cavity - salivary amylase starts to break down the ends of the long glucose chains
Small intestine - pancreatic amylase (from pancreas) breaks down polysaccharides into disaccharides
Brush border enzymes break them down further - lactase, maltase, sucrase

57
Q

Which elements are lipids made from?

A

C-H-O

but in a different ratio to carbs

58
Q

How are lipids different in structure to carbs?

A

Have fewer -OH groups

59
Q

What does having fewer -OH groups mean for lipids?

A

They are hydrophobic

60
Q

How do lipids move around the body?

A

Often bond to a protein to make them more soluble

61
Q

What are lipids bonded to proteins called?

A

Lipoproteins

62
Q

What is the main form of dietary fat?

A

Triglycerides

63
Q

How are triglycerides constructed?

A

A single glycerol molecule

3 fatty acid chains

64
Q

How are the fatty acids attached to the glycerol?

A

By dehydration synthesis and the ester bond

65
Q

How are triglycerides broken down?

A

By hydrolysis

like carbs

66
Q

What are the functions of triglycerides?

A

Protection of body parts/organs
Insulation
Energy
Storing excess calorific intake

67
Q

How are saturated fats constructed?

A

Single covalent bonds between each of the fatty acid carbon atoms
Each carbon atom is saturated with hydrogen atoms

68
Q

How do saturated fatty acid chains appear?

A

Very straight

69
Q

What quality does the very straight fatty acid chain give to saturated fats?

A

More likely to be solid at room temperature

70
Q

Example of a saturated fat

A

Coconut oil

71
Q

How are monounsaturated fats constructed?

A

Mainly single covalent bonds between each of the fatty acid carbon atoms but with one double covalent bond between two carbons

72
Q

How do monounsaturated fatty acid chains appear?

A 
Slight bent
(due to the double bond)
73
Q

What quality does a monounsaturated fat have?

A

Generally liquid at room temperature because the molecules aren’t as packed together

74
Q

Example of a monounsaturated fat

A

Olive oil

75
Q

How are polyunsaturated fats constructed?

A

Contain more than one double covalent bond in the carbon chain

76
Q

How do polyunsaturated fatty acid chains appear?

A

Kinked

77
Q

What quality does a polyunsaturated fat have?

A

Liquid at room temperature

78
Q

Examples of polyunsaturated fats

A

Sunflower oil
Rapeseed oil
Vegetable oils

79
Q

How are fatty acids named?

A

According to the closest double bond to the end of the chain without O2

80
Q

How can you recognise omega 3 from a diagram?

A

The double bond is 3 carbons up from the end

81
Q

How can you recognise omega 6 from a diagram?

A

The double bond is 6 carbons up from the end

82
Q

What two configurations are possible within unsaturated fats?

A

Cis

Trans

83
Q

What is a cis configuration?

A

When the H atoms are on the same side of the double bond

84
Q

What is a trans configuration?

A

When the H atoms are on separate sides of the double bond

85
Q

Which H atom configuration is more prevalent in nature?

A

Cis

86
Q

How does a cis fatty acid appear?

A

Bent

87
Q

How does a trans fatty acid appear?

A

In a line

88
Q

What can fatty acids do to cell membranes?

A

Cis - makes the membrane more flexible

Trans - makes the membrane stiffen

89
Q

What, physiologically, can stiff cell membranes lead to?

A

Oxidative damage

Leaky cell membranes

90
Q

How can cis fats be turned into trans fats?

A

By heating them to high temperatures

Through hydrogenation reactions used to make processed foods and margarine (trans fat)

91
Q

What are essential fatty acids (EFAs)?

A

Polyunsaturated fatty acids that can’t be constructed within the body
Need to be obtained from the diet

92
Q

What are the families of EFAs?

A

Omega 3

Omega 6

93
Q

Why is omega 3 important to get from the diet?

A

The body can’t make it from scratch

94
Q

What are the types of omega 3s?

A

ALA (alpha-linolenic acid)
EPA (eicosapentaenoic acid)
DHA (docosahexaenoic acid)

95
Q

What are the types of omega 6s?

A

LA (linolenic acid)
GLA (gamma linolenic acid)
AA (arachidonic acid)

96
Q

Sources of omega 3 - ALA

A

Flaxseeds
Walnuts
Green leafy veg

97
Q

Sources of omega 3 - EPA + DHA

A

Oily fish

98
Q

Sources of omega 6 - LA

A

Veg oils
Nuts
Seeds

99
Q

Sources of omega 6 - GLA

A

Borage oil

Evening primrose oil

100
Q

Sources of omega 6 - AA

A

Meat
Dairy
Eggs

101
Q

Should omega 6s be avoided?

A

No

For healthy cells and healthy cell to cell communication, a diet would ideally contain a variety of both omega 3 and 6

102
Q

Which EFA is the Western diet rich in?

A

Omega 6

particularly AA

103
Q

Why should we consume less omega 6?

A

It’s pro-inflammatory

104
Q

In which order are omega 3s converted?

A

ALA - EPA - DHA

105
Q

In which order are omega 6s converted?

A

LA - GLA - AA

106
Q

What is needed to make the conversion of one EFA to another?

A

Desaturase enzymes to add in double bonds

107
Q

What is the conversion rate for omega 3s and 6s?

A

10%

in favour of the EFA in abundance - usually 6

108
Q

Functions of EFAs

A 
Fluidity and structure of cell membranes
Synthesis of prostaglandins
Joint lubrication
Transporting cholesterol
Haemoglobin formation
109
Q

Why are polyunsaturated fats/EFAs prone to becoming free radicals?

A

Electrons are lost during heating

New free radical further reacts with O2 in the air over the cooking pan which makes it even more damaging

110
Q

Where are damaged fats incorporated?

A

Into cell membranes

111
Q

How is oxidation of fatty acids accelerated?

A

Heat
Oxygen
Light

112
Q

How are polyunsaturated fats best kept?

A

In dark glass bottles in fridge

Never heat up

113
Q

Which fat is best for cooking with at higher temperatures?

A

Saturated e.g. coconut oil

114
Q

Which is best for cooking with - OO or EVOO?

A

EVOO

115
Q

What do lipoproteins contain?

A

Triglycerides

Cholesterol

116
Q

Where are lipoproteins synthesised?

A

Liver

117
Q

What are the types of lipoproteins?

A

VLDL - very low density lipoproteins
LDL - low density lipoproteins
HDL - high density lipoproteins

118
Q

What are VLDL?

A

Carry newly synthesised triglycerides (those converted from excess carbs) from the liver to adipose tissue

119
Q

What are high VLDL a sign of?

A

Over-eating

120
Q

What are LDL?

A

Carry cholesterol from the liver to cells of the body

121
Q

Why do we need LDL?

A

Repair cells
Support cell membranes
Synthesise sex and adrenal hormones

122
Q

What are HDL?

A

Collect cholesterol from body cells back to the liver

123
Q

How are phospholipids structured?

A

Glycerol head

2 fatty acid chains

124
Q

What are the qualities of the phosphate head of a phospholipid?

A

Lots of -OH molecules
Hydrophilic
Polar
Water soluble

125
Q

What are the qualities of the fatty acid tails of a phospholipid?

A

Hydrophobic
Non-polar
Fat soluble

126
Q

What do the fatty acid tails of the phospholipid contain?

A

Saturated fat
Unsaturated fat
(to support healthy cell membrane that’s not too rigid or fluid)

127
Q

What are steroids?

A

Lipids formed from cholesterol

128
Q

How do steroids appear?

A

4 rings of carbon atoms joined together at their base

129
Q

What are sterols?

A

Steroid bases that contain a -OH group

130
Q

What are steroids used for?

A

Create hormones

131
Q

What is meant by amphiphatic?

A

Phospholipids are soluble on one side and insoluble on the other

Nutrition 1 (Semester I) (15 decks)

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