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z - A Level Biology > 2.1.2: Biological molecules > Flashcards

2.1.2: Biological molecules Flashcards

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1
Q

Catabolic reaction

A

Large molecule broken down to smaller molecules e.g. hydrolysis
⟶ Energy given out (to surroundings)

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2
Q

Anabolic reaction

A

Smaller molecules built up to large molecule e.g. condensation reaction
⟶ Energy taken in (required)

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3
Q

Features of a hydrolysis reaction

A
  • “Splitting with water”
  • Catabolic
  • Covalent bond broken
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4
Q

Features of a condensation reaction

A
  • Water molecule produced
  • Anabolic
  • New covalent bond formed
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5
Q

Hydrogen bonding occurs when…

A
  • Slightly negatively charged part of molecule contacts & attracts slightly positively charged part of molecule.
  • Between H and O.
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6
Q

Individual hydrogen bonds are ____

A

weak but due to large numbers their effect can be big.

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7
Q

Effect of H-bonding on polymers

A

Strengthens and stabilises polymers.

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8
Q

Properties of water

A
  • High SHC
  • High latent heat of vaporisation
  • Cohesion
  • Surface tension
  • Polar so can form H-bonds
  • Expands when freezes
  • Can act as solvent
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9
Q

Water’s high SHC

A

• Due to H-bonding, water molecules stick to one another
• Hard to separate molecules
• Higher boiling point than expected
• High SHC
⟶ Acts as a buffer to sudden temp. changes, keeps an environment stable

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10
Q

Water’s high latent heat of vaporisation

A

• Due to H-bonding, water molecules stick to one another
• Lots of energy needed to evaporate 1 gram of water
⟶ Sweating = effective cooling mechanism in mammals

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11
Q

Cohesion in water

A

Cohesion: tendency of water molecules to stick to each other

⟶ Allows water to be pulled up tube (xylem)

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12
Q

Surface tension in water

A

Body of water moves as one mass
• Water molecules at the edge of a body of water are pulled back in rather than escaping
⟶ Allows pond skater to skate across pond

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13
Q

Water’s density when freezing

A

• Water becomes less dense when it freezes

⟶ Ice floats, insulating water beneath and allowing organisms to survive

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14
Q

Water as a solvent

A

• Polar, interacts with other polar molecules
• Interaction of +ve and -ve charges keeps solute molecules apart hence it dissolves
⟶ Molecules in solution can move/react with other molecules –> water = basis for metabolic reactions

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15
Q

Functions of carbohydrates

A
  • Energy source
  • Energy store
  • Structure (cellulose in wall)
  • Parts of larger molecules (nucleic acids)
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16
Q

Generalised formula of a monosaccharide

A

C𝒏(H₂O)𝒏

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17
Q

Types of simple sugars

A
  • Triose
  • Pentose
  • Hexose

Prefix = no. of carbons

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18
Q

Arrangements of glucose

A
  • Chain

* Ring

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19
Q

Forms of glucose ring

A

Alpha

Beta

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20
Q

Alpha glucose

A

H above OH on C1

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21
Q

Beta glucose

A

OH above H on C1

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22
Q

Glycogen contains _ glucose

A

𝛂

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23
Q

Cellulose contains _ glucose

A

β

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24
Q

Glycosidic bond

A

Covalent bond between two monosaccharides

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25
Q

Sucrose

A

Glucose + fructose

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26
Q

Lactose

A

Glucose + galactose

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27
Q

Maltose

A

Glucose + glucose (both 𝛂)

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28
Q

Elements that make up carbohydrates

A

C
H
O

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29
Q

Elements that make up lipids

A

C
H
O

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30
Q

Elements that make up proteins

A 
C
H
O
N
S
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31
Q

Elements that make up nucleic acids

A 
C
H
O
N
P
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32
Q

Example of a pentose monosaccharide

A

Ribose

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33
Q

Carbohydrate polymers are stores of

A

potential energy

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34
Q

Large polysaccharides are ______ so do not affect ______

A

Large poysaccharides are insoluble so do not affect osmosis

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35
Q

Where is the glycosidic bond in amylose

A

1,4 glycosidic bond

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36
Q

Amylose arranged in coil so

A

very compact

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37
Q

Glycogen arrangement

A
  • Branched (v. compact)

* Can be hydrolysed quickly

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38
Q

Where are the glycosidic bonds in glycogen?

A
  • 1,4 glycosidic bond

* 1,6 linkage (forms branches)

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39
Q

Why is glycogen good for storage?

A
  • Insoluble
  • Very compact
  • Large enough = doesn’t diffuse out easily
  • Branches at 1,4; linkage at 1,6 –> lots of potential enzyme attachment, hydrolysis sites
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40
Q

Why high conc. glycogen = good athletic performance

A
  • Glucose stored as glycogen
  • Glucose used for respiration to produce ATP
  • ATP needed for muscle contraction etc.
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41
Q

Conjugated proteins contain…

A

a prosthetic group

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42
Q

Globular proteins

A
  • spherical, water soluble proteins
  • hydrophilic outside, hydrophobic core
  • Have chemical functions in living organisms, e.g. enzymes, hormones
43
Q

Fibrous proteins

A
  • Long, insoluble structural proteins
  • Lots of hydrophobic R groups
  • Examples: keratin, elastin, collagen
44
Q

Collagen

A
  • 3 polypeptide chains twisted around each other
  • 35% glycene
  • Make up tendons, cartilage, artery walls
45
Q

Elastin

A
  • Many soluble tropoelastin molecules linked to form one stable, cross-linked structure
  • Interactions between hydrophobic regions, crosslinks = covalent bonds –> gives strength and elasticity to skin, tissues
46
Q

Primary structure

A

the sequence of amino acids in a protein

47
Q

Basic chain

A

the order of the amino acids

48
Q

Secondary structure

A

the initial folding of the primary structure

49
Q

Secondary structure types

A
  • Alpha helix

* Beta pleated sheet

50
Q

Alpha helix structure

A

Hydrogen bonds form
between H-N….C=O
every 4 amino acids

51
Q

Beta pleated sheet structure

A

Hydrogen bonds form
between H-N…C=O
but not at regular intervals

52
Q

Tertiary structure

A

provides a protein’s 3D shape.

53
Q

Hydrophobic interaction in a protein

A

interaction pushing apart parts of molcule

54
Q

Ionic bonds in a protein

A

polar interactions between R groups, help maintain shape, stronger than H-bonds

55
Q

Disulfide bridges

A

very strong covalent bonds, offer further suppport.

2 R groups with sulphur required

56
Q

Cellulose structure

A
  • Contains β glucose
  • 1,4 glycosidic bond
  • Alternate β glucose molecules rotated 180°
  • Hydroxyl groups projected either side of chain –> allows H-bonding to occur between chains
57
Q

Where do plant cell walls get their strength

A
  • From cellulose microfibrils –> bundles of 60-70 cellulose molecules lie parallel
  • H bonding between hydroxyl groups of neighbouring chains
58
Q

Fat

A

lipid that is solid at RTP

59
Q

Oil

A

lipid that is liquid at RTP

60
Q

Lipis are __________ so _________

A

Lipids are non-polar so insoluble

61
Q

Triglyceride

A

Contains glycerol and 3 fatty acids

62
Q

Glycerol

A

3 carbon molecule with 3 OH groups

63
Q

Saturated

A

all available bonds in the hydrocarbon chain have a hydrogen attached.

64
Q

Unsaturated

A

not all available bonds in the hydrocarbon chain have a hydrogen attached

65
Q

Where are saturated triglycerides found?

A

In animal products

66
Q

Where are monounsaturated triglycerides found?

A

in cell membranes

67
Q

Where are polyunsaturated triglycerides found?

A

in vegetable oil e.g. olive oil

68
Q

How is a triglyceride formed?

A
  • Condensation reaction repeated 3 times
  • 3 water molecules produced
  • 3 ester bonds formed
69
Q

Why are triglycerides good energy stores?

A
  • Insoluble: hydrophobic charges all around molecule, cannot H bond with water, does not affect ψ
  • High calorific value: gives out 2x as much energy as the same mass of carbohydrates would
70
Q

Differences between triglycerides and phospholipids

A
  • Phospholipids contain a phosphate group
  • Triglycerides contain 3 fatty acids, phospholipids contain 2
  • Triglycerides are totally hydrophobic, phospholipids have a hydrophilic head and hydrophobic tail
71
Q

How are lipids respired?

A
  • Can be respired directly
  • Hydrolysis of ester bond required
  • Glycerol and fatty acids completely broken down into carbon dioxide and water
  • Releases energy used to make ATP
72
Q

Cholesterol

A
  • Small, made from 4 carbon-based rings
  • Narrow and hydrophobic
  • Found in membranes, between tails of phospholipids
  • Helps regulate strength and fluidity of membrane
73
Q

Steroid hormones

A
  • Made from cholesterol

* Lipid based, can pass through phospholipid bilayer into target cell

74
Q

Cholesterol is needed for

A

Plasma membrane

Hormones

75
Q

Cholesterol is made in

A

many cells especially those in the liver

76
Q

In excess, cholesterol

A

can cause formation of gall stones, build up in arteries and lead to stroke, heart attack

77
Q

Where is starch found?

A

In chlorolplasts and plant storage organs

78
Q

What is starch made from?

A

2 polysaccharides:
• Amylose (20%)
• Amylopectin (80%)

79
Q

Starch is soluble/insoluble?

A

Insoluble, so does not affect ψ.

80
Q

Starch and glucose - shared features

A

✔︎ Energy storage molecules
✔︎ Insoluble –> do not affect ψ
✔︎ Long chains (of glucose); can be hydrolysed for respiration to produce ATP

81
Q

Ca²⁺ uses

A
  • Nerve impulse transmission

* Muscle contraction

82
Q

Na⁺ uses

A
  • Nerve impulse transmission

* Kidney function

83
Q

K⁺ uses

A
  • Nerve impulse transmission

* Stomatal opening

84
Q

H⁺ uses

A
  • Catalysis of reactions

* pH determination

85
Q

NH₄⁺ uses

A

• Production of nitrate ions by bacteria

86
Q

NO₃⁻ uses

A

• Nitrogen supply to plants, for amino acid and protein formation

87
Q

HCO₃⁻ uses

A

Maintenance of blood pH

88
Q

Cl⁻ uses

A

• Balance positive charge of sodium and potassium ions in cells

89
Q

OH⁻ uses

A
  • Catalysis of reactions

* pH determination

90
Q

Benedict’s test method - reducing sugars

A

1) Add sample to test tube. If solid, grind up into water.
2) Add benedict’s reagent.
3) Heat mixture gently in water bath set to 80°C for 5 mins.

91
Q

Benedict’s test method - non-reducing sugars

A

1) Add dilute hydrochloric acid to sample in test tube.
2) Heat for a few minutes to hydrolyse the glycosidic bond.
3) Add sodium hydrogencarbonate powder to neutralise the solution. The solution should fizz.
4) Add Benedict’s reagent.
5) Heat mixture gently in water bath set to 80°C for 5 minutes.

92
Q

Benedict’s test results

A 
✘ Blue
✔︎ Green - v. low
✔︎ Yellow - low
✔︎ Brown - medium
✔︎ Brick-red/orange - high
93
Q

Emulsion test - method

A

1) Add ethanol to test sample
2) Shake thoroughly so that any lipids in the sample are dissolved
3) Add water and shake gently

94
Q

Emulsion test - results

A

✘ Colourless and transparent

✔︎ Formation of cloudy white emulsion

95
Q

Emulsion test - safety

A
  • Ethanol is highly flammable

* Goggles should be worn when ethanol is handled

96
Q

Iodine Iodide test - method

A

1) Add a few drops of Iodine Iodide solution to the test sample

97
Q

Iodine Iodide test - results

A

✘ Yellow/brown

✔︎ Blue-black

98
Q

Biuret test - method

A

1) Sample in solution in test tube
2) Add an equal volume of sodium hydroxide at RTP
3) Add a few drops of dilute copper sulphate and mix gently

99
Q

Biuret test - results

A

✘ Blue (pale because dilute)

✔︎ Lilac/purple colouration

100
Q

Food test for starch

A

Iodine Iodide test

101
Q

Food test for proteins

A

Biuret test

102
Q

Food test for simple sugars

A

Benedict’s test

103
Q

Food test for lipids

A

Grease spot/emulsion

104
Q

Name of process in which triglycerides are formed

A

Esterification

z - A Level Biology (25 decks)

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