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AS OCR Biology > Unit 2.2- Biological molecules > Flashcards

Unit 2.2- Biological molecules Flashcards

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1
Q

Why is water important for life?

A
  • Essential for photosynthesis
  • Transporting molecules
  • Maintaining shape
  • Regulating temperature
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2
Q

What types of bonds are in water molecules?

A

Covalent (share electrons, strong bond)

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3
Q

What are the charges in a water molecule?

A

Hydrogen atoms are delta positive and oxygen is delta negative.

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4
Q

What are hydrogen bonds?

A

The small bonds between molecules formed by the slight charges of each atom.

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5
Q

Why is water hard to heat up?

A

Hydrogen bonds keep the molecules together and it takes a lot of energy to over come these bonds so additional heat energy is then needed to heat up the water.

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6
Q

What is specific heat capacity?

A

The amount of heat energy required to increase the temperature of 1 Kg of a substance by 1K.

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7
Q

What is latent heat?

A

The heat energy needed for a substance to change state without changing temperature.

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8
Q

What is surface tension:

A

Water molecules stick together. Molecules on the surface can only stick to molecules below them. This forms a strong layer on which small animals can walk.

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9
Q

What are carbohydrates?

A

Organic compounds which comprise of only carbon, hydrogen and oxygen.

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10
Q

What are the three types of carbohydrates?

A
  • Monosaccharides
  • Disaccharides
  • Polysaccharides.
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11
Q

What are the properties of Monosaccharides?

A
  • Simplest sugars
  • Same number of carbon and oxygen
  • Have the general formula CnH2nOn
  • White crystalline solids
  • Dissolve in water to form sweet tasting solutions.
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12
Q

What are the two forms of glucose?

A

Alpha glucose and beta glucose.

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13
Q

What do alpha and beta glucose form?

A

Alpha forms starch and beta forms cellulose.

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14
Q

What is an isomer?

A

When two compounds have the same molecular formula but different structural formula.

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15
Q

How are disaccharides formed?

A

By two monosaccharides joining together.

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16
Q

What type of reaction is it when a disaccharide is made?

A

A condensation reaction.

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17
Q

What is a condensation reaction?

A

When water comes out of the reaction.

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18
Q

What is a glycosidic bond?

A

The bond formed when disaccharides are formed.

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19
Q

How do you turn disaccharides back into monosaccharides?

A

Add water.

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20
Q

What type of reaction is it when you turn disaccharides back into monosaccharides?

A

Hydrolysis reaction.

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21
Q

What are the properties of disaccharides?

A

-Dissolve in water and taste sweet

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22
Q

What do two glucose molecules join together to make?

A

Maltose.

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23
Q

What are some examples of disaccharides and the monosaccharides they come from?

A
  • Sucrose = glucose + fructose
  • Lactose = glucose + galactose
  • Maltose = glucose + glucose.
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24
Q

What are some examples of polysaccharides?

A
  • Starch
  • Cellulose
  • Glycogen.
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25
Q

What is the function of starch and glycogen?

A

They are stores of energy.

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26
Q

What is the function of cellulose?

A

It is a structural unit.

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27
Q

What is the structure of starch like?

A
  • Spiralling chains
  • Molecules are all the same way up
  • Amylose doesn’t branch
  • Amylopectin branches.
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28
Q

What is the structure of cellulose like?

A
  • Every second molecule is rotated by 180 degrees.
  • This is the beta 1-4 glycosidic bonds help to prevent the chain from spiralling
  • The hydroxyl group on carbon 2 sticks out, enabling hydrogen bonds to be formed between chains.
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29
Q

What is the structure of glycogen like?

A
  • Lots of branches so little tendency to coil
  • Compact
  • Easier to remove monomer units (than from starch), as there are more ends.
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30
Q

What breaks down glycogen?

A

Amylase breaks it down through hydrolysis into glucose when required for respiration.

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31
Q

What type of starch branches?

A

Amalopectin

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32
Q

What type of starch doesn’t branch?

A

Amylose

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33
Q

What type of food are polysaccharides?

A

Carbohydrates

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34
Q

What is starch made up of?

A

A mixture of amylose and amylopectin or just one of them.

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35
Q

What is the main form of carbohydrate used for energy storage in animals?

A

Glycogen

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36
Q

Where is glycogen stored?

A

The muscles and the liver

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37
Q

In times of high energy use, what happens to glycogen?

A

The organs hydrolyse the glycogen stored and break i down into glucose molecules which can be used in respiration.

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38
Q

What is glycogen soluble in?

A

Water

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39
Q

Why is glycogen’s compact shape beneficial?

A

It makes it optimal for energy storage.

40
Q

Microfibril definition:

A

Polymers of about 10,000 beta glucose molecules in a long unbranched chain.

41
Q

What do microfibrils make up?

A

Macrofibrils

42
Q

What group of lipids are fats and oils in?

A

Triglycerides

43
Q

What are the properties of fats?

A
  • Solid at room temperature
  • More saturated
  • C-C bonds
44
Q

What are the properties of oils?

A
  • Liquid at room temperature
  • More unsaturated
  • Some C=C bonds
45
Q

What are triglycerides made up of?

A

1 glycerol and 3 fatty acid chains

46
Q

What are triglycerides? (Not polymers)

A

Macromolecules

47
Q

What type of reaction are Triglycerides formed in?

A
  • Condensation reaction
  • Forms an ester bond between glycerol and each FA chain.
  • It is also known as esterification
48
Q

What are ester bonds broken down by?

A

Hydrolysis

49
Q

What type of bonds do unsaturated FAs contain?

A

1 or more C=C bond. It could bond to more H atoms.

50
Q

What type of bonds do saturated FAs contain?

A

No C=C bonds. Cannot bond to any more H atoms.

51
Q

What are the uses of lipids?

A
  • energy store
  • thermal insulator
  • buoyancy
  • protection of vital organs
52
Q

What is the structure of a phospholipid?

A

Hydrophillic head and 2 hydrophobic tails

53
Q

Why are unsaturated fatty acid tails in a phosopholipid bad?

A

It causes kinks and upsets the plasma membrane and causes it to be weaker.

54
Q

What do phospholipids make up?

A

The plasma membrane of cells

55
Q

What is the structure of phospholipids in a cell membrane?

A

They form a bilayer with the FA chains facing into each other because they are hydrophobic and the heads are hydrophillic. The polar heads dissolve in the aqueous intra and extracellular fluids.

56
Q

Why are phospholipids suitable for forming cell membranes?

A

They enable integration of other molecules into the ‘mosaic’ and help to regulate the movement of molecules in and out of the cell.

57
Q

What are the functions of proteins?

A

Growth and repair

58
Q

What are some examples of proteins?

A
  • Haemoglobin
  • Antibodies
  • Enzymes
  • Hormones
  • Signal receptors
  • Collagen
59
Q

What are essential amino acids?

A

Amino acids that ca’t be synthesised by the human body. We must get them from food.

60
Q

Polypeptide chain definition:

A

A short chain of amino acids.

61
Q

What is the structure of an amino acid?

A

H H O (double bond)
N C C
H R OH

62
Q

What is the basic amino group of an amino acid?

A

NH2. On the left hand side.

63
Q

What is the carboxyl (acidic) group of an amino acid?

A

COOH. On the right hand side.

64
Q

What is the central group of an amino acid?

A

C-H. The middle and top.

65
Q

What is the R-Group on an amino acid?

A

An additional chain, covalently bonded- this is different for each amino acid.

66
Q

What type of reaction are two amino acids bound in?

A

Condensation.

67
Q

What type of bond is formed when two amino acids bond?

A

Dipeptide bond.

68
Q

What are the chemical elements in lipids?

A
  • Carbon
  • Hydrogen
  • Oxygen
69
Q

What are the chemical elements in nucleic acids?

A
  • Carbon
  • Hydrogen
  • Oxygen
  • Nitrogen
  • Phosphorus
70
Q

What type of monosacharide is glucose?

A

Hexose (contains 6 carbons)

71
Q

What type of monosacharide in ribose?

A

Pentose (contains 5 carbons)

72
Q

What is the difference in structure between alpha and beta glucose?

A

Alpha glucose is H on top of OH

Beta glucose is OH on top of H

73
Q

What structures are in the hydrophilic head of phospholipids?

A
  • Phosphate group

- Glycerol group

74
Q

What is the primary structure of an amino acid like?

A
  • Specific sequence of amino acids in a polypeptide

- unique to each gene

75
Q

What is the secondary structure of an amino acid like?

A
  • Polypeptide coils or folds in on itself because of the interactions of individual amino acids (hydrogen bonds)
  • This causes it to either form an alpha helix (strong) or a beta pleated sheet (weak)
76
Q

What is the tertiary structure of an amino acid like?

A
  • Alpha helix or beta pleated sheet folds in on itself
  • 3D shape which often improves solubility due to interactions between R groups and involves ionic, disulphide and hydrogen bonds and hydrophilic and hydrophobic interactions
77
Q

What is the quaternary structure of an amino acid like?

A

Interaction between two or more polypeptides, therefore only exists in proteins consisting of two or more polypeptides

78
Q

What is the structure of haemoglobin?

A
  • Quaternary structure
  • Globular
  • 4 polypeptide chains, 2 alpha, 2 beta
79
Q

What is the structure of collagen?

A
  • Quaternary structure

- Fibrous

80
Q

What are the properties of globular proteins?

A
  • Rolls up to form balls
  • Soluble in water because hydrophobic R groups turn inwards and hydrophilic R groups turn outwards
  • Usually have metabolic roles
  • e.g. haemoglobin, insulin, antibodies.
81
Q

What are the properties of fibrous proteins?

A
  • Form fibres. Regular, repetitive sequence of amino acids
  • Usually insoluble
  • Usually have structural roles
  • e.g. collagen, keratin.
82
Q

What is the prosthetic group of haemoglobin?

A

Haem group

83
Q

What is a conjugated protein?

A

A protein with an attached prosthetic group

84
Q

What are examples of cations?

A
  • Calcium ions (Ca2+)
  • Sodium ions (Na+)
  • Potassium ions (K+)
  • Hydrogen ions (H+)
  • Ammonium ions (NH4+)
85
Q

What are examples of anions?

A
  • Nitrate (NO3-)
  • Hydrogen carbonate (HCO3-)
  • Chloride (Cl-)
  • Phosphate (PO4-)
  • Hydroxide (OH-)
86
Q

How does the Biuret test work?

A
  • For proteins
  • Biuret reagent (copper sulphate (III)? and potassium hydroxide) is blue
  • The reagent turns purple in the presence of peptide bonds, indicating the presence of a protein.
87
Q

How does the Benedicts test work?

A
  • For reducing an non-reducing sugars
  • For reducing sugars:
  • Add Benedict’s reagent (Copper (II) suplhate in alkaline solution) to the sample
  • Heat ina water bath at 80K for 3 minutes
  • If there is reducing sugar, Cu2+ ions are reduced to Cu+ and the mixture is oxidisedand becomes brick red.
  • For non-reducing sugars:
  • Heat solution with acid to hydrolise any glycosidic bonds then neutralise solution with sodium hydroxide
  • Then do the same method as for reducing sugars
88
Q

How does the iodine test work?

A
  • Tests for starch
  • Uses potassium iodide as a source of iodine
  • If starch is present, the solution will turn a dark blue-black colour. This is because iodine becomes trapped in the coils of starch.
89
Q

How does the emulsion test work?

A
  • Tests for lipids
  • Shake sample with ethanol then pour solution into water
  • If the mixture turns cloudy then lipids are present
  • This is due to lipids’ insolubility in water
90
Q

Colorimetry definition:

A

The process to determine the concentration of glucose in a solution.

91
Q

How does coloimetry work?

A

Visible light goes through a filter and then through the solution then reaches a photocell. The opacity is an indicator of how much glucose has reacted, The a mount of light that goes through is recorded.

92
Q

What can be the stationary phase in thin-layer chromatography?

A
  • Cellulose chromatography paper

- Thin-layer chromatography plate

93
Q

What is in the mobile phase in thin-layer chromatography?

A
  • Solvent for molecules to be identified:
  • Water for polar molecules
  • Ethanol for non-polar molecules
94
Q

What is the formula for Rf value?

A

Distance travelled by each solute/ distance travelled by the solvent

95
Q

How are molecules identified through chromatography?

A

They each have their own Rf value

AS OCR Biology (12 decks)

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