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AS Biology > F212 Biological Molecules > Flashcards

F212 Biological Molecules Flashcards

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0
Q

Water

Polar Molecule

A

There is a slight positive charge (from the hydrogen nuclei) on the hydrogen atoms in a water molecule

There is a slight negative charge (from the electrons around the oxygen) on the oxygen atom in a water molecule

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1
Q

Water

Molecule

A

H2O

Each hydrogen atom shares its electron with the outer shell of the oxygen atom which stabilises the oxygen

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2
Q

Water

Intermolecular Hydrogen Bonds

A

Hydrogen bonds occur between the negatively charged oxygen atom of one molecule and the positively charged hydrogen atom of another molecule

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3
Q

Water

Liquid at Room Temperature

A

The intermolecular bonds between water molecules at room temperature hold the molecules together making water a liquid at room temperature rather than a gas
This allows water to act as a liquid transport medium in living things
E.g. blood in animals, the vascular system in plants

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4
Q

Water

Solvent

A

As water is a polar molecule it is a good solvent for other polar molecules and ionic compounds

When the attraction of the water is stronger than the intramolecular forces of the solute then the solute will be pulled apart e.g. ionic compound

In a polar molecule the charged parts of the water surround the charged parts of the solute separating the molecules and keeping them dissolved

Metabolic processes in all living organisms rely on chemicals being able to react in solution

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5
Q

Water

Thermal Stability

A

The hydrogen bonds between water mean that a relatively large amount of energy is required to increase the temperature

Large bodies of water provide fairly stable environments
Makes evaporation of sweat a very effective cooling mechanism

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6
Q

Water

Cohesion

A

Water molecules stick together because of the intramolecular hydrogen bonds, it also causes surface tension

Transport of water in the xylem relies on water molecules sticking to each other as they are transported up the xylem in the transpiration system

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7
Q

Water

Chemical Reactions

A

Waters thermal stability and solvent properties make it an ideal environment for chemical reactions

Water is also a reactant e.g. hydrolysis reactions and photosynthesis

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8
Q

Hydrophobic

A

Water repelling

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9
Q

Hydrophilic

A

Associates easily with water molecules

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10
Q

Proteins

Function

A 
Structure
Transport 
Enzymes
Antibodies
Most hormones
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11
Q

Proteins

Monomer

A

Amino Acids

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11
Q

Proteins

Polymer

A

Polypeptides

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12
Q

Amino Acid

Structure

A

Amine group H-N-H
|
Residual R-C-H
|
Carboxylic Acid group O=C-OH

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13
Q

Breaking A Peptide Bond

A

With a hydrolysis reaction - adding water

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14
Q

Residual

A

Differentiates between different amino acids

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15
Q

Forming A Peptide Bond

A

A condensation reaction removes OH from the carboxylic acid group of one amino acid and the H from the amine group of another amino acid
-a water molecule (h2O) is released and the bond forms

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16
Q

Dipeptide

A

Two amino acids joined together by a peptide bond

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18
Q

Polypeptide

A

A chain of amino acids joined together by peptide bonds

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19
Q

Primary Structure

A

The sequence of amino acids in a polypeptide chain

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19
Q

Protease Enzyme

A

An enzyme that breaks down proteins

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20
Q

Secondary Structure

A

Assumed in the rough endoplasmic reticulum The coiling of an amino acid chain into an alpha helix held together by hydrogen bonds
Polypeptide chains can link together with hydrogen bonds holding the parallel chains in beta pleated sheets

Both alpha helices and beta pleated sheets can occur in the same protein

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20
Q

Tertiary Structure

A

The secondary structure of the polypeptide chain bends and folds to produce a precise 3D structure

This is held together by:
Hydrogen Bonds
Ionic Bonds
Disulphide Bonds

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21
Q

Quaternary Structure

A

Several polypeptide chains linked together

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23
Q

Denaturation

A

An irreversible change in the tertiary structure of a protein molecule
Leading to a loss of function in most proteins

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25
Q

Haemoglobin

A

A transport protein

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26
Q

Haemoglobin

Structure

A

Water soluble
Globular protein
Made up of four separate polypeptide chains, a quaternary structure
Two called alpha chains and two called beta chains

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27
Q

Haemoglobin

Function

A

High affinity for oxygen
Bonds oxygen in the lungs and carries it to the tissues where it releases it
An oxygen atom can bind to the iron in a haem group
haemoglobin + oxygen = oxyhemoglobin
One complete haemoglobin molecule can bind up to four oxygen molecules

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28
Q

Tertiary Structure

Disulphide Bond

A

Forms between two sulphur containing R groups

A covalent bond

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29
Q

Collagen

Structure

A

A collagen molecule is made up of three polypeptide chains wound around each other like a twisted rope
Each chain is made up of around 1000 amino acids
Hydrogen bonds between the chains giving the structure strength
Each collagen molecule forms covalent bonds, cross links, with the molecules next to it
This structure is a fibril many fibrils together form a collagen fibre

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30
Q

Collagen

Function

A

To provide mechanical strength
Walls of the arteries have a layer of collagen to prevent blood being pumped at high pressure from bursting the walls
Tendons are mostly collagen
Bones are formed from collagen and reinforced with calcium phosphate
Cartilage and connective tissue are made of collagen

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31
Q

Collagen

A

A structural protein

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32
Q

Proteins

Test

A

Biuret Test

  • Add Biuret reagent which contains sodium hydroxide and copper sulphate to the sample
  • These chemicals react with the peptide bonds found in proteins
  • If protein is present the colour changes from blue to purple/lilac
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33
Q

Tertiary Structure

Ionic Bonds

A

From between polar R groups
R groups are polar if the electrons are unevenly distributed
Non polar R groups will be at the centre of the protein because they are hydrophobic and the protein is formed inside a cell so is surrounded by water

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35
Q

Carbohydrates

Function

A

Immediate energy source e.g. glucose
Energy store e.g. starch
Structural molecule e.g. cellulose

35
Q

Monosaccharides

Properties

A 
Soluble in water 
- means that they affect water potential for osmosis
- can be transported easily in solution
Sweet tasting
Form crystals
36
Q

Monosaccharides

How Are They Grouped

A

Grouped according to the number of carbon atoms in the molecule

37
Q

Triose Sugars

A

Monosaccharides with three carbon atoms per molecule

38
Q

Pentose Sugars

A

Monosaccharides with five carbon atoms per molecule

38
Q

Hexose Sugars

A

Monosaccharides with six carbon atoms per molecule

38
Q

Glycosidic Bond

A

Covalent bond formed between two monosaccharide molecules
Formed by a condensation reaction
Notation x-y glycosidic bond
- bond between the carbon x atom of one molecule and the carbon y atom of another molecule
- e.g. 1-4 glycosidic bond

38
Q

Breaking a Glycosidic Bond

A

Hydrolysis reaction

39
Q

Disaccharide

A

Two monosaccharide molecules joined together by a glycosidic bond

39
Q

Disaccharides

Examples

A

Sucrose
Maltose
Lactose

39
Q

Maltose

Structure

A

Glucose + Glucose

40
Q

Monosaccharides

Examples

A

Alpha Glucose
Beta Glucose
Fructose
Galactose

41
Q

Lactose

Structure

A

Glucose + Galactose

42
Q

Sucrose

Structure

A

Glucose + Fructose

43
Q

Carbohydrates

Monomer

A

Monosaccharides - simple sugars

43
Q

Carbohydrates

Polymer

A

Polysaccharides

44
Q

Polysaccharides

A

Polymers of monosaccharides consisting of hundreds to thousands of monosaccharide molecules joined together by glycosidic bonds

44
Q

Polysaccharides

Examples

A 
Starch
- Amylose
- Amylopectin
Glycogen
Cellulose
45
Q

Polysaccharides

Properties

A

Insoluble in water

45
Q

Amylose

Structure

A

Polymer of many alpha glucose monomers
Joined together by 1-4 glycosidic bonds
One un branched chain
Long chains of amylose coil into spirals go because of the shape of the glucose molecules and the formation of glycosidic bonds
There are 6 alpha glucose molecules in each turn of the spiral

46
Q

Amylose

Test

A

Add iodine

If present colour change from yellow/brown to deep blue

46
Q

Amylopectin

Structure

A

Polymer of alpha glucose molecules
Branched chain
1-4 glycosidic bonds hold the molecules in each branch together
1-6 glycosidic bonds hold the branches together

47
Q

Amylopectin

Test

A

Add iodine

If present colour change from yellow/brown to red/purple

48
Q

Starch

Structure

A

Long amylose chains

Plus branched chains of amylopectin

49
Q

Starch

Properties

A

Insoluble
Compact
Easier to break down
Energy storage molecule

50
Q

Starch

Function

A

Energy storage molecule in plants

51
Q

Starch

Test

A

Add iodine

If present colour change from yellow/brown to blue/black

52
Q

Cellulose

Structure

A

Polymer of beta glucose molecules
Adjacent molecules are opposite ways up
1-4 glycosidic bonds hold long chains of beta glucose together
Hydrogen bonds between chains

53
Q

Cellulose

Properties

A

Insoluble
Structural molecule
Humans do not have an enzyme which can break down cellulose
Very strong

54
Q

Cellulose

Function

A

Forms cell walls in plants

Forms fibre/roughage in a human diet to keep digestive system functioning

55
Q

Glycogen

Structure

A 
Polymer of alpha glucose molecules 
Large branched molecule
1-4 glycosidic bonds in branches
1-6 glycosidic bonds between branches
Shorter 1-4 linked branches than starch and more branches
56
Q

Glycogen

Properties

A

Insoluble
More compact than starch
Energy storage molecule

57
Q

Glycogen

Function

A

Energy storage molecule in animals

58
Q

Reducing Sugars Test

A
  • Add Benedict’s Solution
  • Heat in a water bath at 80°C
  • If present colour change from blue to the formation of orange/red precipitate
  • The darker the red of the precipitate the more reducing sugar there is
59
Q

Other Names for Lipids

A

Fats

Oils

60
Q

Non-Reducing Sugars Test

A
  • If a reduce sugars test is negative
  • Add hydrochloric acid and boil
  • Cool
  • Neutralise with sodium hydrogen carbonate or sodium carbonate
  • Repeat the reducing sugars test
  • if the second test is positive the a non reducing sugar was present in the original sample
61
Q

Three elements found in lipids

A

Carbon
Oxygen
Hydrogen

62
Q

Determining Glucose Concentration Using Colorimetry

A
  • Pour 5ml of glucose solutions of known concentration into test tube
  • Add Benedict’s solution
  • Heat in a water bath at 80°C
  • Pass each through filter paper to remove the orange/red precipitate
  • Use a sample of water to get a 100% transmission reading from the colorimeter
  • Put each concentration in the colorimeter and plot the results on a graph to draw a calibration curve
  • Repeat the process with the unknown sample
  • Read of the graph the concentration that would produce the colorimeter reading of the sample
63
Q

Structure of Lipids

A

Three fatty acid chains joined by an ester bond from a condensation reaction to one molecule of glycerol

66
Q

Glycerol

Structure

A 
H
     |
H-C-OH
     |
H-C-OH
     |
H-C-OH
     |
    H
67
Q

Carbohydrates

Contain Which Atoms

A

Oxygen
Hydrogen
Carbon

68
Q

Fatty Acid

Structure

A

A carboxylic acid group on the end of a hydrocarbon chain

69
Q

Carbon Atom Bonds

A

Each carbon atoms can only have four bonds

70
Q

Unsaturated

A

Has double bonds

72
Q

Saturated

A

Only single bonds

74
Q

Carboxylic Acid Group

A

OH-C=O

76
Q

Phospholipid

Structure

A

A glycerol molecules bonded to two fatty acid chains and a phosphate

77
Q

Triglyceride

Structure

A

One glycerol molecule

Three fatty acid chains joined to the glycerol molecule by an ester bond

78
Q

Cholesterol

Structure

A

Four carbon-based ring structures joined together

81
Q

Phospholipid

Function

A

Forms a molecule that is part hydrophobic and part hydrophilic, ideal for cell membranes
Phosphate group may have carbohydrates attached, these glycolipids are used for cell signalling

82
Q

Cholesterol

Function

A

Forms a small thin molecule that fits into the lipid bilayer to give strength and stability
Used to form the steroid hormones

83
Q

Triglyceride

Function

A

Compacts energy store
Insoluble in water so it doesn’t affect cell water potential
Stored as fat which also has thermal insulation and protective properties

84
Q

Emulsion Test for Lipids

A

Mix the sample with ethanol in a test tube so that some of it dissolves
Pour the liquid (ethanol) into another texture containing water
Cloudy emulsion on the surface indicates the presence of lipids

AS Biology (15 decks)

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