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F212 Biological Molecules Flashcards

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
Denaturation
An irreversible change in the tertiary structure of a protein molecule Leading to a loss of function in most proteins
25
Haemoglobin
A transport protein
26
Haemoglobin | Structure
Water soluble Globular protein Made up of four separate polypeptide chains, a quaternary structure Two called alpha chains and two called beta chains
27
Haemoglobin | Function
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
28
Tertiary Structure | Disulphide Bond
Forms between two sulphur containing R groups | A covalent bond
29
Collagen | Structure
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
30
Collagen | Function
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
31
Collagen
A structural protein
32
Proteins | Test
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
33
Tertiary Structure | Ionic Bonds
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
35
Carbohydrates | Function
Immediate energy source e.g. glucose Energy store e.g. starch Structural molecule e.g. cellulose
35
Monosaccharides | Properties
``` Soluble in water - means that they affect water potential for osmosis - can be transported easily in solution Sweet tasting Form crystals ```
36
Monosaccharides | How Are They Grouped
Grouped according to the number of carbon atoms in the molecule
37
Triose Sugars
Monosaccharides with three carbon atoms per molecule
38
Pentose Sugars
Monosaccharides with five carbon atoms per molecule
38
Hexose Sugars
Monosaccharides with six carbon atoms per molecule
38
Glycosidic Bond
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
Breaking a Glycosidic Bond
Hydrolysis reaction
39
Disaccharide
Two monosaccharide molecules joined together by a glycosidic bond
39
Disaccharides | Examples
Sucrose Maltose Lactose
39
Maltose | Structure
Glucose + Glucose
40
Monosaccharides | Examples
Alpha Glucose Beta Glucose Fructose Galactose
41
Lactose | Structure
Glucose + Galactose
42
Sucrose | Structure
Glucose + Fructose
43
Carbohydrates | Monomer
Monosaccharides - simple sugars
43
Carbohydrates | Polymer
Polysaccharides
44
Polysaccharides
Polymers of monosaccharides consisting of hundreds to thousands of monosaccharide molecules joined together by glycosidic bonds
44
Polysaccharides | Examples
``` Starch - Amylose - Amylopectin Glycogen Cellulose ```
45
Polysaccharides | Properties
Insoluble in water
45
Amylose | Structure
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
Amylose | Test
Add iodine | If present colour change from yellow/brown to deep blue
46
Amylopectin | Structure
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
Amylopectin | Test
Add iodine | If present colour change from yellow/brown to red/purple
48
Starch | Structure
Long amylose chains | Plus branched chains of amylopectin
49
Starch | Properties
Insoluble Compact Easier to break down Energy storage molecule
50
Starch | Function
Energy storage molecule in plants
51
Starch | Test
Add iodine | If present colour change from yellow/brown to blue/black
52
Cellulose | Structure
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
Cellulose | Properties
Insoluble Structural molecule Humans do not have an enzyme which can break down cellulose Very strong
54
Cellulose | Function
Forms cell walls in plants | Forms fibre/roughage in a human diet to keep digestive system functioning
55
Glycogen | Structure
``` 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
Glycogen | Properties
Insoluble More compact than starch Energy storage molecule
57
Glycogen | Function
Energy storage molecule in animals
58
Reducing Sugars Test
- 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
Other Names for Lipids
Fats | Oils
60
Non-Reducing Sugars Test
- 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
Three elements found in lipids
Carbon Oxygen Hydrogen
62
Determining Glucose Concentration Using Colorimetry
- 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
Structure of Lipids
Three fatty acid chains joined by an ester bond from a condensation reaction to one molecule of glycerol
66
Glycerol | Structure
``` H | H-C-OH | H-C-OH | H-C-OH | H ```
67
Carbohydrates | Contain Which Atoms
Oxygen Hydrogen Carbon
68
Fatty Acid | Structure
A carboxylic acid group on the end of a hydrocarbon chain
69
Carbon Atom Bonds
Each carbon atoms can only have four bonds
70
Unsaturated
Has double bonds
72
Saturated
Only single bonds
74
Carboxylic Acid Group
OH-C=O
76
Phospholipid | Structure
A glycerol molecules bonded to two fatty acid chains and a phosphate
77
Triglyceride | Structure
One glycerol molecule | Three fatty acid chains joined to the glycerol molecule by an ester bond
78
Cholesterol | Structure
Four carbon-based ring structures joined together
81
Phospholipid | Function
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
Cholesterol | Function
Forms a small thin molecule that fits into the lipid bilayer to give strength and stability Used to form the steroid hormones
83
Triglyceride | Function
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
Emulsion Test for Lipids
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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