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Chemistry (Unit 4) > Unit 4 - Proteins, Carbohydrates and Lipids > Flashcards

Unit 4 - Proteins, Carbohydrates and Lipids Flashcards

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1
Q

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Amino Acids

A

General structure: involves 2 carbon molecules, the one on the left side has a NH2 molecule (amino functional group attached) , the one in the middle has one hydrogen atom attached and one R group. The one on the right side has a carboxyl functional group attached

Central carbon is called alpha-carbon and numbering begins from carboxyl functional group

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2
Q

Amino Acid Abbreviations

A

Amino Acids are commonly given by three ltter abbreviations. For example, alanine is given by Ala, Glycine is Gly

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3
Q

Properties of R Groups in Amino Acids

A

Difference between each amino acid is their R group, side chain may be:
- non-polar (-CH3 in valine)
- polar (CH2COOH in aspartic acid)
The side chain can also contain groups which may act as
- proton donors (acidic carboxyl group)
- proton acceptos (basic amino group)

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4
Q

Lack of essential amino acids

A

A healthy diet should contain proteins which include the 9 essential amino acids that can only be obtained through food
Lack of the essential amino acids can cause serious diseases such as ‘Kwashiorkor’

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5
Q

Amino Acids with Acid-Base Properties

A

Contains an amino group and carboxyl functional groups. They are amphoteric, acting as an acid or base depending on the circumstances.
The nature of the side chain can also affect the acid-base properties

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6
Q

Zwitterions

A
  • NH2 can act as a base, accepting a proton to to become a NH3+ group
  • COOH can act as an acid, donating a proton to become a COO- group

+H3N - CH(R) - COO- (called a zwitterion or dipolar ion)

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7
Q

Crytalline Nature of Zwitterions

A

The crytalline nature and relatively high melting points of amino acids in the solid state is evidence that in the solid state the zwitterion is present and that in the solid state, amino acids exist as ionic crystals.

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8
Q

Acid - Base Properties (Equilibrium)

A

The dual acidic and basic nature of amino acids means that different forms of an amino acid can be in equilibrium in a solution. The predominant form is dependant on the pH of the solution and the particular amino acid concerned

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9
Q

Intermediate pH (Amino Acids)

A

At intermediate pH, the cation +H3N−CH(R)−COOH is most abundant.

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10
Q

Low pH (Amino Acids)

A

At low pH, the cation +H3N−CH(R)−COOH is most abundant. The H3O+ ions in the solution can react with the amino acid:

+H3N−CH(R)−COO−(aq) + H3O+(aq) -> +H3N−CH(R)−COOH(aq) + H2O(l)

If the concentration of H3O+(aq) is very high (as it is in a solution of low pH), the position of this equilibrium lies well to the right

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11
Q

High pH (Amino Acids)

A

At high pH, the anion H2N−CH(R)−COO− is most abundant. The OH− ions in solution can react with the amino acid according to the equation:

+H3N−CH(R)−COO−(aq) + OH−(aq) -> H2N−CH(R)−COO−(aq) + H2O(l)

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12
Q

Low pH (General formula)

A

+NH3- CHR- CO2OH

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13
Q

Intermediate pH

A

+NH3-CHR-COO-

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14
Q

High pH

A

NH2- CHR - CO2O-

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15
Q

Formation of Proteins

A

A condensation reaction between a carboxyl group and amine forms a peptide link and water

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16
Q

Peptide Structure

A

Amide
C=O - NH

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17
Q

Di-Peptide

A

When two peptides react, a peptide link is formed
Occurs when two amino acids react together

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18
Q

Structural Formation of a Di-peptide

A

The OH group of one of the amino acids and the and one of the hydrogens from the amine form the water and is removed
Then an amide is notable

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19
Q

Three Amino Acids

A

Tripeptide

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20
Q

Polypeptide

A

When there are more than three peptide links, the notation is of the first three letters of each amino acid (Ala + Glu + Gly + Cys….)

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21
Q

Protein

A

A polypetide made up of more than 50 amino acids is called a protein

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22
Q

N - Terminal

A

The longer chain with a free amino group at the end is known as an N-terminal

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23
Q

C - Terminal

A

The longer chain with a free carboxyl group is known as the C-terminal amino acid

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24
Q

Structures of Proteins

A

Primary structures, secondary structures, tertiary and quanterary structures

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25
Q

Primary Stucture of a Protein

A

The number, type and sequence of the amino acid units in a protein are known as the proteins primary structure.
Primary stucture may be represented by the three letter abbreviations
Sequence is written from left to right (n terminal to c terminal)

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26
Q

Secondary Structure of Proteins

A

Folding introduces a secondary level of structure in proteins
Bonds between the polar -NH group and the non polar -C=O

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27
Q

a - helix Protein

A

OH bonding from spirals of protein structures

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28
Q

B - helix Protein

A

Hydrogen bonds form links from neighbouring polypetide chain and become parallel to each other (example: every 2nd R group is a H)

29
Q

Causes for Tertiary Structures

A

The overall three-dimensional shapes of proteins are due to forces between the different functional groups in the R group or side chain of amino acid units.
The types of forces and bonds between the R groups cause proteins to adopt their different shapes.

30
Q

Tertiary Stuctures

A

A tertiary structure is produced by the three-dimensional
folding of its secondary structures (α-helices and β-pleated sheets). Proteins in solution fold spontaneously to increase their stability

31
Q

Bonding in Tertiary Structures

A

The side chains (R groups) of the amino acid units making up the polypeptide chain influence the overall three-dimensional shape of the molecule.
Not only are some side chains relatively large (such as in phenylalanine), but others also contain polar functional groups, or can become charged depending on the pH of their
surroundings.
In addition, some amino acids have hydrophobic (non-polar) chains,
which tend to fold towards the interior of protein molecules, away from contact with water molecules.

32
Q

Types of Tertiary Protein Bonding - Hydrogen Bonds

A

Require components in ther R group: −O−H, − N−H or −C=O
a hydrogen bond linking two parts of a
polypeptide chain

33
Q

Types of Tertiary Protein Bonding - Dipole/dipole
interactions

A

required components in the R group: any polar group such as those
containing −S−H, −O−H or −N−H
a dipole–dipole interaction linking two parts of a polypeptide chain

34
Q

Types of Tertiary Protein Bonding - Ionic
interactions

A

Required R groups: contains −NH3+ and another group that contains −COO−
an ionic interaction linking two parts of a polypeptide chain

35
Q

Types of Tertiary Protein Bonding - Covalent Cross Links

A

Required R Group: cysteine side groups react to form a disulfide
bridge (−S−S−)
a disulfide bridge linking two parts of a polypeptide chain

36
Q

Types of Tertiary Protein Bonding - Dispersion Forces

A

Required R group: any non-polargroup
dispersion forces can link two parts of a polypeptide chain

37
Q

Quanterary Structure of Proteins

A

Some proteins are composed of two or more polypeptide chains, and may even interact with non-protein molecules to produce a larger, more complex functional unit, known as the quaternary structure.
Haemoglobin is an example of a protein
with a quaternary structure.

38
Q

Fats

A

Fat is a name used to describe a large number of organic compounds belonging to an even larger class of biological molecules called lipids

39
Q

Fats Vs Oils

A

Fats and oils contain large non-polar molecules known as triglycerides. Fats and oils have very similar chemical structures and are distinguished simply on the basis of their physical state at room temperature. At room temperature:
* fats are solids
* oils are liquids.

40
Q

Glycerol Structure

A

3 straight chain carbons going upwards with OH attached
CH2OHCHOHCH2OH

41
Q

Fatty Acid Structures

A

A carboxyl group attached to a long unbranched hydrocarbon chain
HOO2C - Hydrocarbon tail

42
Q

Triglyceride Formation

A

Condensation reaction between a glycerol molecule and three molecules of fatty acids
The H groups of the hydroxide from the glycerol and the OH groups of the fatty acids are removed as water

43
Q

Saturated Fatty Acids

A

Saturated fatty acids have hydrocarbon chains that contain only single carbon– carbon bonds.
C(n)H(2n+1)COOH

44
Q

Monosaturated Fatty Acids

A

Monounsaturated fatty acids contain one carbon–carbon double bond in their hydrocarbon chain.
Monounsaturated fatty acids have the general formula C(n)H(2n−1)COOH.

45
Q

Polyunsaturated Fatty Acids

A

Polyunsaturated fatty acids contain more than one carbon–carbon double bond in their hydrocarbon chain.
General formula is C(n)H(2n–3)COOH

46
Q

Saturated Fats

A

Saturated fats are made from saturated fatty acids only. They are generally unreactive and exist as waxy solids at room temperature. Saturated fats occur in higher proportions in animal fats

47
Q

Unsaturated Fats: Omega-3 fatty acids and Omega-6 fatty acids

A

.An omega-3 fatty acid has a carbon–carbon double bond
on the third carbon from the omega carbon.
Omega carbon - carbon that is not attached to the carboxyl group

48
Q

Melting Points of Fats

A

The different melting points of triglycerides can be explained in terms of the length and degree of saturation of their fatty acid hydrocarbon chains.
This is due to the increasing strength of dispersion forces between fatty acid molecules as molecular mass increases.
The fatty acid tails can pack more closely and so these intermolecular forces become stronger.

49
Q

Cis-Fat Arrangement

A

Most naturally occurring unsaturated fatty acids have a cis-arrangement of the alkyl groups around the double bond.
This produces a permanent bend or ‘kink’ in the hydrocarbon chain.
As a result, the fatty acids are unable line up and pack closely together making them weaker

50
Q

Trans-Fat Arrangement

A

Trans fats are unsaturated fats with a trans orientation of hydrocarbon chains across the double bond.

51
Q

Hydrogenation

A

Partial reaction of the polyunsaturated fats in vegetable oils with hydrogen reduces the number of double bonds present. Hydrogenation is used commercially to increase the melting point of products

52
Q

Soponification - the manufacture of soaps

A

When triglyceride molecules are heated with sodium hydroxide, the three ester links in the triglyceride are hydrolysed.
In theory, water can be used for this reaction.
Reactions where water is used to break down a compound are known as hydrolysis reactions.
In practice, the reaction with water is very slow, so a strong base such as sodium hydroxide or potassium
hydroxide is used.

53
Q

General form of Soaponification

A

Triglyceride + 3NaOH -> glycerol and sodium salts of fatty acids
Breaks the O bonded to the ester
Sodium salts (R - COO-)

54
Q

Hydrolysis of Triglycerides in Body

A

Triglycerides undergo enzyme-catalysed hydrolysis during digestion.
Because triglycerides are insoluble in water their molecules remain intact as they pass through the digestive tract until they reach the small intestine.
In the small intestine, bile is used to process the triglycerides.

55
Q

Cleaning Action of Soaps

A

Water can bond with the charged carboxylate group at the end of the fatty acid ion. This charged end is referred to as the hydrophilic or ‘water-loving’ end of the ion.
This type of bonding is an example of ion–dipole bonding. On the other hand, the non-polar hydrocarbon chain tends not to dissolve in water.
It is referred to as hydrophobic or ‘water-hating’. It will mix readily with oil, due to the weak dispersion forces present

56
Q

Soap in Water

A

The hydrophobic sections of the soap are in the centre of the clump where they are in contact with each other.
This is a stable arrangement called a micelle

57
Q

Removing the Dirt

A

During the washing of clothes, vigorous agitation breaks up micelles formed by soap.
The non-polar ends of the soap particles are then able to position themselves in drops of oil or grease, leaving the hydrophilic end in the water.
As agitation continues, water forms ion–dipole bonds with the negatively charged carboxylate ends of the soap and the oil particle is lifted from the fabric

58
Q

Soaps Vs Detergents

A

Soaps are less effective than detergents in hard water due to the formation of insoluble metal salts.
Soaps in hard water:
2CH3(CH2)16COONa(aq) + Ca2+(aq) → (CH3(CH2)16COO)2Ca(s) + 2Na+(aq)

59
Q

Monosaccharides

A

Carbohydrates are made from the elements carbon, hydrogen and oxygen.
Carbohydrates usually have the general formula Cx(H2O)y, where x and y are whole numbers.
The smallest carbohydrates are the monosaccharides. They are white, sweet-tasting solids that are highly soluble in water.

60
Q

Carbohydrates in Equlibirium

A

Monosaccharides can exist as isomers in equilibrium.
There is a-gluecose where OH is on the botton (left) end of the 1st carbon
There is b-gluecose where OH is on the top (right) end of the 1st carbon

61
Q

Straight-Chain Carbohydrates

A

In their straight-chain form, monosaccharides are classified as either aldoses or ketoses depending on their carbonyl group.
The straight-chain form of glucose has an aldehyde functional group on C1 so it is classified as an aldose

62
Q

Disaccharides

A

Two monosaccharides can join to form disaccharides
Disaccharides are carbohydrates formed from the reaction between two monosaccharide molecules.
A condensation reaction occurs between the hydroxyl functional groups on neighbouring molecules and a water molecule is formed as a by-product with one O remaining.
The connection between the monosaccharide units is called an ether bond (or glycosidic bond in carbohydrates)

63
Q

Triangle of Sweetness

A

Similar to the requirement that the shape of a substrate molecule match the shape of the active site in an enzyme for the substrate to react, the sweetness of some substances is thought to be due to the shape of their molecules matching the shapes of the molecules that form the surface of our taste buds.

Two of these bonds to the taste buds are hydrogen bonds, and the third is formed with a non-polar site. The so-called ‘triangle of sweetness’

64
Q

Polysaccharides

A

Polysaccharides are generally insoluble in water and have no taste. The three most important biological polysaccharides are starch, cellulose and glycogen.

65
Q

Starch Formation - Amylose

A

Foods such as potato and sago have a high starch content. If the starch forms a linear polymer, it is known as amylose. The condensation polymerisation of α-glucose to produce amylose, which is a form of starch

66
Q

Starch - Amylopectin

A

A second form of starch, known as amylopectin, can form if some of the α-glucose molecules undergo condensation reactions between hydroxyl groups at different positions around the glucose rings.

In this way, occasional branches occur along the polysaccharide
chains occur after about 20–24 glucose units.

67
Q

Amylose and Amylopectin Solubilities

A

Amylose and amylopectin have different solubilities in water. The long molecules of amylose coil into spiral-like helices and pack together tightly, with many −OH groups inside the helices and away from contact with water.
Therefore, amylose is largely insoluble in cold water. However, in the case of amylopectin, the branching of its molecules restricts the coiling of the polymer, leaving many more −OH groups exposed so that it dissolves in water.

68
Q

Cellulose

A

The alternating nature of the −CH2OH group in cellulose allows for good alignment of hydroxyl groups between neighbouring cellulose molecules.
The result is hydrogen bonding between the molecules, resulting in a strong material that gives the plant support and rigidity.
The formations are between b - gluecose molecules

69
Q

Glycogen

A

The third polysaccharide formed from polymerisation of glucose is glycogen. Glycogen is a polymer of α-glucose but is highly branched in a similar fashion to amylopectin. (7-11 repeats)
Animals store glycogen that will metabolise to provide energy when glucose levels are low.
Glycogen is formed from excess glucose and stored in the liver or
muscle tissue.
If energy is needed, the glycogen can be broken down to glucose, which can then be used in cellular respiration.

Chemistry (Unit 4) (10 decks)

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