1
Q
What is the general formula of α-amino acids?
A
The general formula is RCH(NH2)COOH, where R can be a hydrogen, alkyl group, or carbon-containing group.
2
Q
What is the simplest α-amino acid?
A
Aminoethanoic acid (glycine), H2NCH2COOH where R = H.
3
Q
What defines the α-carbon atom in an α-amino acid?
A
The α-carbon atom is the carbon that is bonded to the -NH2 group and is next to the carboxylic acid group.
4
Q
What is the traditional name for 2-amino-3-phenylpropanoic acid?
A
Phenylalanine.
5
Q
What is the traditional name for 2-amino-3-hydroxypropanoic acid?
A
Serine.
6
Q
What is the traditional name for 2-amino-3-sulfhydrylpropanoic acid?
A
Cysteine.
7
Q
Do all α-amino acids contain a chiral center?
A
Apart from aminoethanoic acid, all α-amino acids contain a chiral center.
8
Q
What are the two optical isomers of 2-aminopropanoic acid (alanine)?
A
The two optical isomers are mirror image forms of alanine.
9
Q
Fill in the blank: Cystine has the formula HOOCC-C-C-S-S-NH2.
A
Cystine.
10
Q
Does cysteine contain any chiral centers?
A
Yes, cysteine contains a chiral center.
11
Q
What state do a-amino acids exist in at room temperature?
A
Solids
12
Q
What is the melting temperature of aminoethanoic acid?
A
240°C
13
Q
What is the melting temperature of hydroxyethanoic acid?
A
75-80°C
14
Q
What is the melting temperature of methoxyethanoic acid?
A
8°C
15
Q
Why do a-amino acids have higher melting temperatures than expected?
A
Because they exist as zwitterions
16
Q
What happens to the hydrogen ion in the zwitterion formation of a-amino acids?
A
A hydrogen ion (H+) is lost from the carboxylic acid group and gained by the nitrogen atom of the amino group
17
Q
What is the zwitterion formula of aminoethanoic acid?
A
H—C— + NH
18
Q
True or False: a-amino acids generally have lower melting temperatures than similar sized molecules.
A
False
19
Q
Fill in the blank: The melting temperatures of a-amino acids are much ______ than might be expected.
A
higher
20
Q
What type of compounds are a-amino acids compared to other similar sized molecules?
A
Solids
21
Q
What is the boiling temperature of methoxyethanoic acid?
A
203°C
22
Q
What is the ionic nature of zwitterions?
A
Zwitterions exhibit strong ionic forces between positive and negative ions
23
Q
Why do a-amino acids have higher melting temperatures than covalently bonded compounds?
A
More energy is needed to overcome the strong ionic forces
24
Q
What type of amino acid is aminoethanoic acid?
A
Neutral amino acid
25
What does the zwitterion dipolar form of amino acids suggest about their solubility?
a-amino acids are soluble in water
26
What is the solubility of aminoethanoic acid at 25°C?
25g in 100 cm³ of water
27
What is the solubility of 2-amino-3-phenyl-propanoic acid at 25°C?
3g in 100 cm³ of water
28
What do aqueous solutions of a-amino acids contain?
Zwitterions
29
What is the term for the pH at which amino acids exist as zwitterions?
Isoelectric point
30
How does the isoelectric point vary?
It varies depending on the amino acid
31
What is the isoelectric point of aminoethanoic acid?
pH 6.0
32
If the pH of the solution is below the isoelectric point, what does the amino acid act as?
Base by accepting a hydrogen ion
33
If the pH of the solution is greater than the isoelectric point, what does the amino acid act as?
Acid by losing a proton
34
What is a dipeptide?
A dipeptide is formed when two amino acid molecules join together in a condensation reaction.
35
What type of reaction forms dipeptides?
Condensation reaction.
36
What groups react to form a dipeptide?
The COOH group of one amino acid and the NH2 group of another amino acid.
37
Fill in the blank: A dipeptide is formed when two amino acids join together in a _______.
condensation reaction.
38
True or False: Dipeptides are only formed from the reaction of the NH2 group of one amino acid with the COOH group of the same amino acid.
False.
39
What is introduced into the condensation product when a dipeptide is formed?
A peptide linkage
## Footnote
A peptide linkage is also known as a peptide bond or amide linkage.
40
What is aspartame?
An artificial sweetener used in diet carbonated sugar-free drinks
## Footnote
Aspartame is the methyl ester of the condensation product between phenylalanine and aspartic acid.
41
What is a polypeptide?
A long chain of condensed amino acids joined together by peptide linkages.
42
Fill in the blank: A dipeptide introduces a _______ into the condensation product.
peptide linkage
43
What amino acids are part of the polypeptide chain structure shown?
* Ala
* Gly
* Phe
* Ser
44
True or False: A peptide bond is also referred to as an amide linkage.
True
45
What are the three letter abbreviations for alanine, glycine, phenylalanine, and serine?
* Ala
* Gly
* Phe
* Ser
## Footnote
These abbreviations simplify the representation of amino acids in polypeptide formulas.
46
What is the systematic name for alanine?
2-aminopropanoic acid
## Footnote
Alanine is a common amino acid used in protein synthesis.
47
What is the systematic name for glycine?
aminoethanoic acid
## Footnote
Glycine is the simplest amino acid.
48
What are proteins formed from?
Polypeptides formed by condensing many amino acids together
## Footnote
Proteins are crucial for various biological functions.
49
What is the structure of human insulin?
Consists of two amino acid chains joined by disulfide bridges (-S-S-)
## Footnote
Insulin plays a key role in glucose metabolism.
50
What happens to people with diabetes regarding insulin production?
They are not able to produce enough insulin
## Footnote
This leads to elevated sugar levels in the blood.
51
What is the external method of providing insulin to diabetics?
Injections
## Footnote
Insulin therapy is essential for managing diabetes.
52
What is the role of haemoglobin in the blood?
It is the oxygen-carrying protein
## Footnote
Haemoglobin is vital for transporting oxygen to tissues.
53
What effect can a single amino acid replacement have in haemoglobin?
It can have a profound effect on its function
## Footnote
Changes in amino acid sequence can lead to diseases.
54
What mutation occurs in sickle cell anaemia?
Glutamic acid is replaced by valine in haemoglobin
## Footnote
This mutation affects oxygen-carrying capacity.
55
What is the result of the mutation in sickle cell anaemia?
Reduced oxygen-carrying capacity of haemoglobin
## Footnote
This can lead to various health complications.
56
What advantage does the sickle cell mutation provide?
Increased resistance to malaria
## Footnote
This mutation offers a survival benefit in malaria-endemic regions.
57
What is the primary structure of a protein?
The order of amino acids in the chain(s)
58
How many amino acids can make up polypeptide chains?
Twenty amino acids
59
How many essential amino acids cannot be made in the body?
Eight essential amino acids
60
Name two examples of essential amino acids.
* Valine
* Lysine
61
How many possible dipeptides can be formed from twenty amino acids?
400 possible dipeptides
62
How many possible tripeptides can be formed from twenty amino acids?
8000 possible tripeptides
63
What does the secondary structure of proteins describe?
How the amino acid chains are arranged
64
What are the two common arrangements in the secondary structure of proteins?
* a-helix
* B-pleated sheet
65
Describe the a-helix structure of a protein.
The polypeptide chain is coiled into a spiral maintained by hydrogen bonds
66
What maintains the shape of the a-helix structure?
Hydrogen bonds between the N-H hydrogen atom and the C=O carbonyl oxygen atom
67
In which types of proteins is the a-helix structure commonly found?
* Muscle
* Wool
68
What happens to hydrogen bonds in wool fibers when they are stretched?
The hydrogen bonds are broken
69
What remains intact when wool fibers are stretched?
The strong disulfide bonds
70
What occurs when the stretching force is removed from wool fibers?
The hydrogen bonding is restored and the wool resumes its original shape
71
What is another protein that has the a-helix structure?
Keratin
72
What is the common arrangement of proteins that involves hydrogen bonds and different chains?
ß-pleated sheet
## Footnote
The structure is maintained by hydrogen bonds between C=O and N—H groups in different chains.
73
What forces are responsible for producing a pleated sheet structure in proteins?
Van der Waals forces
## Footnote
These forces contribute to the folding pattern rather than allowing a flat arrangement.
74
What does the tertiary structure of proteins refer to?
The way in which the protein chain is folded
## Footnote
This folding is crucial for the protein's functionality.
75
What type of proteins tend to be insoluble in water?
Fibrous proteins
## Footnote
These proteins have a chain length many times their diameter.
76
What are globular proteins characterized by?
Roughly spherical shape
## Footnote
Most enzymes and proteins that operate in an aqueous environment fall into this category.
77
In water, how do globular proteins typically orient their polar and lipophilic groups?
Polar groups on the surface and lipophilic groups towards the interior
## Footnote
This arrangement helps maintain solubility and stability in aqueous environments.
78
What are enzymes?
Compounds that catalyse chemical reactions
## Footnote
Enzymes are macromolecular biological catalysts that facilitate over 5000 biochemical reactions.
79
How do enzymes work?
By lowering the activation energy necessary for a reaction
## Footnote
This is similar to the function of other catalysts.
80
What is the primary structure of most enzymes?
Proteins
## Footnote
Enzymes have unique 3-dimensional structures that are crucial for their function.
81
Why are enzymes essential to life?
They maintain the speed of biochemical reactions in the body
## Footnote
Without enzymes, reactions would occur at a much slower rate.
82
What is amylase?
An enzyme that catalyses the hydrolysis of starch into sugars
## Footnote
Amylase is present in human saliva.
83
What happens when starch is hydrolysed by amylase?
Smaller molecule sugars are formed
## Footnote
This can cause rice and potatoes to taste slightly sweet in the mouth.
84
What is a developing area of research regarding enzymes?
Their commercial use
## Footnote
The application of enzymes in various industries is being explored.
85
Name a type of enzyme used in laundry applications.
Amylases, Lipases, Proteases
## Footnote
These enzymes help remove stains caused by starch, fats, or proteins.
86
Which enzyme is used in brewing?
Amylases, Glucanases, Proteases
## Footnote
These enzymes hydrolyse polysaccharides and proteins to smaller molecules.
87
What is the role of rennin in dairy applications?
Hydrolysing protein in cheese making
## Footnote
Rennin is an enzyme specifically used in the dairy industry.
88
How many enzymes have commercial uses?
About 150 enzymes have commercial uses.
89
What conditions can enzymes operate in?
Aqueous conditions of mild acidity or alkalinity.
90
What is one common use of enzymes in detergents?
To remove stains from clothes.
91
What issues can consumers face when using detergents containing enzymes?
A number of consumers suffer from allergies.
92
What do amylases do in laundry work?
Degrade starches to water-soluble sugars.
93
What is the function of lipases in laundry?
Hydrolyse fats.
94
What do proteases digest?
Proteins.
95
What enzyme is used in the dairy industry for cheese making?
Rennin.
96
What protein does rennin degrade in cheese making?
K-casein.
97
What is the main component of curd from which cheese is made?
The hydrophobic product from the degradation of k-casein.
