Amino Acids & Proteins Flashcards
Structure of proteins influences…
The binding of different molecules
All peptides, polypeptides and proteins in the mammals are polymers of…
Alpha-L-amino acids
How many alpha-amino acids are used to make up proteins
20
Give the general structure of an amino acid
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Which functional groups are found on alpha-amino acids, peptides and proteins?
- Carboxylic (-COOH)
- Amino (-NH2)
Attached to the same carbon atom (alpha carbon)
All amino acids in proteins exhibit which configuration?
Why?
Absolute steric configuration
Based on: Proteinogenic L-amino acids, related to L-glyceraldehyde
What is a monoamino monocarboxylic acid?
Amino acids with aliphatic R-groups
List the monoamino monocarboxylic acids
- Glycine
- Alanine
- Valine
- Leucine
- Isoleucine
List the non-aromatic amino acids with Hydroxyl R-groups
- Serine
- Threonine
List the amino acids with sulphur-containing R-groups
- Cysteine
- Methionine
Give the amino acids with aromatic rings
- Phenylalanine
- Tyrosine
- Tryptophan
Give the interaction
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Hydrogen bond
Name the interaction
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Van der Waals
Name the interaction
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Disulphide bridge
Give the interaction
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Ionic bond
What is happening in the figure?
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- Condensation of two amino acids
- Forming a dipeptide with a peptide bond
What is shown?
What is shown in the red and blue circles?
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Polypeptide chain
- Red circle: N-terminal
- Blue circle: C-terminal
Isoelectric point
pH value where the amino acid has no net charge
What classifies globular proteins?
They are water soluble
What classifies fibrous proteins?
They are water insoluble
What are intermediate proteins?
- Water soluble
- Rod-like
- Found in myosin and fibrinogen
List the protein classifications differing by shape or water solubility
- Globular proteins
- Fibrous proteins
- Intermediate proteins
List the proteins classifications by differing compositions
- Simple proteins
- Conjugated proteins
Simple proteins
During hydrolysis: Only amino acids/amino acid derivatives produced
Conjugated proteins
Conjoined simple protein and non-protein compound
Prosthetic group of: Glycoproteins
Carbohydrates
Prosthetic group of: Nucleoproteins
Nucleic acids
Prosthetic group of: Phosphoproteins
Phosphoric acid
Prosthetic group of: Chromoproteins
Coloured prosthetic group
Example of a hemoprotein
Haemoglobin
Lipoproteins contain…
Lipid molecules
Prosthetic group of: Flavoproteins
Flavin
Prosthetic group of: Metalloproteins
Metals
List 3 conjugated protein types
- Glycoproteins
- Nucleoproteins
- Phosphoproteins
List protein types differing by function
- Contractile proteins
- Transport proteins
- Enzymes
- Protein hormones
- Toxic proteins
Primary structure of proteins
Amino acid sequence
Secondary structure of proteins
- α-helix/Beta-pleated sheet/Collagen helix
- Regularly repeating units
Tertiary structure of proteins
- Polypeptide chain
- 3-D structure by complete folding
Quarternary structure of proteins
Assembled subunits
In moist heat:
Alpha-keratin →
Beta-keratin
Native conformation
- The 3-D conformation of a protein
- Stable and active at optimal temp. and pH
Function of proteins arises from…
Chain-conformation
(Secondary & Tertiary structure)
Functional shape of a protein occurs during which stage?
Protein folding
(Active, native conformation formation)
Denaturation of proteins
Unfolding of chains
(Can be reversible - renaturation)
How does heat denature proteins?
Examples
Breaks:
- Hydrophobic interactions
- Hydrogen bonds
Examples:
- Egg when it is fried
- Skin when it is burned
How do acids and bases denature proteins?
By breaking ionic bonds
How do reducing/oxidising agents denature proteins?
Convert:
Disulphide bonds → free sulfhydryl groups
How do hydrogen-bonding solvents denature proteins?
Example
Disruption of hydrogen bonds
Ethanol - precipitates bacteria proteins
How do heavy metal ions denature proteins?
Example
React with sulfhydryl bonds to form carboxylate ions
AgNO3 previously used to treat eyes of newborns for gonorrhoea
How does salting-out denature proteins?
Example of use
Removes the hydrate hull
Used in the separation of proteins
Denaturing agents used in gel electrophoresis
- Sodium dodecyl sulphate
- Mercaptoethanol
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Haemoglobin - Quarternary structure
Peptide bond:
- Bond type
- Location
- Primary, covalent bond
- Between amino acids
Disulphide bond:
- Bond type
- Location
- Example
- Primary, covalent bond
- Between -SH containing side chains
- 2 x Cysteine molecules form these bonds → Cystine formed
Ionic bond:
- Bond type
- Location
- Primary bond
- Between polar, charged side chains
- Between carboxyl group of an acidic and a basic amino group
Dipol-dipol interaction:
- Bond type
- Location
- Secondary bond
- Between polar, non-charged sidechains
The partially negative portion of molecule attracted to partially positive portion of the other
Van der Waals dispersion force:
- Bond type
- Location
- Secondary, hydrophobic bond
- Between non-polar side chains
- Weakest of all intermolecular forces*
- Used when numerous atoms are present*
- A temporary* partial negative charge on atoms
List the bonds of the secondary and tertiary structures
- Disulphide bond
- Ionic bond
- Dipol-dipol interaction
- Van der Waals dispersion force
- H-bonds
List the bonds of the quarternary structure
- Dispersion
- Dipol
- H-bond
- Disulphide bond
Give examples of acidic amino acids
- Glu
- Asp
Give examples of basic amino acids
- Lys
- Arg
- His