2.1.5 ( Part 2 ) - Biological molecules Flashcards
What are Lipids ?
They are large complex molecules known as macromolecules
Name examples of macromolecules ?
- Triglycerides
- Phospholipids
- Sterols
What is a triglyceride ?
A triglyceride is made up of glycerol molecule and three fatty acid molecules
Draw a digram to display the structure of a triglyceride ?
What happens during a condensation reaction resulting in a triglyceride ?
- During a condensation reaction, a hydroxyl group and a hydrogen atom is removed between the glycerol molecule and each fatty acid molecule
- This leads to the formation of three ester bonds and elimination of three water molecules producing a triglyceride
Draw a diagram to represent the formation of a triglycerides from one glycerol molecule and three fatty acids ?
What happens during a hydrolysis reaction of a triglyceride ?
- During a hydrolysis reaction, a water molecule is used to break an ester bond between a glycerol molecule and fatty acid molecule
- When three water molecules are used to break the ester bonds, the triglyceride is broken down into one glycerol molecule and three fatty acids
What is the name of the bonds that form between glycerol molecules and fatty acid molecules ?
An ester bond
What are the two different types of fatty acids ?
- Saturated ( contains only single C-C bonds )
- Unsaturated ( Contains at leats one multiple C-C bond )
What are the features of unsaturated fatty acids due to their structure ?
- Due to the presence of double bonds, this causes the molecule to kink/bend and means they cannot pack as closely together
- This causes it to be liquid at room temperature rather than solid
What are phospholipids ?
A phospholipid is made up of one glycerol molecule, two fatty acids and a phosphate group
Explain the structure of phospholipids ?
- Due to their length, they have non-polar tails which are repelled by water/ hydrophobic
- The charged head is poler and therefore will interact with water/ is hydrophilic
What are the roles of lipids ?
- Formation of cell membranes
- Hormone production
- Electrical insulation
- Waterproofing
What is the function of triglycerides in particular ?
- Thermal insulation to reduce heat loss ( penguins )
- Cushioning of vital organs ( heart and kidneys )
- Buoyancy for aquatic animals ( whales )
Explain how phospholipids are important in the formation of the cell membrane ?
- Due to their structure, they can crate a phospholipid bilayer with the hydrophobic tails pointing inward creating a hydrophobic core while their hydrophilic heads point outward
- This allows phospholipids to separate the cytoplasm in cells from aqueous environments
What are sterols ?
Sterols are complex alcohol molecules which have dual hydrophilic/ hydrophobic characteristics
Name an example of a sterol ?
Cholesterol
Explain how cholesterol is important in the formation of cell membranes ?
- Cholesterol molecules are positioned between phospholipids and regulate the fluidity of the cell membrane
- They keep membranes fluid at low temperatures and prevent them from becoming too fluid at higher temperatures
What is the test for the presence of lipids called ?
The emulsion test
Describe the test for the presence of lipids in a sample ?
1 ) sample is mixed with ethanol
2 ) Solution is mixed with water and shaken
What is a positive and negative result when testing for presence of lipids ?
- If a white emulsion forms then lipids are present / positive
- If there is no change then it is negative
What is a protein ?
One or more polypeptides arranged as a complex macromolecule
What does an amino acid contain ?
An amino acid contains a central carbon atom bonded to a hydrogen atom, an amine group, a carboxyl group and a R group
Draw a diagram to represent the structure of an amino acid ?
Explain what happens during a condensation reaction between two amino acids ?
- During a condensation reaction, a hydroxyl group from the carboxyl group of one amino acid and a hydrogen atom from the amine group of another is removed
- This leads to the formation of a peptide bond, elimination of a water molecules and production of a dipeptide
What is a polypeptide ?
A long-chain molecule made of three or more amino acids chemically joined together by peptide bonds
What is the name of the bond that forms between amino acids ?
a peptide bond
Explain what happens during the hydrolysis reaction of a dipeptide ?
- During a hydrolysis reaction, a water molecule is added to a dipeptide to break a peptide bond between the two amino acids
- This results in two individual amino acids
Draw a diagram to represent the formation of a dipeptide from two amino acids ?
What are the different levels of protein structure ?
- Primary structure
- Secondary structure
- Tertiary structure
- Quaternary structure
What is the primary structure of protein ?
It is the sequence ( and number ) of Amin acids in a polypeptide and associated peptide bonds
What does the primary structure of a protein determine ?
- It affect how the polypeptide folds to give the proteins final shape
- It therefore affects the proteins shape and function
What is the secondary structure of a protein ?
The formation of hydrogen bonds between the amine group of one amino acid and the carboxyl group of another pulling them into regular patterns
What are the two main types of secondary structures of proteins ?
- Alpha helix ( coiling )
- Bet pleated sheets
What is the tertiary structure of a protein ?
The folding of a protein into a specific 3D structure depending on the various interactions between R groups of amino acids
What are the various interactions between R groups of amino acids in the tertiary and quaternary structure ?
- Hydrophilic and hydrophobic interactions
- Hydrogen bonds
- Ionic bonds
- Disulphide bonds/ bridges
Where do hydrophilic and hydrophobic interactions occur in the tertiary structure ?
They are weak interactions between polar and non-polar R groups of amino acids
Where do hydrogen bonds occur in the tertiary structure ?
They are the weakest bonds between two polar R groups of amino acids
Where do ionic bonds occur in the tertiary structure ?
They form between oppositely charged/ ionised R groups of amino acids
Where do disulphide bridges/ bonds occur in the tertiary structure ?
They are the strongest bonds formed between R groups of amino acids contains sulphur atoms
What does the tertiary structure of a protein determine ?
the tertiary structure determines the 3D structure of the protein and therefore its function
What is the quaternary structure of protein ?
The association of two or more proteins/ subunits to make a functioning protein
What are the different types of proteins ?
- Globular protiens
- Conjugated proteins
- Fibrous proteins
What are the features of globular proteins ?
- Coiled/ spherical- shaped
- Soluble in water
What are the functions of globular proteins ?
Regulate many processes such as chemical reactions, immunity and muscle contraction
Name an example of a globular protein ?
Insulin
Explain how Insulin’s structure as a globular protein helps aid its function ?
- Insulin is a hormone involved in regulation of blood glucose concentration
- Insulin needs to be soluble since hormones are transported via the blood stream
- Insulin needs to have a precise shape since hormones have to fit into specific receptors on the cell membrane
What is a conjugated protein ?
They are globular proteins that contain a non-protein component called a prosthetic group
Name examples of conjugated proteins ?
- Haemoglobin
- Catalase
Explain how haemoglobin’s structure as a conjugated protein aids its function ?
- Haemoglobin is the red, oxygen-carrying pigment in red blood cells
- It is made up of 4 polypeptides which each contain a heat group ( molecule contains Fe2+ )
- Each Fe2+ ion can combine with an oxygen molecule to oxyhemoglobin and transport oxygen around the body
Explain how catalase’s structure as a conjugated protein aids its function ?
- Catalase is an enzyme which speeds up the breakdown of hydrogen peroxide ( common byproduct of metabolic reactions that is damaging to cells )
- It contains 4 haem groups
- Fe2+ ions allow catalase to interact with and increase the rate of the break down of hydrogen peroxide
What are the features of fibrous proteins ?
- Strands/ fibres
- Insoluble in water
Name examples of fibrous proteins ?
- Keratin
- Elastin
- Collagen
Explain how keratin’s structure as a fibrous protein aids its function ?
- Keratin is a group of fibrous proteins present in hair, skin and nails
- The degree of disulphide bonds determines the flexibility
Explain how elastin’s structure as a fibrous protein aids its function ?
- Elastin is a fibrous protein found in elastic fibres ( in walls of blood vessels / alveoli in lungs )
- It allows structures flexibility and to expand/ return to normal size when needed
Explain how collagen’s structure as a fibrous protein aids its function ?
- Collagen is a fibrous protein which is connective tissue found in skin, tendons, ligaments and nervous system
- Collagen has flexibility due to it being a fibrous protein
Name the test for the presence of proteins in a sample ?
Biuret test
Describe the test for the presence of proteins in a sample ?
1 ) Add equal volume of Biuret solution to sample
2 ) Note colour change
What is the positive and negative test for the presence of proteins ?
- If it changes from light blue to purple/ violet then proteins are present
- If there is no change it is negative
Explain why using Biuret solution tests for the presence of proteins ?
- Peptide bonds forma violet precipitate with Cu2+ ions
- Therefore, when proteins are present they forma violet precipitate with Biuret solution ( NaOH and hydrated CUSOv4 )
What can be used to separate and identify the amino acids in a mixture ?
Thin layer chromatography
What is the mobile and stationary phase in the TLC of amino acids ?
- Stationarity phase = silica gel
- Mobile phase = organic solvent
What is the equation for Rf value ?
Rf = ( distance travelled by spot ) / ( distance travelled by solvent front )
What are the key inorganic cations involved in biological processes ?
- Ca2+
- Na+
- K+
- H+
- NHv4+
What are the key inorganic anions involved in biological processes ?
- NOv3-
- POv4-3
- OH-
- Cl-
- H-
- HCOv3-
