Classes of Organic Molecules (Proteins, Lipids and Nucleic Acids) Flashcards
state 2 basic facts about lipids as a whole
- lipids are bonded by a non-polar covalent bond
2. lipids have a very low solubility in water
what percentage of organic matter in the body do lipids around for and what percentage of bodyweight is made up of lipids
- lipids account for 40% organic matter in the body
2. lipids account for 15% of human body weight
what are the 4 ways in which lipids can be organised
fatty acids, phospholipids, triglycerides and steroids
what is the structure of a fatty acid
fatty acids are long chains made up of carbon and hydrogen atoms with an acidic carboxyl group at one end
explain what it is meant by ‘cis unsaturated’ fats
most naturally occurring unsaturated fatty acids occur in the cis position with both hydrogens occurring on the same side of the double carbon to carbon bond
explain what it is meant by ‘trans unsaturated’ fats
trans fatty acids can be made by modifying cis unsaturated fatty acids so both hydrogen atoms are on opposing sides of the double carbon to carbon bond
state 2 facts about trans unsaturated fats
- trans configuration adds stability to food, as well as longer storage and also alters the foods consistency
- trans unsaturated fatty acids have been linked with a number of health conditions - for example, elevated blood cholesterol concentration
define what it is meant by the key term ‘eicosanoids’
Eicosanoids are modified fatty acids - derived from the 20 carbon long fatty acid arachidonic - which regulate a number of cell functions by acting as cell signal molecules
state 4 facts about triglycerides
- the majority of lipids in the human body are triglycerides
- formed when glycerol, a 3 carbon sugar alcohol, binds to 3 fatty acid chains
- hydroxyl groups in glycerol bind to carboxyl groups in fatty acids via a condensation reaction forming an ester bond
- animal fatty acids tend to be more saturated and plant fatty acids tend to be more unsaturated
how can triglycerides be used
- stored in adipose tissue
- broken down via hydrolysis reactions
- fatty acids transported in blood to tissue
- cells metabolise fatty acids to re-synthesis ATP
explain the structure of a phospholipid
the third hydroxyl group in the cholesterol is bonded to a phosphate group, instead of a third fatty acid chain, which has a small, polar, nitrogen attached to the phosphate group
explain the importance of phospholipids on an general basis
as phospholipids are amphipathic, they form clusters in water with hydrophilic (polar) heads facing outwards and hydrophobic (non-polar) tails facing inwards
state 2 facts about steroids
- steroids are formed by interconnected rings of carbon atoms
- a few polar hydroxyl groups may be attracted to this ring structure, but aren’t numerous enough to make a steroid water soluble
give 4 examples of steroids
cholesterol, cortisol, oestrogen and testosterone
explain two features of the structure of amino acids
- each amino acid, excluding proline, has an amine group and a carboxyl group bound to the terminal carbon in the middle of the molecule
- side chains may be polar but not ionised (7 amino acids), polar and ionised (5 amino acids) or non-polar (8 amino acids)
how do amino acids bond together
condensation reactions between the carboxyl group of one amino acid and the amine group of another amino acid forms a peptide bond between two amino acids plus a water molecule
define what it is meant by the key term ‘peptide’
a peptide is a functional polypeptide with 50, or fewer, amino acids in the chain and has a known biological function
what are the two variables which determine the primary structure of a protein
- the number of amino acids in the polypeptide chain
2. the type of amino acids at each point along the polypeptide chain
what is the scientific reason between the secondary structure of a protein
interactions between side groups (of amino acids) leads to bonding, twisting and folding of the polypeptide chain into a more compact structure and forms something called a conformation
explain the concept of an ‘Alpha Helix’
an alpha helix occurs because peptide bonds form at regular intervals along a polypeptide chain. the H-bonds between them tend to force the chain into a coiled conformation known as a double helix
explain the concept of ‘beta pleated sheets’
beta pleated sheets occur because H-bonds also form between peptide bonds when extended regions of a polypeptide chain run approximately parallel to each other forming a relatively straight and extended region called a beta pleated sheet
explain the concept of a ‘random coil conformation’
a random coil conformation occurs when a given region of a polypeptide chain may not assume either an alpha helix or beta pleated sheet and so are called random coil conformations
explain the reasons for alpha helixes and beta pleated sheets
alpha helices and beta pleated sheets import stability to a protein to allow it to anchor onto a lipid bilayer due to the hydrophobic side chains in amino acids making them more likely to remain in lipid environments
what enables a tertiary structure of a protein to form
because the secondary structure has folded the polypeptide up more, more interactions between more amino acids can take place
