3.5 - Lipids and Proteins Flashcards
What make up triglycerides?
Fatty acid and glycerol molecules
Describe the structure and function of cholesterol
• steroid structure of 4 hydrocarbon rings
• hydrocarbon tail on one side hydroxyl group on the other side
• adds stability to cell surface phospholipid bilateral by connecting molecules and reducing fluidity
• molecules of cholesterol are synthesised in the liver and transported via the blood
• acts as a barrier fitting in spaces between phospholipids- prevents water soluble substances from diffusing across the membrane
What’s the general structure of an amino acid?
- COOH carboxyl/ carboxylic acid group
- R variable side groups consists of carbon chain and may include other functional groups
- amine group
How do polypeptides form?
Condensation reactions between amino acids form peptide bonds
What are lipids ?
•They’re macromolecules that contain C,H and O atoms
• non polar and hydrophobic
What is glycerol?
an alcohol that contains a OH group bonded to a carbon atom
What are fatty acids?
• contain a methyl group at one end of a hydrocarbon chain known as a R group and a carbonyl group at another end
Name 2 ways a fatty acid Can vary
- Length of the hydrocarbon chain (R group )
- The fatty acid chain may be saturated or unsaturated
How are triglycerides formed?
By esterification
How does a ester bond form?
When the hydroxyl group from the glycerol bonds react with the carboxyl group of the fatty acids
What type of reaction is a formation of a ester bond?
Condensation reaction
Define primary structure of a protein
Sequence, number & type of amino acids in the polypeptide determines by the sequence of codons on mRNA
Define the secondary structure of a protein
Hydrogen bonds form between O delta negative attached to C=O and H delta positive attached to -NH
Describe the 2 types of secondary protein structure
• alpha helix
- all N-H bonds on the same side of protein chain
- spiral shape
- H- binds parallel to helical axis
• beta pleated sheet
- N-H & C=O groups alternate from one side to the other
In what circumstance does the secondary structure occur ?
Occurs when weak negatively charged nitrogen and oxygen atom’s interact with weak positively charged hydrogen atoms to form hydrogen bonds
Describe the tertiary structure of a protein and describe the bonds present
3D structure formed by further folding
Disulfude bonds - string covalent S-S bonds between molecules acid Cysteine
Ionic bonds- relatively strong bonds between charged R groups
Hydrogen bonds - numerous and easily broken
Define quaternary structure of a protein
• functional proteins may consist of more than one polypeptide
• precise 3D structure held together by the same types of bond as tertiary structure
• may involve the addition of prosthetic groups eg. Metal ions or phosphate groups
Define the structure and function of globular proteins
• compact, circular shape, soluble in water
• hydrophilic R groups face outwards and hydrophobic R groups face inwards = usually water soluble
• involved in metabolic processes eg. Enzymes such as amylase , insulin and haemoglobin
Describe the structure of haemoglobin
• quaternary structure = 4 polypeptide chains
• 2 alpha chains , 2 beta chains and 4 prosthetic haem groups
• these chains are subunits are globular proteins and each subunit has a prosthetic haem group
• these 4 globin subunits are held together by disulphide bonds and are arranged so that their hydrophobic R groups are facing outwards- helping maintain its solubility
• prosthetic haem group contains iron ( iI) which reversible combines with an oxygen molecule forming an oxyhemoglobin and results in the haemoglobin appearing bright red
Describe the structure and function of fibrous proteins
• long strands of polypeptide chains that have cross linkages due to hydrogen bonds
• due to large number of hydrophobic R groups they’re insoluble in water
• useful for structure and support eg. Collagen in skin
What is the function of collagen?
Component of bones , cartilage, connective tissues and tendon’s
What’s the function of elastin?
Provides elasticity to connective tissue , arteries, skin , lungs , cartilage, ligaments
What’s the function of keratin?
Structural component of hair, nails, epithelial cells of outer layer of skin
