Module 2: Biological Molecules Flashcards

Question

The tertiary structure is maintained by different bonds

Answer 1

1) Disulfide bonds- The amino acid cysteine contains sulfur. Where two cysteines are found close to each other a covalent bond can form. 2) Ionic bonds- R groups sometimes carry a charge. Where oppositely charged amino acids are found close together an ionic bond forms. 3) Hydrogen bonds- Where slightly positive groups are found close to slightly negative groups, hydrogen bonds form. 4) Hydrophobic and hydrophilic interactions in a water-based environment, hydrophobic amino acids will be most stable if they are held together with water excluded. Hydrophilic amino acids tend to be found on the outside of globular proteins, with hydrophilic in the centre.

Answer 2

Globular proteins have molecules of a spherical shape. Any hydrophobic R groups are turned inwards towards the centre of the molecule, while hydrophilic groups are on the outside. This makes the protein soluble in water, because water can easily cluster around them and bind to them. They often have very specific shapes, which helps them to take up roles as enzymes, hormones and haemoglobin. Fibrous proteins has a long, thin structure and are usually insoluble in water and metabolically inactive, often having a structural role in an organism. Examples include collagen, elastin and keratin.

Answer 3

Heat energy gives molecules kinetic energy. Kinetic energy makes molecules vibrate and can break bonds. Heating proteins can break the bonds holding their tertiary structure in place ‐ this changes the shape of the protein. This is called denaturing. The shape of a protein is vital to its function so once the bonds are broken and its tertiary structure is lost, the protein will no longer function properly. (Colvalent bonds are very strong so need more heat energy to break them).

Answer 4

Haemoglobin has a quaternary structure with 4 subunits ‐ 2 α‐chains and 2 β‐chains each with a prosthetic (non amino acid) haem group. primary structure: sequence range of amino acids secondary structure: mostly alpha helices tertiary structure: alpha chains and beta chains quaternary structure: 2 alpha and 2 beta chains

Answer 5

Collagen molecules' quaternary structure are made up of 3 polypeptide chains tightly wound around each other ‐ hydrogen bonds between them gives the molecule strength. Every 3rd amino acid on each polypeptide chain is a glycine. These are small and allow close packing. Covalent bonds cross link parallel collagen molecules. This forms a collagen fibril. The ends of molecules and covalent bonds are staggered to add strength. Many fibrils form a collagen fibre.

Answer 6

* lines arterial walls ‐ prevents blood at high pressure bursting walls * tendons ‐ all muscles to pull bone for movement * bones ‐ collagen reinforced with other materials to make them hard * cartilage and connective tissue * cosmetic treatments ‐ collagen injections can make lips look fuller. Properties for function: - High tensile strength - Not elastic - Flexible - Insoluble

Answer 7

A lipid dissolves in organic solvents (alcohol) but not water. They include triglycerides, phospholipids, glycolipids, cholesterol. Solid lipid= fat Liquid lipid= oil

Answer 8

* Energy source * Energy store ‐ lipids stored in adipose cells * Phospholipid bilayers * Thermal insulation * Myelin sheath of neurones ‐ electrical insulation * Steroid hormones * Waxy cuticle of leaves ‐ prevents drying out

Answer 9

Triglycerides are made up of glycerol and fatty acids. Glycerol has 3 carbons and has free -OH groups , which are important to the structure of triglycerides. Fatty acids have a carboxyl group (-COOH) on one end, attached to a hydrocarbon tail made of only carbon and hydrogen atoms. This may be anything from 2-20 carbons long.

Answer 10

If a fatty acid is saturated this means that there are no C=C bonds in the molecule. If a fatty acid is unsaturated, there is a C=C bond between two f the carbons, which means fewer hydrogen atoms can be bonded to the molecule. A single C=C make the fatty acid monounsaturated. - Oleic acid More than one C=C bond makes it polyunsaturated. - Linoleic acid Having one or more C=C bonds changes the shape of the hydrocarbon chain, giving it a kink where the double bond is. Because these kinks push the molecules apart slightly, it makes them more fluid.