In all cases involving the purchases of supplies, materials and equipment, or in cases involving construction work to be done by contract, or the purchase of personal property of any kind, where state statute requires competitive bidding, unless the council shall by an emergency ordinance otherwise provide, the city shall advertise for bids in such manner as may be designated by the council. Contracts entered into pursuant to such bids shall be let by the council only to the lowest responsible bidder. The council may, however, reject any and all bids. Nothing contained in this section shall prevent the council from contracting by a two-thirds vote for the doing of work with patented processes, or from the purchasing of patented appliances by the same majority. Subject to the provisions of this Charter, the council may by ordinance adopt further regulations for the making of bids and the letting of contracts.