A Level Biology Ocr A Study Guide Graded A+

How is a dissacharide formed? {Ans: Two monosaccharides join in condensation reaction forming a 1-4 glycosidic bond}What are the features of alveoli? {Ans: One cell thick Made of squamous epithelium Many alveoli for large surface area Small - large SA:V Surfactant to prevent collapse}What are the three water transport pathways? {Ans: Vacuolar pathway Apoplast pathway Symplast pathway}What are three types of lipids? {Ans: triglycerides, phospholipids, steroids (e.g. cholesterol)}How do you test for a non-reducing sugar? {Ans: Add acid (to hydrolyse glycosidic bond) and heat Then neutralise with sodium bicarbonate Add benedict's reagent and heat (and centrifuge). It will go (blue to) brick red}What is the cambium? {Ans: Lateral meristem, differentiates into phloem, xylem, parenchyma}What is a countercurrent exchange system? {Ans: A mechanism by which the effiency of exchange between two substances is increased by them flowing in opposite directions.}What is the sink? {Ans: Where sugars are used/unloaded e.g. roots (ATP) buds}What is a non-competitive inhibitor? {Ans: An inhibitor that binds to the allosteric site and causes a conformational change to the enzyme}How is fetal haemoglobin different to adult haemoglobin? {Ans: It has a higher affinity for oxygen at lower partial