Theory question 101
Photosynthesis and Plant Nutrition(a) (i) Name the two stages involved in photosynthesis (ii) Write an equation to represent the first stage of photosynthesis
(b) (i) List six modes of nutrition in organisms (ii) Name one feature that makes feeding possible in the following organisms I. Paramecium II. Spirogyra III. Rhizopus IV Tapeworm
(c) Define the term balanced diet
(d) (i) State three characteristics of enzymes. (ii) In a tabular form indicate the source, substrate acted upon and the product of the following enzymes: ptyalin, pepsin
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(a)(i) Light stage (light-dependent stage/photolysis); dark stage (light-independent stage/carbon dioxide fixation).
(ii) Light stage: water is split by light energy absorbed by chlorophyll: 2H2O → 4H+ + 4e− + O2 (or 4H2O → 4H+ + 4OH−).
(b)(i) Any six: autotrophic/holophytic (photosynthetic), chemosynthetic, holozoic, saprophytic, parasitic, symbiotic; also herbivorous, carnivorous, omnivorous.
(ii) Paramecium: cilia/oral groove/food vacuole. Spirogyra: chloroplast (chlorophyll). Rhizopus: hyphae/rhizoids that secrete enzymes and absorb. Tapeworm: thin flat body surface that absorbs digested food (suckers/hooks for attachment).
(c) A balanced diet contains all the food classes (carbohydrate, protein, fats and oils, vitamins, mineral salts, water and roughage) in the right amounts and proportions for the body's needs.
(d)(i) Any three: they are proteins; they speed up reactions (catalysts); they are specific; they are not used up; they work best at an optimum temperature and are destroyed by high heat; they work best at an optimum pH; small amounts work on large amounts of substrate; many reactions they catalyse are reversible.
(ii) Ptyalin: source mouth/salivary glands; substrate cooked starch; product maltose. Pepsin: source stomach/gastric glands; substrate proteins; product peptones/polypeptides.
Learn each enzyme as a set: where it is made, what it acts on and what it makes.