Date | May 2022 | Marks available | 4 | Reference code | 22M.2.HL.TZ2.6 |
Level | Higher level | Paper | Paper 2 | Time zone | Time zone 2 |
Command term | Outline | Question number | 6 | Adapted from | N/A |
Question
Describe how plants transport organic compounds from where they are made to where they are stored.
The processes of photosynthesis and respiration have some factors in common and others differ. Compare and contrast both processes for specific factors.
Humans rely on carbohydrates for much of their energy. Outline the process of digestion and absorption of starch in the human digestive system.
Markscheme
- (overall) process is translocation / bidirectional / movement from source to sink;
- sugars/sucrose/organic compounds produced in leaves;
- (loaded by) active transport / passage by apoplast route;
- loaded into companion cells / transported in phloem / sieve tubes;
- high concentrations of solutes at the source cause uptake of water (by osmosis);
- water provides hydrostatic pressure for transport (from source to sink);
- unloaded / stored / used at sink;
- lowers pressure at sink / creates pressure differential / water re-entry to xylem;
- salivary amylase breaks down starch in the mouth
OR
pancreatic amylase breaks down starch in small intestine; - product is disaccharides / maltose;
- maltase digest disaccharides into monosaccharides / glucose / simple sugars;
- monosaccharides/glucose absorbed in the small intestine;
- villi increase the surface area of the intestinal epithelium for greater absorption;
- (monosaccharides are) absorbed by co-transport/active transport (into intestinal cell) / absorbed byfacilitated diffusion into blood (from intestinal cell);
Do not accept glucose or sugars for mpb.
Examiners report
Question 6 was the least popular in section B.
Most candidates provided correct and complete details of the process of translocation.
The comparison of the processes of cellular respiration and photosynthesis was done effectively. Some very good and well-organized answers were noted. It was common for students to use a table to organize their answers. Some correct answers contained full descriptions of the Calvin and the Krebs cycle, which was unnecessary.
Most candidates presented full and correct answers regarding the enzymes and molecules involved in starch digestion. The main recommendation here was to watch the accuracy of statements.