Fig. 1.1 is a transmission electron micrograph showing a section of a human liver cell. [Figure 1.1]

Mark scheme

Marking points from the official mark scheme (Oct/Nov 2022). The mark or mark type is shown in brackets.

1. [2] (a)(i) A mitochondrion ;
2. B rough endoplasmic reticulum; A ribosome / 80S ribosome
3. [3] (a)(ii) any three from: (more efficient) synthesis / metabolism / AW, of named product; e.g. lipid/named lipid phospholipid steroid / steroid hormone / named, e.g. oestrogen / testosterone sterol/cholesterol I ref. to storage
4. other function; e.g. detoxification
5. max two from: idea that synthesis of products / AW, is a pathway / requires more than one enzyme ; further detail; e.g. enzymes of same pathway are, close together / in clusters products of one reaction are substrates of the next
6. suggestion that membrane gives enzymes, more stability / greater protection (from degradation);
7. AVP; e.g. idea of greater efficiency as enzyme held so that active site faces substrates in lumen suggestion that allows reactions to occur on cytoplasmic side of membrane suggestion that allows reaction to continue / complete, in SER transport vesicles
8. [3] (b) any three from: higher magnification (without loss of detail);
9. higher resolution / ability to see object that are close together as separate objects ;
10. ref. to resolution of (up to) 0.5 nm compared to, 200 nm / 0.2 µm (light microscope) ; A ranges, e.g. 0.5–30 nm and 100–300 nm
11. ability to see organelles such as, SER / ribosomes / other named organelle ;
12. AVP; e.g. very thin sections, qualified, e.g. for greater internal detail