Cell structures, plant and animal cells, and prokaryotes
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The teaching part (1 min) is free to watch. A free account opens the whole lecture: 4 practice questions, 2 real past-paper questions with the answers explained, the mistakes that lose marks, the full-marks tip, a one-card summary and a quick quiz.
What this lecture covers
- A factory in a bag
- The nucleus
- Mitochondria and ribosomes
- The protein route
Read the transcript of the teaching part
A factory in a bag
Think of a cell as a small factory. It has a manager, power stations, production lines, a packing department and a security wall. Each structure has one job, and exam questions ask you to match structure to function, and to compare cells.
The nucleus
The nucleus holds the DNA, which carries the instructions for making proteins. It is surrounded by a double membrane called the nuclear envelope. The nuclear pores let messenger RNA out, and let proteins in. The nucleolus inside makes ribosomal RNA and builds ribosomes.
Mitochondria and ribosomes
Mitochondria are where aerobic respiration releases energy as ATP. They have a double membrane, with the inner one folded into cristae. They contain their own small circular DNA and 70S ribosomes. Ribosomes make proteins. Eukaryotic cells have 80S ribosomes, which are bigger than the 70S ribosomes of prokaryotes.
The protein route
Rough endoplasmic reticulum has ribosomes on it. It makes proteins and folds them. Smooth endoplasmic reticulum makes lipids and steroids. It has no ribosomes. The Golgi body modifies and packages proteins, and sends them off in vesicles. Some vesicles become lysosomes, which hold digestive enzymes.
How often it comes up
How often Cambridge has asked each part, counted by ExamYard from every past paper in its question bank: Cell structures and their functions · Prokaryotic and eukaryotic cells · Cell structures and their functions · Prokaryotic and eukaryotic cells.
The whole chapter: Cell Structure, Cell Structure.
Chapter 1: Cell structure
- Microscopy: resolution, magnification and graticules 7 min
- Cell structures, plant and animal cells, and prokaryotes 5 min
- The secretory pathway and viruses 6 min
Also for A Level Biology 9700
Which topics come up most in A Level Biology 9700 past papers, counted from every paper since 2004: Paper 1 topic frequency, Paper 2 topic frequency, Paper 4 topic frequency.