Cell Biology
Cell Biology tests cell theory, prokaryotic and eukaryotic cells, plant and animal cell differences, organelles and cell division. Questions often ask you to identify a structure from its function or compare two cell types.
Core rules
- Cells are the basic structural and functional units of life. Prokaryotic cells lack a true nucleus and membrane-bound organelles; eukaryotic cells have a nucleus and organelles.
- Nucleus contains genetic material and controls cell activities. Mitochondria release energy through respiration. Chloroplasts carry out photosynthesis in plant cells.
- Ribosomes make proteins; endoplasmic reticulum transports materials; Golgi apparatus packages and modifies materials; lysosomes digest waste; vacuoles store substances.
- Plant cells have a cell wall, chloroplasts and a large central vacuole. Animal cells lack a cell wall and chloroplasts and usually have small vacuoles.
- Mitosis produces identical body cells for growth and repair; meiosis produces gametes with half the chromosome number.
Worked example
A student compares onion peel cells with human cheek cells. Onion peel cells are plant cells, so they show a rigid cell wall, a large central vacuole and chloroplasts in green parts. Cheek cells are animal cells, so they lack a cell wall and chloroplasts and have an irregular flexible shape. Both have a nucleus, cell membrane, cytoplasm and mitochondria. The reasoning is to compare shared structures first, then list cell-type-specific structures.
Traps
Prokaryotes do have genetic material, but not a membrane-bound nucleus. Mitochondria are in both plant and animal cells. A cell wall is not the same as a cell membrane. Chloroplasts are not present in all plant cells, such as root cells. Meiosis halves chromosome number; mitosis does not.