Cell Biology, Tissues, and Life Processes
This domain tests cell structure and organelles, the difference between plant and animal cells, plant and animal tissues, and the life processes of nutrition, respiration, transport, and excretion.
Core rules
- The cell is the basic structural and functional unit of life. Prokaryotic cells lack a membrane-bound nucleus; eukaryotic cells have one.
- Key organelles: nucleus controls activity and contains DNA; mitochondria release energy by respiration; chloroplasts carry out photosynthesis; ribosomes make proteins; vacuoles store substances; the cell membrane controls exchange.
- Plant cells have a cell wall, a large central vacuole, and often chloroplasts. Animal cells lack a cell wall and chloroplasts and usually have small vacuoles.
- Plant tissues include meristematic tissue for growth and permanent tissues such as parenchyma, collenchyma, and sclerenchyma. Life processes include autotrophic and heterotrophic nutrition, aerobic and anaerobic respiration, transport through xylem and phloem, and excretion.
Worked example
A student observes a cell with a rigid outer layer, a large central vacuole, and green structures. Identify the cell. The rigid layer is a cell wall, the large vacuole is typical of a mature plant cell, and the green structures are chloroplasts. The cell is a plant cell, likely from a leaf. The presence of chloroplasts also indicates that photosynthesis can occur.
Traps that cost marks
Do not say plant cells have no mitochondria; they respire too. Do not confuse the cell wall with the cell membrane. Do not state that respiration occurs only in animals. Remember that xylem transports water and minerals mainly upward, while phloem transports food.
Key points
- Cells are the basic unit of life; organelles have specific roles.
- Plant cells have a cell wall, large vacuole, and often chloroplasts.
- Xylem transports water; phloem transports food.
- Respiration occurs in both plants and animals.