Biology Key words
Looking at cells Learning objectives: • describe the structure of eukaryotic cells • explain how the main sub-cellular structures are related to their functions.
chlorophyll chloroplast chromosome DNA eukaryotic order of magnitude
Cell biology helps us to understand how parts of the cell function and interact with each other. It also helps us to learn how we develop, and about our relationships with other organisms. Biomedical scientists use cells to look for signs of disease and in new drug development.
Plant and animal cells Almost all organisms are made up of cells. Plant and animal cells have a basic structure.
The vacuole: • is surrounded by a membrane and fluid filled • the fluid is called cell sap • vacuoles are permanent structures in plants. The nucleus: • controls the activities of the cell • contains deoxyribonucleic acid (DNA) • the DNA is organised into chromosomes. The cell membrane: • controls the passage of substances into and cut of the cell. The cytoplasm: • is where most of the chemical reactions in the cell take place.
(a)
The chloroplasts: • are found in plant cells above ground • contain chlorophyll that absorbs the light the plant needs for photoynthesis. The cell wall: • is an additional layer outside the cell membrane • is made from cellulose fibres contains fibres that provide • strength • unlike the cell membrane, does not regulate what enters or leaves the cell.
(b)
Figure 1.1 (a) A simple animal cell and (b) a plant leaf cell
This type of cell, containing a true nucleus in the cytoplasm, is called a eukaryotic cell. 1
List the sub-cellular structures found in both plant and animal cells.
2
Which sub-cellular structures are found only in plant cells? What is the function of: • the nucleus • the cell membrane?
3
14
What structure gives strength to a plant cell?
Figure 1.2 Growing cells in a laboratory
AQA GCSE Biology for Combined Science: Trilogy: Student Book
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