Biology – Cell structures (B1.1)
Looking at cells
KEY WORDS
Learning objectives: • •
describe the structure of eukaryotic cells explain how the main sub-cellular structures are related to their functions.
chloroplast chlorophyll chromosome 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. Cells are the fundamental units of living organisms. Plant and animal cells have a basic structure. The nucleus: • controls the activities of the cell • contains deoxyribonucleic acid (DNA) • the DNA is organised into chromosomes. The cell membrane: • is a selective barrier that controls the passage of substances into and out of the cell • contains receptor molecules.
The cytoplasm: • is where most of the chemical reactions in the cell take place. (b)
(a)
Figure 1.4 (a) A simple animal cell and (b) a plant leaf cell
The vacuole: • surrounded by a membrane and fluid filled • the fluid is called cell sap • vacuoles are permanent structures in plants. The chloroplasts: • are found in plant cells above ground • contain chlorophyll that absorbs the light the plant needs for photosynthesis. The cell wall: • is an additional layer outside the cell membrane • made from cellulose fibres • contains fibres that provide strength • unlike the cell membrane, does not regulate what enters or leaves the 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
16
What structure gives strength to a plant cell?
OCR Gateway GCSE Biology: Student Book
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