33 WJEC Biology AS Level - Marianne Izen - 2nd Edition Flashcards
What are all cells surrounded by?
All cells are surrounded by a membrane made of phospholipids and proteins.
Describe the appearance of biological membranes in light microscope and electron microscope.
Biological membranes are very thin.
Their structure cannot be distinguished in the light microscope
In the electron microscope, they appear as a single line.
What do eukaryotic cells contain?
Eukaryotic cells contain membrane-bound organelles, which are enclosed areas in the cytoplasm.
What is the advantage of having membrane-bound organelles?
- The advantage is that potentially harmful chemicals, such as enzymes, are isolated.
- Molecules with particular functions, such as chlorophyll, can be concentrated in one area.
- Membranes provide a large surface area for the attachment of enzymes involved in metabolic processes.
- They provide a transport system inside the cell.
When looking at images of cells, what is important to understand?
When looking at images of cells, it is important to understand the units of measurement.
What is the standard unit of measurement?
The standard unit of measurement is the metre (m).
When considering molecules, the unit of measurement used is —–
nanometres (nm)
When considering ecosystems, the unit of measurement used is —–
kilometres (km)
When considering cells and organelles, the unit of measurement used is —–
micrometres (um)
Organelle (Key Term)
A specialised structure with a specific function inside a cell.
What are the principles of cell theory?
The three principles of cell theory are:
- All living organisms are composed of one or more cells.
- The cell is the basic unit of life.
- Cells can only arise from pre-existing cells.
How has the concept of cells developed?
The concept of cells dates back to the 1660s and has developed as microscope technology and the chemistry of stains have advanced.
Draw and label the generalised structure of an animal cell.
Draw and label the generalised structure of a plant cell.
