1.1. Cells Are The Basic Unit Of Life Flashcards
Define cell
The basic unit for all living organisms; it is surrounded by cell surface membrane and contains genetic material (DNA) and cytoplasm containing organelles
Define organelle
A functionally and structurally distinct
part of a cell.
All cells come from
Pre-existing cells by the process of cell division
Define nucleus
A relatively large organelle found in eukaryotic cells, but absent from prokaryotic cells. The nucleus contains cell’s DNA and therefore controls the activities of the cells.
What are the two fundamentally different types of cells?
Prokaryotic cells and eukaryotic cells
Describe prokaryotic cells
These cells are simpler with the DNA, not surrounded by any membranes, but free in the cytoplasm. They also don’t have any membrane bound organelles.
Describe eukaryotic cells
These cells are much larger and more complex and contain a nucleus surrounded by two membranes. The genetic material DNA is in the nucleus. They also have membrane bound organelles.
Eukaryotes are said to have evolved from prokaryotes ___________ years ago
More than 2 billion
Define eukaryotes
An organism whose cells contain a nucleus and other membrane bound organelles
Define prokaryotes
An organism whose cells do not contain a nucleus or other membrane bound organelles
Prokaryotes include
Bacteria
Eukaryotes include
Animals, plants, fungi and some other organisms.
A cell can be thought of as a bag in which
the chemistry of life takes place
The membrane is an essential feature of the cell because
It controls the exchange between cell and it’s environment
How does the cell surface membrane control the exchange between a cell and it’s environment
By acting as a barrier and controlling the movement of materials across the membrane in both directions.
The membrane is therefore partially permeable.
If the membrane were freely permeable, then why couldn’t life exist
Because the chemicals of the cell would simply mix with the surrounding chemicals by diffusion and inside of the cell would be the same as outside the cell. This means some vital conditions for reactions to take place such as a specific concentration of the solution and pH will not be present due the mixing of the chemicals from outside the cell with the chemicals from inside the cell.
