Topic 1: Cells Flashcards
What are the three statements of cell theory?
- All organisms are composed of one or more cells.
- Cells are the smallest units of life.
- All cells come from pre-existing cells.
What are the functions of life?
Metabolism, growth, reproduction, homeostasis, nutrition, excretion, responses.
Define metabolism.
Chemical reactions in an organism where energy is converted from one form to another.
Define growth.
When the cell will grow. This may be limited in certain cells, but will always occur.
Define reproduction.
When hereditary molecules found in cells are passed on to the offspring cells.
Define a response.
These are a cells response to specific stimuli (i.e, a reaction to light). It is essential for survival and helps the cell to adapt to an environment.
Define homeostasis.
This is the maintenance of a constant internal environment of the cell. For example, when the cell membrane will maintain a specific state of the cell by allowing specific materials to enter the cell.
Define nutrition.
The cell is provided with a source of compounds (chemical bonds), which are broken down to provide the cell with energy.
Define excretion.
The cell membrane will push out waste (toxic and useless chemicals) to be pushed out of the cell.
What is the ratio of surface area to volume?
It is the ratio of the cells total area to the volume of the cell itself. The higher this ratio (i.e 10:1), the better.
Why is a bigger ratio typically better for a cell?
A bigger ratio increases efficiency of the cell. Nutrients are moved faster to each part of the cell in a larger ratio cell, and there is more membrane (centimeters squared) which can service the volume of the cell (centimeters cubed). Additionally, if there the membrane is stretched too thin across the cell, waste can accumulate causing a big inefficiency of the cell. In a bigger cell, the metabolism can also generate more heat than the cell is capable of losing, resulting in the cell overheating.
When is it better to have a smaller SA:V ratio?
It is better to have a small SA:V ratio when conserving heat. For example, when it’s cold, in bigger mammals, they will lose heat much quicker, or the energy that was metabolised from the food they ate. This means they have to eat more to sustain themselves as heat is being lost at a quicker rate.
What is differentiation/specialization?
This is the process of a stem cell having it’s specific genes activated, which allows it to perform specific functions within the organism. Specializing may mean the cell can lose functionality (i.e, reproduction in nerve cells).
What is an emergent property?
An emergent property are new properties which result of differentiation, which will come together when cells create a new organism. Essentially, it proves that the whole is more than the sum. For example, a person is more than the organs which creates it.
What is a stem cell and why is there debate around it?
A stem cell is a “new” cell which has not yet been differentiated, i.e has the potential to become a cell for any organism. The reason there is debate around it is because scientists have found that one can use stem cells to repair damaged organisms, but obtaining stem cells requires the death of an embryo. There are two debates here, infused into one; abortion for scientific purposes.
