Cell Theory 1.1

Question 1

What is the cell theory?

Answer 1

1. Cells are the smallest poissible units of life
2. All living organisms are made of cells
3. All cells come from pre-existing cells

Question 2

What are the exceptions to the cell theory?

Answer 2

1. Skeletal muscle
   - made up of muscle fibres
   - fibres are enclosed inside a membrane
   - they are mushc larger than most cells (300mm < long)
   - contain hundreds of nuclei
2. GIant algae
   - Acetabularia can grow to a lendth of 100mm
   - only contain a single nucleus
   - not multicellular
3. Aseptate fungi
   - consist of thread-like structures called hyphae
   - hyphae is not divided into sub-units containing a single nucleus
   - they are long undivided sectins of hypha that contain many nuclei

Question 3

What are the functions of life?

Answer 3

Metabolism 
Reproduction 
Sensitivity 
Homeostasis 
Excretion 
Growth 
Nutrition

Question 4

What is the SA:Vol ratio and why is it important in cell size limitations?

Answer 4

Cells need to exchange materials w/ the environment to produce chemical energy for survival (via metabolism)

• the rate of metabolism is a function of a cells mass/volume
• the rate of material exchange is a function of a cells surface area

As a cell grows, volume increases faster than Surface area.

• if metabolic requirements exceed material exchange, the cell will die
• therefore they must stay small or increase their SA:Vol ratio to survive

Small SA:Vol: 
- high metabolic rates 
- low material exchange 
- low chance of survival 
High SA:Vol:
- low metabolic rate 
- high material exchange 
- high chance of survival