- 116 Views
- Uploaded on
- Presentation posted in: General

Cell Size

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Cell Size

Unit 3 Part 2 – The Cell

- Why cells are small?
- Diffusion limits cell size
- DNA limits the cell size.
- Surface area-volume ratio

- Diffusion is fast and efficient over short distances, it becomes slow and inefficient over larger distances.
- Small cell
- good diffusion

- Big cell
- bad diffusion

- Small cell

- Speed of Diffusion
- An organelle in the center of a 20μm diameter cell receives supplies a fraction of a second after it enters the cell.
- An organelle in the center of a 20 cm diameter cell would have to wait months before receiving supplies that enter the cell.

- The DNA tells the cell which proteins to be made.
- Not enough protein the cell will die. Take time for protein to be produced.
- As cells increase in size, no extra DNA is made

- As cell size increases, volume increases much faster than surface area.
- A 1mm cube has a surface area of 6mm2 and a volume of 1mm3. A 2mm cube has a surface area of 24mm2 and a volume of 8mm3

- The larger the volume of the cell, the smaller the surface area gets.

- Before a cell gets too large, it divides into two “daughter” cells.
- Before cell division takes place, the cell must replicate all of its DNA.
- The cell then divides and solves the problem of the cell becoming too large.

Cell size vs. surface area must remain at an efficient ratio

Growth - bigger organism needs more cells

Repair - regeneration of skin, blood & bone etc.

Reproduction - asexual vs sexual