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Cell Size - PowerPoint PPT Presentation

Cell Size. Unit 3 Part 2 – The Cell. Why are cells small?. Why cells are small? Diffusion limits cell size DNA limits the cell size. Surface area-volume ratio. Diffusion Limits Cell Size.

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PowerPoint Slideshow about ' Cell Size' - anastacia-manella

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Presentation Transcript

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

• 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