IB Biology Topic B2.3.6 Surface Area-to-volume Ratios and Constraints on Cell Size Revision Notes (SL/HL)

IB Biology Topic B2.3.6 Surface Area-to-volume Ratios and Constraints on Cell Size Revision Notes (SL/HL) | RevisionDojo

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Surface Area-to-Volume Ratio: Why Cells Stay Small

Cells need to exchange materials such as nutrients, waste products, and gases through their cell membrane.
The surface area (SA) sets how much space is available for exchange.
The volume (V) sets how much material must be exchanged and how much waste is produced.
The rate of exchange across the surface must keep up with the metabolic demands of the volume.

Note

As a cell increases in size, its volume increases faster than its surface area.
This leads to a lower surface-area-to-volume ratio, making it harder for larger cells to exchange materials efficiently.

Calculating SA:V Ratios: The Maths Behind Cell Size

Surface Area (SA) of a Cube = 6 × (side length)², because a cube has six square faces.
Volume (V) of a Cube = (side length)³.

SA:V Ratio = Surface Area / Volume = 6 / side length

Worked Example: Cubes of Increasing Size

Small Cube (side = 1 unit)

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Surface Area-to-Volume Ratio: Why Cells Stay Small

Cells need to exchange materials such as nutrients, waste products, and gases through their cell membrane.
The surface area (SA) sets how much space is available for exchange.
The volume (V) sets how much material must be exchanged and how much waste is produced.
The rate of exchange across the surface must keep up with the metabolic demands of the volume.

Note

As a cell increases in size, its volume increases faster than its surface area.
This leads to a lower surface-area-to-volume ratio, making it harder for larger cells to exchange materials efficiently.

Calculating SA:V Ratios: The Maths Behind Cell Size

Surface Area (SA) of a Cube = 6 × (side length)², because a cube has six square faces.
Volume (V) of a Cube = (side length)³.

SA:V Ratio = Surface Area / Volume = 6 / side length

Worked Example: Cubes of Increasing Size

Small Cube (side = 1 unit)

Definition

Paywall

(on a website) an arrangement whereby access is restricted to users who have paid to subscribe to the site.

anim nostrud sit dolore minim proident quis fugiat velit et eiusmod nulla quis nulla mollit dolor sunt culpa aliqua

Duis aute irure dolor in reprehenderit

Note

Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam quis nostrud exercitation.

Excepteur sint occaecat cupidatat non proident

Tip

Lorem ipsum dolor sit amet, consectetur adipiscing elit.
Sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.
Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris.
Duis aute irure dolor in reprehenderit in voluptate velit esse cillum.

A - Unity and Diversity9 subtopics

B - Form and Function10 subtopics

C - Interaction and Interdependence9 subtopics

D - Continuity and Change12 subtopics

IB Biology Topic B2.3.6: Surface Area-to-volume Ratios and Constraints on Cell Size Notes

A - Unity and Diversity9 subtopics

B - Form and Function10 subtopics

C - Interaction and Interdependence9 subtopics

D - Continuity and Change12 subtopics

Surface Area-to-Volume Ratio: Why Cells Stay Small

Calculating SA:V Ratios: The Maths Behind Cell Size

Worked Example: Cubes of Increasing Size

anim nostrud sit dolore minim proident quis fugiat velit et eiusmod nulla quis nulla mollit dolor sunt culpa aliqua

Duis aute irure dolor in reprehenderit

Excepteur sint occaecat cupidatat non proident

Unlock the rest of this chapter with a free account

Surface Area-to-Volume Ratio: Why Cells Stay Small

Calculating SA:V Ratios: The Maths Behind Cell Size

Worked Example: Cubes of Increasing Size

anim nostrud sit dolore minim proident quis fugiat velit et eiusmod nulla quis nulla mollit dolor sunt culpa aliqua

Duis aute irure dolor in reprehenderit

Excepteur sint occaecat cupidatat non proident

Unlock the rest of this chapter with a free account