IB Biology Topic B2.3.5 Cell Size as an Aspect of Specialization Revision Notes (SL/HL)

IB Biology Topic B2.3.5 Cell Size as an Aspect of Specialization Revision Notes (SL/HL) | RevisionDojo

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Cell Size Is Itself an Adaptation to a Cell's Job

Specialised cells differ enormously in size, from a red blood cell around 7 micrometres across to a motor neuron that can stretch nearly a metre.
A cell's size and shape are tuned to its function, so size is a genuine part of specialisation.
Cell sizes are measured in micrometres (µm), where one micrometre is a thousandth of a millimetre.

Analogy

A courier van and a bicycle both move goods, but each suits a different job.
The bicycle wins in tight lanes while the van carries far more cargo.
Cell size works the same way, matched to the task rather than chosen at random.

Size Is Set by the Job, Then Limited by Geometry

Small cells such as red blood cells squeeze through narrow capillaries to deliver oxygen.
Long cells such as motor neurons carry signals over long distances.
Large cells such as the egg cell (ovum) hold stored nutrients for a developing embryo.
How large a cell can get is limited by surface area-to-volume considerations, which are covered separately in B2.3.6.

Note

This topic is about how size fits function.
The full theory of why volume outgrows surface area belongs to B2.3.6.

Examples: Real Cells Span a Huge Size Range

Red Blood Cell: Small for Fast Gas Exchange

Size: about 7 µm in diameter.
The red blood cell (erythrocyte) transports oxygen around the body.
1. Its small biconcave shape gives a short path for oxygen to diffuse in and out.
2. Being small and flexible lets it bend through the narrowest capillaries.

Sperm Cell: Small and Streamlined for Speed

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Cell Size Is Itself an Adaptation to a Cell's Job

Specialised cells differ enormously in size, from a red blood cell around 7 micrometres across to a motor neuron that can stretch nearly a metre.
A cell's size and shape are tuned to its function, so size is a genuine part of specialisation.
Cell sizes are measured in micrometres (µm), where one micrometre is a thousandth of a millimetre.

Analogy

A courier van and a bicycle both move goods, but each suits a different job.
The bicycle wins in tight lanes while the van carries far more cargo.
Cell size works the same way, matched to the task rather than chosen at random.

Size Is Set by the Job, Then Limited by Geometry

Small cells such as red blood cells squeeze through narrow capillaries to deliver oxygen.
Long cells such as motor neurons carry signals over long distances.
Large cells such as the egg cell (ovum) hold stored nutrients for a developing embryo.
How large a cell can get is limited by surface area-to-volume considerations, which are covered separately in B2.3.6.

Note

This topic is about how size fits function.
The full theory of why volume outgrows surface area belongs to B2.3.6.

Examples: Real Cells Span a Huge Size Range

Red Blood Cell: Small for Fast Gas Exchange

Size: about 7 µm in diameter.
The red blood cell (erythrocyte) transports oxygen around the body.
1. Its small biconcave shape gives a short path for oxygen to diffuse in and out.
2. Being small and flexible lets it bend through the narrowest capillaries.

Sperm Cell: Small and Streamlined for Speed

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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

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Sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.
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A - Unity and Diversity9 subtopics

B - Form and Function10 subtopics

C - Interaction and Interdependence9 subtopics

D - Continuity and Change12 subtopics

IB Biology Topic B2.3.5: Cell Size as an Aspect of Specialization Notes

A - Unity and Diversity9 subtopics

B - Form and Function10 subtopics

C - Interaction and Interdependence9 subtopics

D - Continuity and Change12 subtopics

Cell Size Is Itself an Adaptation to a Cell's Job

Size Is Set by the Job, Then Limited by Geometry

Examples: Real Cells Span a Huge Size Range

Red Blood Cell: Small for Fast Gas Exchange

Sperm Cell: Small and Streamlined for Speed

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

Cell Size Is Itself an Adaptation to a Cell's Job

Size Is Set by the Job, Then Limited by Geometry

Examples: Real Cells Span a Huge Size Range

Red Blood Cell: Small for Fast Gas Exchange

Sperm Cell: Small and Streamlined for Speed

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