HL IB Biology Cell Specialisation

Stem Cell

A cell capable of unlimited division and differentiation into specialized cells

Stem Cell Niche

Specific location in the body where stem cells remain after differentiation

Totipotency

Stem cells that can differentiate into any cell type in an embryo

Pluripotency

Embryonic stem cells that can differentiate into any cell type in an embryo

Multipotency

Adult stem cells that can differentiate into closely related cell types

Unipotency

Adult cells that can only differentiate into their own lineage

Cell Specialisation

Process where eukaryotic cells become specialized for specific functions

Differentiation

Process by which cells develop specific adaptations for their roles

Structural Adaptations

Specific changes in cell structure to help carry out specialized functions

Cell Size Variation

Different cell sizes during differentiation to efficiently carry out functions

Red Blood Cells

Small cells adapted for movement through narrow capillaries

White Blood Cells

Larger cells with space for protein synthesis and antibody production

Sperm Cells

Long cells with streamlined heads for movement towards egg cells

Egg Cells

Cells with large volume for storing food reserves

Nerve Cells

Cells with large cell bodies for protein synthesis and rapid impulse delivery

Muscle Cells

Larger cells designed for exerting force during muscle contraction

Surface area to volume ratio

Ratio of cell surface area to its volume; crucial for metabolic reactions

Metabolic requirements

Materials exchanged across plasma membrane for cell survival

Single-celled organisms

Organisms with high SA:V ratio; survive by simple diffusion

Multicellular organisms

Organisms with adaptations for internal-external substance exchange

Exchange with environment

Substance exchange at cell surface for survival

Diffusion distance

Distance substances travel within a cell for metabolic reactions

Growth limitations

Cells stop growing when SA:V ratio is too small for survival

Models in science

Simplified representations for experimentation and explanation

Agar cubes experiment

Method to study ion diffusion based on surface area to volume ratio

Rate of metabolism

Dependent on cell mass or volume

Rate of exchange

Dependent on cell surface area

Red blood cells adaptation

Biconcave shape maximizes surface area for oxygen absorption

Proximal convoluted tubule cells

Cells requiring maximized surface area for substance movement

Proximal Convoluted Tubules

Tiny tubes in the kidney responsible for reabsorption of vital substances

Microvilli

Cell membrane feature in proximal tubule cells to increase surface area

Invaginations

Basal membrane infoldings in proximal tubule cells for increased surface area

Alveoli

Millions in lungs for gas exchange, with thin walls for short diffusion distance

Type I Pneumocytes

Thin alveolar cells maximizing gas exchange with short diffusion distance

Type II Pneumocytes

Alveolar cells producing surfactant to reduce surface tension

Pulmonary Surfactant

Solution with hydrophobic tails reducing alveolar surface tension

Skeletal Muscle Fibers

Striated muscle cells with contractile proteins, myofibrils, and T-tubules

Cardiac Muscle

Specialized striated muscle in the heart, myogenic and fatigue-resistant