IB Biology HL - B2.3: Cell Specialization

Stem Cells

Undifferentiated cells that can divide indefinitely.

Zygote

Single, unspecialized cell formed after fertilization.

Differentiation

Process of unspecialized cells becoming specialized.

Morphogens

Signaling molecules influencing gene expression and cell fate.

Cell Specialization

Cells perform specific functions with increased efficiency.

Self-Renewal

Stem cells can divide without limit.

Potency

Ability of stem cells to differentiate into specialized cells.

Stem Cell Niche

Microenvironment regulating stem cell behavior.

Hematopoietic Stem Cells

Produce blood cells in bone marrow.

Epithelial Stem Cells

Regenerate from hair follicle bulge.

Totipotent Stem Cells

Can become any cell type, e.g., zygote.

Pluripotent Stem Cells

Can become any body cell except placenta.

Multipotent Stem Cells

Can become a limited range of cell types.

Blastocyst

Early embryo stage with pluripotent stem cells.

Ectoderm

Germ layer forming skin and nervous system.

Mesoderm

Germ layer forming muscles and internal organs.

Endoderm

Germ layer forming digestive and respiratory systems.

Surface Area-to-Volume Ratio

Measurement affecting cell size and efficiency.

Cell Size Constraints

Limits on cell size due to surface area.

Adaptations for Surface Area

Changes to increase surface area-to-volume ratios.

Embryonic Development

Process where cells specialize as the fetus forms.

Specialized Functions

Unique roles cells perform based on their structure.

Gene Expression

Process by which information from genes is used.

Human Sperm Cell

Smallest human cell, specialized for fertilization.

Human Egg Cell

Largest human cell, provides nutrients for embryo.

Red Blood Cell

Biconcave shape increases oxygen transport efficiency.

White Blood Cell

Variety of types involved in immune response.

Neuron

Specialized cell for transmitting nerve impulses.

Striated Muscle Fiber

Long, multinucleated cells for muscle contraction.

Surface Area to Volume Ratio

Key factor influencing cell size and function.

Adaptations to Increase SA:V

Structural changes enhancing efficiency of material exchange.

Axons of Neurons

Long extensions increasing surface area for signal transmission.

Root Hairs of Plants

Thin extensions increasing surface area for water absorption.

Pneumocytes

Cells lining alveoli, involved in gas exchange.

Type 1 Pneumocytes

Thin cells facilitating gas diffusion in alveoli.

Type 2 Pneumocytes

Rounded cells secreting surfactant to reduce surface tension.

Surfactant

Lipid-protein mixture preventing alveolar collapse.

Basement Membrane

Extracellular matrix separating alveolar and capillary epithelium.

Cristae of Mitochondria

Folded membranes increasing internal surface area.

Thylakoids of Chloroplasts

Membrane structures maximizing surface area for photosynthesis.

Brush Border

Microvilli-covered surface enhancing absorption in epithelial cells.

Proximal Convoluted Tubule (PCT)

Kidney structure lined with microvilli for solute reabsorption.

Intestinal Epithelium

Cells with brush border for nutrient absorption.

Epithelial Cells

Flattened cells optimizing gas and nutrient diffusion.

Alveoli

Air sacs in lungs for gas exchange.

Capillary Endothelium

Thin layer facilitating gas exchange with alveoli.

Basement Membrane

Layer anchoring cells with adhesion proteins.

Pneumocytes

Cells in lungs facilitating gas exchange.

Capillary Endothelium

Single layer of flat cells in capillaries.

Efficient Diffusion

Optimal gas exchange across thin capillary walls.

Striated Muscle Fibers

Muscle cells with a striped appearance.

Contractile Tissue

Tissue capable of shortening for movement.

Types of Muscle Tissue

Skeletal, cardiac, and smooth muscle types.

Smooth Muscle

Involuntary muscle, non-striated in appearance.

Skeletal Muscle

Voluntary, striated muscle attached to bones.

Cardiac Muscle

Striated muscle forming the heart walls.

Myofibrils

Cylindrical structures in muscle fibers for contraction.

Sarcomeres

Repeating units in myofibrils containing actin and myosin.

Titin

Protein allowing muscle fiber relaxation after contraction.

Sarcoplasmic Reticulum (SR)

Specialized ER for calcium storage in muscle cells.

Myofibers

Multinucleated muscle fibers with peripheral nuclei.

Fascicles

Bundles of muscle fibers running lengthwise.

Intercalated Discs

Junctions between cardiac cells for electrical impulse transmission.

Cardiac Cell Characteristics

Short, branched, single nucleus muscle cells.

Electrical Impulse Transmission

Rapid signal propagation in cardiac muscle.

Gametes

Haploid cells for sexual reproduction.

Sperm Cells

Male gametes delivering DNA to egg cells.

Egg Cells

Female gametes surrounded by protective structures.

Acrosome

Enzyme sac in sperm for egg fertilization.

Receptor Proteins

Bind sperm to egg cell's zona pellucida.