DP Biology B2.3 Cell Specialization

Fertilization

The fusion of male and female gametes to form a single diploid zygote.

Zygote

A diploid cell formed from the fusion of gametes; it divides rapidly to produce all other cells of the organism.

Cell differentiation

The process by which unspecialized cells become specialized by activating certain genes while repressing others.

Morphogen

A signalling molecule that forms a concentration gradient in an embryo, influencing cell fate and differentiation.

Gene expression

The process by which specific genes are transcribed and translated to produce proteins that determine cell structure and function.

Stem cell

An undifferentiated cell capable of self-renewal and differentiation into specialized cell types.

Self-renewal

The ability of a stem cell to divide and produce identical daughter stem cells.

Differentiation potential

The range of specialized cell types a stem cell can form, depending on its potency.

Totipotent

Stem cells that can give rise to all cell types of an organism, including embryonic and extra-embryonic tissues.

Pluripotent

Stem cells that can differentiate into nearly all cell types within the body but not extra-embryonic tissues.

Multipotent

Stem cells that can produce a limited range of cell types related to a specific tissue or organ.

Unipotent

Stem cells that can divide but only produce one specific type of differentiated cell.

Embryonic stem cell

A pluripotent cell derived from the inner cell mass of a blastocyst; can form most cell types in the body.

Adult stem cell

A multipotent stem cell found in differentiated tissues; maintains and repairs tissues through regeneration.

Stem cell niche

A microenvironment in tissues that maintains stem cells and regulates their self-renewal and differentiation.

Bone marrow

A stem cell niche producing blood cells through hematopoietic stem cell differentiation.

Hair follicle

A stem cell niche where epithelial stem cells generate new hair and repair skin tissue.

Specialized cell

A cell with a specific structure and function within a multicellular organism (e.g., neuron, red blood cell).

Gamete

A haploid reproductive cell (sperm or egg) that carries genetic material to form a zygote during fertilization.

Sperm cell

A male gamete specialized for motility and delivering genetic material to the egg.

Egg (ovum)

A large, nutrient-rich female gamete specialized to support early embryonic development.

Neuron

A specialized cell transmitting electrical and chemical signals within the nervous system.

Striated muscle fibre

A long, multinucleated cell specialized for contraction through organized actin and myosin filaments.

Red blood cell (erythrocyte)

A biconcave, anucleate cell adapted for oxygen transport due to high hemoglobin content.

White blood cell (leukocyte)

A cell of the immune system specialized in defense against pathogens.

Surface area-to-volume ratio (SA:V)

The ratio that affects the rate of material exchange across the cell surface relative to metabolic demand.

Constraint on cell size

The limitation on how large a cell can grow because surface area does not increase proportionally with volume.

Scientific model

A simplified representation of a complex system, used here to illustrate how SA:V affects diffusion.

Surface area adaptations

Structural features that increase a cell's surface area relative to its volume to enhance exchange efficiency.

Microvilli

Microscopic projections on cell surfaces that increase surface area for absorption, e.g., intestinal or kidney cells.

Invagination

The folding inward of a cell membrane to increase surface area or form vesicles.

Erythrocyte (red blood cell)

A flattened, biconcave cell adapted for efficient gas exchange with a high SA:V ratio.

Proximal convoluted tubule (PCT) cell

Kidney cell with abundant microvilli to maximize reabsorption of solutes.

Type I pneumocyte

Extremely thin alveolar cell that minimizes diffusion distance for gas exchange.

Type II pneumocyte

Secretory alveolar cell producing surfactant to reduce surface tension in the lungs.

Surfactant

A phospholipid substance secreted by type II pneumocytes to prevent alveolar collapse.

Alveolus

A microscopic air sac in the lung where gas exchange occurs between air and blood.

Cardiac muscle cell (cardiomyocyte)

A branched, striated muscle cell connected by intercalated discs, allowing coordinated contraction.

Striated muscle fibre

A multinucleated, unbranched muscle cell containing organized myofibrils for voluntary movement.

Myofibril

A cylindrical structure composed of actin and myosin filaments responsible for muscle contraction.

Intercalated disc

Specialized junctions between cardiac muscle cells that allow rapid electrical and mechanical connectivity.

Sperm cell

A highly motile male gamete with a flagellum, acrosome, and mitochondria for fertilization.

Egg cell (ovum)

A large female gamete with stored nutrients and organelles for early development.

Flagellum

A whip-like structure that enables movement of cells such as sperm.

Acrosome

A vesicle at the head of a sperm cell containing enzymes to penetrate the egg's outer layers.

Nucleus (in gametes)

The haploid genetic material carried by a gamete to contribute to the zygote's genome.