cell bio

Microfilaments

Thin, flexible filaments that support cell shape, contribute to motility (e.g., muscle contraction), and form structures like microvilli.

Intermediate Filaments

Ropelike fibers providing mechanical support, especially in epithelial cells, neurons, and the nuclear membrane.

Microtubules

Long, hollow cylinders made of tubulin that support cell shape, facilitate intracellular transport, and form structures like the mitotic spindle, cilia, and flagella.

Role of Actin

Key component of microfilaments involved in cellular movements, muscle contraction, and cytokinesis.

Actin vs. Lamin

Actin forms microfilaments while lamin forms intermediate filaments in the nuclear lamina.

Diseases from Mutations in Actin

Mutations in actin can lead to defects in cell movement, immune function, and muscle contraction, such as cardiac and skeletal muscle disorders.

Myosin

A motor protein that interacts with actin filaments in muscle cells, generating force for muscle contraction.

Role of Calcium in Muscle Contraction

Calcium ions bind to troponin on actin filaments, allowing myosin heads to interact with actin and contract the muscle.

Diseases from Microtubule Mutations

Can lead to neurodegenerative diseases caused by malfunctioning motor proteins like dynein or kinesin.

Intermediate Filaments Examples

Include proteins like keratin (in epithelial cells), vimentin (in mesenchymal cells), and lamin (in the nuclear membrane).

Diseases from Intermediate Filament Mutations

Mutations can cause epidermolysis bullosa due to keratin defects or neurodegenerative disorders from vimentin or lamin mutations.

Mitosis

Somatic cell division for growth and repair, producing two genetically identical daughter cells.

Meiosis

Reproductive cell division that reduces chromosome number by half, resulting in four non-identical haploid cells.

Interphase

The cell growth phase where DNA is replicated, consisting of G1, S, and G2 phases.

M Phase

The phase in the cell cycle where the cell divides (mitosis or meiosis) and undergoes cytokinesis.

Cyclins

Proteins that activate Cyclin-dependent kinases (Cdks) to regulate the progression of the cell cycle.

G1/S-cyclin

Cyclin that is highest in G1 and initiates DNA replication.

S-cyclin

Cyclin that is highest in S-phase to ensure DNA replication.

M-cyclin

Cyclin that is highest in M-phase, facilitating mitosis.

CKIs (p27)

Cyclin-dependent kinase inhibitors that halt cell cycle progression.

Wee1

A kinase that inhibits cyclin/CDK activity.

Cdc25

A phosphatase that activates cyclin/CDKs.

APC/C

Ubiquitin ligase complex that targets proteins for degradation, regulating mitosis progression.

Centrosome Duplication

Occurs during interphase to form the spindle apparatus in mitosis.

Cohesin

Protein that holds sister chromatids together until anaphase.

Kinetochore

Structure that attaches chromosomes to the mitotic spindle.

Apoptosis

Programmed cell death that eliminates unwanted cells without inflammation.

Necrosis

Uncontrolled cell death due to injury, leading to inflammation.

Intracellular Apoptotic Cascade

Cascade initiated by mitochondrial release of cytochrome C, activating caspases.

Caspases in Apoptosis

Caspases that play key roles in starting (initiator) and executing (executioner) the apoptotic process.

Mitochondria in Apoptosis

Alter mitochondrial outer membrane permeability leads to cytochrome C release, forming the apoptosome which activates caspase-9.

Bcl2

Protein that regulates mitochondrial membrane integrity; has pro-apoptotic and anti-apoptotic forms.

Phagocytes

Cells that remove apoptotic cells by phagocytosis.

Tight Junctions

Junctions that seal gaps between adjacent cells, preventing leakage.

Adherens Junctions

Junctions that anchor cells to each other via cadherins and catenins.

Desmosomes

Junctions providing mechanical strength via cadherins linking intermediate filaments.

Gap Junctions

Junctions allowing direct communication between cells through connexons.

Hemidesmosomes

Junctions anchoring cells to the extracellular matrix via integrins.

Cadherins

Calcium-dependent adhesion molecules mediating cell-to-cell junctions.

Catenins

Proteins linking cadherins to the cytoskeleton, mainly actin filaments.

Proteoglycans

Components of the extracellular matrix made of glycosaminoglycans (GAGs) that support cell signaling and structure.

Fibrous Proteins

Mainly collagen, which provides structural integrity to tissues.

Glycoproteins

Proteins with sugar chains, key for many biological functions in the extracellular matrix.

Integrins

Transmembrane receptors that connect cells to the extracellular matrix, involved in adhesion and signaling.

Cadherin

A protein involved in cell adhesion, facilitating contact between cells.

Cyclin-dependent kinase (Cdk)

A protein kinase that regulates the cell cycle progression.

Caspase

Enzymes responsible for the execution of apoptosis.

Laminin

An extracellular matrix protein involved in basal lamina structure.