2B and 2C extracellular and endosymbiont

What does “endosymbiont theory” mean?

Endo = inside; symbiosis = living together; theory that eukaryotic cells formed when one cell engulfed another and they lived together in a mutually beneficial relationship

Why is endosymbiont theory still considered a theory?

Exact mechanism unknown; multiple models exist; strong supporting evidence still present

What is the basic idea of endosymbiont theory?

Ancestral prokaryotic cell engulfed another prokaryote which became an organelle (mitochondria/chloroplast), forming eukaryotic cells

What is LUCA and LECA?

LUCA = Last Universal Common Ancestor; LECA = Last Eukaryotic Common Ancestor

What type of DNA do plastids have?

Circular DNA; no histones; no introns; similar to prokaryotic DNA

How do plastids reproduce?

Binary fission (like bacteria)

What type of ribosomes are in mitochondria and plastids?

Bacterial-like ribosomes

What is unique about mitochondrial and chloroplast membranes?

Mitochondria = double membrane; chloroplasts = triple membrane

What lipid in mitochondria supports endosymbiont origin?

Cardiolipin in inner mitochondrial membrane

What organisms are mitochondria and chloroplasts thought to originate from?

Mitochondria = α-proteobacteria; chloroplasts = cyanobacteria

What is the extracellular matrix (ECM)?

Hydrated network of glycoproteins and proteoglycans located outside the cell

What does extracellular and matrix mean?

Extracellular = outside the cell; matrix = meshwork of components

Why is ECM important?

Provides structural support; allows multicellular organisms to be strong

What is cell-cell adhesion?

Cells connected to each other

What is cell-matrix adhesion?

Cells attached to ECM/support structure

What are fibroblasts?

Cells that produce ECM components

Fibroblasts are specialized connective tissue cells that primarily secrete components of the extracellular matrix (ECM) to maintain structural integrity and repair tissues. They produce collagen (types I and III), elastin, fibronectin, laminin, and glycosaminoglycans (ground substance)

How do fibroblasts move?

Motile; move by breaking down and rebuilding ECM (remodelling)

What are the main functions of the ECM?

Support; regulates cell division; adhesion; motility; migration; differentiation; growth factor reservoir; signalling via dynamic reciprocity

providing structural support, facilitating cell adhesion, enabling communication, regulating behavior (migration, proliferation, differentiation), and assisting with tissue repai

What are the 4 main ECM component categories?

Structural fibres; hydrated matrix components; adhesive molecules; ground substance

What is the main structural fibre in ECM?

Collagen (most abundant protein in human body)

What makes up the hydrated matrix?

Proteoglycans and elastin

What is elastin?

Stretchy protein that allows tissues to recoil

What is fibrillin?

Flexible protein supporting elastic fibres

What are key adhesive molecules in ECM?

Fibronectin and laminin

What is the function of adhesive glycoproteins? (fillamen and laminin)

Bind ECM components together and attach ECM to cell surface via integrins

Both crucial extracellular matrix (ECM) glycoproteins that facilitate cell adhesion, migration, growth, and differentiation. Fibronectin is generally found in the stromal matrix (interstitial matrix) and aids in fibroblast adhesion and wound healing, while laminin is a major component of the basement membrane, supporting epithelial cell adhesion and tissue structure.

What is ground substance?

Proteoglycan-based material that holds water and forms hydrated environment

How can ground substance vary?

Blood = fluid; bone = rigid (mineralised); cartilage = flexible

How are ECM components organised?

Arranged into loose or dense/packed structures depending on tissue

Do animal cells have a cell wall?

No; they rely on ECM for support

What must you know about ECM for exams?

Definition; components; fibroblast role; functions; adhesion types; ground substance variation