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BIOL1028

Cytoskeleton

Dee Whitworth Room: 343 Phone: x50972 Email: d.whitworth@uq.edu.au

Introduction

• Cytoskeleton is a network of fibres • extends throughout the cytoplasm • cells’ internal skeleton

Introduction

• Maintenance of cell shape • resists compression & torsion • animal cells lack a cell wall

Introduction

• Organisation of structures within the cell • cell is not a bag of water with organelles floating around • e.g. position of nucleus

Introduction

• Organisation of processes within the cell • e.g. cell division & transport between organelles

• Cell motility • e.g. cilia, flagella & pseudopodia

Introduction

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Introduction

• Contraction of muscle cells

Cardiac muscle Skeletal muscle

Smooth muscle Skeletal muscle

Introduction

• Cytoskeleton consists of 3 types of fibres: • Actin • microfilaments

• Tubulin • microtubules

• Intermediate filaments

Introduction

• Different fibres have very specific roles

Actin

• Most abundant intracellular protein (1-5%) • Highly conserved throughout evolution

Leur – skate Danre – zebrafish Homsa – human

Trisc – shark Galga – chook Xentr – toad

Brafl – lancelet Sacce – yeast

Actin

• Also called microfilaments • Solid rods of approximately 7nm in diameter • composed of globular actin proteins • organised into two intertwined strands

Actin

• Dispersed throughout the entire cytoplasm • but, forms a dense meshwork immediately beneath the plasma membrane • Determines & maintains the cell’s shape • Provides mechanical strength by resisting tensive forces

Actin

• In association with myosin filaments forms contractile structures: • muscle cells – sarcomeres • cleavage furrow of dividing cells • pseudopodia

Actin

• In association with myosin filaments forms contractile structures: • muscle cells – sarcomeres • cleavage furrow of dividing cells • pseudopodia

Actin

• In association with myosin filaments forms contractile structures: •...