regulation of animal cell shape Flashcards
What is the cytoskeleton
✔ The cytoskeleton is a dynamic network of protein filaments that provides structural support, shape, and movement to cells.
cytoskeleton functions
Maintains cell shape and internal organization.
Anchors organelles in place.
Rapidly disassembles and reassembles, allowing cell shape changes.
Facilitates cell movement (e.g., cilia, flagella, muscle contraction).
Enables intracellular transport of organelles and vesicles.
What are the three components of the cytoskeleton?
✔ Microtubules – hollow tubes of tubulin, resist compression, used in motility (cilia/flagella) & intracellular transport.
✔ Microfilaments – thin actin filaments, resist tension, maintain cell shape, help with movement (muscle contraction, amoeboid motion).
✔ Intermediate filaments – fibrous proteins (keratin, lamin, neurofilaments), provide strength and permanent structural support.
What are microtubules, and what are their functions?
Microtubules are hollow tubes composed of tubulin subunits.
✔ They radiate out from the centrosome and provide:
Cell shape support (resist compression).
Organelle & vesicle transport (motor proteins “walk” organelles along microtubules).
Cell motility (flagella & cilia movement).
How do microtubules assist in cell movement?
1️⃣ Flagella – enable movement with a snake-like motion (e.g., sperm cells).
2️⃣ Cilia – move in a rowing-like motion to transport fluids past fixed cells (e.g., in the respiratory tract).
🔹 If cells are anchored in place, cilia beat to move extracellular fluid (e.g., clearing mucus in airways).
How do microtubules assist in intracellular transport?
✔ Microtubules act like highways inside the cell.
✔ ATP-powered motor proteins “walk” along them, carrying vesicles and organelles to specific locations.
Example: Vesicles travel from the Golgi apparatus to the plasma membrane for secretion.
What are microfilaments, and what are their functions?
✔ Microfilaments are composed of actin and form double chains.
✔ They provide tensile strength and support:
Cell shape – form the cortical network under the plasma membrane, making it less fluid.
Cell movement – interact with myosin for contraction (e.g., muscle movement, amoeboid motion).
Cytoplasmic streaming – helps distribute materials inside plant cells
How do actin and myosin interact in microfilaments?
Muscle contraction (sliding filament theory).
Amoeboid movement (e.g., white blood cells crawling).
Cytoplasmic streaming (movement of organelles and nutrients in plants).
What are intermediate filaments, and what are their functions?
Intermediate filaments are supercoiled cables made of proteins like:
Keratins (hair, nails, skin).
Lamins (support nuclear envelope).
Neurofilaments (stabilize neurons).
✔ Functions:
More permanent than microtubules or microfilaments.
Maintain cell shape and anchor organelles.
Remain even after the cell dies (e.g., in hair and outer skin).
What are the three main types of cell junctions?
Tight junctions – Seal cells tightly to prevent fluid leakage (e.g., intestines).
✔ Desmosomes – Rivet-like structures that provide strong cell-to-cell attachment (e.g., muscle cells).
✔ Gap junctions – Channels that allow communication by permitting ions and small molecules to pass (e.g., heart cells).
What is the function of tight junctions?
✔ Tight junctions form a continuous seal between adjacent cells.
✔ Prevents movement of fluids between cells (e.g., intestinal lining).
What is the function of desmosomes?
✔ Desmosomes function as anchoring junctions that hold cells together like rivets.
✔ Example: Muscle cells rely on desmosomes to stay attached—a torn muscle is a torn desmosome.
What is the function of gap junctions?
✔ Gap junctions create cytoplasmic connections between cells, allowing ions and small molecules to pass.
✔ Enable fast communication (e.g., heart muscle cells coordinate contractions via gap junctions).
What is the extracellular matrix (ECM), and why is it important?
✔ The ECM is a network of molecules outside cells that provides support and structure.
✔ Composition:
Collagen – provides tensile strength.
Proteoglycan complex – traps water, resists compression, and keeps tissues hydrated.
Fibronectin – attaches cells to the ECM.
Integrins – connect the ECM to the cytoskeleton, enabling communication.
What is collagen, and what role does it play in the ECM?
✔ Collagen is the most abundant ECM glycoprotein.
✔ Provides tensile strength (resistance to stretching).
✔ Embedded in a proteoglycan matrix, which traps water to keep tissues hydrated.
Example: Skin strength and elasticity depend on collagen.
What are proteoglycans, and why are they important?
✔ Proteoglycans are proteins with extensive sugar chains.
✔ Function:
Trap water, making the ECM gel-like and resistant to compression.
Help retain tissue shape and hydration.
How is the ECM linked to the cytoskeleton?
✔ Fibronectins attach cells to the ECM.
✔ Integrins are membrane proteins that link the ECM to the cytoskeleton.
✔ This connection enables signal transmission from the ECM to the cell interior.
What are the three components of the cytoskeleton, and how do they differ?
✔ Microtubules – hollow tubes of tubulin, resist compression, enable motility & intracellular transport.
✔ Microfilaments – thin actin filaments, resist tension, allow shape changes & movement.
✔ Intermediate filaments – strong, rope-like, anchor organelles, provide structural stability.
What membrane protein connects the ECM to the cytoskeleton?
Integrins – allow communication between the ECM and cell interior.
