Cell Biology: Hyaloplasm and Cytoskeleton
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Questions and Answers

What is the primary function of intermediate filaments in eukaryotic cells?

  • Forming a supportive network for the nuclear envelope (correct)
  • Transport of organelles
  • Facilitating pseudopodia extension
  • Enabling cell division

Which fibrous protein is specifically associated with muscle cells?

  • Desmin (correct)
  • Vimentin
  • Lamin
  • Neurofilament proteins

What role do cytokeratins play in epithelial cells?

  • Forming the nuclear envelope
  • Transporting intracellular vesicles
  • Facilitating cell division
  • Anchoring cells at desmosomes and hemidesmosomes (correct)

Which function is NOT performed by the cytoskeleton?

<p>Protein synthesis (B)</p> Signup and view all the answers

What is the diameter range of intermediate filaments?

<p>8 to 10 nm (C)</p> Signup and view all the answers

Which type of protein is vimentin classified as?

<p>Fibrous protein of connective tissues (B)</p> Signup and view all the answers

During cell division, what happens to the network of lamins?

<p>It disintegrates into vesicles (C)</p> Signup and view all the answers

What is one of the primary roles of the cytoskeleton in a cell?

<p>Maintaining spatial organization (D)</p> Signup and view all the answers

What is the primary function of hyaloplasm in cells?

<p>Synthesis and degradation of proteins (A)</p> Signup and view all the answers

Which components primarily compose microtubules?

<p>Alpha and beta globular proteins (A)</p> Signup and view all the answers

What is the diameter of a microtubule formed from 13 protofilaments?

<p>25 nm (A)</p> Signup and view all the answers

What role do kinesins play in relation to microtubules?

<p>Transport towards the plasma membrane (B)</p> Signup and view all the answers

What percentage of the chemical composition of hyaloplasm is water?

<p>85% (C)</p> Signup and view all the answers

Which of the following is NOT a type of filament in the cytoskeleton?

<p>Vesicular filaments (A)</p> Signup and view all the answers

What is the role of the associated proteins with microtubules?

<p>Stabilize microtubules and assist in vesicle movement (B)</p> Signup and view all the answers

Which type of metabolic reactions primarily occur in the hyaloplasm?

<p>Synthesis and degradation (A)</p> Signup and view all the answers

What is the direction of movement for kinesin along a microtubule?

<p>Towards the plasma membrane (C)</p> Signup and view all the answers

Which protein is responsible for transporting vesicles towards the minus end of a microtubule?

<p>Dynein (C)</p> Signup and view all the answers

Which protein attaches kinesin motor proteins to the vesicle membrane?

<p>Kinectin (C)</p> Signup and view all the answers

What characterizes the dynein movement along the microtubule?

<p>It transports cytoplasmic components towards the minus end. (A)</p> Signup and view all the answers

Which statement is true regarding the motor proteins in the vesicles?

<p>Kinesin is active while dynein is inactive in the upper vesicle. (A)</p> Signup and view all the answers

Which component is involved in anchoring dynein to the vesicle membrane?

<p>Dynactin complex (D)</p> Signup and view all the answers

What does the term 'negative pole' refer to in the context of microtubule movement?

<p>The end of the microtubule towards which dynein transports vesicles. (A)</p> Signup and view all the answers

Which of the following is NOT a characteristic feature of kinesin and dynein transport systems?

<p>They only operate independently of each other. (A)</p> Signup and view all the answers

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Flashcards

Kinesin

A protein involved in transporting cargo towards the plus end of a microtubule.

Dynein

A protein involved in transporting cargo towards the minus end of a microtubule.

Dynactin

A protein complex that helps dynein bind to microtubules.

Kinectin

A protein that connects kinesin to vesicles.

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Microtubule (MT)

A long, cylindrical structure that serves as a track for motor proteins to move cargo.

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Plus end of a microtubule

The end of a microtubule where new subunits are added.

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Minus end of a microtubule

The end of a microtubule where subunits are removed.

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Microtubule-based transport

The movement of vesicles along microtubules, powered by motor proteins.

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What is hyaloplasm?

A viscous gel inside cells where organelles and the cytoskeleton are found.

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What are the components of hyaloplasm?

Hyaloplasm contains various non-membrane bound particles like lipid droplets, glycogen, starch, and free ribosomal subunits.

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What is the chemical composition of hyaloplasm?

Hyaloplasm, a gel, holds 85% water, enzymes, amino acids, ions, RNA, glucose, and proteins.

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What is the role of hyaloplasm in the cell?

Hyaloplasm is the site of many essential metabolic reactions, including protein synthesis and degradation.

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What is the cytoskeleton?

A network of fibers that provides structure and support to the cell.

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What are microtubules?

Microtubules are hollow tubes made of alpha and beta tubulin proteins.

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What are microfilaments?

Actin microfilaments are thin, flexible fibers made of the protein actin.

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What are intermediate filaments?

Intermediate filaments are rope-like fibers that provide structural support and help connect cells.

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Intermediate Filaments

Stable polymers found in the cytoplasm and nucleus, with a diameter of 8-10nm. They are made of fibrous proteins and contribute to cell structure and support.

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Lamins

A type of intermediate filament found in the nucleus of eukaryotic cells. They form a network that supports the nuclear envelope and anchors to chromatin.

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Cytokeratins

Fibrous proteins found specifically in epithelial cells, they form a network that anchors to desmosomes and hemidesmosomes, providing resistance to pulling forces.

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Vimentin

A fibrous protein specific to connective and cartilage cells. Found in the cytoplasm, it contributes to the structural integrity of these tissues.

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Desmin

A protein specific to muscle cells. It reinforces the myofibrils, giving muscle cells their striated appearance.

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Neurofilament proteins

Proteins found in neurons that form neurofilaments, providing structural support to these long, intricate cells.

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Cytoskeleton

A complex network of fibers that provides structural support to cells, transports organelles and substances throughout the cytoplasm, and contributes to cell movement and division.

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Intracellular Transport

The movement of cellular components such as vesicles, organelles, and molecules within the cytoplasm of a cell.

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Study Notes

Hyaloplasm

  • Hyaloplasm, also called cytosol, is a viscous gel that surrounds organelles and the cytoskeleton
  • Contains particles not enclosed by membranes, like lipid inclusions, glycogen particles (sometimes in rosettes), starch particles (in plant cells), and free ribosomal subunits
  • Chemical composition includes water (85%), enzymes, amino acids, ions, RNA, glucose, and proteins
  • Hyaloplasm is the site of many metabolic reactions, protein synthesis and degradation

Cytoskeleton

  • Includes microtubules (MTs), actin microfilaments (MFs), and intermediate filaments (IFs)
  • MTs are unstable, polarized polymers of alpha (α) and beta (β) tubulin dimers; 13 protofilaments form a hollow tube (25 nm diameter)
  • MTs have a (+) end (faster polymerization, toward the plasma membrane) and a (-) end (slower polymerization, toward the cell center)
  • Associated proteins (MAPs) stabilize MTs and facilitate vesicle and organelle transport along MTs (e.g., kinesins move toward the (+) end, dyneins toward the (-) end)
  • MTs are highlighted by immunofluorescence
  • MTs are stable or labile, depending on fixative and temperature. Stable MTs are permanent structures.

Microtubules:

  • MTs are about 25 nm in diameter, made up of 13 parallel protofilaments
  • Polymerization requires GTP and Mg2+
  • Polymerization is faster at the (+) end and slower at the (-) end
  • Associated proteins control polymerization and depolymerization
  • Microtubules are involved in cell shape, chromosome movement, organelle transport, and cell division

Microfilaments (actin filaments):

  • MFs are 5-7 nm in diameter, made of G-actin monomers polymerized into F-actin filaments
  • Polymerization requires ATP and Mg2+
  • MFs have a (+) and (-) end
  • Associated proteins organize and control polymerization/depolymerization (e.g., profilin, caldesmon)
  • They are involved in muscle contraction, cell movement (e.g., pseudopodia), and intracellular transport
  • Myosin I is a motor protein that moves vesicles and organelles along actin filaments

Intermediate filaments:

  • Intermediate filaments (IFs) are stable polymers, 8-10 nm in diameter
  • Their molecular architecture involves monomers, dimers, tetramers, and eight protofilaments forming a filament.
  • Different types of intermediate filaments (e.g., lamins, cytokeratins, vimentin, desmin) are specific for certain cell types and tissues.
  • They provide structural support and maintain cell shape.

General functions of the cytoskeleton

  • Structural support and maintenance of cell shape
  • Transport of vesicles and organelles within the cell
  • Cell motility, movement , and cytokinesis
  • Intracellular organization

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Chapter 3: Hyaloplasm & Cytoskeleton PDF

Description

Explore the fascinating components of cell biology, focusing on hyaloplasm and the cytoskeleton. This quiz covers the structural and functional aspects of cytosol, organelles, and the various types of filaments involved in cellular processes. Test your knowledge about the critical roles these components play in metabolic activities and transport mechanisms.

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