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?

Protein synthesis Signup and view all the answers

What is the diameter range of intermediate filaments?

8 to 10 nm Signup and view all the answers

Which type of protein is vimentin classified as?

Fibrous protein of connective tissues Signup and view all the answers

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

It disintegrates into vesicles Signup and view all the answers

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

Maintaining spatial organization Signup and view all the answers

What is the primary function of hyaloplasm in cells?

Synthesis and degradation of proteins Signup and view all the answers

Which components primarily compose microtubules?

Alpha and beta globular proteins Signup and view all the answers

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

25 nm Signup and view all the answers

What role do kinesins play in relation to microtubules?

Transport towards the plasma membrane Signup and view all the answers

What percentage of the chemical composition of hyaloplasm is water?

85% Signup and view all the answers

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

Vesicular filaments Signup and view all the answers

What is the role of the associated proteins with microtubules?

Stabilize microtubules and assist in vesicle movement Signup and view all the answers

Which type of metabolic reactions primarily occur in the hyaloplasm?

Synthesis and degradation Signup and view all the answers

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

Towards the plasma membrane Signup and view all the answers

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

Dynein Signup and view all the answers

Which protein attaches kinesin motor proteins to the vesicle membrane?

Kinectin Signup and view all the answers

What characterizes the dynein movement along the microtubule?

It transports cytoplasmic components towards the minus end. Signup and view all the answers

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

Kinesin is active while dynein is inactive in the upper vesicle. Signup and view all the answers

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

Dynactin complex Signup and view all the answers

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

The end of the microtubule towards which dynein transports vesicles. Signup and view all the answers

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

They only operate independently of each other. Signup and view all the answers

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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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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.