Cell Cycle Control & Mitosis Quiz
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Questions and Answers

What is the term for the body cells produced by mitosis that contain the diploid number of chromosomes?

  • Sperm cells
  • Somatic cells (correct)
  • Germ cells
  • Ovum cells

During which phase of the cell cycle do chromatin fibers condense to form chromosomes?

  • Prophase (correct)
  • Anaphase
  • Interphase
  • Cytokinesis

How many chromosomes do human germ cells contain?

  • 22 chromosomes
  • 23 chromosomes (correct)
  • 46 chromosomes
  • 44 chromosomes

In female somatic cells, which chromosomes are active for transcription?

<p>Only one of the X chromosomes (B)</p> Signup and view all the answers

What process occurs at the conclusion of the G2 phase to complete the cell cycle?

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

What divides first during the process of mitosis?

<p>Nuclear material (B)</p> Signup and view all the answers

Which phase involves the disappearance of the nucleolus?

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

How many pairs of chromosomes do somatic cells have?

<p>22 pairs (A)</p> Signup and view all the answers

What is formed from the division of the cytoplasm in mitosis?

<p>Daughter cells (B)</p> Signup and view all the answers

Which method involves the degradation of phagocytosed material primarily by lysosomal enzymes?

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

What is the role of autophagy in cellular function?

<p>Eliminates damaged organelles and proteins (B)</p> Signup and view all the answers

What are autophagosomes primarily composed of during their formation?

<p>Double-membrane vesicles surrounding cytoplasm and organelles (D)</p> Signup and view all the answers

Which environmental conditions are known to induce autophagy?

<p>Food deprivation and hypoxia (C)</p> Signup and view all the answers

What is a residual body in the context of lysosomal function?

<p>Material that remains undigested after lysosomal processing (C)</p> Signup and view all the answers

What is the primary role of the molecular machinery found in the nucleus?

<p>To synthesize and process RNA types (C)</p> Signup and view all the answers

What mainly constitutes the nuclear envelope?

<p>A double membrane with perinuclear cisterna (D)</p> Signup and view all the answers

Which component of the nucleus is responsible for the exchange of substances with the cytoplasm?

<p>Nuclear pores (D)</p> Signup and view all the answers

What characteristic of the nuclear envelope affects substance exchange?

<p>It is impermeable to all ions and molecules (D)</p> Signup and view all the answers

In what form is DNA primarily found within the nucleus?

<p>Condensed and uniformly distributed chromatin (B)</p> Signup and view all the answers

What type of staining causes nuclei to appear intensely stained in preparations?

<p>Basic staining with hematoxylin (C)</p> Signup and view all the answers

What is the function of polyribosomes attached to the outer membrane of the nuclear envelope?

<p>To produce proteins using mRNA (B)</p> Signup and view all the answers

What is the primary function of spindle fibers during mitosis?

<p>To assist in chromosome alignment on the cell equator (A)</p> Signup and view all the answers

Which phase of mitosis is characterized by the separation of sister chromatids?

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

What happens to the nuclear envelope during metaphase?

<p>It disappears early in the phase (A)</p> Signup and view all the answers

In the absence of centrioles, what effect does this have on mitosis?

<p>Microtubule-nucleating material disperses, affecting spindle formation (C)</p> Signup and view all the answers

What significant structural change occurs to chromosomes during telophase?

<p>Chromosomes unwind into chromatin (C)</p> Signup and view all the answers

How do spindle fibers attach to chromosomes during metaphase?

<p>At the centromere region via kinetochores (B)</p> Signup and view all the answers

What is the immediate outcome of sister chromatids aligning parallel to the equator?

<p>They are prepared for separation during anaphase (A)</p> Signup and view all the answers

What initiates the development of the cleavage furrow during anaphase?

<p>A change in the spindle/kinetochore attachment site (B)</p> Signup and view all the answers

What occurs to the mitotic spindle during telophase?

<p>It disappears entirely (C)</p> Signup and view all the answers

Which type of chromatin do chromosomes reorganize into during telophase?

<p>Interphase heterochromatin and euchromatin (B)</p> Signup and view all the answers

Which class of antibiotics primarily functions by inhibiting bacterial protein synthesis?

<p>Tetracyclines and Macrolides (A)</p> Signup and view all the answers

What substance inhibits tRNA binding by acting on the 60S ribosomal subunit?

<p>Shiga toxin (D)</p> Signup and view all the answers

What is the primary role of lysosomes in the cell?

<p>Digesting phagocytosed material (D)</p> Signup and view all the answers

How are lysosomal enzymes produced?

<p>Manufactured in the rough endoplasmic reticulum (rER) (C)</p> Signup and view all the answers

Which type of cytoplasmic inclusion is associated with patterns of cell activity?

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

What is the physiological function of peroxisomes in cells?

<p>Degradation of fatty acids and detoxification of harmful substances (D)</p> Signup and view all the answers

What condition is caused by the action of Diphtheria toxin on the ribosome?

<p>Inhibition of protein synthesis leading to cell death (B)</p> Signup and view all the answers

What cellular structure is responsible for exporting digested products from lysosomes into the cytosol?

<p>Lysosomal membrane carrier proteins (D)</p> Signup and view all the answers

Which of the following correctly correlates with the structure and function of a proteasome?

<p>They degrade protein molecules into smaller peptides (B)</p> Signup and view all the answers

Which condition indicates the impact of lysosomal derangement on cellular health?

<p>Accumulation of undigested substrates (A)</p> Signup and view all the answers

What is the primary role of contractile bundles formed by actin filaments?

<p>Induce cleavage furrows during mitotic division (A)</p> Signup and view all the answers

Which cyclin is initially synthesized during the early G1 phase of the cell cycle?

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

What feature distinguishes the plus end of an actin filament?

<p>It grows faster than the minus end (A)</p> Signup and view all the answers

Which complex allows the cell to exit the S phase during the cell cycle?

<p>Cyclin A-CDK2 (B)</p> Signup and view all the answers

Which functional form of actin provides structural support to the cell cortex?

<p>Gel-like networks (A)</p> Signup and view all the answers

What is the main function of the cyclin B-CDK1 complex in the cell cycle?

<p>To facilitate exit from the G2 phase into mitosis (A)</p> Signup and view all the answers

What is primarily formed by the organization of actin filament bundles?

<p>The core structure of microvilli (B)</p> Signup and view all the answers

What is the role of N-terminal residues in determining protein half-lives?

<p>They dictate the stability and turnover rate of the protein. (D)</p> Signup and view all the answers

Which statement regarding crystallins in the lens of the eye is true?

<p>They were primarily synthesized during early development and have long half-lives. (C)</p> Signup and view all the answers

Which type of amino acid residues are considered destabilizing at the N-terminal for protein half-lives?

<p>Arginine and acetylated alanine (C)</p> Signup and view all the answers

What is one of the primary functions of peroxisomes in the cell?

<p>Beta-oxidation of long-chained fatty acids (C)</p> Signup and view all the answers

What can result from the failure of proteasomes to degrade misfolded proteins?

<p>Accumulation of abnormal proteins leading to disease (B)</p> Signup and view all the answers

What is the primary reason for protein maturation in cells?

<p>To activate proteins to functional forms and localize them (D)</p> Signup and view all the answers

How many high-energy phosphate bonds are hydrolyzed to charge tRNA with its amino acyl moiety?

<p>2 high-energy bonds (A)</p> Signup and view all the answers

Which modification is specifically important for blood clotting?

<p>γ-carboxylation of glutamic acid (D)</p> Signup and view all the answers

What is the function of molecular chaperones in protein maturation?

<p>To assist in the folding of proteins into their 3D structures (D)</p> Signup and view all the answers

Which amino acid modifications are involved in collagen synthesis?

<p>Hydroxylation of proline and lysine (A)</p> Signup and view all the answers

What happens to misfolded proteins during the process of protein maturation?

<p>They are targeted for destruction (C)</p> Signup and view all the answers

Which type of glycosylation involves the attachment of carbohydrates to serine or threonine residues?

<p>O-linked glycosylation (D)</p> Signup and view all the answers

What is the main outcome of translocating newly formed peptidyl-tRNA from the A site to the P site during translation?

<p>Hydrolysis of one GTP to GDP (D)</p> Signup and view all the answers

Which of the following describes the role of signal peptides in protein maturation?

<p>They are essential for the transport of proteins to their final destination (C)</p> Signup and view all the answers

What pathway do cyclins enter after performing their specific functions?

<p>Ubiquitin-proteasome pathway (C)</p> Signup and view all the answers

Which factor does NOT stimulate a cell to enter the cell cycle?

<p>Cellular dehydration (D)</p> Signup and view all the answers

What is the primary consequence of mutations in proto-oncogenes?

<p>Uncontrolled cell proliferation (C)</p> Signup and view all the answers

Which mechanism does the cell NOT use to enforce checkpoints in the cell cycle?

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

What structure attaches sister chromatids during cell division?

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

Which condition can lead to an increased expression of proto-oncogenes?

<p>Mechanical stretching (D)</p> Signup and view all the answers

What happens to oncogenes as a result of gene amplification?

<p>Their activity is increased (B)</p> Signup and view all the answers

Which function is associated with the checkpoints in the cell cycle?

<p>Ensuring adequate DNA synthesis (C)</p> Signup and view all the answers

Which of the following is NOT a direct result of cyclin degradation?

<p>Activation of growth factors (B)</p> Signup and view all the answers

During mitosis, what characteristic is observed in chromosomes?

<p>They become condensed and tightly coiled (C)</p> Signup and view all the answers

What is the term 'autophagy' derived from?

<p>Self-devouring (A)</p> Signup and view all the answers

What structural element surrounds organelles during the autophagy process?

<p>Elements of the endoplasmic reticulum (B)</p> Signup and view all the answers

What is primarily resistant to complete digestion in a lysosome?

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

Which method allows degradation of senescent organelles in the cell?

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

What initiates the formation of autophagosomes?

<p>Autophagy-related genes (A)</p> Signup and view all the answers

What cellular conditions are known to activate autophagy?

<p>Environmental stress (B)</p> Signup and view all the answers

Which type of vesicle is responsible for the transport of phagocytosed material?

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

What is the fate of an autophagosome after it fully forms?

<p>It fuses with a lysosome (A)</p> Signup and view all the answers

What is the primary material that remains after the degradation of lipids in lysosomes?

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

Which of the following best describes the role of autophagy in cellular processes?

<p>Cellular waste management (C)</p> Signup and view all the answers

What role do microtubule-associated proteins (MAPs) play in cellular function?

<p>They facilitate the translocation of organelles and vesicles. (A)</p> Signup and view all the answers

Which statement accurately describes the function of centrioles during cell division?

<p>They assist in the formation of the spindle apparatus. (C)</p> Signup and view all the answers

How does colchicine exert its clinical effects on leukocytes?

<p>By disrupting microtubule polymerization. (B)</p> Signup and view all the answers

Which of the following correctly describes the movement of motor proteins along microtubules?

<p>Kinesin moves vesicles to the plus end, while dynein moves them to the minus end. (B)</p> Signup and view all the answers

What is the significance of the dynamic process of microtubule formation during cell division?

<p>It allows for the symmetrically distributed daughter cells. (A)</p> Signup and view all the answers

Which of the following events occurs during the G1 phase of the cell cycle?

<p>Synthesis of macromolecules essential for DNA replication (B)</p> Signup and view all the answers

What distinguishes the S phase of the cell cycle from the G2 phase?

<p>The phase during which DNA replication occurs (D)</p> Signup and view all the answers

During which phase does the cell analyze DNA replication for errors before proceeding to mitosis?

<p>G2 phase (D)</p> Signup and view all the answers

What occurs to centrioles during the cell cycle, specifically in the G1 phase?

<p>Centrioles duplicate themselves (A)</p> Signup and view all the answers

What characterizes cells that have entered the G0 phase of the cell cycle?

<p>They are temporarily resting before re-entering the cell cycle (C), They permanently stop dividing (D)</p> Signup and view all the answers

What is the primary role of molecular chaperones in protein maturation?

<p>Aiding in the proper folding of proteins (B)</p> Signup and view all the answers

Which modification is crucial for the function of prothrombin in blood clotting?

<p>γ-carboxylation of glutamic acid (A)</p> Signup and view all the answers

What process is described by the removal of amino terminal or signal peptides from proteins?

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

Which of the following mechanisms is not directly involved in protein maturation?

<p>Transcriptional regulation (B)</p> Signup and view all the answers

What is the result of errors during the translation process?

<p>Misfolded proteins targeted for degradation (D)</p> Signup and view all the answers

What is the role of the sex chromatin in female cells?

<p>It is genetically inactive. (C)</p> Signup and view all the answers

What distinguishes the appearance of sex chromatin in neutrophilic leukocytes?

<p>It manifests as a drumstick-like appendage. (D)</p> Signup and view all the answers

What is the primary function of the nucleolus within the nucleus?

<p>Production of ribosomal subunits. (D)</p> Signup and view all the answers

Which characteristic differentiates heterochromatin from euchromatin?

<p>Heterochromatin is often visible as a clump in female cells. (C)</p> Signup and view all the answers

What component is commonly associated with the nucleolus, even though its functional significance is not well understood?

<p>Heterochromatin. (A)</p> Signup and view all the answers

Flashcards

Nucleus function

The nucleus holds the cell's blueprint (DNA) for structures and activities and houses the machinery for DNA replication and RNA synthesis (mRNA, tRNA, rRNA).

Nuclear envelope

Double membrane surrounding the nucleus, separating the nucleus from the cytoplasm, with nuclear pores for controlled transport.

Nuclear pores

Small openings in the nuclear envelope allowing controlled passage of molecules between the nucleus and cytoplasm.

Chromatin

Material in the nucleus that contains DNA and proteins, organizing DNA into chromosomes.

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Nuclear matrix

A protein scaffold inside the nucleus that gives the nucleus its structure and organizes the chromatin.

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Perinuclear cisterna

The narrow space between the two layers of the nuclear envelope.

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Chromosomes

Organized structures formed by chromatin when a cell is ready to divide, carrying the genetic material (DNA).

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What happens to chromatin in prophase?

Chromatin condenses into visible, thread-like chromosomes, each consisting of two identical sister chromatids.

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Centrosome in prophase

The centrosome divides into two, each containing a pair of centrioles and a microtubule-organizing center (MTOC), which migrate to opposite poles of the cell.

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Nucleolus in prophase

The nucleolus disappears.

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Somatic cells

Body cells produced by mitosis containing 46 chromosomes (diploid number), representing 23 homologous pairs.

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Germ cells

Sperm or ovum cells produced by meiosis containing 23 chromosomes (haploid number), with one sex chromosome (X or Y).

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Karyokinesis

The division of the nuclear material during mitosis.

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Cytokinesis

The division of the cytoplasm during mitosis.

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Mitosis stages

Prophase, metaphase, anaphase, and telophase.

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What is mitosis?

The process of cell division that results in the formation of two identical daughter cells.

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Phagosome

A vesicle that engulfs large particles like bacteria or cell debris for digestion by lysosomes.

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Autophagy

Process where cells break down their own components (like damaged organelles) for recycling and energy.

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Autophagosome

Membrane-bound vesicle formed during autophagy, containing parts of the cell destined for degradation.

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Why is autophagy important?

Autophagy helps remove damaged organelles, recycle materials, and maintain cell health by clearing debris.

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How are Atgs involved?

Atg genes regulate autophagy, ensuring proper formation of autophagosomes for degradation.

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MTOC

A microtubule organizing center, often found in the centrosome of a cell, where microtubules are assembled and anchored. It helps organize and regulate the movement of chromosomes during cell division.

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Astral rays

Microtubules that radiate outwards from the MTOC in the spindle apparatus. They help position the MTOC at the poles of the cell during mitosis.

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Spindle fibers

Microtubules that attach to the centromere region of chromosomes, guiding their movement and alignment during cell division.

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Kinetochore

A protein complex located on the centromere of a chromosome, serving as the attachment point for spindle fibers.

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What happens in prophase?

The nuclear envelope breaks down, chromosomes condense, and the mitotic spindle forms as microtubules grow from the MTOCs.

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What is karyokinesis?

The division of the nucleus during mitosis, where chromosomes are separated and distributed into daughter cells.

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What happens in metaphase?

Chromosomes align at the center of the cell (metaphase plate) with spindle fibers attached to their kinetochores.

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What happens in anaphase?

Sister chromatids separate and migrate to opposite poles of the cell, pulled by the spindle fibers. A cleavage furrow starts to form, indicating future cell division.

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What happens in telophase?

Chromosomes decondense, the nuclear envelope reforms around each set of chromosomes, and the cell finishes dividing (cytokinesis).

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Cleavage furrow

A groove that forms at the cell surface, pinching the cell membrane inward during cytokinesis, eventually dividing the cytoplasm into two daughter cells.

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Lysosome

A membrane-bound organelle containing acidic hydrolases (enzymes), responsible for digesting cellular debris, microorganisms, and worn-out organelles.

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Acid Hydrolases

Enzymes within lysosomes that function optimally in acidic environments, breaking down various biomolecules like proteins, lipids, and nucleic acids.

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Autolysosome

A lysosome that fuses with a part of the cell's own cytoplasm, digesting its internal components.

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Phagolysosome

A lysosome that fuses with a phagosome, a vesicle containing engulfed material like bacteria or debris.

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Translation Inhibition

Disrupting the process of protein synthesis from mRNA to protein, often targeting ribosomes.

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Shiga Toxin

A toxin produced by certain bacteria that inhibits protein synthesis by blocking tRNA binding to the ribosome.

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Diphtheria Toxin

A toxin produced by bacteria that inhibits translocation during protein synthesis, essentially halting the ribosome.

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Proteasome

A large protein complex that degrades damaged or misfolded proteins, playing a crucial role in maintaining protein quality control.

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Peroxisome

A small, single-membrane bound organelle that breaks down fatty acids and detoxifies harmful compounds.

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Cytoplasmic Inclusions

Various structures within the cytoplasm that can reflect the cell's activity, storage, or even disease states.

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Protein Maturation

The process of transforming a newly synthesized protein into its functional form, involving folding, modifications, and localization.

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Protein Folding

The process by which a linear polypeptide chain acquires a specific three-dimensional structure, often assisted by chaperone proteins.

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Proteolysis

The breakdown of proteins by enzymatic cleavage, usually removing specific amino acid sequences.

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Signal Peptides

Short amino acid sequences on proteins that act as signals for protein transport to specific locations within the cell.

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Glycosylation

The attachment of carbohydrate chains to proteins, often influencing protein stability, function, and localization.

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Acylation

The addition of fatty acids to proteins, typically helping anchor them to cellular membranes.

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Hydroxylation

The addition of a hydroxyl group (OH) to an amino acid, often crucial for protein structure and function.

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Phosphorylation

The addition of a phosphate group to an amino acid, often involved in cell signaling and regulation.

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γ-Carboxylation

The addition of a carboxyl group to a specific glutamate residue, often involved in calcium ion binding.

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What are actin filaments?

Thin filaments made of two coiled chains of globular subunits (G-actin) forming a filamentous protein (F-actin). They are 6 nm thick and have a faster-growing plus end and a slower-growing minus end.

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What are contractile bundles?

Actin filaments arranged loosely and parallel, with alternating plus and minus ends. They form contractile rings for cell division and are involved in moving organelles and vesicles.

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What are gel-like networks?

Actin filaments that form a mesh-like structure, providing support for the cell cortex (the cell's outer layer).

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What are bundles in terms of actin?

Actin filaments tightly packed together, forming the core of microvilli (finger-like projections on the cell surface).

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What are focal points?

Points where actin filaments connect to the extracellular matrix, providing anchorage and communication between the cell and its environment.

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Cell cycle control: What is the role of cyclins and CDKs?

Cyclins are proteins that activate cyclin-dependent kinases (CDKs). Different cyclin-CDK complexes drive the cell through different stages of the cell cycle.

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What happens in the G1 phase?

The cell grows in size, synthesizes necessary proteins, and prepares for DNA replication. Cyclin D binds to CDK4 and CDK6.

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Cell cycle control

The regulation of the cell cycle, ensuring proper progression through phases like growth, DNA replication, and division.

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Cyclin fate

After performing their function, cyclins are broken down by the ubiquitin-proteasome pathway, ensuring timely removal from the cell.

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Cell cycle checkpoints

Quality control mechanisms that monitor the cell cycle, ensuring essential events are completed before proceeding to the next phase.

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Triggers for cell cycle entry

Signals that initiate cell cycle progression, such as mechanical force, tissue injury, or cell death.

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Growth factors and proto-oncogenes

Ligands released during cell cycle initiation that indirectly trigger proto-oncogene expression, promoting cell proliferation.

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Oncogenes and cancer

Mutated proto-oncogenes that allow uncontrolled cell growth and contribute to cancer development.

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What are chromosomes?

Condensed chromatin fibers visible during mitosis and meiosis, carrying genetic information.

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Sister chromatids

Two identical copies of a chromosome connected at the centromere.

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Centromere

The point where sister chromatids are joined during mitosis and meiosis.

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Role of the proteasome

A protein complex responsible for degrading and removing damaged or misfolded proteins, maintaining cellular health.

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Protein Half-Life

The time it takes for half of a protein to be degraded in a cell. It's determined by the protein's amino acid sequence, specifically the N-terminal residue.

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N-end Rule

A rule that dictates a protein's half-life based on its N-terminal (first) amino acid. Certain amino acids, like arginine, destabilize the protein, leading to faster degradation. Others, like serine, stabilize it.

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PEST Sequences

Short amino acid sequences rich in proline (P), glutamate (E), serine (S), and threonine (T) that signal for faster protein degradation.

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Ubiquitination

A process where a small protein called ubiquitin is attached to another protein, tagging it for degradation by proteasomes.

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Peroxisome Function

Small organelles involved in breaking down long-chain fatty acids (beta-oxidation) and producing hydrogen peroxide as a byproduct. They also detoxify harmful molecules.

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What are phagosomes?

Vesicles that engulf larger molecules, like bacteria or cell debris, for degradation in lysosomes.

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What is autophagy?

A self-eating process where the cell degrades its own worn-out organelles or proteins using lysosomes.

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What is an autophagosome?

A vesicle containing parts of a cell, like damaged organelles, destined for breakdown by lysosomes.

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What is the importance of autophagy?

It helps remove damaged parts, recycle materials, and maintain cell health by clearing debris.

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What are Atgs?

Proteins that regulate autophagy, ensuring autophagosomes are formed correctly for degradation.

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What triggers autophagy?

Conditions like starvation, heat stress, or oxygen deprivation activate autophagy.

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What is a residual body?

A spent lysosome that contains undigested material, often lipids, after degrading other contents.

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How do autophagosomes and phagosomes reach lysosomes?

They fuse with either late endosomes or directly with lysosomes, ultimately leading to degradation of their contents.

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What are hydrolytic enzymes?

Enzymes within lysosomes that break down various biomolecules in an acidic environment.

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What is the role of lysosomes in cellular digestion?

Lysosomes are responsible for breaking down ingested material (via phagosomes), cellular debris (via autophagy), and worn-out organelles.

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Protein Elongation Energy Cost

Synthesizing a single peptide bond requires energy from the hydrolysis of four high-energy phosphate bonds.

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Translation Errors

Mistakes during translation lead to faulty proteins that can be targeted for destruction or become non-functional.

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Microtubule function

Microtubules are long, hollow cylinders made of tubulin protein. They are involved in cell shape, movement (cilia and flagella), and transport of organelles and vesicles.

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What is a centrosome?

The centrosome is a microtubule organizing center near the nucleus, consisting of two centrioles arranged perpendicular to each other.

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Centriole function

Centrioles help organize microtubules and replicate themselves before cell division. They are also involved in forming cilia and flagella.

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Dynein and kinesin

Dynein and kinesin are microtubule motor proteins that move vesicles and organelles along microtubules. Dynein moves towards the minus end, while kinesin moves towards the plus end.

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Colchicine effect

Colchicine inhibits microtubule polymerization by binding to tubulin. This disrupts leukocyte function, leading to an anti-inflammatory effect.

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Cell cycle

The series of events that a cell goes through as it prepares to divide into two daughter cells.

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Interphase

The longest phase of the cell cycle where the cell grows, copies its DNA, and prepares for division. It includes G1, S, and G2 phases.

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Mitosis

The shorter phase of the cell cycle where the cell's nucleus and cytoplasm divide, creating two identical daughter cells.

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G1 Phase

The first phase of interphase where the cell grows and makes proteins necessary for DNA replication.

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S Phase

The phase of interphase where the cell replicates its DNA, doubling its genetic material.

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Sex Chromatin

A tightly coiled and visible mass of heterochromatin found in female cells, representing one of the two X chromosomes. It's inactive genetically.

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Nucleoplasm

The fluid substance that fills the nucleus. It contains proteins, ribonucleoproteins, and various other molecules necessary for nuclear activities.

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Heterochromatin

Densely packed and inactive form of chromatin. It's often seen as clumps in the nucleus under a microscope.

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What's the significance of the sex chromatin being inactive?

It prevents the expression of an extra X chromosome in female cells, ensuring a balanced dosage of X-linked genes. This is important for normal development.

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Study Notes

Cell Cycle Control & Mitosis

  • The cell cycle is a series of events preparing a cell to divide into two daughter cells
  • Interphase includes three stages: G1 (growth), S (synthesis, DNA duplication), and G2 (preparations for mitosis)
  • Mitosis is a shorter period where the cell divides its nucleus and cytoplasm, producing two daughter cells
  • Cell growth occurs during G1 phase, restoring cell size to normal.
  • DNA is duplicated during S phase, doubling the cell's DNA complement.
  • G2 phase involves cell preparations for mitosis.

Nucleus and Phases of Cell Cycle

  • The nucleus contains DNA blueprints for cell structures and activities
  • It contains molecular machinery for DNA replication and RNA synthesis (rRNA, mRNA, tRNA)
  • The nucleus does not produce proteins; it imports them from the cytoplasm
  • The nucleus has a nuclear envelope, chromatin, nucleolus and nuclear matrix
  • The nuclear envelope is made of two membranes making a perinuclear cisterna
  • Nuclear pores allow substance transport between the nucleus and cytoplasm
  • Chromatin is DNA wound around histone proteins (nucleosomes)
  • Heterochromatin is inactive/condensed, Euchromatin is active/less condensed
  • The nucleolus is involved in rRNA synthesis and ribosomal subunit assembly

Cytoskeletal Microtubules & Microfilaments & Motility

  • The cytoskeleton is a protein meshwork in animal cells
  • The cytoskeleton supports cell shape, maintains cell structures, and allows cell movement and organelle transport
  • Microtubules are hollow tubes that act as intracellular pathways
  • Centrosomes are nucleation sites for microtubules
  • Microtubules are dynamic structures, rapidly changing length (growth/shrinkage)
  • Motor proteins (dynein and kinesin, MAPs) assist in organelle transport along microtubules
  • Microtubules are involved in cell division (spindle apparatus), cilia and flagella movement
  • Microfilaments (actin filaments) are thin filaments, with a plus (fast-growing) and minus (slow-growing) end.
  • Contractile bundles are an important type of microfilaments, moving organelles during cell division and activities
  • Microfilaments organize the cell cortex, provide microvilli support, and are focal points for cell-extracellular matrix interactions.

Autophagy, Lysosomes, Peroxisomes & Cell Inclusions

  • Lysosomes are membrane-bound organelles containing hydrolytic enzymes for intracelluar digestion
  • Substances for degradation reach lysosomes through phagosomes, pinocytotic vesicles, and autophagosomes
  • Autophagy is a self-degredative process, removing damaged organelles, proteins, and other cellular components
  • Autophagy responds to stress and physiological conditions such as starvation, hyperthermia, and hypoxia.
  • Proteasomes are small organelles that degrade proteins.
  • Peroxisomes are organelles containing oxidative enzymes for specific metabolic processes.
  • Inclusions are non-living components of the cell like glycogen, lipids, pigments, that have no metabolic activity.

Cell Cycle Control & Mitosis

  • The cell cycle is a tightly regulated process.
  • Cyclins and cyclin-dependent kinases (CDKs) control the cell cycle by ensuring that the cell cycle proceeds through its phases in an ordered and controlled way.
  • Checkpoints ensure that events are meticulously completed
  • Factors that cause cell entry into the cycle (example: mechanical force or injury to the tissue) can cause the release of ligands to the cell
  • Proto-oncogenes are genes that control the cell's proliferation, which must be very strictly regulated, so that uncontrolled cell proliferation does not happen
  • Mutations in proto-oncogenes lead to oncogenes which can cause cancer.

Meiosis

  • Meiosis is a special type of cell division
  • It produces gametes (sex cells) with half the chromosome number of the parent cell.
  • Meiosis contains two phases: Meiosis I and Meiosis II.
  • Meiosis I involves reductional division, separating homologous chromosomes
  • Meiosis II involves equatorial division(similar to mitosis), separating sister chromatids
  • Meiosis ensures genetic variation through recombination (crossing over)
  • Results in four daughter cells with unique combinations of chromosomes.

Gene Expression 2: RNA Transcription and Genetic Code

  • Translation is the process of converting mRNA codons into an amino acid sequence.
  • The genetic code defines the relationship between codons and amino acids.
  • The genetic code is degenerate, meaning multiple codons can code for the same amino acid.
  • mRNA, tRNA, rRNA and ribosomes are necessary for protein synthesis.
  • Initiation, elongation, and termination are the three main stages in the protein biosynthesis
  • Different translation initiation factors are necessary for eukaryotic cells
  • Specific aminoacyl-tRNA synthetases charge tRNA molecules with the appropriate amino acids
  • During protein elongation, the ribosome moves along the mRNA, adding amino acids to the growing polypeptide chain.
  • Stop codons signal termination of protein synthesis
  • Proteins undergo maturation to achieve their final, active form.

Intercellular Junctions

  • Intercellular junctions are specialized areas where cells come in close contact with each other.
  • These structures are crucial for maintaining tissue integrity and function.
  • Anchoring junctions (zonula and macula adherens): Provide mechanical stability
  • Occluding junctions (zonula occludens) form an impermeable barrier.
  • Communicating junctions (gap junctions) allow small molecules to pass between cells.

Protein Folding, and Post-translational Modification

  • Misfolded proteins are harmful, so cells have quality control mechanisms for proper protein folding (chaperones).
  • Proteins are post-translationally modified to activate/inactivate/regulate their function
  • Post translational modifications include proteolysis (cleavage), phosphorylation, glycosylation, and oxidation.

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Description

Test your knowledge of the cell cycle and mitosis processes. This quiz covers interphase stages, functions of the nucleus, and the role of DNA during cell division. Understand the journey of a cell from growth to division and the importance of each phase.

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