Life Sciences Unit II

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Questions and Answers

What happens during the spindle checkpoint?

New nuclei begin to form.

Sister chromatids separate from each other.

The cell checks if all chromosomes are correctly attached. (correct)

Chromosomes align at the metaphase plate.

How do microtubules contribute to the stability of the spindle?

They form the membrane around the nucleus.

They attach to chromosomes from the same pole.

They grab on to microtubules from the opposite pole. (correct)

They pull chromosomes apart.

What is the role of motor proteins during mitosis?

To initiate cytokinesis by forming the cell membrane.

To break down the mitotic spindle.

To walk along microtubules and carry chromosomes or other microtubules. (correct)

To help chromosomes align at the metaphase plate.

What occurs in anaphase?

Sister chromatids are pulled towards opposite ends of the cell. Signup and view all the answers

Which event signifies the start of cytokinesis?

Division of the cytoplasm to form two new cells. Signup and view all the answers

What happens during telophase?

The cell prepares for the formation of two new nuclei. Signup and view all the answers

What best defines the metaphase plate?

A plane where chromosomes are aligned in preparation for division. Signup and view all the answers

How is the mitotic spindle disassembled during telophase?

By breaking down its building blocks. Signup and view all the answers

What characterizes the internal environment of lysosomes?

Acidic pH of approximately 4.5-5.0 Signup and view all the answers

Which organelle is primarily responsible for organizing microtubules?

Centrosome Signup and view all the answers

What is a primary function of vacuoles in plant cells?

Storage of water and solutes Signup and view all the answers

During which phase of mitosis do chromosomes line up at the metaphase plate?

Metaphase Signup and view all the answers

Which best describes the main function of centrioles in relation to cilia and flagella?

Formation of basal bodies Signup and view all the answers

What occurs during the anaphase stage of mitosis?

Chromosomes are pulled to opposite ends of the cell Signup and view all the answers

Which of the following is NOT a characteristic of lysosomes?

Formation of spindle fibers Signup and view all the answers

What is the primary purpose of the mitotic spindle during mitosis?

To separate chromosomes Signup and view all the answers

What key process occurs during cytokinesis?

Cell divides into two daughter cells Signup and view all the answers

Which structure is essential for organizing chromosomes during mitosis?

Centrosome Signup and view all the answers

During which phase do chromosomes become more condensed and the nuclear envelope breaks down?

Late prophase Signup and view all the answers

What happens to the nucleolus during prophase?

It disappears Signup and view all the answers

What are sister chromatids connected by?

Centromere Signup and view all the answers

Which of the following structures begins to form in early prophase?

Mitotic spindle Signup and view all the answers

What are microtubules that bind to chromosomes during mitosis called?

Kinetochore microtubules Signup and view all the answers

What primarily occurs at the checkpoints during mitosis?

Verification of the cell's readiness for division Signup and view all the answers

Study Notes

Unit II - Lecture 8

This lecture covers fundamental life sciences topics, crucial for quizzes and tests.
All slides are important for assessment.

Lysosome

Specialized membrane-bound vesicles, primarily in animal cells.
Contain hydrolytic enzymes to break down biomolecules.
Structurally, dense granular, enclosed by a lipid bilayer.
Internal environment has an acidic pH (4.5-5.0), optimal for enzymes.
- Autophagy: degrades worn-out cellular components.
- Endocytosis: degrades extracellular substances engulfed by the cell.
- Exocytosis: expels enzymes, aids in breaking down extracellular material.
- Often involved in white blood cell function.

Lysosome Enzymes

Lysosomes contain numerous hydrolases (enzymes).
Approximately 40 distinct varieties, categorized by substrates.
- Proteases: hydrolyze proteins, creating amino acids.
- Lipases: hydrolyze fats into fatty acids and glycerol.
- Amylases: hydrolyze carbohydrates into simpler sugars.
- Nucleases: hydrolyze nucleic acids (DNA/RNA).
- Phosphoric Acid Monoesters: hydrolyze phosphoric acid esters.

Why Lysosomes are Known as Suicidal Bags

Lysosomes have a potent arsenal of hydrolytic enzymes.
Primary function: degrade/recycle cellular components (extraneous or aged).
Vulnerability: Enzymes can rupture lysosomes, releasing them into cytoplasm, damaging the cell (autolysis).
Important for cellular health/waste removal, but poses risk of cell self-destruction.

Vacuoles

Membrane-bound organelles, in plants, fungi, some protists, animals, and bacteria.
Compartments containing water, inorganic/organic molecules, and enzymes.
Functions:
- Isolating harmful materials.
- Containing waste/small molecules/water (especially in plants).
- Maintaining turgor pressure (shape/buoyancy for plants).
- Maintaining an acidic internal pH.
- Exporting unwanted substances.
- Supporting plant structures (leaves/flowers).
- Storing proteins needed for germination in seeds.

Centrosome and Centriole

Centrosome: Organelle containing two centrioles.
Centrioles: Membraneless cylindrical structures.
Surrounded by amorphous pericentriolar material (centrosphere/kinoplasm/cytocentrum).
Commonly called "diplosomes."
No internal compartment.
Found in animal cells, except amoeba.
Absent in higher plants, but found in some stages of certain plants' life cycles.

Centriole Function

Involved in cell division (mitosis and meiosis).
Help organize microtubules.
Involved in the positioning of microtubules.
Can transform into basal bodies (forming cilia/flagella).

Chromosomes

23 pairs
One from each parent
Same length, same genes in the same position
Chromosomes from father & mother are designated

Homologous Chromosomes

Chromosomes having similar structures
Same length.
Same genes.
Same position.

Alleles

Specific form of a gene.
Responsible for variations in expressed genes.
Occur in pairs.

Mutations and Allele Frequencies

Mutations in genes can create new phenotypes (like different eye colors).
Allele frequency shifts over time, but some alleles remain dominant.

Cell Division (Mitosis)

Stages: Interphase, Prophase, Metaphase, Anaphase, Telophase, Cytokinesis.
Process where somatic cells divide to produce two genetically identical diploid cells.
Chromosome number remains the same.

Cell Division (Meiosis)

Process where sex cells divide to produce four genetically unique haploid gametes or cells.
Chromosome number is halved.
Stages: Prophase I, Metaphase I, Anaphase I, Telophase I, Prophase II, Metaphase II, Anaphase II, Telophase II, and Cytokinesis.

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This quiz covers key topics from Life Sciences Unit II, focusing on lysosomes and their functions in cell biology. You'll explore the structure, enzymes, and processes like autophagy and endocytosis crucial for understanding cellular mechanisms. Prepare to test your knowledge on these fundamental concepts.

Life Sciences Unit II - Lecture 8

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