History of the Cell: Janssen Microscope

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Questions and Answers

What is the primary function of the G1 checkpoint in the cell cycle?

To ensure DNA has been duplicated properly

To initiate chromosome condensation

To confirm the cell's size and nutrient availability (correct)

To regulate the spindle fiber attachment

Which of the following best describes sister chromatids?

Chromatids from different chromosomes

Two identical copies of a single chromosome (correct)

Paired chromosomes that are not identical

Chromatids that have exchanged genetic material

What event primarily occurs during the interphase of the cell cycle?

Cell division

Chromosome duplication (correct)

Chromosome separation

DNA repair mechanisms activation

In meiosis, what is the role of non-sister chromatids?

They exchange genetic material Signup and view all the answers

What role does the kinetochore play during cell division?

It is where spindle fibers attach Signup and view all the answers

Who were the inventors of the first primitive microscope?

Hans and Zacharias Janssen Signup and view all the answers

What did Robert Hooke discover by examining a slice of cork?

Cells Signup and view all the answers

What was Francesco Redi's conclusion regarding the theory of spontaneous generation?

Flies can reproduce only through eggs. Signup and view all the answers

What significant observation did Anton van Leeuwenhoek make with his microscope?

The circulation of corpuscles in capillaries. Signup and view all the answers

What important cell structure did Robert Brown discover in 1839?

Nucleus Signup and view all the answers

How did Theodore Schwann contribute to cell theory?

He concluded that all living things are made up of cells. Signup and view all the answers

What did Marcelo Malphigi contribute to the field of biology?

He observed blood capillaries in fish tails. Signup and view all the answers

Which scientist coined the term 'Animalcules'?

Anton van Leeuwenhoek Signup and view all the answers

What is the primary function of the nucleolus in a cell?

Producing and assembling ribosomes Signup and view all the answers

What structure is responsible for cell movement in certain cells?

Flagella Signup and view all the answers

Which organelle organizes microtubules within the cell?

Centriole Signup and view all the answers

What is the state of DNA when the cell is not dividing?

Chromatin in dispersed form Signup and view all the answers

How do animal cells communicate with each other?

Via gap junctions Signup and view all the answers

What type of cells are classified as gametes?

Haploid sex cells Signup and view all the answers

What is the main role of the central vacuole in mature plant cells?

Growth, storage, and sequestration of toxins Signup and view all the answers

Which structure directly connects the cytoplasm of adjacent plant cells?

Plasmodesma Signup and view all the answers

What is the primary function of mitochondria within eukaryotic cells?

Conversion of chemical energy of food to ATP Signup and view all the answers

Which type of microorganism is known to thrive in high saline environments?

Halophiles Signup and view all the answers

What organelle is responsible for the synthesis of membrane proteins and secretory proteins?

Rough Endoplasmic Reticulum Signup and view all the answers

Which structure is responsible for digestion within animal cells?

Lysosomes Signup and view all the answers

Which organelle converts light energy into chemical energy of sugars?

Chloroplasts Signup and view all the answers

What is the primary function of the Golgi Apparatus?

Storage and transport of macromolecules Signup and view all the answers

Which component of the cytoskeleton provides structure and shape to eukaryotic cells?

Intermediate Filaments Signup and view all the answers

Which of the following correctly describes peroxisomes?

Contain enzymes that oxidize fatty acids Signup and view all the answers

What occurs during the S phase of the cell cycle?

DNA synthesis and chromosome duplication Signup and view all the answers

Which phase ensures that DNA replication has been completed before proceeding?

G2 Phase Checkpoint Signup and view all the answers

What is the role of cyclins in the cell cycle?

To phosphorylate proteins and activate kinases Signup and view all the answers

In which phase do chromatin fibers become tightly coiled into discrete chromosomes?

Prophase Signup and view all the answers

What is the defining characteristic of the M phase in the cell cycle?

Nuclear and cytoplasmic division Signup and view all the answers

What happens at the metaphase checkpoint?

Chromosomes are checked for proper alignment Signup and view all the answers

What do cyclin-dependent kinases (CDKs) require for activation?

Presence of cyclin Signup and view all the answers

How are the daughter cells characterized after mitosis and cytokinesis?

Genetically identical to each other and the parental cell Signup and view all the answers

Study Notes

Early Microscope Development

Hans and Zacharias Janssen invented the first primitive microscope; they were glassmakers.
Allowed Robert Hooke to observe cork cells in 1665, magnifying 5-10 times using concave and convex lenses.
The invention drew attention from William Boreel, who informed the French King.

Key Discoveries in Cell Biology

Marcelo Malpighi, in 1660, first observed blood capillaries and the connection between arteries and veins, marking embryology's precursor.
Robert Hooke discovered cells in cork slices in 1665, coining the term "cell" due to their appearance resembling jail cells.
Francesco Redi challenged the theory of spontaneous generation in 1668 through experiments with rotting meat and fly reproduction.

Advancements in Microscopy

Anton van Leeuwenhoek, in 1683, created a practical microscope with magnifications up to 270 times; recognized "animalcules" including bacteria and yeasts.
Robert Brown (1839) identified the nucleus in plant cells, noting its opaque structure.

Cell Theory Contributions

Theodore Schwann and Matthias Jakob Schleiden developed the cell theory in 1839, stating that all living things are composed of cells and cell products.
Schleiden emphasized the cell nucleus's importance in cell division.

Eukaryotic Cells

Eukarya domain includes four kingdoms: Plantae (ferns, trees, flowers), Animalia (elephants, hippos, dogs, cats), Fungi (mushrooms, yeast), and Protista (Euglena, Paramecium).

Eukaryotic Organelles Functions

Nucleus: Site for DNA and RNA synthesis.
Smooth Endoplasmic Reticulum: Involved in lipid synthesis, carbohydrate metabolism, and detoxification; lacks ribosomes.
Rough Endoplasmic Reticulum: Synthesis of membrane and secretory proteins; ribosomes present.
Golgi Apparatus: Stacked sacs for macromolecule transport and lysosome formation.
Ribosomes: Sites of polypeptide synthesis; composed of rRNA and proteins.
Lysosomes: Enzymatic sac for digestion of nutrients and cellular debris.
Mitochondria: Convert food's chemical energy into ATP using oxygen.
Chloroplasts: Convert light energy into chemical energy in plant cells.
Plasma Membrane: Separates cell interior from the external environment.
Cytoplasm: Thick solution providing cell shape; includes cytosol (fluid portion).
Cytoskeleton: Composed of microtubules, microfilaments, and intermediate filaments for structure and transport.
Peroxisome: Contains enzymes for fatty acid and amino acid oxidation; produces and converts hydrogen peroxide.

Cell Division and Chromosome Structure

Somatic Cells: Body cells, diploid (46 chromosomes).
Gametes: Sex cells, haploid (23 chromosomes); produced via meiosis.
Chromosome structure includes P arm (short) and Q arm (long), centromere for sister chromatid binding.

Cell Cycle Phases

Cell Cycle: Sequence from one cell division to the next; typically lasts 24 hours.
Interphase: High metabolic activity; includes G1, S (DNA synthesis), and G2 phases.
G1 Phase: Cell growth and organelle increase; G1 checkpoint ensures size and nutrient adequacy.
S Phase: Chromosomes duplicate; each becomes double with sister chromatids.
G2 Phase: Preparation for division; checkpoint ensures DNA replication completion.
M Phase (Mitosis): Nuclear division creating genetically identical daughter cells followed by cytokinesis.

Regulation of the Cell Cycle

Checkpoints regulate the cell cycle, with three major checkpoints in G1, G2, and M phases.
Cyclins and CDKs: Cyclin-dependent kinases activate "go-ahead" signals at critical points in the cycle, forming MPF complexes to initiate mitosis.

Mitosis Process

Mitosis includes several stages:
- Prophase: Chromatin condenses, nucleoli disappear, and spindle fibers form.
- Cytokinesis: Division of the cytoplasm occurs post-mitosis, ensuring two distinct cells are formed.

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Description

Explore the groundbreaking contributions of Hans and Zacharias Janssen in the invention of the primitive microscope that revolutionized cell observation. Learn about their impact on the field of microscopy and how their work influenced scientists like Robert Hooke and Marcelo Malpighi in the 17th century.