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Questions and Answers
Who discovered cells by examining a piece of cork?
What does the first postulate of cell theory state?
Which of the following scientists established that all animals are composed of cells?
Which postulate of cell theory disproved the idea of spontaneous generation?
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What did Matthias Jacob Schleiden contribute to cell theory?
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What was one of the key advancements made by Anton Van Leeuwenhoek?
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Which statement about cells is true according to cell theory?
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In what year did Robert Brown discover the nucleus in plant cells?
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What is the primary function of the cell membrane?
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The nucleus is responsible for directing all the cell's activities.
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What are the primary components of cytoplasm?
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The ______ serves as the site of ribosome synthesis within the nucleus.
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Match the following cell structures with their primary functions:
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What is the primary function of the rough endoplasmic reticulum?
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What type of environmental condition do vacuoles typically maintain?
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Lysosomes are responsible for protein synthesis in cells.
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The Golgi apparatus modifies, sorts, and packages __________ synthesized by the cells.
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Match the following organelles with their respective functions:
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Study Notes
Cell Theory
- Proposed in the mid-1800s
- One of the basic principles of biology
- Three main postulates:
First Postulate: Cell as the Basic Unit of Life
- All living organisms are composed of at least one cell
- Cells are the fundamental building blocks of life
- Examples: Unicellular organisms (Bacteria) and multicellular organisms (Animals)
- Cell movement indicates life:
- Organelles move within a living cell
- Dissipation of protoplasm indicates cell death (Robert Hooke)
- Movement of bacteria within a cell indicates life (Anton van Leeuwenhoek)
Second Postulate: All Living Organisms are Composed of Cells
- A collaboration between Matthias Schleiden (German Botanist) and Theodor Schwann (German Physiologist)
- Schleiden recognized Robert Brown's discovery of the nucleus in 1833
- Schleiden established that plant cells are the basic unit of plant life (1838)
- Schwann correlated his findings with Schleiden's and confirmed that animals are composed of cells
Third Postulate: New Cells are Created from Preexisting Cells
- Cells arise only from existing cells
- Disproved the theory of spontaneous generation which suggested life arises from non-living matter
- Examples: Cell division and fertilization
Development of Cell Theory
- 1590: Zacharias Janssen invented the primitive microscope with help from his father, Hans
- 1663-1665: Robert Hooke viewed thin slices of cork and discovered "cells"
- 1665-1676: Marcello Malpighi and Nehemiah Grew contributed to early cell studies
- 1670-1683: Anton van Leeuwenhoek improved the microscope, magnifying objects up to 270x diameters.
Cell Membrane
- Outermost layer protecting the cell.
- Controls the exchange of essential components.
- Composed of a phospholipid bilayer (double layer of fats and proteins).
- Controls the entry and exit of materials into and out of the cell.
- Lipids like cholesterol can pass through due to its hydrophobic interior.
- Polar substances cannot cross independently as they cannot penetrate the hydrophobic interior.
Cytoplasm
- Area within the cell containing organelles.
- Primarily composed of water, proteins, and salts.
- Organelles are suspended in a gel-like solution called cytosol, containing water and ions.
- Predominantly made up of water, it contains macromolecules and smaller organic molecules.
- Contains enzymes that break down waste and enable metabolic reactions.
- Allows for cellular expansion and growth.
- Together with the cytoskeleton, determines cell shape and accommodates movement.
Nucleus
- Control center of the cell.
- Directs all the cell's activities and determines its appearance and function.
- Takes up 10% of the cell's volume.
- Contains the nucleolus, which is the site of ribosome synthesis.
- Holds the chromosomes containing DNA (deoxyribonucleic acid), the genetic material of an organism.
Endomembrane System
- Network of structures involved in adaptation, wrapping, and protein transfer across the cell.
- Functions as a depository of nutrients and a disintegrator of harmful organisms.
Endoplasmic Reticulum
- Transports molecules across the cytoplasm and assembles new lipids for export.
- Rough or granular ER: synthesizes and modifies proteins. Plays a significant role in forming plasma membrane proteins and proteins outside the cell. Has a rough appearance due to ribosomes attached to it.
- Smooth or agranular ER: incorporates proteins into cisternae and transports them across the cytoplasm. Allows for the synthesis of fatty acids and phospholipids.
- Abundant in liver cells, where it detoxifies hydrophobic chemicals.
Ribosomes
- Involved in providing a frame for protein synthesis.
- Sites of protein production.
- Discovered by G.E.Palade in 1952.
- Present in prokaryotic and eukaryotic cells.
Vacuoles
- Fluid-filled vesicle enclosed by a membrane.
- Has a selective membrane allowing water passage but retaining smaller molecules.
- Stores chemicals within cells.
- Acidic environment.
Lysosomes
- Serve as digestion slots for expiring or useless cellular materials.
- Known as the cell's "suicide bags" due to their ability to self-destruct to protect other organelles from poisons.
Peroxisomes
- Disintegrate proteins and accommodate the breakdown of fatty acids.
- Protect the cell from damage caused by reactive oxygen species (ROS) molecules.
- ROS molecules are byproducts of normal cellular metabolism.
Golgi Apparatus
- Observed as stacks of flat frameworks holding several sacs of secretory granules.
- Functions as the manufacturer and shipping center of the cell.
- Modifies, sorts, and packages macromolecules synthesized by the cells.
Centrosomes
- Assists in arranging microtubules (hollow tubes of protein) for cell division.
- Enables microtubules to form part of the cell's cytoskeleton.
- Maintains cellular shape and stabilizes cell structure.
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Description
Explore the foundational principles of cell theory, proposed in the mid-1800s. This quiz covers the three main postulates that define cells as the basic unit of life and the composition of living organisms. Test your knowledge on key figures and discoveries that shaped our understanding of biology.
