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Questions and Answers
What did Robert Hooke observe when examining a thin slice of cork?
What did Robert Hooke observe when examining a thin slice of cork?
Robert Hooke used a microscope created by another scientist to view the cork cells.
Robert Hooke used a microscope created by another scientist to view the cork cells.
False (B)
What does the Latin word 'cell' mean?
What does the Latin word 'cell' mean?
a little room
The outer layer of an onion bulb that is peeled off for observation is called the ________.
The outer layer of an onion bulb that is peeled off for observation is called the ________.
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Match the following terms with their descriptions:
Match the following terms with their descriptions:
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What is used is the given content to stain the onion peel before observation under a microscope?
What is used is the given content to stain the onion peel before observation under a microscope?
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Chlamydomonas, Paramoecium, and bacteria are all multicellular organisms
Chlamydomonas, Paramoecium, and bacteria are all multicellular organisms
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What is the main function of rough endoplasmic reticulum (RER)?
What is the main function of rough endoplasmic reticulum (RER)?
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Lysosomes are known for their role in energy production within the cell.
Lysosomes are known for their role in energy production within the cell.
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What unique feature do mitochondria possess that allows them to produce some of their own proteins?
What unique feature do mitochondria possess that allows them to produce some of their own proteins?
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What is the primary function of the plasma membrane?
What is the primary function of the plasma membrane?
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The __________ apparatus is involved in the packaging and dispatching of materials synthesized near the endoplasmic reticulum.
The __________ apparatus is involved in the packaging and dispatching of materials synthesized near the endoplasmic reticulum.
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All cells in a multicellular organism have the same shape and size.
All cells in a multicellular organism have the same shape and size.
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Match the following organelles with their primary functions:
Match the following organelles with their primary functions:
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Name the two scientists who presented the cell theory.
Name the two scientists who presented the cell theory.
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The fluid substance of the cell is called ______.
The fluid substance of the cell is called ______.
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Which of the following is an example of a unicellular organism?
Which of the following is an example of a unicellular organism?
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All cells have the same organelles performing the same functions, no matter what organism they are found in.
All cells have the same organelles performing the same functions, no matter what organism they are found in.
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Who discovered the nucleus and in what year?
Who discovered the nucleus and in what year?
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The movement of substances across the cell membrane from a region of high concentration to a region of low concentration is called ______.
The movement of substances across the cell membrane from a region of high concentration to a region of low concentration is called ______.
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Match the scientist with their discovery or contribution to cell biology:
Match the scientist with their discovery or contribution to cell biology:
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What process causes CO2 to move out of a cell?
What process causes CO2 to move out of a cell?
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Osmosis is the diffusion of any molecule through a selectively permeable membrane.
Osmosis is the diffusion of any molecule through a selectively permeable membrane.
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What term describes a solution where the water concentration is higher outside the cell than inside?
What term describes a solution where the water concentration is higher outside the cell than inside?
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If a cell is placed in a hypertonic solution, it will ______.
If a cell is placed in a hypertonic solution, it will ______.
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Match the solutions with the effect they have on a cell:
Match the solutions with the effect they have on a cell:
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What is the main component of a plant cell wall?
What is the main component of a plant cell wall?
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Plasmolysis occurs when a plant cell gains water due to osmosis.
Plasmolysis occurs when a plant cell gains water due to osmosis.
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Which type of microscope is needed to observe the structure of the plasma membrane?
Which type of microscope is needed to observe the structure of the plasma membrane?
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The process by which cells engulf food and other materials is known as ______.
The process by which cells engulf food and other materials is known as ______.
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What is the role of diffusion in the context of living cells?
What is the role of diffusion in the context of living cells?
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The cell wall allows cells to withstand changes in the surrounding medium, unlike ______ cells.
The cell wall allows cells to withstand changes in the surrounding medium, unlike ______ cells.
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Which of the following is NOT a function of the nucleus?
Which of the following is NOT a function of the nucleus?
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The nuclear membrane allows the passage of materials between the nucleus and cytoplasm.
The nuclear membrane allows the passage of materials between the nucleus and cytoplasm.
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What is the name given to the undefined nuclear region in prokaryotic cells?
What is the name given to the undefined nuclear region in prokaryotic cells?
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Match the following cell structures with their respective functions:
Match the following cell structures with their respective functions:
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The ______ is the fluid content enclosed by the plasma membrane and contains various cell organelles.
The ______ is the fluid content enclosed by the plasma membrane and contains various cell organelles.
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Describe the difference between prokaryotic and eukaryotic cells in terms of membrane-bound organelles.
Describe the difference between prokaryotic and eukaryotic cells in terms of membrane-bound organelles.
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Which of the following statements accurately describes chromosomes?
Which of the following statements accurately describes chromosomes?
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Viruses have a membrane similar to that of cells and can reproduce independently.
Viruses have a membrane similar to that of cells and can reproduce independently.
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What is the function of the cell membrane?
What is the function of the cell membrane?
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Study Notes
Robert Hooke's Observation of Cells
- Robert Hooke, in 1665, observed cork through a microscope, noticing compartments resembling a honeycomb.
- He named these compartments "cells," drawing from the Latin word for "a little room."
- This was a crucial moment in science, marking the first observation of living things as comprised of discrete units.
Living Organisms and Cells
- Living things consist of either single cells (unicellular) or multiple cells (multicellular).
- Examples of unicellular organisms include Chlamydomonas, Paramecium, and bacteria.
- Multicellular organisms, such as some fungi, plants, and animals, consist of many cells grouped together to form various body parts.
- All cells originate from pre-existing cells.
Observing Cells in Onion Peel
- To observe cells, a thin peel from an onion is prepared on a glass slide.
- Safranin solution is used to stain the cells for better visibility under a microscope.
- Onion cells are observed under different microscope magnifications to study structure.
Cell Shape and Structure
- Cells vary in shape and size depending on their specific function.
- Cells may change their shape (e.g., Amoeba) or have a fixed shape.
- Cells from various parts of a plant body might be different in structure.
- However, all cells display similarities in basic structural features.
Cell Theory
- The cell theory, proposed by Schleiden and Schwann in 1838-1839, states that all plants and animals are composed of cells, and the cell is the fundamental unit of life.
- Virchow (1855) expanded the theory by stating that all cells arise from pre-existing cells.
- Improved microscopes, including the electron microscope (1940), allowed further understanding of cells.
Cell Components
-
Plasma Membrane (Cell Membrane):
- The outer boundary of the cell, separating its internal contents from the external environment.
- Selectively permeable, regulating what enters and exits the cell.
- Allows movement of some substances (e.g., CO2, O2) via diffusion.
- Movement of water through the membrane is called osmosis.
- Osmosis depends on relative solute concentrations (hypotonic, isotonic, hypertonic solutions).
- The membrane is flexible and composed of lipids and proteins.
- Endocytosis allows cells to engulf material from their environment.
-
Cell Wall:
- Found in plant cells, fungi, and bacteria.
- Rigid outer layer outside the plasma membrane. Primarily composed of cellulose in plants.
- Provides structural support and prevents bursting in hypotonic environments.
- Can undergo plasmolysis (shrinkage) when cells lose water.
-
Nucleus:
- A central, typically spherical or oval structure in eukaryotic cells.
- Contains genetic material (DNA) organized as chromosomes.
- The nucleus directs cell activities and plays a role in reproduction.
- Surrounded by a double membrane (nuclear membrane) with pores.
- In some organisms (e.g., bacteria), the nuclear region is undefined (nucleoid).
-
Cytoplasm:
- The fluid contents of the cell, enclosed by the plasma membrane.
- Contains cell organelles, which perform various functions.
- Membrane-bound organelles are absent in prokaryotic cells.
-
Cell Organelles:
-
Endoplasmic Reticulum (ER):
- Network of membrane tubes and sheets, aids in transport of material.
- Rough ER (RER) has ribosomes for protein synthesis.
- Smooth ER (SER) synthesizes lipids and detoxifies substances.
-
Golgi Apparatus:
- Stacks of flattened membrane sacs. Modifies, packages, and transports cellular products
-
Lysosomes:
- Contain digestive enzymes to break down waste material and foreign substances.
- "Suicide bags" – can also digest the cell if damaged.
-
Mitochondria:
- "Powerhouses" of the cell, with inner folds that generate ATP (energy).
- Contain their own DNA and ribosomes for protein synthesis.
-
Plastids:
- Found only in plant cells.
- Chromoplasts (e.g., chloroplasts) contain pigments for photosynthesis.
- Leucoplasts store substances like starch.
-
Vacuoles:
- Storage sacs for liquids or solids.
- Larger in plant cells (central vacuole).
-
Endoplasmic Reticulum (ER):
Prokaryotic vs Eukaryotic Cells
- Prokaryotic cells lack a defined nucleus and membrane-bound organelles (e.g., bacteria).
- Eukaryotic cells have a defined nucleus and membrane-bound organelles (e.g., plants, animals).
Cell Division
- Cell division (mitosis) creates identical daughter cells for growth and repair.
- Cell division (meiosis) produces gametes with half the number of chromosomes.
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Description
Explore the foundational concepts of biology with a focus on Robert Hooke's groundbreaking observations of cells. Learn about the differences between unicellular and multicellular organisms, and discover how to prepare onion cells for microscopic observation. This quiz will test your understanding of the structural units of life.
