Biology Chapter 4: Cell Structure and Microscopy

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Questions and Answers

What term did Robert Hooke use to describe the structures he observed in cork?

Cells (correct)

Chambers

Microorganisms

Animalcules

Which scientist concluded that all plants are made of cells?

Theodor Schwann

Anton van Leeuwenhoek

Mathias Schleiden (correct)

Rudolf Virchow

Which type of microscope allows for the observation of living cells?

Transmission electron microscope

Confocal microscope

Light microscope (correct)

Scanning electron microscope

What is the primary function of peroxisomes in a cell?

Oxidize organic molecules to produce hydrogen peroxide Signup and view all the answers

What does the term 'resolution' refer to in microscopy?

The clarity of an image Signup and view all the answers

Who stated that all animals are made of cells?

Theodor Schwann Signup and view all the answers

What are the two internal compartments of mitochondria?

Intermembrane space and mitochondrial matrix Signup and view all the answers

Which of the following is true regarding the advancements in microscopy?

Scanning and transmission electron microscopes provide greater magnification and resolution. Signup and view all the answers

Which process do chloroplasts primarily facilitate?

Photosynthesis Signup and view all the answers

According to the endosymbiont theory, what is a shared characteristic between mitochondria and prokaryotes?

Independent DNA Signup and view all the answers

Rudolf Virchow is known for concluding what about cells?

Cells arise from existing cells. Signup and view all the answers

What was a significant contribution of Anton van Leeuwenhoek to microscopy?

Observing bacteria for the first time. Signup and view all the answers

What roles does the cytoskeleton play in maintaining cell function?

Support and movement of organelles Signup and view all the answers

Which of the following is NOT a component of the cytoskeleton?

Nucleolus Signup and view all the answers

How do mitochondria and chloroplasts exhibit evidence of endosymbiosis?

All of the above Signup and view all the answers

What specific process do mitochondria primarily facilitate?

Cellular respiration Signup and view all the answers

What role do integrins play in cell adhesion?

They attach the ECM to glycoproteins and facilitate communication. Signup and view all the answers

Which type of cell junction is specifically designed to prevent leakage between cells?

Tight junctions Signup and view all the answers

What is the primary component of plant cell walls?

Cellulose Signup and view all the answers

Which type of junction allows for direct communication through the cytoplasm between adjacent plant cells?

Plasmodesmata Signup and view all the answers

What primary role does the smooth endoplasmic reticulum (ER) serve?

Processes toxins and synthesizes lipids Signup and view all the answers

How can the functions of eukaryotic cell structures be categorized?

By genetic control, energy processing, structural support, and material handling. Signup and view all the answers

Which statement accurately describes the function of lysosomes?

They house enzymes that digest substances and damaged organelles. Signup and view all the answers

Which of the following correctly distinguishes eukaryotic cells from prokaryotic cells?

Eukaryotic cells have membrane-bound organelles. Signup and view all the answers

What is the main function of the Golgi apparatus?

To modify, sort, and ship cell products Signup and view all the answers

Which statement best describes the structural role of the cell wall in plants?

It provides mechanical support and maintains cell shape. Signup and view all the answers

How do vacuoles function within a plant cell?

They store molecules, waste, and assist in growth. Signup and view all the answers

What limitation does cell size typically face?

Reduced efficiency in nutrient acquisition and waste removal. Signup and view all the answers

Which of the following best describes the structural relationship of organelles in the endomembrane system?

They are interconnected structurally and functionally. Signup and view all the answers

What type of molecules does the rough endoplasmic reticulum primarily produce?

Membrane and secretory proteins Signup and view all the answers

Which function is attributed to the mitochondria in all cells?

Energy processing Signup and view all the answers

What is the significance of the central vacuole in plant cells?

It provides structural support and storage. Signup and view all the answers

What are the two main tenets of cell theory established in the mid-1800s?

All cells come from other cells. Signup and view all the answers

How is the large surface-to-volume ratio of small cells beneficial?

It facilitates more efficient exchange of materials. Signup and view all the answers

What characteristic distinguishes eukaryotic cells from prokaryotic cells?

Eukaryotic cells have membrane-enclosed organelles. Signup and view all the answers

Which of the following best describes the function of channel proteins in the plasma membrane?

They shield ions and hydrophilic molecules during transport. Signup and view all the answers

What is a primary function of the plasma membrane in cells?

To control the movement of substances in and out of the cell. Signup and view all the answers

Why do small nonpolar molecules typically cross the plasma membrane more easily than large polar molecules?

They can pass through the hydrophobic center of the membrane. Signup and view all the answers

What is a common feature of all cells, regardless of being prokaryotic or eukaryotic?

Existence of a plasma membrane. Signup and view all the answers

Which protein was first isolated and identified by biochemists in the 1940s?

Myosin Signup and view all the answers

What was the primary advancement that allowed scientists to visualize cytoskeletal proteins in living cells?

Application of fluorescence microscopy Signup and view all the answers

Which statement accurately describes the relationship between cell size and surface-to-volume ratio?

As cell size decreases, the surface-to-volume ratio increases. Signup and view all the answers

How do flagella differ from cilia in terms of their motion?

Flagella operate using a whiplike motion while cilia move more like synchronized oars. Signup and view all the answers

What is the primary disease associated with the lack of motor proteins in cilia and flagella?

Primary ciliary dyskinesia (PCD) Signup and view all the answers

What structural arrangement is characteristic of eukaryotic cilia and flagella?

9 + 2 arrangement Signup and view all the answers

How does the extracellular matrix (ECM) support animal cells?

By binding tissue cells and supporting the plasma membrane Signup and view all the answers

What was the significance of the findings regarding actin filaments in the decade following the initial discoveries?

Researchers identified actin filaments in various cell types. Signup and view all the answers

Which of the following best explains the symptoms associated with primary ciliary dyskinesia (PCD)?

Impaired movement of cilia, leading to respiratory issues Signup and view all the answers

Study Notes

Introduction

Improved microscopes and techniques have greatly expanded the understanding of cells.
In 1665, Robert Hooke used a rudimentary microscope to examine cork, observing structures resembling "little rooms" (cellulae in Latin), leading to the term "cell".
Anton van Leeuwenhoek, a few decades later, used more advanced microscopes to view various specimens, including blood, sperm, and pond water.
This chapter explores the cellular basis of life.

The Discovery of the Cell

Early Microscopes:
- Robert Hooke utilized a simple microscope to examine cork, discovering cells.
- Anton van Leeuwenhoek observed tiny living organisms in pond water (animalcules).
The Cell Theory:
- Matthias Schleiden concluded that all plants are composed of cells.
- Theodor Schwann stated that all animals are made of cells.
- Rudolf Virchow proposed that new cells arise from existing cells.

Microscopes Reveal the World of the Cell

Light microscopes display living cells.
Scanning and transmission electron microscopes reveal the ultrastructure of cells.
- Magnification is the increase in an object's image size compared to its actual size.
- Resolution is the ability of an instrument to distinguish between two nearby objects as separate.

Prokaryotic vs. Eukaryotic Cells

All cells have a plasma membrane, DNA, ribosomes, and cytosol.
Bacteria and Archaea are prokaryotic cells.
All other life forms are in domain Eukarya and have eukaryotic cells.
- Eukaryotic cells have a membrane-bound nucleus and numerous membrane-bound organelles with specialized functions.
- Prokaryotic cells are smaller and simpler than eukaryotic cells.

The Small Size of Cells

Most cells have a large surface area to volume ratio
This allows for efficient exchange of materials across the plasma membrane

The Nucleus and Ribosomes

The nucleus houses the cell's DNA, directing protein synthesis via messenger RNA.
Subunits of ribosomes are assembled in the nucleolus.
The processes occurring within the nucleus include DNA replication, RNA synthesis and ribosomal subunit assembly.

Ribosomes Make Proteins

Ribosomes are composed of ribosomal RNA and proteins.
Ribosomes synthesize proteins according to DNA's instructions.
Cells with high protein production have many ribosomes.

The Endomembrane System

Many eukaryotic cell membranes are part of the endomembrane system.
Organelles in this system interact in the synthesis, distribution, storage, and export of molecules.

The Endoplasmic Reticulum

The ER is a network of tubes and sacs.
Smooth ER synthesizes lipids and processes toxins.
Rough ER produces membranes and makes secretory proteins aided by ribosomes on its surface.

The Golgi Apparatus

The Golgi apparatus modifies, sorts, and ships cell products.
Products from the ER are processed and sent to other organelles or the cell surface through the Golgi.

Lysosomes

Lysosomes are digestive compartments breaking down ingested substances and damaged organelles.
They contain enzymes that break down these materials within the cell

Vacuoles

Vacuoles are large membrane-bound sacs with diverse functions.
Some protists have contractile vacuoles for water regulation.
Plant cells have a large central vacuole for storage, waste disposal, and growth.

A Review of the Structures Involved in Manufacturing and Breakdown

The endomembrane system organelles are interconnected structurally and functionally. The endomembrane system components include the ER, Golgi apparatus, lysosomes and vacuole

Energy-Converting Organelles

Mitochondria carry out cellular respiration.
Mitochondria have an outer and inner membrane. The intermembrane space is between the two membranes, while the mitochondrial matrix has the mitochondrial DNA, ribosomes, and enzymes involved in cellular respiration.
Chloroplasts carry out photosynthesis in plants and algae.
Chloroplasts contain thylakoids with chlorophyll, where light energy is converted into chemical energy, and stroma where the Calvin cycle occurs, yielding sugar.

Mitochondria and Chloroplasts Evolved Through Endosymbiosis

The endosymbiont theory states that mitochondria and chloroplasts were once prokaryotes that lived within larger cells.
Evidence includes their similar size to bacteria, their own DNA, and the way they are not synthesized within cells.

The Cytoskeleton and Cell Surfaces

Eukaryotic cells have a cytoskeleton which includes microfilaments, intermediate filaments and microtubules.
Functions include maintaining cell shape, anchoring and movement of organelles, amoeboid movement and muscle contraction.

Scientists Discovered the Cytoskeleton

In the 1940s, biochemists isolated actin and myosin from muscle cells.
In 1954, microscopy techniques showed how actin and myosin filaments interact during muscle contraction.
Actin filaments were later found in all cells during the next decade.

Cilia and Flagella

Eukaryotic cilia and flagella are made of microtubules arranged in a 9 + 2 pattern.
Flagella are longer and propel cells via an undulating (wave-like) motion.
Cilia are shorter and function like coordinated oars in movement.

The Extracellular Matrix

Animal cells secrete the extracellular matrix (ECM) which functions in support, binding cells together, communicating with the cytoskeleton, and supporting the plasma membrane.
The ECM is connected to the plasma membrane via membrane proteins called integrins.

Types of Cell Junctions

Neighboring cells adhere, interact, and communicate through specialized junctions.
Tight junctions form leakproof sheets binding cells together.
Anchoring junctions strengthen tissues by connecting cells.
Gap junctions allow small molecules and ions to pass between cells.

Cell Walls

Plant cells have a rigid cell wall primarily composed of cellulose, providing support and protection.
Plasmodesmata are cell junctions in plant cells that allow for the sharing of water, nutrients, and chemical signals between plant tissues.

Eukaryotic Cell Structures Grouped by Function

The structures of eukaryotic cells can be grouped into four functions: genetic control, manufacturing/distribution/breakdown, energy processing, and structural support/movement/communication.

Table 4.22 Eukaryotic Cell Structures and Their Functions

This table provides a comprehensive summary of eukaryotic cell structures, including their location, composition, and function. The table is divided into four main categories, covering their various functions within the cell (genetic control, manufacturing/distribution/breakdown, energy processing, and structural support/movement/communication).

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Description

Test your knowledge on cell structures, the history of microscopy, and the key scientists who contributed to the cell theory. This quiz covers important terms, functions, and theories related to cells, including endosymbiont theory and the functionalities of organelles. Perfect for biology students looking to reinforce their understanding of cellular biology.