Biology Chapter 6: A Tour of the Cell

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Questions and Answers

What causes amoeboid movement in cells?

Interaction of actin filaments with myosin

What drives cytoplasmic streaming in plant cells?

Myosin motors interacting with actin filaments

What are the motor proteins that move the microfilaments in muscle?

Myosin

What are two functions of intermediate filaments?

<ol> <li>Maintenance of cell shape (tension-bearing elements), 2. Anchorage of nucleus and certain other organelles</li> </ol> Signup and view all the answers

What are three functions of the cell wall?

<ol> <li>Protects the plant cell, 2. Maintains its shape, 3. Prevents excessive uptake of water</li> </ol> Signup and view all the answers

What is the relatively thin and flexible wall secreted first by a plant cell?

Primary cell wall Signup and view all the answers

What is the composition of the cell wall?

Microfibrils made of cellulose embedded in a matrix of polysaccharides and proteins Signup and view all the answers

What is the middle lamella and where is it found?

A thin layer of sticky polysaccharides called pectins located between the primary walls of adjacent cells Signup and view all the answers

Explain the deposition of a secondary cell wall.

It has a strong and durable matrix that affords the cell protection and support. Signup and view all the answers

What are the intercellular junctions between plant cells?

Plasmodesmata Signup and view all the answers

What can pass through plasmodesmata?

Cytosol Signup and view all the answers

What is the difference between magnification and resolution?

Magnification is the ratio of an object's image size to its real size. Resolution is a measure of the clarity of the image; it is the minimum distance two points can be separated and still be distinguished as two points. Signup and view all the answers

What is considered a major disadvantage of electron microscopes?

The methods used to prepare the specimen kill the cells. Signup and view all the answers

What does scanning electron microscopy (SEM) provide?

3-D component of the specimen image. Signup and view all the answers

What is transmission electron microscopy (TEM)?

This type of microscopy profiles a thin section of a specimen, resulting in various views of the cells prepared. Signup and view all the answers

Which organelles are the smallest ones isolated in cell fractionation?

Ribosomes. Signup and view all the answers

Which two domains consist of prokaryotic cells?

Bacteria and Archaea. Signup and view all the answers

Describe the location of DNA in prokaryotic and eukaryotic cells.

In a eukaryotic cell, most of the DNA is in an organelle called the nucleus, which is bounded by a double membrane. In a prokaryotic cell, the DNA is concentrated in a region that is not membrane enclosed, called a nucleoid. Signup and view all the answers

What is the structure of a cell wall?

Rigid structure outside the plasma membrane. Signup and view all the answers

What is the function of the plasma membrane?

Membrane enclosing the cytoplasm. Signup and view all the answers

What is the nucleoid?

Region where the cell's DNA is located (not enclosed by a membrane). Signup and view all the answers

What does a bacterial chromosome carry?

Carries genes in the form of DNA. Signup and view all the answers

What is the cytoplasm?

Interior of cell. Signup and view all the answers

What are flagella?

Locomotion organelles of some bacteria. Signup and view all the answers

Why are cells so small?

Cells are small because a high surface-to-volume ratio facilitates the exchange of materials between a cell and its environment. Signup and view all the answers

What are microvilli and how do they relate to the function of intestinal cells?

Microvilli are long, thin projections from the cell surface, which increase surface area without an appreciable increase in volume. Signup and view all the answers

Describe the nuclear envelope.

The nuclear envelope encloses the nucleus, separating its contents from the cytoplasm. It is a double membrane. Signup and view all the answers

What is the nuclear lamina?

The netlike array of protein filaments that maintains the shape of the nucleus. Signup and view all the answers

What are the two components of chromatin?

Chromatin is composed of proteins and DNA. Signup and view all the answers

When are the nucleoli visible and what is assembled there?

Nucleoli are visible in a nondividing nucleus in cells active, and proteins imported from the cytoplasm are assembled with rRNA into large and small subunits of ribosomes. Signup and view all the answers

What is the function of ribosomes?

Ribosomes are the cellular components that carry out protein synthesis. Signup and view all the answers

What are free ribosomes?

Suspended in cytosol. Produce protein that function within the cytosol. Signup and view all the answers

What are bound ribosomes?

Attached to the outside of endoplasmic reticulum or nuclear envelope. Produce proteins for insertion into membranes. Signup and view all the answers

List all the structures of the endomembrane system.

Nuclear envelope, Endoplasmic reticulum, Golgi apparatus, Lysosomes, Peroxisomes, Vesicles, Vacuoles, Plasma membrane. Signup and view all the answers

What is the lumen of the endoplasmic reticulum?

The cavity or cisternal space within the ER. Signup and view all the answers

List and describe three major functions of the smooth ER.

<ol> <li>Synthesis of lipids; 2. Detoxification of drugs and poisons; 3. Storage of calcium ions.</li> </ol> Signup and view all the answers

Why does alcohol abuse increase tolerance to other drugs such as barbiturates?

Alcohol and many other drugs induce the proliferation of smooth ER and its associated detoxification enzymes, increasing the rate of detoxification. Signup and view all the answers

What does the rough ER do with secretory proteins?

The ER membrane keeps them separate from proteins produced by free ribosomes and wraps them in vesicles to depart. Signup and view all the answers

What is a lysosome?

A membranous sac of hydrolytic enzymes that an animal cell uses to digest macromolecules. Signup and view all the answers

What happens in the process of phagocytosis?

Food vacuoles formed by engulfing smaller organisms or food particles fuse with lysosomes for digestion. Signup and view all the answers

Describe the process of autophagy.

During autophagy, a damaged organelle is surrounded by a double membrane, and a lysosome fuses with it to digest the material. Signup and view all the answers

What happens in Tay-Sachs disease?

A lipid-digesting enzyme is missing or inactive, leading to an accumulation of lipids in the brain. Signup and view all the answers

What are food vacuoles?

Vacuoles formed by phagocytosis. Signup and view all the answers

What are contractile vacuoles?

They pump excess water out of the cell. Signup and view all the answers

What do central vacuoles in plants do?

They develop by coalescence of smaller vacuoles and play a major role in the growth of plant cells. Signup and view all the answers

What is an endosymbiont?

A cell living within another cell. Signup and view all the answers

What is the endosymbiont theory?

It states that an early ancestor of eukaryotic cells engulfed a prokaryotic cell, merging into a single organism over time. Signup and view all the answers

What is the function of the mitochondria?

They are the sites of cellular respiration, generating ATP by extracting energy from nutrients. Signup and view all the answers

What is the function of chloroplasts?

Chloroplasts are sites of photosynthesis, converting solar energy into chemical energy. Signup and view all the answers

Why is the inner membrane of the mitochondria highly folded?

To increase surface area, enhancing the productivity of cellular respiration. Signup and view all the answers

What is the important role played by peroxisomes?

They contain enzymes that remove hydrogen atoms from substrates, producing hydrogen peroxide, which quickly degrades. Signup and view all the answers

What is the cytoskeleton?

A network of fibers extending throughout the cytoplasm. Signup and view all the answers

What are the three roles of the cytoskeleton?

<ol> <li>Maintenance of cell shape; 2. Mechanical support; 3. Cell motility.</li> </ol> Signup and view all the answers

Name the three main types of fibers that make up the cytoskeleton.

Microtubules, Microfilaments, Intermediate Filaments. Signup and view all the answers

What are four functions of microtubules?

<ol> <li>Maintenance of cell shape; 2. Cell motility; 3. Chromosome movement in cell division; 4. Organelle movement.</li> </ol> Signup and view all the answers

What is another name for centrosomes?

Microtubule-organizing center. Signup and view all the answers

What is the organization of microtubules in a centriole?

Two centrioles are at right angles to each other and each is made up of nine sets of three microtubules. Signup and view all the answers

Compare and contrast cilia and flagella.

Cilia and flagella are both microtubule-containing extensions, but differ in their beating patterns. Signup and view all the answers

How do motor proteins called dyneins cause movement of cilia?

Dyneins cause bending and movement, with ATP providing energy for these changes. Signup and view all the answers

What are three examples of movements that involve microfilaments?

<ol> <li>Muscle cell contraction; 2. Cell division; 3. Amoeboid movement.</li> </ol> Signup and view all the answers

Study Notes

Introduction to Cell Study

Robert Hooke first described cells in 1665 using oak tree cork.
Anton van Leeuwenhoek improved lens crafting, revealing a microscopic world.
Magnification measures size ratio of image to object; resolution indicates image clarity by showing the smallest distance two points remain distinct.

Microscopy Techniques

Electron microscopes allow detailed viewing of cell structures but require specimen preparation that kills cells.
Scanning electron microscopy (SEM) provides three-dimensional images of specimens.
Transmission electron microscopy (TEM) reveals thin sections of cells for various views.

Cell Structure and Organization

Cell fractionation separates cellular components through centrifugation, isolating organelles, with ribosomes being the smallest.
Prokaryotic cells belong to two domains: Bacteria and Archaea.
Eukaryotic cells contain DNA in a nucleus; prokaryotes have DNA in a non-membrane-bound nucleoid.

Cellular Components

The cell wall is a rigid structure outside of the plasma membrane.
The plasma membrane encloses the cytoplasm, regulating material exchange.
Flagella serve as locomotion organelles in some bacteria.

Cell Size and Surface Area

High surface-to-volume ratio is crucial for material exchange, explaining smaller cell sizes.
Microvilli increase surface area in intestinal cells, enhancing nutrient absorption.

Nucleus and Genetic Material

The nuclear envelope, a double membrane, encases the nucleus and connects through the nuclear lamina for structural support.
Chromatin, composed of DNA and proteins, condenses into distinct chromosomes during cell division.
Nucleoli, visible in active cells, assemble ribosomal subunits from proteins and rRNA.

Ribosomes

Ribosomes synthesize proteins; can be free (in cytosol) or bound (attached to rough ER).
The endomembrane system includes nuclear envelope, ER, Golgi apparatus, lysosomes, and vacuoles.

Endoplasmic Reticulum (ER)

Rough ER has ribosomes and processes secretory proteins, while smooth ER synthesizes lipids, detoxifies drugs, and stores calcium ions.
Alcohol abuse leads to increased smooth ER, augmenting drug detoxification.

Lysosomes and Vacuoles

Lysosomes digest macromolecules using hydrolytic enzymes, maintaining an acidic pH.
Phagocytosis and autophagy are processes where lysosomes recycle cellular components.
Food vacuoles are formed by phagocytosis, while contractile vacuoles expel excess water.

Plant Cell Vacuoles

Central vacuoles store inorganic ions and play a role in plant cell growth, absorbing water to enlarge.

Endosymbiont Theory

The endosymbiont theory posits that eukaryotic cells evolved from engulfed prokaryotes, explaining mitochondria and chloroplasts' double membranes and DNA.

Energy Organelles

Mitochondria conduct cellular respiration, converting nutrients into ATP.
Chloroplasts perform photosynthesis, turning sunlight into chemical energy.

Cytoskeleton

Cytoskeleton maintains cell shape, provides mechanical support, and facilitates cell movement.
Composed of microtubules, microfilaments, and intermediate filaments, each serving specific roles.

Fiber Functions

Microtubules assist in maintaining shape, cell motility, and movement of chromosomes.
Microfilaments enable muscle contraction through myosin interactions and support amoeboid movement.
Intermediate filaments provide structural stability and anchor organelles.

Cilia and Flagella

Cilia and flagella are microtubule-containing structures that differ in motion patterns, with cilia performing a rowing motion and flagella an undulating motion.

Peroxisomes

Peroxisomes contain enzymes for oxidation reactions, producing hydrogen peroxide, which is quickly broken down.

Plant Cell Wall Structure

The cell wall protects, maintains shape, and prevents excess water uptake.
Composed of cellulose microfibrils, primary and secondary walls, and pectin-rich middle lamella connecting adjacent cells.

Studying That Suits You

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Description

Explore the fundamentals of cell biology through flashcards covering key concepts from Chapter 6. Learn about the history of cell discovery, including contributions from Robert Hooke and Anton van Leeuwenhoek. This quiz will deepen your understanding of cell magnification and resolution.