# Principles Of Biology I - Exam II - Chapters 6, 7, 8

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Pittsburg State UniversityPrinciples of Biology IFall, 2010 - Exam II - Chapters 6, 7, 8Dr. Wu

• 1.

### What is the minimum resolution of a Light Microscope (LM)?

• A.

20 nm

• B.

20 mm

• C.

20 µm

• D.

200 nm

• E.

200 µm

D. 200 nm
Explanation
1 m = 100 cm = 1000 mm = 1000000 µm = 1000000000 nm
A light microscope magnifies the image about 1000 times the size of the actual specimen. 200 µm is approximately the size of a small bacterium, most subcellular structures, or organelles, are too small to be resolved by a light microscope.

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• 2.

### Which type of microscope focuses a beam of electrons onto the surface of a specimen, providing images that look 3-d?

• A.

Transmission Electron Microscope

• B.

Scanning Electron Microscope

• C.

Light Microscope

• D.

Fischer Price Microscope

• E.

None of the above

B. Scanning Electron Microscope
Explanation
A scanning electron microscope focuses a beam of electrons onto the surface of a specimen, allowing for the generation of 3-dimensional images. This type of microscope is different from a transmission electron microscope, which focuses electrons through a specimen to create a 2-dimensional image. Light microscopes use visible light to create images, while the Fischer Price microscope is not a real type of microscope. Therefore, the correct answer is the scanning electron microscope.

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• 3.

### Which type of microscope focuses a beam of electrons through a specimen, and are used mainly to study the internal structure of cells?

• A.

Transmission Electron Microscope

• B.

Scanning Electron Microscope

• C.

Light Microscope

• D.

Fischer Price Microscope

• E.

None of the above

A. Transmission Electron Microscope
Explanation
A transmission electron microscope (TEM) focuses a beam of electrons through a specimen, allowing for high-resolution imaging of the internal structure of cells. This type of microscope uses electromagnetic lenses to magnify the image and has the ability to reveal details at the nanoscale level. In contrast, a scanning electron microscope (SEM) uses a focused beam of electrons to scan the surface of a specimen, providing detailed information about its topography. A light microscope, on the other hand, uses visible light to illuminate the specimen and is not capable of achieving the same level of resolution as an electron microscope. Fischer Price Microscope is not a valid type of microscope.

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• 4.

### What cell types are eukaryotic?

• A.

Bacteria, fungi, protists

• B.

Bacteria and archaea

• C.

Archaea and fungi

• D.

Protists, fungi, animals and plants

• E.

None of the above.

D. Protists, fungi, animals and plants
Explanation
The correct answer is protists, fungi, animals, and plants. This is because all of these cell types have a nucleus and other membrane-bound organelles, which are characteristics of eukaryotic cells. Bacteria and archaea, on the other hand, are prokaryotic cells and do not have a nucleus or membrane-bound organelles. Therefore, the correct answer is protists, fungi, animals, and plants.

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• 5.

### What cell types are prokaryotic?

• A.

Bacteria, fungi, protists

• B.

Bacteria and archaea

• C.

Archaea and fungi

• D.

Protists, fungi, animals and plants

• E.

None of the above.

B. Bacteria and archaea
Explanation
The correct answer is bacteria and archaea. Prokaryotic cells are characterized by the absence of a nucleus and membrane-bound organelles. Bacteria and archaea are the two domains of prokaryotes. Bacteria are single-celled organisms found in various environments, while archaea are also single-celled organisms but often live in extreme environments. Fungi, protists, animals, and plants are all examples of eukaryotic cells, which have a nucleus and membrane-bound organelles. Therefore, they are not prokaryotic.

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• 6.

### Prokaryotic cells:

• A.

Do not have a nucleus

• B.

Lack membrane-bound organelles

• C.

Contain DNA in a nucleus that is bounded by a membranous nuclear envelope

• D.

Have membrane-bound organelles

• E.

Contain DNA in an unbound region called the nucleoid

A. Do not have a nucleus
B. Lack membrane-bound organelles
E. Contain DNA in an unbound region called the nucleoid
Explanation
The correct answer is "Do not have a nucleus, lack membrane-bound organelles, contain DNA in an unbound region called the nucleoid." This answer accurately describes the characteristics of prokaryotic cells. Prokaryotic cells do not have a defined nucleus like eukaryotic cells, and their DNA is located in a region called the nucleoid, which is not surrounded by a membrane. Additionally, prokaryotic cells lack membrane-bound organelles, which are present in eukaryotic cells. Therefore, this answer correctly summarizes the unique features of prokaryotic cells.

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• 7.

### Eukaryotic cells:

• A.

Contain DNA in a nucleus that is bounded by a membranous nuclear envelope

• B.

Contain DNA in an unbound region called the nucleoid

• C.

Lack membrane-bound organelles

• D.

Have membrane-bound organelles

• E.

Do not have a nucleus

A. Contain DNA in a nucleus that is bounded by a membranous nuclear envelope
D. Have membrane-bound organelles
Explanation
Eukaryotic cells contain DNA in a nucleus that is bounded by a membranous nuclear envelope. This means that the DNA is enclosed within a membrane-bound structure called the nucleus. Additionally, eukaryotic cells have membrane-bound organelles, which are specialized compartments within the cell that perform specific functions. This distinguishes them from prokaryotic cells, which lack membrane-bound organelles.

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• 8.

### A phospholipid has a hydrophobic head and hydrophilic tails.

• A.

True

• B.

False

B. False
Explanation
A phospholipid has a hydrophilic head and hydrophobic tails. The head of a phospholipid molecule is attracted to water (hydrophilic), while the tails are repelled by water (hydrophobic). This unique structure allows phospholipids to form the basic building blocks of cell membranes, with the hydrophilic heads facing outward towards the watery environment and the hydrophobic tails facing inward, creating a barrier that separates the inside of the cell from the outside.

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• 9.

### What types of cellular organelles are present in animal cells but not plant cells?

• A.

Lysosomes

• B.

Nucleus

• C.

Mitochondrion

• D.

Cytoskeleton

• E.

Golgi apparatus

• F.

Flagella

• G.

Plasmodesmata

• H.

Centrioles

A. Lysosomes
F. Flagella
H. Centrioles
Explanation
Animal cells contain lysosomes, flagella, and centrioles, which are not present in plant cells. Lysosomes are responsible for breaking down waste materials and cellular debris. Flagella are whip-like structures that help in cell movement. Centrioles play a role in cell division and the formation of the spindle apparatus. These organelles are unique to animal cells and are not found in plant cells.

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• 10.

### What types of cellular organelles are present in plant cells but not animal cells?

• A.

Chloroplasts

• B.

Golgi apparatus

• C.

Plasmodesmata

• D.

Mitochondrion

• E.

Centrioles

• F.

Central vacuole and tonoplast

• G.

Cell wall

A. Chloroplasts
C. Plasmodesmata
F. Central vacuole and tonoplast
G. Cell wall
Explanation
Plant cells have several organelles that are not present in animal cells. Chloroplasts are one such organelle that is responsible for photosynthesis in plants. Plasmodesmata are small channels that connect plant cells and allow for communication and transport of molecules between them. The central vacuole and tonoplast are involved in storing water, nutrients, and waste products in plant cells. Lastly, plant cells have a cell wall, which provides structural support and protection. These organelles are unique to plant cells and are not found in animal cells.

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• 11.

### What cellular organelle is/are the genetic library(ies) and control center(s) of the cell?

• A.

The Cytoskeleton

• B.

Mitochondria & Chloroplasts

• C.

The Endomembrane System

• D.

Ribosomes

• E.

Nucleus

E. Nucleus
Explanation
The nucleus is the correct answer because it contains the genetic material, DNA, which serves as the genetic library of the cell. It also controls the activities of the cell by regulating gene expression and directing the synthesis of proteins. The nucleus is surrounded by a double membrane called the nuclear envelope, which separates the genetic material from the rest of the cell. Inside the nucleus, the DNA is organized into structures called chromosomes, which contain the genes that code for various traits and characteristics of the organism.

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• 12.

### What cellular organelles are the protein factories of the cell?

• A.

Lysosomes

• B.

The Golgi Apparatus

• C.

Vacuoles

• D.

Ribosomes

• E.

Mitochondria & Chloroplasts

D. Ribosomes
Explanation
Ribosomes are the protein factories of the cell. They are responsible for protein synthesis, where they read the genetic information from the DNA and use it to assemble amino acids into proteins. Ribosomes can be found in both prokaryotic and eukaryotic cells, and they are either free-floating in the cytoplasm or attached to the endoplasmic reticulum. Lysosomes, the Golgi apparatus, vacuoles, mitochondria, and chloroplasts have different functions within the cell but are not directly involved in protein synthesis.

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• 13.

### What cellular organelle consists of microtubules, actin and intermediate filaments?

• A.

The Cytoskeleton

• B.

Mitochondria

• C.

The Endomembrane System

• D.

Ribosomes

• E.

Extracellular structures

A. The Cytoskeleton
Explanation
The cytoskeleton is a cellular organelle that consists of microtubules, actin, and intermediate filaments. It provides structural support to the cell and helps in cell movement, cell division, and maintaining cell shape. Microtubules are responsible for maintaining cell shape and acting as tracks for intracellular transport. Actin filaments are involved in cell movement and muscle contraction. Intermediate filaments provide mechanical strength to the cell. Therefore, the cytoskeleton is the correct answer for the organelle consisting of microtubules, actin, and intermediate filaments.

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• 14.

### What cellular organelle is(are) the shipping and receiving center(s) for the cell?

• A.

Lysosomes

• B.

Vacuoles

• C.

Endoplasmic Reticulum

• D.

The Golgi Apparatus

• E.

Actin

D. The Golgi Apparatus
Explanation
The Golgi Apparatus is the correct answer because it acts as the shipping and receiving center for the cell. It receives proteins and lipids from the endoplasmic reticulum, modifies them, and then packages them into vesicles for transport to other parts of the cell or for secretion outside of the cell. It also receives materials from the cell membrane through endocytosis and sorts and processes them for recycling or degradation. Therefore, the Golgi Apparatus plays a crucial role in the intracellular transport and sorting of molecules, making it the shipping and receiving center of the cell.

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• 15.

### The nuclear envelope consists of what two membranes?

• A.

Lamina

• B.

Chromosomes

• C.

Chromatin

• D.

Pores

• E.

Nucleoli

A. Lamina
D. Pores
Explanation
The nuclear envelope which consists of two membranes is perforated with pores and lined by the nuclear lamina. It encloses the nucleus, separating it from the cytoplasm.

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• 16.

### Chromatin condenses to form discrete _______________?

chromosomes
Explanation
In the nucleus, DNA and proteins form genetic material called chromatin. Chromatin condenses to form discrete chromosomes.

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• 17.

### What is the primary function of nucleoli?

• A.

Enclose the nucleus, separating it from the cytoplasm

• B.

Chromosome secretion

• C.

Genetic material formation

• D.

Ribosome synthesis

D. Ribosome synthesis
Explanation
The primary function of nucleoli is ribosome synthesis. Nucleoli are small structures found within the nucleus of a cell. They are responsible for producing and assembling the components of ribosomes, which are essential for protein synthesis. Ribosomes are responsible for translating genetic information from the nucleus into functional proteins. Therefore, the correct answer is ribosome synthesis.

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• 18.

### Where can ribosomes be found in the cell?

• A.

Mitochondria

• B.

Cytosol (free)

• C.

The Golgi Apparatus

• D.

Outside of the endoplasmic reticulum or nuclear envelope (bound)

B. Cytosol (free)
D. Outside of the endoplasmic reticulum or nuclear envelope (bound)
Explanation
Ribosomes can be found in two different locations within the cell. They can be found freely floating in the cytosol, which is the fluid portion of the cytoplasm. Additionally, ribosomes can also be found bound to the outside of the endoplasmic reticulum or the nuclear envelope. This is where proteins are synthesized and processed before being transported to their final destinations within the cell or outside of it.

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• 19.

### What are some characteristics and functions of smooth ER (endoplasmic reticulum)?

• A.

Synthesize lipids

• B.

Membrane factory for the cell

• C.

Metabolize carbohydrates

• D.

Distributes transport vesicles

• E.

Stores calcium

• F.

Detoxifies poison

• G.

Has bound ribosomes, studding its surface

• H.

Lacks ribosomes

A. Synthesize lipids
C. Metabolize carbohydrates
E. Stores calcium
F. Detoxifies poison
H. Lacks ribosomes
Explanation
Smooth ER is responsible for synthesizing lipids, metabolizing carbohydrates, storing calcium, and detoxifying poisons. It does not have bound ribosomes, which are found on the surface of rough ER.

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• 20.

### What are characteristics and functions of rough ER (endoplasmic reticulum)?

• A.

Synthesize lipids

• B.

Membrane factory for the cell

• C.

Metabolize carbohydrates

• D.

Distributes transport vesicles

• E.

Stores Calcium

• F.

Detoxifies poison

• G.

Has bound ribosomes, studding its surface

• H.

Lacks ribosomes

B. Membrane factory for the cell
D. Distributes transport vesicles
G. Has bound ribosomes, studding its surface
Explanation
The rough ER is responsible for synthesizing lipids, acting as a membrane factory for the cell, and distributing transport vesicles. It also has bound ribosomes, which are studded on its surface and involved in protein synthesis.

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• 21.

### Endoplasmic reticulum (ER) accounts for what percentage of the total membrane in many eukaryotic cells?

• A.

>20%

• B.

>30%

• C.

>40%

• D.

>50%

• E.

>60%

D. >50%
Explanation
The endoplasmic reticulum (ER) is a network of membranes found in eukaryotic cells that is involved in various cellular processes. It is responsible for the synthesis and transport of proteins and lipids. The ER is an extensive and interconnected membrane system, making up more than 50% of the total membrane in many eukaryotic cells. This high percentage reflects the importance and significance of the ER in cellular functions.

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• 22.

### Smooth ER and Rough ER are the two distinct regions of endoplasmic reticulum (ER).

• A.

True

• B.

False

A. True
Explanation
Smooth ER and Rough ER are indeed two distinct regions of the endoplasmic reticulum. The smooth ER lacks ribosomes on its surface and is involved in lipid synthesis, detoxification, and calcium storage. In contrast, the rough ER is studded with ribosomes and is responsible for protein synthesis and processing. Therefore, the statement is true.

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• 23.

### What are functions of the Golgi Apparatus?

• A.

Metabolizes carbohydrates

• B.

Stores calcium

• C.

Modifies products of the endoplasmic reticulum (ER)

• D.

Synthesizes the production of proteins

• E.

Manufactures certain macromolecules

• F.

Sorts and packages materials into transport vesicles

C. Modifies products of the endoplasmic reticulum (ER)
E. Manufactures certain macromolecules
F. Sorts and packages materials into transport vesicles
Explanation
The Golgi Apparatus is responsible for modifying products of the endoplasmic reticulum (ER), manufacturing certain macromolecules, and sorting and packaging materials into transport vesicles. It plays a crucial role in the processing and packaging of proteins and lipids for transport to their final destinations within the cell or for secretion outside the cell. Additionally, the Golgi Apparatus is involved in the synthesis of certain macromolecules and the modification of proteins by adding sugars or lipids to them.

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• 24.

### The trans face is the "receiving" side of the Golgi apparatus and the cis face is the "shipping" side of the Golgi apparatus.

• A.

True

• B.

False

B. False
Explanation
The trans face of the Golgi apparatus is actually the "shipping" side, where the modified and packaged proteins are transported out of the Golgi. The cis face, on the other hand, is the "receiving" side, where proteins from the endoplasmic reticulum enter the Golgi for further processing. Therefore, the correct answer is false.

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• 25.

### Sacs of flattened membranous sacs are called ______________?

cisternae
Explanation
Sacs of flattened membranous sacs are called cisternae. Cisternae are a type of membrane structure found in cells, particularly in the endoplasmic reticulum and Golgi apparatus. They are responsible for the storage and transport of various molecules within the cell. The term "cisternae" refers to the flattened, interconnected sacs that make up these structures, allowing for efficient organization and compartmentalization of cellular processes.

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• 26.

### Lysosomes are the digestive compartments of the cell.

• A.

False

• B.

True

B. True
Explanation
Lysosomes are membrane-bound organelles found in animal cells that contain digestive enzymes. These enzymes help break down waste materials, cellular debris, and foreign substances that enter the cell. Lysosomes play a crucial role in cellular digestion and recycling. They fuse with other vesicles or organelles to digest their contents and release the breakdown products back into the cell for reuse. Therefore, it is correct to say that lysosomes are the digestive compartments of the cell.

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• 27.

### A lysosome is a membranous sac of hydrolitic enzymes that can digest what?

• A.

Food, by hydrolyzing proteins, fats, polysaccharides & nucleic acids (phagocytosis)

• B.

Damaged organelles and macromolecules (autophagy)

• C.

Ribosomes

• D.

Chromatin

A. Food, by hydrolyzing proteins, fats, polysaccharides & nucleic acids (phagocytosis)
B. Damaged organelles and macromolecules (autophagy)
Explanation
Lysosomes are membranous sacs that contain hydrolitic enzymes, which are capable of breaking down various substances. These enzymes can digest food particles by hydrolyzing proteins, fats, polysaccharides, and nucleic acids through a process called phagocytosis. Additionally, lysosomes also play a role in removing damaged organelles and macromolecules through a process called autophagy. Therefore, the correct answer is food, by hydrolyzing proteins, fats, polysaccharides & nucleic acids (phagocytosis), damaged organelles and macromolecules (autophagy).

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• 28.

### A food vacuole:

• A.

Is formed by phagocytosis

• B.

Is found in many freshwater protists and pumps excess water out of cells

• C.

Is found in many mature plant cells and holds organic compounds and water

A. Is formed by phagocytosis
Explanation
The central vacuole is usually the largest compartment in a plant cell, the rest of the cytoplasm is generally confined to a narrow zone between the vacuolar membrane (tonoplast) and the plasma membrane.

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• 29.

### A contractile vacuole:

• A.

Is formed by phagocytosis

• B.

Is found in many freshwater protists and pumps excess water out of cells

• C.

Is found in many mature plant cells and holds organic compounds and water

• D.

None of the above

B. Is found in many freshwater protists and pumps excess water out of cells
Explanation
A contractile vacuole is a structure found in many freshwater protists. Its main function is to pump excess water out of the cells. This is important because freshwater protists live in a hypotonic environment, meaning that water tends to flow into their cells. The contractile vacuole helps maintain osmotic balance by actively removing the excess water, preventing the cells from bursting. This mechanism is crucial for the survival of these organisms in their aquatic habitat.

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• 30.

### A central vacuole:

• A.

Is formed by phagocytosis

• B.

Is found in many freshwater protists and pumps excess water out of cells

• C.

Is found in many mature plant cells and holds organic compounds and water

• D.

None of the above

C. Is found in many mature plant cells and holds organic compounds and water
Explanation
The correct answer is "Is found in many mature plant cells and holds organic compounds and water." The central vacuole is a large membrane-bound organelle found in plant cells. It is responsible for storing water, nutrients, and waste materials. The central vacuole also helps maintain the turgor pressure in plant cells, which is important for cell stability and support. Additionally, it can store pigments and toxins, and play a role in plant growth and development.

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• 31.

### What are the characteristics and functions of mitochondria?

• A.

Present in almost all eukaryotic cells

• B.

Have a smooth outer membrane and an inner membrane folded into cristae

• C.

Present in almost all prokaryotic cells

• D.

Inner membrane consists of of two compartments: intermembrane space and mitochondrial matrix

• E.

Cristae present a large surface area for enzymes that synthesize ATP

• F.

Capture light energy

• G.

Used for energy conversion

A. Present in almost all eukaryotic cells
B. Have a smooth outer membrane and an inner membrane folded into cristae
D. Inner membrane consists of of two compartments: intermembrane space and mitochondrial matrix
E. Cristae present a large surface area for enzymes that synthesize ATP
G. Used for energy conversion
Explanation
Mitochondria are present in almost all eukaryotic cells and have a smooth outer membrane and an inner membrane folded into cristae. The inner membrane consists of two compartments: the intermembrane space and the mitochondrial matrix. The cristae provide a large surface area for enzymes that synthesize ATP, which is used for energy conversion. Therefore, mitochondria play a crucial role in energy production within cells.

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• 32.

### What are the primary components of chloroplasts?

• A.

Chromatin, cytosol

• B.

Thylakoids (stacked to form grana), stroma

• C.

Cisternae, chromatin

• D.

Thylakoids (stacked to form grana), cisternae

• E.

Stroma, chromatin

B. Thylakoids (stacked to form grana), stroma
Explanation
The primary components of chloroplasts are thylakoids (stacked to form grana) and stroma. Thylakoids are membrane-bound structures that contain chlorophyll and other pigments, where the light-dependent reactions of photosynthesis occur. They are stacked together to form grana, which increase the surface area available for capturing light energy. Stroma, on the other hand, is the fluid-filled space surrounding the thylakoids, where the light-independent reactions of photosynthesis take place. Stroma contains enzymes and other molecules necessary for the synthesis of glucose from carbon dioxide.

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• 33.

### ___________ are used to capture light energy.

Chloroplasts
Explanation
Chloroplasts are the correct answer because they are the organelles found in plant cells that are responsible for capturing light energy through the process of photosynthesis. Within the chloroplasts, pigments such as chlorophyll absorb light energy, which is then converted into chemical energy to fuel the plant's growth and metabolism. This process is essential for plants to produce glucose and oxygen, which are vital for their survival.

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• 34.

### The ________________ is known as the cellular highway system, consisting of a network of fibers extending throughout the cytoplasm.

cytoskeleton
Explanation
The cytoskeleton is known as the cellular highway system because it consists of a network of fibers that extend throughout the cytoplasm. These fibers provide structural support to the cell and help maintain its shape. They also play a crucial role in cell movement and transport of organelles and other cellular components. The cytoskeleton is made up of three main components: microtubules, microfilaments, and intermediate filaments. Microtubules are responsible for cell division and provide tracks for organelle movement. Microfilaments are involved in cell contraction and movement, while intermediate filaments provide mechanical support and help anchor organelles in place.

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• 35.

### What are the three roles of the cytoskeleton?

• A.

Protein synthesis

• B.

Cellular support

• C.

Digestion

• D.

Motility - highway system

• E.

Light energy capture

• F.

Regulation of biochemical activities

B. Cellular support
D. Motility - highway system
F. Regulation of biochemical activities
Explanation
- helps to support the cell and maintain its shape, anchoring many organelles
- interacts with motor proteins to produce motility (highway system)
- vesicles can travel along “monorails” provided by the cytoskeleton
- help regulate biochemical activities

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• 36.

### What are the three components of the cytoskeleton?

• A.

Chromatin, microtubules and actin filaments

• B.

Microtubules, actin filaments and cisternae

• C.

Vacuoles, intermediate filaments and actin filaments

• D.

Microtubules, actin filaments and intermediate filaments

• E.

None of the above.

D. Microtubules, actin filaments and intermediate filaments
Explanation
The correct answer is Microtubules, actin filaments and intermediate filaments. These three components make up the cytoskeleton, which provides structural support to the cell and helps in cell movement and shape determination. Microtubules are hollow tubes made of tubulin protein and are involved in cell division and intracellular transport. Actin filaments are thin, flexible filaments made of actin protein and are involved in cell movement and muscle contraction. Intermediate filaments are rope-like filaments made of various proteins and provide mechanical strength to the cell.

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• 37.

### Actin filaments are hollow tubes, with walls consisting of 13 columns of tubulin molecules of 25 nm diameter with 15 nm lumen.  They are used to shape the cell, separate chromosome during cell division and guide organelle movements.

• A.

False

• B.

True

A. False
Explanation
Microtubules, part of the cytoskeleton

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• 38.

### Actin filaments consist of two solid intertwined strands of actin, each a polymer of actin subunits approximately 7 nm in size and are responsible for cell shape, muscle contraction, cell mobility and cell division.

• A.

True

• B.

False

A. True
Explanation
Actin filaments are indeed composed of two solid intertwined strands of actin, with each strand being a polymer of actin subunits. These filaments play crucial roles in various cellular processes such as maintaining cell shape, facilitating muscle contraction, promoting cell mobility, and aiding in cell division. Therefore, the statement "Actin filaments consist of two solid intertwined strands of actin, each a polymer of actin subunits approximately 7 nm in size and are responsible for cell shape, muscle contraction, cell mobility, and cell division" is true.

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• 39.

### Plant cells have centrosomes but no centrioles.

• A.

True

• B.

False

A. True
Explanation
Plant cells do not have centrioles, which are cylindrical structures composed of microtubules that play a role in cell division. However, they do have centrosomes, which are structures that contain centrioles in animal cells. The centrosome in plant cells serves as a microtubule organizing center, playing a similar role to centrioles in animal cells, but without the presence of actual centrioles. Therefore, the statement that plant cells have centrosomes but no centrioles is true.

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• 40.

### The __________________ is the microtubule-organizing center.

centrosome
Explanation
The centrosome is the microtubule-organizing center in cells. It plays a crucial role in cell division by organizing and anchoring the microtubules that form the mitotic spindle. This structure is responsible for ensuring accurate chromosome segregation during cell division. Additionally, the centrosome is involved in various other cellular processes, including cell motility, cell polarity, and intracellular transport. It consists of a pair of centrioles surrounded by pericentriolar material, which contains proteins necessary for microtubule nucleation and organization. Overall, the centrosome is essential for maintaining cell structure and function.

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• 41.

### Plasmodesmata are channels between adjacent plant cells.

• A.

True

• B.

False

A. True
Explanation
Through plasmodesmata, water and small solutes (and sometimes proteins and RNA) can pass from cell to cell, the cytoplasm of one plant cell is continuous with the cytoplasm of its neighbors

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• 42.

### What are the functions of the ECM (extracellular matrix) of animal cells?

• A.

Waste disposal

• B.

Support

• C.

Cellular shape

• D.

• E.

Movement

• F.

Motility

• G.

Regulation

B. Support
E. Movement
G. Regulation
Explanation
The ECM (extracellular matrix) of animal cells serves multiple functions. It provides support to the cells, helping to maintain their structure and integrity. It also plays a role in cell adhesion, allowing cells to attach to each other and to the ECM itself. The ECM is involved in cell movement, providing a framework for cells to migrate and interact with their surroundings. Additionally, the ECM helps regulate various cellular processes, such as cell signaling and tissue development.

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• 43.

### Animal cells lack cell walls but are covered by an elaborate ECM (extracellular matrix).

• A.

True

• B.

False

A. True
Explanation
Animal cells lack cell walls, which is a characteristic that distinguishes them from plant cells. Instead of a cell wall, animal cells are covered by an elaborate extracellular matrix (ECM). The ECM is a complex network of proteins and carbohydrates that provides structural support and facilitates cell-cell communication. It plays a crucial role in various cellular processes such as adhesion, migration, and tissue development. Therefore, the statement that animal cells lack cell walls but are covered by an elaborate ECM is true.

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• 44.

### What are the functions of tight junctions in animal cells?

• A.

Membranes of neighbouring cells are pressed together, preventing leakage of extracellular fluid

• B.

Fasten cells together into strong sheets

• C.

Provide cytoplasmic channels between adjacent cells

• D.

None of the above

A. Membranes of neighbouring cells are pressed together, preventing leakage of extracellular fluid
Explanation
Tight junctions in animal cells function by pressing the membranes of neighboring cells together, which helps to prevent the leakage of extracellular fluid. This tight seal created by the tight junctions ensures that substances cannot pass through the gaps between cells, maintaining the integrity and barrier function of the tissue. This is important in organs and tissues that require a selective barrier, such as the digestive tract or blood-brain barrier. The other options provided, fastening cells together into strong sheets and providing cytoplasmic channels between adjacent cells, are functions of other types of cell junctions like desmosomes and gap junctions, respectively.

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• 45.

### What are the functions of Desmosomes in animal cells?

• A.

Membranes of neighbouring cells are pressed together, preventing leakage of extracellular fluid

• B.

Fasten cells together into strong sheets

• C.

Provide cytoplasmic channels between adjacent cells

• D.

None of the above

B. Fasten cells together into strong sheets
Explanation
Desmosomes are specialized cell junctions that play a crucial role in holding animal cells together. They function to fasten cells together into strong sheets, providing structural integrity and stability to tissues. Desmosomes accomplish this by forming strong connections between adjacent cells, anchoring the cytoskeletons of the cells to each other. This allows for the transmission of mechanical forces and prevents the cells from being pulled apart. Therefore, the correct answer is "Fasten cells together into strong sheets."

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• 46.

### What are the functions of gap junctions in animal cells?

• A.

Membranes of neighbouring cells are pressed together, preventing leakage of extracellular fluid

• B.

Fasten cells together into strong sheets

• C.

Provide cytoplasmic channels between adjacent cells

• D.

None of the above

C. Provide cytoplasmic channels between adjacent cells
Explanation
Gap junctions are specialized protein channels that connect the cytoplasm of adjacent animal cells. These channels allow for the direct exchange of ions, small molecules, and electrical signals between the cells. This communication is important for coordinating the activities of cells within tissues and organs. Gap junctions do not prevent leakage of extracellular fluid or fasten cells together into strong sheets, making the correct answer "Provide cytoplasmic channels between adjacent cells."

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• 47.

### The general structure of a biological membrane is a single layer of phospholipids.

• A.

True

• B.

False

B. False
Explanation
The general structure of a biological membrane is a double layer of phospholipids.

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• 48.

### How often do phospholipids in the plasma membrane move in a lateral direction?

• A.

~ once per month

• B.

~ once per day

• C.

~ 10E7 times/second

• D.

~ 10E4 times/second

• E.

Never

C. ~ 10E7 times/second
Explanation
Phospholipids in the plasma membrane move in a lateral direction approximately 10E7 times per second. This means that they are constantly in motion and can rapidly change their position within the membrane. This high frequency of movement is due to the fluid nature of the phospholipid bilayer, which allows for the dynamic rearrangement of molecules. The constant motion of phospholipids is important for various cellular processes, such as membrane fluidity, protein interactions, and signal transduction.

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• 49.

### How often do phospholipids in the plasma membrane flip-flop?

• A.

Never

• B.

~ 10E7 times/second

• C.

~ 10E4 times/second

• D.

~ once per day

• E.

~ once per month

E. ~ once per month
Explanation
Phospholipids in the plasma membrane rarely undergo flip-flopping, with an estimated frequency of once per month. This means that the movement of phospholipids from one layer of the membrane to the other is a relatively rare event. The stability of the plasma membrane is maintained by the asymmetrical distribution of phospholipids, with different types of phospholipids present in each layer. This infrequent flip-flopping allows for the preservation of the membrane's structure and function.

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• 50.

### What are the six major functions of membrane proteins?

• A.

Ribosome secretion

• B.

Transport

• C.

Waste recycling

• D.

Enzymatic Activity

• E.

Signal Transduction

• F.

Motility

• G.

Cell-cell recognition

• H.

Intercellular joining

• I.

Attachment to the Cytoskeleton & ECM

• J.

Chromatin production

B. Transport
D. Enzymatic Activity
E. Signal Transduction
G. Cell-cell recognition
H. Intercellular joining
I. Attachment to the Cytoskeleton & ECM

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• Mar 21, 2023
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• Sep 24, 2010
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