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

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.

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.

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

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

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.

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.

An isotonic solution is one whose concentration is equal to that inside the cell. When a cell is placed in an isotonic solution, there is no net movement of water into or out of the cell. This means that the cell neither gains nor loses water.

Receptor-mediated endocytosis is a process in which ligands bind to specific receptors on the cell surface, leading to the formation of vesicles that internalize the ligands into the cell. This process is a crucial mechanism for the uptake of various molecules, such as nutrients and signaling molecules, into the cell. Therefore, the statement that the binding of ligands to receptors triggers vesicle formation is true.

Phagocytosis is the process of "cellular eating" where a cell engulfs solid particles or large molecules into its cytoplasm. Pinocytosis, on the other hand, is the process of "cellular drinking" where a cell takes in fluid and dissolved substances by forming small vesicles. Therefore, the correct answer is Phagocytosis, Pinocytosis.

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.

Water is a polar solvent because it has a partial positive charge on the hydrogen atoms and a partial negative charge on the oxygen atom. This polarity allows water molecules to form hydrogen bonds with other polar molecules or ions, making it an excellent solvent for substances that are also polar.

Osmosis is the process of water molecules moving from an area of lower solute concentration to an area of higher solute concentration through a selectively permeable membrane. This occurs in order to equalize the solute concentration on both sides of the membrane. Diffusion, on the other hand, refers to the movement of molecules from an area of higher concentration to an area of lower concentration, without the involvement of a membrane. Motility and transport are not relevant to the process described in the question.

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.

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.

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

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.

Diffusion is the correct answer because it refers to the natural process where molecules move from an area of high concentration to an area of low concentration. This movement occurs without the need for any additional energy or work, as it is driven by the random motion of the molecules. Diffusion allows for molecules to spread out evenly into the available space, resulting in a uniform distribution of the substance. Osmosis, on the other hand, specifically refers to the diffusion of water molecules across a selectively permeable membrane. Motility and transport are not accurate descriptions of this process.

Facilitated diffusion is the process in which transport proteins assist in the movement of molecules across the plasma membrane. These transport proteins create channels or carriers that allow specific molecules to pass through the membrane more quickly than they would through simple diffusion. This process does not require energy expenditure and is used for the transport of larger or charged molecules that cannot easily pass through the lipid bilayer of the membrane. Osmosis refers specifically to the movement of water molecules across a membrane, while facilitated osmosis is not a recognized term. Therefore, the correct answer is facilitated diffusion.

A hydrophilic substance has an affinity for water and cannot move through lipids because lipids are hydrophobic and repel water. On the other hand, a hydrophobic substance does not have an affinity for water and can move through lipids because it is compatible with the nonpolar nature of lipids.

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.

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.

Diffusion is a passive transport process where substances move from an area of higher concentration to an area of lower concentration. It does not require any energy input from the cell to occur. Therefore, the correct answer is "zero".

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.

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.

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.

A hypertonic solution is one in which the solute concentration is greater than that inside the cell, causing the cell to lose water. In a hypertonic solution, there is a higher concentration of solute particles outside the cell compared to inside the cell. As a result, water molecules move out of the cell through osmosis, causing the cell to shrink or lose water.

Water is a polar molecule, meaning it has a slightly positive end and a slightly negative end. This polarity allows water to attract and dissolve other polar molecules, such as compounds made of nonionic polar molecules and large polar molecules like proteins. Additionally, water can dissolve compounds with ionic and polar regions because it can form hydrogen bonds with these molecules. Therefore, the statement "Water can dissolve compounds made of nonionic polar molecules and large polar molecules such as proteins (if they have ionic and polar regions)" is true.

Active transport uses energy (usually in the form of ATP) to move solutes against their concentration gradient, thus allowing cells to maintain concentration gradients that differ from their surroundings. This process requires the use of specific transport proteins in the cell membrane to pump solutes across the membrane against the concentration gradient. This is in contrast to passive transport, which does not require energy and moves solutes down their concentration gradient. Therefore, the correct answer is active transport, against the concentration gradient.

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.

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.

A plant cell swells until the wall opposes uptake and is now turgid. This suggests that water has entered the cell through osmosis, causing it to expand. In a hypotonic solution, there is a lower concentration of solutes outside the cell compared to inside the cell. This creates a concentration gradient that drives water to move into the cell, leading to cell swelling and turgidity. Therefore, the plant cell in this scenario is most likely in a hypotonic solution.

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."

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.

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.

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.

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.

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.

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.

In plasmolysis, the membrane pulls away from the cell wall when in a hypertonic environment. This is because a hypertonic environment has a higher concentration of solutes outside the cell compared to inside the cell. As a result, water molecules move out of the cell, causing the cell to shrink and the membrane to detach from the cell wall.

At warm temperatures, such as 37ºC, cholesterol restrains movement of phospholipids. This is because at higher temperatures, the phospholipids would have more kinetic energy and move around more freely. Cholesterol acts as a "spacer" between the phospholipids, preventing them from packing tightly together.
At cool temperatures, cholesterol maintains fluidity by preventing tight packing. This is because at lower temperatures, the phospholipids would have less kinetic energy and move around less. Cholesterol fills in the gaps between the phospholipids, preventing them from becoming too closely packed and rigid.

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.

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.

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.

A hypotonic solution is one in which the solute concentration is less than that inside the cell, causing the cell to gain water. In a hypotonic solution, there is a higher concentration of water molecules outside the cell compared to inside. As a result, water moves into the cell through osmosis, causing the cell to swell or gain water. This can lead to the cell expanding and potentially bursting if the influx of water is too high.

If an animal cell and its surroundings are isotonic, it means that the concentration of solutes inside the cell is equal to the concentration of solutes outside the cell. In this situation, there will be no net movement of water into or out of the cell, resulting in no change in the cell's shape or turgidity. Therefore, the statement that the cell becomes flaccid and may wilt is incorrect.

- 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

Microtubules, part of the cytoskeleton

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.

Channel proteins have a hydrophilic channel that certain molecules or ions can use as a tunnel, allowing them to pass through the membrane. Carrier proteins, on the other hand, bind to molecules and change shape to shuttle them across the membrane. Therefore, the correct answer is "Channel, carrier".

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.