Chapter 7: Cells and Organelles

What is the function of a bacterium's capsule? adhesion protection protein synthesis propulsion DNA storage

Protection

For prokaryotic cells, which statement is correct concerning how the structure of a particular cell component correlates with its function? Photosynthetic membranes contain magnetite that allows the cell to convert magnetic field energy into chemical energy. The cell wall is a tough, fibrous layer that protects the cell and gives it shape and rigidity. The cell wall represents infoldings of the plasma membrane that protect the cell and give it shape and rigidity. Photosynthetic membranes are composed of crosslinked polymers like peptidoglycan that provide extensive surface area for photosynthesis.

The cell wall is a tough, fibrous layer that protects the cell and gives it shape and rigidity.

1.In eukaryotic flagella, the fibers that slide past one another due to the activity of dynein proteins are microtubules. 2. Many cell organelles, most notably the nucleus, are anchored by intermediate filaments which are assembled from a diverse class of proteins. 3. Centrosomes are sites where protein dimers assemble into microtubules. 4. The extension of pseudopodia in amoeba is due to the regulated assembly and destruction of microfilaments. 5. The only cytoskeletal fibers not associated with intracellular movement or whole cell locomotion are the intermediate filaments. 6. During muscle contractions, myosin motor proteins move across tracks of microfilaments.

The eukaryotic cytoskeleton is appropriately named because, at the cellular level, these fibers and their associated motor proteins perform similar roles as an animal's musculoskeletal system. Microfilaments are responsible for cell locomotion and the cell's structural characteristics. Microtubules serve as intracellular highways for transporting vesicles and organelles; they are also required for cellular locomotion via flagella and cilia. Intermediate filaments are rope-like structures that anchor organelles and intercellular junctions called desmosomes. They are specialized for bearing tension.

Which of these provides the cell with structural support?

Microfilaments are a component of the cytoskeleton.

Which of these are hollow rods that shape and support the cell? chloroplasts peroxisomes microfilaments microtubules plasma membrane

Microtubules are rods that also play a role in organelle movement.

Which of these organelles carries out cellular respiration? nucleolus mitochondrion ribosomes smooth endoplasmic reticulum chromatin

Mitochondria convert the chemical energy of organic molecules to chemical energy in the form of ATP.

Which organelle described in the table in part A would pellet first during centrifugation? mitochondria ribosomes lysosomes nuclei

Nuclei are the largest organelles with an intermediate density and would pellet first.

What is Phagocytosis?

Phagocytosis involves the engulfing of large particles.

Can a chloroplast replicate itself? Yes No

Yes

Can a vacuole in a cell be considered to be an organelle? Yes No Sometimes, if it has DNA Sometimes, if it has enzymes, water and protein

Yes

_____ is/are identical in structure to centrioles. Microfilaments Mitochondria Chromatin Basal bodies Nuclear envelopes

basal bodies

How much of the human genome is thought to be due to insertion by viral DNA? 0% between 0 and 0.01% 0.1-1% 5-8% 95-95%

5-8%

What central theme of biology helps explain why various cells can look so different from one another? Cells correlate structure with function. Different cells contain different macromolecules as their genetic material. All cells need to engage in energy transformations. Cells must be small in size.

A cell's structure will depend upon its function. Cells with different functions will have different structures.

Where is a bacterial cell's DNA found? ribosomes nucleus peroxisome nucleoid region capsule

Bacteria lack a nucleus; their DNA is found in the nucleoid region.

True or false? Proteins produced during the "chase" phase of a pulse-chase experiment are labeled with radioactive materia

During the chase phase, cells are provided with a large amount of nonradioactive material, so they are not labeled.

What is the correct sequence for secreted protein movement through the endomembrane system? vesicles, ER, trans-Golgi, cis-Golgi cis-Golgi, trans-Golgi, ER, vesicles ER, trans-Golgi, cis-Golgi, vesicles ER, cis-Golgi, trans-Golgi, vesicles

ER, cis-Golgi, trans-Golgi, vesicles

Viruses can replicate their genetic material in the absence of cells true false

False

What scientific hypotheses can be tested by a pulse-chase experiment? Solubility of a molecule The steady-state amount of protein in a cell Movement of molecules through a cell over time The amino acid sequence of a protein

Pulse-chase experiments allow for the tracking of molecules in a cell over time.

In a bacterium, where are proteins synthesized? ribosomes nucleus peroxisome nucleoid region capsule

Ribosomes are involved in the manufacture of polypeptides (proteins).

What path does a protein in the secretory pathway take, starting from its site of synthesis? Golgi apparatus, rough ER, secretory vesicles, plasma membrane Rough ER, secretory vesicles, Golgi apparatus, plasma membrane Plasma membrane, secretory vesicles, Golgi apparatus, rough ER Rough ER, Golgi apparatus, secretory vesicles, plasma membrane

Rough ER, Golgi apparatus, secretory vesicles, plasma membrane Proteins are synthesized in the rough ER, modified in the Golgi apparatus, and carried in secretory vesicles to the plasma membrane, where they are secreted.

Which of these structures stores, modifies, and packages products?

The Golgi apparatus modifies, stores, and packages products of the ER.

What name is given to the rigid structure, found outside the plasma membrane, that surrounds and supports the bacterial cell? capsule pili cell wall flagella nucleoid region

The cell wall is a rigid supporting structure.

Which of these is a double membrane that enclose the nucleus?

This is the nuclear envelope.

ellular homogenization is often incomplete, and the mixture has unbroken cells. These cells are found in _____. the second supernatant pellet 1 the first supernatant pellet 2

The first pellet has the largest components, such as nuclei and whole cells.

The bacterial cell wall functions to _______. maintain the position of the nucleus protect the cell and provide shape and rigidity synthesize pigments needed for photosynthesis propel bacterial cells through their environment

The main role of the cell wall, which lies external to the plasma membrane, is to prevent the cell from swelling due to osmotic stress and also to provide shape and support.

What is the main function of a chloroplast? to break down sugars to convert light in to chemical energy to produce enzymes that will be used to make proteins to interact with the nucleus to promote cell division

convert light to chemical energy

Which statement most accurately describes what happens to proteins that lack an ER signal sequence? They are inserted into the plasma membrane. They are inserted into the ER membrane but do not enter the ER lumen. They are released into the cytosol. They bypass the ER but enter the Golgi apparatus.

cytosol

In experiments to test whether a protein can enter the nucleus, why would proteins be labeled with fluorescent molecules? To give the protein molecules energy To make the proteins bigger To make the proteins easy to see To target the proteins to the nucleus

easier to see

The genetic material in viruses is composed of DNA RNA Either DNA or RNA neither DNA nor RNA

either DNA or RNA

If they had instead performed this assay on muscle cells, which have high energy demands and primarily consist of actin and myosin filaments, where would you expect the labeled proteins to go during the chase? from the cytoplasm to the Golgi apparatus from the Golgi apparatus and the rough ER to the cytoplasm and the mitochondria from the Golgi apparatus and the rough ER to the cytoplasm and the nucleus from the rough ER to the Golgi apparatus

from the Golgi apparatus and the rough ER to the cytoplasm and the mitochondria

Endocytosis moves materials _____ a cell via _____. out of ... membranous vesicles into ... membranous vesicles into ... facilitated diffusion into ... a transport protein out of ... diffusion

into...membraine vesicles

What feature is most commonly associated with what most biologists would consider to be organelles? DNA proteins lipid membrane enzymes water

lipid membrane

Which organelle plays a role in intracellular digestion? lysosome ribosome plasmodesma chloroplast Golgi apparatus

lysos means injestion to decompose

What two organelles cannot be separated easily by centrifugation? (See the table.) nuceli 1.4 -5-10 mitochondria 1.1 -1-2 ribosomes 1.6 -0.02 lysosomes 1.1 -1-2 ribosomes and mitochondria ribosomes and nuclei nuclei and mitochondria lysosomes and mitochondria

lysosomes and mitochondria These organelles are very similar in size and density; therefore, they cannot easily be separated by centrifugation.

What is pinocytosis?

pinocytosis ... the cell is engulfing extracellular fluid

What is receptor-mediated endocytosis?

receptor protein involved

_____ are the sites of protein synthesis. Golgi apparatuses Ribosomes Mitochondria Microfilaments Peroxisomes

ribosomes

What is exocytosis?

A membranous vesicle is fusing with the plasma membrane and releasing its contents into the extracellular fluid.

Which of these manufactures cellular membranes by adding membrane proteins and phospholipids to its own membrane? Golgi apparatus rough endoplasmic reticulum nucleolus lysosomes ribosomes

As membrane proteins grow from ribosomes on rough ER, the proteins are embedded into the rough ER membrane.

Pancreatic cells, which secrete a large amount of digestive enzymes, are labeled with radioactive leucine and then chased for several hours with nonradioactive leucine. Photographic emulsions are prepared at different times during the chase. Where would the black spots appear on an emulsion prepared 3 hours after the pulse? a.Secretory vesicles b.Rough ER c.Golgi apparatus d.Exterior of the cell

Black spots would appear on the exterior of the cell after 3 hours, indicating that the proteins had been secreted from the cell.

The preparation of liver mitochondrial enzymes begins by placing liver and a buffered solution in a blender. What is the purpose of the blender? to remove the plasma membranes from the intracellular structures, such as the mitochondria to separate the mitochondria from the other organelles to prepare a cell homogenate; to break open the liver cells and to release the organelles to separate the nuclei from the mitochondria

Blenders are used to prepare cell homogenates.

What is the first step in a pulse-chase experiment? Incubating cells with an unlabeled molecule Examining cells for the location of the labeled molecules Preparing cells for electron microscopy Incubating cells with a labeled molecule

Cells are first "pulsed" with a large amount of labeled material for a short time.

For eukaryotic cells, which answer best describes the function of the indicated component? Peroxisome: detox center Endomembrane system: administrative/information hub Golgi apparatus: waste-processing and recycling center Lysosome: protein finishing and shipping line

Correct. Peroxisomes are centers for redox reactions, including those that render certain toxins harmless.

A prokaryotic cell is distinct from a eukaryotic cell because a prokaryotic cell lacks _____. carbohydrates a plasma membrane ribosomes a nucleus

Correct. Prokaryotic cells lack a membrane-bound nucleus. Eukaryotic literally means "true kernel" and prokaryotic cells lack the "kernel" or nucleus.

What do mitochondria and chloroplasts have that golgi apparatus and endoplasmic reticulum lack? lipid membrane proteins enzymes water DNA

DNA

Which molecules do not normally cross the nuclear membrane? Nucleotide triphosphates mRNA DNA Proteins

DNA

True or false? Large proteins containing a nuclear localization signal (NLS) bind to the nuclear pore and enter the nucleus without any expenditure of energy. True False

False Cytoplasmic proteins called importins bind to large proteins containing an NLS and mediate their transport across the nuclear membrane through an active transport (energy-requiring) process.

_____ are surface appendages that allow a bacterium to stick to a surface. Fimbriae Ribosomes Mitochondria Flagella Cell walls

Fimbriae

Where is calcium stored? rough endoplasmic reticulum smooth endoplasmic reticulum microtubules centrioles mitochondria

In addition to storing calcium, the smooth ER also plays a role in detoxification and lipid synthesis.

A small protein (molecular weight = 25,000 daltons) is injected into a cell and observed in the nucleus a short time later. What type of transport has taken place? Passive transport Osmosis Active transport

Passive Transport A 25,000-dalton protein is small enough to diffuse through nuclear pores without any expenditure of energy.

Which of these organelles produces H2O2 as a by-product? nucleus centrioles flagellum peroxisome mitochondrion

Peroxisomes produce hydrogen peroxide as a by-product of their metabolic processes.

A white blood cell engulfing a bacterium is an example of _____. exocytosis phagocytosis pinocytosis receptor-mediated endocytosis facilitated diffusion

Phagocytosis occurs when a cell engulfs a large particle.

Nucleoplasmin is a nuclear protein. This protein was divided into two segments and linked to the same large cytoplasmic protein, generating two fusion proteins. After injecting these fusion proteins into a cell, one of the proteins was found in the nucleus and the other in the cytoplasm. Which of the following conclusions can be drawn from these results? The cytoplasmic protein contains a nuclear localization signal. One of the fusion proteins entered the nucleus by passive transport. Only one of the two fusion proteins possesses a nuclear localization signal. Nucleoplasmin does not have a nuclear localization signal.

The nuclear localization signal is only present in the fusion protein that enters the nucleus

Where can the most DNA be found?

The nucleus contains most of a cell's DNA.

During a pulse-chase experiment, photographic emulsions were prepared at different times during the chase, and radioactive spots were detected at the following times and locations: 5 minutes: rough ER; 10 minutes: Golgi apparatus; 40 minutes: endosomes; 70 minutes: lysosomes; 140 minutes: lysosomes. Which of the following conclusions can be drawn from these results? The proteins did not travel through the Golgi apparatus. The proteins were secreted. The proteins traveled from lysosomes to endosomes. The final destination of the proteins was the lysosome.

This conclusion can be drawn from the results, since the radioactive spots were last detected at the lysosome, which is not a secretory vesicle.

The HIV virus can change the genetic make-up of a cell it infects and actually become part of its total genetic make-up true false

True

Viruses have the potential to bring bits of DNA from one species to another species and incorporate the DNA from one species into the permanent genome of another species. true false

True

In plant cells, why are toxins like nicotine, cocaine, and caffeine stored in vacuoles instead of the cytosol? Toxins are degraded in the vacuoles, preventing them from harming the cell. Toxins in vacuoles are sequestered from the rest of the cell, where they could do harm. The high concentration of toxins in vacuoles allows them to function more efficiently within the cell. Toxins are synthesized in the vacuoles.

Vacuoles serve as storage depots that keep noxious compounds like toxins separate from the rest of the cell. If released into the cytosol, toxins would poison the cell.

The _____ is composed of DNA and protein. flagellum mitochondrion ribosome chromatin centriole

chromatin

Which of the following statements about the nuclear envelope is false? Nuclear pores are made up of a group of proteins that are collectively called the nuclear pore complex. The nuclear envelope is continuous with the Golgi apparatus. Molecules pass into and out of the nucleus through nuclear pores. The nuclear envelope is composed of two lipid bilayers.

continuois with gogi body

Ribosomal subunits are manufactured by the _____. smooth endoplasmic reticulum peroxisome nucleolus lysosome rough endoplasmic reticulum

nucleiolus

A researcher was interested in the histones, which are DNA-associated proteins. Which pellet should he keep? (See the figure.) all of the pellets pellet 2 pellet 1 pellet 3

pellet 1 The first pellet has the nuclei, which contain the DNA.

The _____ is the bacterial structure that acts as a selective barrier, allowing nutrients to enter the cell and wastes to leave the cell. plasma membrane nucleoid region ribosome pili cell wall

plasma membrane

How are proteins transported to their correct location in the cell? The cell always synthesizes a protein in the compartment in which it will be used. Every protein will have a nucleic acid attached to it that tells the cell in which compartment it will be used. The cell sends the proteins to the cellular compartment that currently has the least amount of proteins in it. Proteins contain molecular "zip codes" that allow them to be shipped to the correct cellular compartment.

proteins destined for the nucleus contain a nuclear localization signal, and other proteins contain an ER signal sequence.

The HIV virus uses the protein reverse transcriptase to make DNA from its RNA contains double stranded DNA in its capsid contains ribosomes in its capsid contains no proteins within its capsid

uses the protein reverse transcriptase to make DNA from its RNA