Biology-Test 3

What is generally the maximum magnifying capacity of a light microscope?

2000

Upon observing a cell of a grass blade, you notice a prominent sac that occupies a large portion of the cell. Which organelle is this?

Vacuole

Suppose that acetylcholine binds its receptor on the surface of a muscle cell. What happens next?

A sodium gate opens.

The hydrolysis of GTP to GDP deactivates the ____.

G protein

The main signaling cascade for cell division and differentiation is the ____ cascade.

MAP kinase

What type of chemical compound diffuses across synapses?

Neurotransmitters

What is a characteristic found in both prokaryotic and eukaryotic cells?

Plasma membrane

Which is a part of a signal transduction pathway that enables vision in dim light in vertebrates?

Rhodopsin

What is the process in which one activated receptor can give rise to thousands of final products?

Signal amplification

What type of cells must receive, relay, and respond to the information signaled?

Target cells

Under which of the following situations would receptor downregulation most likely occur?

The concentration of a hormone is too high

A person has a genetic disease that prevents the phospholipids in the plasma membrane of the white blood cells from freely fusing with the other membranes within the cell. How would this disease affect phagocytosis?

The phagocytic vacuole would not fuse with the lysosome.

How is paracrine signaling different from other types of signaling?

The signaling molecules are diffused through interstitial fluid and act on nearby cells.

Refer to the accompanying figure. Which best describes what is happening to the red blood cells in Fig. A?

There has been no net water movement.

Which statement about receptors is false?

They are also called ligands

How are integral proteins unique in cell membranes?

They are firmly bound to the membrane.

What is the purpose of the cristae of the inner membrane of mitochondria?

To increase surface area

Most intracellular receptors are what type of protein?

Transcription factors

Ion channels are found in the plasma membranes of neurons and muscle cells.

True

DNA transcribes its information into what type of molecule?

mRNA

The ratio of the size of the image seen with the microscope to the actual size of the object is called:

magnification

A single cell in a smoker's lung has become cancerous. It doubles its DNA and divides much faster than a normal lung cell. The most likely change that would have caused this condition took place in the:

nucleus

The role of ATP in the sodium-potassium pump is

to transfer Na+ to the outside of a cell.

Match the following descriptions to the appropriate protein molecule. - integrins - channels - protein pumps - signal transduction receptors - membrane-bound enzymes

- Anchor cell to extracellular matrix - Allow selective transport of ions or molecules - Use ATP to transport solutes - Transmit information into cell - Catalyze reactions which take place within or along the membrane surface

Match the receptor with the correct description of its activated state. Answers may be used more than once. - Phosphate comes from ATP - Protein kinase sites are active. - Sodium ions enter the cell. - GDP is replaced with GTP - DAG is the second messenger.

- Enzyme-linked receptor - Enzyme-linked receptor - Ion channel-linked receptor - G protein- linked receptor - G protein- linked receptor

What is the microtubule arrangement of a flagellum or cilium?

9 + 2 arrangement

What is calmodulin?

A calcium-binding protein

What is typically the result of receptor upregulation?

A hormone's signal is amplified.

Why is it advantageous for cells to be small?

A small cell has a small volume relative to surface area, which allows efficient transport through the plasma membrane.

What is required for facilitated diffusion to take place?

A transmembrane protein

What does an ABC transporter use to move larger ions and molecules across the cell membrane?

ATP

Adenylyl cyclase catalyzes the reaction in which

ATP is converted to cAMP.

The cis face of the Golgi complex is most directly involved in which process?

Accepting vesicles from the ER

Which molecule is a first messenger but not a second messenger?

Acetylcholine

Which neurotransmitter opens ligand-gated sodium channels?

Acetylcholine

Since sodium-potassium pumps transport sodium ions out of a cell and potassium ions into a cell, what type of carrier proteins are they?

Antiporters

In the IP3 pathway, what is the function of IP3?

Binds calcium channels in the ER

What happens during the cotransport of glucose and sodium ions?

Both D and E

How are hormones produced by endocrine glands typically transported to target cells?

By the blood

When food is scarce, the amoeba-like cellular slime mold, Dictyostelium, secretes which compound?

Cyclic adenosine monophosphate

Which cellular mechanism ejects products, such as hormones, by the fusion of a vesicle with the plasma membrane?

Exocytosis

Biological membranes are one-dimensional fluids.

False

G protein-linked receptors are transmembrane proteins with a binding site for a signaling molecule outside the cell and a neuron component inside the cell.

False

Groups of eight connexin molecules cluster to form a cylinder that spans the plasma membrane.

False

In cell membranes, cholesterol and glycoproteins are exposed to the extracellular surface for cell recognition and adhesion to other cells.

False

Insulin stimulates cells to take in glucose by facilitated diffusion, so the down regulation of insulin receptors increases the ability of cells to take in glucose.

False

Kinesin transports organelles toward the minus end of a microtubule.

False

Mitochondria play an important role in cell necrosis

False

The outer part of the enzyme-linked receptor has a binding site for a signaling molecule, and the part of the receptor that extends into the cytosol has a binding site for a specific G protein.

False

The smooth ER is the primary site for the synthesis of proteins and cholesterol needed to make membranes.

False

When a signaling molecule binds to a G protein-linked receptor, the ligand-receptor complex associates with GDP protein and causes GDP to be replaced by GTP.

False

When an enzyme-linked receptor is activated, a conformational change activates the extracellular kinases.

False

When food is abundant, the cellular slime mold Dictyostelium secretes cAMP into the environment to signal the formation of a multicellular slug-shaped colony.

False

Which statement about the accompanying figures is true?

Figure B has a smaller surface area to volume ratio than Figure A.

In the accompanying figure, what is the form of cellular junction?

Gap junctions

Proteins that are synthesized by ribosomes may be further modified within which organelle?

Golgi complex

What type of protein can transduce a signal in two directions?

Integrins

Why can cholesterol act as a "fludity buffer' in cell membranes?

It is slightly amphipathic because of the presence of one hydroxyl group.

A receptor on the cell surface usually has several domains. What is the function of the external domain?

It is the docking site for a signaling molecule

What can happen when GABA binds to its receptor?

Neural signaling is inhibited.

What transmits information electrically and chemically?

Neurons

Which statement about G protein is false?

One subunit binds ATP.

A local regulator is a signaling molecule that diffuses through the interstitial fluid, the fluid surrounding the cells, and acts on nearby cells. What is this process?

Paracrine regulation

What method does a human white blood cell employ to engulf a bacterial cell?

Phagocytosis

Mammalian red blood cells contain which type of membrane?

Plasma membrane

What is found between adjacent plant cells that allows signal molecules to pass quickly from one cell to another?

Plasmodesmata

Which list describes the correct sequence of events involved in cell signaling?

Signal transmission, reception, signal transduction, response

You light a scented candle in the guest bathroom. Within a few minutes, you can smell the candle's scent throughout the hallway. What process is occurring?

Simple diffusion

What type of molecule can rapidly cross a plasma membrane?

Small, hydrophobic molecules

How do the phospholipids in vegetable oil differ from those of animal fat?

The fatty acid tails bend

In the cAMP signal transduction pathway, a protein kinase is activated. What happens next?

The protein kinase activates a cellular response.

What happens when Ras proteins become stuck in their "on" state?

There is unregulated cell division.

Refer to the accompanying figure. Which best describes the red blood cells in Fig. B?

These red blood cells have shrunk is response to a hypertonic external solution.

In the accompanying figure, what is the role of the structures between the membranes?

They allow the transport of small molecules and ions between adjacent cells.

Which statement about Ras proteins is false?

They are inactivated when phosphorylated.

Which statement about lipid bilayers is false?

They are inflexible

Which of the following statements about phospholipids is false?

They contain three fatty acids chains.

Which statement about centrioles is false?

They have a 9 + 2 arrangement of microtubules.

In animal cells, the main microtubule organizing center (or centrosome) is important in cell division.

True

In scanning electron microscopy, an electron beam passes through a very thin slice of a specimen and then falls onto a photographic plate or a fluorescent screen.

True

LDL cholesterol is taken into the cell by receptor-mediated endocytosis.

True

Microfilaments are linked with one another and with other proteins by linker proteins.

True

Most plasmodesmata contain a narrow cylindrical structure, called the desmotubule, which runs through the channel and connects the smooth ER of the two adjacent cells.

True

Mutations to ABC transporter genes contribute to cystic fibrosis.

True

Scaffold proteins organize groups of intracellular signaling kinases into signaling complexes.

True

What process halts the net movement of water from a hypotonic solution into a plant's cells and often provides the structural support to many plants?

Turgor pressure

Which is a major group of enzyme-linked receptors?

Tyrosine kinases

Which cellular structure is correctly match to the role it plays within the cell?

centrosome- cell division

The following are different types of neurotransmitters EXCEPT

cyclic adenosine.

During an infection, white blood cells travel to the infected site and phagocytize the pathogens. After phagocytosis, primary lysosomes fuse with the phagocytic vesicle to form a larger vesicle called a secondary lysosome. The purpose for this process is to:

degrade the pathogens with hydrolytic enzymes for later export from the cell

During enzyme-linked reception, signal molecules bind to two tyrosine kinase receptors. The receptor proteins move closer together in the plasma membrane and pair, forming a(n) ____.

dimer

In a lipid bilayer, _______ fatty acid tails face each other within the bilayer and form a region that excludes water.

hydrophobic

A molecule that binds specifically to a receptor is called a ______.

ligand

Plants lack organ systems for disposing of toxic metabolic waste products. Their cells' vacuoles are similar to which animal cell organelle?

lysosomes

What is found between the primary walls of adjacent cells which cause them to tightly adhere to one another?

middle lamella

Which two organelles are responsible for converting energy into forms that can be used by cells?

mitochondria and chloroplasts

What enzyme in the ER lumen catalyzes the efficient folding of proteins into proper conformations? (Figure 4.2)

molecular chaperones

The process by which the plasma separates from the cell wall is called ________.

plasmolysis

Choanoflagellates are important in the study of cell communication evolution because choanoflagellates have

protein kinases similar to those in animals.

The process of receiving an incoming signal is known as _______.

reception

The outer part of a G protein-linked receptor binds to a(n) ____, and its inner part binds to a(n) ____.

signaling molecule; G protein

Evidence that all living cells have a common origin is best illustrated by:

the basic similarities in cell structure and chemistry

Carrier proteins are also called _______.

transporters

How do gap junction differ from desmosomes?

A gap junction provides communication between cells.

DNA is associated with certain proteins, forming a complex called:

chromatin

Once ligand molecules bind to receptors in coated pits of a plasma membrane, the next step of receptor-mediated endocytosis would be

coated vesicle forms by endocytosis.

Which strategy is the most effective for larger cells to have an effective surface area to volume ratio?

having thin, finger-like projections

Sodium-potassium pumps help to maintain a separation of charges across the plasma membrane, which is called the _________________.

membrane potential

Which of the following is a key component of the cytoskeleton?

microtubules

A cell is surrounded by which distinctive surface membrane?

plasma membrane

What is the primary function of mitochondria?

transformation of energy

Match the organelle to the description of its structural components. -Granular body within an organelle which consists of RNA and protein - Large membranous sacs of plants and fungi - Encloses an internal thylakoid membrane - Membranous sacs in animals - Ribosomes stud its outer surface

-Nucleolus -Vacuoles -Plastids -Lysosome -Rough endoplasmic reticulum -microfilaments

During signal transduction of a G protein, the first messenger binds to the receptor, and the G protein is activated. What happens next? Correct Answer

Activation of adenylyl cyclase

Which technique is used to separate different part of cells so that they can be studied by both physical and chemical methods?

Cell fractionation

Which is an example of a second messenger?

Cyclic AMP

Which local regulator is stored in cells of the immune system and released during an allergic reaction?

Histamine

A glycoprotein destined for secretion from the cell would move through the Golgi complex in which sequence?

cis face to medial region to trans face

Fluid that has a higher osmotic pressure than a cell is called ___________.

hypertonic

Which of the following organelles plays an important role in apoptosis, or programmed cell death?

mitochondria

While testing an experimental drip on a vertebrate cell, you notice that the cell cortex becomes more fluid and the cell loses its ability to move. Despite this, you determine that cell strength is maintained. Based on these observations, you correctly conclude that the drug most directly affects:

actin filaments

The force necessary to cause microtubules of cilia and flagella to slide alongside one another is provided through the action of ____ proteins, which derive the energy to perform their work directly from ____ molecules.

dynein; ATP

The sodium-potassium pump is a carrier protein that maintains a(n) ______ gradient across the plasma membrane.

electrochemical

What type of cellular junction cements cells together that use cadherins as a belt around each cell?

Adhering junctions

Plasmolysis occurs in plant cells when the soil or water contains low concentrations of salts or fertilizers.

False

A patient who has had a severe hemorrhage accidentally receives a large transfusion of distilled water directly into a major blood vessel. What effect will this have on the patient?

It will have serious, perhaps fatal consequences because the red blood cells could swell and burst.

In cells that are constantly involved in secretion, an equivalent amount of membrane must be returned to the interior of the cell for each vesicle that fuses with the plasma membrane; if this does not occur, then what would happen?

The cell surface will keep expanding

In many cells, including almost all animal cells, the centrosome contains two structures called _________.

centrioles

Plasmodesmata of plant cells are functionally equivalent to the ____ of animal cells.

gap junctions

A transmembrane protein differs from other membrane proteins because

it completely extends through the membrane.

Intermediate filaments are most closely associated with which of the following ?

keratins

Typically, the gate of an ion channel remains closed until a(n) ____ binds to the receptor.

ligand

The cellular structure indicated by the arrow in the accompanying figure is responsible for:

protein synthesis

What does the nucleolus, within the nucleus, synthesize?

ribosomal RNA

Peroxisomes are found in large numbers in cells that synthesize, store, and degrade lipids, and one of their functions is to break down protein molecules.

False

A basal body anchors what part of a cell?

flagellum

The gas ethylene is a plant hormone that regulates a variety of processes, including seed germination and ripening of fruit.

True

Which of the following is necessary for a cell to maintain its function and growth?

food

Cotransport systems directly provide energy for active transport of solutes.

False

Enzymes called proteases in the ER luman catalyze folding of proteins into proper conformations.

False

Consider the cellular process illustrated in the accompanying figure. What substance would most likely be transported in this manner? (Figure 5-2) (3 picutres, circle)

Hormones

Which proteins are located on the inner or outer surface of the plasma membrane, usually bound to exposed regions of integral proteins by noncovalent interactions?

Peripheral membrane proteins

Which molecule is least likely to cross a cellular membrane by simple diffusion?

Potassium ion

If a bacterial toxin destroys ribosomes, what cellular activity will be affected first?

Protein synthesis

How does the scanning electron microscope differ from the transmission electron microscope?

The SEM yields a 3D image of the object being studied.

You conduct an experiment in which you inactivate Ras proteins in fibroblast cells. Which of the following is the most immediate consequence of this procedure?

The fibroblasts no longer synthesize DNA in response to growth factors.

Although glucose molecules constantly diffuse into a red blood cell along their concentration gradient, equilibrium is never reached and a steep concentration gradient is continually maintained. What causes this?

The rapid addition of a phosphate to the glucose molecules

Which of the following is not a property of membranes?

They inhibit the passage of materials.

Almost every vertebrate cell has a primary cilium, a single cilium on the cell surface that serves as a cellular antenna.

True

Barbiturates and benzodiazepine drugs bind to GABA receptors to open chloride channels, inhibit neural impulse, and induce tranquility.

True

Cells that secrete large amounts of glycoprotein have many Golgi stacks

True

The many short appendages that a cell has are called cilia.

True

The micrometer (μm) is the most convenient unit for measuring cells.

True

The peripheral membrane proteins can be easily removed without disrupting the bilayer structure of the membrane.

True

What are the colors of an electron micrograph?

black and white

Peripheral proteins are linked to either surface of the plasma membrane by

bonding to integral proteins through noncovalent interactions.

Phosphodiesterase catalyzes the conversion of

cAMP to AMP.

The smooth ER is the primary site for the synthesis of phospholipids and cholesterol needed to make ____.

cell membranes

What protects a cell and may help keep other cells at a distance?

glycocalyx

When the net movement of water in and out a cell is zero, that solution is said to be

isotonic

You isolate a cellular structure and determine that it is composed of a-tubulin and B-tubulin. Based on this evidence, you correctly identify this structure as a(n):

microtubule

The accompanying image is the product of which type of microscope?

scanning electron microscope

What activates protein kinase C?

DAG

Name the part of the cell outside the nucleus.

Cytoplasm

What facilitates the rapid transport of water through the plasma membrane?

Aquaporins

Where are hormones produced in animals?

Endocrine glands

Where are calcium ions stored before a signaling pathway releases them into the cytosol?

Endoplasmic reticulum

What cellular process is represented in the accompanying figure?

Exocytosis

In the phospholipase C signal transduction pathway, which pair of second messengers is produced?

IP3 and DAG

Scaffold proteins ensure that signals are relayed ____.

efficiently

Which of the following pairs is correctly matched?

integrins−receptors