Bio Hw 6

What name is given to the rigid structure, found outside the plasma membrane, that surrounds and supports the bacterial cell?

Cell Wall

The _____ is composed of DNA and protein.

Chromatin

The cilia and flagella of eukaryotic cells are composed of _____.

microtubules

Which statement best explains the effect on membrane permeability of cholesterol and/or temperature?

Adding cholesterol reduces permeability because its steroid rings fill gaps in the hydrophobic membrane interior., Cholesterol's bulky steroid rings result in a denser membrane interior, making it more difficult for materials to pass through.

what would happen when ATP is added if the links connecting the microtubule doublets (shown) and the spokes connecting each doublet to the central pair of microtubules (not shown) were missing?

Adjacent doublets would slide past one another but no bending would occur. Bending occurs because the sliding motion is constrained by links and spokes, which are missing in this case.

_____ is/are identical in structure to centrioles.

Basal Bodies

Which molecules do not normally cross the nuclear membrane?

DNA ,All processes involving DNA take place in the nucleus.

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.

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

What is the most likely role of a cell that contains an extensive smooth ER?

It synthesizes large quantities of lipids.

Which organelle plays a role in intracellular digestion?

Lysosome

Which of the following cytoskeletal proteins are important in changing cell shape or location (any type of cell movement)?

Microfilaments and myosin are among the cytoskeletal proteins important in cell movement.

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?

Microtubules,

Which of these organelles carries out cellular respiration?

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

Which of these is the double membrane that encloses the nucleus?

Nuclear Envelope

The DNA-containing region of this bacterial cell is

Nucleoid

Where is a bacterial cell's DNA found?

Nucleoid region

Ribosomal subunits are manufactured by the _____.

Nucleolus

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, 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?

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

The _____ is a selective barrier, regulating the passage of material into and out of the cell.

Plasma Membrane, The plasma membrane regulates the passage of material into and out of the cell.

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

What is the function of a bacterium's capsule?

Protection

_____ are the sites of protein synthesis.

Ribosomes

In a bacterium, where are proteins synthesized?

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

Which of these manufactures cellular membranes by adding membrane proteins and phospholipids to its own membrane?

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

Where is calcium stored?

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

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

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

Which of the following statements about the nuclear envelope is false?

The nuclear envelope is continuous with the Golgi apparatus. This statement is false; the nuclear envelope is continuous with the endoplasmic reticulum.

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

The structure that regulates the passage of material into and out of this bacterial cell is

The plasma membrane is selectively permeable.

How are proteins transported throughout the endomembrane system?

The protein contains a molecular zip code that allows the protein to be shipped to the correct cellular compartment.

Which of the following is not a characteristic that chloroplasts and mitochondria share?

They are both part of the endomembrane system.

Why are lysosomes considered part of the endomembrane system?

They are formed from products synthesized by the endoplasmic reticulum and processed by the Golgi.

Molecular zip codes direct molecules to particular destinations in the cell. How are these signals read?

They bind to receptor proteins.

A prokaryotic cell is distinct from a eukaryotic cell because a prokaryotic cell lacks _____.

a membrane-bound nucleus

What three distinct elements make up the cytoskeleton in eukaryotic cells?

actin filaments, intermediate filaments, and microtubules

Where are the proteins that will be exported (excreted) from the cell made?

in ribosomes that attach to the endoplasmic reticulum

Which of the following most accurately summarizes the (1) structural and (2) functional properties of actin filaments, intermediate filaments, or microtubules?

intermediate filaments: (1) many subunit types; (2) one cellular role, Although intermediate filaments can be built from a variety of subunit types (keratin, vimentin, lamin, or others), they serve purely a structural role

Cells will phagocytize asbestos, but are not able to degrade it. As a result, asbestos fibers accumulate in _____.

lysosomes

Which of the following macromolecules leaves the nucleus of a eukaryotic cell through the pores in the nuclear membrane?

mRNA

The cell wall found in bacterial cells functions to _____.

protect the cell and provide shape and rigidity