Mastering Biology Chapter 6

What is the most likely pathway taken by a newly synthesized protein that will be secreted by a cell? A) ER →Golgi →vesicles that fuse with plasma membrane B) ER →lysosomes →vesicles that fuse with plasma membrane C) ER →Golgi →nucleus D) nucleus →ER →Golgi E) Golgi →ER →lysosome

A)

Which molecules do not normally cross the nuclear membrane? A) DNA B) Proteins C) mRNA D) Nucleotide triphosphates

A); All processes involving DNA take place in the nucleus

Where is calcium stored? A) smooth endoplasmic reticulum B) rough endoplasmic reticulum C) microtubules D) centrioles E) mitochondria

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

Which of these are hollow rods that shape and support the cell? A) microtubules B) microfilaments C) plasma membrane D) peroxisomes E) chloroplasts

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

Which of these organelles produces H2O2 as a by-product? A) peroxisome B) centrioles C) nucleus D) flagellum E) mitochondrion

A); Peroxisomes produce hydrogen peroxide as a by-product of their metabolic processes

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? A) Only one of the two fusion proteins possesses a nuclear localization signal. B) The cytoplasmic protein contains a nuclear localization signal. C) One of the fusion proteins entered the nucleus by passive transport. D) Nucleoplasmin does not have a nuclear localization signal.

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

The _____ is a selective barrier, regulating the passage of material into and out of the cell. A) plasma membrane B) nuclear envelope C) lysosome D) nucleus E) chloroplast

A); The plasma membrane regulates the passage of material into and out of the cell

Which structure is not part of the endomembrane system? A) plasma membrane B) chloroplast C) Golgi apparatus D) nuclear envelope E) ER

B)

Which of these organelles carries out cellular respiration? A) chromatin B) mitochondrion C) smooth endoplasmic reticulum D) nucleolus E) ribosomes

B); Mitochondria convert the chemical energy of organic molecules to chemical energy in the form of ATP

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? A) Osmosis B) Active transport C) Passive transport

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

_____ is/are identical in structure to centrioles. A) Mitochondria B) Nuclear envelopes C) Basal bodies D) Microfilaments E) Chromatin

C); Basal bodies and centrioles have identical structures.

Which of the following correctly matches an organelle with its function? A) nucleus ... cellular respiration B) mitochondrion ... photosynthesis C) central vacuole ... storage D) lysosome ... movement E) ribosome ... manufacture of lipids

C); But remember, plant cells have a central vacuole, whereas most animal cells have several smaller vacuoles located throughout the cytoplasm

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

C); Fluorescent tags make the location of the proteins easy to visualize

Which of the following are common traits of chloroplasts and mitochondria? A) Both are found in plant and animal cells. B) Both are surrounded by a single membrane. C) Both have their own DNA. D) Both reproduce by meiosis. E) Proteins for both are synthesized on ribosomes in the rough ER.

C); Mitochondria and chloroplasts contain their own DNA and ribosomes

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

C);This statement is false; the nuclear envelope is continuous with the endoplasmic reticulum

Which one of the following statements about the endomembrane system is correct? A) Most of the phospholipids of the endomembrane system are synthesized in the mitochondria. B) The endoplasmic reticulum is continuous with the plasma membrane. C) Mitochondria function in the modification and sorting of lipids and proteins. D) Proteins that will be secreted from the cell are likely to be found in closed spaces bounded by membranes of the endomembrane system. E) Ribosomes move lipids and proteins among the different organelles of the endomembrane system.

D); Proteins that will be secreted are always enclosed by some membrane of the endomembrane system until they are secreted.

Ribosomal subunits are manufactured by the _____. A) peroxisome B) lysosome C) smooth endoplasmic reticulum D) nucleolus E) rough endoplasmic reticulum

D); Ribosomes are manufactured by the nucleolus

Which cell would be best for studying lysosomes? A) muscle cell B) nerve cell C) bacterial cell D) leaf cell of a plant E) phagocytic white blood cell

E)

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

E); As membrane proteins grow from ribosomes on rough ER, the proteins are embedded into the rough ER membrane

The _____ is composed of DNA and protein. A) ribosome B) flagellum C) centriole D) mitochondrion E) chromatin

E); Chromatin is composed of DNA and protein

_____ are the sites of protein synthesis. A) Microfilaments B) Peroxisomes C) Mitochondria D) Golgi apparatuses E) Ribosomes

E); Ribosomes are the site of protein synthesis.

The primary role of _____ is to bind animal cells together. A) tight junctions B) the cytoskeleton C) plasmodesmata D) gap (communicating) junctions E) desmosomes

E); The primary role of desmosomes (anchoring junctions) is to bind cells together

Which of these cell junctions form a barrier to the passage of materials? A) desmosomes (anchoring junctions) B) gap (communicating) junctions C) plasmodesmata D) keratin fibers E) tight junctions

E); Tight junctions form a barrier that prevents fluids from moving between cells.

_____ aid in the coordination of the activities of adjacent animal cells. A) Plasmodesmata B) Desmosomes C) Tight junctions D) Keratin fibers E) Gap (communicating) junctions

E);Gap junctions allow for the passage of material between cells, thus facilitating communication between these cells.

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.