Biology Quiz 2

Of the following, the _______, which is enclosed in a membrane, has the greatest amount of internal surface area. A) nucleus B) endoplasmic reticulum C) mitochondrion D) chloroplast E) ribosome

DNA strands are visualized using a(n) A) light microscope. B) electron microscope. C) dissecting microscope. D) centrifuge. E) thermocycler.

The organelles and biomolecules present in homogenized cells can be separated by centrifugation. Which of the following would be found at the top of a centrifugation gradient? A) Golgi B) Mitochondria C) Nuclei D) Ribosomes E) ATP molecules

Prokaryotes A) are surrounded by a cell membrane. B) have a nucleus. C) do not have ribosomes. D) have a cell wall similar in composition to that of plant cells. E) are larger than eukaryotic cells.

The proteins that make up the cytoskeleton of bacteria are similar to _______ in eukaryotic cells. A) proteases B) sterols C) actin D) transcription factors E) telomerases

Which structure is known for its lack of nucleic acids? A) The nucleus B) Mitochondrion C) Plant vacuole D) Ribosome E) Prokaryotic cell

Some proteins that are on the surface of mammalian cells contain carbohydrates. These proteins are synthesized by _______ and the carbohydrates are added in the _______. A) mitochondrial ribosomes; smooth endoplasmic reticulum B) the rough endoplasmic reticulum; Golgi apparatus C) cytoplasmic ribosomes; smooth endoplasmic reticulum D) Golgi apparatus; rough endoplasmic reticulum E) cytoplasmic ribosomes; cell membrane

Which statement about the nucleus of animal cells is true? A) It occupies the smallest volume of the cell. B) It powers the cell. C) It is enclosed by a single membrane. D) DNA in the nucleus combines with proteins. E) The nucleus is the site of protein synthesis.

The endomembrane system A) is present in prokaryotes. B) includes the endoplasmic reticulum and the mitochondria. C) includes the Golgi apparatus and the endoplasmic reticulum. D) functions to make ATP. E) does not exist in plant cells.

Which organelles are involved in energy conversions? A) Lysosomes B) Vacuoles C) Chloroplasts D) Peroxisomes E) Nuclei

Liver cells are exposed to radioactive amino acids, making all proteins synthesized during this time radioactive. The cells are then removed at 5-minute intervals and fractionated. Where in the cells is the radioactively-labeled enzyme lipase performing its intracellular functions? A) In the endoplasmic reticulum B) In the Golgi apparatus C) In lysosomes D) On ribosomes E) In the cytoskeleton

Which organelle(s) is/are found only in plants? A) Glyoxysomes B) Golgi C) Peroxisomes D) Mitochondria E) Endoplasmic reticulum

Which structure occupies the largest volume in a mature plant cell? A) Peroxisome B) Ribosome C) Chloroplast D) Vacuole E) Mitochondrion

Plastids are A) present in nearly all plant cells. B) always green. C) present in photosynthetic prokaryotes. D) present in all eukaryotes. E) very similar to mitochondria.

Which structure(s) is/are directly involved in the movement of organelles within a cell? A) Golgi apparatus B) Endoplasmic reticulum C) Mitochondrion D) Microtubules E) Intermediate filaments

Which protein(s) power(s) the movement of both cilia and vesicles within a cell? A) Myosin B) Actin C) Keratin D) Dynein only E) Kinesin and dynein

Cilia and eukaryotic flagella A) propel cells by rotation of structures. B) contain microfilaments. C) contain microtubules that are sufficient to drive movement. D) must have a motor protein that uses the energy of ATP hydrolysis to power movement. E) contain centrioles.

Amoeba proteus is injected with a drug that inhibits the formation of microtubules. What effect will this have on the organism's movement? A) It will survive, but it will not be able to move. B) It will show hyperactive movement. C) It will die, and thus will not move. D) It will only be able to move in one direction. E) The drug will have no effect on the organism's movement.

The extracellular matrix of animal cells A) is not involved in chemical signaling between cells. B) aids in blocking materials from passing between tissues. C) contains proteoglycans. D) contains cellulose. E) pigments the cells.

The presence of _______ means that substances must pass through, rather than between, the epithelial cells that form the lining of the small intestine. A) gap junctions B) tight junctions C) desmosomes D) plasmodesmata E) microtubules

Why do phospholipids spontaneously form bilayer structures, while oils form small droplets? A) Oils are not as hydrophobic as phospholipids are. B) The fatty acids in oils preclude bilayer formation. C) Oils are energy reserves of cells. D) Oils do not have the polar head group that phospholipids have. E) Oils and water do not mix.

Which statement about membrane proteins is true? A) Hydrophilic regions of integral membrane proteins are in contact with the interior of the bilayer. B) Peripheral membrane proteins may be associated with the phospholipid head groups. C) Integral membrane proteins are fixed in place. D) Some membrane proteins may have DNA attached to them. E) RNA is found as part of most membrane proteins' structure.

In addition to the lipid bilayer and proteins, membranes may contain _______ in the form of _______ and _______. A) nucleic acids; DNA; RNA B) carbohydrates; cellulose; starch C) triglycerides; fats; oils D) nucleotides; ATP; GTP E) carbohydrates; glycoproteins; glycolipids

In animals, cell recognition A) involves only glycolipids. B) is mediated by the lipid bilayer. C) involves soluble proteins. D) involves proteins in plasma membranes. E) is usually heterotypic.

Which molecule would diffuse across a phospholipid bilayer fastest, if there are no proteins associated with the bilayer? A) H2O B) NH4+ C) CH3COO- D) Na+ E) NH3

Osmosis is A) the movement of water across selectively permeable membranes. B) the active transport of water across membranes. C) the unidirectional diffusion of water across membranes. D) a process that is unaffected by solute concentrations inside cells. E) a process that requires energy.

If a suspension of red blood cells in an isotonic NaCl solution was suddenly diluted with pure water by a factor of 10, the cells would A) pump water out of the cell. B) lose water and shrink. C) swell and lyse (burst). D) take up water, but the cell walls would prevent bursting. E) remain as they are.

In facilitated diffusion, A) molecules may be transported against their concentration gradient. B) specific integral membrane proteins mediate transport. C) the rate of transport is independent of the concentration of the molecule transported. D) ATP is used. E) endocytosis is involved.

The sodium-potassium pump (or Na+-K+pump) A) is present in endomembranes. B) is an example of a secondary active transporter. C) results in the formation of an Na+ concentration gradient across the cell membrane. D) carries out facilitated diffusion. E) pumps K+ out of cells

Receptor-mediated endocytosis A) is nonspecific. B) allows small molecules to enter cells. C) results in the formation of clathrin-coated vesicles. D) directly involves the Golgi apparatus. E) is another name for phagocytosis.

Hormones are chemical signals that A) affect adjacent cells. B) work in prokaryotes. C) are autocrine signals. D) travel through circulatory systems. E) are paracrine signals.

A universal feature of receptors is that they A) undergo structural (shape) changes when the signal molecule is bound. B) are protein kinases. C) are present in the plasma membrane. D) are ion channel proteins. E) do not undergo structural (shape) changes when the signal molecule is bound

Which statement about receptors and enzymes is true? A) Most receptors and enzymes are nucleic acids. B) Both receptors and enzymes may be integral membrane proteins. C) Receptor ligands, like enzyme substrates, are altered during signal transduction. D) Receptors and enzymes are not specific for the molecules they bind. E) Receptors generally have enzymatic activity, whereas enzymes do not.

Chemical signal transduction pathways A) use nonspecific receptors. B) involve binding of the signal molecule to receptors. C) use receptors that are located only on the cytoplasm. D) use receptors that change the ligands they bind. E) all use G proteins.

Caffeine A) is structurally related to GDP. B) binds to a receptor in the brain. C) causes signal transduction by itself. D) is a signal. E) is a depressant.

Adenylyl cyclase A) is located in such a manner that cAMP is made outside of cells. B) makes cAMP from ATP with the liberation of phosphate (Pi). C) is inactivated by activated G proteins. D) makes cAMP from ATP with the liberation of pyrophosphate (PPi). E) is directly activated by receptors.

Which statement about a signal cascade is true? A) Glycogen phosphorylase in liver cells is always active. B) cAMP is referred to as a "first messenger." C) Epinephrine directly activates adenylyl cyclase. D) cAMP is referred to as a "second messenger." E) Adenylyl cyclase is a protein kinase.

Which step of the signal transduction cascade that results in glucose release during the "fight-or-flight" response involves factors other than a nucleotide? A) Phosphorylation of glycogen phosphorylase B) Activation of adenylyl cyclase C) Epinephrine binding to its receptor D) Activation of a G protein E) Inactivation of glycogen synthase

The phosphorylation of proteins by ATP A) is catalyzed by enzymes known as "protein kinases." B) always stimulates the activity of an enzyme. C) is catalyzed by adenylyl cyclase. D) is catalyzed by the epinephrine receptor. E) is catalyzed by G proteins.

Suppose the concentration of epinephrine in the bloodstream of an animal drops. The cyclic AMP concentration in liver cells would be expected to _______ because _______ activity would _______. A) increase; adenylyl cyclase; increase B) decrease; protein kinase; decrease C) decrease; phosphodiesterase; decrease D) increase; protein kinase; increase E) decrease; adenylyl cyclase; decrease