Light microscopes can be used to observe living cells, while standard electron microscopes cannot.
Correct Answer
True
True. Preparing a specimen for an electron microscope kills the cells, and the electron beam must travel in a vacuum, so living material cannot be viewed. Light microscopes can show living cells, although stains used to reveal details often kill them.
Category: Microscopy and Cell Theory
Question 2
According to the cell theory, new cells can arise from nonliving matter.
Correct Answer
False
False. The cell theory states that all new cells arise from existing cells. Its other two parts are that all living things are made of one or more cells and that the cell is the basic unit of life.
Category: Microscopy and Cell Theory
Question 3
Matthias Schleiden and Theodor Schwann proposed the unified cell theory in the late 1830s.
Correct Answer
True
True. The botanist Matthias Schleiden and the zoologist Theodor Schwann, studying plant and animal tissues, proposed that all organisms are made of cells. Their work became the basis of the unified cell theory.
Category: Microscopy and Cell Theory
Question 4
All cells, prokaryotic and eukaryotic, share four components: a plasma membrane, cytoplasm, DNA and ribosomes.
Correct Answer
True
True. Every cell has a plasma membrane that encloses cytoplasm, DNA that carries its genetic information, and ribosomes that make proteins. Prokaryotes differ from eukaryotes mainly in lacking a nucleus and other membrane-bound organelles.
Category: Prokaryotic Cells
Question 5
Archaea have cell walls made of peptidoglycan, just as bacteria do.
Correct Answer
False
False. Peptidoglycan is found in the cell walls of bacteria but not in archaea or eukaryotes. Archaeal cell walls, where present, are built from other molecules, which is one way the two prokaryotic domains differ.
Category: Prokaryotic Cells
Question 6
Prokaryotic cells typically have larger diameters than eukaryotic cells.
Correct Answer
False
False. Prokaryotic cells are usually about 0.1 to 5.0 micrometers across, while eukaryotic cells are usually about 10 to 100 micrometers. Their small size gives prokaryotes a high surface area to volume ratio, so materials move through them quickly.
Category: Prokaryotic Cells
Question 7
Rough endoplasmic reticulum is studded with ribosomes and modifies newly made proteins, such as by folding them and adding sugars.
Correct Answer
True
True. Ribosomes attached to the rough endoplasmic reticulum release new proteins into its interior, where they are folded and often given carbohydrate chains. The rough endoplasmic reticulum also makes phospholipids for cell membranes.
Category: Nucleus and Endomembrane System
Question 8
The digestive enzymes inside lysosomes work best at a high, basic pH.
Correct Answer
False
False. Lysosomal enzymes work best at a low, acidic pH, which is maintained inside the lysosome. This helps protect the cell, because the enzymes work poorly if they leak into the less acidic cytoplasm.
Category: Nucleus and Endomembrane System
Question 9
Mitochondria and chloroplasts each contain their own DNA and ribosomes.
Correct Answer
True
True. Both organelles carry their own DNA and ribosomes, much like bacteria. This is a key piece of evidence for the endosymbiotic theory, which holds that both descended from bacteria engulfed by ancestral host cells.
Category: Organelles for Energy and Breakdown
Question 10
A large central vacuole that maintains pressure against the cell wall is a typical feature of animal cells.
Correct Answer
False
False. The large central vacuole is a typical feature of plant cells. It holds water and pushes the membrane against the cell wall, and when it shrinks from water loss the plant wilts.
Category: Organelles for Energy and Breakdown
Question 11
Plant cell walls are made mainly of cellulose, a polysaccharide built from glucose.
Correct Answer
True
True. Cellulose is a long, straight chain of glucose units, and it gives plant cell walls their strength. The rigid wall protects the plant cell and helps it keep its shape.
Category: Organelles for Energy and Breakdown
Question 12
Keratin is a protein that forms one type of intermediate filament.
Correct Answer
True
True. Keratin is a fibrous protein that makes up one type of intermediate filament, and it also strengthens hair, nails and the outer skin. Intermediate filaments bear tension and help anchor organelles in place.
Category: Cytoskeleton and Cell Connections
Question 13
Desmosomes are channels that let ions and nutrients pass directly between the cytoplasm of adjacent animal cells.
Correct Answer
False
False. Gap junctions are the channels that connect the cytoplasm of adjacent animal cells. Desmosomes act like spot welds that hold cells together in sheets in tissues that stretch, such as skin and heart muscle.
Category: Cytoskeleton and Cell Connections
Question 14
Carbohydrates attached to the plasma membrane are found on its outer surface, facing away from the cytoplasm.
Correct Answer
True
True. Membrane carbohydrates are bound to proteins as glycoproteins or to lipids as glycolipids on the outside of the cell. Along with membrane proteins, they help cells recognize one another.
Category: Cell Membrane
Question 15
Peripheral proteins span the full width of the phospholipid bilayer.
Correct Answer
False
False. Peripheral proteins sit on the inner or outer surface of the membrane, attached to integral proteins or phospholipids. Integral proteins are the ones embedded in the bilayer, and many of them span it completely.
Category: Cell Membrane
Question 16
Oxygen and carbon dioxide cross the plasma membrane by simple diffusion.
Correct Answer
True
True. Oxygen and carbon dioxide are small and nonpolar, so they slip directly through the hydrophobic core of the bilayer down their concentration gradients. Ions and polar molecules such as glucose need transport proteins to cross.
Category: Passive Transport
Question 17
Facilitated diffusion uses ATP to move substances against their concentration gradient.
Correct Answer
False
False. Facilitated diffusion is a form of passive transport that uses channel or carrier proteins to move substances down their concentration gradient with no energy input. Moving a substance against its gradient requires active transport.
Category: Passive Transport
Question 18
Heavier molecules diffuse faster than lighter molecules under the same conditions.
Correct Answer
False
False. Heavier molecules move more slowly and therefore diffuse more slowly than lighter ones. The rate of diffusion also increases with a steeper concentration difference and a higher temperature, and decreases in a denser solvent.
Category: Passive Transport
Question 19
Osmosis is the diffusion of dissolved solutes across a semipermeable membrane.
Correct Answer
False
False. Osmosis is the diffusion of water across a semipermeable membrane. Water moves from where it is more concentrated, the side with fewer solutes, toward where it is less concentrated, while the solutes that cannot cross stay put.
Category: Passive Transport
Question 20
Secondary active transport uses the energy stored in an electrochemical gradient that primary active transport created.
Correct Answer
True
True. Primary active transport, such as the sodium-potassium pump, uses ATP directly to build an ion gradient. In secondary active transport, ions flowing back down that gradient carry other substances, such as glucose or amino acids, into the cell.
Category: Active Transport