The degree to which a microscope enlarges the image of an object is called its magnification.
Missing Word
magnification
Magnification is how many times larger an image appears than the real object. A typical student light microscope magnifies up to about 400 times, or about 1,000 times with an oil immersion lens.
Category: Microscopy and Cell Theory
Question 2
Organisms whose cells lack a nucleus and other membrane-bound organelles, namely bacteria and archaea, are called prokaryotes.
Missing Word
prokaryotes
Prokaryotes are single-celled organisms in the domains Bacteria and Archaea. Their DNA lies in the nucleoid rather than inside a nuclear envelope.
Category: Prokaryotic Cells
Question 3
During conjugation, bacteria exchange genetic material through hairlike surface appendages called pili.
Missing Word
pili
Pili are thin protein appendages on the surface of many bacteria. During conjugation, a pilus links two cells so that DNA can pass from one to the other.
Category: Prokaryotic Cells
Question 4
The cytoplasm is the entire region of a cell between the plasma membrane and the nuclear envelope, including the organelles and the fluid around them.
Missing Word
cytoplasm
Cytoplasm includes the organelles plus the gel-like cytosol in which they are suspended. It is mostly water, and many metabolic reactions, including protein synthesis, take place there.
Category: Nucleus and Endomembrane System
Question 5
Inside the nucleus, DNA wound together with proteins forms a threadlike material called chromatin, which condenses into chromosomes before a cell divides.
Missing Word
chromatin
Chromatin is the combination of DNA and proteins that makes up the genetic material in the nucleus. Before division it coils tightly into compact chromosomes that can be moved to the new cells.
Category: Nucleus and Endomembrane System
Question 6
Protein synthesis is carried out by ribosomes, complexes of a large and a small subunit that are either free in the cytosol or bound to the endoplasmic reticulum.
Missing Word
ribosomes
Ribosomes read messenger RNA and link amino acids into proteins. They are made of ribosomal RNA and protein and are especially plentiful in cells that make large amounts of protein.
Category: Nucleus and Endomembrane System
Question 7
In a macrophage, a vesicle holding an engulfed bacterium fuses with a lysosome, whose digestive enzymes destroy the invader.
Missing Word
lysosome
A lysosome is a membrane-bound sac of digestive enzymes that work at low pH. Lysosomes break down macromolecules, worn-out organelles and engulfed pathogens.
Category: Nucleus and Endomembrane System
Question 8
The inner membrane of a mitochondrion is folded into many shelves called cristae, which greatly increase its surface area.
Missing Word
cristae
Cristae are the folds of the inner mitochondrial membrane. The space they enclose is the matrix, and the extra membrane area provides room for the proteins that make ATP.
Category: Organelles for Energy and Breakdown
Question 9
In a chloroplast, the fluid that surrounds the stacks of thylakoids is called the stroma.
Missing Word
stroma
The stroma is the fluid-filled space enclosed by the chloroplast's inner membrane. The thylakoids, which hold the light-capturing pigment chlorophyll, sit within it.
Category: Organelles for Energy and Breakdown
Question 10
In animal cells, the microtubule-organizing center near the nucleus, which holds a pair of centrioles, is called the centrosome.
Missing Word
centrosome
The centrosome organizes microtubules in animal cells and contains two centrioles set at right angles to each other. It is copied before cell division, although plant cells, which lack centrosomes, still divide.
Category: Cytoskeleton and Cell Connections
Question 11
Cells lining the small intestine have microvilli, tiny fingerlike projections of the plasma membrane that increase the area for absorbing nutrients.
Missing Word
microvilli
Microvilli are small folds of the plasma membrane supported by microfilaments. By adding surface area, they let intestinal cells absorb more nutrients.
Category: Cytoskeleton and Cell Connections
Question 12
A protein in the plasma membrane with carbohydrate chains attached to it is called a glycoprotein.
Missing Word
glycoprotein
A glycoprotein is a protein bonded to one or more carbohydrate chains, which face the outside of the cell. These carbohydrate markers help cells recognize one another.
Category: Cell Membrane
Question 13
A solution with a higher solute concentration than the fluid inside a cell is described as hypertonic, and a cell placed in it loses water.
Missing Word
hypertonic
Hypertonic describes a solution that has more dissolved solutes than the cell interior, so water leaves the cell by osmosis. An animal cell in a hypertonic solution shrivels, and a plant cell loses its firmness.
Category: Passive Transport
Question 14
Water pressing the plasma membrane against the cell wall creates turgor pressure, which keeps nonwoody plants upright.
Missing Word
turgor
Turgor pressure is the push of water inside a plant cell against its wall. When a plant runs short of water, turgor drops and the plant wilts.
Category: Passive Transport
Question 15
Neutrophils engulf and destroy microorganisms by phagocytosis, the form of endocytosis that takes in large particles such as whole cells.
Missing Word
phagocytosis
Phagocytosis, often called cell eating, wraps the plasma membrane around a large particle and pinches it off inside a vesicle. The vesicle then fuses with a lysosome, which digests its contents.
Category: Active Transport