Summarize the four key points of the cell theory.
The cell is the structural and functional unit of life. The activity of an organism depends on the activities of its cells. The activities of cells depend on their form and relative numbers of subcellular structures. Cells can only arise from other cells.
How would you explain the meaning of a "generalized cell" to a classmate?
It is the cell concept that includes structures and functions common to all cells.
What basic structure do all cellular membranes share?
All cellular membranes consist of a double layer of phospholipids in n which proteins are embedded.
What is the importance of the glycocalyx in cell interactions?
The sugar residues of the glycocalyx provide biological markers that allow cells to recognize each other.
Which two types of cell junctions would you expect to find between muscle cells of the heart?
The heart has desmosomes (anchoring junctions) that secure cardiac cells together as the heart works and gap junctions (communicating junctions) that allow ions to flow from cardiac cell to cardiac cell.
Phospholipid tails can be saturated or unsaturated (Chapter 2). This is true of phospholipds in plasma membranes as well. Which type--saturated or unsaturated--would make the membrane more fluid?
Unsaturated phospholipids would make the membrane more fluid. The double bonds cause the fatty acid chains to kink so that they cannot be packed closely and this makes the membrane more fluid.
What is the energy source for all types of diffusion?
Diffusion is driven by kinetic energy of the molecules.
What determines the direction of any diffusion process?
The relative concentration of the substance in different areas determines the direction of diffusion. Diffusion occurs from regions of high concentration to regions of low concentration.
What are the two types of facilitated diffusion and how do they differ?
In channel-mediated diffusion, the diffusing substance moves through a membrane channel. In carrier-mediated diffusion, the diffusing substance attaches to a membrane (protein) carrier that moves it across the membrane.
What happens when the Na+ -K+ pump is phosphorylated? When K+binds to the pump protein?
Phosphorylation of the Na+ -K+ pump causes the pump protein to change shape so that it "pumps" Na+ across the membrane. K+ binding to the pump protein triggers the release of the phosphate and the pump protein returns to its original shape.
As a cell grows, its plasma membrane expands. Does this membrane expansion involve endocytosis or exocytosis?
The plasma membrane expands as a result of exocytosis.
Phagocytic cells gather in the lungs, particularly in the lungs of smokers. What is the connection?
Phagocytic cells engulf debris, and a smoker's lungs would be laden with carbon particles and other debris from smoke inhalation.
Which vesicular transport process allows a cell to take in cholesterol from the extracellular fluid?
Cholesterol is taken in by receptor-mediated endocytosis.
What process establishes the resting membrane potential?
Diffusion of ions, mainly the diffusion of K+ from the cell through leakage channels, establishes the resting membrane potential.
Is the inside of the plasma membrane negative or positive relative to its outside in a polarized membrane of a resting cell?
In a polarized membrane of a resting cell, the inside is negative relative to its outside.
What term is used to indicate signaling chemicals that bind to membrane receptors? Which type of membrane receptor is most important in directing intracellular events by promoting formation of second messengers?
Signaling chemicals that bind to membrane receptors are called ligands. G protein-linked receptors direct intracellular events by promoting formation of second messengers.
Which organelle is the major site of ATP synthesis?
Mitochondria are the major sites of ATP synthesis.
What are three organelles involved in protein synthesis and how do these organelles interact in that process?
Ribosomes are the sites of protein synthesis. The rough ER provides a site for ribosome attachment, and its cistern package in vesicles the proteins made on the ribosomes for transport to the Golgi apparatus. The Golgi apparatus modifies and packages the proteins it receives for various destinations within or outside the cell.
Compare the functions of lysosomes and peroxisomes.
Thy lysosomal enzymes digest foreign substances engulfed by the cell, nonuseful or deteriorating organelles, or even the cell itself to prevent the buildup of cellular debris. The enzymes in peroxisomes detoxify harmful chemicals and neutralize free radicals.
How are microtubules and microfilaments related functionally?
Both microfilaments and microtubules are involved in organelle movements within the cell and/or movements of the cell as a whole.
Of microfilaments, microtubules, or intermediate filaments, which is most important in maintaining cell shape?
Intermediate filaments are the most important cytoskeletal elements in maintaining cell shape.
The major function of cilia is to move substances across the free cell surface. What is the major role of microvilli?
The major function of microvilli is to increase the cell's surface area for absorption of substances.
If a cell ejects or loses its nucleus, what is its fate and why?
If a cell loses its nucleus, it is doomed to die because it will be unable to make proteins, which include the enzymes needed for all metabolic reactions.
What is the role of the nucleoli?
Nucleoli are the site of synthesis of ribosomal units.
What is the importance of the histone proteins present in the nucleus?
Histone proteins provide the means to pack DNA in a compact, orderly way, and they play a role in gene regulations.
If one of the DNA strands being replicated "reads" CGAATG, what will be the base sequence of the corresponding DNA strand?
The base sequence of the corresponding strand will be GCTTAC.
During what phase of the cell cycle is DNA synthesized?
DNA is synthesized during the S phase.
What are the three events occurring in prophase that are undone in telophase?
Nuclear envelope breaks up, spindle forms, nucleoli disappear, and the chromosomes coil and condense.
Codons and anticodons are both three-base sequences. How do they differ?
Codons are three-base sequences in mRNA, each of which specifies an amino acid. Anticodons are three-base sequences in tRNA that are complementary to the codons specifying the amino acid they transport to the ribosome during protein synthesis.
How do the A,P, and E ribosomal sites differ functionally during protein synthesis?
The A site is the entry site for tRNA at the ribosome. The P site is where the tRNA carrying the growing polypeptide is located. The E site is the tRNA exit site from the ribosome.
What is the role of DNA in transcription?
DNA provides the coded instructions (is the template) for protein synthesis via the mRNA synthesized on it.
What is the importance of ubiquitin in the life of a cell?
Ubiquitin attaches to misfolded, damaged, or unneeded proteins, tagging them for destruction by proteasomes.
What is apoptosis and what is its importance in the body?
Apoptosis is a process of programmed cell death which rids the body of cells that are stressed, damaged, old, or no longer needed.
The smallest unit capable of life by itself is
the cell
The major types of lipid found in the plasma membranes are
cholesterol, phospholipids
Membrane junctions that allow nutrients or ions to flow from cell to cell are
gap junctions
The term used to describe the type of solution in which cells will lose water to their environment is
hypertonic
Osmosis always involves
a selectively permeable membrane, a difference in solvent concentration, diffusion
A physiologist observes that the concentration of sodium inside a cell is decidedly lower than that outside the cell. Sodium diffuses easily across the plasma membrane of such cells when they are dead, but not when they are alive. What cellular function that is lacking in dead cells explains the difference?
active transport (solute pumping)
The solute-pumping type of active transport is accomplished by
changes in shape and position of transport molecules in the plasma membrane
The endocytotic process in which a sampling of particulate matter is engulfed and brought into the cell is called
phagocytosis
The nuclear substance composed of histone proteins and DNA is
chromatin
The information sequence that determines the nature of a protein is the
gene
Mutations may be caused by
X rays, certain chemicals, radiation from ionizing radioisotopes
The phase of mitosis during which centrioles reach the poles and chromosomes attach to the spindle is
prophase
Final preparations for cell division are made during the life cycle subphase called
G2
The RNA synthesized on one of the DNA strands is
mRNA, tRNA, rRNA
The RNA species that travels from the nucleus to the cytoplasm carrying the coded message specifying the sequence of amino acids in the protein to be made is
mRNA
If DNA has a sequence of AAA, then a segment of mRNA synthesized on it will have a sequence of
UUU
A nerve cell and a lymphocyte are presumed to differ in their
specialized structure, genetic information
A pancreas cell makes proteins (enzymes) that it releases to the small intestine. Which of the following best describes the path of these proteins from synthesis to exocytosis at the pancreatic cell's plasma membrane (PM)?
rough ER to Golgi to PM
A gene is best defined as
a segment of DNA that carries instructions for the production of one polypeptide chain.
DNA is replicated during the ____ phase of the cell cycle
S
The resting membrane potential is mainly determined by
the differential permeability of the plasma membrane to K+ and other ions.
The mRNA start codon, AUG, matches up with a tRNA anticodon
UAC
Which nucleic acid molecules are involved in transcription but not translation in the synthesis of a particular polypeptide?
DNA
(DNA is copied into mRNA in transcription within the nucleus in the synthesis of a particular polypeptide)
Which type of membrane transport process uses ATP as a source of energy?
primary active transport
(Active transport uses ATP)
In which stage of mitosis do the chromosomes align along the cell equator?
metaphase
(In metaphase, the chromosomes cluster around the middle of the cell, with the centromeres aligned on the cell equator.)
Function:
Ribosome
synthesize protein
Ribosomes are found _____ and _____.
In the cytosol and on the endoplasmic reticulum
Cells of the body mainly use ____ for the selective endocytosis of most macromolecules.
receptor-mediated endocytosis
The primary site of ATP production in most cells is the
mitochondrion
T or F
At rest, the plasma membrane of most body cells are NOT polarized.
False
Pinocytosis is a type of ____
endocytosis
Function:
Lysosomes
contain digestive enzymes
Simple diffusion is best described as substances ____
moving passively down a concentration gradient.
(moving substances from an area of high concentration to one of low concentration does not require energy and is known as simple diffusion)
Function:
cytokeleton
support cellular structures
Definitely changes in the ____of the cell membrane can be seen in a cell that is becoming cancerous.
glycocalyx
Proteins in the cell membrane that bind hormones and relay messages into the interior of the cell ____
perform a function known as signal transduction
function:
peroxisomes
neutralize dangerous free radicals
function:
endoplasmic reticulum
fold, package, and modify proteins
function:
nucleolus
synthesize ribosomes
The underlying cause of Tay-Sachs disease is ____
the lack of the enzymes needed to break down a glycolipid abundant in nerve cell membranes
(Lysosomes swollen with undigested lipids in nerve cells from the lack of the enzymes needed to digest a certain glycolipid are the cause of Tay-Sachs disease.)
Crenation takes place when a cell is placed in _____
a hypertonic solution
(Cells placed in a hypertonic solution shrink from loss of water and are said to be crenated)
Cells may be said to be "sugar-coated" because of the presence of ____
glycocalyx
(The glycocalyx is made up of glycoproteins, which are proteins with carbohydrate side chains located on the outside surface of the cell membrane, thus causing the cell to appear "sugar-coated".)
T or F
Primary active transport is driven by secondary active transport.
False
A cell will swell, and likely burst, if it is placed in ____ solution
a hypotonic
Osmosis is
the diffusion of water across a membrane
T or F
Water can pass through the lipid bilayer via osmosis
True
Function:
Gap junctions
important for cell communication
Function:
Tight junctions
prevent molecules from passing through the extracellular space between adjacent cells
The outer boundary of a human cell is the
plasma membrane
Function:
Desmosomes
anchor junctions found in areas subject to pulling force
The basic structural and functional unit of living organisms is the
cell
During transcription, ____
DNA is used as a template to make RNA
The intracellular fluid packed with the organelles of a cell is called
cytoplasm
The cell membrane is composed mostly of
phospholipids and proteins
The smallest unit of life is the
cell
The interior of the cell membrane can be best described as
hydrophobic
Cell junctions that are important in cell communication are
gap junctions
if you walk into your house and smell dinner, you are experiencing ____
diffusion
A cell that is placed in a hypertonic solution will
crenate
____solutions contain a lower concentration of nonpenetrating particles than cells contain
hypotonic
A cell will "drink" small amounts of fluid and solutes using ____
pinocytosis
Specifically, which type of transport is driven by energy stored in gradients?
secondary active transport
How is active transport different from facilitated diffusion?
It moves against the concentration gradient.
In a cell, proteins are synthesized at the
ribosome
In a cell, ATP is produced by the ____
mitochondrian
Which organelle detoxifies a number of toxic substances?
Peroxisome
Which type of cytoskeleton attaches to desmosomes to resist pulling forces exerted on the cell?
Intermediate filaments
These organelles are fatal to the cell if they burst
lysosomes
Mitosis is division of the ____
nucleus
Cytokenesis is defined as
the division of cytoplasm
DNA is replicated during which phase of interphase?
S phase
If a cell has 8 chromosomes before mitosis, each daughter cell will have how many chromosomes?
8
Semiconservative replication refers to
each new DNA molecule consisting of one old and one new nucleotide strand
What is the function of small interfering RNA's?
They interfere with viral replication