Ch. 3 Cells: The Living Unit Flashcards
What is the composition of the plasma membrane?
A double layer of phospholipids with embedded proteins
Which process involves the diffusion of molecules down their concentration gradient?
Passive membrane transport
What distinguishes primary active transport from secondary active transport?
Primary active transport directly uses ATP
What is membrane potential?
The voltage difference across a cell membrane
What role do cell adhesion molecules play?
They allow cells to interact with their environment
What is the function of mitochondria?
Producing ATP
What are the two main types of cellular extensions?
Cilia and microvilli
What are the phases of the cell cycle?
Interphase and mitotic phase
What is the role of messenger RNA (mRNA)?
Carrying instructions from DNA for building proteins
What are the three major regions of a generalized cell?
Plasma membrane, cytoplasm, and nucleus
Plasma membrane
A double layer of phospholipids with embedded proteins that surrounds the cell
What is the primary function of the plasma membrane?
To regulate the movement of substances in and out of the cell
What is passive membrane transport?
The diffusion of molecules down their concentration gradient
Active transport
The movement of molecules across a cell membrane using ATP
What establishes the membrane potential?
Selective diffusion
Membrane potential
The voltage difference across a cell’s plasma membrane
Cytosol
The fluid component of the cytoplasm
Ribosome
An organelle that synthesizes proteins
Nucleus
The organelle that contains the cell’s genetic material
Gene
A segment of DNA that contains instructions for building a protein
Apoptosis
The process of programmed cell death
What is the importance of ubiquitin-dependent degradation?
It disposes of unneeded soluble proteins
Which of the following is NOT a point of cell theory?
All organisms are made of multiple cells.
What principle states that the activities of cells are dictated by their shapes and subcellular structures?
Principle of complementarity of structure and function
What process do most body cells use to arise?
Mitosis
Which type of cell arises by meiosis?
Sperm and ovum (egg) cells
What are the two major fluid compartments separated by the plasma membrane?
Intracellular fluid and extracellular fluid
Why is the term ‘plasma membrane’ preferred over ‘cell membrane’ in the context of this book?
Because nearly all cellular organelles are enclosed in a membrane
What role does the plasma membrane play in cellular activities?
A dynamic role
Intracellular fluid
The fluid within cells.
Extracellular fluid
The fluid outside cells.
Receptor-mediated endocytosis
The type of endocytosis in which engulfed particles attach to receptors before endocytosis occurs.
Plasma membrane
Membrane, composed of phospholipids, cholesterol, and proteins, that encloses cell contents; outer limiting cell membrane.
Anaphase
Third stage of mitosis, meiosis I, and meiosis II in which chromosomes move toward each pole of a cell.
Exocytosis
Mechanism by which substances are moved from the cell interior to the extracellular space as a secretory vesicle fuses with the plasma membrane.
Centrosome
A region near the nucleus that contains paired organelles called centrioles.
Basal bodies
An organelle structurally identical to a centriole and forming the base of a cilium or flagellum.
Passive processes
Membrane transport processes that move substances down their concentration gradients (e.g., diffusion). They are driven by kinetic energy and so do not require cellular energy (such as ATP).
Endocytosis
Means by which fairly large extracellular molecules or particles enter cells, e.g., phagocytosis, pinocytosis, receptor-mediated endocytosis.
Peroxisomes
Membranous sacs in cytoplasm containing powerful oxidase enzymes that use molecular oxygen to detoxify harmful or toxic substances, such as free radicals.
Primary active transport
A type of active transport in which the energy needed to drive the transport process is provided directly by hydrolysis of ATP.
Nucleus
(1) Control center of a cell; contains genetic material; (2) clusters of neuron cell bodies in the CNS; (3) center of an atom; contains protons and neutrons.
Centrioles
Minute body found in pairs near the nucleus of the cell; active in cell division.
Hyperplasia
Accelerated cell division, e.g., in anemia, the bone marrow produces red blood cells at a faster rate.
Carriers
A transmembrane protein that changes shape to envelop and transport a polar substance across the cell membrane.
Endoplasmic reticulum (ER)
Membranous network of tubular or saclike channels in the cytoplasm of a cell.
Interphase
One of two major periods in the cell life cycle; includes the period from cell formation to cell division.
Membrane receptors
A large, diverse group of integral proteins that serve as binding sites for signaling molecules.
Chromosomes
Barlike bodies of tightly coiled chromatin; visible during cell division.
M (mitotic) phase
One of two major periods in the cell life cycle; involves the division of the nucleus (mitosis) and the division of the cytoplasm (cytokinesis).
Amoeboid motion
The flowing movement of the cytoplasm of a phagocyte as it moves across a surface.
Necrosis
Death or disintegration of a cell or tissues caused by disease or injury.
Cytosol
Viscous, semitransparent fluid substance of cytoplasm in which other elements are suspended.
Channels
A transmembrane protein that forms an aqueous pore, allowing substances to move from one side of the membrane to the other.
Pinocytosis
Engulfing of extracellular fluid by cells.
Osmosis
Diffusion of a solvent through a selectively permeable membrane from a dilute solution into a more concentrated one.
Mitosis
Process during which the chromosomes are redistributed to two daughter nuclei; nuclear division. Consists of prophase, metaphase, anaphase, and telophase.
Signal sequence
A short peptide segment present in a protein being synthesized that causes the associated ribosome to attach to the membrane of rough ER.
Isotonic
A solution with a concentration of nonpenetrating solutes equal to that found in the reference cell.
Multinucleate
Cell with more than one nucleus, e.g., skeletal muscle cells, osteoclasts.
Microfilaments
One of three types of cytoskeletal elements; thin strands of the protein actin.
Simple diffusion
The unassisted transport across a plasma membrane of a lipid-soluble or very small particle.
Cell cycle
Series of changes a cell goes through from the time it is formed until it has reproduced itself.
Exons
Amino acid–specifying informational sequences (separated by introns) in the genes of higher organisms.
Osmolarity
The number of solute particles present in 1 liter of a solution.
Nucleoli
Dense spherical bodies in the cell nucleus involved with ribosomal RNA (rRNA) synthesis and ribosomal subunit assembly.
Desmosomes
Cell junction composed of thickened plasma membranes joined by filaments.
Tonicity
A measure of the ability of a solution to cause a change in cell shape or tone by promoting osmotic flows of water.
G protein
Protein that relays signals between extracellular first messengers (such as hormones or neurotransmitters) and intracellular second messengers (such as cyclic AMP) via an effector enzyme.
Cytokinesis
The division of cytoplasm that occurs after the cell nucleus has divided.
Secondary active transport
A type of active transport in which the energy needed to drive the transport process is provided by the electrochemical gradient of another molecule (which moves “downhill” through the transport protein at the same time as another molecule is moved “uphill” against its gradient). Also called cotransport or symport (when the two transported molecules move in the same direction) or antiport (when the two transported molecules move in opposite directions).
Autolysis
Process of autodigestion (self-digestion) of cells, especially dead or degenerate cells.
Codon
The three-base sequence on a messenger RNA molecule that provides the genetic information used in protein synthesis; codes for a given amino acid.
Transfer RNA (tRNA),
Short-chain RNA molecules that transfer amino acids to the ribosome.
Active processes
(1) Membrane transport processes for which ATP is directly or indirectly required, e.g., solute pumping and endocytosis. (2) “Active transport” also refers specifically to solute pumping.
Organelles
Small subcellular structures (ribosomes, mitochondria, and others) that perform specific functions for the cell as a whole.
Microvilli
Tiny projections on the free surfaces of some epithelial cells; increase surface area for absorption.
Atrophy
Reduction in size or wasting away of an organ or cell resulting from disease or lack of use.
Cytoplasm
The cellular material surrounding the nucleus and enclosed by the plasma membrane.
Hypertonic
Excessive, above normal, tone or tension.
Genetic code
Refers to the rules by which the base sequence of a DNA gene is translated into protein structures (amino acid sequences).
Metaphase
Second stage of mitosis, meiosis I, and meiosis II.
Tight junction
Area where plasma membranes of adjacent cells are tightly bound together, forming an impermeable barrier.
Vesicular transport
Transport of large particles and macromolecules into or out of a cell or between its compartments in membrane-bound sacs.
Lysosomes
Organelles that originate from the Golgi apparatus and contain strong digestive enzymes.
Systemic
Pertaining to the whole body.
Phagosome
Vesicle formed as a result of phagocytosis.
Fluid mosaic model
A depiction of the structure of the membranes of a cell as phospholipid bilayers in which proteins are dispersed.
Transcription
The transfer of genetic code information from a DNA base sequence to the complementary base sequence of an mRNA molecule; the first major step in polypeptide synthesis.
Telophase
The final phase of mitosis, meiosis I, and meiosis II; begins when migration of chromosomes to the poles of the cell has been completed and ends with the formation of two daughter nuclei.
Hypertonic solutions
A solution that has a higher concentration of nonpenetrating solutes than the reference cell; having greater osmotic pressure than the reference solution (blood plasma or interstitial fluid).
Microtubules
One of three types of cytoskeletal elements; hollow tubes made of the spherical protein tubulin.
Extracellular matrix
Nonliving material in connective tissue consisting of ground substance and fibers; separates the living cells.
Diffusion
The spreading of particles in a gas or solution with a movement toward uniform distribution of particles; driven by kinetic energy.
Introns
Noncoding segment or portion of DNA that ranges from 60 to 100,000 nucleotides long.
Golgi apparatus
Membranous system close to the cell nucleus that packages protein secretions for export, packages enzymes into lysosomes for cellular use, and modifies proteins destined to become part of cellular membranes.
Extracellular fluid (ECF)
Internal fluid located outside cells; includes interstitial fluid, blood plasma, and cerebrospinal fluid.
Ribosomes
Cytoplasmic organelles at which proteins are synthesized.
Chromatin
Strands of DNA (genes) and associated proteins; forms chromosomes when condensed (tightly coiled).
Cisterns
Any cavity or enclosed space serving as a reservoir.
Cytoskeleton
Literally, cell skeleton. An elaborate series of structural proteins running through the cytosol, supporting cellular structures and providing the machinery to generate various cell movements.
Permeability
A measure of the ability of molecules and ions to pass through a membrane.
Hydrostatic pressure
Pressure of fluid in a system.
Apoptosis
A process of controlled cellular suicide; eliminates cells that are unneeded, stressed, or aged.
Gene
One of the biological units of heredity located in DNA; transmits hereditary information.
Cell differentiation
The development of specific and distinctive features in cells, from a single cell (the fertilized egg) to all the specialized cells of adulthood.
Pores
The surface opening of the duct of a sweat gland.
Cyclic AMP
Intracellular second messenger that mediates the effects of the first (extracellular) messenger (hormone or neurotransmitter); formed from ATP by a plasma membrane enzyme (adenylate cyclase).
Mitochondria
Cytoplasmic organelles responsible for ATP generation for cellular activities.
Concentration gradient
The difference in the concentration of a particular substance between two different areas.
Gap junction
A passageway between two adjacent cells; formed by transmembrane proteins called connexons.
Membrane potential
Voltage across the plasma membrane.
Ribosomal RNA (rRNA)
A constituent of ribosomes that assists in protein synthesis.
Aquaporins (AQPs)
Transmembrane proteins that form water channels.
Messenger RNA (mRNA)
Long nucleotide strands that reflect the exact nucleotide sequences of the genetically active DNA and carry the DNA’s message.
Nuclear envelope
The double membrane barrier of a cell nucleus.
Cells
Structural unit of all living things.
Anticodon
The three-base sequence complementary to the messenger RNA (mRNA) codon.
Free radicals
Highly reactive chemicals with unpaired electrons that can scramble the structure of proteins, lipids, and nucleic acids.
Hypotonic solutions
A solution that is more dilute (containing fewer nonpenetrating solutes) than the reference cell. Cells placed in hypotonic solutions plump up rapidly as water diffuses into them.
Ligand
Signaling chemicals that bind specifically to membrane receptors.
Glycocalyx
A layer of externally facing glycoproteins and glycolipids (a “cell coat”) on or near a cell’s plasma membrane; its components determine blood type and are involved in cellular interactions.
Phagocytosis
Engulfing of solids by phagocytic cells.
DNA
DeoxyriboNucleic Acid is a nucleic acid found in all living cells; it carries the organism’s hereditary information.
Osmotic pressure
A measure of the tendency of a solvent to move into a more concentrated solution.
Nucleosomes
Fundamental unit of chromatin; consists of a strand of DNA wound around a cluster of eight histone proteins.
Prophase
The first stage of mitosis, meiosis I, and meiosis II. The chromosomes become visible, the nuclear envelope breaks down, and a spindle forms.
S phase
The part of the interphase period of the cell cycle in which DNA replicates itself, ensuring that the two future cells will receive identical copies of genetic material.
Vesicle
A small liquid-filled sac or bladder.
Translation
The second major step in the transfer of genetic code information, in which the information carried by mRNA is decoded and used to assemble polypeptides.
Flagella
Long, whiplike cellular extension containing microtubules; propels sperm and some single-celled eukaryotes.
Sodium-potassium pump
A primary active transport system that simultaneously drives Na+ out of the cell against a steep gradient and pumps K+ back in. Also called Na+-K+ ATPase.
Cilia
Tiny, hairlike projections of a cell; may move in a wavelike manner to propel substances across the exposed cell surface.
Resting membrane potential
The voltage that exists across the plasma membrane during the resting state of an excitable cell; typically ranges from −50 to −90 millivolts depending on cell type.
Glycolipids
A lipid with one or more covalently attached sugars.
Second messengers
Intracellular molecule generated by the binding of a chemical (e.g., hormone or neurotransmitter) to a receptor protein; mediates intracellular responses to the chemical messenger.
Facilitated diffusion
Passive transport process used by certain large or charged molecules (e.g., glucose, Na+) that are unable to pass through the plasma membrane unaided. Involves movement through channels or movement facilitated by a membrane carrier.
