Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
37 Cards in this Set
- Front
- Back
|
Define cell |
Cells are the basic structural and functional unit of all living organisms |
|
|
3 major regions of a generalized cell and their functions |
-plasma membrane: encloses cell contents, mediates exchanges with extracellular environment, and plays a role in cellular communication -cytoplasm intracellular fluid that is packed with organelles -nucleus: controls cellular activities and lies near the cell's center |
|
|
Describe chemical composition of the plasma membrane and relate it to membrane functions |
-the fluid mosaic model depicts the plasma membrane as a fluid bilayer of lipids (phospholipids, cholesterol, and glycolipids) within which proteins are inserted -lipids have both hydrophilic and hydrophobic regions resulting in a self-orienting property, which encourages biological membranes to self-assemble into closed, generally spherical, structures and to reseal themselves quickly when torn -majority of membrane phospholipids are unsaturated, a condition which kinks their tails (increasing the space between them) and increases membrane fluidity |
|
|
Compare structure and function of tight junctions, desmosomes, and gap junctions |
-in a tight junction, a series of integral proteins molecules in the plasma membranes of adjacent cells fuse together, forming an impermeable junction that encircles the cell -desmosomes are anchoring junction, mechanical couplings scattered like rivets along the sides of abutting cells that prevent their separation. Desmosomes not only bing neighboring cells together, they also contribute to an arrangement that distributes tension throughout a cellular sheet and reduces the chances of tearing -a gap junction is a communicating junction between adjacent cells, cells are connected by hollow cylinders called connexons
|
|
|
Membrane transport: active processes |
Whenever a cell uses the bond energy of ATP to move solutes across the membrane, the process is referred to as active. Substances moved actively across the plasma membrane are usually unable to pass through the channels, incapable of dissolving in the lipid bilayer, or unable to move down its concentration gradient. Two major mechanisms of active membrane transport: active transport and vesicular transport |
|
|
Simple diffusion |
-energy source: kinetic energy -net movement of particles (ions, molecules, etc.) from an area of their higher concentration to an area of their lower concentration, that is, along their concentration gradient -ex: movement of fats, oxygen, carbon dioxide through the lipid portion of the membrane |
|
|
Facilitated diffusion |
-energy source: kinetic energy -same as simple diffusion, but the diffusion substance is attached to a lipid-soluble membrane carrier protein or moves through a membrane channel -ex: movement of glucose and some ions into cells |
|
|
Osmosis |
-energy source: kinetic energy -simple diffusion of water through a selectively permeable membrane -ex: movement of water into and out of cells directly through the lipid phase of the membrane or via membrane pores (aquaporins) |
|
|
Filtration |
-energy source: hydrostatic pressure -movement of water and solutes through a semipermeable membrane (either through the plasma membrane or between cells) from a region of higher hydrostatic pressure to a region of lower hydrostatic pressure, that is, along a pressure gradient -ex: movement of water, nutrients, and gases through a capillary wall; formation of kidney filtrate |
|
|
Describe membrane potential and explain how the resting membrane potential is maintained |
The resting membrane potential is largely determined by K+ (potassium) because the membrane is much more permeable to K+ than to Na+ (sodium) at rest. K+ moves more easily across the membrane by diffusing through membrane leakage channels. The net effect of this K+ movement is that the outside membrane face becomes more electrically positive (more positive ions build up) than the inside, which is relatively more negative. The active transport of sodium and potassium ions (in a ratio of 3:2) by the Na+K+ pump maintains these conditions.
*K+ goes out of cell, Na+ goes into cell |
|
|
Describe the role of the glycocalyx when cells interact with their environment |
-The glycocalyx is a glycoprotein-polysaccharide covering that surrounds the external surface of some cell's plasma membranes (fuzz-like coat) -whether cells interact directly or indirectly with other cells the glycocalyx is always involved. The best understood of the participating glycocalyx molecules fall into two large families- cell adhesion molecules and plasma membrane receptors |
|
|
Cell adhesion molecules, CAMs (part of glycocalyx) |
-play key roles in embryonic development and wound repair (situations where cell mobility is important) and in immunity -molecular "velco" that cells use to anchor themselves to molecules in extracellular space and to each other -the "arms" that migrating cells use to haul themselves past one another -SOS signals sticking out from the blood vessel lining that rally protective white blood cells to a nearby infected or injured area -mechanical sensors that respond to local tension at the cell surface by stimulating synthesis or degradation of adhesive membrane junctions -transmitters of intracellular signals that direct cell migration, proliferation, and specialization |
|
|
List several roles of membrane receptors and that of voltage-sensitive membrane channel proteins |
-contact signaling: the actual coming together and touching of cells is the means by which cells recognize one another. It is particularly important for normal development and immunity -chemical signaling: signaling chemicals that bind specifically to plasma membrane receptors are called ligands. Among these ligands are most neurotransmitters, hormones, and paracrines -activated membrane receptors act as catalysts, regulate channels, or like G protein-linked receptors, act through second messengers such as cyclic AMP and CA2+. Ligand binding results in changes in protein structure or function within the targeted cell |
|
|
Describe the composition of the cytosol |
The cytosol is the viscous, semitransparent fluid in which the other cytoplasmic elements are suspended. It is a complex mixture with properties of both a colloid and a true solution. Dissolved in the cytosol, which is largely water, are proteins, salts, sugars, and a variety of other solutes |
|
|
Define Inclusions |
Inclusions are chemical substances that may or may not be present in the cytoplasm, depending on cell type. Examples include stored nutrients, such as the glycogen granules abundant in liver and muscle cells, lipid droplets common in fat cells; pigment (melanin) granules seen in certain cells of skin and hair; water-containing vacuoles; and crystals of various types |
|
|
Mitochondria: structure and function |
-organelles limited by a double membrane; outer membrane is smooth and featureless, but the inner membrane folds inward, forming shelflike cristae that protrude into the matrix, the gel-like substance within the mitochondrion -power plants of a cell, sites of ATP formation -their internal enzymes carry out the oxidative reactions of cellular respiration -contain their own DNA and RNA and are able to reproduce themselves -widely believed that mitochondria arose from bacteria that invaded the ancient ancestors of plant and animal cells |
|
|
Ribosomes: structure and function |
-small, dark-staining granules composed of proteins and a variety of RNA called ribosomal RNA. Each ribosome has two globular subunits that fit together like the body and cap of an acorn -sites of protein synthesis -some float freely in cytoplasm, others are attached to membranes forming a complex called the rough endoplasmic reticulum |
|
|
Endoplasmic reticulum: structure and function |
-extensive system of interconnected tubes and parallel membranes enclosing fluid-filled cavities or cisternae, that coils and twists through the cytosol. The ER is continuous with the nuclear membrane and accounts for 1/2 of cell's membranes -Rough ER: is a ribosome-studded membrane system. Its cisternae act as sites for protein modification. Its external face acts in phospholipid synthesis. Vesicles pinched off from the ER transport the proteins to other sites -Smooth ER: synthesizes lipid and steroid molecules. It also acts in fat metabolism and in drug detoxification. In muscle cells, it is a calcium ion depot. |
|
|
Golgi apparatus: structure and function |
-consists of stacked and flattened membranous sacs, shaped like hollow dinner plates, associated with swarms of tiny membranous vesicles. -is the principal "traffic director" for cellular proteins -Its major function is to modify, concentrate, and package the proteins and lipids made at the rough ER -"receiving side" and "shipping side" |
|
|
Functions of lysosomes |
-lysosomes are spherical membranous organelles containing digestive enzymes. Function as a cell's "demolition crew" by digesting particles taken in by endocytosis, particularly ingested bacteria, viruses, and toxins; degrading worn out or nonfunctional organelles; performing metabolic functions, such as glycogen breakdown and release; breaking down nonuseful tissues, such as the webs between fingers and toes of developing fetus and uterine lining during menstruation; breaking down bone to release calcium ions into the blood -arise by budding off from golgi apparatus
|
|
|
Functions of peroxisomes |
-membranous sacs containing a variety of powerful enzymes, the most important of which are oxidases and catalses -oxidases use molecular oxygen to detoxify harmful substances, including alcohol. Their most important function is to neutralize dangerous free radicals by convertin ghtem to hydrogen peroxide, highly reactive chemicals with unpaired electrons that can scramble the structure of biological molecules **although peroxisomes look like small lysosomes, they are self-replicating organelles formed by a simply pinching in half of preexisting peroxisomes. Unlike lysosomes, they do not arise by budding from the golgi apparatus |
|
|
Name and describe the structure and function of cytoskeletal elements |
-cytoskeleton: elaborate series of rods running through the cytosol, supports cellular structures and provides the machinery to general various cell movements -microtubules: largest diameter, radiate from small region of cytoplasm near the nucleus called the centrosome, determine the overall shape of the cell as well as the distribution of cellular organelles; organelles are pulled along microtubules by tiny protein machines called motor proteins -microfilaments: thinnest element, involved in cell motility or changes in cell shape, help to form the cleavage furrow that pinches one cell into two during cell division -intermediate filaments: tough, insoluble protein fibers, constructed like woven ropes, the most table and permanent; they attach to desmosomes and their main job is to act as internal guy-wires to resist pulling forces exerted on the cell |
|
|
Describe the role of centrioles in mitosis and in formation of cilia and flagella |
Centrioles/the centrosome matrix is best known for its generation of microtubules and its role of organizing the mitotic spindle in cell division. Each centriole consists of a pinwheeel array of nine triplets of microtubules, arranged to form a hollow tube. Centrioles also form the bases of cilia and flagella |
|
|
Nuclear envelop: structure and function |
-double membrane structure; pierced by pores; outer membrane continuous with the endoplasmic reticulum -separates the nucleoplasm from the cytoplasm and regulates passage of substances to and from the nucleus |
|
|
Nucleolus: structure and function |
-dense spherical (non-membrane bounded) bodies; composed of ribosomal RNA and proteins -site of ribosome subunit manufacture
|
|
|
Chromatin: structure and function |
-granular, threadlike material composed of DNA and histone proteins -DNA constitutes the genes |
|
|
List the phases of the cell life cycle and describe the key events of each phase |
-Includes two main divisions, interphase and mitotic phase -Interphase is the period from cell formation to cell division. Subdivisions include: G1 phase when the cell is metabolically active, synthesizing proteins rapidly and growing vigorously; S phase is when DNA is replicated, new histones are made and assembled into chromatin; G2 phase is brief, enzymes and other proteins needed for division are synthesized and moved to their proper sites, centriole replication is completed |
|
|
Describe the process of DNA replication |
DNA replication occurs before cell division; it ensures that all daughter cells have identical genes. The DNA helix uncoils, and each DNA nucleotide strand acts as a template for the formation of a complementary strand. Base pairing provides the guide for the proper positioning of nucleotides -the products of the semiconservative replication of a DNA molecule are two DNA molecules identical to the parent molecule, each formed of one "old" an done "new" strand |
|
|
Describe cell division |
-cell division, essential for body growth and repair, occurs during the M phase. Cell division is stimulated by certain chemicals (including growth factors and some hormone) and increasing cell size. Lack of space and inhibitory chemicals deter cell division. Cell division is regulated by cyclin-CDK complexes, of which one example is MPF. Cell division consists of two distinct phases: mitosis and cytokinesis -Mitosis, consisting of prophase, metaphase, anaphase, and telophase, results in the parceling out of replicated chromosomes to two daughter nuclei, each genetically identical to the mother nucleus. Cytokinesis, which begins late in mitosis, divides the cytoplasmic mass into two parts |
|
|
Briefly describe phases of Mitosis |
-early prophase: chromatin threads condense to form chromosomes, nucleoli disappear, cytoskeleton microtubules disassemble, mitotic spindle forms -late prophase: nuclear envelope fragments, mitotic spindle lengthens, some spindles moving chromosomes toward center of cell and others pushing the cell apart -metaphase: chromosomes line up along metaphase plate -anaphase: centromeres of chromosomes split and each chromatid becomes a chromosome, split chromosomes are separated towards opposite poles -telophase and cytokinesis: both sets of chromosomes at opposite poles uncoil and resume chromatin form, nuclear envelop reforms, nucleoli reappear, mitotic spindle breaks down, contractile ring forms cleavage furrow and splits cell |
|
|
Define gene and genetic code and explain the function of genes |
-a gene is defined as a DNA segment that provides the instructions for the synthesis of one polypeptide chain. -the rules by which the base sequence of a gene is translated into an amino acid sequence are called the genetic code (ex: AAA = lysine) |
|
|
triplet vs. codon vs. anticodon |
-triplet: each three base sequence of exon DNA which provides the information for protein structure -codon: corresponding three base sequence of mRNA -anticodon: a three base sequence complementary to the mRNA codon calling for the amino acid carried by that particular tRNA **thus, the transfer of information goes from DNA base sequence (triplets) to the complementary base sequence of mRNA (codons) and then to the tRNA base sequence (anticodons) |
|
|
Ribosomal RNA vs. mRNA vs. tRNA |
-ribosomal RNA forms part of the protein synthesis sites -messanger RNA carries instructions for making a polypeptide chain from the DNA to the ribosomes -transfer RNA ferries amino acids to the ribosomes and recognizes codons on the mRNA strand specifying its amino acid |
|
|
Name two phases of protein synthesis |
Protein synthesis involves (1) transcription, synthesis of a complementary mRNA (RNA molecules are synthesized on single strands of the DNA template), and (2) translation, "reading" of the mRNA by tRNA and peptide bonding of the amino acids into the polypeptide chain. Ribosomes coordinate translation |
|
|
Describe the importance of ubiquitin degradation of soluble proteins |
-lysosomal enzymes do not have access to misfolded, damaged, or unneeded soluble proteins in the cytosol that need to be disposed of -to prevent such proteins from accumulating, doomed proteins are marked for attack by attachment of proteins called ubiquitins -the tagged proteins are hydrolyzed to small peptides by soluble enzymes or by giant "waste disposal" complexes composed of protein-digesting enzymes called proteasomes, and the ubiquitin is recycled |
|
|
Name and describe the composition of extracellular materials |
-Extracellular materials are any sustsances contributing to body mass that are found outside the cells, including... -body fluids: mainly interstitial fluid, blood plasma, and cerebrospinal fluid -cellular secretions: include substances that aid in digestion (intestinal and gastric fluids) and some that act as lubricants (saliva, mucus, and serous fluids) -the most abundant extracellular material is the extracellular matrix: a jellylike substance composed of proteins and polysaccharides. These molecules are secreted by the cells and self-assemble into an organized mesh in the extracellular space, where they serve as a universal "cell glue" that helps to hold body cells together |
|
|
Discuss some theories of cell differentiation and aging |
-the first cell of an organism is the fertilized egg. Early in development, cell specialization begins and reflects differential gene activation -the "wear and tear" theory attributes aging to little chemical insults and formation of free radicals, both of which have cumulative effects -"genetic theory" suggests that cessation of mitosis and cell aging are programmed into our genes; notion of a "telomere clock" determines the number of times a cell can divide
|
