1 obj331 cellbiol

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  • 1. Cell Biology-viv1.Identify the five chief cellular functions. a. Movement: muscle cells-attached to bones to produce limb movements b. Conductivity: nerve cells-response to a stimulus by a wave of excitation, an electrical potential, that passes along the surface of the cell to reach its other parts c. Metabolic absorption: All cells take in and use nutrients. For example, cells of the intestine and the kidney are specialized to carry out absorption. Cells of the kidney tubules reabsorb fluids and synthesize proteins. Intestinal epithelial cells reabsorb fluids and synthesize protein enzymes d. Secretion: mucous gland cells can synthesize new substances from substances they absorb and then secrete the new substances to serve as needed elsewhere. Cells of adrenal gland, testis, ovary can secrete hormonal steroids e. Excretion: all cells can get rid themselves of waste products resulting from metabolic breakdown of nutrients f. Respiration: cells absorb oxygen which is used to transform nutrients into energy (ATP)-Mitochondria g. Reproduction: tissue growth occurs as cells enlarge and reproduce themselves. Not all cells are capable of continuous division, and nerve cells cannot reproduce. h. Communication: Constant communication allows the maintenance of a dynamic steady state. Pancreatic cells secrete and release insulin to tell muscle cells to take up sugar from the blood for energy.2.Match the cellular function to the cell type that performs that function.The five cell types and the five chief cellular functions are: 1. Nerve Cells – Detect changes in internal or external environment. They transmit nerve impulses from one part of the body to another. 2. Muscle Cells – Contract to allow movement of body parts. 3. Red Blood Cells – Transport Oxygen in the bloodstream (from the lungs to other body parts of the body). 4. Gland Cells – Release substances such as hormones, enzymes, mucus and sweat. 5. Immune Cells – Recognize and destroy “non-self” cells such as cancer cells and invading bacteria.3. Identify the three components of a typical eukaryotic cell.Eukaryotic cells - Organization, memb-bound organelles, central nubleus.have a truenucleus bound by a double membrane that contains the genetic information needed fortranscription, translation and production of proteins. Eukaryotic cells have membranebound organelles such as the endoplasmic reticulum, mitochondria, golgi apparatus, and Page 1 of 8
  • 2. lysosomes. Eukaryotic cells have ribosomes, which can be free in the cell cytoplasm orcan be bound to the endoplasmic reticulum, which in turn makes it a rough endoplasmicreticulum. Ribosomes are involved in the translation of mRNA to produce proteins thatare inscribed in the genetic code of the mRNA.4. Describe the structure and functions of the nucleus.The nucleus is a membrane-enclosed organelle found in eukaryotic cells. It contains mostof the cellular genetic material, which is organized into long multiple linear DNAmolecules. The DNA molecules form complexes with a large variety of proteins, such ashistones, to form chromosomes, which make up the nuclear genome. The function of thenucleus is to act as the control center and regulatory component of the cell bymaintaining the integrity of the chromosomes and by controlling the activity of the cellby regulation of the genes expressed.5. Describe the structure and functions of ribosomes.Ribosomes are complexes of RNA and protein that are found within the cell. Ribosomesare composed of two subunits a small subunit and a large subunit. The function ofribosomes is to aid in the translation of mRNA and the production of proteins bycatalyzing the assembly of individual amino acids into polypeptide chains, which arelater folded properly and become functioning proteins within the cell.6.Compare and contrast smooth and rough endoplasmic reticulum in terms ofstructure and function.The smooth endoplasmic reticulum is a network that consists of tubules and vesiclesthat branch out within the cell and forms the golgi apparatus. The rough endoplasmicreticulum has ribosomes attached to it but shares the same common characteristics withthe smooth endoplasmic reticulum and is thought to be continuous with the nuclearmembrane. When the attached ribosomes make a protein they deposit it into the lumen ofthe rough endoplasmic reticulum. The protein can then be processed in the lumen area orit can be transported in the lumen space to other parts of the cell. The endoplasmicreticulum has the ability to assemble the lipids needed in making membranes and is also apart of certain types of reactions such as protein processing, lipid formation, membraneformation and detoxifying reactions.7. Describe the structure and function of the golgi apparatus.The golgi apparatus is an organelle of small sacs stacked on one another near thenucleus that makes carbohydrate compounds, combines them with protein molecules, andpackages the product for distribution from the cell.8. Describe the structure and function of the lysosome. Page 2 of 8
  • 3. The lysosome is a membranous organelle that pinched off from the golgi apparatuscontaining various enzymes that can dissolve most cellular compounds and un-neededmacromolecule into basic reusable compounds such as proteins that are not needed intoamino acids which can then be reused by the cell; called digestive bags or suicide bags ofcell.9. Identify the contents of lysosomes and explain their normal functions (McCancepg.6): a. Contains more than 40 digestive enzymes called hydrolases, which catalyse bonds in proteins, lipids, nucleic acids and carbohydrates. b. Function: Lysosomal enzymes are capable of digesting most cellular constituents down to their basic forms such as amino acids, fatty acids, and sugars. The decreased pH value of a lysosome assist in the digestive processes of other cell’s. They are “cellular garbage disposals.10.Describe the structure and function of the mitochondira (McCance pg. 8): a. Structure: Mitochondria appear as rods (“sausage shaped”) that are bound by a double membrane. The outer membrane is smooth and surrounds the mitochondrion itself; the inner membrane is convoluted in the mitochondrial matrix to form cristae. The inner membrane contains the enzymes of the respiratory chain. The outer membrane is permeable to many substances, but the inner membrane is highly selective and contains many transmembranous transport system b. Function: Cellular respiration. It regulates cellular metabolism and provides 95% of a cell’s energy supply. The mitochondria’s enzymes catalyze oxidative reactions. Power house of the cell, energy formation with the production of ATP. ATP: energy currency of cell formed by oxidative phosphorlyation. It has a DNA molecule, which allows it to produce its own enzymes and replicate copies of itself.11. Predict how mitochondrial dysfunction can lead result in cell injury and disease: a. The mitochondria supply our cells with energy through the production of ATP. If the mitochondria are not functioning properly then the cells start Page 3 of 8
  • 4. breaking themselves down to find energy. Glycolysis and lactic acid only supply us with a small amount of energy so eventually mitochondrial dysfunction will cause the cells to self destruct by autophagocytosis. Dysfunction will lead to cell ischemia, injury or death. Dysfunction may play a role in things like mental disorders and cardiac dysfunctions.12. Match the five plasma membrane functions with the underlying purpose or activity (McCance pg 9-10):Five plasma membrane functions a. Structure: usually thicker than intercellular organelle membranes. Containment of cellular organelles. Maintenance of relationship with cytoskeleton, ER, and other organelles. The outer surface in many cells are not smooth but are studded with cilia or even smaller cylindrical projections called microvilli; both are capable of movement; caveolae are also outer indentations. Maintenance of fluid and electrolyte balance. b. Protection: Barrier to toxic molecules and macromolecules (protein, nucleic acid, polysaccharides). Barrier to foreign organisms and cells. c. Activation of Cell: Hormones (regulates cellular activity), Mitogens (cellular division), Antigens (antibody synthesis), and Growth factors (proliferation and differentiation). d. Transport: Diffusion and exchange diffusion, Endocytosis (pinocytosis and phagocytosis); receptor-mediated endocytosis, exocytosis (secretion), and active transport. e. Cell to Cell Interaction: Communication and attachment at junctional complexes, symbiotic nutritive relationships, release of enzymes and antibodies to extracellular environment, and relationship with exracellular matrix.13.Explain the anatomical basis for the plasma membrane’s ability to act as abarrier to water soluble molecule while allowing lipid soluble molecules easy access: a. The plasma membrane is a phospholipids bilayer arranged with their nonpolar tails pointing toward each other. The membrane spontaneously organizes itself into a bilayer because these two incompatible solubilities. Page 4 of 8
  • 5. The hydrophobic region (tail) of each lipid molecule is protected from water, whereas the hydrophilic region (head) is immersed in it. The bilayer’s structure accounts for one of the essential functions of the plasma membrane: it is impermeable to most water soluble molecules because they are insoluble in the oily core region. The bilayer serves as a barrier to the diffusion of water and hydrophilic substances while allowing lipid- soluble molecules (O, CO2), to diffuse through. b. The anatomical basis of the membrane is so that it can have selective impermeability.14.Identify four functions of plasma membrane proteins (McCance pg 12): a. Proteins facilitate transport across membranes by serving as receptors, enzymes, or transporters. Proteins act as: i) Transporters other molecules into and out of the cell ii) Facilitates (catalyzes) membrane reactions iii) Receives messages, thus acting as receptors for extracellular and intracellular signals. iv) Create structural linkages between the external and internal cellular environments.15.Explain the role of cell receptors in normal cell function (McCance 14-15): a. Receptors are protein molecules on the plasma membrane, in the cytoplasm, or in the nucleus that are capable of recognizing and binding with specific smaller molecules called ligands. I.e.: Hormones are ligands. b. Recognition and binding depend on the chemical configuration of the receptor and its smaller ligand, which must fit together like jigsaw puzzle. c. Plasma membrane receptors: bind with hormones, neurotransmitters, antigens, infectious agents, drugs, and metabolites.16.Compare and contrast endocytosis, pinocytosis, passive transport, activetransport, osmosis, diffusion, and facilitated diffusion: a. Endocytosis and pinocytosis: involves the ingestion of fluids and solute molecules through formation of small vesicles (McCance pg 30). b. Passive transport or facilitated diffusion: the protein transporter moves solute molecules through cellular membranes without expending metabolic energy via simple diffusion (down the gradient concentration) (McCance pg 25). Page 5 of 8
  • 6. c. Active transport: the protein transporter moves molecules against, or up the concentration gradient and required expenditure of energy (ATP) (McCance pg. 25). d. Osmosis: the movement of water down a concentration gradient across a semipermeable membrane from a region of higher water concentration to a lower concentration. The membrane must be more permeable to water than to solutes and the concentration of solutes must be greater so that water moves more easily (McCance pg. 26). e. Diffusion: the movement of a solute molecule from an area of greater solute concentration to an area of lesser solute concentration. The difference in concentration is known as a concentration gradient. The higher concentration on one side, the greater the diffusion rate. (McCance 25).17. Describe the Fluid Mosaic Model: i. Transport other molecules into and out of the cell j. Facilitate membrane reactions k. Receive messages, thus acting as receptors for extracellular and intracellular signals l. Create structural linkages between external and internal cellular environment. m. It accounts for the flexibility of cellular membranes, their self-sealing properties, and their impermeability to many substances18. Define the term membrane potential and explain how the membrane potential isgenerated: a. Membrane potential: slight excess of positively charged ions on the outside of the membrane and slight deficiency of positively charged ions on the inside of the membrane. b. When a membrane potential is maintained by a cell, opposite ions are held on opposite sides of the membrane like water behind a dam-ready to rush through with force when the proper membrane channels open. c. Types of membrane potentials: i. Resting membrane potential: polarized at -70mV ii. Local potential: depolarized (excitatory) at higher than -70mV and hyperpolarized (inhibitory) at lower than -70mV Page 6 of 8
  • 7. iii. Threshold potential: depolarized at -59mV iv. Action potential: depolarized at +30mV19 Describe the role of ATP in cellular metabolism: a. The energy transferred by ATP is used in doing he body’s work-the work of muscle contraction and movement, of active transport, and biosynthesis. b. Because ATP is the form of energy that cells generally use, it is an especially important organic molecule. ATP is a mole that can pick up energy and give it to another chemical process; therefore, it is often called the energy currency of cells.20. Define oxidative phosphorlyation and describe its role in cellular metabolism: a. Oxidative phosphorlyation: refer to this oxygen-requiring joining of a phosphate group to ADP to form ATP. b. Glycolytic enzymes in the cytoplasm catalyze the production of pyruvic acid, which diffuses into mitochondria. The enzymes of this critic acid cycle have been localized mostly to the matter (matrix) inside the inner mitochondrial membrane. The high-energy electrons and their accompanying protons are then carried to the cristae of the inner membrane, where the electron transport carriers and mechanism for phosphorylation is found. Because so many of the cell’s energy releasing enzymes are located within the mitochrondria, these tiny structures are aptly the power plants of the cell.21. Predict the effect of an ATP deficit on membrane potentials and actionpotentials: a. Both membrane potentials and action potentials require ATP to conduct impulse. If ATP is deficit, generating impulse will be very difficult.22. ID three major mechanisms of cell-cell (intracellular) communication: a. They form protein channels (gap junction) that directly coordinate the activities of adjacent cells Page 7 of 8
  • 8. b. They display plasma membrane-bound signaling molecules (receptors) that affect the cell itself and other cells in direct physical contact c. They secrete chemicals that signal to cells some distance away23. Differentiate between desmosomes, tight functions, and gap junctions: a. Desmosomes: holds cell together by forming either continuous bands or belts of epithelial sheets or button-like points of contact and maintain structural stability. b. Tight junction: serve as a barrier to diffusion, prevent the movement of substances through transport proteins in the plasma membrane, and prevent leakage of small molecules between the plasma membranes of adjacent cells c. Gap junctions: clusters of communicating tunnels, connexons, that allow small ions and molecules to pass directly from the inside of one cell to the inside of another.. It coordinates the activities of adjacent cell. Important for synchronizing contractions of heart muscle cells through ionic coupling and in permitting action potentials to spread rapidly from cell to cell neural tissues.24. Match the type of intercellular junction to the function of cell. See #23 Page 8 of 8