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BIO169 - Obj Week 1
BIO169 - Objectives Week 1
| Question | Answer |
|---|---|
| Homeostasis: definition | the ability of the body to maintain a consistent internal environment while being exposed to continuously changing conditions |
| Homeostasis: examples | see negative & positive feedback examples |
| Negative feedback: definition | a control mechanism in which a change in variable in one direction (increase or decrease) will initiate responses which will promote change in that variable back to normal; the most common control mechanism |
| Negative feedback: examples | blood glucose is maintained at approximately 100 mg/100 ml of blood; an increase in blood glucose which occurs after a meal triggers the release of insulin from the pancreas; insulin triggers the uptake of glucose from the blood into cells thus bringing t |
| Negative feedback: examples | maintenance of body temperature; when body gets too hot, blood vessels dilate and boyd produces sweat to cool off; when body gets too cold, blood vessels become constricted and body shivers to raise temp |
| Positive feedback: definition | a control mechanism in which the initiating change in a variable triggers responses which promote further change in the variable |
| Positive feedback: examples | labor & delivery; pressure, irritation, & stretch of uterine wall & cervix cause release of oxytocin; oxytocin causes uterine contractions, pushes baby into cervix creating more irritation, pressure and distension, resulting in release of more oxytocin... |
| Describe the fluid mosaic model of the cell membrane | The basic structure of the membrane is a double layer of lipids with various proteins embedded in it |
| Describe the 3 main types of molecules and their percentage by weight: | The membrane is composed of 3 main types of molecules; on a weight basis it is composed of: 35% lipid, 62% protein, 3% carbohydrate. |
| Describe the orientation of the phospholipids | The lipid molecules are phospholipids w/ polar heads & nonpolar tails. The polar (hydrophilic) heads face the inner and outer membrane surfaces for free interaction with water. The nonpolar (hydrophobic) tails face inward forming a waterproof barrier. |
| Explain functions of the cell membrane (4) | 1)boundary between the cell’s internal and external environments 2)regulates the transport of substances in & out of the cell 3)contains receptors which determine how a cell will respond to environmental stimuli 4)contains antigens for immune response |
| What are glycolipids and glyclolipids? | they are carbohydrate "tails" attached to phospholipid and protein molecules., which function in cell adherence and as antigens. Glyclolipid=carb+phospholipid; glycoprotein=card+protein |
| What is simple diffusion? | the net movement of molecules from an area of high concentration to low concentration |
| What energy is used in diffusion? | random kinetic energy |
| What types of molecules pass by simple diffusion | factors are solubility, molecular size, and molecular charge; molecules will pass if they are: 1) lipid soluble 2) water soluble and small enough, if they are electrically neutral (water soluble charged particles will pass only with difficulty) |
| What is facilitated diffusion? | used to transport a solute from higher to lower concentration; solutes move across a membrane by means of a transporter until the two concentrations become equal; metabolic energy is not required |
| What is an example of a molecule that is transported by facilitated diffusion? | glucose |
| What is osmosis? | the diffusion of water molecules across a semi-permeable membrane; since it is a special case of diffusion, all factors that affect diffusion rate also affect the rate at which osmosis can occur |
| What is filtration? | the net movement of fluid and/or solutes out of capillaries due to the hydrostatic pressure of the blood |
| What is carrier mediated active transport | active transport moves molecules against an electrochemical gradient; 1) solutes move across a membrane by means of a transporter; 2) energy input is required |
| What is another name for an active transport transporter? | a pump |
| What is phagocytosis? | a form of endocytosis; "cell eating"; cells engulf large particles, such as bacteria and debris from damaged tissues and pinches off to form a vesicle |
| What is pinocytosis? | a form of endocytosis; "cell drinking"; the cell membrane engulfs extracellular liquid, pinching it into the cell to form a vesicle |
| What is exocytosis? | a process in which an intracellular vesicle fuses with the plasma membrane, the vesicle opens, and its contents are liberated into the extracellular fluid |
| What are the variables which affect diffusion rate? (10) | permeability, molecular size, pore size, charge, concentration gradient, surface area, temperature, solubility, molecular weight, and distance |
| What is the effect of permeability on diffusion? | the greater the permeability constant, the larger the net flux across the membrane for any given concentration difference and membrane surface area |
| What is the effect of molecular size on diffusion? | if small enough, a water soluble substance may be able to diffuse through the pores or channels in transmembranal proteins; if too large, they can't pass by simple diffusion |
| What is the effect of pore size on diffusion? | the large the pores, the easier it is for solutes to past through |
| What is the effect of molecular charge on diffusion? | the pores behave as if they are lined with positive charges, so a positively charged substance will pass only with difficulty; negatively charged ones also diffuse with difficulty, while netral ones should be able to freely pass through |
| What is the effect of the concentration gradient on diffusion? | the bigger the gradient, the faster diffusion occurs |
| What is the effect of surface area on diffusion? | the greater the amount of available surface area of cell membrane, the faster diffusion occurs |
| What is the effect of temperature on diffusion? | the higher the temperature, the faster the diffusion rate |
| What is the effect of solubility on diffusion? | the more lipid soluble the molecule, the faster the diffusion rate |
| What is the effect of molecular weight on diffusion? | the greater the molecular weight, the slower the diffusion rate |
| What is the effect of distance on diffusion? | the greater the distance between the areas of high and low concentration, the slower the rate |
| Define osmotic pressure and explain how it is measured | the pressure exerted against a membrane due to diffusion of water; measured by determining the hydrostatic pressure needed to stop osmosis |
| What determines osmotic pressure? | the osmolarity; the higher the osmolarity, the higher the osmotic pressure and the more water will flow in (i.e. water flows towards higher osmotic pressure |
| What is osmolarity? | a measurement of the number of solute particles within a solution; calculates as molarity * number of solute particles formed by solute molecule (i.e. in the case of dissociation of ions) |
| What is tonicity? | the relative concentration of solute to a particular cell (typically a red blood cell) |
| What is isotonic? | the concentration of solute on both sides of a membrane are the same; no transfer of water |
| What is hypertonic? | the concentration of solute is greater than the concentration of solute in the cell; the cell will lose water to solution (crenation) |
| What is hypotonic? | the concentration of solute is less than the concentration of solute in the cell; the cell will gain water from the solution, which may cause the cell to burst (lysis, or in a red blood cell - hemolysis) |
| What is the function of the nucleus? | stores, transmits, and expresses genetic information which is coded in molecules of DNA |
| What is the function of the nucleolus? | it is where ribosomal subunits are assembled; it is a filamentous region without a membrane |
| What is the function of chromatin? | it is the nuclear material that contains the genetic code; it is composed of DNA and proteins; during cell division the chromatin condenses into chromosomes |
| What is the function of the mitochondria? | they are the major cell sites that comsume oxygen and produce carbon dioxide in chemical processes that transfer energy to ATP, which can then provide energy for cell functions; they also synthesize certain lipids |
| What is the function of the smooth endoplasmic reticulum? | it is the site of lipid synthesis and calcium accumulation and release; it is tubular and lacks chromosomes |
| What is the function of the Golgi apparatus? | it modifies and sorts the proteins that are synthesized on the RER and packages them into secretory vesicles |
| What is the function of a ribosome? | it is composed of RNA and protein and it is the site of protein synthesis |
| How is protein synthesized in a ribosome? | it is synthesized using genetic info from messenger RNA |
| What happens to the proteins synthesized on free ribosomes? | it is released into the cytosol |
| What happends to protein synthesized on the RER? | it passes into the lumen of the reticulum and is then transferred to the Golgi apparatus of modification and secretion from the cell, or to other organelles |
| What is the function of a lysosome? | it digests particulate matter that enters the cell |
| What is the function of a peroxisome? | it uses oxygen to remove hydrogen from organic molecules and in the process forms hydrogen peroxide (H2O2) |
| What is the function of a centrosome? | it is a region of cell cytoplasm in which microtubule formation and elongation occur, particularly during cell division |
| What is a vesicle? | it is a small, membrane-bound organelle within cells; vesicles are formed during endocytosis and exocytosis to bring in some molecules (bacteria & debris) and to eliminate some wastes |
| What is the function of microtubules and microfilaments? | they are contained within the cytoplasm and they form a network providing for cell shape and movement |
| What is the function of cilia? | they are hairlike projections from specialized epithelial cells that sweep back and forth in a synchronized way to propel material along the epithelial surface |
| What is the function of a flagellum? | it is a long, threadlike appendage, used for locomotion; made up of microtubules |
Created by:
debmurph