Lecture 1 Flashcards
what are the components of Feedback Lopp
receptors: monitors a controlled condition
control center: determines next action
effector: receives directions from control center; produces a response that changes the controlled condition
what is NEGATIVE FEEDBACK LOOP?
- original stimulus reversed
- most feedback systems in the body are negative
- used for conditions that need frequent adjustment
- body temperature, blood sugar levels, blood pressure
what is POSITIVE FEEDBACK LOOP?
- original stimulus intensified
- seen during normal childbirth
explain the Homeostasis of Blood Pressure
- pressure receptors in walls of certain arteries detect an increase in BP (BP = force of blood on walls of vessels)
- brain receives input and signals heart and blood vessels
- heart rate slows and arterioles dilate (increase in diameter)
- BP returns to normal
explain positive feedback during childbirth
- stretch receptors in walls of uterus send signals to brain
- brain releases hormone (oxytocin) into bloodstream
- uterine smooth muscle contracts more forcefully
- more stretch, more hormone, more contraction, etc.
- cycle ends with birth of the baby & decrease in stretch
what is epidemiology?
how disease is transmitted
what is cytology?
study of cellular structure
what is cell physiology
study of cellular function
what are the 3 types of lipid molecules in cell membrane?
phospholipids
glycolipids
cholesterol
what are the characteristics of phospholipids?
- comprise of 75% of lipids
- phosholipid bilayer = 2 parallel layers of molecules
- each molecule is amphipathic (has both polar & nonpolar region)
polar parts of phospholipids are?
- the head
- hydrophilic and face on both surfaces a watery environment
non-polar parts of phospholipids are?
- tails
- hydrophobic and line up next to each other in the interior
what are the characteristics of glycolipids with the cell membrane?
- comprise 5% of lipids of he cell membrane
- carbohydrate groups form a polar head only on the side of the membrane facing the extracellular fluid
what are the characteristics of cholesterol within the cell?
- comprise of 20% of cell membrane lipids
- interspersed among the other lipids in both layers
- stiff steroid rings & hydrocarbon tail are non-polar
what are Integral Proteins?
- extend into or completely across cell membrane
- all are amphipathic with hydrophobic portion hiding among the phospholipid tails
- glycoproteins have the sugar portion facing the extracellular fluid to form a glycocalyx
what are Peripheral Proteins?
- attached to either inner or outer surface of cell membrane and are easily removed from it
what are the functions of membrane proteins?
- formation of Channel : allows specific substance to pass through
- transporter Proteins: bind a specific substance, change their shape and move it across membrane
- Receptor Proteins: cellular recognition site
- cell identity marker: allow cell to recognize other similar cells
- linker: anchor proteins in cell membrane or to other cells; allow cell movt; cell shape & structure
- act as enzyme: speed up reaction
what decreases the fluidity of a membrane?
fluidity is reduced by presence of cholesterol, bc cholesterol increases stiffness of membrane, since it forms a hydrogen bonds with neighboring phospholipid heads
lipid bilayers have selective permeability, they are permeable to?
- non-polar and uncharged molecules (such as oxygen, sterioids, CO2)
- to water, which flows through the gaps that form in hydrophobic cores of membranes as phospholipids move about
In selective permeability of membrane, the transmembrane protein act as…?
specific channels to small & medium, polar and charged molecules
macromolecules are unable to pass through the membrane bc of their large size, what do they do?
they are passed through via vesticular transport
what is concentration gradient?
membrane can maintain difference in concentration of substance inside versus outside of membrane
- more O2 & Na+ outside of cell membrane
- more CO2 & K+ inside of cell membrane
what is electrical gradient of membrane potential?
membrane can maintain a difference in charged ions between inside and outside of membrane
gradients across the plasma membrane means?
substances move down their concentration gradient and towards the oppositely charged area
- ions have electrochemical gradients
what is mediated transport?
moves materials with the help of a transporter protein
what is nonmediated transport?
does not use a transporter protein
what is active transport?
uses ATP to drive substances against their concentration gradient
what is passive transport?
moves substances down their concentration gradient with only their kinetic energy
what is vesicular transport?
moves materials across membranes in small vesicles- either by exocytosis or endocytosis
what is the principle of diffusion
random mixing of particles in a solution as a result of the particle’s kinetic energy
what happens in diffusion
more molecules move away from an area of high concentration to an area of low concentration
what creates a faster rate of diffusion
- the greater the difference in concentration between the 2 sides of membrane
- higher temperature
- increase in surface area
what creates slow rate of diffusion?
- larger the size of diffusing substance, the slower the rate of diffusion
- increasing diffusion distance
when is equilibrium achieved in diffusion?
when molecules are evenly distributed
what is osmosis
the net movt of water through a selectively permeable membrane from an area of high water concentration to an area of lower water concentration
what are examples of osmosis?
diffusion through lipid bilayer
aquaporins (transmembrane proteins) that function as water channels
when does osmosis ONLY occur?
only if membrane is permeable to water but not to certain solutes
what are the effects of fluids on RBCs in lab?
- water enters the cell faster than it leaves
- water enters & leaves the cell in equal amounts
- water leaves the cell
normally the osmotic pressure of the inside of the cell is…
equal to the fluid outside of the cell
-cell volume remains constant (solution is isotonic)
what is isotonic solution?
water concentration is the same inside and outside of cell, which results in no net movt of water across cell membrane
what is hypotonic solution?
higher concentration of water outside of cell results in hemolysis (rupture of blood cell)
whiat is hypertonic solution?
lower concentration of water outside of cell causes crenation (scalloped edge)
what diffuses through the lipid bilayer and why is this important?
- important for absorption of nutrients - excretion of wastes
- nonpolar, hydrophobic molecules
what is diffusion through membrane channels?
- each membrane channel specific for particular ion (K+, CI-, Na+, or Ca+2)
- slower than diffusion through membrane but still 1 million K+ through a channel in one sec
- channels may be open all the time or gated (closed randomly or as ordered)
what is facilitated diffusion?
- substance binds to specific transporter protein
- transporter protein conformational change move substance across cell membrane
- facilitated diffusion occurs down concentration gradient only
- rate of movt depends upon steepness of concentration gradient, number of transporter proteins
describe the facilitated diffusion of glucose
- glucose bindsto transport protein
- transport protein changes shape
- glucose moves across cell membrane (but only down the concentration gradient)
- Kinase enzyme reduces glucose concentration inside the cell by transforming glucose into glucose-6-phosphate
- transporter proteins always bring glucose into cell
what is active transport?
- movt of polar or charged substances against their concentration gradient
- energy-requiring process: energy from hydrolysis of ATP (primary active transport); energy stores in an ionic concentration gradient (2ndary active transport)
- exhibits transport maximums and saturation
- Na+, K+, H+, Ca+2, I- and Cl-, amino acids and monosaccharides
what is primary active transport?
- transporter protein called a pump, it works against concentration gradient, requires 40% of cellular ATP
- Na+/K+ ATPase pump (maintains low concentration of Na+ and high concentration of K+ in the cytosol; operates continually)
- maintenance of osmotic pressure across membrane - cells neither shrink nor swell due to osmosis & osmotic pressure; sodium continually pumped out as if sodium could not enter the cell (factor in osmotic pressure of extracellular fluid); K+ inside the cell contribute to osmotic pressure of cytosol
what is secondary active transport
- uses energy stored in an ion concentration gradient to move other substances against their own concentration gradient
- Na+/K+ pump maintains low concentration of Na+ inside of cells
- provides route for Na+ to leak back in and use energy of motion to transport other substances
- Na+ symporter proteins: glucose or amino acids rush inward with Na+ ions
- Na+ antiporters protein: as Na+ ions rush inward, Ca+2 or H+ pushed out
what is endocytosis?
bringing something into cell
what is phagocytosis
cell eating by macrophages & WBCs - particles binds to receptor proteins -whole bacterial or viruses are engulfed and later digested -pseudopods extend to form phagosome lysosome joins it
what is pinocytosis?
cell drinking
no receptor proteins
no pseudopods form
nonselective drinking of extracellular fluid
what is receptor-mediated endocytosis?
selective input
- mechanism for uptake of specific substances - ligands
- desired substance binds to receptor protein in clathrin-cpated pit region of cell membrane causing membrane to fold inward
- vesicles become uncoated and combine with endosome
- receptor proteins separate from ligands and return to surface
- ligans are digested by lysosomal enzyme or transporter across cell - epithelial cell crossing accomplished
what is exocytosis?
release something from cell
- vesicles form inside cell, fuse to cell membrane
- release their contents: digestive enzymes, hormones, neurotransmitters, or waste products
- replace cell membrane lost by endocytosis
