Phys: Intro And Membrane Transport Flashcards
Physiology
The study of functions of living organisms
Two approaches to explain body functions:
-emphasis on purpose of body functions (meeting a bodily need)
-emphasis on mechanism (cause and effect sequences)
Levels of organization
-molecular/cellular
-tissue/organ
-organism/body system
Homeostasis
Maintenance of a relatively stable internal environment
**does not mean unchanging!!
Homeostasis is essential for ____________ and _____________ of all cells
Survival and function
Factors homeostatically regulated:
-[ ] of nutrient molecules
- [ ] of O2 and CO2
-[ ] of waste products
-pH
-[ ] of water, salt, and other electrolytes
-volume and pressure
-temperature
In order to maintain homeostasis, control system must be able to:
-detect deviation in the normal
-integrate this info with other relevant info
-make appropriate adjustments to restore
Two classes of control systems:
-intrinsic controls
-extrinsic controls
Intrinsic controls
Local controls that are inherent in an organ
Extrinsic controls
-regulatory mechanisms initiated outside an organ
-accomplished by nervous and endocrine systems
Feedforward
Term used for responses made in anticipation of a change
Feedback
-Responses made after change has been detected
-negative and positive systems
Negative feedback systems
-primary type of homeostatic control
-oppose initial change
-3 components: sensor, control center, effector
Sensor in negative feedback system
Monitors magnitude of a controlled variable
Control center in negative feedback system
Compares sensor’s input with a set point
Effector in negative feedback system
Makes a response to produce a desired effect
Positive feedback system
-amplifies initial change
-does NOT occur as often as negative feedback
-ex. Uterine contractions becoming stronger until baby is born
Disruptions in homeostasis can lead to:
-illness and death
-pathophysiology (abnormal functioning of the body associated with disease)
Hyperkalemia
Common clinical problem that is most often due to impaired urinary potassium excretion due to acute or chronic kidney disease or drugs that inhibit renin-angiotensin-aldosterone axis
Most serious problems associated with hyperkalemia:
-muscle weakness or paralysis
-cardiac conduction abnormalities
Fluid lipid bilayer is embedded with ________
-Proteins (mostly phospholipids: polar end hydrophilic, non-polar end hydrophobic)
Cell membrane is a…
Bilayer of phospholipids with proteins
Lipid bilayer has small amounts of ___________ on the outer surface and ______________ tucked between the phospholipid molecules
Carbohydrates, cholesterol
Cholesterol in the lipid bilayer contributes to ____________ and ______________ of the cell membrane
Fluidity and stability
Lipids on the cell membrane:
-barrier to water and water-soluble substances
-organized in a bilayer of phospholipid molecules
What can diffuse across the cell membrane?
-small, non-polar solutes can diffuse across (O2, CO2, ethanol, steroid hormones)
Proteins within the cell membrane:
-provide specificity to the membrane
-defined by the mode of association with lipids (integral and peripheral)
Integral membrane proteins
Channels, pores, carriers, and enzymes embedded within the membrane
Peripheral membrane proteins
Enzymes and signal mediators only associated with the outer layer of the membrane
Unassisted membrane transports:
-diffusion
-osmosis
Assisted membrane transports:
-carrier-mediated transport
-facilitated transport
-active transport
Diffusion characteristics:
-occurs down a concentration gradient (higher to lower [ ] )
-through lipid bilayer by channel or carrier
-no additional energy required
Active transport characteristics:
-occurs against a concentration gradient
-involves a protein carrier
-requires energy (ATP)
Sometimes, transport through a channel protein can be referred to as __________________ instead of simple diffusion
Facilitated diffusion
Channel proteins:
-aquaporins
-aquaglyceroporins
-ion channels
Simple diffusion with lipid-soluble molecules
Move readily across cell membranes (rate depends on lipid solubility)
Simple diffusion with water-soluble molecules
Cross cell membranes via channels or other transport proteins
Characteristic of carrier-mediated transport are:
Saturation, stereospecificity, and competition
Rate of diffusion is limited by ______of carrier protein
-Vmax (units are pmol/min/mg protein
**adding more carriers does NOT affect Vmax
When a protein carrier is saturated, the rate of transport is __________
Maximal
Saturation occurs when…
The [ ] of a solute is > than the number of available transporters can handle
Movement against a concentration gradient requires…
An additional source of energy besides kinetic energy
Primary active transport
Molecules are pumped against an electrochemical gradient at the expense of ATP
**direct use of energy
Secondary active transport
Transport driven by the energy stored in the electrochemical gradient of another molecule (usually Na+)
**indirect use of energy
Na+-K+ ATPase characteristics:
-located in the plasma membrane of all animal cells
-pumps Na ions out of cells and pumps K into cells against electrochemical gradient
-critical role in regulating osmotic balance
Sodium/ potassium pump is activated by..
An increase in cell volume
Sodium/potassium pimp requires about _____ of typical cell’s energy and up to ___ of neuron’s energy
1/5 , 2/3
Inhibition of sodium/potassium pump by ________ causes cell to…
Ouabain, swell and burst
What activates the ATPase in the sodium/potassium pump?
-When 2K+ bind on outside of carrier protein and 3Na+ bind in th inside
-*this causes cleavage of one Pi (ATP to ADP)
The cleaved phosphate then sodium and potassium bind causes…
A chemical and conformational change in the protein carrier molecule releasing the 3 Na to the outside and 2 K to the inside
The Na/K transport is ___________
Electrogenic
The electrogenic nature of the pump contributes less than ____ to the membrane potential
10%
Ca2+ ATPase is located on the….
cell membrane and the sarcoplasmic reticulum in muscle fibers
SERCA
Name for the sarcoplasmic and endolpasmic reticulum Ca2+ATPase
Ca2+ ATPase maintains a __________ Ca2+ concentration
Low cytosolic
H+ ATPase is found in…
Parietal cells of gastric glands (HCl secretions) and intercalated cells of renal tubules (controls blood pH)
H+ ATPase concentrates H+ ions up to ____________
1 million-fold
Protein co-transporters in secondary active trasnport:
Symporters and antiporters
Symporters
Transport substance in same direction as a “driver” ion
Antiporters
Transport substance in opposite direction of a “driver” ion
