Phys: Intro And Membrane Transport Flashcards by Bella Forster

Physiology

The study of functions of living organisms

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Two approaches to explain body functions:

-emphasis on purpose of body functions (meeting a bodily need)
-emphasis on mechanism (cause and effect sequences)

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Levels of organization

-molecular/cellular
-tissue/organ
-organism/body system

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Homeostasis

Maintenance of a relatively stable internal environment
**does not mean unchanging!!

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Homeostasis is essential for ____________ and _____________ of all cells

Survival and function

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Factors homeostatically regulated:

-[ ] of nutrient molecules
- [ ] of O2 and CO2
-[ ] of waste products
-pH
-[ ] of water, salt, and other electrolytes
-volume and pressure
-temperature

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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

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Two classes of control systems:

-intrinsic controls
-extrinsic controls

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Intrinsic controls

Local controls that are inherent in an organ

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Extrinsic controls

-regulatory mechanisms initiated outside an organ
-accomplished by nervous and endocrine systems

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Feedforward

Term used for responses made in anticipation of a change

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Feedback

-Responses made after change has been detected
-negative and positive systems

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Negative feedback systems

-primary type of homeostatic control
-oppose initial change
-3 components: sensor, control center, effector

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Sensor in negative feedback system

Monitors magnitude of a controlled variable

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Control center in negative feedback system

Compares sensor’s input with a set point

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Effector in negative feedback system

Makes a response to produce a desired effect

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Positive feedback system

-amplifies initial change
-does NOT occur as often as negative feedback
-ex. Uterine contractions becoming stronger until baby is born

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Disruptions in homeostasis can lead to:

-illness and death
-pathophysiology (abnormal functioning of the body associated with disease)

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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

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Most serious problems associated with hyperkalemia:

-muscle weakness or paralysis
-cardiac conduction abnormalities

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Fluid lipid bilayer is embedded with ________

-Proteins (mostly phospholipids: polar end hydrophilic, non-polar end hydrophobic)

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Cell membrane is a…

Bilayer of phospholipids with proteins

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Lipid bilayer has small amounts of ___________ on the outer surface and ______________ tucked between the phospholipid molecules

Carbohydrates, cholesterol

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Cholesterol in the lipid bilayer contributes to ____________ and ______________ of the cell membrane

Fluidity and stability

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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