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UNL / Management / MNGT 213 / What is the meaning of osmolality in biology?

What is the meaning of osmolality in biology?

What is the meaning of osmolality in biology?

Description

School: University of Nebraska Lincoln
Department: Management
Course: Human Physiology
Professor: Tony zera
Term: Spring 2017
Tags: Human, Physiology, Topic1, and Topic2
Cost: 25
Name: BIOS 213 -- Week 2 Lecture Notes
Description: Topic #1: Biological Membranes and & introduction to ... Topic #2: Renal System
Uploaded: 01/22/2017
8 Pages 42 Views 2 Unlocks
Reviews


*words highlighted in red are fill-in-the-blank answers


What is the meaning of osmolality in biology?



~January 18th, 2017

❖ Terms

Review measures of concentration and ion dissociation

★ Osmolality - total moles of all solutes per liter of solvent

--ex: 1 mole glucose/Liters water = 1 Osm;

 1 mole NaCl/Liter water = 2 Osm - because NaCl dissociates into 2 ions (NaCl → Na+ Cl-) ★ Osmolality of blood = 0.3 Osm = 0.3 moles/Liter = 300 mOsm (know this unit) ★ Hyperosmotic solution - high solute concentration (usually greater than 0.3 Osm); gains water ★ Hypo-osmotic solution - low concentration (usually less than 0.3 Osm); loses water ★ Osmotic pressure -pressure exerted on a membrane that separates solutions from different osmolality due to tendency of water to move (can cause a membrane to burst)


What is the meaning of hyperosmotic solution in biology?



--osmotic problems:

 -many diseases

 -ex: Kwashiorkor - bloated stomach due to malnutrition and high content of water in the body ❖ Complication: Tonicity vs. Osmolality

--if a membrane is only permeable to water, then osmolality will always determine the direction of the movement of water. We also discuss several other topics like What is the age crime curve?

--biological membranes are complex and can be permeable to solutes as well as water; which can cause osmolality to change We also discuss several other topics like What does an ectotherm do if environment temperatures are low?

--in this case, initial osmolality of two solutions joined by a membrane will not necessarily determine the direction of movement of water; because osmolality can change as a solute moves across the membrane

 Tonicity - the movement of water across a semipermeable membrane taking all factors into account, including the movement of solutes.


What is the meaning of a hypo-osmotic solution in biology?



 -tonicity is more difficult to measure than osmolality

 -osmolality is a good indicator of the direction of water movement across a membrane

❖ Membrane Permeability

Phospholipid bilayer - a selective barrier to molecular movement

--if no pored in the membrane; only small molecules and non-polar molecules can pass

--non-polar molecules are attracted to non-polar regions in center of the membrane

--concentration gradient required If you want to learn more check out Who is defined as a criminal?
If you want to learn more check out Is the world good or evil?
Don't forget about the age old question of What is the goal of research in psychology?

 -What prevents polar molecules or ions from passing?

--repelled by inner part of membrane

--Molecules that can diffuse through membrane easily:

 --H20, O2, CO2, urea (small molecules <100 MW, even if polar)

Some fatty acids (non-polar)

Some steroid hormones (non-polar)

Vitamins E, A, D (non-polar)

--Molecules that cannot diffuse through membrane easily:

 --Ions (charged); even though small cannot pass through

Polar molecules (larger than urea, H2O >100 MW)

Carbohydrates, proteins, some fatty acids If you want to learn more check out What are the 2 universal taboos?

Mechanisms of transport through membranes

--Membranes must be modified to allow movement through it

I. Channels

--transmembrane, integral protein forms a por

*words highlighted in red are fill-in-the-blank answers

--mainly allows movement of ions across membrane; but water channels (aquaporins) allow faster movement of water than by diffusion alone

--selective (based on size and/or charge of ion); often only one type of particle can pass through --ex: Na+, K+, Cl-, Ca2+

--direction and rate always determined by diffusion gradient (concentration)

Channel Gating Regulation of transport

Regulation - maintaining constant value or change to meet need; ion channel allows movement --the process of opening and closing channels

--proteins can easily change conformation (tertiary structure or shape)

--causes opening or closing of pores in membrane

What stimulates the channel proteins to change their conformation?

A. Ligand-gated channels

--molecule or ion (ligand) binds temporarily to a specific binding site on the transmembrane protein --protein changes conformation (shape)

--ligand is used in gating but is not the main molecule that passes through the channel --one type of ligand per binding site--specificity

-ex: ion-exchange in nerve synapse

B. Voltage

--change in ionic environment in ECF or ICF

--affects charged amino acids on protein

--electrostatic forces change conformation of proteins

--important in nerve transmission

-ex: voltage-gated channel in axon of nerve cell

II. Carrier Mediated Transport (CMT)

​--generally, channels do not allow large molecules to pass

--channels mostly for ions (and water--aquaporins)

CMT - transport of polar molecules and large molecules, as well as some ions

--involves temporary binding of molecules to protein in the membrane (integral membrane protein); allows passage through membrane

--Two types of CMT:

 -Facilitated diffusion and Active transport

Transport protein (carrier protein/transporter) - membrane protein that binds molecule to be transported.

 -allows larger molecules to cross membrane

 -integral, transmembrane proteins

 -temporarily binds molecule to be moved

--All of these properties are used to identify transport proteins:

-specific for the ligand

-has a high affinity (=strength of binding) for a ligand

-can be saturated (limited # of binding sites)

--saturation of transporters are the reason for the abnormally high glucose concentration in the urine of diabetics

--specificity and affinity result from the match between the structure of the ligand and the structure of the binding site on the protein -- (like lock and key; glove and hand)

Carrier-mediated transport - transport protein binds to a specific ligand on one side of the membrane, undergoes a conformational change, causing ligand to move across the membrane. -rate of transport is slower than for channels because of time required for binding

Two types of carrier-mediated transport

*words highlighted in red are fill-in-the-blank answers

1) Facilitated Diffusion - no energy involved 

 -movement = diffusion; channels = ions

--transported molecule must follow diffusion gradient

--one binding site per molecule

--promotes net diffusion

--more particles will dock in the binding site on the side of the membrane with higher concentration --binding → conformational change → release

--driving force for transport comes from the difference in the concentration gradient -ex: transport of glucose; large, polar molecule: GLUT (glucose) transporter in

muscle-insulin independent

2) Active Transport - energy required 

--molecules transported against concentration gradient

--energy required for transport; does not come from the diffusion gradient

--two sources of energy leading to two different types of active transport:

A. Primary active transport

--energy comes from direct hydrolysis

ATPases - enzymes that hydrolyze ATP and liberate energy

--transporters in primary active transport are ATPases

--two binding sites: ligand, ATP

--hydrolysis of ATP is triggered by binding of ligand to transporter

--energy used to transport against concentration gradient

Example of primary active transport: sodium-potassium pump (key transporter) --Pump = transports against gradient

--Na+, K+, ATPase = transports Na+ and K+ with hydrolysis of ATP

--counter transport system: Na+ goes one way, K+ goes the other way

--2K+ into cell, 3Na+ out of the cell per ATP hydrolyzed (electrogenic)

-creates more negativity inside the cell (3 positives out and 2 positives into the cell) --sets up concentration and charge difference across the membrane

--maintains homeostasis; low Na+, high K+ inside cell

-ex: 1 million Na+/K+ pumps in cell of kidney; also important in nerve cells; only 200 pumps in red blood cells (RBC)

Energetically expensive

​--Na+/K+ ATPase consumes ⅓ of total energy of cells

--⅔ of the energy is used by nerve cell

B. Secondary active transport

--energy for transport comes from ion gradient (previously set up by active transport) --binding of ion, usually Na+, increases affinity for different molecule (ex: glucose) --conformational change leading to transport when both bound

--energy from diffusion of Na+ down concentration gradient

-if both molecules move in same direction = co-transport 

-if molecules move in opposite directions = countertransport 

Summary and synthesis

--glucose transport from lumen of kidney into the blood involves several different types of transport - know this cold 

-blood → capillaries → liquid removed from blood → liquids go into tubule (lumen) → absorption --Bulk Transport

-primary → secondary → facilitated

--transport of molecules too large to be transported through membrane (proteins)

*words highlighted in red are fill-in-the-blank answers

--many molecules moved at once (hence “bulk”)

--proteins, polypeptides, neurotransmitters, cholesterol

★ Exocytosis - (movement out of cell) fusion of vesicles with plasma membrane ★ Endocytosis - (movement into cell)

★ Receptor-mediated endocytosis - bulk transport

-ex: bulk transport -- cholesterol movement

-LDL : low density (bad) lipoprotein

-HDL : high density (good) lipoprotein

❖ Cystic Fibrosis

--occurs in about ______ Caucasian births each year

--_______ Genetic defect in __________ -lungs/pancreas

--one of several channel proteins

--amino acid sequence OK; defective process in Golgi apparatus; defective carbo attachment --abnormal Cl-; H2O movement across membrane

--produces thick mucus that promotes bacterial growth

*words highlighted in red are fill-in-the-blank answers

~January 20th, 2017

Two types of carrier-mediated transport

1) Facilitated Diffusion - no energy involved 

 -movement = diffusion; channels = ions

--transported molecule must follow diffusion gradient

--one binding site per molecule

--promotes net diffusion

--more particles will dock in the binding site on the side of the membrane with higher concentration --binding → conformational change → release

--driving force for transport comes from the difference in the concentration gradient

-ex: transport of glucose; large, polar molecule: GLUT (glucose) transporter in

muscle-insulin independent

2) Active Transport - energy required 

--molecules transported against concentration gradient

--energy required for transport; does not come from the diffusion gradient

--two sources of energy leading to two different types of active transport:

A. Primary active transport

--energy comes from direct hydrolysis

★ ATPases - enzymes that hydrolyze ATP and liberate energy

--transporters in primary active transport are ATPases

--two binding sites: ligand, ATP

--hydrolysis of ATP is triggered by binding of ligand to transporter

--energy used to transport against concentration gradient

Example of primary active transport: sodium-potassium pump (key transporter) --Pump = transports against gradient

--Na+, K+, ATPase = transports Na+ and K+ with hydrolysis of ATP

--counter transport system: Na+ goes one way, K+ goes the other way

--2K+ into cell, 3Na+ out of the cell per ATP hydrolyzed (electrogenic)

-creates more negativity inside the cell (3 positives out and 2 positives into the cell)

--sets up concentration and charge difference across the membrane

--maintains homeostasis; low Na+, high K+ inside cell

-ex: 1 million Na+/K+ pumps in cell of kidney; also important in nerve cells; only 200 pumps in red blood cells (RBC)

Energetically expensive

​--Na+/K+ ATPase consumes ⅓ of total energy of cells

--⅔ of the energy is used by nerve cell

B. Secondary active transport

--energy for transport comes from ion gradient (previously set up by active transport)

--binding of ion, usually Na+, increases affinity for different molecule (ex: glucose)

--conformational change leading to transport when both bound

--energy from diffusion of Na+ down concentration gradient

-if both molecules move in same direction = co-transport 

-if molecules move in opposite directions = countertransport 

Summary and synthesis

--glucose transport from lumen of kidney into the blood involves several different types of transport - know this cold 

-blood → capillaries → liquid removed from blood → liquids go into tubule (lumen) → absorption

*words highlighted in red are fill-in-the-blank answers

--Bulk Transport

-primary → secondary → facilitated

--transport of molecules too large to be transported through membrane (proteins) --many molecules moved at once (hence “bulk”)

--proteins, polypeptides, neurotransmitters, cholesterol

Exocytosis - (movement out of cell) fusion of vesicles with plasma membrane

Endocytosis - (movement into cell)

Receptor-mediated endocytosis - bulk transport

-ex: bulk transport -- cholesterol movement

-LDL : low density (bad) lipoprotein

-HDL : high density (good) lipoprotein

❖ Cystic Fibrosis

--occurs in about 2,500 Caucasian births each year

--As a result of a genetic defect in NaCl and water movement across wet epithelial membranes -lungs/pancreas

--one of several channel proteins

--amino acid sequence OK; defective process in Golgi apparatus; defective carbo attachment --abnormal Cl-; H2O movement across membrane

--produces thick mucus that promotes bacterial growth

TOPIC #2 : RENAL SYSTEM

Background on General Aspects of Osmoregulation -- read on own; not covered in class ★ Osmoregulation - regulation of an organism’s fluids and solutes

--total water content

--distribution of water in body compartments (ECF, ICF, blood)\

--concentration of osmolites (Na+, Cl-, glucose, etc.)

--removal of nitrogenous wastes

Importance of water

--Good solvent - polar ----key for cell function

--readily dissolves and transports gases such as O2 and CO2

--high capacity for heat; retains heat; useful in thermoregulation

--only totally continuous medium in body - avenue for long distance communication (ex:hormones dissolved in blood) and transport

--because of its importance, water is a major component of nearly all living systems and its concentration is tightly regulated by many homeostatic mechanisms

Distribution of water

--water = 60% of total body weight; 90% of all molecules in body

--⅔ of water in ICF; ⅓ in ECF

--20% in blood plasma

Edema - excessive fluid in tissue (discussed in detail in Circulatory System)

Osmoregulatory issues in humans: retention of water

--water tends to be lost from the body and must be continuously replenished

--How is water lost?

-air that we breath is dehydrating

-thermoregulation involves water loss through sweating

-water is required to move nitrogenous wastes (ammonia, urea) produced by proteins and amino acid catabolism

*words highlighted in red are fill-in-the-blank answers

Water loss through breathing

--warm air holds more moisture - as temperature rises, amount of water required to saturate air increases as well

--respiratory system (Mouth → Lungs) must be moist for gas exchange

--air before inhaled usually < 100% saturated and cooler than body temperature

--as air enters the body, takes up water from the body as it is heated

--exhaled air has more water than inhaled air

--water loss by breathing is unavoidable

Water loss due to excretion of end products of protein metabolism (urea)

--end products of carbohydrate and lipid metabolism are CO2 and H2O - not very toxic and easily excreted (ex: CO2 via the lungs)

--end products of protein metabolism (ex: ammonia and urea) are more toxic

--ammonia is the direct end product of protein metabolism and is the most toxic

--in organism that occur in aquatic environments (ex: fish), where water is abundant, ammonia is excreted in dilute solutions, but requires large volumes of water to be excreted

--organisms in terrestrial environments, where water is less abundant, convert ammonia into less toxic compounds (ex: urea in humans). Because of its reduced toxicity, urea can be stored in the body at higher concentrations than ammonia and can be excreted in more concentrated solutions. This requires less water to be excreted, and thus less water to be taken in.

--although urea excretion occurs in the kidney, the production of urea from the protein breakdown occurs in the liver which is the most important organ involved in intermediary metabolism Water input, retention and excretion are controlled by a number of physiological and behavioral mechanisms

Thirst - conscious desire for water

--caused by high blood plasma osmolality; detected by hypothalamic (brain) osmolality receptors --the “thirst center” in hypothalamus induces thirst

--stimulated at 304 mOsm (only slightly higher than normal osmolality)

--low blood pressure also leads to thirst

--takes ½ hour after drinking for fluid to become absorbed and to affect receptors

Kidney is the main organ for osmoregulation

--removal of waste for waste production (ex: urea)

--regulation of water concentration

--regulation of solute concentration

Amount of water retained vs. excreted is regulated by hormones which are activated by osmoreceptors and which affect water retention in the kidneys

Similarly, concentration of various ions, most notably Na+ and K+, are regulated by hormones which control excretion vs. retention of these ions in the kidney

--urine volume = minimally 0.41L per day to remove waste; average = 1.5L

--salt intake = 10.5g/day from food

--salt output = .5g in sweat and feces; 10g lost in urine

❖ Renal System -- Function

General Function - to control the volume, osmolality, composition, and pH of body fluids --regulation of water and ions : Na+, Cl-, K+

Regulation - control; adjust to meet needs

--removed metabolic wastes from blood (urea;hemoglobin breakdown products)

--reuglation of pH (ex: secretion of H+ bicrbonate), key function of kidney with lungs --remove foreign chemicals (ex:ingested toxinx; drugs)

*words highlighted in red are fill-in-the-blank answers

--Biosynthesis

Gluconeogenesis - production of glucose

--produces active form of Vitamin D; Ca++ metabolism

Gross Anatomy of kidneys

​Cortex (outer; iso-osmotic), Medulla (inner; hyperosmotic), Major/Minor calyx (“cups”), Renal Pelvis, Ureters

★ Nephron - functional unit of the kidney (100,000 tubule cells);where urine is formed --begins in cortex, then dives into medulla and turn back to leave kidney again

Components of the nephron:

--Bowman’s capsule (Glomerular capsule)

--Proximal convoluted tubule

--Descending loop of Henle (DLOH)

--Ascending loop of Henle (ALOH)

--Distal convoluted tubule

--Collecting duct

 - Outside the kidney:

--Ureter

--Bladder

Two important sets of capillaries in and around nephron

Glomerulus - surrounded by Bowman’s capsule (filtration) --very leaky capillary system Vasa recta (peritubular capillaries) - around tubules; maintain high osmolality of medulla of kidney (traps salt inside of kidney)

--Glomerulus + Bowman’s capsule = renal capsule

Overview of nephron function

1) Blood is filtered under pressure in glomerulus (ex: blood pressure)

2) Most components of blood enter Bowman’s capsule (except large proteins, cells, cell components); filtered liquid in lumen (cavity of tube) called filtrate

3) Components reabsorbed in various places -- from lumen of nepheron into cells of nephron, into interstitial fluid, then into blood

a) Molecules by transporters

b) Ions by pumps/channels/transporters

c) Water by osmosis/aquaporins (water channels)

d) Wastes retained in lumen in nephron’

4) Most components reabsorption upregulated

5) Others (ex: H+, K+, Na+, H20, bicarbonate) - reabsorption/secretion regulated by hormones

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