Week 1

Question 1

2nd messenger system

Answer 1

1) Extracellular ligand binds a surface receptor 2) Morphological or chemical change at the intracellular part of the receptor 3) This causes activation (ie G-Protein, enzyme, ion channel) or direct transcription 4) Activation of a secondary messenger (ie increase cAMP or Ca2+) 5) Secondary effect (ie increased protein production)

Question 2

Buffer

Answer 2

A substance that can bind or release H+ in order to maintain stable pH -E.g H2CO3, phosphates, protein

Question 3

Membrane Potential -What is the typical value?

Answer 3

The difference in electrical charge between the inside and outside of the biological cell. Usually -40mV to -60mV at the exterior of the cell

Question 4

Osmolarity vs Osmolality

Answer 4

OsmolaRity -The number of osmoles per L of solution OsmolaLity -The number of osmoles per Kg of SOLVENT Normal plasma osmolarity 290mOsm/L

Question 5

Transcellular Fluid

Answer 5

The proportion of body water contained in epithelium lined spaces. E.g. CSF, GI fluid, urine in the bladder etc

Question 6

Osmotic Pressure

Answer 6

The pressure necessary to prevent solvent migration (osmosis) -Proportional to the concentration of particles in solution

Question 7

Moles vs Osmoles

Answer 7

Moles -Molecular weight in grams -6x10^23 molecules Osmoles -1 Mole of fully dissociated substance disolved in water

Question 8

Equivalents

Answer 8

The amount needed to react with or supply 1 mole of electrons -Ie 1mol Na+ = 1 eq -1 mol Ca2+ = 2 eq

Question 9

Osmosis

Answer 9

Diffusion of SOLVENT (ie water) to an area of higher SOLUTE (ie ions/protein) concentration -Needs membrane to be impermeable to the solute

Question 10

Tonicity

Answer 10

OsmolaLity of a substance relative to plasma -ie Isotonic, hypotonic, hypertonic

Question 11

Diffusion

Answer 11

-The process where a gas or substance spreads into the total volume available by random movement of its particles. -Net flux=Areas with higher concentration have more particles moving than lower concentration areas -Time to equilibrium is proportional to the square of diffusion distance

Question 12

Solvent drag

Answer 12

When SOLVENT flows through a membrane it can drag SOLUTE with it -Ie Na with water in the renal tubule

Question 13

Transport across cell membranes -What are the different mechanisms?

Answer 13

Passive diffusion down electrochemical gradient Active transport -E.g. Na+/K+ ATP-ase uses energy to transport ions against the gradient -3Na out, 2K+ in -Has alpha and beta subunits, spans the whole membrane Secondary Active Transport -Movement of a “driving ion” (usually sodium) facilitates movement of another molecule -E.g. SGLT1 in bowel and Distal convoluted tubules -Can be Co-transport (SGLT1), molecule moves in same direction -Or counter- transport, opposite direction Ion channels -Voltage gated or ligand gated Aquaporins -Allow passage of water Endocytosis/Exocytosis

Question 14

Fundamentals of Intracellular Communication -What are the types of intracellular communication

Answer 14

Gap Junctions -Local -Directly from cell to cell -Specificity–> anatomic location Synaptic -Local -Across synaptic cleft -Specificity–>anatomic location and receptors Paracrine and autocrine -Locally diffuse -Diffusion in interstitial fluid -Specificity–>Receptors Endocrine -General -Circulating fluids -Specificity–>receptors

Question 15

pH

Answer 15

pH=-log ([H+]) Water at 25 degrees C=7 -This means H+=OH- Normal plamsa pH 7.35-45 -Can vary in different body environments (to maximise protein/enzyme functions)

Question 16

Oncotic pressure

Answer 16

A form of osmotic pressure exerted by proteins in blood vessels. -Tend to pull water into the circulatory system

Question 17

Donnan Effect

Answer 17

An impermeable ions effect on the movements of permeable ions -ie impermeable anionic proteins in blood will attract intracellular cations

Question 18

Body Fluid Compartments -What are the different compartments? -What percentage do they make up? -What are their contents?

Answer 18

Total Body Fluid=60% of body weight ECF=1/3 (20% of weight) -Interstitial 3/4 of ECF (15% of weight) -Intravascular (plasma + cell contents) 1/4 of ECF (5% of weight) -High in NA+Cl ICF= 2/3 (40% of weight) -High in K+, Mg+. proteins of phospates

Question 19

Ficks Law

Answer 19

The magnitude of diffusing tendency from one region to another is directly proportional to the cross sectional area of the barrier and the concentration gradient divided by the thickness of the barrier