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26 Cards in this Set
- Front
- Back
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The body's two main circulatory systems |
Lymph & cardiovascular |
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Components of the cardiovascular system |
-Heart -arterial system -capillaries -venous system -blood |
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Function of the Cardiovascular system |
1) Transport of nutrients, gases and waste products, 2) thermoregulation, 3) distribution of water electrolytes and hormones and 4) immune defence. Blood is pumped through CVS by heart, flows through aorta into major arteries, arterioles, venules and veins, returns to the heart. -5% of blood volume in capillaries at one moment -Nutrients and metabolic products diffuse through the endothelial capillary wall into and out of cells, via the ECF. |
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Functions of biological membranes |
1) selective barrier- holds enzymes and metabolites inside, regulates entry 2) organisation- compartments that surround organelles- maintains distinct molecular environments 3) transport- contains specific molecular pumps and channels for solute transportation 4) control information flow- receptors for external signalling, electrical and chemical signalling 5) cell-cell interactions- cell recognition and adhesion 6) reactions- enzyme activity |
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Phospholipid structure |
Polar head, containing phosphate, glycerol and choline- Hydrophilic
Hydrophobic fatty acid tail.
Amphipathic |
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Amphipathic |
Molecule that has both hydrophilic and hydrophobic parts. |
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Fluid mosaic model |
Each monolayer is a 2D liquid- molecules can diffuse sideways, freely within their own monolayer.
Molecules rarely flip flop (move from one leaflet to the other), except for cholesterol. |
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Membrane lipid families |
1) Phospholipids- have a glycerol back bone, two fatty acid chains (average length 16-18 carbons), a phosphate group and usually an alcohol (either serine, ethanolamine, choline or inisitol)
2) derived from sphingosine (a more complex alcohol) e.g. sphingomyelin.
Glycosphingolipids associate together, reducing fluidity. |
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Cholesterol in the membrane |
is a major membrane lipid present in roughly equal amounts with phospholipids. It is a large disc-like molecule with one end hydrophilic and the rest hydrophobic and embedded in the hydrophobic portion of the plasma membrane. Cholesterol makes the membrane less flexible and even less permeable.
ie. amount of cholesterol in the membrane determines fluidity and permeability. |
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Factors affecting membrane fluidity and permeability |
1) Phospholipid tail length- increased length = increased fluidity. 2) number of double bonds in the acid tail - (degree of unsaturated)- if unsaturated (double bond), has a kink, which stops from packing well = increased fluidity. 3) Temperature- Fluidity increases with temp 4) Cholesterol- makes membrane less flexible.
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Fick's Law of diffusion |
"The rate of transfer of a gas through a sheet of tissue is proportional to the tissue area and the dirfference in gas partial pressure between the 2 sides and inversely proportional to the tissue thickness." ie. Describes the effect of different factors influencing the rate of net diffusion of a substance across a membrane. |
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Simplified equation for Fick's law |
Net rate of diffusion (flux) = concentration gradient x membrane surface area x diffusion coefficient / membrane thickness |
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Non ionic diffusion |
Some uncharged molecules can cross the membrane- eg. base NH3, acid HCOOH, however the charged form cannot (NH4+, HCOO-)
-pH determines whether a substance is charged or not. |
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Integral membrane proteins |
Permanently attached to the cell membrane bilayer. Two types
1) Span entire membrane - once or many times. eg. voltage gated ion channels, hormone receptors
2) Integral monotopic proteins - not covalently bound, don't span entire membrane |
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Functions of membrane proteins |
1) Transport - hydrophilic channel, ATP pump 2) Enzyme functions (active site exposed) 3) Signal transduction (Detect external signals0 4) Cell recognition- molecules are recognised by other cells 5) Control adhesion- between cells and ECM 6) Cytoskeletal attachment - microfilaments |
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Membrane channels |
The protein transmembrane channels that permit simple or facilitated diffusion. -May be open or closed, or gated. -Rate of movement limited by rate of diffusion. |
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Types of gated ion channels |
1) Voltage gated (Na+ or K+)
2) chemical or ligand gated (ACh)
3) Mechanically gated (eg. sound waves in inner ear) |
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Ion movement via transport protein is affected by... |
1) concentration gradient
2) electrical gradient. |
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Nernst Equation |
Used to find the equilibrium potential- the membrane voltage for the ion to be in equilibrium. |
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Nerve cell transmission |
Can be activated by 1) electrical stimuli (an action potential) or 2) chemical stimuli by a neurotransmitter (Eg. ACh) |
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Ligand gated ion channels |
Ion channels open or close in response to the binding of a ligand. Ligands may be extracellular or intracellular.
Examples of external ligands- 1) ACh- binds to nicotinic acetylcholine receptor, which opens Na+ channel, allowing sodium through (Depolarisation) 2) GABA- binds at synapses at CNS, admits Cl- ions into the cell, inhibiting nerve impulses. |
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Basic mechanism for transport through cell sheets |
Active transport on one side of the cell -Simple / facilitated diffusion on other side of the cell. |
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Large molecule transport (endocytosis) |
1) pinocytosis 2) receptor mediated endocytosis 3) phagocytosis |
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Pinocytosis |
Continuous non specific uptake of ECF and small dissolved molecules. |
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Receptor mediated endocytosis |
-via clathrin coated pits in epithelial and phagocytic cell membranes. (pits contain protein receptors for things endocytosed)
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via cavolin coated pits in vascular endothelial cells and adipocytes (transport of albumin/ folate?) |
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Phagocytosis |
Endocytosis of large particulate matter eg. microorganisms, cell debris, by specialised phagocytic cells. |
