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The Functional Organisation Of The Body Notes

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The Functional Organisation of the Body Nerve cells Transmit information in the form of electrical signals Some neurones receive information from the outside environment Other neurones command muscles, glands etc

Muscle cells Elongated cells specialised in generating force Their membranes carry electrical charge like nerve cells

Epithelial cells Form continuous sheet-like layers on non-cellular material called basement membrane. Separate the body from the external environment Some cells transport ions, inorganic molecules and water from one side to the other Can form glands, which secrete to the outside of the body (exocrine glands) or into the blood (endocrine)

Connective tissue Widely scattered cells embedded in a non-cellular material - extracellular matrix In tendons, these cells are surrounded by a meshwork of long molecules which provide mechanical strength and elasticity

TISSUE An association of similar cells which perform similar function

ORGAN Associations of tissues which combine to perform specific function of the body Nervous, musculoskeletal, cardiovascular, digestive, reproductive, urinary, immune, endocrine, integumentary, respiratory

Absorption Intake of various molecules into the blood from the lumen eg water & nutrients from the GI tract

Secretion Transport into the lumen eg HCl & other chemicals needed for digestion in the stomach

Filtration Movement of small molecules through cellular/molecular sieves eg kidneys

Re-absorption Some materials may be filtered out first but then retrieved 40%

from the GI or kidneys Extracellular fluids constitutes the internal environment of the body

Homeostasis 60%


The maintenance of a constant internal environment




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Molecular Composition of cells Water Water is a dipole and will interact with ions such as NaCl and other polar molecules but not with non-polar molecules such as oil

Carbohydrates Are highly polar and therefore soluble in water Exist as monomers, dimers and polymers Are important sources of energy, components of the cell membrane and the backbone of nucleic acids

Lipids Non-polar since composed of mostly C and H atoms Fatty acids are non-polar, water incoluble molecules used to store energy Phospholipids have a polar head and a non-polar fatty acid tail making them amphipathic. They form cluster in water and are used to form cell membranes Steroids have 4 cycles of carbon atoms and are important components of plasma membrane, also acting as signalling molecules

Proteins Longs chains of subunits called amino acids AA have the same backbone but different side chains making them different AA are joined to form long chain proteins Membrane protein function: anchoring, receptors, channels, gated channels, reactions, carriers

Nucleic acids DNA is built of numerous nucleotides connected by phosphoric residues

Physiology of the Cell Membrane conc in mM K+
ClHCO3Inorganic PAmino Acids Glucose Protein ATP

INSIDE 140 15

0.8 0.001 4 10 40 8 1 4 4


1.5 1.8 115 25 2 2

5.8 0.2 0

The cell membrane is not freely permeable to these molecules otherwise the concentration would be equal Polar molecule and ions cannot pass through [glucose, AA, H+, Na+, Cl-]
Small uncharged molecules can pass through [O2, CO2, ethanol, glycerol]
because they can temporarily dissolve in the lipid bilayer The cell can actively move molecules across the membrane

Passive Movement along the concentration gradient by using the energy of the gradient

Active Uses energy supplied by the cell to power protein pumps against the concentration gradient

Transport is driven by both the chemical and electrical gradients combining to create the electrochemical driving force The movement of charged particles across the membrane depends on the sum of the force generated by the chemical gradient and the electrical field

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