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38 Cards in this Set
- Front
- Back
How many elements approx naturally occur in the earth's crust?
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100
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How many elements are essential for life?
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16
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What are the 4 most common elements in organisms?
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C, H, N, O.
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What elements are commonly found in organisms in smaller quantities (8)?
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Phosphorus, Sulphur, Na, K, Mg, Cl, Ca, Fe.
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Why are HONC biologically significant?
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They can form more stable covalent bonds than any other elements with the same valencies (1 2 3 4 respectively).
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Carbon's special property:
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It's tetravalent - can form 4 covalent bonds with other atoms. Can be other Cs or from other elements. Bonds point towards tetrahedron vertices - v stable arrangement.
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Carbon bonds:
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C-C bonds v strong. Long chains rings or branched chains can exist in a single molecule. They can also form double bonds i.e. >C=C< or >C=O, >C=N-), hence there is an enormous variety of C-containing molecules.
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Structure and formula of glycerol:
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C>3H>8O>3
H H H | | | H-C-C-C-H | | | O O O | | | H H H |
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Structure of glycine:
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H H O
\ | # N-C-C / | \ H H O-H |
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Structure of glucose:
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CH>2OH
| H C--O H \/H OH\/ C C / \OH H/ \ OH C--C OH | | H OH |
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The human body is about ... water:
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60%
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Polar molecule because:
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Shared electrons are pulled towards the O atom giving it a slightly negative charge and leaving each H atom with a slightly positive charge.
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Hydrogen bonds make water such an important factor for living organisms because:
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negative and positive molecule ends attract each other so the molecules tend to stick together.
||| between two atoms ie H|||O = hydrogen bonds. Say hydrogen not H-bond in exam. |
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Why is water the universal solvent?
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So many things dissolve.
Ionic substances carry + and - charges so they are attracted to the charges on the H2O Molecules. Water surrounds separated molecules. Other polar substances eg some sugars and alcohols also dissolve in the same day. - ion - hs surrond + ion - os surround |
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Why is water's use as a solvent relevant?
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Solution - molecules and ions free to move - more chemically reactive. Maj of cell reactions take place aqueous sols.Also, good transport medium because of solvent properties.
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Why is it relevant that non-polars and water will not mix?
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eg Lipids will not mix and usually group together in its presence - important for membrane stability.
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What is surface tension?
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Water mols more attracted to each other than to surrounding air.
Attraction between mols of sim subst called cohesion.Not easily broken, water has greater surface tension than most liquids. |
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Apart from itself, water tension in:
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Can form H bonds with other polars - stick to each other but also other surfaces IE side of container.
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Relevance of surface tension:
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Significant in cells and translocation in plants. Important for many small organisms who rely on surface tension in order to settle on water or skate over its surface.
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Specific heat capacity:
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the amount of heat energy (J) required to raise the temp of 1kg of water by 1C.
Water has high shc - gain much to raise, lose much to lower. Buffer against extreme temp flucts in environ. |
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Latent heat of vaporization:
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Water has high lhv - lot J (heat) needed to evap. When, draws much heat energy out of the material underneath - cooling effect (sweating, panting, plant cooling) - much heat lost without much water loss.
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Latent heat of fusion:
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Water must losse a lot of heat J before it forms ice crystals. Cells and environs are less likely to freeze (ice crystals v damaging in cells).
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What is the difference between adhesion and cohesion?
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Adhesion is for different substances, cohesion is for the same substance.
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When is water most dense? What happens afterwards?
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4C - Density decreases as it feezes so ice floats.
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Why does ice float?
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Gets less dense - in liquid H bonds constantly form and reform - when frozen forms H bonds with 4 other mols - rigid lattic holds mols further apart than in liquid - expands and becomes less dense.
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Why is it important that ice floats?
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Insulates water below it - allows nutrient cycling in larged bodies of water - life can survive to greater depth.
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Important that transparent and colourless:
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Aquatic plants can get sunlight and photo. - O2 into water, feeds fish etc. (plants are producers).
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Has relatively high density compared with air:
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Large animals can float. Dispersal of repro structures eg larvae and large fruits.
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Difficult to compress:
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Shock absorber in mammalian joints - allows movement via synovial fluid. Important structural agent. Plants remain turgid, support for hydroskeletal animals.
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Conducts electricity
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Nervous response
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How good an electrical conductor is water?
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Pure has low but dissolved ions make good
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Good that water is liquid at room temp:
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transport in cells, synovial fluid allows to move
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What is a reagent? Why is it good that water is one?
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Takes part in chemical reaction. Photosynthesis, hydrolysis (digestive system etc) - many take place in water.
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Low viscosity:
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Can change shape so things can be dissolved (more reactive), can get through narrow vessesl (blood and xylem), lubricant (mucus and saliva for swallowing).
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Water columns do not break or pull apart easily:
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transport in plant and animal bloodstreams - continuous column can be pulled up to tree top.
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Water is universal solvent
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dissolving good for transport as main transport medium - also makes more reactive.
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Ice less dense than water
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Heat not lost in convection - water animals can survive, ditto nutrients and nutrient cycling.
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High surface tension
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Pond skaters
Translocation in plants and cvells - can move up stem. |