Glossary of Biology - AS Level - 10.1 - Biological Molecules - .7 - Organic Elements and Wat
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- How many elements approx naturally occur in the earth's crust?
- How many elements are essential for life?
- What are the 4 most common elements in organisms?
- C, H, N, O.
- What elements are commonly found in organisms in smaller quantities (8)?
- Phosphorus, Sulphur, Na, K, Mg, Cl, Ca, Fe.
- Why are HONC biologically significant?
- They can form more stable covalent bonds than any other elements with the same valencies (1 2 3 4 respectively).
- Carbon's special property:
- 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.
- Carbon bonds:
- 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.
- Structure and formula of glycerol:
H H H
| | |
| | |
O O O
| | |
H H H
- Structure of glycine:
- H H O
\ | #
/ | \
H H O-H
- Structure of glucose:
H C--O H
/ \OH H/ \
OH C--C OH
- The human body is about ... water:
- Polar molecule because:
- Shared electrons are pulled towards the O atom giving it a slightly negative charge and leaving each H atom with a slightly positive charge.
- Hydrogen bonds make water such an important factor for living organisms because:
- 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.
- Why is water the universal solvent?
- 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
- Why is water's use as a solvent relevant?
- 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.
- Why is it relevant that non-polars and water will not mix?
- eg Lipids will not mix and usually group together in its presence - important for membrane stability.
- What is surface tension?
- 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.
- Apart from itself, water tension in:
- Can form H bonds with other polars - stick to each other but also other surfaces IE side of container.
- Relevance of surface tension:
- 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.
- Specific heat capacity:
- 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.
- Latent heat of vaporization:
- 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.
- Latent heat of fusion:
- 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).
- What is the difference between adhesion and cohesion?
- Adhesion is for different substances, cohesion is for the same substance.
- When is water most dense? What happens afterwards?
- 4C - Density decreases as it feezes so ice floats.
- Why does ice float?
- 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.
- Why is it important that ice floats?
- Insulates water below it - allows nutrient cycling in larged bodies of water - life can survive to greater depth.
- Important that transparent and colourless:
- Aquatic plants can get sunlight and photo. - O2 into water, feeds fish etc. (plants are producers).
- Has relatively high density compared with air:
- Large animals can float. Dispersal of repro structures eg larvae and large fruits.
- Difficult to compress:
- Shock absorber in mammalian joints - allows movement via synovial fluid. Important structural agent. Plants remain turgid, support for hydroskeletal animals.
- Conducts electricity
- Nervous response
- How good an electrical conductor is water?
- Pure has low but dissolved ions make good
- Good that water is liquid at room temp:
- transport in cells, synovial fluid allows to move
- What is a reagent? Why is it good that water is one?
- Takes part in chemical reaction. Photosynthesis, hydrolysis (digestive system etc) - many take place in water.
- Low viscosity:
- Can change shape so things can be dissolved (more reactive), can get through narrow vessesl (blood and xylem), lubricant (mucus and saliva for swallowing).
- Water columns do not break or pull apart easily:
- transport in plant and animal bloodstreams - continuous column can be pulled up to tree top.
- Water is universal solvent
- dissolving good for transport as main transport medium - also makes more reactive.
- Ice less dense than water
- Heat not lost in convection - water animals can survive, ditto nutrients and nutrient cycling.
- High surface tension
- Pond skaters
Translocation in plants and cvells - can move up stem.
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