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Water
Aspects of Biochemistry
| Question | Answer |
|---|---|
| Why is water considered to be dipolar? | The water molecule has positive and negative poles. The H's are slightly electropositive and the O's are slightly electronegative. |
| What is a hydrogen bond? | An intermolecular force of attraction between hydrogen of one molecule and oxygen (or another electronegative element) of another molecule. |
| Define cohesion. | Water molecules sticking together. |
| Define heat capacity. | The amount of heat required by an object to produce a unit change in it's temperature. |
| Define surface tension. | The property of the surface of a liquid that allows it to resist an external force, due to the cohesive nature of its molecules. |
| What is metabolism? | Term given to all the chemical reactions that occur in an organism. |
| What is anabolism? | Chemical reactions which build up larger biological molecules from smaller ones. |
| What is catabolism? | Chemical reactions which break down large biological molecules into smaller ones. |
| Name the 4 biological macromolecules. | Carbohydrates, lipids, proteins and nucleic acids. |
| Name the sub-unit molecules of carbohydrates. | Glucose |
| Name the sub-unit molecules of lipids. | Glycerol, fatty acids (triglycerides) Glycerol, fatty acid and phosphate (phospholipids) |
| Name the sub-unit molecules of proteins. | Amino acids (20 different types) |
| Name the sub-unit molecules of nucleic acids | Nucleotides (5 different types) |
| Define monomer | Small molecules which link together to form larger molecules. |
| Define polymer | Large molecules which contain several smaller sub-units (usually monomers) |
| All of the 4 main macromolecules are made up of monomers EXCEPT | Lipids |
| Define macromolecule. | A very large molecule comprised of many smaller molecules. |
| Define solute | A substance which dissolves. |
| Define solvent | The substance in which a solute dissolves. |
| Why is water considered a universal solvent? | Polar molecules (eg. glucose) and ions (eg, Na+ and Cl-) are charged and are attracted to the weak charges on water molecules. |
| What is the role of water's solvent properties in organisms? | It functions as a solvent within cells Solvent in transport media e.g. blood plasma, lymph, phloem and xylem saps |
| What is the role of water's solvent properties as an environment? | Solvent for nutrients and gases (oxygen and carbon dioxide) Carbon dioxide is much more soluble than oxygen. |
| Explain what is meant by water having a high specific heat capacity. | 4.2 J are necessary to increase the temperature of 1g of water by 1 degree C; this thermal energy breaks hydrogen bonds between water molecules. |
| What is the benefit of water's high specific heat capacity? | It limits fluctuations in the temperature of organisms and the environment of those that live in water. |
| Explain what is meant by water having a high latent heat of vaporisation. | Much thermal energy is needed to cause water to change to water vapour. |
| What is the benefit of water's high latent heat of vaporisation to organisms? | Loss of water for cooling (e.g. in transpiration and sweating) is efficient as a lot of thermal energy is needed to evaporate small quantities of water. |
| What is the benefit of water's high latent heat of vaporisation as an environment? | Water in shallow aquatic habitats (e.g. ponds, rock pools) does not evaporate too quickly. |
| Explain what is meant by water having a high latent heat of fusion. | Much thermal energy is needed to change ice to water; much is transferred from water when it forms ice. |
| What is the benefit of water's high latent heat of fusion? | Water in cells tends to stay as a liquid, so cell membranes are not damaged by ice crystals. |
| Explain why water is considered reactive. | Water splits to form hydrogen ions (H+) and hydroxyl ions(OH-) |
| What is the benefit of water's reactivity in organisms? | It is useful as a raw material for photosynthesis Provides hydrogen ions and electrons for photosynthesis and respiration Used in hydrolysis reactions e.g. digestion |
| What is special about the density of water? | Solid water (ice) is LESS dense than liquid water. |
| Density of water is important in water's role as a habitat. Explain. | Ice floats on water - it acts as an insulation for aquatic organisms beneath. |
| Water is incompressible. What benefit is this to organisms? | Support if provided to organisms with hydrostatic skeletons e.g. sea anemones, worms. Turgidity in plant cells gives support. |
| Why do water molecules have high cohesion? | Hydrogen bonds hold water molecules together. |
| What is the importance of cohesion in water's role in organisms? | It supports columns of water moving up through xylem vessels by capillary action. |
| What is the importance of cohesion in water's role as a habitat? | Gives surface tension - some organisms live on the surface of water. |
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CAPE Biology Unit 1
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