IB Biology Unit 2.2

Methanogenic Prokaryotes

- Can be found in swamps, wetlands, the guts of animals (including cattle and sheep). - Can also be found in waste dumps

Give examples of how organisms exploit this Adhesion

- Capillary action is caused by the combination of adhesive forces causing water to bond to a surface, e.g. the sides of a xylem vessel and the cohesive forces bonding water molecules together. - Capillary action is helpful in the movement of water during transpiration and also when you drink using a straw.

Explain how the body exploits this property of water to cool the body using sweat.

- Excess heat energy is removed from the body (latent heat of evaporation). - Skin + Blood vessels are cooled. - Because blood is mostly water, cooler blood can circulate to other parts of the body to cool them down. - This property also helps aquatic habitats remain at fairly constant temperatures in hot summers.

Outline the consequences, to cells, of not cooling the human body.

- High temperatures damage tissues and denature proteins - causing enzymes to cease to work.

Sodium Chloride - Solubility + Relation to Blood Transport

- Ionic compound - Freely soluble in water dissolving to form sodium ions (Na+) and chloride ions (Cl-) - Carried in the blood plasma

What property of water means it is useful as a coolant?

- It takes a lot of heat for water to evaporate. - As a result, when water evaporates it removes a lot of heat from the system which provides a cooling effect

Fats - Solubility in Water + Relation to Blood Transport

- Large, non-polar molecules - Insoluble in water - They are carried in blood inside lipoprotein complexes (in the plasma).

Give examples of how organisms exploit these solvent properties

- Metabolic reactions happen most readily in solutions of water - water in cells dissolves the reactants /substrates. - Cells are mostly water therefore diffusion into and out of them happens most easily if the substance concerned is in solution, e.g. before oxygen diffuses from the alveoli to the blood it dissolves into the moist layer lining the alveoli. - Soluble substances such as sucrose can be easily transported around the plant in the phloem. Once dissolved in the water of the phloem the sucrose can be moved to where it is needed by mass flow.

Cholesterol - Solubility in Water + Relation to Blood Transport

- Molecules are hydrophobic, apart from a small hydrophilic region at one end. - This is not enough to make cholesterol dissolve in water. -They are carried in blood in lipoprotein complexes (in the plasma).

Hydrophobic

- Non - polar - Molecules are hydrophobic if they do not have negative or positive charges and are nonpolar - All lipids are hydrophobic, including fats and oils -Hydrophobic molecules dissolve in other solvents such as propanone (acetone)

Oxygen - Solubility in Water + Relation to Blood Transport

- Non-polar molecule - Due to the small size of an oxygen molecule it is soluble in water, but only just water becomes saturated with oxygen at relatively low concentrations - As temperature increases the solubility of oxygen decreases - At body temperature (37 °C) very little oxygen can be carried by the plasma, too little to support aerobic respiration hemoglobin in red blood cells carry the majority of oxygen - Haemoglobin has (4) binding sites for oxygen

Hydrophillic

- Polar - All substances that dissolve in water are hydrophilic, including polar molecules such as glucose, and particles with positive or negative charges such as sodium and chloride ions. -Substances that water adheres to, cellulose for example, are also hydrophilic.

Glucose - Solubility in Water + Relation to Blood Transport

- Polar molecule hence freely soluble. -Carried in the plasma - blood plasma is 95% water.

- Give examples of how organisms exploit cohesion

- Pond Skaters using the surface tension of water. - Surface tension is caused by the cohesive hydrogen bonding resisting an object trying to penetrate the surface.

Amino Acids - Solubility in Water + Relation to Blood Transport

- Positive and negative charges (due to the amine and acid groups) therefore soluble in water. - R group varies, can be polar, non-polar or charged. - Carried in the plasma - blood plasma is 95% water.

Water Solvent Properties + Bonding

- The polar attraction of large quantities of water molecules can interrupt intra-molecular forces (such as ionic bonds) and resulting in the dissociation of the atoms. - Positive atoms, e.g. Na+ end up being surrounded by the negative oxygen regions of water molecules and the Cl- being surrounded by the positive hydrogen region of water molecules. - Because of this water is often (wrongly) referred to as being the 'universal solvent', it is however a very good solvent for many substances.

Water Cohesive Properties + Bonding

- This property occurs as a result of the polarity of a water molecule and its ability to form hydrogen bonds. - Although hydrogen bonds are weak the large number of bonds present (each water molecule bonds to four others in a tetrahedral arrangement) gives cohesive forces great strength.

Water Adhesive Properties + Bonding

- This property occurs as a result of the polarity of a water molecule and its ability to form hydrogen bonds. -Again similarly individual hydrogen bonds are weak, but large number of bonds gives adhesive forces great strength.

Methane Properties

- Waste product of anaerobic respiration in certain prokaryotes living in anaerobic conditions. - Methane can be used as a fuel. - If present in the atmosphere it contributes to the greenhouse effect.

Explain why the water molecule is polar. Refer to electrons and covalent bonding in your answer.

- Water (H2O) is made up of two hydrogen atoms covalently bound to an oxygen atom. -While this bonding involves the sharing of electrons, they are not shared equally. -The number of protons in each atom is different; oxygen atoms have 8 whilst hydrogen atoms have just 1 having more protons the oxygen atoms attract the electrons more strongly. -Thus the oxygen end of the molecule becomes slightly negative and the hydrogen end becomes slightly positive.

Water as a Solvent outline

- Water can dissolve many organic and inorganic substances that have charged or polar regions.

Water Thermal Properties + Bonding

- Water has a high heat of vaporisation (amount of energy needed to change from a liquid to a gas or vapour). - Water has a high heat of fusion (amount of energy needed to be lost to change liquid water to ice). - These properties are due to many hydrogen bonds that need to be formed or broken to change the temperature or state of water. - Therefore the temperature of water remains relatively stable.

Water Thermal Outline

- Water has a high specific heat capacity (4.2 Joules is required to raise the temperature of 1 g of water by 1°C).

- Give examples of how organisms exploit these thermal properties

- Water is used by Leaves as a coolant. - The heat lost from leaves for evaporation prevents them over-heating. - If the leaves get too hot enzymes in their cells will start to denature.

Water Cohesive Outline

- Water molecules are strongly cohesive (they tend to stick to one another).

Water Adhesive Outline

- Water molecules tend to stick to other molecules that are charged or polar for similar reasons that they stick to each other.