IBDP Bio

Chemistry of Life3.1 Chemical Elements and Water

3.1.1 State the most frequently occurring chemical elements in living things.

Carbon- forms 4 covalent bonds, ex: CH4

Hydrogen- forms 1 covalent bond, ex: H2

Oxygen- forms 2 covalent bonds ex: CO2

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•Carbon is not only important elements required by cells. Oxygen, Nitrogen, and Hydrogen are also very important elements. •Other important elements needed by living organisms are sulphur, calcium, phosphorus, iron, and sodium.

3.1.2 State that a variety of other elements are needed by living organisms. Nitrogen Sulfur Calcium Phosphorus Potassium Iron

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3.1.3 State one role for each of the elements named in 3.1.2.

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Nitrogen and Sulfur- found in proteins.

Calcium- found in bones.

Phosphorus- found in nucleic acids (DNA & RNA.)

Sodium & Potassium- help transmit nerve impulses.

Iron- found in hemoglobin (carries oxygen in blood.)

3.1.4 Draw and label a diagram showing the structure of water molecules to show their polarity and hydrogen bond formation.

Dashed blue lines represent hydrogen bonds.

6Courtesy of Thomas Splettstoesser

3.1.5 Outline the thermal, cohesive and solvent properties of water. Thermal- water has

a high specific heat. Cohesive- water

molecules tend to attract each other, which results in high surface tension

Solvent- polarity of water gives it strong solvent properties.

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Courtesy of Michael Apel

Thermal Properties of Water

Definition: specific heat capacity - Is the measure of the heat energy needed to increase the temperature of an object y 1 degree Celsius.

Water has a relatively high specific heat capacity; it needs a lot of energy to heat up. (more energy to change temperature, it becomes hot slower)

Can absorb and keep for a long time.

Because hydrogen bonds must be broken to separate molecules and make move further apart.

Solvent Properties of Water

Is a universal solvent.

Substance (polar) can dissolve in water (hydrophilic) if its attractive forces are equal to or stronger than the attractive forces of water.

Substances cannot dissolve in water (hydrophobic) if its properties do not allow it to overcome water’s strong attractive forces.

Cohesive and Adhesion Properties of Water

Cohesion refers to the ability of water to stick to itself.

Due to polarity and subsequent attractions of water molecules to one another.

Results in high surface tension

Adhesion refers to the ability of water to stick to other things.

3.1.6 Explain the relationship between the properties of water and its uses in living organisms.

Coolant- animals loose heat by sweating.

Transport medium- blood, plant fluid.

Metabolic medium- many metabolic reactions take place in water.

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Water serves as a transport medium for blood tissue.

Properties of Water

Remains liquid over a wide temperature range, including temps where most small molecules are gases.

Dissolves most substances involved in living processes such as oxygen, carbon dioxide, glucose, amino acids, and sodium chloride.

Changes temperature gradually when heated or cooled

It protects cells from rapid temperature changes and provides a stable environment for cell reactions

Properties of Water

Is one of the only pure substances that expand when it becomes solid, which makes it float when frozen.

Transparent. Plants need for photosynthesis.

Molecules with uneven charge distribution are polar (have oppositely charged poles)

Properties of Water

(Even distribution of charges makes it nonpolar)

Charge of water molecule is 0 (neutral).

Water is a coolant

Makes up sweat. Takes a lot of energy to turn into gas. It takes heat energy from body cooling body.