Module+03+The+Chemistry+of+Life


 * __3.1 Chemical elements and water__**

3.1.1 State that the most frequently occurring chemical elements in living things are carbon, hydrogen, oxygen and nitrogen. 3.1.2 State that a variety of other elements are needed by living organisms, including sulfur, calcium, phosphorus, iron and sodium. 3.1.3 State one role for each of the elements mentioned in 3.1.2. 3.1.4 Draw and label a diagram showing the structure of water molecules to show their polarity and hydrogen bond formation. 3.1.5 Outline the thermal, cohesive and solvent properties of water. 3.1.6 Explain the relationship between the properties of water and its uses in living organisms as a coolant, medium for metabolic reactions and transport medium 3.2.1 Distinguish between //organic// and //inorganic// compounds. 3.2.2 Identify amino acids, glucose, ribose and fatty acids from diagrams showing their structure. 3.2.3 List three examples each of monosaccharides, disaccharides and polysaccharides. 3.2.4 State one function of glucose, lactose and glycogen in animals, and of fructose, sucrose and cellulose in plants. 3.2.5 Outline the role of condensation and hydrolysis in the relationships between monosaccharides, disaccharides and polysaccharides; between fatty acids, glycerol and triglycerides; and between amino acids and polypeptides. 3.2.6 State three functions of lipids. 3.2.7 Compare the use of carbohydrates and lipids in energy storage
 * __3.2 Carbohydrates, lipids and proteins__**


 * __3.3 DNA structure__**

3.3.1 Outline DNA nucleotide structure in terms of sugar (deoxyribose), base and phosphate. 3.3.2 State the names of the four bases in DNA. 3.3.3 Outline how DNA nucleotides are linked together by covalent bonds into a single strand. 3.3.4 Explain how a DNA double helix is formed using complementary base pairing and hydrogen bonds. 3.3.5 Draw and label a simple diagram of the molecular structure of DNA.

The phosphate group is covalently bonded to the carbon of the deoxyribose and then nitrogenous base is attached to the deoxyribose.
 * 3.3.1 : A DNA is composed of a deoxyribose, a phosphate group and a nitrogen base.

[[image:6k8b9iqkYtjQp0NO4NvIyQ_m.jpg width="184" height="146"]] media type="youtube" key="etmZIi7HfZw" width="210" height="175"

 * 3.3.2 : adenine (A),cytosine (C),guanine (G),thymine (T).

media type="youtube" key="ycjH_ZnN3U0" width="167" height="140" > Two DNA nucleotides can be linked together by a covalent bond between the sugar of one nucleotide and the phosphate of another. More nucleotides can be added to form a single strand. >
 * 3.3.3 : A covalent bond forms between the sugar of one nucleotide and the phosphate group of another nucleotide.
 * 3.3.4 : DNA is made up of two nucleotide strands. The nucleotides are connected together by covalent bonds within each strand. The sugar of one nucleotide forms a covalent bond with the phosphate group of another. The two strands themselves are connected by hydrogen bonds. The hydrogen bonds are found between the bases of the two strands of nucleotides. Adenine forms hydrogen bonds with thymine whereas guanine forms hydrogen bonds with cytosine. This is called complementary base pairing. Below is a digram showing the molecular structure and bonds within DNA.
 * 3.3.5 :


 * __3.4 DNA replication__**

3.4.1 Explain DNA replication in terms of unwinding the double helix and separation of the strands by helicase, followed by formation of the new complementary strands by DNA polymerase 3.4.2 Explain the significance of complementary base pairing in the conservation of the base sequence of DNA 3.4.3 State that DNA replication is semi-conservative.


 * 3.4.1 : DNA replication is semi-conservative as both of the DNA molecules produced are formed from an old strand and a new one. The first stage of DNA replication involves the unwinding of the double strand of DNA (DNA double helix) and separating them by breaking the hydrogen bonds between the bases. This is done by the enzyme helicase. Each separated strand now is a template for the new strands. There are many free nucleotides around the replication fork which then bond to the template strands. The free nucleotides form hydrogen bonds with their complimentary base pairs on the template strand. Adenine will pair up with thymine and guanine will pair up with cytosine. DNA polymerase is the enzyme responsible for this. The new DNA strands then rewind to form a double helix. The replication process has produced a new DNA molecule which is identical to the initial one.

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 * 3.4.2 : Complementary base pairing is very important in the conservation of the sequence of DNA. This is because adenine always pairs up with thymine and guanine always pairs up with cytosine. As DNA replication is semi-conservative (one old strand an d one new strand make up the new DNA molecules), this complementary base pairing allows the two DNA molecules to be identical to each other as they have the same base sequence. The new strands formed are complementary to their template strands but also identical to the other template. Therefore, complementary base pairing has a big role in the conservation of the base sequence of DNA.
 * 3.4.3 :The replication is semiconservative. Each strand acts as a template for the synthesis of a new DNA molecule by the sequential addition of complementary base pairs, thereby generating a new DNA strand that is the complementary sequence to the parental DNA. Each daughter DNA molecule ends up with one of the original strands and one newly synthesized strand.
 * __3.5 Transcription and translation__**

3.5.1 Compare the structure of RNA and DNA. 3.5.2 Outline DNA transcription in terms of the formation of an RNA strand complementary to the DNA strand by RNA polymerase. 3.5.3 Describe the genetic code in terms of codons composed of triplets of bases. 3.5.4 Explain the process of translation, leading to polypeptide formation. 3.5.5 Discuss the relationship between one gene and one polypeptide.


 * __3.6 Enzymes__**

3.6.1 Define //enzyme// and //active site//. 3.6.2 Explain enzyme–substrate specificity. 3.6.3 Explain the effects of temperature, pH and substrate concentration on enzyme activity. 3.6.4 Define //denaturation//. 3.6.5 Explain theuse of lactase in the production of lactose-free milk.
 * __3__****__.7 Ce__****__ll respiration__**

3.7.1 Define //cell respiration//. 3.7.2 State that, in cell respiration, glucose in the cytoplasm is broken down by glycolysis into pyruvate, with a small yield of ATP. 3.7.3 Explain that, during anaerobic cell respiration, pyruvate can be converted in the cytoplasm into lactate, or ethanol and carbon dioxide, with no further yield of ATP. 3.7.4 Explain that, during aerobic cell respiration, pyruvate can be broken down in the mitochondrion into carbon dioxide and water with a large yield of ATP.

✔ Cell respiration is the controlled release of energy from organic compounds in cells to form ATP. ✔ ATP or Adenosine triphosphates is the molecule which directly fuels the majority of biological reactions.

✔ Cell respiration:
 * Location: cytoplasm
 * Process: glycolysis
 * Substrate: Glucose
 * Products: __**2 Pyruvate**__ and a small amount of ATP
 * Glycolysis does __**not**__ use oxygen.

✔ Anaerobic cell respiration:
 * Anaerobic respiration is the oxidation of organic compounds without oxygen.
 * It is less efficient than aerobic respiration (with oxygen).
 * There are different types of anaerobic respiration. Here we will compare anaerobic respiration in yeast and humans.
 * E.g. Human anaerobic cell respiration:
 * Location: Cytoplasm
 * Substrate: Glucose
 * Product: lactic acid (lactate) + ATP
 * Note: lactic anaerobic respiration supplements aerobic respiration in the production of ATP. Both aerobic and anaerobic respiration can take place in the human cell at the same time.

✔ During aerobic cell respiration, pyruvate can be broken down in the mitochondrion into carbon dioxide and water with a large yield of ATP.


 * __3.8 Photosynthesis__**

3.8.1 State that photosynthesis involves the conversion of light energy into chemical energy. 3.8.2 State that light from the Sun is composed of a range of wavelengths (colours). 3.8.3 State that chlorophyll is the main photosynthetic pigment. 3.8.4 Outline the differences in absorption of red, blue and green light by chlorophyll. 3.8.5 State that light energy is used to produce ATP, and to split water molecules (photolysis) to form oxygen and hydrogen. 3.8.6 State that ATP and hydrogen (derived from the photolysis of water) are used to fix carbon dioxide to make organic molecules 3.8.7 Explain that the rate of photosynthesis can be measured directly by the production of oxygen or the uptake of carbon dioxide or indirectly by an increase in biomass. 3.8.8 Outline the effects of temperature, light intensity and carbon dioxide concentration on the rate of photosynthesis.