Topic 3: The Chemistry Of Life

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3.1.1 What are the most frequently occuring chemical elements in living things.

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Carbon, hydrogen and oxygen

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3.1.2 What are the other elements needed by living organisms

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Sulfur, calcium, phosphorus, ion and sodium

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3.1.3 What are the roles of calcium, sulphur, phosphorus, iron and sodium?

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Calcium- Regulate transciption and other proccesses. It is nessecary for bone and tooth formation, blood clotting and nerve impulse transmission.
Phosphorus- A part of DNA molecules and par of the phosphate groups in ATP. Also to balance acid and base concentrations in body.
Iron- A part of haemogloblin, a molecule needed to carry oxygen in the blood (carrying electron transport for aerobic cell respiration).
Sodium- balances both water in the body and acid/base concentration. It raises the solute concentration which causes water to enter by osmosis.

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3.1.5 How are the properties of water signficant to living organisms?

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Water is transparent - allows light to filter into ocean. This allows aquatic plants to absorb light and perform photosynthesis.
Water is cohesive- It binds to itself due to the polarity of the water molecule. They bind together by hydrogen bonds. This property allows for transport of water against gravity in plants.
Water is an universal solvent- capable of disolving many organic and inorganic particles. All reactions in cell myst take place in aqueous solution.
Water's polarity also inhibits movement of its molecules. Since all the molecules are connected, they cannot freely move about as other nonpolar molecules.

Water has a thermal properties that include heat capacity, boiling/freezing points and cooling effect of evaporation.

Heat is thus restriced and so water has a high specific heat(it must absorb large amounts of energy in order to change states because of the strengths of the hydrogen bonds) Meaning that water can serve as an temperature insulator and a provides suitable habitat.

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3.1.6 What are the significance of water as a coolant and transport medium for metabolic reactions and transport for living organisms .

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Water's high specific heat allows it to absorb large amount of energy. eg our bodies use water to form sweat to lower body temperature. The sweat absorbs a large amount of heat, and then evaporates, carrying the heat away.

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3.2.1 What is organic and inorganic compounds

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Compouds containing carbon that are found in living organisms, except carbonates, hydrogencarbonates and oxides.
Inorganic compounds do not contain carbon

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3.2.3 What are 3 examples of mono/di/poly- saccharides?

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Mono- glucose, galactose and fructose
Di- Maltose, sucrose and lactose
Poly- Starch, glycogen and cellulose

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3.2.5 What is the role of condensation and hydrolysis in the relationship between mono/di/poly saccharides ; fatty acids, glycerol and glycerides; amino acids, dipeptides and polypeptides.

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For monosaccharides, fatty acids and amino acids to become disaccharides,glycerol and dipeptides, condensation reaction needs to occur.
When these monomers covalently bond, a water molecule is released; this is a condensation reaction. When many monos join together through condensation, polys result
In a hydrolysis reaction, the addiction of water molecule breaks down the covalent bonds and polys break down into monos.

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3.2.6 What are the three functions of lipids?

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Insulators (recuduces heat loss), hormones and long term energy storage( fat in human and oil in plants) and buoyancy so animals can float in water .

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3.2.7 What is the usage of carbohydrates compared to lipids in energy storage?

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Carbohydrates are used for short term storage wheras lipids are used in long term storage.
Carbohydrates are soluble in water therefore easily digested unlike lipids which also makes it more difficult to transport. But because of that it decreases the problems within the cells

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3.2.4 What is the function of glucose, lactose ad glycogen in animals

and fructose, sucrose and cellulose in plants

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In animals glucose is used as an energy source and lactose is the sugar found in milk (new borns) and glycogen is short term energy source stored in muscles and liver

Plants- fructose; makes the fruits taste sweet which attracts animals to encourage seed dispersion.
sucrose- energy source
cellulose- makes plant cell wall strong

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3.3.1 What is a DNA nucleotide structure made up of?

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Sugar deoxyribose, a base and a phosphate group

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3.3.2 What are the four bases

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adenine, guanine, thymine and cytosine

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3.3.3 How are Dna nucleotides linked together by ?

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By covalent bonds into a single strand

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3.3.4 How is DNA double helix formed using complementary base pairing and hydrogen bonds.

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DNA is made up of two nucleotide strands. The sugar forms a covalent bond with the phosphate group of another.

The two hydrogen bonds are found between the bases of the two strands of nucleotides.

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3.4.1 Explain DNA replication.

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It involves the unwinding of the polymerase strands by enzyme helicase.When the two DNA strands are split apart new DNA is made by attaching free nucleotides to the orignal strand(template) by base pairing rules with the help of enzyme DNA polymerase. The process results in two identical DNA strands produced from one.

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3.4.2 What is the significance of complementary base pairing in conservation of base sequence?

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As DNA replication is semi- conservative (one old and one new strand = new DNA molecule) the complementary base pairing allows the two DNA molecules to be identical to each other and new ones are formed complementary to template strands but identical to the other template.

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3.4.3 DNA replication is....

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Semi-consevative

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3.5.1 What are the differences between the structure of RNA and DNA?

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DNA is composed of a Double strand forming a helix whilst RNA is only composed of one strand
DNA contains a deoxyribose sugar, in RNA its ribose.
When complementary bases to adenine get attatched, in DNA, it is replaced by thymine but in RNA it is replaced by uracil.

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3.5.2 What happens in DNA transcription?

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DNA transcription is the formation of an RNA strand which is complementary to the DNA strand.
First, DNA double helix uncoils and free RNA nucleotides start to form RNA strand by suing DNA strands as template. This is done through complementary base pairing.
However in RNA, the base THYMINE is replaced by URACIL.
RNA polymerse is the enzyme involved in formation of RNA strand and the uncoiling.
The RNA then elongates and separates from DNA. The DNA then reform a double helix.
The strand of RNA formed is called messenger RNA.

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3.53 What is the genetic code

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A triplet of bases forming a codon. Each codon codes for a particular amino acide.
The genetic code is the codons within DNA and RNA, composed of triplets of bases which lead to protein synthesis.

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3.5.4 What happens in translation before polypeptide formation?

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Translation is the process where proteins are synthesized.
It uses ribosmes, mRNA which is composed of codons and tRNA which has a triplet of bases called anticodon.
During the first stage, the mRNA binds to the small subunit of the ribosome.
The tRNA has a specific amino acid attached to them that corresponds with the anticodon. A tRNA molecule will bind to the ribosome if anticodon matches the codon on the mRNA through complementary base pairing. ANother tRNA molecule then bonds. (Two trna molecules can bind at once)
Then the 2 aminoacid on the 2trna molecules form a peptide bond.
The first tRNA then detaches from the ribsome and second one takes its place. The ribosome move along the mRNA to the next codon so that another tRNA can bind. Again, a peptide bond is formed between the amino acids and this process continues. This forms a polypeptide chain.

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3.5.5 What is the relationship between one gene and one polypeptide?

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A polypeptide is formed by amino acids linking together through peptide bonds. ( there are 20 so a wide range is possible)
Genesstore the information required for making polypeptides(many amino acids) which is stored in codons. The sequence of bases in these codons from that gene codes for the sequence of amino acids in a polypeptide. The information and sequence of the genes is decoded during transcription and translation leading to protein synthesis.

(depends on your inherited genes(many DNA, this will put the bases/codons in order to produce the polypeptide you need)

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3.6.1 What is an enzyme and its active site?

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Enzymes are globular protein that act as catalyst to enhance chemical reactions.
Active sites are the region on the surface of an enzyme to which the substrates bind and catalyses that chemical reaction involving that subtrate.

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3.6.2 What is the enzyme-substrate specifity?

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The active site of an enzyme is very specific to its substrates as it has a precise shape. This is because enzymes only catalyse certain reactions as only a number of substrates fit into that precised shaped active site.

For enzymes to catalyse subtrates it needs to be chemically attracted and physically able to fit into the active site.
This makes the enzyme very specific to its substrate. It can be compared to a lock (enzyme) and the key(substrate)

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3.6.3 a) What effects do temperature have on enzyme activities.

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Enzyme activity increases with an increase in temperature. This is due to the molecules moving faster and colliding together more often. However if the temp gets too high the enzymes will denature. This is due to the heat causing bizare vibration hence destroying its struture by breaking the bonds in the enzymes.

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3.6.3 b) What effects do pH and substrate concentration on enzyme activites?

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Enzymes have an optimum pH where they work most effectively. As the pH level diverges from the optimum, enzyme activity decreases.

Enzyme activity increases with an increase in substrate conentration. This is due to the increase in random collisions between the substrate and the active site. But at some point all the active sites will be taken up so the substrate concentration (key) will have no more effect.

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3.6.4 What is denaturation?

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It is the changing of the structure of an enzyme that it can no longer carry out functions.

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3.6.5 What is the use of lactase in the production of lactose-free milk?

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Lactose is the sugar found in milk.

It can be broken down by lactase into glucose and galactose.

Some people lack this enzyme and so they cannot break down lactose therefore have to drnk lactose-free milk.

This milk can be made in two ways.
a) Adding the enzyme lactase to the milk so that the milk contains the enzyme.
b) immobilizing the enzyme o a surgace or in beads of a porous material. The milk is then allowed to flow past the beads or surface and hence avoids having the lactose in the milk.

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3.7.1 What is cell respiration?

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It is the controlled release of energy from an organic compound to form ATP.

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3.7.2 What happens in cell respiration?

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Glucose in the cytoplasm is broken down by glycosis into pyruvate a small yield of ATP.

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3.7.3 What happens during anaerobic cell respiration?

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The pyruvate stays in the cytoplasm in humans and is converted into lactate which is then removed from the cell.
In yeast, the pyruvate however is converted into carbon dioxide and ethanol.
No ATP is produced.

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3.7.4 What happens during aerobic cell respiration?

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If oxygen is available, the pyruvate is take into the mitochondria and broken down into carbon dioxide and water. Then, a huge amount of ATP will be released.

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3.8.1 What conversion occurs in photosynthesis?

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Light energy into chemical energy

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3.8.2 What is the light from sun composed of ?

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A range of wavelengthes (colours)

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3.8.3 What is the main photosynthetic pigment?

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Chorophyll

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3.8.4 What is the differences in absorption of red, blue and green light by chlorophyll?

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Chlorophyll can absorb red and blue light more than green. It cannot absorb freen light and so reflects it making leaves look green.

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3.8.5 What is light energy used for?

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To produce ATP and to split water molecules to form oxygen and hydrogen.

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3.8.6 What are the usage of ATP and hydrogen ( from photolysis of water)

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Used to fix carbon dioxide to make organic molecules.

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3.8.7 How can the rate of photosynthesis be measured?

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It can be measured in a number of ways as it produces oxygen, has an increase in biomass and the uptake of carbon dioxide.
EG: aquatic plants release oxygen bubbles during photosynthesis and so this can be collected and measured.
The uptake of carbon dioxide is more difficult to measure so it is done indirectly.
EG: When carbon dioxide is absorbed by water, the pH of the water rises and so this can be measured with the pH indicators/pH meters.
With Biomass, if batches of plants are harvested at a series of times and the biomass of these batches are calculated, the rate increase in biomass gives and indirect measure of te rate of photosynthesis in these plants.

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3.8.8 What are the effects on the rate of photosynthesis?

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As temperature increases, the rate of photosynthesis increases more and more until optimum temp is reached. If above op temp, the rate decreases rapidly

Light intensity increases photosynthesis until a certain point. After reeaching a plateau at high light, it does not increase any more. At low/ medium light intensity, the rate of photosynthesis is direcly proportional.
The increase of concentration of carbon dioxide increases the rate as well. There will be no photosynthesis at a very low level but during high levels, it will reach a plateau