Summary Chemistry of life Biology notes (grade 10, term1)
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Course
Life Sciences
Institution
10th Grade
These notes include: chemistry of life, inorganic and organic compounds, (water, mineral salts, carbohydrates, lipids, proteins, enzymes, nucleic acids and vitamins)
TOPIC 1
L i f e a t t h e M o l e c u l a r, C e l l u l a r a n d T i s s u e L e v e l
Atoms
smallest building blocks of matter • The raw materials needed by plants and animals are
combine to form molecules derived from the environment
Cells • Plants absorb mineral salts from soil and manufacture
basic unit of life nutrients during photosynthesis
composed of simple + complex • Animals obtain nutrients from food eaten
molecules
Compounds Chemistry of life
Two or more elements bonded • Elements consist of identical atoms
together • Compounds = two or more atoms
Molecules combine
Two or more atoms bonded
__________________________________________________________________________________________________________________
Inorganic compounds
• These substances do not contain carbon except for CO2 and carbonates (carbonic
acid - H2CO3)
• e.g. water, mineral salts, carbon dioxide, oxygen, sodium chloride (table salt - NaCl)
1. Water 2. Mineral salts
Essential to both plants and animals and is • Salts of elements like calcium,
used: magnesium, sulphur etc.
• In plants, it is required for • Needed by both plants and animals for
photosynthesis maintenance of cell functions, growth
• In animals it plays an important role in and development
nutrition Macro elements - elements that are
• It provides a uid medium for chemical required in large quantities (Na, K, Ca, P)
reactions Micro elements - elements requires in
• Dissolves substances (solvent) small quantities (Fe, I)
• Controls temperature
• For support and structure
Element Use in plants Use in animals
Sodium (Na) Maintains water balance of cell sap 1. Regulates osmotic balance in body uids
and keeps cells turgid 2. Plays role in functioning of kidneys,
nerves and muscles
Potassium (K) Plays role in opening and closing of Plays a role in the transmission of nerve
stomata impulses
Calcium (Ca) Component of middle lamella of cell 1. Used to build strong teeth and bones
walls 2. Involved in the muscle contraction and
transmission of nerve impulses
Phosphorus (P) 1. Component of cell membranes 1. Component of cell membranes and ATP
and ATP 2. Used to build strong teeth and bones
2. Promotes owering, fruit and root
development
Iron (Fe) Required for chlorophyll synthesis Required to form part of the haemoglobin
molecule
Iodine (I) Not a requirement in higher order Apart of the hormone thyroxin - de ciency
plants results in goitre (swelling of thyroid gland)
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,Use of fertilisers
Plants take up minerals from the soil
1. Fertilisers are used to enrich the soil with minerals like nitrate and phosphate
2. If crops are grown and harvested regularly, soil becomes depleted in minerals. To replace
minerals, dead plants are ploughed back into the soil. The decomposition of these plants will
result in the release of minerals back into the soil
1. Eutrophication - excess of fertiliser results in some of it being drained into rivers and dams
the high, level of nitrates and phosphate results in rapid growth of algae and other water
plants
2. Plants growing deeper, don’t get enough sunlight and will die and rot, these decomposing
plants reduce the O2 and increase the CO2 content of the water causing sh and other aquatic
animals to die
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Organic compounds
• These substances are compounds that contain carbon (except CO2 ) and are usually
bonded with hydrogen
• Some other elements may be also attached (oxygen, nitrogen and phosphorus)
• Examples: Carbohydrates (sugars+starch), lipids (fats+oils), proteins, enzymes, vitamins,
nucleic acid, vinegar, plastics, alcohol, aspirin
• There are more organic compounds than inorganic compounds
• Organic compounds are far more complex in structure than inorganic compounds
• Life is based on organic compounds
Carbohydrates
Examples:
• Starch Composition:
• Sugars • Contain the elements carbon, hydrogen
• Cellulose (In fruit+veg) and oxygen only
• As the word suggests carbon (carbo) and
Consists of 3 groups: water (hydrate), H20
1. Monosaccharides (single sugars) • The ratio of H:O is 2:1
E.g. glucose (C6H12O6)+fructose (fruit sugar) • Building blocks/monomers of carbs is
known as saccharides
Function:
• Important source of energy for plants
2. Disaccarides (double sugars) and animals
E.g. maltose (malt sugar)+sucrose • The monomer glucose is broken down in
(cane sugar) the cell to yield energy
• Food is often stored in the form of
polysaccharides
• Plant store carbohydrates in the form of
starch, animals in glycogen
• Cellulose, a polysaccharide, forms the
cell walls of a plant
3. Polysaccharides (many linked sugars)
E.g. starch, cellulose, glucose
Source:
• Pasta, potatoes
• Bread, rice, our
• Fruit and vegetables
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, Lipids (Fats+Oils)
Composition:
• Contains elements carbon, hydrogen
Source: Examples:
and oxygen
• Butter, margarine, • Fats
• Ratio of H:O is greater than 2:1
oil, nuts • Oils
• Some have phosphorus attached and are
• Fatty meat • Steroids
known as phospholipids
• Certain sh (sardines) • Cholesterol
• Formed when glycerol combines with
fatty acids
• Saturated fats have single bonds in the
fatty acid chains
Cholesterol: • Unsaturated fat has one or more double
• A lipid found in the human body bonds in the fatty acid chains
• Some comes from our diet and some is • Fats are solid at room temp + oils are
formed in the liver liquid at room temp
• It is an important parts of cell membranes
and is needed to make vitamin D
• When in excess it gets deposited on the walls
of blood vessels resulting in the blood Function:
vessels getting blocked, a condition known • Important source of energy (twice as
as Atherosclerosis much as other foods): both plants and
• If the blockage occurs in the blood vessel animals store food in the form of fats oils
supplying blood to the heart muscle the • 1 gram of fat yields twice the energy
person may have a heart attack compared to 1 gram of carbs
• High cholesterol in the body is caused by a • In animals, fat (blubber) under the skin
diet High in saturated fats, being overweight, serves to insulates the body thereby
lack of exercise, a family history of high preventing excessive heat loss
cholesterol and old-age • Most plants store oils in their seeds
• Stored for warmth and future use
There are two types of cholesterol presents in
the body:
1. HDL-cholesterol = good, it is bene cial to the
body
2. LDL-cholesterol = bad, it is harmful to the
body
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, Proteins: Enzymes
Function:
• Required for growth and repair of body
tissues. Muscles are made up of proteins
• Enzymes and hormones are proteins in Composition:
nature. Enzymes speed up chemical reactions • Contain the elements carbon,
well hormones serve as chemical messengers hydrogen, oxygen and nitrogen some,
in the blood other elements like sulphur, phosphorus
• Haemoglobin is a protein found in the blood or iron
that plays an important role in the transport of • Proteins are large complex molecules
oxygen and carbon dioxide which can be broken down into smaller
units (monomers) called amino acids
Enzymes • Proteins are sensitive to temperature and
• Complex protein molecules that speeds up changes in pH
biological reactions in living organisms • High temperature and extremes in pH
• Are biological catalysts since they are not used causes proteins to denature i.e. proteins
up in the chemical reaction lose their shape and function
• Catalyst – speeds up a reaction without taking • Enzymes are very speci c with regard to
part or affecting the reaction the reactions they catalyse. This is to
• Enzymes speed up both anabolic (building of their particular shape
new molecules) and catabolic (breaking down) • Low temperatures render enzymes
reactions inactive
• E.g. photosynthesis, cellular respiration and
digestion of food in animals
Source: Examples:
• Fish, meat, poultry • Albumen
• Eggs, nuts, beans • Enzymes
• Haemoglobin
“Lock and Key Theory” of enzyme action
Enzymes are substrate-speci c which
means that they have a particular shape in
which only a speci c shaped substrate
(molecule in which it acts) will t
1. The surface of the substrate will make
contact with the active site on the surface
of the enzyme molecule
2. An intermediate compound, the
enzyme–substrate complex, is now formed
3. The substrate molecule now changes by
the rearrangement of existing molecules or
the breakdown of the substrate molecule
the changed substrate molecules are now
called the products
• When the reaction is completed the
products move away, the unchanged
enzyme is now free to react with another
substrate molecule.
• The now broken down substrate can move
to other enzymes to be broken down
further.
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