Nature of science:
Falsification of theories—the artificial synthesis of urea helped to falsify vitalism. (1.9)
Understandings:
Applications and skills:
The ability of ions and other molecules to dissolve in water is due to polarity. For example, in the illustration above sodium chloride is shown in its crystalline form and dissolved in water.
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Adhesive properties: the dipolarity of water molecules make them adhere to surface that are polar example: adhesive forces between water and cellulose cell walls in the leaf causes water to be drawn out of xylem vessels keeping the cell wall moist.
https://www.youtube.com/watch?v=ASLUY2U1M-8
All organic molecules contain carbon except carbon dioxide
type of organic molecule |
subtypes |
Examples |
Carbohydrates |
Monosaccharides |
Glucose, fructose, galactose |
Disaccharides |
Maltose, lactose, sucrose |
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Polysaccharides |
Starch , glycogen, cellulose |
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Proteins |
Enzymes, antibodies |
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Lipids |
Phospholipids , triglycerides |
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Nucleic acids |
DNA, RNA |
Carbohydrates: all contain carbon, oxygen and hydrogen atoms common formula C x( H2O)y where x =y or variable numbers
• Monosaccharides (mono means single) Ø Are simple sugars Ø Have a general formula (CH2O)n Ø value of n is any number from 3-7 Ø According to the value of n they are grouped as trioses where n=3 tetroses where n=4 pentoses where n=5 hexoses where n=6 heptoses where n=7 Examples of triose: early product of photosynthesis pentose :ribose and deoxyribose hexose : glucose, fructose and galactose |
• Disaccharides Made up of 2 monosaccharides Examples • 2 Glucose molecules make up Maltose (malt sugar) • A glucose and a fructose make up Sucrose (table sugar) • A glucose and a galactose make up Lactose (milk sugar) |
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Glucose(C6H12O6)
The structure of glucose
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Glucose is the major source of energy. Each gram of glucose yields about 16kJ of energy when fully broken down during respiration |
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Glucose is soluble and dissolved in blood plasma is transported around the body |
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Lactose is the main sugar in milk |
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In plants sugar is transported as sucrose in phloem |
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Maltose is produced in many germinating seeds by the breakdown of amylose ( a kind of starch) |
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Ribose and deoxyribose are constituents of genetic material in RNA and DNArespectively |
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Condensation reaction involves removal of a water molecule |
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The linkage formed between monosaccharide residues due to this is called glycosidic bond/linkage |
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The condensation reaction is brought about by an enzyme |
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Disaccharide can be broken down into constituent monosaccharides by hydrolysis. This is the reverse of condensation where the splitting of glycosidic bond occurs, catalysed by an enzyme |
The water molecule comes out from the OH group of C1 and C4.In Beta glucose the OH of C1 is on the top.
Starch |
It is a compact molecule making it ideal for a storage product. In flowering plants they are present in plastids. |
Glycogen Much more branched as it has many more 1-6 glycosidic bonds |
Storage by hydrolysis more rapidly than starch. compound particularly abundant in liver and muscle cells. Breaks down |
Cellulose |
Tough ,completely permeable. Major constituent of plant cell wall. Cannot be hydrolysed easily. Humans do not have cellulase to digest cellulose. Gut microorganisms of cow produce the enzyme. |
STARCH is comprised of alpha glucose units.
Starch is of two types : amylose(1-4 glycosidic bonds) and amylopectin (both 1-4 and 1-6 glycosidic bonds).
The long chains are coiled into helix.
Because of its structure starch is compact and ideal for storage. In flowering plants starch granules are present in plastids.
CELLULOSE is made up of beta subunits
(1-4 glycosidic bonds).
Orientation of glucose units alternates which makes the polymer straight. The OH in C1 and C4 point in opposite directions. To allow condensation each unit has to be positioned at 180 degrees to the previous one.
Groups of cellulose molecules are arranged in parallel with hydrogen bonds forming crosslinks. Cellulose is found in the form of microfibrils that make up the main structural molecules of the plant cell wall.
Glycogen was discovered by Claude Bernard in 1857,
R GROUP
Hydrolysis is the reverse of condensation
A protein is a large polypeptide, or several polypeptides joined together, and having a specific shape and function. Proteins have many important biological functions.
Types of protein |
Function |
Enzymes |
Biological catalysts that control biochemical reactions :example amylase that catalyses the digestion of starch. Digestion of food and synthesis of important molecules occur in living cells only in the presence of enzymes |
Structural proteins |
Form the part of the body of an organism. For example the silk of spiders ; collagen in tendons and ligaments; keratin the major component of hair |
Signal proteins |
Carry messages around the body: insulin , a hormone involved in controlling glucose level in the blood |
Contractile proteins |
Actin and myosin are muscle proteins that help the muscle to contract thereby bringing about movements |
Storage proteins |
Albumen , the protein store that forms the egg white |
Defensive proteins |
Blood antibodies that fight infections |
Transport proteins |
Hemoglobin , carrying oxygen in blood |
Proteins perform a huge variety of functions in wide range of environments
Ice fish living in the waters of the
Antarctic have proteins designed to function at sub-zero temperature
THE SHAPE OF A PROTEIN IS DETERMINED BY FOUR LEVELS OF STRUCTURE |
PRIMARY STRUCTURE
SECONDARY STRUCTURE
http://www.youtube.com/watch?v=lijQ3a8yUYQ&feature=related
http://www.youtube.com/watch?v=8-RoBZVbHOU
An α helix is generated when a single polypeptide chain twists around on itself to form a rigid cylinder. A hydrogen bond is made at regular intervals, linking the C=O of one peptide bond to the N–H of another. This gives rise to a regular helix with a complete turn every 3.6 amino acids.
Methionine, Cysteine(Cys, CH2SH)
TERTIARY STRUCTURE OF PROTEIN
Breaking down tertiary structure : DENATURATION of enzymes
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A number of tertiary polypeptides joined together. |
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Haemoglobin is a quaternary structure. |
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It is composed of four different polypeptide chains. |
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Each chain forms a tertiary structure called a haem group. |
Proteins are classified into 2 main groups on basis of tertiary structure
COLLAGEN is a fibrous protein
Collagen is distinct from other proteins in that the molecule comprises three polypeptide chains which form a unique triple-helical structure
Polar and non polar amino acids in protein structures.
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Those sections of the molecule that contain polar amino acids are hydrophilic and can exist in contact with water. |
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Polar amino acids allow the positioning of proteins on the external and internal surface of a cell membrane. Both cytoplasm and tissue fluid are water based regions. |
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The non-polar amino acids allow the same protein to site within the phospholipid bilayer. |
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The lining of the channel itself will be of polar amino acids to allow the diffusion of charged molecules and ions. |
Cis- unsaturated fatty acids are not good at packing together therefore they have lower melting point. Trans fatty acids do not bend at double bond and
have higher melting point. They are produced by hydrogenation of vegetable oil or fish oil and present in margarine and other processed foods.
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