Grade 12 Biology Notes

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Biology notes for FST Project


* Large molecules sometimes composed of a large number of repeating subunits * Four major classes: Carbohydrates (made of simple sugar/glucose), Lipids (Glycerol and Fatty Acids), Proteins (Amino Acids) and Nucleic Acids (Nucleotides) * Condensation reaction/dehydration synthesis: a reaction that creates a covalent bond between two interacting subunits. Removal of H from one functional group and an OH from the other, and the H come together to form a water molecule (H2O). Anabolic process because it results in the construction of large molecules from smaller subunits * Hydrolysis reaction: a catabolic process in which a water molecule is used to break a covalent bond. AKA the opposite of condensation, where one H goes to one atom and the OH goes to the other * Enzymes are biological catalysts, and catalysts are chemicals that speed up chemical reactions without being consumed in the process

* Most common organic material among earth
* Produced by plants and algae through photosynthesis
* Used by organisms as sources of energy, as building materials, and as cell surface markers for cell-to-cell identification and communication * Carbon, hydrogen and oxygen in a 1:2:1 ratio (CH20)

* Monosaccharides (simple sugars), oligosaccharides, and polysaccharides * Monosaccharides can be distinguished by the carbonyl group they possess- aldehyde or ketone- and the number of atoms in their carbon backbone * Glyceraldehyde: 3 carbons (triose) with aldehyde group (R- CHO) * Ribose: 5 carbons, component of RNA

* Oligosaccharides are sugars containing two or three simple sugars attached by glycosidic linkages * These bonds are condensation reactions, and transports sugars from one part of the cell to another * Polysaccharides are monosaccharide polymers composed of several hundreds/thousands monosaccharides held together by glycosidic linkages * Used for energy storage ands structural support

* Starch and glycogen are for storage, cellulose and chitin are structural * Sometimes plants produce too much glucose than needed, so enzymes in the chloroplast link excess glucose molecules together to form starch (storage) * Starch is a mixture of two different polysaccharides, amylose and amylopectin

* Hydrophobic molecules composed of carbon, hydrogen and oxygen * Fewer polar OH bonds and more non polar CH bonds than carbohydrates * They are insoluble in water but soluble in non polar substances * Lipids are used for storing energy, building membranes and other cell parts, and used as chemical signaling molecules * They can be divided into four families: fats, phospholipids, steroids and waxes * Triglycerides are forms of fat that carbohydrates (Excess) are stored in * Triglycerides have three fatty acids attached to one glycerol * A glycerol is a three carbon alcohol containing a hydroxyl (OH) group attached to each carbon * Fatty acids are long hydrocarbon chains containing a single carboxyl group (COOH) at one end * The OH from each carbon on the glycerol attached to the OH on the end of each fatty acid, creating a COC bond and H2O (COC linkage is an ester linkage) * Membranes of cells are composed of phospholipids, which are composed of a glycerol which is attached to two fatty acids and polar phosphate group * When in water, the phospholipids form a sphere called a micelle. The heads dissolve in the water and the tails mix together in the center of the sphere * Membranes also contain sterols/steroids, which are compact hydrophobic molecules containing four fused hydrocarbon rings and several functional groups * An example is cholesterol- in high concentrations and a diet high in saturated fats (single bonds between carbons) have been linked to the development of atherosclerosis (where plaque...
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