Biology Unit 3 Notes

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Biol GOD Notes.
First Edition
1 L. Leong 2012

Chapter 1: Molecules of Life
Cell Theory
∝ All living things are composed of cells and the products of cells ∝ Cells are the basic functional unit of life ∝ All cells arise from pre-existing cells

Living Things
Unicellular: consisting of one cell Multicellular: composed of many cells ∝ All living things: grow and develop, regulate metabolic processes, move, respond to stimuli, reproduce AUTOTROPHS: manufacture their own organic carbon compounds from inorganic material ‒ Phototrophic: use light as an energy source for the production of organic molecules eg. All green (chlorophyll-containing) plants are phototrophic ‒ Chemosynthetic: derive energy from chemicals for use in the manufacture of organic molecules eg. some bacteria HETEROTROPHS: rely on consuming an external source of organic molecules eg. All animals, fungi and most bacteria

Chemicals of Life
All cells (therefore all living things) are composed of chemicals, which fall into two different categories: » » Organic chemicals: Molecules that contain carbon in a complex form eg. glucose Inorganic chemicals: do not contain carbon in a complex form eg. Water, carbon dioxide

Maintaining a Constant pH in the Body It is vital to keep blood pH within its narrow limits. Deviations from the normal range are corrected using a buffering system. CO₂ + H₂O H₂CO₃ HCO₃⁻ + H⁺

Bicarbonate ions and hydrogen ions react with acids/bases in the bloodstream to maintain a constant pH.


L. Leong 2012

The Water Molecule
∝ Versatile solvent due to polarity, molecules held together by hydrogen bonds ∝ Substances dissolve in water due to positive ion attracted negative oxygen, and vice versa, which in enough to dissociate the substance » Hydrophilic: substances that readily dissolve in water (polar)  » Hydrophobic: substances that tend to be insoluable in water (non-polar) 

Biomacromolecules (a.k.a. organic molecules) Carbohydrates
∝ Chemicals containing carbon, hydrogen and oxygen; Formula: (CH₂O)n Simple Carbohydrates ∝ Simple Carbohydrates includes monosaccharides and dissaccharides ∝ Monosaccharide (sugar molecule): 3-7 carbon atoms, water soluble ∝ Most important is glucose, an energy source in animals and plants (C₆H₁₂O₆). Other include: fructose, galactose, ribose ∝ Contain rings of carbon atoms bonded covalently to oxygen and hydrogen atoms. ∝ Dissaccharide (two sugars): forms by condensation reaction, joined by glycosidic bond eg. Sucrose (form carbohydrates are transported in plants) Complex Carbohydrates ∝ Polysaccharides: mostly consist of glucose, difference in bonding and structure give different shape and properties ∝ Glycogen: highly branched chains of glucose molecules used as storage molecule in animals. Storage in the liver (100g), muscle tissue (300g), excess as fat ∝ Starch: straight chains of glucose molecules, spiral-shaped, used as a storage molecule in plants. Ideal due to insoluability, no osmatic action, readily converted back into sugar and transported where needed ∝ Cellulose: long, unbranched chain of glucose molecules, used as structural component in plants ie. forms plant cell walls. Contains strong cross-links that humans cannot breakdown. ∝ Chitin: forms basis of insect exoskeletons and cell walls of some fungi. Composed of modified glucose molecules.


L. Leong 2012

∝ All contain C, H, O, N, some contain S & P Amino Acids ∝ There are 20 naturally occurring amino acids (humans rely on food for 9) ∝ All amino acids contain an amino group (NH₂) and carboxylic acid group (COOH). ∝ R-group varies in each of the 20 amino acids ∝ Dipeptide: two amino acids, held together by peptide bond, by condensation reaction Peptides ∝ Polypeptides are chains of amino acids formed by condensation polymerisation

Structure and Shape of Proteins
Primary Structure ∝ Amino acid sequence (genetic material decides the sequence of amino acids) Secondary Structure ∝ Folding of the...
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