Biology: Biological Molecules

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Intro to Biochemistry

Metabolism is the sum total of all chemical reactions taking place in an organism.

Catabolic Reaction: BREAKING large molecules into smaller molecules.

Anabolic Reaction: BUILDING larger molecules from smaller molecules.

Condensation Reaction: When monomers are linked together. Causing water to be released and a covalent bond is formed.

Hydrolysis Reaction: When a large molecule is split into monomers, causing a water molecule to be used and a covalent bond is broken. 

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Carbohydrates: Energy storage & supply

- Soluble in water, sweet tasting and forms crystals

Alpha: OH is below.         Beta: OH is above.      =They differ in properties. 

A glycosidic bond is the covalent bond that occurs between two monosaccharides join to make a disaccharide. (water molecule is released).

Animals/Plants can only break down a-glucose (used for respiration).                                 A polymer of a-glucose is maltose, this occuring over and over = amylose

The glycosidic bond between 3 glucose occurs is called a 1,4 glycosidic bond. 

Amylose:  Long chains coil due to shape of glucose & glycosidic bonds. Very compact. Not water soluble. 

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Carbohydrates Structure

Alpha Glucose                                                     Beta Glucose

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Carbohydrates as Energy storage

Starch (plants)

- long, chained amylose and branched amylopectin. 

- stored in chloroplast. 

- plants store alot of starch grains which are broken to glucose = respiration.

Glycogen (animals)

- large branched molecule that can be broken

- 1,4 link glucose cgains are shorter and more branched

- very compact

- forms glycogen granules

- found in liver & muscle cells

Both do not dissolve in water, the water potential in a cell is not affected. 

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Cellulose uses B-glucose: chains are long and straight. 

- Hydrogen and 1,4- glycosidic bonds.

- Linear structure and non helical.

- 60-70 cross links.

- Found in plant cells walls (provides strength & structure).

- The arrangement of macrofibrils allow water to move through the cell walles without bursting.

The cross links form bundles (microfibrils) and when more hydrogen bonds hold microfibrils to form (macrofibrils) 

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- structure, membrane carriers, enzymes, hormones and antibodies.

 Animals cannot make amino acids, so they are obtained through the diet. Amino groups are removed by deamination which occurs in the liver, otherwise they become toxic

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Various Structures

Primary structure: Specific sequence of amino acids that make up a protein.

Secondary structure: formed when the chain of amino acids coil to form an alpha helix.

Tertiary structure: when the coils or pleats themselves coil or fold with straight run of amino acids between them. (Disulfide bonds, Ionic bonds, Hydrogen bonds, Hydrophobic & Hydrophillic bonds) 

Quarternary structure: when some proteins are made of more than one polypeptide subunit joined together. 

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Protein structure

Globular proteins                                Fibrous proteins

- rolls up to form balls                                                  - forms fibres

- usually soluble in water                                             - usually insoluble in water

- metabolic roles                                                        - structural roles

- hydrophobic inwards, hydrophillic outside                  - collagen tends to be fibrous

- enzymes tend to be globular

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Proteins in Action

Haemoglobin (TRANSPORT) 

Consists of 4 sub-units (2 A & 2 B)

Form a water soluble globular protein

Contains a prosthetic group (The Haem group)

Alpha helix structure


Fibrous protein- 3 polypeptide chains

Hydrogen Bonds give structure length

Contains cross links

Cross links are staggered= collagen fibril

Provides strength, found in artery walls & bones

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Saturated fats = single bonds = unhealthy (mostly in animals)

Unsaturated fats = double bond = healthy (C=C changes the molecule shape)

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