Biology Unit 1

Causes of Disease

Pathogens are disease causing microorganisms that cause disease by producing toxins and damaging cells.

They enter the body through the respiratory system, the reproductive system, the digestive system and the skin.

Enzymes and the digestive system

Assimilation is when the break down products of digestion are used in processes within the body.

Benedict's Test is for reducing sugars and if positive turns from blue to an orange-brown colour.

To test for a non-reducing sugar, it is broken down into it's monosaccharide components and then the Benedict's test is used. 

• Glucose + Glucose ---> Maltose + Water
• Glucose + Fructose ---> Sucrose + Water
• Glucose + Galactose ---> Lactose + Water

Monosaccharides are formed by a condensation reaction and are held together by glycosidic bonds. 

To test for starch, iodine is added and it turns blue-black if positive.

Starch digestion :

• Food is broken up in the mouth to give it a larger surface area.
• It mixes with salivary amylase beginning hydrolysis of starch into maltose.
• It enters the stomach where the acidic conditions denature the enzyme to prevent further hydrolysis. 
• It enters the small intestine where it mixes with pancreatic amylase for further hydrolysis of remaining maltose.
• Muscles in the intestinal wall push the food along the small intestine and the epithelium lining produces maltase, hydrolysing the maltose into alpha-glucose.

People who are lactose intolerant don't produce enough lactase. Once the undigested lactose reaches the small intestine, the water potential of the lumen gets more negative so water floods into the lumen by osmosis. This means there is excess water and leads to osmosis.

Proteins :

Proteins are formed from amino acids by a condensation reaction, and are held together by peptide bonds.

• Primary structure - sequence of amino acids
• Secondary structure - alpha-helix of the polypeptide chains
• Tertiary structure - bending and twisting of the polypeptide chains and maintained by hydrogen bonds and disulfide bridges.
• Quaternary structure - combination of different polypeptide chains

The Biuret test is a test for proteins and turns lilac if positive.

Enzyme Action :

Temperature - increases because of an increase in kinetic energy until it gets too hot where it denatures enzyme by breaking hydrogen bonds, altering the tertiary structure and the shape of the active site.

Concentration - directly proportional until it reaches Vmax where all the active sites are already binded to substrate.

pH - causes the hydrogen bonds to break and changes it's tertiary structure.

Competitive inhibitors have a similar shape to the substrate and are complementary of the enzyme so it binds to the active site.

Non-competitive inhibitors attach to a different part of the enzyme, changing the shape of the enzyme and active site.

Cells and movement in and out of them

magnification = size of image / size of object

Magnification is the measure of enlargement.

Resolution is the ability to define two points that are very close to each other.

Cell Fractionation :

• Cells are homogenised to release organelles.
• They are centrifuged.
• Heaviest organelles form…