Biology as Unit 2 Revision

Topics: Blood, Heart, Protein Pages: 15 (3338 words) Published: August 15, 2013
ASBiology and Disease
* Causes of disease
* Pathogens
Disease suggests a malfunction of the body or mind which has an adverse effect on good health For a micro-organism to be considered a pathogen it must
* Gain entry to the host
* Colonise the tissue of the host
* Resist the defences of the host
* Cause damage to the host tissues
Pathogen Infection Disease
Entry pathways
* Gas exchange system
* Digestive system
Natural defences
* Mucous layer
* Production of enzymes
* Stomach acid
Ways of causing disease
* Damaging host tissues
* Producing toxins

* Data and disease
Correlation doesn’t cause causation.

* Lifestyle and health
Risk – A measure of the possibility that damage to health will occur as a result of a given hazard * Probability that a hazardous event will occur
* Consequences of that hazardous event
* Smoking
* Diet
* Obesity
* Sunlight
* Physical activity
* High blood pressure
* High cholesterol

2. Enzymes and the digestive system

* Enzymes and digestion
Oesophagus - transfers food from the mouth to the stomach
Stomach – Stores and digests food
Small intestine – further digestion by enzymes
Large intestine – absorbs water
Rectum – faeces are stored before egestion

Physical breakdown & Chemical breakdown
All chemical breakdown digestion is done by hydrolysis by hydrolase

Carbohydrases – Carbohydrates
Lipases – Lipids
Protease – Proteins
* Carbohydrates – monosaccharide’s
Individual molecule – monomer
Repeating molecules – polymer
Single monomer – monosaccharide
Pair of monomers – disaccharide
Large no. of monomers – polysaccharide

Monosaccharides –
General formula (CH2O)n
Best known monosaccharide – C6H12O6



Test for reducing sugars
(Monosaccharide’s and some Disaccharides)
* Add benedicts reagent
* Heat
* Turns green, yellow, red or orange if present

* Disaccharides
Glucose + Glucose = Maltose
Glucose + Fructose = Sucrose
Glucose + Galactose = Lactose

When disaccharides are formed a molecule of water is released, a condensation reaction, and a glycosidic bond is formed When water is added to a disaccharide it forms two monosaccharides in a hydrolysis reaction

Non reducing sugar test
* Add benedicts reagent
* Heat
* If no colour change..
* Add acid
* Heat
* Add alkaline til neutralised
* Add benedicts reagent
* Heat
* Will turn yellow, green, orange or red if present

* Polysaccharides
Joining lots of monosaccharides together by condensation reaction to produce lots of glycosidic bonds Very large molecules + insoluble
Starch is a polysaccharide

Test for starch
* Add iodine
* Will turn blue/black if present

* Carbohydrate digestion

* Food in the mouth is digested physically by teeth
* Salivary amylase hydrolyses starch to maltose (pH neutral) * Maltose enters stomach where pH denatures the salivary amylase * Food is passed into small intestine where pancreas releases pancreatic amylase hydrolysing any leftover starch * Maltase in small intestine wall hydrolyses maltose into a-glucose Sucrase hydrolyses sucrose = glucose + fructose

Lactase hydrolyses lactose = glucose + galactose

Lactose intolerance - little or no lactase is found in small intestine so lactose is digested minimally which causes nausea, diarrhoea and cramps. * Proteins
Amino acids are basic monomers which make the polymer protein
The joining of amino acids is a condensation reaction and is the – O – H from the carboxyl group ( COOH ) and the – H from the amino group (NH2) The bond between the C – N is a...
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