Essay on AQA notes AS

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Biology Unit 1 Notes
3.1.1
Pathogens
Pathogens include bacteria, viruses and fungi
Disease can result from the pathogenic microorganisms penetrating any of an organisms interface with the environment. These interfaces include the digestive and gas-exchange systems and the skin
Digestive system:
Eat/drink food containing pathogens
Most skilled by acidic conditions of the stomach
Some may survive and pass into the intestines where they can invade cells of the gut wall and cause disease
Gas Exchange System:
Breathe in air containing pathogens
Most will be trapped in a layer of mucus lining the lung epithelium
These cells have cilia that beat and move the mucus up the trachea to the mouth where it is removed
Some pathogens reach the alveoli where it can invade cells and cause damage
Skin:
Damage skin
Pathogens on the surface can enter your bloodstream
The blood clots at the area of damage to prevent pathogens from entering
Some may get in before the clot forms
Pathogens can cause diseases by damaging the cells of the cost and by producing toxins
Cell Damage: Pathogens can physically damage host cells by
Rupturing them to release nutrients inside them
Breaking down nutrients inside of the cell to their own use, starves and eventually kills the cell
Replicating inside the cells and bursting them when they are released
Production of Toxins:
Bacteria releases toxins into the body
E.g. Tetanus bacteria produces toxins that blocks the function of certain nerve cells causing muscle spasms

Lifestyle
Lifestyle can affect human health
Risk Factors for Cancer:
Smoking – mouth, throat and lung cancer
Excessive exposure to sunlight – skin cancer
Excessive alcohol intake – liver cancer
Risk Factors for Coronary Heart Disease:
Poor Diet – diet high in saturated fats or salts increase the risk
Smoking
Lack of exercise
Alcohol intake
Changes in lifestyle may also be associated with a reduced risk of contracting these conditions.
Reducing the risk of Cancer and Coronary Heart Disease
Giving up smoking
Avoiding becoming overweight
Reducing salt intake
Reducing intake of cholesterol and saturated fats
Taking regular aerobic exercise
Keeping alcohol consumption within limits
Increase the intake of dietary fibre and antioxidants

3.1.2
The Digestive system

The salivary glands: they secrete saliva that consists of mucus, mineral salts and salivary amylase. Salivary amylase breaks down starch into maltose. Saliva also helps to lubricate food, making it easier to swallow.
The Pancreas: releases pancreatic juice into the duodenum through the pancreatic duct. Pancreatic juice contains amylase, trypsin chymotrypsin and lipase. It also contains sodium hydrogencarbonate which neutralises the acidity of hydrochloric acid from the stomach.
Digestion is the process in which large molecules are hydrolysed by enzymes to produce smaller molecules that can be absorbed and assimilated
Proteins
Proteins have a variety of functions within all living organisms

Condensation and the formation of peptide bonds linking together amino acids to form polypeptides.
Primary Structure- sequence of amino acid in the polypeptide chain
Secondary Structure- polypeptide chain does not remain flat and straight. Hydrogen bonds form between the amino acids in the chain, this makes it automatically coil into an alpha helix or fold into a beta pleated sheet.
Tertiary Structure- the coiled or folded chain of amino acids is often coiled and folded further. More bonds form between the different parts of the polypeptide chain. For proteins made form single polypeptide chain, the tertiary structure forms their final 3D shape.
Quaternary Structure- some proteins are made of several different polypeptide chains held together by bonds. The quaternary structure is the way these polypeptide chains are assembled together. For proteins made from more
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