AS Biology (AQA)

What is a pathogen, how do they enter the body and how do they cause disease?

A pathogen is a bacteria, fungi or virus. They can enter the body through cuts in the skin, the gas exchange system and the digestive system. They cause damage by producing toxins or damaging the host tissue.

What is the difference between cause and correlation?

When a graph shows a cause then there must be no other factors which could change the results produced during an experiment except the independent variable.

A graph will show a correlation if there is a link between the dependant variable and independent variable but there are other factors which may effect the results.

An example of a correlative relationship:

Smoking can significantly decrease life expectancy.

This statement shows that there is a link between smoking and decreased life expectancy however there are other factors which may affect life expectancy such as genes and lack of exercise.

What is risk, how do we measure it?

Risk is the measure of probability that health problems will occur as a result of a given hazard. Risk is measured in percentage and provided within a time frame.

The chance of dying within the next month is 90%.

Give the structure and function of the main parts of the digestive system.

• Salivary Glands - Produces Amylase, begins the digestion of starch
• Oesophagus - Peristalsis, moves food into stomach
• Pancreas - Pancreatic juices, secretes enzymes, Amylase, Protease, Lipase.
• Stomach - Peristalsis, enzymes (Protease) begin digestion of substances (protein)
• Small Intestine - Villi & Microvilli increase surface area for digestion, enzymes continue to digest foods
• Large Intestine - Excess water is removed and faeces is produced
• Rectum - Faeces is stored

How does the digestive system mechanically break down food?

Teeth grind food down and saliva mixes with it to form a pulp. Food is passed into the stomach which breaks down the food further via peristalsis - the contracting of the stomach wall.

What is the role of Carbohydrases, Lipases and Proteases?

Carbohydrases, lipases and proteases break down carbohydrates, fats and proteins via hydrolysis into monosaccharides, fatty acids and glycerol and amino acids respectively.

Biological molecules such as carbohydrates and proteins are polymers.

Carbohydrates are long chains of monosaccharides called polysaccharides.

Proteins are long chains of amino acids, they have primary, secondary tertiary and quaternary structures.

What are the names of some monosaccarides, and what is the simplified structure of Alpha glucose?

Monosaccarides:

• Glucose
• Galactose
• Fructose

Alpha Glucose:

                    | ________O

         H \      /                   \      / H

               \ /                        \ /

              /   \                      /   \

      OH /       \_________/       \ OH