Assingment

Question 1

Aim

Answer 1

The aim of this investigation is to investigate the effect of changing the respiratory substrate on the process of fermentation

Question 2

Underlying Biology (aerobic respiration)

Answer 2

Aerobic respiration is the process by which oxygen and glucose is broken down into carbon dioxide and water:

Glucose + oxygen ➡️ carbon dioxide + water + energy

(word equation for aerobic respiration)

Question 3

Underlying Biology (aerobic respiration 2)

Answer 3

The first stage takes place in the cytoplasm where the glucose is broken down into 2x pyruvate and enough energy is produced to make 2 ATP molecules

If oxygen is present, the second stage then occurs. Stage 2 takes place in the mitochondria (the site of aerobic respiration) where the 2x pyruvate is further broken down into carbon dioxide and water and enough energy is produced to make lots of ATP

Muscle cells require more ATP as the energy is used for muscle cell contraction, cell division, protein synthesis and transmission of nerve impulses

Question 4

Underlying Biology (fermentation)

Answer 4

Fermentation is what occurs when there is an absence of oxygen at stage 2 of respiration

It takes place in the cytoplasm where glucose is broken down into 2x pyruvate and enough energy is produced to make 2 ATP

During fermentation of animal cells, when there is an absence of oxygen the pyruvate that has been made is converted into lactate (sometimes referred to as lactic acid). This is when your muscles are using up oxygen faster than it can be supplied by your circulatory system and lungs. A build up of lactate in muscles can cause fatigue and this creates a lack of oxygen in cells. When oxygen is present it means there is no longer a lack of it and the lactate is converted back into pyruvate, it’s a reversible process

However during the fermentation of plant and yeast cells the same 2x pyruvate is made but this time, due to the absence of oxygen, it is converted into carbon dioxide and ethanol and no more energy is produced, this process is irreversible as carbon dioxide diffuses away

Question 5

Method

Answer 5

I weighed flour into a beaker then stirred in warm water, yeast and sugar. I then marked the current height of the dough on the beaker and covered it with film. After 30 minutes I then marked the height of the dough again and calculated the difference in height. I repeated this process with the other sugar types