Biology is Too Hard
And the Mark Schemes are never clear
Respiration & ATP
Why do organisms need energy?
This may crop up as an essay question - so make sure you can name the different processes that require ATP/energy.
1) Metabolism - some reactions in living organims require energy at some point - where are the points in certain reactions that require ATP? 1st stage of glycolysis where glucose is phosphorylated to glucose-6-phosphate (substrate level phosphorylation). Find some examples of this.
2) Movement - Energy is needed for movement - can you explain the role of ATP in bringing about movement in the body? You need to be going for the involvement of ATP in muscle contraction.
3) Active transport - describe it fully and the involvement of ATP.
4) Cell division
5) Production of proteins
6) Maintenance of body temperature
The name Adenosine Tri-phosphate means that this molecule is made of three distinct parts. An adenine molecule - same as the one found in DNA and RNA. A ribose sugar molecule same as the one found in an RNA molecule. Ribose and adenine together form a molecule called a NUCLEOSIDE. When one phosphate group is added it becomes a NUCLEOTIDE - Adenosine monophosphate. When two more phosphate groups are added it becomes ATP or adenosine tri-phosphate. The bonds between each phosphate group are unstable and so have a low activation energy - when they are broken they release loads of energy.
ATP is constantly being formed from ADP, this involves the addition of a phosphate molecule. This is known as phosphorylation and there are three different types.
1) Photophosphorylation - which takes place in the light dependent stage of photosynthesis.
2) Oxidative phosphorylation - where ATP is made from ADP in the final stage of respiration.
3) substrate level phosphorylation - when phospahte groups are transferred from donor molecules to make ATP from ADP. This happens in the final stage of glycolysis where pyruvate is made.
Overview of Respiration
You will need to learn both types of respiration both aerobic and anaerobic.
Aerobic takes place in the presence of oxygen and produces CO2, water and a lot of ATP.
Anaerobic takes place without oxygen and produces lactate in animals or ethanol and CO2 in plants - but not very much ATP in both cases.
As you can see aerobic respiration is divided into 4 stages - Glycolysis, Oxidative decarboxylation (link reaction), Krebs Cycle and the ECT.
