Topic 5 - Photosynthesis Flashcards
Why is respiration important?
- Respiration produces ATP to release energy.
- For active transport, protein synthesis etc.
What are the stages of aerobic respiration?
Glycolysis, the link reaction, Krebs cycle, oxidative phosphorylation.
What are the stages of anaerobic respiration?
Glycolysis and NAD regeneration.
What happens in glycolysis and where does it occur? Specify what products are at the end of this stage.
Where is it? Cytoplasm.
What happens?
Step 1 - Glucose is phosphorylated to glucose phosphate using inorganic phosphate from two ATP.
Step 2 – It is then hydrolysed into 2 triose phosphate.
Step 3 – These TP molecules are then oxidised into 2 pyruvate.
During this process, 2 NAD molecules are reduced and become reduced NAD and 4 ATP are regenerated.
Explain what happens in the link reaction and where it occurs.
Where is it? Mitochondrial matrix.
What happens?
Step 1 – Pyruvate oxidised into acetate.
C02 is produced and reduced NAD is produced.
Step 2 – Acetate combines with coenzyme A, forming Acetyl Coenzyme A.
What happens in the Krebs cycle and where does it occur?
Where is it? Mitochondrial matrix.
What happens?
Step 1 – Acetyl coenzyme A reacts with a 4C molecule. This releases coenzyme A, producing a 6C molecule that enters the Krebs cycle.
Step 2 – In a series of oxidation – reduction reactions, the 4C molecule is regenerated and 2 C02 are lost, coenzymes NAD and FAD are reduced. Substrate level phosphorylation = ATP produced.
What happens in oxidative phosphorylation and where does it occur?
Where is it? Inner mitochondrial membrane.
What happens?
Step one- reduced NAD/FAD is oxidised to release H atoms, these are then split into protons and electrons.
Step two- electrons transferred down the electron transfer chain by redox reactions.
Step three- energy release by electrons is used in the production of ATP from ADP and an inorganic phosphate which is known as the chemiosmotic theory. Energy used by electron carriers to actively pump protons from the matrix into the membrane space. Protons diffuse into matrix down an electric chemical gradient via ATP synthesis. Releasing energy to synthesise ATP from ADP and inorganic phosphate.
Step four-in the matrix at the end of the electron transport chain, oxygen is the final electron accepter, so protons, electrons and oxygen combined together to form water.
What happens in NAD regeneration and where does it occur?
Where is it? Cytoplasm.
What happens?
Step one-pyruvate is converted into lactate or ethanol.
Step two- oxidation of reduced NAD means the NAD is regenerated so that glycolysis can continue allowing continued production of ATP.
Suggest why anaerobic respiration produces less ATP per molecule of glucose than aerobic respiration?
Only glycolysis is involved which produces only two molecules of ATP plus there is no oxidative phosphorylation which forms the majority of ATP roughly around 34 molecules.
Give example, examples of other respiratory substrates?
Fatty acids from hydrolysis of lipids which are converted into acetyl Co enzyme A.
Amino acids from hydrolysis of proteins which are converted to intermediates in the Krebs cycle.
Describe how a respirometer can be used to measure the rate of aerobic respiration?
First add a set mass of single celled organism for example yeast to a set of volume of substrate for example glucose. Next at a buffer to keep the pH constant. Then add a chemical that absorbs carbon dioxide for example sodium hydroxide. After this place in a water bath a set temperature to allow it to equilibrate. Finally measure the distance moved by the coloured liquid in a set time.
In required practical nine explain why the liquid moves?
Organisms aerobic be respire and take in oxygen, CO2 is given out but absorbed by the sodium hydroxide solution so the volume of gas and pressure in the container decreases so the fluid in the capillary tube moves down the pressure gradient towards the organism.
Require practical nine explain why the respirometer operators is left open for 10 minutes?
Which allows the operators to equilibrium which allows for overall pressure and expansion to change throughout and respiration rate of the organism to stabilise.
Required practical nine explain why the apparatus must be airtight?
Prevent air from entering or leaving and change the volume and pressure affecting the movement of the liquid.
In required practical line, describe a more accurate way to measure the volume of gas?
By using a gas syringe.
Describe how the rate of respiration can be calculated?
Calculate volume of oxygen or the CO2 consumed by calculating cross sexual area of a capillary tube and multiplying it by the distance that the liquid has moved.
In the methylene blue practical, give examples of variables that should be controlled.
The volume of a single celled organism, volume concentration and type of respiratory substrate, temperature, pH, the volume of redox indicator.
In the methylene blue practical, why would you leave the tubes in the water bath for five minutes?
To allow solutions to equilibrium and reach the same temperature as the water bath.
In the methylene blue practical, describe a control experiment and why it should be done.
Add methylene blue to boiled yeast with all other conditions the same to show that change due to respiration.
Suggest and explain why you must not shake tubes containing methylene blue?
Shaking it would mix the solution with oxygen which would oxidise the blue and cause it to lose its electrons so blue turned back to the colour it was originally.
Suggest one source of error using blue and explain how it can be reduced?
Subjective as it’s due to determination of colour change however you can compare the results to a colour standard or a colour for quantitative results.
How is biomass formed in plants?
During photosynthesis plants make organic compounds from atmospheric or aquatic CO2. Most sugar synthesis are used by the plant as respiratory substrate. The rest is used to make other groups of biological molecules and formed biomass.
How can biomass be measured?
Mass of carbon or dry massive tissue per a given area.
