Cell Respiration Flashcards
Define Cell Respiration
Cell respiration is the controlled release of energy from organic compounds to produce (adenosine triphosphate) ATP. The main organic compound used for this process is carbohydrates (glucose), although lipids and proteins can also be digested.This energy is used for a wide range of processes including active transport and protein synthesis.
State the two main types of Cell Respiration
1) Anaerobic respiration – involves the partial breakdown of glucose in the cytosol for a small yield of ATP
2) Aerobic respiration — utilises oxygen to completely break down glucose in the mitochondria for a larger ATP yield
Is ATP an immediate energy source and state the significance of the answer to this question
ATP (adenosine triphosphate) is a high-energy molecule that functions as an immediate source of power for cell processes.
Advantage
The advantage of ATP is that it is immediately available as an energy source in the cell. It can diffuse to any part of the cell and release its energy within a fraction of a second.
Describe the relationship between ATP and ADP
One molecule of ATP contains three covalently linked phosphate groups – which store potential energy in their bonds. When ATP is hydrolysed (to form ADP + Pi) the energy stored in the phophate bond is released to be used by the cell. Cell respiration uses energy stored in organic molecules to regenerate ATP from ADP + Pi (via oxidation)
Describe the process of Glycolysis (the link reaction)
ATP gets created through cellular respiration. Cells need ATP to power their chemical reaction. The process through glucose is broken down to make ATP begins with Glycolysis. During glycolysis, which takes place in the cytoplasm of a cell, two molecules of ATP plus enzymes begin to break down glucose into two immediate molecules called Phosphoglyceraldehyde (PGAL). Enzymes in the cytoplasm will then add another phosphate to the two immediate molecules, converting the PGAL into another immediate molecule. Next 2 NAD+ with help of an enzyme will strip off hydrogens from the two immediate molecules, one NAD+ strip off from one of the immediate molecules, and the other NAD+ strips off hydrogen from the other immediate molecule, creating NADH molecules which enter the mitochondria. Next, four molecules of ADP with the help of enzymes strip off phosphates from the two immediate molecules (each possesses two phosphates), creating four ATP molecules and transforming the two immediate molecules into pyruvate molecules. Though there are 4 ATP molecules created, the is only a net gain of 2 ATP as 2 ATP molecules were used to catalyst the start of the process of Glycolysis.
List the Stages of Cell Respiration in Order in the aerobic pathway
1) Glycolysis
2) Kreb Cycle
3) Electron Transport Chain
Describe the two possible pathways after Glycolysis
After Glycolysis, pyruvates are going to be broken down even further through:
1) the aerobic pathway – with oxygen, leading to the Kreb cycle and the electron transport chain
2) Anaerobic pathway — (fermentation) involves the breakdown of carbohydrates in the absence of oxygen. In yeasts, fermentation results in the production of ethanol and carbon dioxide – which can be used in food processing:
Bread – Carbon dioxide causes the dough to rise (leavening), the ethanol evaporates during baking
Alcohol – Ethanol is the intoxicating agent in alcoholic beverages (concentrations above ~14% damage the yeast)
Explain the process of the Kreb Cycle
Two molecules of pyruvate migrate into the mitochondrial matrix where the Kreb cycle will take place. NAD+ molecules will then strip off hydrogens the two Pyruvate, molecules to form NADH and CO2 molecule is created as a waste product. Consequently, each pyruvate molecule will be broken down into acetic acid. Coenzyme-A will then bond to acetic acid creating Acetyl-CoA (an immediate molecule). Acetyl-CoA will then bond with a 4 carbon molecule from the previous Kreb cycle to form citric acid (a 6 carbon molecule). Citric acid will then be broken down into a 5 carbon molecule and in the process, NADH is created (strips off a hydrogen from the critic acid molecule) and CO2 is also a by-product. The 5 carbon molecule will then be broken down into a 4 carbon molecule, creating NADH, a molecule of ATP and CO2 as a by-product. Enzymes will rearrange this 4 carbon molecule into another 4 carbon molecule. In the process of doing this, a molecule of NADH is created and FADH2 is also created. Acetyl COA will then bond to the rearranged 4 carbon molecule to recreate Citric acid. The process repeats itself. In total 8 molecules of NADH were created, 2 FADH2 were created, 6 C02 molecules were created and 2 ATP molecules were created (numbers are doubled because they are 2 pyruvate molecules broken down).
Explain what happens in the Electron transport chain (Sidenote: Ask Mr. Stewart if this takes place in the Cristae)
Embedded in the inner mitochondria membrane are protein complexes that drive the electron transport chain. The molecules NADH and FADH2 are broken down into NAD+ and FAD and electrons stripped from these two molecules become embedded in the inner mitochondria membrane and hydrogen ions from these molecules attach to protein complexes in the inner mitochondrial membrane. The electron now embedded in the inner mitochondrial membrane start a chain reaction that active protein channels, pumping H ions out of the matrix. Once all the hydrogens are out of the matrix, the hydrogen ions will rapidly diffuse through ATP synthase and activate it. As hydrogen ions diffuse through, ATP synthase brings together ADP and a phosphate molecules to form ATP. This process happens repeatedly. In the end, up to 34 ATP can be created. Oxygen from the air we breathe will bond with two of the hydrogens and electrons that regathered in the matrix, producing water as a by-product.
Distinguish between the products of Aerobic respiration and Anaerobic respiration
1) Aerobic respiration
CO2 and water
2) Anaerobic respiration
Humans: lactate
Yeast: CO2 and ethanol
Discuss the difference between Aerobic respiration and Anaerobic respiration with regards to how muscles use energy
Anaerobic respiration can only be used to produce ATP for about two minutes. It is therefore used in muscles carrying out very vigorous exercise, (e.g sprinting)
anaerobic cell respiration produces fewer molecules of ATP per glucose, thus, it is used in muscles carrying out moderate to low intensity exercise.
Define a Respirometer and its function and how it works
A respirometer is a device that determines an organism’s respiration rate by measuring the rate of exchange of O2 and CO2
1) The living specimen (e.g. germinating seeds or invertebrate organism) is enclosed in a sealed container
2) Carbon dioxide production can be measured with a data logger or by pH changes if the specimen is immersed in water
3) When an alkali is included to absorb CO2, oxygen consumption can be measured as a change in pressure within the system
4) The pressure change can be detected with a data logger or via use of a U-tube manometer
Discuss the ethical implications of using Respirometers?
To assess the ethical implications of the experiment involving animals before doing it, these questions should be asked:
- Will the animals suffer pain or any other harm during the experiment?
- Are there unacceptable risks to the animals, for example, contact with the alkali?
- Will the animals have to be removed from their natural habitat and if so, can they be safely returned to it and continue to live natural lives?
Discuss the factors that factor Cell Respiration
Factors which may affect respiration rates include
1) temperature
2) hydration
3) light (plants)
4) age
5) activity levels
An increase in carbon dioxide levels will indicate an increase in respiration (CO2 is a product of aerobic respiration)
A decrease in oxygen levels will indicate an increase in respiration (O2 is a requirement for aerobic respiration)
