The importance of cycles in biology

Question 1

list your 4 points + an extra

Answer 1

1. nutrient cycles
2. krebs cycle
3. the cardiac cycle
4. the cell cycle

extra: light-independent reaction

Question 2

nutrients cycles: “important of cycles in biology”

Answer 2

• One major nutrient cycle is the nitrogen cycle which is important to the synthesis of chlorophyll
• Firstly, via nitrogen fixation mutualistic nitrogen-fixing bacteria use the enzyme nitrogenous to reduce gaseous nitrogen into ammonia
• Secondly, saprobionts feed on and decompose organic waste containing nitrogen to release NH3 gas which dissolves in water soil to form ammonium ions
• Thirdly, anaerobic denitrifying bacteria convert soil nitrates back into gaseous nitrogen, and the cycle continues again by nitrogen-fixing bacteria.
• This is an essential cycle due to the fact that plants require nitrogen in order to synthesise chlorophyll, which absorbs light energy for photosynthesis.
• Without chlorophyll, the plant would be unable to photosynthesise to produce glucose which is contained in their cell membranes as cellulose.
• Therefore, the plant cell walls would be unsupported due to lack of cellulose and unable to withstand turgor pressure, turning them flaccid.
• In conclusion, the importance of the nitrogen cycle is supplying plant cells with nitrogen so that they can synthesise chlorophyll for photosynthesis.

Question 3

krebs cycles: “important of cycles in biology”

Answer 3

• Aerobic respiration includes the Krebs cycle which is a series of redox reactions that occur in the matrix of the mitochondria, essential in generating ATP for muscle contraction in animals.
• This involves the binding of acetyl coenzyme A with a 4C compound, to generate a 6C molecule and releasing acetyl coenzyme A back into the link reaction.
• The 6C molecule is decarboxylated andhydrogenated producing a 5C molecule, the 2H+ ions released are used to reduce NAD.
• 5C molecule, a phosphate is removed and used togenerate ATP,substrate level phosphorylation. 5C is decarboxylated and hydrogenated again to produce 4C andCO2 and reduced NAD as well as 2x ATP.
• The ATP produced from the Krebs cycle is used to power metabolic processes such as muscle contraction.
• Without ATP, the myosin head would be unable to return to its resting position, therefore the muscles would be constantly contracting which can cause spasticity in animals.
• In conclusion, the importance of the Krebs cycle is that it generates ATP which returns myosin heads to their resting position so that muscles can relax - so that muscle contraction can continue.

Question 4

cardiac cycles: “important of cycles in biology”

Answer 4

• The cardiac cycle is important for animals that allows oxygenated blood to be delivered to our respiring tissues.
• During atrial systole, the atria contract decreasing volume and increasing pressure inside the atria so the atrioventricular valves open and blood flows into the ventricles.
• Then in ventricular systole, ventricles contract decreasing volume and increasing pressure so that the semi-lunar valves open and atrioventricular valves shut, blood is pushed out of the heart into arteries where it is delivered to the body.
• If there is a failure in the cardiac cycle, such as the failure of atrioventricular valves closing during ventricular systole there will be backflow of blood into the atria.
• This means that a smaller volume of blood is pushed into the aorta, and less oxygen is delivered to respiring tissue causing fatigue and shortness of breath.
• It can also lead to heart attacks. Therefore, the importance of the cardiac cycle is that it delivers oxygenated blood to the body, preventing fatigue and heart attacks.

Question 5

cell cycles: “important of cycles in biology”

Answer 5

• The cell cycle is also an important cycle for animals as it allows for the synthesis of 2 new genetically identical daughter cells to replace damaged/dead cells.
• The cell cycle consists of 4 stages: prophase, metaphase, anaphase, and telophase.
• In prophase, the nuclear membrane breaks down and chromosomes condense, in metaphase the chromosomes line up at the equator of the cell and each centromere of a sister chromatid has spindle fibres attached.
• In anaphase the spindle fibres contract to pull apart the chromosomes to opposite poles of the cell and in telophase the nuclear membrane begins to reform as the chromosomes de-condense thus producing 2 new daughter cells.
• If mitosis were to stop, we would be unable to synthesise new cells such as red blood cells which deliver oxygen to respiring muscles.
• Without red blood cells, our muscles would be unable to respire aerobically causing aplastic anaemia.
• In conclusion, the cell cycle is important as it allows for the synthesis of new red blood cells that allow our muscles to respire anaerobically.