Joshua Post 6

Since the day we planted our plants, they have been growing. They have grown a lot since then, and that is due to various cellular processes. Those very important cellular processes are know as Mitosis, Photosynthesis, and Cellular Respiration. They all play a big role in the growth of our Cabbage plants in regards to biomass.

Mitosis is a very important process most animal and plant cells undergo. Before mitosis, our plants cells must go through interphase. First, the cells grow in size and build organelles. Then, the cells DNA is copied and microtubules form. The chromosomes, which is DNA wrapped up with histone proteins, are condensed during the first stage of mitosis, called prophase. During the third phase of mitosis, anaphase, the copies of chromosomes are pulled apart and each side of the parent cell has a copy of identical genetic information. During a process that comes after mitosis, called cytokinesis, a cell wall must form in between the new cells. This results in two daughter cells that result from the parent cell. This is the main way that our plant is adding biomass because the cells in our plants structures are undergoing mitosis every day. This results in more cells, which expands tissues, which results in more biomass. Our plants derive the energy to do this from ATP, a molecule made during photosynthesis and cellular respiration.

During photosynthesis, the chloroplast and chlorophyll in the plant cells take in solar energy, carbon dioxide, and water to convert to glucose and oxygen (6CO2 + 2H2O --> C6H12O2 + 6H2O). When light hits the plant, it excites the chlorphyll, which is a light absorbing pigment in the chlorplasts, and enzymes begin breaking apart water molecules. The hydrogen and oxygen molecules travel in a electron transport chain along the thylakoid membrane of the chloroplasts. NADPH is then created from NADP+, and ATP is also created through enzyme ATP synthase. These are the products of the light dependent reactions, meaning light energy was required to drive them. The light independent reactions build sugars using the ATP and NADPH made in the light dependent reactions. These help the plant grow in biomass because they provide energy for the cells to undergo mitosis. Cellular respiration also produces ATP.

In the process of cellular respiration, plants use the products of photosynthesis as the reactants. Cells use glucose and oxygen to yield carbon dioxide, water, and ATP (C6H12O2 + 6H20 --> CO2 + H2O + ATP).  The main idea of cellular respiration is to break down sugars into energy that the plant can use. Cellular respiration usually uses oxygen, and is called aerobic respiration. Cellular respiration however is not limited to only occuring when oxygen is present. When it takes place without oxygen, it is known as fermentation, but only glycolysis can happen. Cellular respiration has 4 stages; glycolysis, the Krebs cycle, link reaction, and electron transport chain. In glycolysis, glucose in the cytoplasm is broken down to two molecules of pyruvate. The pyruvate is broken down to produce acetyl-CoA in a process known as pyruvate oxidation. The Krebs cycle then uses this molecule to produce NADH, FADH2, ATP molecules, and carbon dioxide. The NADH and FADH2 will pass their electrons through the electron transport chain and the result will be ATP, through a process known as oxidative phosphorylation. As the electrons pass down this chain, energy is released and used to pump protons out of the mitochondrial matrix, which results in a gradient. The protons go back into the mitochondrial matrix through an enzyme known as ATP synthase, which makes ATP. The ATP is used for many reasons, but primarily for growth. Biomass is added from this growth.

The Production of enzymes depends mainly on two things, ribonucleic acid and ribosomes. To build enzymes, a mRNA copy has to be transcribed in the nucleus from DNA. RNA polymerase would transcribe the mRNA. The mRNA strand would then leave the nucleus and a ribosome would eventually attach itself to it. The ribosome would then start translating 3 nucleotides at a time, and would start at codons UAG, UGA, or UAA. The tRNA in the ribosome would attach an anti-codon to the mRNA codons and the oligopeptide, which in this case is an enzyme, would begin being assembled. One amino acid is translated from 3 nucleotides. This is how our plants would make enzymes if a message was sent to the nucleus that the production of certain enzymes was needed. After they enzyme is synthesized, it would have to travel to its destination. To do this, the enzyme would first pass through the endoplasmic reticulum. If the enzyme was needed somewhere outside of the cell, it would go to the golgi apparatus where it would be packaged in vesicles and sent to it's destination.