Tutor profile: Yeap W.
Subject: Natural Sciences
Discuss the differences of the structure and function of a cell's organelles.
Organelles play an important role as each of them carries out a specific function in which they were specialized with the division of labour with three different stages of cell division, differentiation and specialization. The organelles were membrane-bounded, which indicates that the internal membranes are present around the organelles and are visible under electron microscopes as they suspended within the cytosol. First, the nucleus is one of the conspicuous of the whole cell, in which it is located at the center of the cytoplasm. The nucleus is surrounded by two layers of membrane, in which they were nuclear envelope as well as the inner region of the nucleus that plays the role as nucleolus. The main function of the nucleolus functions as the site of ribosomal RNA production. The main function of the nucleus is to control all metabolic pathways as well as the molecular activities of the cells, it also carries the genetic information of the cells whereby they will condense during cell division. The nuclear envelope contains small circular openings in which they allow the production of messenger RNA as well as their protein sub units with ribosomal RNA to enter the cytoplasm to perform protein synthesis at the ribosomes site. As for ribosomes, its structural diameter would be approximately 20 nm. It can move freely in the cytoplasm or attached to the endoplasmic reticulum to form rough endoplasmic reticulum (RER). It is assembled with one large protein sub-unit (60S) and one small protein sub-unit (40S) which includes the acceptor site, peptidyl site and an exit site in which the whole structure slides through the messenger RNA (codon) and allows the attachment of transfer RNA (anti codon) which carries the complementary genetic codes of the DNA in the nucleus with the process of transcription. The ribosomal site advances the RNA translation process and forms functional polypeptide chains. Lysosomes is one of the free-moving organelles in the cell in which it is membrane-bounded as well as the internal contents were hydrolytic enzymes, the internal lumen pH level was maintained acidic. The hydrolytic enzymes carried within the lysosomes can carry out various activities such as digestion (endocytosis: phagocytosis or pinocytosis, cell surface signalling as well as energy and nutrients absorption. It is really specialized when its hydrolytic enzymes tends to carry out autophagy and autolysis. The lysosomes release the hydrolytic enzymes into the food vacuole/ autophagososomes. Vacuoles are large water sac-like component in which it is formed with the assemblage of vesicles from the endoplasmic reticulum and dictyosomes, which are enclosed with the tonoplast membrane. The vacuoles take up 95% of the cell volume if present in plant cells, which pushes the nucleus to the peripheral and they can absorb water and to release water according to water potential of the environment of the cells and control their turgor pressure. Mitochondria and chloroplast are both energy-conversion organelles which possessed their own DNA, as they have 70S ribosomes similar to prokaryotes. Thus, they were thought to prokaryotes and they underwent endosymbiotic relationship with its host cell with evolutionary development. If we compare both of their differences: 1. Mitochondria could be found in animal cells and plant cells; whereas the chloroplasts could be found in only plant cells. 2. Mitochondria tends to undergo the process of respiration with the usage of ATP produced under oxidative phosphorylation and intermediate phosphorylation and oxygen acts as the terminal acceptor of the transport chain; whereas chloroplast undergoes photosynthesis including the production of ATP, NADPH and oxygen as the side product, carbon dioxide is the key compound for dark reaction. 3. Mitochondria is involved in many processed steps including glycolysis, link reaction, Krebs cycle and electron transport chains; whereas chloroplast has processed level of steps which includes dark reaction and light reaction. 4. Mitochondria has a smooth external membrane and an internal membrane which is folded with the internal side contains ATP synthase; whereas chloroplast has a double membrane and an internal matrix with various enzymes suspended with the liquid-like stroma and thylakoid structures stacked together to form grana.
What is the purpose of oxidation?
Oxidation is a process which leads to the chemically loss of hydrogen and the gaining of oxygen from a certain biochemical component, whereby it is the essential part of biochemical processes and metabolism. Oxidation in our body usually takes place with the presence of oxidoreductase, and the most recurring example of oxidation-reduction activities would be within the respirational cycles. The oxidative phosphorylation usually takes place within the respiration cycle when there is production of ATP and the usage of ATP molecules in glycolysis, link reaction and Krebs Cycle. Besides that, chemiosmosis requires the oxidation process, in which the redox reaction of the electron carries of the chain to form water molecules at the end of the terminal electron acceptor, Thus, in conclusion, oxidation is important in energy-generating as well as the metabolism of the body and cell.
Babies fed on milk for food. Milk is digested in the digestive tract so that it can be absorbed and readily used. What are the three main components of milk that have to be digested? Explain what happens to the milk when it reaches the digestive system?
The contents of the milk was not yet digested in the mouth. It then travels into the oesophagus and then into the stomach. Then, the stomach gastric juice is secreted by the gastric glands, whereby the rennin components transformed the milk proteins to insoluble milk proteins (caseinogen to casein). The casein is then hydrolysed by pepsin to polypeptide chains. As for the case of fats and lactose components, it is not digested in the stomach compartment and it is further churned by peristalsis into the duodenum. The milk enters into the duodenum bit by bit through the contractions of the pyloric sphincter. The pancreatic juice including the enzyme lipase, amylase and trypsin. The trypsin hydrolyses polypeptide chains to peptide components. As for the fat components of the milk, the molecules will be emulsified first by the bile produced by the gall bladder, which was subsequently released into the duodenum. Then, the emulsified fat components will be hydrolysed by lipase into fatty acids and glycerol. The milk components travels into the ileum, in which the intestinal juices were released. The peptidase breaks peptide components into amino acids, whereas lactase breaks down lactose into glucose and galactose. The digested products from the milk such as glucose, galactose, amino acids, fatty acids, glycerol as well as vitamin A and D was then absorbed through the villi in the ileum. The only difference is that glucose, galactose, amino acids, mineral salts, as well as water-soluble vitamins were absorbed through the blood capillaries in the villi; whereas the fatty acids, glycerol and fat-soluble vitamins are absorbed through the lacteal in the villus. From the ileum, the remaining content of the milk will be released into the colon where water is absorbed .
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