Unit 5 Cell Biology Illustrated Report - Marked at Achieved (ungraded unit) PDF

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Unit 5 Cell Biology is an ungraded unit so you are only able to reach achieved or a resub until you pass the unit. I received and Achieved on the first submission, just be mindful of using Wikipedia. Apparently I used Wikipedia and I am discouraged from using it, however there no trace of Wikipedia ...

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8/10/2021

Cell biology. Unit five.

Holloway, Emily Francesca Anne STONEBRIDGE COLLEGE

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Table of Contents Cover page ………………………………………………………………………………….. Page 0 Table of contents …………………………………………………………………………… Page 0 Introduction ………………………………………………………………………………….. Page 1 Cell structure …………………………………………………………………………... Page 3 to 4 Cellular metabolism …………………………………………………………………… Page 5 to 8 Cell growth and division …………………………………………………………….. Page 9 to 10 Conclusion …………………………………………………………………………………. Page 11 Recommendations ………………………………………………………………………... Page 12 References ………………………………………………………………………….. Page 13 to 14 Bibliography ………………………………………………………………………… Page 15 to 17

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Introduction. This illustrated report has been composed to demonstrate, describe, and explain the fundamentals of cell biology and how the cell interacts with the human body to sustain life in a comprehensive manner. Throughout this report, I will touch on my understanding of cell structure, cellular metabolism, cell growth and cell division.

To demonstrate my understanding of cell structure I will; 1. Discuss the selected characteristics of living cells. 2. Compare and contrast prokaryotic and eukaryotic cells, and explain the impact that viruses have on them. 3. Discuss eukaryotic sub-cellular structure and organelles.

To demonstrate my understating of cellular metabolism I will; 1. Explain the role of the cell membrane in regulating how nutrients are gained and waste products lost. 2. Explain how animal cells use nutrients to provide the energy for growth, movement, and cell division. 3. Explain the role of nucleic acids in the nucleus and cytoplasm. 4. Explain the synthesis of proteins.

Finally, to demonstrate my understanding of cell growth and division, I will; 1. Explain the generation of specialised tissues from embryonic stem cells. 2. Explain the process of interphase and factors that initiate cell division, and their importance. 3. Explain how genetic information is received by each daughter cell. 4. Compare and contrast cancer cells with normal cells. The information included throughout this report has been gathered through the use of study materials acquired through Stonebridge College, internet articles and books, gathering information, utilising images and tables from other sources of education.

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Cell structure. Characteristics of living things. It is a well-known fact that for an organism to be considered living, it must have the following characteristics, which is referred to as Mrs. Gren. The following characteristics include; 1. Movement – the organism’s ability to move within its environment, whether this is to escape predators, hunt for food, or to find a sexual mate. 2. Respiration – the cell’s ability to deconstruct nutrient molecules to create energy for the cell, this energy source is known as adenosine triphosphate (ATP). 3. Sensitivity – the cell’s ability to adapt to its environment or remain in homeostasis. Different organisms react differently to any changes. 4. Growth – Through homeostasis and nutrition, cells can increase in size and complexity, and can also produce new tissue. (Basic Biology, 2015) 5. Reproduction – The cell/organism’s ability to produce offspring via binary fission. Mitosis or meiosis. 6. Excretion – The organism’s ability to remove waste products such as urine or CO2. 7. Nutrition – The organism’s ability to feed, store and use its energy source to facilitate growth and reproduction.

Prokaryotic and Eukaryotic cells. Prokaryotic cells are the most primitive of all cells, alongside the archaea group. Prokaryotic cells do not have a nucleus, organelles, are single-celled, and have a nucleoid, which houses the DNA (Khan Academy, n.d.). These type of cells can withstand inhospitable environments allowing them to tolerate extreme temperatures, salinity, and acidity levels. Additionally, prokaryotic cells reproduce through binary fission and use anaerobic respiration to utilise the cytoplasm. Prokaryotic cells also have a plasmid, which holds additional DNA that replicates independently thus giving the cell an evolutionary advantage in relation to reproduction. (Encyclopedia Britannica, n.d.) Eukaryotic cells are a more advanced version of prokaryotic/archaea cells and are a mutation of the more primitive bacterial cell. Eukaryotic cells are more advanced because they have a nucleus, organelles, and are multi-cellular. These cells are unable to withstand inhospitable environments. Additionally, Eukaryotic cells reproduce through mitosis and meiosis and use aerobic respiration to utilise its mitochondrion. Figure 1 - Differences between the However, Prokaryotic and Eukaryotic cells do Pro/Eukaryotic Cell (microbiologynote.com, also share commonalities with each other. 2010) For example, both cell groups have DNA, ribosomes, cytoplasm, and a plasma membrane.

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The impact of viruses. Viruses are an “infectious agent of small size and simple composition that can multiply only in living cells of animals, plants, or bacteria.” (Wagner, 2019) Viruses work by infiltrating a cell and interrupt the cellular process thus allowing an encoded protein to replicate the genetic material of the virus, otherwise referred to as an obligate intercellular parasite that is of an acellular nature. (Cohen, 2016) Figure 2 Structure of A virus has no cells and can only reproduce once it has infiltrated a a virus. (Davidson, host-cell, they are also unable to respond to external/internal stimuli 2019) and lack metabolism and homeostatic mechanisms. The virus operates by overriding the cells metabolic structures and ribosomes allowing it to create virions. Additionally, viruses are comprised of DNA/RNA within a nucleic acid that is encased in a capsid, this genetic information is passed through the virus’s spikes. (Unit 5 Cell Biology –1 page 1.2 2020)

Eukaryotic sub-cellular structure and organelles. Eukaryotic cells have a variety of organelles that allow for itself to function efficiently. In its simplest terms, the organelles all play a crucial function that allows for cell survival and function. 1. Cytoplasm – Contains enzymes, sugars, salts, amino acids, and nucleotides. The enzymes aid in metabolic reactions. 2. Nucleus – The nucleus is home to the organisms DNA and RNA. 3. Nucleolus – This manufactures ribosomes using chromatin. 4. Mitochondrion – This is where aerobic respiration occurs and is known to have an inner and outer membrane, the former plays apart in the synthesis of adenosine triphosphate. 5. Ribosomes – These control protein synthesis within a cell. They can be found in either the RER or floating freely in the cytoplasm. 6. Smooth Endoplasmic Reticulum (SER) – These aid lipid synthesis and transportation. 7. Rough Endoplasmic Reticulum (RER) – These have their own attached ribosomes that aid in the production/modification or protein and carbohydrates. 8. Golgi body – These consist of cisternae, and they receive/modify proteins from the ER. They enter through one side of the cell for modification and once on the other side the membrane pinches inwards to create vesicles. The vesicles begin fusing with the membrane to secrete its contents, this is known as exocytosis. 9. Vacuole – These contain water and diluted salts in a membrane-bound sac. 10. Lysosome – These contain hydrolytic enzymes which breakdown biomolecules. Lysosomes are known as suicide bags due to the absorption of toxic chemicals via endocytosis.

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11. Cytoskeleton – Used to support the body and cell motility by developing a vast network of protein fibres. It aids in transference of chromosomes during mitosis and meiosis. (Cell Biology - page 1.3, 2020)

Cellular metabolism. The role of the cell membrane. The role of the cell membrane is to control what enters and leaves the cell by developing a thin, flexible, selectively permeable wall around its organelles. The cell membrane is comprised of three different molecules, and these are; phospholipids, proteins, and carbohydrates: creating the phospho-lipid-protein bi-layer (Whitehouse et al., 2014).

Figure 3 - Cellular membrane (The Editors of Encyclopedia Britannica, 2019)

The bilayer is comprised of fatty molecules over two layers and protein molecules that are spread throughout intermittently. Another part of the cell membrane structure is that the phospholipids are arranged in a fluid-mosaic structure, meaning that its hydrophilic head is water loving and points outwards, whilst the hydrophobic tail is made from fatty acids and points inwards thus repelling water. Intrinsic proteins are a substance that are infused within the bilayer that allow polypeptides to contact the hydrophobic tails of the phospholipids. The intrinsic protein is often put into two groups: the first group has most of its mass outside of the cytoplasm and the second group has the most of its mass inside the cytoplasm. As well as this, intrinsic proteins also have the capability to move from one side of the membrane to the other (transmembrane). Extrinsic proteins are found to be attached to the membrane wall from the outside by ionic/hydrogen molecular reactions, thus meaning they are hydrophilic. Because of this, extrinsic proteins are often referred to as peripheral proteins. These proteins become receptors in cells allowing to signal each other with a combination of glycoproteins. Additionally, cholesterol contributes to the structure of the bilayer by providing stability.

Methods of transportation. There are five methods of transportation which allow for substances to cross the cell membrane, and these include; Lipid diffusion – this allows for the transportation of lipid soluble molecules, such as water, oxygen, and carbon dioxide, and occurs within the bilayer. The method requires no energy and causes levels to go from a high concentration gradient to a low concentration gradient. Osmosis – this allows water molecules that are high in concentration to pass through a partially permeable membrane to a region that is lower in concentration. Facilitated diffusion – this refers to molecules that move from a region of high to low concentration, with the assistance of a transmembrane protein, thus requiring no energy on behalf of the cell. The two forms of facilitated diffusion include; 1. Channel protein – a pore allowing the substance to use the protein. These proteins are gated which allows for the cell to control what ions enter/exit. 2. Carrier protein – these have a binding site that flip between two states, always leaving one site open. This allows for the substance to bind on the concentrated side before its release on the less concentrated side.

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Active transport – this refers to the transference of substances from a low to a high concentration gradient via the transmembrane protein (pump-molecule). The protein binds to a molecule before transporting it from one side to the other. The transmembrane referred to as the ATPase enzyme which begins the process of catalysing the breakdown of ATP, ADP, and Pi. This breakdown of molecules releases energy allowing for the cell to change shape and move across the membrane. By use of vesicles – this refers to large molecules, such as starch, being transported from proteins, nucleotides, and polysaccharides. If a molecule is being transported into the cell membrane, it is referred to as endocytosis, this is because the material is folded into the cell membrane causing it to pinch shut thus creating a closed vesicle. However, if a molecule is being transported out of the cell membrane it is referred to as exocytosis, which causes the RER/Golgi to secrete hormones/digestive enzymes outside of the cell.

Nutrients in relation to cell growth, movement, and division. Animal cells require the use of energy (ATP) on a cellular level to support cell growth and division. The creation of ATP occurs through aerobic respiration which begins with the chemical compound glucose (C₆H₁₂O₆) being broken down in four individual steps. 1. Glycolysis – this breaks down C₆H₁₂O₆ into two molecules of pyruvic acid. From here four molecules of ATP molecules are produced, although only two of these are used alongside two NADH molecules. Figure 4 - Cellular respiration. 2. Intermediate stage – the pyruvic acid is moved (Earth's Lab, 2018) to the mitochondria to drop a singular CO₂ molecule. As a result, Acetyl-coA is formed by the end-product bonding with coenzyme A. 3. Krebs cycle – Acetyl-coA is then broken down to form x1 ATP, x3 NADH and x1 FADH2, whilst CO₂ is produced as a by-product of this reaction. 4. Electron Transport Chain (ETC) – the FADH2 and NADH molecules carry in an electron into the chain prior to bonding with O₂ and H molecules to create H₂O, thus creating 36 ATP molecules. This part of the process occurs within the proteins which are embedded in the mitochondrial membrane. Due to the processes of endo/exocytosis and active transport, coupled with the progressive movement of nutrients throughout the cell: the cell can maintain homeostasis. Due to homeostasis, the cell is then able to efficiently convert chemical energy into kinetic/heat energy through cell movement. Additionally, the cell can reproduce through mitosis and meiosis in part because of its existing organelles, which include the centrioles, and chromatids.

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Nucleic acids. Nucleic acids are comprised of polynucleotides which house the DNA and RNA. Firstly, the polynucleotide chain is composed of a phosphoric acid, pentose, and five organic bases split into two groups. Secondly, the pentose is a structure composed of five carbon molecules which include ribose and deoxyribose whilst the organic base features pyrimidines and purines which are chemically bound to form a codon. Furthermore, the pyrimidines consist of Cytosine (C), Thymine (T) an Uracil (U), whereas purines consist of Adenine (A) and Guanine (G). The DNA is composed of a double helix structure, with two polynucleotide strands coiled around each other to create said structure. Additionally, this structure has a sugar-phosphate chain on the outside and its base pairs (T, A, G and C), on the inside which connect to the relevant base pair on the opposite strand through hydrogen bonds. (Nucleic acid - Deoxyribonucleic acid (DNA), 2019) As well as this, RNA is a singular polynucleotide strand, and is comprised of ribose, the adenine, guanine, cytosine, and uracil bases. There are three forms of RNA, and these include;

Figure 5 - Nucleic acids. (Wikipedia Contributors, 2019)

1. rRNA – the rRNA helps catalyse peptide bonds and form an integral part of the ribosome, which facilitates protein synthesis. 2. mRNA – these are exact copies of DNA within the nucleus, which are carried to the cytoplasm for protein synthesis. Figure 6 - RNA types. 3. tRNA – these have a C-C-A sequence, in relation to its base pairs, and once this (ib.bioninja.com.au, n.d.) sequence has been developed it allows for an amino acid to attach facilitating protein synthesis.

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The polypeptide chain is created through protein synthesis, and it occurs within three stages listed below;

Figure 7 - Protein structure in four levels. (Lumenlearning.com, 2013)

1. Transcription is the conversion of DNA to RNA by using RNA polymerases, this allows for the DNA to be copied exactly into the RNA. (Khan Academy, 2016) Transcription occurs in the nucleus. 2. Activation is the binding of amino acids to the tRNA, which in turn allows for an anticodon (three unpaired bases) to be developed at the end of the process. Activation occurs in the cytoplasm. 3. Translation is where the mRNA attaches itself to the ribosome to follow through a process that will inevitably create a stopcodon, thus forming a completed protein and/or polypeptide chain. Translation occurs in the ribosome.

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Cell growth and division. Specialised tissues and stem cells. Firstly, stem cells can be defined as “special types of cells in multicellular organisms that are capable of self-renewal as well as the ability to differentiate into various types of cells for specific functions”. (MicroscopeMaster, 2019) Secondly, there are three types of stem cells which include; 1. Embryonic cells – these are found in the embryo. 2. Foetal cells – these are found in a developing foetus. 3. Adult cells – these are found within tissues in the body and are used in medical research to treat blood disease/cancer.

Figure 8 - Pluripotent stem cells. (MedicineNet, n.d.)

Next, embryonic cells are referred to as pluripotent, and this is due to their potential to become any type of cell or tissue within the organism. To put it simply, embryonic cells evolve from a fertilised egg (zygote) and becomes the blastocyst after four to six days. Additionally, the blastocyst is comprised of an inner (embryoblast) and outer (trophoblast) mass of cells, which respectively become the structures of the foetus and its placenta respectively. It is widely known that stem cells can treat a variety of illnesses which include heart disease, diabetes, blood disease, cancer, and multiple sclerosis. (BBC Bitesize, n.d.)

Interphase, factors, and cell division. Interphase is defined as “the period of the cell cycle during which the nucleus is not undergoing division”. (www.dictionary.com, 2019) As with all biological processes, interphase is split into stages, and these include; 1. G1 – the cell undergoes a rapid growth rate thus allowing for high levels of protein synthesis.

Figure 9 - Interphase. (Khan Academy, 2018)

2. S – the cell begins to replicate its pre-existing DNA, and this begins at the restriction point. 3. G2 – the cell begins to prepare for mitosis, beginning with the mitochondria dividing and the centrioles replicating, allowing for the cells natural energy store to increase.

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Once the cell has entered the stage of G2, it enters the cell division process known as mitosis. This process of cell division is also split into stages, and include; prophase, metaphase, anaphase, and telophase. Furthermore, mitosis creates daughter cells (identical copies of its parental cell) due to the division. Because of this, information is passed on to the daughter cell, leading the daughter cell to have exact copy of chromosomes as its parent whilst also aiding in the growth and repair of the cell itself.

Figure 10 - Prophase, metaphase, anaphase, and telophase with somatic cell division (mitosis). (Encyclopedia Britannica, n.d.)

Cancer cells. Cancer cells are described as a harmful mutation within a cell that was once healthy, and as a result has experienced a rapid and uncontrolled cell growth. Because of this there are a variety of differences between a healthy and a cancer cell. As seen in figure 11, we can identify that the structure of a cancer cell is vastly different to that of a healthy cell. For example, a healthy cell has a sole nucleus and is spherical in shape, with large amounts of cytoplasm, whereas a cancer cell has the exact opposite of these characteristics e.g., multiple nucleoli and mishappen.

Figure 11 - Cancer vs normal cells. (Normal Human Cell Cancer Cell Malignant Cancer Stock Illustrations – 65 Normal Human Cell Cancer Cell Malignant Cancer Stock Illustrations, Vectors & Clipart - Dreamstime, n.d.)

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Conclusion. In conclusion, we can see that the cell is a highly complex organism that requires a variety of other microorganism to maintain a coordinated and balanced environment for life to be sustained, whilst allowing it to thrive. Due to the vast array of factors that contribute to the health of the cell, cells can grow, divide, and metabolise with no intervention by the homosapien. However, this is not always the case, as we saw with the development of cancer cells. In relation to cancer cells, we identified that a normal healthy cell had mutated causing it to acquire a variety of characteristics that were detrimental to the health of the cell, and if al...