Cell membrane A cell membrane protects the cell by being selectively permeable to substances going in and out of the cell. Typically, substances like glucose, oxygen, water and viruses enter the cell and carbon dioxide and waste products leave the cell. Found in plant, animal and bacterial cells.
Cell wall The cell wall provides structural support for the cell using turgor pressure, also allowing the cell to grow, this does not apply to bacteria cells. The cell wall is a fully permeable layer. A cell wall is found in fungi, algae plant and some bacteria cells. Cell walls are absent in protozoa and animal cells.
Chloroplasts Chloroplasts contain chlorophyll which uses photosynthesis to convert sunlight, water and carbon dioxide into glucose and oxygen. The glucose is stored as a food and oxygen is released into the atmosphere. Chloroplasts are found in green plant cells.
Cytoplasm Cytoplasm is a jelly like substance which is present in different parts of the cell. It gives structure to the cell and allows the passage of substances to different parts of the cell. Cytoplasm is found in both prokaryotic and eukaryotic cells.
Golgi Body The Golgi body modifies, sorts and packages protein and lipid molecules. It also processes molecules and facilitates the transport of lipid molecules throughout the cell. The Golgi body is an organelle found within the cytoplasm most eukaryotic cells.
Endoplasmic Reticulum (ER) The ER works closely with the Golgi body, it synthesises proteins and packages proteins. It then sends proteins to the Golgi body and other parts of the cell. There are two types of ER; Smooth ER and Rough ER. Smooth ER stores lipids and steroids and rough ER processes proteins. The rough ER has ribosomes attached to its surface which makes it rough. Smooth ER does not have ribosomes attached which making the surface smooth. The ER is an organelle found within the cytoplasm of most eukaryotic cells.
Plasmid Plasmids carry genetic information for bacteria. This information can aid bacteria to have resistance to antibodies. Plasmids are found in prokaryotic cell and some eukaryotic cells.
Flagella Flagella aid in the locomotion of cells. Flagella are found in all types of cells. However, some cells use cilia for locomotion.
Mitochondria Mitochondria regulate the cell metabolism. It also makes adenosine triphosphate, which is the chemical energy produced during the process of cell respiration. Mitochondria is found in Eukaryotic cells.
Nucleus The nucleus of a cell stores the majority of the cells genetic material (DNA). The nucleus controls cell reproduction, growth and protein synthesis and the metabolism of the cell. A cell nucleus is only found in Eukaryotic cells.
Ribosome Ribosomes are organelles that make protein. Ribosomes in the cytoplasm makes protein for the cell. Ribosomes attached to ER make proteins for inside and outside the cell. Ribosomes are found in the cytoplasm of eukaryotic cells or attached to ER. When ribosomes are attached to ER the ER is called a rough ER.
Vacuole Vacuoles in a cell are storage units for water, waste products, organic and inorganic molecules and enzymes. Vacuoles also regulate turgor and hydrostatic pressure in plant cells. Large vacuoles are found in plant and fugal cells and some prokaryotic cells. Small vacuoles are also found in animal cells.
Word count – 557
The meaning of the terms ‘prokaryotic’ and ‘eukaryotic’. (Task One part c)
A prokaryote is a single celled organism that does not have a nucleus also, prokaryotes do not have cell membranes within the cell, organelles or mitochondria. A eukaryote is a cell that has a nucleus, organelles and other functioning elements each enclosed by specific cell membranes. Bacteria are prokaryotic whilst plant and animal cells are eukaryotic.
Cell Structure (Task One-part d).
The difference between viruses and cells.
Viruses are much smaller particles than cells, they are only visible using an electron microscope. They have a nucleic acid core of deoxyribonucleic acid or ribonucleic acid and a protein coat. Viruses are not cells and so are not living organisms. Unlike cells they do not have cytoplasm, organelles, chromosomes or their own cell membranes. Viruses exist only as parasites and use the metabolic mechanism of their host to exist and they also need a host cell to reproduce. Viruses exist as inert particles called virions outside their host cell. Living things are made up of cells. Unlike viruses cells have a nucleus and the nucleus is capable cell division to reproduce existing cells.
Task one total word count- 755
The stages of mitosis (task-2a)
Mitosis is ordinary cell division; when cells are damaged or become too old new cells are created by mitosis to replace the old cells. A chemical signal called mitogen-activated protein kinase (MAPK) in the cytoplasm of a cell triggers mitosis, according to Evidence-Based Proactive Nutrition to Slow Cellular Aging. (Robert Fried, 2017, p. 4.2)
Interphase begins before cell division starts, it involves three different stages: the first growth phase, which is when the cell gets larger and making new parts of the cell; the synthesis phase which involves the synthesis of deoxyribonucleic acid (DNA); and the second growth phase which involves more protein being synthesised and the cell continuing to get larger. Before the cell divides the DNA of the cell must be copied and replicated.
Mitosis begins with the prophase stage; the DNA in chromosomes condenses and can be seen more easily.
The next stage is metaphase, the spindle now becomes fully developed and the nuclear membrane has gone completely. Chromosomes are organised and line up along the metaphase plate in the middle of the cell.
In anaphase as the spindle fibres shorten the chromosomes are pulled apart into identical chromatids. The cell elongates getting the cell ready to be split apart into two cells.
The next stage of mitosis is telophase. The spindle now breaks down and a new nuclear membrane forms around both groups of chromatids at each end of the cell.
Finally, cytokinesis involves the division of the cytoplasm, as the cell membrane squeezes into two identical daughter cells each with 46 chromosomes.
(task-2 b) The difference between stem cells and specialised cells
and; (task 2c) How embryonic stem cells develop into specialised cells.
Stem cells can grow into any specialised cell types in the body. However, stem cells are not specialised cells performing a specific task. Stem cells are capable of mitotic cell division to renew themselves to form new stem cells. Embryonic stem cells can grow in to any type of cell, adult stem cells are stem cells that can grow into some, but not all types of specialised cells. Also, Japanese scientists have created pluripotent stem cells, these are embryonic like stem cells that can change into any type of specialised cell.
In an organ specialised cells perform a specific function for which they have been created to do and they act together working and responding in unison in a controlled way. Some specialised cells can divide into new specialised cells of the same type, but most specialised cells need to be replaced by cell division of stem cells.
Embryonic stem cells are stem cells from an embryo other types of stem cells can be found in many tissues in the body. An embryonic stem cell is capable of forming any type of cell in the body.
Specialised cells are differentiated into different specialised cells through the process of gene expression. Genes that are not use in the specialised cell will remain switched off or repressed and appear coiled up in the DNA strands, however genes that are active in the specialised cell are switched on or expressed and appear uncoiled in the DNA stands. For example, genes used to make bone and cartilage tissue would be switched on and bone and cartilage cells would be made; or genes used to make brain cells may be switched on and brain cells would be made.
Cells start to become specialised through gene expression. The first stage of gene expression is transcription, here RNA is produced to help to form functional proteins that are required for the formation, shape, structure and function of the specialised cell. Then gene translation is the process of coding the proteins required in protein synthesis to form a specialised cell.
The differences between normal cells and cancer cells (task-2d)
Normal specialised cells communicate with each other, also signals from other cells can trigger appropriate cell death through apoptosis, when normal cells become damaged or get old necessary apoptosis also occurs. Normal cells typically adhere together, molecules on the cell surface allow the cells to stick together. Normal cells are mostly regular in size and shape. White blood cells can destroy normal cells when they become damaged or infected. Normal cells perform the function that they are designed to do.
Damaged or old cancer cells do not undergo apoptosis or communicate and they continue to grow, and even reproduce before they are mature cells, they also have many mutations and genetic faults. Cancer cells do not stick together they become detached and can spread to other parts of the body easily. Unfortunately, this may lead to cancer cells starting to grow in other parts of the body. Cancer cells are irregular in size and shape and have many mutations. Cancer cells secrete chemicals or evade detection and are not destroyed by white blood cells. Cancer cells do not function normally, because the genes that they carry have been changed by damage or mutation.
The appearance of cancer cells if very different to normal cell. Normal cells are regular in size, have a large quantity of cytoplasm and they have a single nucleus. In contrast cancer cells are irregular in size and shape, they have a small quantity of cytoplasm and they often have many nucleoli which are often malformed.
Task two total word count- 878
Task 3a How the cell membrane controls the input of nutrients and removal of cell waste products.
The cell membrane present in animal, plant and bacteria cells is semi-permeable allowing selectively the control of substances in and out of the cell. The cell membrane is a flexible, thin barrier surrounding a cell and is comprised substantially of lipids and proteins. About 75 per cent of the cell membrane lipids are phospholipids, helping to control the flow of substances. Glycolipids, situated on the outside of the membrane, help the cell with communication and identity. Cholesterol gives the membrane structural strength and is specifically found in animal cells. Plant cells are protected by their cell wall. Phospholipid molecules in the cell membrane have hydrophobic (water repelling) tails on the inside of the cell membrane and hydrophilic (able to mix with water) heads orientated to the outside of the membrane; this positioning of these molecules makes the cells impermeable to most water-soluble molecules.
Integral proteins are proteins in the cell membrane that selectively allow the passage of materials through channels in and out of the cell. Glycoproteins are cell identity markers on the cell membrane. Peripheral proteins on the surface of the membrane help with determining the role that the cell performs.
Passive processes of the flow of molecules in and out of the cell occurs when no energy is required from the cell, for this to happen.
Simple diffusion is a passive process, which involves the movement of particles from areas of high concentration to areas of low concentration, until is equilibrium is reached.
Facilitated diffusion needs large protein carriers in the cell membrane. For example, charged irons dissolved in water could not normally passively pass through the cell membrane, because of the hydrophobic lipids in the membrane; however, they can have passage enabled through protein carrier channels.
Active processes relate to the flow of molecules through the cell membrane and requires energy from the cell, this occurs against the concentration gradient and moves molecules from areas of low concentration to areas of high concentration. Active transport processes need adenosine triphosphate (ATP) to bind to the carrier protein. ATP changes the carrier protein shape, once the ATP is bound to the carrier protein it changes into adenosine diphosphate (ADP). The change from ATP to ADP releases some energy which aids the passage of the molecule through the cell membrane. This is often used for the passage of glucose into the cell and urea as a waste product out of the cell.
Another active process is vesicular transport which transports larger molecules such as insulin using vesicles to allow osmosis. In vesicular transport larger molecules are packaged in membrane by Golgi bodies and are squeezed through the membrane by vesicles, when substances are leaving the cell, this is called exocytosis. Endocytosis occurs when substances are entering the cell, substances in vesicles can be stored in vacuoles in the cell cytoplasm.
Task 3b How animal cells use energy from nutrients for growth, movement and cell division.
Cells need energy for growth, movement and cell division. In the cell, cellular respiration creates the energy for the body to function. Some cells need more energy than others depending on their function and use, for example muscles can use lots of energy. Once food is broken down in the digestive tract, it can be used to provide the fuel for creating energy. Foods such as starch, carbohydrates and lipids are broken down into glycogen for short term storage; glycogen can then be broken down into glucose which is then transported by the blood to the cells requiring energy. In cells internal respiration takes place to create energy. Fat is made for long term energy storage of the fuel for energy.
ATP is broken down by ATPase. When ATP is broken down ADP is formed and also energy is provided for cells. ATP is made up of three phosphate groups, when one phosphate group breaks off energy and ADP is produced. ATP production and re-synthesis of ATP, takes place in a process called cellular respiration. Cellular respiration requires three stages, beginning with the breakdown of sugars through glycolysis taking place in the cell cytoplasm, two ATP molecules are made from one glucose molecule. The glucose molecule is broken down into pyruvic acid molecules. The pyruvic acid is then oxidised in the matrix of the mitochondrion, with carbon dioxide being lost.
The Krebs cycle takes place in the mitochondrial matrix of cells. Animal cells contain over 1000 mitochondria. In the Krebs Cycle pyruvate is changed to acetyl-CoA and oxygen, these are then converted to hydrogen, carbon dioxide and two ATP molecules. A running total of four ATP molecules have been produced so far, from one glucose molecule. The Electron Transport Chain also takes place in the membrane of mitochondria. Hydrogen travels into the cellular membrane; the hydrogen separates into a positively charged hydrogen ions and a negatively charged electrons. The electrons and hydrogen ions are passed on to proteins which aid the conversion of ADP back to ATP. The hydrogen ions react with oxygen producing water and 34 ATP molecules. This produces a final total of 38 ATP molecules from one glucose molecule.
Task 3 c and d. The process of manufacturing proteins and the functions of nucleic acids found in animal cells.
Proteins are long chains of the twenty different amino acids made by ribosomes within the cytoplasm of the cell. The DNA within the nucleus of a cell determines which proteins are made. The DNA in proteins is designed according to the protein’s function. The DNA molecule is a very complex structure, it is made up of monomers called nucleotides held together by phosphate and sugar molecules. The rungs of the DNA helix are made up of four nitrogen bases of the nucleotides. A gene is a section of DNA which carries the genetic code for the characteristics of a protein. The four bases are the same in all DNA, but the order of the four bases determines which genes are made. There are two types of nitrogen bases called purines, and pyrimidines. Purines include bases such as, adenine and guanine; pyrimidines include bases thymine and cytosine. These are matched together and all attached by hydrogen bonds. For example, adenine and thymine pair together also, cytosine and guanine pair together. Groups of three nucleotides form a codon, the order of codons specifies the order of amino acids within a protein. Each gene also has start and stop codons which make the beginning and end of the gene. Protein synthesis is the process by which a cell makes protein and it is based on the controlled messages within the DNA in the cell nucleus.
There are two stages of protein synthesis transcription and translation. Transcription occurs in the nucleus of eukaryotic cells. Since the DNA in the nucleus is too large to travel to the ribosomes transcription is necessary, so that the coding for genes in copied into a form that can travel to the ribosome allowing proteins to be made. During transcription, RNA polymerase breaks the bonds between the required genes for transcription. Then one of the DNA strands is used as a model to make mRNA (messenger RNA). As mRNA is very small it can then leave the nucleus and travel to the ribosomes carrying the code for protein synthesis. During transcription mRNA copies the sequence of bases for a section of DNA. Translation occurs at the ribosomes creating a polypeptide chain. The ribosome identifies the instructions correctly ordering amino acids. Transfer RNA (tRNA) is required; individual molecules of tRNA only carry one particular type of amino acid. The tRNA comprises of three nucleotides at the base, known as the anticodon. During translation the codon in the mRNA is matched with the corresponding codon in tRNA allowing synthesis of the required gene code and the production of proteins. Ribosomal RNA (rRNA) is part of a ribosome it aids in the processing of amino acids into protein chains. Ribosomes are made up of a large subunit and a small subunit with each having its own rRNA. The ribosomes translate mRNA into protein; the small subunit of a ribosome rRNA reads the order of the amino acid from the mRNA; the rRNA in the large subunit of a ribosome links amino acids together.
Task three total word count- 1410