The Animal Cell

Asst. Professor um MVPs Institute of Pharmaceutical Sciences,Nashik
2. Jan 2023

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The Animal Cell

  1. ANIMAL CELL Prof. Amol B. Deore Department of Physiology MVP’S Institute of Pharmaceutical Sciences, Nashik
  2. • The cell is the smallest structural, functional, and biological unit of all living organisms which can capable of biosynthesis, replication and energy transformation. • They are often called the ‘building blocks of life’. The cell
  3. Cytology is the scientific study of cellular structure and function. Organisms can be classified as unicellular (consisting of a single cell; including bacteria) or multicellular (including plants and animals). While the number of cells in plants and animals varies from species to species, Humans contain about 100 trillion (1014) cells.
  4. All cells arise from existing cells by the process of cell division, in which one cell divides into two identical cells. Different types of cells fulfil unique roles that support homeostasis and contribute to the many functional capabilities of the human organism.
  5. Most plant and animal cells are visible only under the microscope, with dimensions between 1 and 100 µm. Animal cell contains membrane bound nucleus, it also contains other membrane bound cellular organelles. These cellular organelles carry out specific functions that are necessary for the normal functioning of the cell.
  6. PLASMA MEMBRANE • A biological membrane that surrounds the cytoplasm of a cell. In short, it is the outer boundary of the cell. • It is a thin, elastic structure about 7.5 to 10 nm in thickness. • It separates the internal environment (inside the cell) from the external environment (outside the cell). • The plasma membrane is made up of lipid bilayer, which contains lipid molecules— phospholipids, cholesterol, and glycolipids.
  7. The plasma membrane is said to be 'semi-permeable'. Semi-permeable means that the membrane allows some materials to pass while excluding others. Lipid soluble substances and gasses such as oxygen and carbon dioxide can easily pass through the phospholipids. Water soluble substances such as glucose and charged molecules such as ions, however, are unable to pass through the lipid bilayer. These hydrophilic molecules and ions must use transfer proteins within the membrane to pass into or out of the cell.
  8. Two different types of proteins that are embedded in the cell membrane are the integral proteins and peripheral protein. A transport protein (channel) is an example of an integral protein that selectively allows particular materials, such as certain ions, to pass into or out of the cell. Another important group of integral proteins are cell recognition proteins, which serve to mark a cell’s identity so that it can be recognized by other cells.
  9. A receptor is a type of recognition protein that can selectively bind a specific molecule outside the cell, and this binding induces a chemical reaction within the cell. Some integral membrane proteins are glycoproteins. A glycoprotein is a protein that has carbohydrate molecules attached, which help in cell-to-cell recognition.
  10. FUNCTIONS • The membrane allow the passage of different nutrients and electrolyte ions into and out of a cell. • The plasma membrane also plays a vital role in communication between cells to cells. • Plasma membranes also contain proteins that allow cells to detect external signalling molecules such as hormones.
  11. CYTOPLASM • The intracellular substance in which all cell organelles are suspended is known as cytoplasm. • Cytoplasm is a viscous, transparent, gel like semisolid fluid containing 75-90% water, proteins, carbohydrates, lipids, organic substances including amino acids, sugars polysaccharides and inorganic substances such as mineral ions.
  12. Nucleus • The nucleus is the largest and most prominent of a cell’s organelle. • The nucleus is generally considered the control center of the cell because it stores all of the genetic instructions for manufacturing proteins.
  13. The nucleus is surrounded by a double membrane called the nuclear envelope. This envelope consists of lipid bilayers with a thin fluid space called nuclear pore. A nuclear pore is a tiny passageway for the passage of proteins, RNA, and solutes between the nucleus and the cytoplasm.
  14. Inside the nuclear envelope is a gel-like nucleoplasm with solutes that include the building blocks of nucleic acids. The nucleolus is a region of the nucleus that is responsible for manufacturing the RNA necessary for production of ribosomes. Once synthesized, newly made ribosomal subunits exit the cell’s nucleus through the nuclear pores. The genetic instructions that are used to build and maintain an organism are arranged in an orderly manner in strands of DNA. Within the nucleus are threads of chromatin composed of DNA and associated proteins.
  15. ENDOPLASMIC RETICULUM • The endoplasmic reticulum (ER) is an extensive network of membranous tubules that extend from the nuclear envelope to the cell membrane. • The ER provides passages throughout the cell for transporting, synthesizing, and storing materials. It serves as a mini circulatory system for the cell. • Endoplasmic reticulum can exist in two forms: rough ER and smooth ER. • These two types of ER perform different functions and can be found in very different amounts depending on the type of cell.
  16. Rough ER • Rough ER is dotted with embedded granules called ribosomes, which are sites of protein biosynthesis. The cavities of the rough ER work in the separation and transport of these proteins. Smooth ER • Smooth ER does not contain ribosome. It performs biosynthesis of steroidal hormones, sex hormones, digestive enzymes, fatty acids, phospholipids, triglycerides and cholesterol. • In addition, the smooth ER also stores and regulates the concentration of cellular Ca+2, a function extremely important in nerve cells. • Additionally it metabolizes some carbohydrates and carry out detoxification certain toxins in the liver
  17. Ribosomes • A ribosome is the site of protein synthesis. It can be found free floating in the cytoplasm or attached to the rough ER. It is composed of two ribosomal RNA subunits that wrap around mRNA to start the process of translation, a stage of protein synthesis. • Protein synthesis consists of two main stages: transcription and translation. • Transcription occurs within the nucleus and is a phase of proteins synthesis in which mRNA is copied from DNA. The mRNA leaves the nucleus through nuclear pores and goes to the ribosome.
  18. The ribosome then “reads” or interprets the instructions within mRNA and uses transfer RNA (tRNA) to link amino acids in the appropriate order to produce a protein. Typically, a protein is synthesized within the ribosome and released inside the channel of the rough ER, where sugars can be added to it (by a process called glycosylation) before it is transported within a vesicle to the next stage in the packaging and shipping process: the Golgi apparatus.
  19. Golgi apparatus • Golgi apparatus is a membrane-bound organelle, which is mainly composed of a series of flattened, stacked pouches (look like pancakes) called cisternae. It is located in the cytoplasm next to the endoplasmic reticulum. It is primarily responsible for sorting, modifying, packaging and transporting of proteins and lipids to targeted areas of the cell.
  20. (Cis face) (Trans face)
  21. The Golgi apparatus has two distinct ends: the cis face and the trans face of Golgi network, each has a different function. The cis face receives products from transport vesicles. These products are sorted through the Golgi apparatus, and then they are released from the trans face after being repackaged into new secretory vesicles.
  22. functions of Golgi apparatus • sorting, modifying, packaging and transporting of proteins and lipids to targeted areas of the cell and some are exported from the cell through exocytosis. • Proteins formed by ribosomes are stored in the secretory vesicles of Golgi apparatus. • The secretory vesicles of Golgi apparatus are composed of enzymatic proteins further develop in to lysosomes. • Synthesis of glycolipids etc
  23. Mitochondrion • Mitochondria are bean-shaped organelles that can be considered the power houses of the cell, converting oxygen and nutrients into adenosine triphosphate (ATP). The number of mitochondria present in a cell depends upon the metabolic requirements of that cell. • There are about 1600-2000 mitochondria present in liver cells, muscle cells, kidney, however sperm cells contain only 20-24. • The outer membrane and the inner membrane are made of proteins and phospholipid layers separated by the intermembrane space.
  24. The outer membrane covers the surface of the mitochondrion and has a large number of special proteins known as porins. The inner membrane has numerous folds called cristae, and this helps in increasing the surface area inside the organelle. The mitochondrial matrix is a viscous fluid that contains a mixture of enzymes and proteins. It also comprises ribosomes, inorganic ions, mitochondrial DNA, nucleotide cofactors, and organic molecules. The proteins and enzymes present in the matrix play an important role in the synthesis of ATP molecules.
  25. The important functions of mitochondria are • Produce energy through the process of oxidative phosphorylation • Regulates the metabolic activity of the cell • Promotes the growth of new cells and cell multiplication • Apoptosis or programmed cell death • It is also involved in various cellular activities like cellular differentiation, cell signalling, cell senescence, controlling the cell cycle and also in cell growth.
  26. The cellular respiration can be stated as follows: Food (like glucose) + oxygen Energy + waste+ water C6H12O6 + 6O2 ATP + 6CO2 + 6H2O Most of the energy-producing reactions, which occur in the mitochondria, take place on the surface of the cristae. For this reason, the mitochondria are known as the powerhouses of the cell.
  27. Lysosome • The Golgi apparatus releases secretory vesicles which further converted into new lysosomes. A lysosome is an organelle that contains enzymes that break down and digest unneeded cellular components, such as a damaged cell organelle.
  28. Lysosomes are involved with various cell processes. They break down excess or worn-out cell parts. They may be used to destroy invading viruses and bacteria. If the cell is damaged beyond repair, lysosomes can help it to self- destruct in a process called programmed cell death, or apoptosis. Hence lysosomes are referred as suicidal bags.