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Ultra structure of plant cell (2)

  1. Ultra structure of plant cell (PART II) Pillai Aswathy Viswanath Dept. of Botany Assumption College Chenganacherry
  2. Dictyosome • Dictyosomes are stacks of flat, membrane- bound cavities (cisternae) that together comprise the Golgi apparatus.
  3. • Dictyosomes in animal cells are stacked tightly together called Golgi apparatus • Plant cells contain smaller Golgi Apparatus type vesicles, which are called dictyosomes. • The dictyosomes in plant cells are dispersed in the cytoplasm, making them difficult to identify as the Golgi apparatus. • Within the dictyosomes, proteins are stored, modified, sorted, and packed into for further transport.
  4. function • The proteins are synthesized on the rough endoplasmic reticulum and arrived in the vesicles of Golgi Apapratus. • In the vesicles of Golgi apparatus, the proteins are processed and sorted for future secretion, storage, transport etc.
  5. Lysosomes • “Lysosomes are sphere-shaped sacs filled with hydrolytic enzymes . • Lysosomes are membrane-bound organelles and the area within the membrane is called the lumen, which contains the hydrolytic enzymes and other cellular debris. • The pH level of the lumen lies between 4.5 and 5.0, which makes it quite acidic.
  6. Lysosome function • lysosomes are membranous organelles whose specific function is to breakdown cellular wastes and debris by engulfing it with hydrolytic enzymes. • Cellular debris or foreign particles are pulled in to the cell through the process of endocytosis.
  7. • The process of endocytosis happens when the cell membrane falls in on itself (invagination), creating a vacuole or a pouch around the external contents and then bringing those contents into the cell. • On the other hand, discarded wastes and other substances originating from within the cell is digested by the process of autophagocytosis or autophagy.
  8. Why are Lysosomes known as Suicidal Bags? • lysosomes work as the waste discarding structures of the cell and degrading them, both from the exterior of the cell and waste constituents inside the cell. • But sometimes, the digestive enzymes may end up damaging the lysosomes themselves, and this can cause the cell to die. • This is termed as autolysis, where “auto” means “self” and “lysis” means “the disintegration of the cell by the destruction of its cell membrane“. • Hence, lysosomes are known as “Suicidal Bags” of the cell.
  9. Microbodies • A microbody is usually a vesicle with a spherical shape, ranging from 0.2-1.5 micrometres in diameter. • The microbodies are found in the cytoplasm of a cell • They are surrounded by a single phospholipid bilayer membrane and they contain a matrix of intracellular material including enzymes and other proteins, • but they do not seem to contain any genetic material to allow them to self-replicate.
  10. • Microbodies facilitates the breakdown of fats, alcohols and amino acids. Different types of microbodies have different functions: • Peroxisome is a type of microbody that functions to help the body break down large molecules and detoxify hazardous substances. • Glyoxysomes are specialized peroxisomes found in plants , which help to convert stored lipids into carbohydrates so that they can be used for plant growth.
  11. Vacuole and cell sap • The vacuole is a type of organelle present in eukaryotic cells. • It is a sac surrounded by a single membrane called a tonoplast.
  12. • Both plant and animal cells can contain vacuoles, but vacuoles are far more prevalent in plant cells. • They are also much larger in plant cells and often take up a great deal of space within the cell. • Animal cells do not always have a vacuole, and most never have a large vacuole, because it would cause harm to the cell and disrupt the functioning of the rest of the cell. • Animal cells may instead have several very small vacuoles.
  13. • Vacuoles in animal cells are small and spend most of their time providing transportation into and out of the cell for various organic materials. • There are two kinds of transportation that the vacuoles provide: exocytosis endocytosis
  14. • Exocytosis is the method by which vacuoles move materials out of the cell. • These materials are often unwanted materials such as waste, or molecules • Endocytosis is the inverse process of exocytosis, in which vacuoles help to bring organic matter into the animal cell.
  15. • Plant cells commonly contain one large vacuole that fills more space within the cell than any other organelle. • The plant cell vacuole consists of tonoplast, which forms a sac around a fluid called cell sap. • Cell sap contains water and a number of other substances. These can include: Salts Enzymes Sugars and other carbohydrates Lipids Ions
  16. • The concentration of ions in the cell sap is a useful tool for moving water in and out of the vacuole via osmosis. • If the ion concentration is higher within the vacuole, water moves through the tonoplast into the vacuole. • If the ion concentration is higher in the cytoplasm outside of the vacuole, water moves out of the vacuole. • The vacuole enlarges or shrinks as water moves into or out of it.
  17. Nucleus • The nucleus is a double-membraned organelle that contains the genetic material. • It is exclusively found in eukaryotic cells • Parts Of The Nucleus: Nuclear Envelope Nuclear Pores Nucleoplasm Chromatin Nucleolus
  18. Structure Of Nucleus • It is generally the most prominent organelle in the cell. • The nucleus is completely bound by membranes. • It is surrounded by a structure called the nuclear envelope. • The nuclear envelope is a double-layered membrane that contains all the parts of the nucleus and separates it from the cytoplasm of the cell.
  19. • The nuclear envelope is full of holes called nuclear pores, which allow molecules to move in and out of the nucleus. • nucleopore allows proteins and nucleic acids to pass through • This membrane separates the contents of the nucleus from the cytoplasm. • The cell’s chromosomes are also enclosed within it. • DNA is present in the Chromosomes and they provide the genetic information of life.
  20. • The nucleoplasm is a jelly-like substance that is found within the nuclear envelope, and its function is similar to the cytoplasm found in the main cell, supporting the nucleus and protecting its contents. • Finally, the nucleolus is the largest structure found in the nucleus. • It is very dense, has no membrane, and is composed of chunks of protein and RNA. • In nucleolus, ribosome biogenesis happens here.
  21. Function OF Nucleus • The nucleus has been clearly explained as a membrane-bound structure that comprises the genetic material of a cell. • It contains the cell’s hereditary information and controls the cell’s growth and reproduction. • It is not just a storage compartment for DNA but also happens to be the home of some essential cellular processes. • First and foremost, it is possible to duplicate one’s DNA in the nucleus
  22. • This process has been named DNA Replication and creates an identical copy of the DNA. • Secondly, the nucleus is the spot of transcription. • Transcription is the process of creating different types of RNA from DNA.
  23. • Chromatin is a complex of DNA and protein found in eukaryotic cells. • Its primary function is packaging long DNA molecules into more compact, denser structures. • This prevents the strands from becoming tangled
  24. DIFFERENCE • Animal cells and plant cells are similar in that they are both eukaryotic cells. • These cells have a true nucleus, which houses DNA and is separated from other cellular structures by a nuclear membrane.
  25. • Both of these cell types also contain cell structures known as organelles, which are specialized to perform functions necessary for normal cellular operation. • Animal and plant cells have some of the same cell components in common including a nucleus, Golgi complex, endoplasmic reticulum, ribosomes, mitochondria, peroxisomes , cytoskeleton, and cell (plasma) membrane.
  26. Size • Animal cells are generally smaller than plant cells. • Animal cells range from 10 to 30 micrometers in length, • While plant cells range from 10 and 100 micrometers in length. Shape • Animal cells come in various sizes and tend to have round or irregular shapes. • Plant cells are more similar in size and are typically rectangular or cube shaped.
  27. Cell Wall • Animal cells do not have a cell wall but have a cell membrane. • Plant cells have a cell wall composed of cellulose as well as a cell membrane. Glyoxysomes • These structures are not found in animal cells but are present in plant cells. • Glyoxysomes help to degrade lipids, particularly in germinating seeds.
  28. Lysosomes • Animal cells possess lysosomes which contain enzymes that digest cellular macromolecules. • Plant cells rarely contain lysosomes Plastids • Animal cells do not have plastids. • Plant cells contain plastids such as chloroplasts, which are needed for photosynthesis
  29. Plasmodesmata, • Animal cells do not have plasmodesmata. • Plant cells have which are pores between plant cell walls that allow molecules and communication signals to pass between individual plant cells. Vacuole • Animal cells may have many small vacuoles. • Plant cells have a large central vacuole that can occupy up to 90% of the cell's volume. • The plant vacuole handles molecule degradation
  30. Energy Storage • Animals cells store energy in the form of the complex carbohydrate glycogen. • Plant cells store energy as starch. Proteins • Of the 20 amino acids needed to produce proteins, only 10 can be produced naturally in animal cells. • The other so-called essential amino acids must be acquired through diet. • Plants are capable of synthesizing all 20 amino acids.
  31. • Both of these cell types have similar processes for reproduction, which include mitosis and meiosis. Centrioles • Animal cells contain these cylindrical structures that organize the assembly of microtubules during cell division. • Plant cells do not typically contain centrioles.