eukariotic cell structure

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Eukaryotic Cells

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  • 1. Eukaryotic Cells

2. A Generalized Eukaryotic Cell 3. Pores through the Cell Nucleus 4.

  • Nucleus
  • The nucleus consists of the nuclear envelope, nucleolus, chromatin, and nucleoplasm.
  • Nuclear Envelope
  • Structure-two unit membranes with a fluid-filled space -nuclear pores present -outer membrane may be continuous with endoplasmic reticulum
  • Function-selectively permeable to control movement in or out -contains nuclear contents
  • Chromatin
  • Structure-composed of long thin strands of DNA
  • Function-contains instructions that control cell metabolism and heredity
  • Nucleolus
  • Structure-non-membraneous matrix of RNA (ribonucleic acid) and protein.
  • Function- instructions in DNA are copied here - works with ribosomes in the synthesis of protein

5. 6. Centriole Structure- nine triplets of microtubules form one centriole - two centrioles form one centrosome. Function- forms spindle fibres to separate chromosomes during cell division Vacuole Structure - a single layer of unit membrane enclosing fluid in a sack Function - produces turgor pressure against cell wall for support - stores water and various chemicals - may store insoluble wastes Cytoskeleton Structure - Composed of microtubules Function - Supports cell and provides shape - Aids movement of materials in and out of cells 7. Mitochondria

  • Power house of cell and account for 20% of the cell volume, 1 m diameter.
  • Enzymes carry out oxidative reactions that capture energy in ATP.
  • Glucose + Oxygen ------> Carbon Dioxide + Water + Energy (ATP)
  • Mitochondria contains mitochondrial DNA and can replicate independently.

8. Mitochondrial DNA 9. Chloroplasts

  • Like mitochondria chloroplast too have outer and inner membrane (stroma), it corresponds mitochondrial matrix.
  • Unlike mitochondria chloroplast have separate inner membrane (thylacoids), that contain chlorophyll (in Grana), that capture energy during photosynthesis.
  • chlorophyllCO 2+ H 2 O ---------------> Glucose + O 2(food) radiant energy
  • Chloroplast contains chloroplast DNA and can replicate independently.

10. Ribosome Structure- non-membraneous, spherical bodies composed of RNA (ribonucleic acid) and protein enzymes. Function- site of protein synthesis Endoplasmic Reticulum (ER) Structure- sheets of unit membrane withribosomeson the outside (rough ER) and without ribosome (smooth ER). - forms a tubular network throughout the cell Function - transports chemicals between cells and within cells - provides a large surface area for the organization of chemical reactions and synthesis 11. LysosomeStructure- membrane bound bag containing hydrolytic enzymes - hydrolytic enzyme = (water split biological catalyst) i.e. using water to split chemical bonds. Function- break large molecules into small molecules by inserting a molecule of water into the chemical bond Peroxisome: -Membrane bound organelle, contains enzymes.-These enzymes in plant cell oxidize fats and in animal cell oxidizes amino acids.-Peroxisomal enzymes converts hydrogen peroxide to water, to prevent the toxic effect of hydrogen peroxide. Golgi Apparatus Structure- stacks of flattened sacs of unit membrane (cisternae) - vesicles pinch off the edges Function- modifies chemicals to make them functional - secretes chemicals in tiny vesicles - stores chemicals - may produce endoplasmic reticulum 12. Prokaryotic and Eukaryotic Flagella Compared

  • One central pair and 9 peripheral pair of microtubules, made up of tubulin.
  • Each pair of peripheral microtubules associated with a protein Dynein, which cross-bridges with other flagellar proteins for movement. The movement is dependenton ATP hydrolysis by dynein.

13. Oxytricha The Ciliated Protozoan 14. The Stroke-and-Recovery Motion of a Cilium 15. Cilia on an Organism Move in a Synchronized Fashion, Creating a Wave that Propels the Organism Forward 16. Pseudopodia 17. Amoeba(132X) Amoeba engulfing food particle Food particles 18. Endosymbiosis

  • According to the endosymbiotic theory, organelles of eukaryotic cells came from prokaryotic cells those have developed symbiotic relation with eukaryote. If one organism lives inside the other, is calledendosymbiosis.
  • Especially in case of mitochondria and chloroplast. They have outer and inner membranes, self replicating DNA and their structure resembles Gram negative and photosynthetic bacteria respectively.

The cytoplasm ofPyrsonympha ,a protist that live symbiotically in the hideouts of termites,. Bacteria acts as mitochondria for the protist. 19.

  • Passive Transport: Cell expends no energy to move substances down a concentration gradient (high to low concentration)
  • Simple Diffusion
  • Facilitated Diffusion
  • Osmosis
  • Active Transport: Cell expends energy from ATP, enabling it to transport substances against a concentration gradient

Movement of substances across the membrane 20. Simple Diffusion: The random movements of molecules cause them to spread out (diffuse) from an area of high concentration to area of low concentration 21. Facilitated Diffusion: Carrier protein molecules aid in the movement of substances through cell membrane from high to low concentration 22. Osmosis: The diffusion of water from an area of high water concentration to an area of low water concentration through a semi or, selectively permeable membrane (Cell Membrane) 23. Experiments that examine the effects of tonicity on osmosis 24. Active Transport: Carrier protein molecules aid in movement of molecules against a concentration gradient requires energy in form of ATP 25. Endocytosis and Exocytosis

  • Eukaryotic cells move substances by forming membrane-enclosed vesicles
  • Endocytosis: Form by invagination (poking in) and surrounding substances from outside the cell
  • Exocytosis: Vesicles inside the cell fuse with the plasma membrane and extrude contents from the cell

26. 1.Phagocytosis (solid/ semisolid) 2. Pinocytosis (liquid)