ડાયમંડ ક્લાસ 11 ઝીન એપ્લીકેશન

Cell: The Unit of Life

• Characteristic Feature of Plant Sieve Tubes and Mammalian Erythrocytes: The common feature is the absence of mitochondria and nucleus in some cells.

• Cell Organelles: Plant cells have a cell wall, while many mammalian erythrocytes (red blood cells) lack a nucleus.

• Scientists and Their Discoveries:

  • Leeuwnhoek: First observed living cells.
  • Robert Brown: Discovered the nucleus.
  • Schleiden: All plants are composed of cells.
  • Schwann: All animals are composed of cells.

• Microtubules: Found in cilia, flagella, and centrioles; are involved in cell structure.

• Ribosomes: Composed of two subunits; forms polysomes; involved in protein synthesis.

• Glycocalyx: Can be a loose sheath (slime layer) or thick and tough (capsule) in bacteria.

• Cytoplasmic Connections: Plasmodesmata in plant cells maintain cytoplasmic continuity between adjacent cells.

• Tonoplast: The membrane-bound structure surrounding the vacuole in plant cells.

• Eukaryotic Cell Characteristics: 80S ribosomes, circular DNA in mitochondria, and membrane bound organelles are present in eukaryotic cells.

• Unicellular Organisms: These organisms cannot survive independently because they lack the complex functions of multicellular organisms.

• Cell as Fundamental Unit: Cells are essential for independent survival.

• Sizes of Cells: Mycoplasma is the smallest cell (0.3 µm), the ostrich egg is the largest, and nerve cells are quite small. Bacteria typically range from 3 to 5 µm in size.

• Prokaryotic Cell Characteristics: Smaller than eukaryotic cells, multiply faster, and include bacteria, blue-green algae, mycoplasma, and PPLO (pleuropneumonia-like organisms).

• Cell Organizational Complexity (non-achieved): Bacteriophage is a structure without organization, contrasted by organisms like Amoeba and Diatoms.

• Cell Size Arrangement: Mycoplasma, bacteria, human RBC, and ostrich egg arranged in ascending order of size.

• Bacterial Cell Envelope: Mostly a chemically simple structure with cell walls and a cell membrane.

• Bacterial Cell Envelope Components: Glycocalyx (capsule or slime layer), pili (attachment and reproduction), flagella (movement), and cell wall are typical components.

• Cell Membrane Structure: Phospholipid bilayer oriented with polar heads towards the outer environment.

• Cell Membrane Models: Fluid mosaic model best describes cell membrane structure where integral (embedded) and peripheral (outside) proteins are present.

• Cell Organelles (endomembranous system): These include the endoplasmic reticulum (ER), Golgi bodies (GB), lysosomes, and vacuoles in eukaryotes.

• Energy Transduction: Mitochondria and chloroplasts convert energy in cells.

• Cellular Function and Organelles: The many functions of organelles are integrated together to support the vital reactions for life.

• Ribosomes: Found in all cells, ribosomes are responsible for protein synthesis.

• Golgi Body Characteristics: Polarity (cis and trans faces); involved in packaging and modifying materials for transport.

• Vacuole and Tonoplast: Involved in maintaining turgor pressure and storing materials.

• Mitochondria: Double membrane structure with the inner membrane creating cristae; house DNA, RNA, and ribosomes.

• Chloroplast: Plastids responsible for photosynthesis.

• Cytoplasmic Structures: The cytoplasm is organized in eukaryotic cells through a network of membranes (endoplasmic reticulum), with organelles like the cytoskeleton.

• Types of Plastids: Leucoplasts (colorless), chromoplasts (non-green), and chloroplasts.

• Extranuclear Genes: Mitochondria and chloroplasts possess their own DNA.

• Chloroplast Number: Mesophyll cells typically have 100–1000 chloroplasts.

• Microtubules and Cilia/Flagella: Microtubules are components of cilia/flagella involved in movement.

• Nucleus Components: Chromatin condenses into chromosomes during division.

• Nuclear Membrane Characteristics: Double membrane with nuclear pores that regulate substance exchange between the nucleus and the cytoplasm.

• Ribosomes and Protein Synthesis: Ribosomes are involved in protein synthesis, with 70S ribosomes characteristic of prokaryotes, and 80S ribosomes in eukaryotes.

• Cell Wall Composition: Middle lamella (calcium/magnesium pectate) forms a connecting layer between plant cells; cell wall has components like cellulose, creating structural integrity.

• Cell Size and Types: Various organisms and cells display different sizes.

• Various Cell Components and Their Functions: A wide range of structures and organelles carry out cell functions.