Eukaryotic cells

Common Features
1. Membrane delimited nuclei
2. Membrane-bound organelles that perform specific functions
3. Intracytoplasmic membrane complex serves as transport system
4. More complex and larger than Bacterial or Archaeal cells
Flagella and Cilia
1. Locomotion or Move substances along cell surface
2. Enclosed by Plasma Membrane
3. Contain Cytoplasm
4. 9 rings of Microtubule in a ring and 2 single Microtubule in center
5. Flagella: LOng whip-like projections
6. Cilia: Short hair-like Projections
Cell wall
1. Lack of External cell wall
2. Protozoa have a flexible outer layer called PELLICLE instead of cell wall
3. Animal cells have a sticky glycocalyx surrounding the cell membrane
4. Importnat for attachment,Strength and Cell-Cell recognition
5. Cell wall is chemically simpler and lack Peptidoglycan
6. Composition
  1. Algae and Plants: Cellulose
  2. Fungi: Chitin
  3. Yeasts: Glucan and Mannan
Cell Membrane
1. Similar to Prokaryotic cell membrane
2. Different Membrane Proteins
3. Contain Carbohydrate (Important for cell-cell recognition and serve as sites for Bacterial attachment)
4. Contain Sterols which increase resistance to osmotic lysis
Ribosomes
1. Site of Protein synthesis(Translation)
2. Found in all eukaryote and Prokaryote cells
3. Made of Protein and Ribosomal RNA (rRNA)
4. May be found free in cytoplasm or associated with the rough endoplasmic reticulum (RER)
5. Eukaryotic ribosomes (80S) are larger and more dense than Prokaryotic ribosomes (70S)
6. Two subunits
  1. Small Subunit: 40S
  2. Large Subunit: 60S
Golgi Apparatus
1. Sacks of flattened membrane sacs that may be distended in certain regions. Sacs are not interconnected.
2. First described in 1898 by camillo Golgi
3. Works closely with the ER to secrete proteins
4. Functions
  1. Receiving side (receives Proteins in transport vesicles from ER)
  2. Modifies Proteins into final shape, sorts and labels them for proper transport
  3. Shipping side- Packages and sends proteins to cell membrane (export) or other parts
  4. Packages digestive enzymes in Lysosomes
Lysosomes
1. Released from Golgi
2. Contains at least 4 different digestive enzymes
3. Optimal PH is about five
4. Found mainly in animal cells
5. Functions
  1. Molecular garbage dump
  2. Recycles macromolecules
  3. Destruction of foreign material
  4. Digestion of food particles taken in by cell
  5. after cell dies lysosomal membrane breaks down causing rapid self-destruction
  6. Contain digestive enzymes used to break down various molecules
  7. Can digest any bacteria that enters the cell
Vacuoles
1. Central Vacuole
  1. In Plants cells
  2. Store starch, Water, Pigments, Poisons and wastes
  3. May occupy up to 90% of plant cell
2. Contractile Vacuole
  1. Regulate water balance by removing escess water from cell
  2. Found in many aquatic prosites
3. Food or Digestion Vacuole
  1. Engulf nutrients in many protozoa (protists)
  2. Fuse with lysosomes to digest food particles
Other Organelles
1. Peroxisomes
  1. Oxidation of Organic substances
  2. Decompose H2O2 (Catalase)
  3. Oxidize toxic substances
2. Centrosome
  1. Pericentriolar
  2. Centrioles
Chloroplasts
1. Site of Photosynthesis in plants and algae
  1. CO2 + H2O + Sun Light
  2. Sugar + O2
2. Number in Range may range from 1 to over 1000
3. Disc shaped, with three membrane systems
Mitochondria
1. Rod shaped Organelles
2. Central role in ATP production through the degradation of organic compounds
3. Site of cellular respiration
  1. Food(Sugar) + O2
  2. CO2 + H2O +ATP
4. Changes Chemical energy of molecule to ATP
5. Oval or sausage molecule
6. Contain
  1. Their own DNA
  2. 70S ribosomes
7. Make some Proteins
8. Can devide to form daughter mitochondria
9. Structure
  1. Inner/outer membrane
  2. Inter membrane space
  3. Cristae
  4. Matrix (inner liquid)
Cytoplasm
1. Many enzymes are sequestered in organelles
2. Contains the cytoskeleton (A complex network of thread and tube-like structures, Provides support, shape and movement)
3. Cytoskeleton components
  1. Micro filaments
    1. Smallest Fibers action protein
    2. Amoeboid motion of white blood cells
  2. Intermediate Filaments
    1. Anchor organelles (nucleus) and hold cytoskeleton in place
    2. Abundant in cells with high mechanical stress
  3. Microtubules
    1. Largest Fibers
    2. Work in cell division
    3. Moving Chromosomes
    4. Flagella and ciliary movement
Nucleus
1. Structure
  1. Envelope: Double nuclear membrane
  2. Nuclear pores
  3. DNA (Genetic Material) combined with Histones
    1. Chromatin (Loose, Thread-like DNA. Most of the cell life)
    2. Chromosomes (Tightly packaged DNA. Found only during cell division)
  4. Nucleoli: Dense region where ribosomes are made
2. Functions
  1. House and protect cell's DNA
  2. Ribosome synthesis
    1. Mastermind of the eukaryotic cell
    2. Usually the largest structure of the cell
Mitosis
1. Body prepares for Asexual reproduction or cell maintenance
2. Replacement of Old cells with New cells
3. produces two daughter cells that are identical to the parent cell
4. Allows multicellular organisms to grow and repair damaged tissue
5. Phases
  1. Interphase
    1. Chromosomes not visible (uncoiled)
  2. Prophase
    1. The chromosomes coil
    2. The nuclear membrane disintegrates
    3. Spindle fibres (microtubule) form
  3. Metaphase
    1. Chromosomes become aligned
  4. Anaphase
    1. Chromatids separate (chromosomes double up)
  5. Telophase
    1. Cell divides into two
    2. Chromosomes uncoil
    3. The nucleus reforms
    4. The spindle apparatus disassembles
  6. G1 Interphase
    1. Chromosomes have one chromatid
  7. G2 Interphase
    1. Chromosomes have two chromatid each
Miosis
1. Producing daughter cells with half number of chromosomes as the parent cell
2. Used in reproducing sexually
3. Gametes (Sperm and eggs) are haploid
4. Produces four daughter cells
5. In animals, meiosis occurs only when gametes are formed
6. In plants gametes are not produced directly. Meiosis produces spores and then mitosis produces Gametes
7. Involves 2 divisions
  1. Meiosis1
    1. Number of cells doubled but number of chromosomes don't change (1/2 as many chromosomes per cell)
      1. Prophase1
      2. Events similar to Prophase of mitosis
      3. Chromosomes produce tetrads
      4. The two chromosomes may exchange fragments(Crossing over)
      5. Metaphase1
      6. Tetrads become aligned in the center of the cell and attach to spindle fibres
      7. Anaphase1
      8. Separation of homologous
      9. Telophase1
      10. Nuclear envelope reforms
      11. Two cells formed
      12. each cell has 4 chromosomes
  2. Meiosis 2
    1. like mitosis, The number of chromosomes don't reduce
      1. Prophase2
      2. Metaphase2
      3. Anaphase2
      4. Telophase2
Endoplasmic Reticulum (ER)
1. Network of flattened membranous tubules within the cell
2. Extensive maze of membranes that branches throughout the cytoplasm
3. continuous with plasma membrane and outer nucleus membrane
4. Types
  1. Rough Endoplasmic Reticulum (RER)
    1. Flat, Interconnected, Rough membrane sacs
    2. Rough: Outer walls are covered with Ribosomes
    3. Ribosome may exist free or attached to RER
    4. Functions
      1. Synthesis and Modification of Proteins
      2. Synthesis of cell and organelles membranes
  2. Smooth Endoplasmic Reticulum (SER)
    1. Network of interconnected tubular smooth membranes
    2. Smooth: No ribosomes
    3. Functions
      1. Lipid synthesis
      2. Phospholipids
      3. Fatty acids
      4. Steroids (sex hormones)
      5. Breakdown of toxic compounds
      6. Drugs
      7. Alcohol
      8. amphetamines
      9. Sedatives
      10. Antibiotics, etc
      11. Helps develop tolerance to drugs and alcohol