Cell Organelles: Golgi Bodies Quiz

Cell: Structure and Function

• Cell is the fundamental unit of life, self-replicating, and can be unicellular or multicellular.
• First cells were observed by Robert Hooke in 1665 from a slice of cork, with a diameter of 2-120µm.

Cell Theory

• Proposed by Matthias Schleiden and Theodor Schwann in 1839:
  • All living things are made up of cells.
  • Cells are the smallest working unit of all living things.
  • All cells come from pre-existing cells through cell division.

Protoplasm

• Composed of:
  • Water (70-80%)
  • Carbohydrates
  • Lipids
  • Proteins
  • Electrolytes (Sodium, Potassium, Magnesium, Calcium, Phosphate, Chloride, and Bicarbonate)

Cell Membrane

• Thin elastic outermost structure that envelops the cell.
• Consists of bilipid layer with embedded proteins: integral proteins and peripheral proteins.

Functions of Cell Membrane

• Protective: forms outermost boundary of the cell organelles.
• Digestive: takes in food and excretes waste products.
• Selective Permeability: allows non-polar molecules to dissolve and move rapidly across the membrane, while polar molecules have lower solubility.

Cytoplasm

• Thick, gel-like semitransparent fluid found in both plant and animal cells.
• Constituent parts: cytosol, cell organelles, and cytoplasmic inclusions.
• Bounded by the plasma membrane and contains many organelles in a eukaryotic cell.

Mitochondria

• First observed by Kolliker in 1850 as granular structures in the striated muscles.
• Called the 'powerhouse of the cell'.

Endoplasmic Reticulum

• Network of tubular and flat vesicular structures in the cytoplasm.
• Extensive network of closed, flattened membrane-bounded sacs called cisternae.
• Space inside the tubules is filled with Endoplasmic Matrix.

Types of Endoplasmic Reticulum

• Smooth Endoplasmic Reticulum: site of synthesis of lipid and steroid hormones.
• Rough Endoplasmic Reticulum: site of protein synthesis, processing, and packaging.

Golgi Bodies

• Collection of membrane-enclosed sacs composed of four or more stacked layers of thin, flat enclosed vessels.
• Consist of multiple discrete compartments.
• Functions:
  • Wrapping and packaging department of the cell.
  • Site of formation of lysosomes.
  • Adds certain carbohydrates to form glycoproteins.

Lysosome

• Irregular structures surrounded by the unit membrane.
• Acts as a form of digestive (lytic) system or the cell.
• Engulf worn out components of the cells in which they are located.
• When a cell dies, lysosomal enzymes cause autolysis of the remnant.

Peroxisome

• Lipid bilayer membrane surrounds which regulates what enters or exits the peroxisomes.
• Structure is similar to that of the lysosomes but with a different composition.
• Functions: H2O2 metabolism and detoxification.

Cytoskeleton

• System of fibers that maintains the structure of the cell and permits it to change shape and move.
• Made up primarily of:
  • Microtubules
  • Intermediate Filaments
  • Microfilaments

Cytoskeleton Components

• Microtubules: long hollow structures that determine the shape of the cell, role in the contraction of the spindle and movement of chromosomes and centrioles.
• Intermediate Filaments: flexible scaffolding or cell, help it resist external pressure.
• Microfilaments: long solid fibers responsible for the cell motion.

Nucleus

• Contains chromatin, RNAs, and nuclear proteins that move freely in aqueous solution.
• Has an internal structure that organizes the genetic material and localizes nuclear functions.
• Serves both as the repository of genetic information and as the cell's control center.