BIOCHEMICAL ENGINEERINGLecture No. 2

Eucaryotic Cell Architecture

• Cytoplasmic Matrix:- Large part of it is water (70-85%).- The “environment” of the organelles, and location of important biochemical processes.- Cell is not "just a bag in a bubble". Lots of internal fibers = internal “skeleton”;

- Fibers include microfilaments, microtubules (e.g. form Cilia and Flagella) and Intermediate filaments.

- Cell Walls also, provide a rigid structure around cells. Made of cellulose in the case of plants and fungi.

• Endoplasmic Reticulum (ER):

- ER is a maze of parallel membranous tubules and flattened sacs surrounding the nucleus that connects with the nuclear membrane and runs throughout the cytoplasm.- ER provides a surface area for protein and lipid synthesis; - forms a pathway for transporting molecules within the cell; - provides a storage area for molecules the cell has synthesized.

- There are two distinct regions of the ER: the rough ER and the smooth ER.

- ER with ribosomes attached is called rough ER and is involved in protein synthesis, production of new membrane, modification of newly formed proteins, and transport of these proteins and membrane to other locations within the cell.

- ER without ribosomes is called smooth ER and contains enzymes for lipid biosynthesis, especially the synthesis of phospholipids and steroids.

• Golgi Apparatus:

- The Golgi apparatus (GA) consists of 3-20 flattened and stacked saclike structures called cisternae. A complex network of tubules and vesicles is located at the edges of the cisternae.- GA sorts proteins and lipids received from the ER; - modifies certain proteins and glycoproteins; and - sorts and packages these molecules into vesicles for transport to other parts of the cell or secretion from the cell.

• Lysosomes- Lysosomes, synthesized by the ER and the GA, are membrane-enclosed spheres typically about 500 nm in diameter that contain powerful digestive enzymes.- They function to digest materials that enter by endocytosis.

- Ribosomes are composed of RNA and protein

• Ribosomes:

- The ribosomes are both attached to the ER and free in the cytoplasm.

- They serve as a workbench for protein synthesis, that is, they receive and translate genetic instructions for the formation of specific proteins or polypeptides.

• Mitochondria:- Mitochondria are rod-shaped structures ranging from 2 to 8 nm in length.- Found throughout the cytoplasm; up to 20% of the cell's volume. - Mitochondria are surrounded by two membranes.- They have their own DNA and ribosomes- Frequently called the “powerhouses” of the cell- They are the centers for respiratory catabolism, during which oxygen is combined with chemicals to break down foods, and generate cell energy.

• Chloroplasts:- Chloroplasts are disk-shaped structures ranging from 5 to 10 m in length. - Like mitochondria, chloroplasts are surrounded by an inner and an outer membrane.- Use light energy to convert CO2 and water to carbohydrates and O2, that is Photosynthesis.

• Nucleus: -It is a membrane-delimited spherical body filled with dense fibrous material called chromatin.

- DNA is organized as multiple chromosomes located within a nucleus.

- The nucleus is separated from the cytoplasm by a nuclear membrane.

- The nuclear membrane has pores that connect with the ER.

- Nucleolus is the most noticeable structure within the nucleus, where ribosomal subunits are assembled.- The nucleus divides by mitosis, a process that ensures each daughter cell receives the same number of chromosomes as the original parent cell.

- Meiosis is the nuclear division that occurs as a part of sexual reproduction wherein the daughter cell receives the haploid number of chromosomes.

Commerially Important Microorganisms

Bacteria Yeast Molds Algae Viruses

Bacteria Unicellular Prokaryotic Present in three Morphological Shapes Mostly Cannot utilize light energy, Formation of endopores in adverse

conditions Can cause a vast spectrum of diseases Keeps the earth’s environment & atmosphere

in balance

Yeast Subgroup of Fungi Unable to extract energy from sunlight Fungus has complex morphology; But

yeast has existence as single small cell Path of reproduction is asexual and

sexual. Used in the production of alcoholic

beverages

Molds Have vegetative structure called

“MYCELIUM” Mycellium contains more than one cells

and have mobile mass of cytoplasm and many nuclei

Reproduction (may be sexual or asexual) is done by means of spores

Algae Have highly organized

structure Can obtain energy by

Photosynthesis Primitive Plants A large source of DO in

marine system

Viruses Does not have proper cell Structure,

only have particles of RNA, DNA in protein coating

Cause many major diseases