The document provides an overview of biochemistry as a science, discussing its evolution and applications in various life sciences fields like genetics, physiology, immunology, and pathology. It describes the biochemical unity across living organisms in terms of common macromolecules like DNA and proteins, as well as conserved metabolic processes. The document also outlines the three-domain system of classifying organisms into eukaryotes, bacteria, and archaea based on their biochemical characteristics. It concludes by comparing the structures of prokaryotic, plant, and animal cells.

1. Introduction: Biochemistry: an evolving science; Eukaryotic and prokaryotic cell structures; Functions of cellular organelles

2. Biochemistry; An evolving Science Biochemistry is the study of the chemistry of life processes. The knowledge of biochemistry can be applied to solve problems in medicine, dentistry, agriculture, forensics, anthropology, environmental sciences..etc.

3. Biochemistry; and Life Sciences Genetics; Nucleic acids, their structures, and functions constitute the core of Genetics. Physiology; Biochemistry overlaps almost completely with physiology (the study of biological processes and functions). Immunology; a science that deals with defense mechanisms against diseases, is considered a branch of Biochemistry. Pathology; Biochemistry explains, at the molecular level, the symptoms and pathogenesis of diseases. Pharmacology and Toxicology; advances in these sciences depend primarily on knowledge gained from Biochemistry as drugs and poisons are metabolized inside the body in enzyme-catalyzed biochemical reactions. Biological Sciences (microbiology, Botany and Zoology) use biochemical approaches in the study of different aspects of these sciences.

4. Biochemical unity Biochemistry is the study of the chemistry of life processes. These processes entail the interplay of two different classes of molecules. Members of these classes of molecules are common to all living organisms. Functions of such molecules are also conserved to a great extent. Large molecules (also called biological macromolecules), such as proteins and nucleic acids. Low-molecular-weight molecules (referred to as metabolites) such as glucose and glycerol.

5. Biochemical unity (Cont.) Biochemical unity underlies the common features at the biochemical level of the greatly diverse biological world. Examples include DNA, a type of macromolecule that stores genetic information in all cellular organisms. It consists of the same 4 building units in all living cellular organisms. Another example is represented by proteins, another type of macromolecules that are key participants in most biological processes. Proteins are built from a set of 20 building blocks that are the same in all organisms.

6. Biochemical unity (Cont.) Key metabolic processes, such as the chemical conversion of glucose and oxygen to CO2 and water as part of energy production mechanism in living organisms, are essentially the same in all living organisms from bacteria through human. Normal Biochemical Processes are the basis of health. Any deviation from normal biochemical processes results in a disease condition. In addition, biochemical investigations and laboratory tests contribute to the diagnosis and treatment of many diseases.

7. Biochemical unity (Cont.) On the basis of the biochemical characteristics, the diverse organisms can be divided into three fundamental groups (three-domain classification system): Eukarya (or Eukaryotes), bacteria and Archaea.

8. The Three-domain System Eukaryotes include unicellular organisms such as yeast in addition to all multi-cellular organisms. They are characterized by the presence of a well-defined nucleus within each cell. On the other hand, bacteria (also known as prokaryotes) are unicellular organisms that lack nuclei. Archaea constitute a separate group between the two classes, resembling bacteria in many aspects of cellular structure and metabolic processes, while follow the path of eukaryotes in the processes dealing with the flow of genetic information through generations.

9. Prokaryotic / Bacterial cell

10. Eukaryotic cell (Plant cell)

11. Eukaryotic cell (Plant cell) A large central vacuole (enclosed by a membrane, the tonoplast ), which maintains the cell's turgor and controls movement of molecules between the cytosol and sap A cell wall made up of cellulose and protein , and in many cases lignin , and deposited by the protoplast on the outside of the cell membrane ; this contrasts with the cell walls of fungi , which are made of chitin , and prokaryotes , which are made of peptidoglycan The plasmodesmata , linking pores in the cell wall that allow each plant cell to communicate with other adjacent cells; this is different from the network of hyphae used by fungi Plastids , especially chloroplasts that contain chlorophyll , the pigment that gives plants their green color and allows them to perform photosynthesis Plant groups without flagella (including conifers and flowering plants ) also lack centrioles that are present in animal cells .

12. Eukaryotic cell (Animal cell)

13. Comparison of structures between animal and plant cells Typical animal cell Typical plant cell Organelles Nucleus Nucleolus (within nucleus) Rough endoplasmic reticulum (ER) Smooth ER Ribosomes Cytoskeleton Golgi apparatus Cytoplasm Mitochondria Vesicles Lysosomes Centrosome Centrioles Vacuoles Nucleus Nucleolus (within nucleus) Rough ER Smooth ER Ribosomes Cytoskeleton Golgi apparatus ( dictiosomes ) Cytoplasm Mitochondria Vesicles Chloroplast and other plastids Central vacuole (large) Tonoplast (central vacuole membrane) Peroxisome (e.g. Glyoxysome ) Vacuoles Additional structures Plasma membrane Flagellum Cilium Plasma membrane Flagellum (only in gametes) Cell wall Plasmodesmata