BIOCHEM LAB
UNIT 1: BIOCHEMISTRY and the ORGANIZATION of CELLS
BIOCHEMISTRY
• It is a multidisciplinary science that explores the chemistry of living organisms and the
molecular basis for the changes occurring in living cells.
• Basic principles of biochemistry are common to all living organisms.
• The knowledge of biochemistry can be applied to solve problems in medicine, agriculture,
environmental sciences, etc.
BIOCHEMICAL FEATURES OF LIVING ORGANISMS
A. Cells
- the basic structural and functional units of all living organisms.
- It is highly organized; a constant energy source is required to maintain a cell’s ordered state.
B. Living processes consist of thousands of chemical reactions; precise regulation and
integration of these reactions are required to maintain life.
• Certain biochemical reaction pathways, i.e. glycolysis and Krebs cycle, are found in almost
all organisms.
C. All organisms use the same type of (bio)molecules.
1. Proteins
2. Carbohydrates
3. Lipids
4. Nucleic Acids
D. The instructions for growth, development, and reproduction are encoded in each
organism’s nucleic acid.
CELL: FUNCTIONAL AND STRUCTURAL UNIT OF CELL
Types of Cells
PROKARYOTE
- “before the nucleus”
- Single-celled organisms
- Include bacteria and cyanobacteria
EUKARYOTE
- “true nucleus”
- contain a well-defined nucleus surrounded by a nuclear membrane
- can be single celled, such as yeasts and Paramecium, or multicellular, such as animals and
plants
COMPARISON OF PROKARYOTES AND EUKARYOTES
PROKARYOTIC CELL
Prokaryotes are considered as ancestor of eukaryotic cell.
• They are unicellular.
• There are two major divisions of prokaryotes: Archaebacteria (ancient class) and Eubacteria
(true bacteria).
• Escherichia coli is the most studied prokaryote.
Structure and Function:
• There are two definite membranes in a bacterial cell: the cell wall and the plasma
membrane.
• Interior of the cell consists of cytoplasm and nucleoid region.
o Ribosomes, various RNAs, proteins (including enzymes) and small
molecules (i.e. water) filled the cytoplasm.
o A bacterial chromosome is a single circular molecule of naked DNA.
• Hair-like projections (flagella and/or pili) are also present.
EUKARYOTIC CELL
• Structurally more complex
• Presence of nucleus
o Possess a number of separate chromosomes
• Filled with diverse structures
o Membrane-bound organelles
o Cytoplasmic membranes
o Other structures that lack surrounding membranes
Structure and Function
1. Cell membrane
2. Cytoplasm
o Organelles
o Cytoskeletal elements
o Cytosol
CELL MEMBRANE: Structure and Function
- It is a thin film of lipid and protein molecules held together by non-covalent interactions.
Functions:
• Define and compartmentalize the cell
• Serve as scaffold for biochemical activities
• Provide selectively permeable barrier
• Provide means of transporting solutes
• Play a role in cell-to-cell communication and detection of external signals
NUCLEUS: Structure and Function
• It is the principal feature that distinguishes eukaryotic from prokaryotic cells.
• It serves both as repository of genetic information and as the cell’s control center.
• Processes involved: DNA replication, transcription and RNA processing
MITOCHONDRION: Structure and Function
• It plays a critical role in the generation of useful energy derived from the breakdown of
lipids and carbohydrates.
• It contains their own DNA encoding for tRNA, rRNA and some mitochondrial proteins.
• Most mitochondrial proteins are synthesized on free ribosomes.
CHLOROPLAST: Structure and Function
• Can harness solar energy to convert CO2 & H2O into carbohydrates; photosynthetic
generation of ATP.
• They synthesize their own amino acids, fatty acids and lipid components of their own
membranes.
• Reduction of NO2— to NH3 also occurs in chloroplast
ENDOPLASMIC RETICULUM: Structure and Function
• It is a network of membrane-enclosed tubules and sacs that extends from the nuclear
membrane throughout the cytoplasm.
• It is the largest organelle in the cell.
• Two types: Rough and Smooth ER
ROUGH ENDOPLASMIC RETICULUM
• Consists of flattened sheets that is continuous to the outer nuclear membrane.
• Characterized by the presence of ribosomes on the cytosolic side of the membrane.
SMOOTH ENDOPLASMIC RETICULUM
• It is tubular in shape.
• It is involved in lipid metabolism.
• It is involved in several cellular processes: drug detoxification, carbohydrate metabolism and
synthesis of neutral fats, phospholipids and steroids.
GOLGI COMPLEX: Structure and Function
• It consists of a series of flattened, membranous sacs (cisternae) involved in modifying,
sorting and packaging of macromolecules for secretion or for export to other organelles.
• It is form by fusion of vesicles that bud off the ER.
LYSOSOME: Structure and Function
• It is a membrane-enclosed organelle that functions to degrade materials taken into the cell
and to digest worn out or unnecessary cell components.
• It contains about 50 different hydrolytic enzymes that can breakdown macromolecules.
PEROXISOME: Structure and Function
• It is a small, membrane-enclosed organelle that contain enzymes in variety of metabolic
reactions.
• Production and decomposition of H2O2
• Oxidative reactions of uric acid, amino acids and fatty acids.
• Synthesis of cholesterol, dolichol and bile acids in specialized cells
• In plants, glyoxylate cycle and photorespiration occurs.
CYTOSKELETON: Structure and Function
• It is a complex networks of protein filaments extending throughout the cytoplasm
• It determines cell’s shape and internal organization; responsible for the movement of the
cell.
• Three principal types of cytoskeleton:
o Microfilaments
o Intermediate filaments
o Microtubules
Centrosome and Vacuole
CENTROSOME
• It is also called the microtubule organizing center.
• Its function is to aid cellular division.
VACUOLE
• It functions as storage depots for nutrients, wastes, and specialized materials such as
pigments.
SUMMARY OF ORGANELLES AND THEIR FUNCTIONS