Introduction to Biochemistry

• Biochemistry is the study of the chemical processes in living organisms.
• It deals with the structure, function, and interactions of biological molecules such as proteins, nucleic acids, carbohydrates, and lipids.
• Biochemistry is essential for understanding the molecular basis of life and disease.
• It provides the foundation for various fields such as medicine, pharmacology, nutrition, and biotechnology.

Basic Concepts in Biochemistry

• Biomolecules are organic molecules present in living organisms.
• The four major classes of biomolecules are carbohydrates, lipids, proteins, and nucleic acids.

Carbohydrates

• Carbohydrates are the primary source of energy for living organisms.
• They consist of carbon, hydrogen, and oxygen atoms, usually in a ratio of 1:2:1.
• Monosaccharides are the simplest carbohydrates, such as glucose, fructose, and galactose.
• Disaccharides are composed of two monosaccharides linked together, such as sucrose (glucose + fructose) and lactose (glucose + galactose).
• Polysaccharides are complex carbohydrates made up of many monosaccharides, such as starch, glycogen, and cellulose.
• Starch is the storage form of glucose in plants.
• Glycogen is the storage form of glucose in animals.
• Cellulose is a structural component of plant cell walls.

Lipids

• Lipids are hydrophobic molecules that include fats, oils, phospholipids, and steroids.
• They are important for energy storage, insulation, and cell membrane structure.
• Triglycerides (fats and oils) are composed of glycerol and three fatty acids.
• Saturated fatty acids contain only single bonds between carbon atoms.
• Unsaturated fatty acids contain one or more double bonds between carbon atoms.
• Phospholipids are major components of cell membranes with a hydrophilic head and hydrophobic tails.
• Steroids are lipids with a characteristic four-ring structure, such as cholesterol and hormones.

Proteins

• Proteins are complex molecules composed of amino acids.
• They perform a wide range of functions, including catalysis, transport, structure, and defense.
• Amino acids are organic molecules containing an amino group, a carboxyl group, a hydrogen atom, and a unique side chain (R group).
• There are 20 common amino acids found in proteins, each with a different R group.
• Peptide bonds link amino acids together to form polypeptide chains.
• The primary structure of a protein is the sequence of amino acids.
• The secondary structure refers to local folding patterns such as alpha-helices and beta-sheets.
• The tertiary structure is the overall three-dimensional shape of a protein.
• The quaternary structure involves the arrangement of multiple polypeptide chains in a protein complex.

Nucleic Acids

• Nucleic acids store and transmit genetic information.
• The two types of nucleic acids are DNA (deoxyribonucleic acid) and RNA (ribonucleic acid).
• Nucleotides are the building blocks of nucleic acids, consisting of a sugar, a phosphate group, and a nitrogenous base.
• DNA contains the sugar deoxyribose, while RNA contains the sugar ribose.
• The nitrogenous bases in DNA are adenine (A), guanine (G), cytosine (C), and thymine (T).
• The nitrogenous bases in RNA are adenine (A), guanine (G), cytosine (C), and uracil (U).
• DNA is a double-stranded helix with complementary base pairing (A with T, and G with C).
• RNA is typically single-stranded and involved in protein synthesis.

Enzymes

• Enzymes are biological catalysts that accelerate chemical reactions in living organisms.
• They are typically proteins and highly specific for their substrates.
• Enzymes lower the activation energy of a reaction, making it proceed faster.
• The active site is the region of an enzyme where the substrate binds and the reaction occurs.
• Enzyme activity can be affected by factors such as temperature, pH, and the presence of inhibitors or activators.

Metabolism

• Metabolism is the sum of all chemical reactions that occur within a living organism.
• It includes catabolism (the breakdown of complex molecules) and anabolism (the synthesis of complex molecules).
• Catabolic pathways release energy, while anabolic pathways require energy.
• ATP (adenosine triphosphate) is the main energy currency of the cell, providing energy for various cellular processes.
• Glycolysis is the breakdown of glucose into pyruvate, producing ATP and NADH.
• The citric acid cycle (Krebs cycle) is a series of reactions that oxidize acetyl-CoA, producing ATP, NADH, and FADH2.
• Oxidative phosphorylation is the process by which ATP is generated from NADH and FADH2 through the electron transport chain and chemiosmosis.

Cell Structure and Function

• The cell is the basic structural and functional unit of living organisms.
• Eukaryotic cells have a nucleus and other membrane-bound organelles, while prokaryotic cells do not.
• The plasma membrane encloses the cell and regulates the passage of substances in and out.
• The nucleus contains the cell's DNA and controls gene expression.
• Mitochondria are the powerhouses of the cell, responsible for ATP production through cellular respiration.
• Ribosomes are the sites of protein synthesis.
• The endoplasmic reticulum (ER) is involved in protein synthesis and lipid metabolism.
• The Golgi apparatus processes and packages proteins and lipids.
• Lysosomes contain enzymes that break down cellular waste and debris.

Acid-Base Balance

• Acids are substances that donate protons (H+) in aqueous solutions.
• Bases are substances that accept protons (H+) in aqueous solutions.
• pH is a measure of the acidity or alkalinity of a solution, defined as the negative logarithm of the hydrogen ion concentration.
• Buffers are solutions that resist changes in pH upon addition of an acid or a base.
• The bicarbonate buffer system is a major buffer in the blood, involving carbonic acid (H2CO3) and bicarbonate ions (HCO3-).
• Acidosis is a condition characterized by a decrease in blood pH.
• Alkalosis is a condition characterized by an increase in blood pH.