Lipid Biochemistry

• Biochemistry is the study of chemical processes within and relating to living organisms.
• It combines biology and chemistry.
• It's essential for understanding life at a molecular level.

Lipid Biochemistry

• Lipids are a broad group of naturally occurring molecules which include fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E, and K), monoglycerides, diglycerides, triglycerides, phospholipids, and others.
• Lipids have roles in energy storage, structural components of cell membranes, and signaling molecules.
• Fatty acids are carboxylic acids with long aliphatic tails, which can be saturated or unsaturated.
• Saturated fatty acids have no carbon-carbon double bonds.
• Unsaturated fatty acids have one or more carbon-carbon double bonds.
• Triacylglycerols (triglycerides) are composed of glycerol and three fatty acids, serving as the primary storage form of fat in the body.
• Phospholipids consist of a glycerol backbone, two fatty acids, and a phosphate group, making them amphipathic and suitable for forming lipid bilayers in cell membranes.
• Cholesterol is a sterol that is a crucial component of animal cell membranes and a precursor to steroid hormones.
• Lipoproteins transport lipids in the blood.
• They include LDL (low-density lipoprotein) and HDL (high-density lipoprotein).
• Lipid metabolism involves the synthesis (lipogenesis) and breakdown (lipolysis) of lipids.
• Beta-oxidation is the process by which fatty acids are broken down in the mitochondria to produce energy.

Protein Structure

• Proteins are large biomolecules consisting of one or more long chains of amino acid residues.
• Amino acids are the building blocks of proteins, each containing an amino group, a carboxyl group, a hydrogen atom, and a distinctive side chain (R group).
• The primary structure of a protein is the linear sequence of amino acids.
• The secondary structure refers to local folded structures such as alpha-helices and beta-sheets, stabilized by hydrogen bonds between amino acids in the polypeptide chain.
• The tertiary structure is the overall three-dimensional structure of a protein, resulting from various interactions, including hydrophobic interactions, hydrogen bonds, disulfide bridges, and ionic bonds, between amino acid side chains.
• The quaternary structure is the arrangement of multiple polypeptide chains (subunits) in a multi-subunit protein.
• Protein folding is the process by which a polypeptide chain acquires its native three-dimensional structure.
• Chaperone proteins assist in protein folding and prevent misfolding or aggregation.
• Protein domains are distinct structural and functional units within a protein.
• Disulfide bonds, formed between cysteine residues, can stabilize protein structure.

Enzyme Kinetics

• Enzymes are biological catalysts that accelerate chemical reactions by lowering the activation energy.
• Substrates are the molecules upon which enzymes act.
• The active site is the region of an enzyme where the substrate binds and catalysis occurs.
• Enzyme-substrate complex: The intermediate formed when a substrate molecule interacts with the active site of an enzyme.
• Cofactors are non-protein chemical compounds that are bound to a protein and are required for the protein's biological activity.
• Coenzymes are small organic non-protein molecules that carry chemical groups or electrons during enzymatic reactions.
• The Michaelis-Menten equation describes the rate of enzymatic reactions, relating reaction velocity to substrate concentration.
• Km (Michaelis constant) is the substrate concentration at which the reaction rate is half of Vmax.
• Vmax is the maximum reaction rate when the enzyme is saturated with substrate.
• Enzyme inhibitors are substances that reduce enzyme activity.
• Competitive inhibitors bind to the active site, preventing substrate binding.
• Noncompetitive inhibitors bind to a different site on the enzyme, altering its shape and reducing its activity.
• Allosteric enzymes have multiple binding sites and exhibit cooperativity, where the binding of one substrate affects the binding of subsequent substrates.
• Feedback inhibition is a regulatory mechanism where the end product of a metabolic pathway inhibits an earlier enzyme in the pathway.

Metabolic Pathways

• Metabolic pathways are a series of interconnected biochemical reactions that convert substrates into products.
• Anabolic pathways synthesize complex molecules from simpler ones, requiring energy input (endergonic).
• Catabolic pathways break down complex molecules into simpler ones, releasing energy (exergonic).
• Glycolysis is the breakdown of glucose into pyruvate, producing ATP and NADH.
• Gluconeogenesis is the synthesis of glucose from non-carbohydrate precursors.
• The citric acid cycle (Krebs cycle) oxidizes acetyl-CoA, producing CO2, ATP, NADH, and FADH2.
• Oxidative phosphorylation is the process by which ATP is generated from the electron transport chain and chemiosmosis.
• The electron transport chain transfers electrons from NADH and FADH2 to oxygen, creating a proton gradient across the mitochondrial membrane.
• Chemiosmosis uses the proton gradient to drive ATP synthesis by ATP synthase.
• The pentose phosphate pathway produces NADPH and pentose sugars.
• Fatty acid synthesis (lipogenesis) converts acetyl-CoA into fatty acids.
• Urea cycle converts ammonia to urea for excretion.
• Metabolic regulation involves controlling enzyme activity and gene expression to maintain homeostasis.

Nucleic Acids

• Nucleic acids are biopolymers essential for all known forms of life.
• DNA (deoxyribonucleic acid) stores genetic information.
• It consists of two strands forming a double helix structure, with a sugar-phosphate backbone and nitrogenous bases (adenine, guanine, cytosine, and thymine).
• RNA (ribonucleic acid) plays various roles in gene expression.
• It is typically single-stranded and contains uracil instead of thymine.
• Nucleotides are the building blocks of nucleic acids, consisting of a nitrogenous base, a pentose sugar (ribose or deoxyribose), and one or more phosphate groups.
• DNA replication is the process by which DNA is copied, ensuring genetic information is passed on to daughter cells.
• Transcription is the process by which RNA is synthesized from a DNA template.
• Translation is the process by which proteins are synthesized from mRNA.
• The genetic code is the set of rules by which information encoded in genetic material (DNA or RNA sequences) is translated into proteins (amino acid sequences) by living cells.
• Mutations are changes in the DNA sequence that can lead to altered protein function.
• Gene expression is the process by which the information encoded in a gene is used to synthesize a functional gene product (protein or RNA).

Hormones

• Hormones are chemical messengers produced by endocrine glands that travel through the bloodstream to target cells, regulating various physiological processes.
• Peptide hormones are synthesized as inactive prohormones or preprohormones.
• They bind to receptors on the cell surface.
• They trigger intracellular signaling cascades.
• Steroid hormones are derived from cholesterol.
• They can pass through the cell membrane
• They bind to intracellular receptors, affecting gene transcription.
• Amine hormones are derived from amino acids like tyrosine.
• For example, epinephrine and thyroid hormones.
• Hormone receptors are proteins that bind to specific hormones, initiating a cellular response.
• Signal transduction pathways are the series of molecular events that occur after a hormone binds to its receptor.
• The hypothalamus and pituitary gland regulate many endocrine functions.
• Feedback loops regulate hormone secretion, maintaining hormone levels within a narrow range.
• Negative feedback inhibits hormone release.
• Positive feedback promotes hormone release.
• Examples of hormones include insulin, glucagon, epinephrine, cortisol, estrogen, testosterone, and thyroid hormones.
• Hormones regulate processes such as metabolism, growth, reproduction, and stress response.