Biochemistry: Carbohydrates and Lipids

Biochemistry

• Explores the chemical processes within and related to living organisms.
• Integrates biology and chemistry.

Biomolecules

• Molecules produced by living organisms.
• Major classes include carbohydrates, lipids, proteins, and nucleic acids.

Carbohydrates

• Primary energy source and structural component.
• Monosaccharides are simple sugars like glucose and fructose.
• Disaccharides consist of two monosaccharides linked together, such as sucrose and lactose.
• Polysaccharides are complex carbohydrates of many monosaccharides, examples are starch, cellulose, and glycogen.
• Glycolysis breaks down glucose into pyruvate, generating ATP and NADH.
• Gluconeogenesis synthesizes glucose from non-carbohydrate precursors.

Lipids

• Includes fats, oils, phospholipids, and steroids.
• Hydrophobic molecules are crucial for energy storage, cell structure, and signaling.
• Fatty acids are hydrocarbon chains that can be saturated (no double bonds) or unsaturated (one or more double bonds).
• Triglycerides are composed of glycerol and three fatty acids and serve as energy storage.
• Phospholipids are major components of cell membranes, with a polar head and nonpolar tails.
• Steroids like cholesterol have a ring structure and function as hormones or membrane components.
• Beta-oxidation breaks down fatty acids into acetyl-CoA, generating ATP.

Proteins

• Performs diverse functions like catalysis, transport, structure, and signaling.
• Amino acids are the building blocks of proteins, linked by peptide bonds.
• Primary structure is the sequence of amino acids.
• Secondary structure involves local folding patterns like alpha-helices and beta-sheets.
• Tertiary structure is the overall 3D structure of a single protein molecule.
• Quaternary structure is the arrangement of multiple protein subunits.
• Enzymes are biological catalysts that speed up biochemical reactions.
• Enzyme kinetics describes the rate of enzyme-catalyzed reactions.
• Michaelis-Menten kinetics relates reaction velocity to substrate concentration.
• Enzyme inhibition can be competitive, noncompetitive, or uncompetitive.

Nucleic Acids

• DNA and RNA store and transmit genetic information.
• Nucleotides are the building blocks, consisting of a sugar, a phosphate group, and a nitrogenous base.
• DNA is a double-stranded helix containing the genetic code.
• RNA is single-stranded and involved in protein synthesis.
• DNA replication is the process of copying DNA.
• Transcription is the synthesis of RNA from a DNA template.
• Translation is the synthesis of proteins from an RNA template.
• The genetic code specifies how the information in DNA and RNA is translated into proteins.

Metabolism

• Sum of all chemical reactions in an organism.
• Catabolism breaks down complex molecules into simpler ones, releasing energy.
• Anabolism synthesizes complex molecules from simpler ones, requiring energy.
• ATP (adenosine triphosphate) is the primary energy currency of the cell.
• The citric acid cycle (Krebs cycle) oxidizes acetyl-CoA, producing ATP, NADH, and FADH2.
• Oxidative phosphorylation generates ATP from NADH and FADH2 through the electron transport chain.

Enzymes

• Biological catalysts speed up biochemical reactions by lowering activation energy.
• The active site is the region where the substrate binds and catalysis occurs.
• Cofactors are non-protein molecules required for enzyme activity.
• Coenzymes are organic cofactors (vitamins).
• Enzyme kinetics studies the rate of enzyme-catalyzed reactions.
• The Michaelis-Menten equation describes the relationship between reaction velocity and substrate concentration.
• The Lineweaver-Burk plot is a graphical representation of the Michaelis-Menten equation.
• Enzyme inhibition refers to molecules that reduce or prevent enzymatic activity.
• Competitive inhibition occurs when the inhibitor binds to the active site.
• Non-competitive inhibition occurs when the inhibitor binds to a site other than the active site.

Cell Structure and Function

• The cell membrane is a lipid bilayer separating the inside of the cell from the external environment.
• The nucleus contains the cell's DNA.
• Mitochondria are responsible for energy production (ATP synthesis) through cellular respiration.
• The endoplasmic reticulum (ER) is involved in protein and lipid synthesis.
• The Golgi apparatus modifies, sorts, and packages proteins and lipids.
• Lysosomes contain enzymes for breaking down cellular waste.

Molecular Biology Techniques

• PCR (Polymerase Chain Reaction) amplifies specific DNA sequences.
• Gel electrophoresis separates molecules based on size and charge.
• Blotting techniques (Southern, Northern, Western) detect specific DNA, RNA, or protein molecules.
• DNA sequencing determines the nucleotide sequence of DNA.
• Recombinant DNA technology manipulates DNA to create new genetic combinations.

Signal Transduction

• Cells receive and respond to external signals through signal transduction.
• Receptors bind to signaling molecules (ligands).
• G protein-coupled receptors (GPCRs) activate intracellular signaling pathways.
• Receptor tyrosine kinases (RTKs) activate signaling pathways through phosphorylation.
• Second messengers (e.g., cAMP, calcium ions) amplify the signal.
• Signaling pathways regulate gene expression, metabolism, and cell growth.

Vitamins and Minerals

• Vitamins are organic compounds essential for various biochemical reactions.
• Water-soluble vitamins (e.g., B vitamins, vitamin C) are not stored in the body and need to be consumed regularly.
• Fat-soluble vitamins (e.g., vitamins A, D, E, K) are stored in the body.
• Minerals are inorganic substances required for various physiological functions (e.g., calcium, iron, zinc).

Acid-Base Chemistry

• pH measures the acidity or basicity of a solution (-log[H+]).
• Acids donate protons, bases accept protons.
• Buffers resist changes in pH (e.g., bicarbonate buffer system).
• The Henderson-Hasselbalch equation relates pH, pKa, and concentrations of acid and base.

Thermodynamics

• Concerned with energy transformations in chemical and physical processes.
• First law: energy is conserved.
• Second law: entropy (disorder) increases in a closed system.
• Gibbs free energy (G) = enthalpy (H) - temperature (T) * entropy (S).
• Reactions with negative delta G are spontaneous (exergonic).
• Reactions with positive delta G require energy input (endergonic).