Lipid Biochemistry Overview

Definition: Study of lipids' structure, function, and metabolism in biological systems.
Types of Lipids:
- Fatty Acids: Saturated (no double bonds) and unsaturated (one or more double bonds).
- Triglycerides: Glycerol + three fatty acids; main form of stored energy.
- Phospholipids: Glycerol + two fatty acids + phosphate group; key component of cell membranes.
- Sterols: Four fused carbon rings; e.g., cholesterol, important for membrane fluidity.
Functions:
- Energy storage
- Structural role in membranes
- Signaling molecules (e.g., hormones)

Levels of Structure:
1. Primary: Sequence of amino acids.
2. Secondary: Local folding patterns (α-helix, β-sheet) stabilized by hydrogen bonds.
3. Tertiary: Overall 3D structure formed by interactions among R groups.
4. Quaternary: Assembly of multiple polypeptide chains into a functional unit.
Amino Acids: 20 standard amino acids; classified as essential and non-essential.
Protein Folding: Assisted by chaperones; misfolding can lead to diseases (e.g., Alzheimer's).

Definition: Study of the rates of enzyme-catalyzed reactions.
Key Concepts:
- Substrate: The reactant that enzymes act on.
- Active Site: Region where substrate binds.
- Michaelis-Menten Kinetics: Describes the rate of enzymatic reactions with respect to substrate concentration.
  - Vmax: Maximum reaction velocity.
  - Km: Substrate concentration at which the reaction rate is half of Vmax.
Inhibition:
- Competitive: Inhibitor resembles substrate; competes for active site.
- Non-competitive: Inhibitor binds elsewhere; reduces enzyme activity regardless of substrate concentration.

Definition: Study of the molecular basis of gene structure and function.
DNA Structure: Double helix formed by nucleotides (adenine, thymine, cytosine, guanine).
Gene Expression:
- Transcription: DNA → mRNA.
- Translation: mRNA → protein.
Mutations: Changes in DNA sequence, can lead to genetic diversity or diseases.
Techniques:
- PCR (Polymerase Chain Reaction): Amplifies specific DNA sequences.
- CRISPR: Gene editing technology for targeted modifications.

Definition: Set of life-sustaining chemical reactions in organisms.
Categories:
- Catabolism: Breakdown of molecules to obtain energy (e.g., glycolysis).
- Anabolism: Synthesis of complex molecules from simpler ones (e.g., protein synthesis).
Energy Currency: ATP (adenosine triphosphate) used for energy transfer.
Key Pathways:
- Glycolysis: Conversion of glucose to pyruvate; produces ATP and NADH.
- Krebs Cycle: Oxidation of acetyl-CoA to CO2; generates electron carriers (NADH, FADH2).
- Electron Transport Chain: Series of protein complexes; uses electrons from NADH and FADH2 to produce ATP through oxidative phosphorylation.

Lipids are crucial biomolecules encompassing structure, function, and metabolism within living organisms.
Fatty acids can be saturated (lacking double bonds) or unsaturated (containing one or more double bonds).
Triglycerides consist of glycerol bonded to three fatty acids; they serve as the primary storage form of energy in organisms.
Phospholipids feature glycerol, two fatty acids, and a phosphate group; essential for forming cell membranes and their integrity.
Sterols, such as cholesterol, possess four fused carbon rings and play a vital role in maintaining cell membrane fluidity.
Key functions of lipids include energy storage, structural roles in biological membranes, and acting as signaling molecules (e.g., hormones).

Proteins exhibit four levels of structure:
- Primary structure is the linear sequence of amino acids.
- Secondary structure includes local folding patterns such as alpha-helices and beta-sheets, held together by hydrogen bonds.
- Tertiary structure is the complete three-dimensional arrangement of a polypeptide chain.
- Quaternary structure arises from the assembly of multiple polypeptide chains into a functional protein complex.
There are 20 standard amino acids categorized as essential (obtained from diet) and non-essential (synthesized by the body).
Protein folding is facilitated by molecular chaperones; improper folding can lead to diseases, exemplified by Alzheimer's.

Enzyme kinetics focuses on the speed of enzyme-catalyzed reactions and their regulation.
Substrates are the reactants that enzymes convert to products.
The active site is the specific region of the enzyme that binds the substrate.
Michaelis-Menten kinetics models the relationship between substrate concentration and reaction velocity.
Vmax represents the maximal rate of reaction, while Km indicates the substrate concentration at which the reaction rate is half of Vmax.
Inhibition types include:
- Competitive inhibition, where an inhibitor mimics the substrate and competes for the active site.
- Non-competitive inhibition, where an inhibitor binds to a different site and reduces enzyme activity irrespective of substrate presence.

Molecular genetics studies the underlying molecular mechanisms that dictate gene structure and function.
DNA is organized as a double helix composed of nucleotide bases: adenine (A), thymine (T), cytosine (C), and guanine (G).
Gene expression involves transcription (conversion of DNA to mRNA) and translation (synthesis of proteins from mRNA).
Mutations are alterations in the DNA sequence that can increase genetic variability or result in diseases.
Key techniques in molecular genetics include:
- PCR (Polymerase Chain Reaction) for amplification of specific DNA sequences.
- CRISPR technology allows precise gene editing for targeted modifications.

Metabolism encompasses all biochemical reactions essential for sustaining life.
It can be divided into:
- Catabolism, which involves breaking down molecules to harvest energy (like glycolysis).
- Anabolism, the process of synthesizing complex biomolecules from simpler substrates (such as protein synthesis).
ATP (adenosine triphosphate) serves as the primary energy currency in cellular energy transfer.
Important metabolic pathways include:
- Glycolysis, which converts glucose into pyruvate while generating ATP and NADH.
- Krebs Cycle (Citric Acid Cycle), which oxidizes acetyl-CoA into CO2, producing electron carriers NADH and FADH2.
- The Electron Transport Chain, a series of proteins that convert electrons from NADH and FADH2 into ATP through oxidative phosphorylation.