Biochemistry Chapter on Lipids and Reactions

Unsaturated Fatty Acids

• Not saturated with hydrogen, characterized by double bonds or kinks in the carbon chain.
• Remain liquid at room temperature, important for cell membrane fluidity.

Fat Function

• Major role is energy storage within organisms.

Phospholipids

• Composed of a hydrophilic phosphate head and two hydrophobic fatty acid tails.
• Essential components of cell membranes, forming a bilayer that arranges with hydrophilic heads facing outward and hydrophobic tails inward.

Anabolic Reactions

• Involve the synthesis of complex molecules from simpler ones; require energy input.
• Considered endergonic reactions, where the free energy of products exceeds that of the reactants.

Catabolic Reactions

• Break down complex molecules into simpler ones, releasing energy.
• Classified as exergonic reactions, where the free energy of products is less than that of reactants.

Nucleic Acids

• Polymers made up of nucleotide monomers, crucial for storing and transmitting genetic information.

Function of Nucleic Acids

• Store, transmit, and utilize hereditary information through genes.

Major Nucleic Acid Types

• Deoxyribonucleic acid (DNA) and ribonucleic acid (RNA).

DNA Functions

• Stores genetic information, directs RNA synthesis, and controls protein synthesis.

RNA Functions

• Translates DNA sequences into polypeptides (proteins).

Nucleotide Structure

• Comprised of a 5-carbon sugar, a phosphate group, and a nitrogenous base.

Nucleoside Structure

• Consists of a pentose sugar and a nitrogenous base.

Phosphodiester Bond

• Links nucleotides through a condensation reaction; connects the hydroxyl group on the 3' carbon of one nucleotide to the phosphate group on the 5' carbon of another, forming the backbone of polynucleotides.

Pyrimidines and Purines

• Pyrimidines: single-ringed nucleotides (Cytosine, Thymine/Uracil in RNA).
• Purines: double-ringed nucleotides (Adenine, Guanine).

RNA Structure

• Typically single-stranded; can fold back on itself through hydrogen bonding.

DNA Structure

• Double helix structure, with hydrogen bonds forming between complementary bases (A-T and C-G pairing).

Base Pairing Rules

• DNA: C pairs with G, T pairs with A; RNA: C pairs with G, U pairs with A.
• C-G bonds are stronger than A-T bonds.

Transcription

• The process of transferring genetic information from DNA to messenger RNA (mRNA) within the nucleus.

Translation

• Involves the formation of a polypeptide (protein) where a ribosomal complex interprets mRNA.

Central Dogma

• Describes the flow of genetic information: DNA → RNA → Protein.

Proteins

• Polymers of amino acids, perform multiple roles including enzymatic activities, defense, regulation, and transport.

Amino Acids

• Composed of 20 common types; consist of an amino group, carboxyl group, and a variable side chain (R group).

Peptides

• Short chains of amino acids (20 or fewer), often act as signaling molecules or hormones.

Polar and Nonpolar Amino Acids

• Polar amino acids have hydrophilic side chains.
• Nonpolar amino acids are hydrophobic with nonpolar side chains.

Cysteine, Glycine, Proline

• Cysteine: Contains thiol groups, forms disulfide bridges, influencing protein folding.
• Glycine: Smallest amino acid, fits into tight spaces in proteins.
• Proline: Contains a ring structure, affecting protein geometry.

Peptide Bonds

• Covalent bonds formed between amino acids during dehydration synthesis; growth occurs from the amino terminus to the carboxyl terminus.

Protein Structures

• Primary: Sequence of amino acids.
• Secondary: Local folding patterns like α-helices and β-pleated sheets.
• Tertiary: Overall 3D structure formed by interactions between R-groups.
• Quaternary: Arrangement of multiple polypeptides into functional units.

Enzymes

• Specialized proteins that catalyze reactions without being consumed; commonly end in -ase.

Active Site and Substrate

• Active site: Area on enzyme where substrates bind specifically.
• Substrate: The reactant that undergoes a chemical change during enzymatic reaction.

Enzyme-Substrate Complex and Induced Fit

• Complex forms when substrates bind; induced fit model describes how binding alters shape to enhance catalysis.

Cofactors and Prosthetic Groups

• Cofactors: Non-protein components required for enzyme activity (may be inorganic).
• Prosthetic groups: Non-amino acid compounds permanently attached to enzymes.

Enzyme Regulation

• Competitive inhibitors: Compete with substrates for active site binding.
• Noncompetitive inhibitors: Bind elsewhere, altering enzyme shape and function.
• Allosteric regulation: Modulation of enzyme activity through non-active site binding.

Feedback Inhibition

• Pathway regulation where the end product inhibits the first enzyme to prevent overproduction.

Cell Theory

• All living organisms are made of cells, the cell is the basic unit of life, and all cells arise from pre-existing cells.

Plasma Membrane

• Acts as an outer barrier, selectively permeable; regulates entry/exit of substances.

Prokaryotic vs. Eukaryotic Cells

• Both contain DNA, ribosomes, cytosol, and a plasma membrane.
• Prokaryotic: No membrane-bound organelles, with a single circular chromosome.
• Eukaryotic: Membrane-bound organelles, multiple chromosomes within a nuclear envelope.

Eukaryotic Cell Parts

• Major components include the nucleus, cytoplasm, and plasma membrane.

Nucleus and Chromosomes

• Nucleus: Site of DNA replication and transcription, containing a nucleolus for rRNA synthesis.
• Chromosomes: Structures made from condensed chromatin, housing genetic information.

Ribosomes

• Composed of rRNA and proteins; essential for protein synthesis, either free in cytoplasm or attached to the rough ER.

Endomembrane System

• Composed of various organelles (e.g., ER, Golgi apparatus, lysosomes) involved in the synthesis, modification, and transport of proteins.

Endoplasmic Reticulum

• Rough ER: Studded with ribosomes for protein production and modification.
• Smooth ER: Synthesizes lipids and detoxifies harmful substances.

Golgi Apparatus

• Modifies ER products and dispatches them to destinations within or outside the cell.

Lysosomes

• Contain hydrolytic enzymes for breaking down macromolecules; involved in intracellular digestion.

Mitochondria and Chloroplasts

• Mitochondria: Site of ATP production through cellular respiration, double-membraned structure.
• Chloroplasts: Convert light energy into chemical energy through photosynthesis, also double-membraned.

Cytoskeleton

• Network of protein filaments providing structural support and facilitating organelle movement.

Cell Junctions

• Specialized structures that connect and bind adjacent cells; types include tight junctions, desmosomes, and plasmodesmata in plants for cytoplasmic flow.