Protein Structure and Function Summary

Protein Structure and Function

• Proteins are polymers of amino acids that fold into specific three-dimensional shapes crucial for their biological roles.
• There are 20 different amino acids, all in L-form; properties of side chains affect protein behavior (hydrophobic or hydrophilic).
• Protein folding is primarily driven by non-covalent interactions including hydrogen bonds, ionic bonds, and hydrophobic interactions.
• Chaperones are proteins that assist in the correct folding of other proteins, preventing misfolding and aggregation.
• Secondary structures of proteins include alpha-helices and beta-sheets, which are stabilized by hydrogen bonding.
• Enzymes function as biological catalysts, reducing activation energy and allowing for biochemical reactions to occur efficiently.
• The active site of an enzyme is the region where substrates bind, with the induced fit model explaining how enzymes adjust to accommodate substrates.
• Feedback inhibition is a regulatory mechanism that prevents overproduction of metabolic products by inhibiting early pathway steps.
• Non-covalent bonds, essential for protein stability, encompass hydrogen bonds, ionic interactions, van der Waals forces, and hydrophobic effects.
• Phosphorylation plays a key role in regulating protein function by adding or removing phosphate groups, impacting cellular signaling.

Cell Organelles

• Organelles are specialized cellular structures that perform distinct functions critical for cell operation.
• Plasma membrane serves as a protective barrier, regulating the movement of substances into and out of the cell.
• The nucleus houses genetic material (DNA) and is the site of transcription and ribosome assembly.
• Mitochondria are known as the cell's powerhouse, generating ATP through cellular respiration and found in both plant and animal cells.
• Chloroplasts enable photosynthesis in plant cells, transforming light energy into chemical energy.
• Endoplasmic Reticulum (ER) includes Rough ER (protein synthesis) and Smooth ER (lipid synthesis).
• Golgi apparatus modifies, sorts, and packages proteins for cellular transport and secretion.
• Ribosomes are the sites of protein synthesis, existing freely or attached to the rough ER.
• All cells share fundamental structures (membrane, cytoplasm, DNA, and ribosomes) yet exhibit specialized functions based on organelle composition.
• Microscopy techniques vary in resolution: Light Microscopy (lower resolution, live cells) and Electron Microscopy (high resolution for detailed organelle imagery).
• Key concepts include: eukaryotic cells having membrane-bound organelles, the endosymbiosis theory on mitochondrial and chloroplast origins, and the importance of non-covalent interactions in organelle structure and function.

DNA Structure

• DNA is organized as a double helix with two antiparallel strands, featuring a sugar-phosphate backbone and specific nitrogenous base pairing (A-T, G-C).
• The distance between base pairs is approximately 1 nm, crucial for the structural integrity of DNA.
• Nucleosomes are the basic units of chromatin, formed by DNA wrapped around histone proteins.
• Chromatin is classified into euchromatin (loosely packed, transcriptionally active) and heterochromatin (condensed, transcriptionally inactive).
• The DNA packaging hierarchy progresses from nucleosomes to chromatin fibers to chromosomes.
• Most genes encode proteins; some genes produce functional RNAs like tRNA and rRNA.
• Karyotypes display organized chromosome presentations that are significant for clinical analysis.
• The nucleolus is a site for ribosomal RNA synthesis and assembly, as well as gene regulation through chromatin remodeling, which requires ATP.