Proteins and Nucleic Acids Structure

• Amino acids have a specific structure.
• Amino acids have an N-terminus and a C-terminus.
• Amino acids can be either hydrophilic or hydrophobic.
• Monomers are small subunits that can be linked together to form a polymer through a process called polymerization.
• Peptide bonds link amino acids together.
• Proteins have four levels of structure: primary, secondary, tertiary, and quaternary.
• Protein folding is the process by which a protein attains its functional shape.
• Enzymes are proteins that act as catalysts.
• Enzymes reduce the energy of activation required for a chemical reaction to proceed.
• Substrates bind to the active sites of enzymes, where the chemical reaction occurs.
• Competitive enzyme inhibitors bind to the active site, while non-competitive inhibitors bind to a different site on the enzyme.

Nucleic Acids Structure

• Nucleotides are composed of a sugar, a phosphate group, and a nitrogenous base.
• The sugar in nucleotides can be either ribose or deoxyribose.
• Nitrogenous bases are either purines or pyrimidines, and they exhibit complementary base pairing (A with T/U, and G with C).
• Phosphodiester bonds link nucleotides together.
• Nucleic acids have primary and secondary structures.
• DNA's function is to store genetic information.
• RNA has various structures and functions in the cell.

Carbohydrates

• Carbohydrates have specific structures and functions.
• Monosaccharides are the monomer subunits of carbohydrates.
• Glycosidic linkages connect monosaccharides together.
• Starch, glycogen, and cellulose are all polysaccharides composed of glucose monomers.
• Glycogen is a storage form of glucose in animals.

Lipids and Membranes

• Lipids have diverse structures and physical properties.
• Hydrocarbons are a key component of many lipids.
• Fats can be saturated, unsaturated, or trans.
• Phospholipids have a polar head and nonpolar tails.
• Phospholipids form a bilayer in water due to their amphipathic nature.
• Amphipathic molecules have both hydrophilic and hydrophobic regions.
• Cell membranes are selectively permeable.
• Membrane structure influences its permeability.
• Diffusion and osmosis are forms of passive transport.
• Passive transport does not require energy, while active transport does.
• Tonicity refers to the relative concentration of solutes in two solutions (isotonic, hypertonic, and hypotonic).

Inside the Cell

• All cells share certain features.
• Prokaryotic cells lack membrane-bound organelles, while eukaryotic cells possess them.
• Organelles include the smooth and rough endoplasmic reticulum, Golgi apparatus, peroxisomes, lysosomes, mitochondria, chloroplasts, vacuoles.
• The smooth endoplasmic reticulum is involved in lipid synthesis.
• The rough endoplasmic reticulum contains ribosomes and is involved in protein synthesis.
• The Golgi apparatus processes and packages proteins.
• Peroxisomes are involved in detoxification.
• Lysosomes contain enzymes for breaking down cellular waste.
• Mitochondria are the site of cellular respiration.
• Chloroplasts are the site of photosynthesis in plant cells.
• Vacuoles have various storage and structural roles.
• Cells have structures such as a cell wall, cytoskeleton, and ribosomes.
• The cell wall provides support and protection.
• The cytoskeleton (actin microfilaments, intermediate filaments, microtubules) provides structural support and facilitates movement.
• Ribosomes are the site of protein synthesis.
• Compartmentalization increases efficiency.

Cell-Cell Interactions

• Cells interact through extracellular layers (cell walls and extracellular matrix).
• Lamella is the middle layer of the cell wall.
• Tight junctions seal cells together.
• Desmosomes connect the cytoskeleton of cells.
• Plasmodesmata are channels between plant cells.
• Gap junctions are channels between animal cells.