Macromolecules and Cellular Components

Macromolecules and Cell Components

• Macromolecules can be composed of a single type of basic unit/structure
• Monomeric units are the building blocks of macromolecules

Protein Structure

• Proteins are composed of amino acids (aa) linked together by peptide bonds
• Each protein has a unique amino acid sequence
• The structure of an amino acid determines its binding properties
• Amino acids can be polar or non-polar, affecting their binding properties
• Hydrogen bonds, ionic bonds, and disulfide bonds are important in protein structure

Protein Folding

• Proteins fold into a stable, 3D structure that is biologically active
• Folding is influenced by the amino acid sequence and the interactions between amino acids
• The final shape of a protein is determined by its most stable conformation
• Hydrophobic and hydrophilic interactions contribute to protein folding

Protein Functions

• Different proteins have different functions due to their unique amino acid sequences
• Proteins can interact with each other and with other molecules
• Subunits of proteins can come together to form a functional protein

Carbohydrates

• Carbohydrates are composed of monosaccharides linked together by glycosidic bonds
• Monosaccharides can be linked together in different ways to form different carbohydrates
• Examples of carbohydrates include maltose, sucrose, and lactose

Cell Components

• Receptor proteins help facilitate interactions between cells and their environment
• Proteins can interact with nucleic acids and other cell components

Nucleic Acids

• Nucleic acids (DNA and RNA) store, transmit, and express genetic information, influencing heredity and traits.
• They are linear polymers of nucleotides, with four different types of nucleotides in each molecule.
• DNA (deoxyribonucleic acid) and RNA (ribonucleic acid) differ chemically and functionally.

DNA vs RNA

• DNA is double-stranded, resides in the nucleus, and contains the sugar deoxyribose.
• RNA is single-stranded, found in the nucleus and cytoplasm, and contains the sugar ribose.
• There are three main types of RNA: messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA).

RNA Synthesis and Polypeptide Synthesis

• Transcription: a segment of DNA (a gene) directs the synthesis of a complementary molecule of mRNA.
• mRNA export: the processed mRNA exits the nucleus through nuclear pores.
• Translation: a ribosome attaches to the mRNA to read the coded information, and tRNA molecules bring the correct amino acids to add to the polypeptide chain.

Other Types of RNA

• Micro RNAs (miRNAs) and small interfering RNAs (siRNAs) regulate gene expression.

The Monomers Are Nucleotides

• Nucleotides consist of a five-carbon sugar, a phosphate group, and a nitrogen-containing aromatic base.
• There are four types of nucleotides, each with a different base: adenine (A), guanine (G), cytosine (C), and thymine (T) in DNA, with uracil (U) replacing thymine in RNA.

The Polymers Are DNA and RNA

• Nucleotides are linked by a 3',5' phosphodiester bridge, creating a polynucleotide with directionality (5' to 3').

Nucleic Acid Synthesis

• A preexisting molecule is used to ensure that new nucleotides are added in the correct order.
• The template and incoming nucleotides form complementary base pairs.

Complementary Base Pairing

• Adenine (A) forms two hydrogen bonds with thymine (T), and guanine (G) forms three hydrogen bonds with cytosine (C).

The DNA Molecule Is a Double-Stranded Helix

• Francis Crick and James Watson described the double helix structure of DNA in 1953.
• The double helix consists of two anti-parallel and complementary strands of DNA twisted around a common axis.

Lipids

• Lipids are not formed by linear polymerization, but are regarded as macromolecules due to their high molecular weight and importance in cellular structures, especially membranes.
• Features of lipids include:
  • Hydrophobic nature, making them insoluble in water
  • Amphipathic properties, with polar and nonpolar regions
  • Functions include energy storage, membrane structure, and specific biological functions (e.g., signal transmission)

Fatty Acids and Triacylglycerols

• Fatty acids are components of triacylglycerols and phospholipids.
• Fatty acid structure consists of a hydrocarbon chain with a carboxyl group at one end.
• Triacylglycerols contain a glycerol molecule with three fatty acids attached.

Phospholipids

• Phospholipids are important for membrane structure due to their amphipathic nature.
• Phosphoglycerides and sphingolipids are two classes of phospholipids.
• Phosphoglycerides have a phosphatidic acid backbone, with two fatty acids and a phosphate group attached to a glycerol molecule.

Steroids and Glycolipids

• Steroids are lipids with a four-ringed hydrocarbon skeleton, including cholesterol and steroid hormones.
• Glycolipids are lipids containing a carbohydrate group, often attached to a sphingosine or glycerol backbone.

Terpenes

• Terpenes are synthesized from the five-carbon compound isoprene.
• Examples of isoprene-based compounds include vitamin A, carotenoid pigments, dolichols, and electron carriers like coenzyme Q.