Cellular Biology Concepts

• The study of biological molecules is molecular biology.
• Molecular Biology studies the composition, structure, and interactions of molecules, such as nucleic acids and proteins, that carry out cells' functions and maintenance.
• The building blocks of life are the 4 elements; hydrogen, carbon, oxygen, and nitrogen.

Monomers, Polymers, and Macromolecules

• Monomers are relatively simple molecules used as a basic building block for synthesizing a polymer.
• A polymer is a giant molecule made from similar repeating subunits joined together in a chain.
• A macromolecule is a large biological molecule such as a protein, polysaccharide, or nucleic acid.

Carbohydrates

• A carbohydrate contains carbon (C), hydrogen (H), and oxygen (O).
• Carbohydrates can be found in wide varieties of food.
• Carbohydrates serve as a primary source of energy.
• Hydrogen and oxygen atoms appear in a 2:1 ratio.
• Three primary forms are monosaccharides, disaccharides, and polysaccharides.

Monosaccharides

• These are simple sugars that can be linear or ring form.
• Examples consist of glucose, fructose, and galactose.
• Monosaccharides are water-soluble.
• They are colourless, possess a sweet taste and have crystalline solids.
• Monosaccharides have a reducing sugar.
• Trioses contain 3 carbon atoms.
• Pentoses contain 5 carbon atoms such as ribose and deoxyribose.
• Hexoses contain 6 carbon atoms such as glucose, fructose, and galactose.

Glucose Ring Structures

• In alpha-glucose, the OH group on the first carbon projects below the plane of the ring.
• In beta-glucose, the OH group on the first carbon projects up above the plane of the ring.
• The position of OH and H at each carbon for alpha and beta glucose is memorized:
• Alpha-glucose = BBAB
• Beta-glucose = ABAB
• A = above, B = below

Disaccharides

• Form when two monosaccharides join via a glycosidic linkage, via condensation
• A glycosidic linkage is broken by adding water to it, via hydrolysis.
• Water-soluble, with a sweet taste, and crystallizes easily
• Three common forms are:
  • Maltose: glucose + glucose
  • Sucrose: glucose + fructose
  • Lactose: glucose + galactose

Polysaccharides

• Polymers with hundreds to thousands of monosaccharides joined by glycosidic linkages.
• Chains formed can vary in length, branched or unbranched, and form a straight or coiled shape
• tasteless, insoluble in water, and not easily crystallized
• Example is Starch, Glycogen & Cellulose

Starch

• A polysaccharide formed from a-glucose.
• Serves as a major storage form of carbohydrates in plants.
• It is insoluble in water and is stored in large amounts with little effect on the water potential.
• Starch contains 2 components; amylose which is unbranched, and amylopectin which is branched.

Amylose and Amylopectin

• Both made from a-glucose molecules
• Linear chain is joined by a-1,4 glycosidic bond between neighboring C1 and C4 atoms.
• Amylopectin: Forming branched chains of up to 1500 units. Branches occur every 30 units.
• Linear chain is joined by a-1,4 glycosidic bond between neighboring C1 and C atoms.
• Each branch is joined by a-1,6 glycosidic bond

Glycogen

• A major storage form of carbohydrates found in animals.
• Mainly present in the liver and muscle cells where high metabolic activities take place
• Insoluble in water.
• Like amylopectin, glycogen is made of 1,4 linked a-glucose with 1,6 linkages
• Glycogen displays a structure similar to amylopectin.
• It is a branched structure, more so than amylopectin.
• Glycogen molecules clump together to form granules, which are visible in liver and muscle cells to form an energy reserve.

Cellulose

• Serves as an important structural material in plants.
• A long chain beta-glucose holds cellulose together with b-1,4- glycosidic linkage.
• Exhibits a straight-chain polymer
• Parallel strands are linked by hydrogen bonds, forming a stable cell wall.

Lipids

• These are organic molecules insoluble in water but are soluble in organic solvents.
• They contain the elements Carbon, Hydrogen, and Oxygen.
• Functions of lipids include cell membranes, energy storage, insulation, etc.
• Fats and oils are familiar lipids.
• Fats of animal origin, like butter, appear solid at room temperature.
• Oils of plant origin, like corn oil, are liquid at room temperature.
• Lipids are chemically similar, and fatty acids serve as their building block.

Fatty Acids

• A series of acids found in fats (lipids).
• They contain the acidic group -COOH, known as a carboxyl group.
• Larger molecules have long hydrocarbon tails attached to the acid 'head'.

Triglycerides

• The most common lipids.
• One glycerol and 3 fatty acids make up triglycerides, forming an ester linkage
• Ester linkings form by condensation or esterification, between a hydroxyl group of glycerol and a carboxyl group of fatty acids.
• In each reaction, one water molecule is removed (total of 3 water molecules).

Phospholipids

• Composed of 2 fatty acids attached to glycerol and a phosphate group
• Plays its role in cell membrane structure
• When added to water, self-assembly into aggregates, where hydrophobic tails point toward the center and hydrophilic heads point on the outside

Nucleic Acids

• DNA and RNA are nucleic acids.
• DNA contains information for almost all cell activities, including cell division.
• RNA stores and transfers information that is essential for the manufacturing of proteins
• Nucleic acids are polymers made of nucleotide monomers.
• Nucleotides are smaller.
• Has 3 components: a nitrogen-containing base, a pentose sugar (5C), and a phosphate group.

Nucleotide

• Ribose is the sugar used in nucleotides of RNA.
• Deoxyribose is in nucleotides of DNA.
• Ribose and deoxyribose sugars differ due to deoxyribose lacking an oxygen atom.
• Rings of carbon and nitrogen form a nitrogenous base.
• There are two types, purines & pyrimidines. -Three nitrogenous bases form Pyrimidines; Cytosine, Thymine, and Uracil -Two nitrogenous bases that form Purines; Adenine and Guanine.

Comparing DNA and RNA Nucleotides

• Deoxyribose is the pentose sugar of DNA.
• Ribose is the pentose sugar of RNA.
• Nitrogenous bases in DNA are A, C, G, and T.
• Nitrogenous bases in RNA are A, C, G, and U.

Forming Polynucleotides

• To form the polynucleotides DNA and RNA, linked nucleotides form a long chain via condensation between sugar and phosphate group of different nucleotides, forming a phosphodiester bond
• The covalent sugar-phosphate bonds link the 5-carbon of one sugar molecule and the 3-carbon of the next.
• Polynucleotide sequences reference the 5' to 3' direction. 

DNA

• Two Polynucleotides, running in opposite directions in its structure, are the result of held together by hydrogen bonds formed between the bases.
• Complementary base pairing:
  • A links with T by two hydrogen bonds.
  • C links with G by three hydrogen bonds.
• In RNA, Uracil replaces Thymine.

RNA Traits

• A single-stranded molecule containing ribose sugar.
• Have 4 different nucleotide bases; A, G, C and U.
• mRNA transcribes the DNA and directs the translation of protein.
• rRNA is involved in the translation of protein.
• tRNA delivers amino acids to the ribosomes during translation.

Explore key concepts in cellular biology, including the roles of glycogen granules, cellulose characteristics, lipid insolubility, and the formation of triglycerides. This also covers nucleotide components and differences between monomers, polymers, and macromolecules. Furthermore, the primary function of RNA molecules is discussed.