Nucleic Acids

DNA (deoxyribonucleic acid) is the largest molecule in the human body. DNA is made up of 2 complimentary strands of nucleotides. Nucleotides are composed of 3 sub-molecules: pentose sugar, a phosphate, and a nitrogen base (purine/pyrimidine).I'll go into more detail about nitrogen bases later on, lets go back to DNA for now. The 2 complimentary strands are joined by hydrogen bonds. Adenine bonds with thymine with 2 hydrogen bonds, and cytosine attaches to guanine with 3 hydrogen bonds. These nitrogen bases hold together the sugar-phosphate backbone of the DNA. This is what allows it to spiral and fold into the unmistakeable double helix, known as DNA.

Now, back to nucleic acids and their nitrogen bases. There are 2 types of nucleic acids, deoxyribonucleic acid and ribonucleic acid, both of which are found in the nucleus of cells.All nucleic acids are made up of nucleotides, which in turn are made up of the 3 sub-molecules mentioned earlier: pentose sugar (ribose for RNA and deoxyribose for DNA), phosphate, and a nitrogen base. There are 2 types of nitrogen bases, purines and pyrimidines.

Purines are made up of adenine and guanine, and have 2 rings. It is found in both DNA and RNA. A memory trick for purines is : Its got 2 be GAP. The 2 is to remind you that there are 2 rings and the letters G, A, P, stand for guanine, adenine, and purine.

Pyrimidines are made up of thymine, uracil, and cytosine and have only one ring.Cytosine is found in both DNA and RNA. Thymine in found in DNA only and Uracil is found in RNA only. A memory trick for pyrimidines is: CUT the pyramid.The letters C, U, T stand for cytosine, uracil, and thymine and the word 'pyramid' is to make you think of  'pyrimidine'.

Proteins

Functions

The functions of proteins are structured, functional, and being a food source. Proteins make up all of the structures in living things. For example, actin and myosin are muscle proteins. Keratin makes up horns, nails, feathers, and hair. The bones, teeth, blood vessels, and ligaments in your body are made up of collagen. Proteins are made up of an amino group, a carboxyl group, and a side chain (an r group) 

The amino acids in proteins bind together with peptide bonds and involves dehydration synthesis (because one water is lost). Two amino acids is a dipeptide. This grows to become a tripeptide (3 amino acids). In the end, a polypeptide is formed, which can have anywhere between 30 and 30,000 amino acids. Proteins differ because of the order of their amino acids. There are four levels of protein structure: 

1. Primary Structure

Primary structure is the first level in the forming of proteins. The amino acids are simply joined together with peptide bonds. This sequence if amino acids will determine the characteristics of the protein. 

2. Secondary Structure

This is the second step in forming a protein. An alpha helix (also called a beta pleated sheet) is formed because of the negative carboxyl group being attracted to the positive amino group. This results in the formation of hydrogen bonds.

 

 

 

3. Tertiary Structure

Some R groups will react with other R groups in the chain. These are either amino acids that are charged or that have a sulphur atom. When the positive/negative attrations and the sulphur bridges interact, the molecule is folded into a very specific 3D shape. This shape is what determines the protein's job in the body.

 

 



4. Quaternary Structure

This is the final stage in protein formulation, and is does not apply to all proteins. The proteins that reach this stage are actually two or more molecules joined together with ionic bonds. Examples are insulin (2 subunits) and hemoglobin (4 subunits).

 

 

 

Lipids

Lipids

Lipids are used for insulation, protection, and the long term storage of energy in animals. They also make some hormones and are the structure of the cell membrane (phospholipids). Neutral fats are called triglycerides, of which there are 2 types:

1. Saturated Fats have no double bonds in the carbon chains. They are unhealthy, mostly come from animals, and become solid at room temperature. The carbons in saturated fats are filled with hydrogens.

2. Unsaturated fats have either one (monounsaturated) or more (polyunsaturated) double bonds. They are healthier, mostly come from plants, and are liquid at room temperature.

These triglycerides are composed of 3 fatty acids bonded to one glycerol through dehydration synthesis. The fatty acids contain a long chain of 16-18 carbons and have an acid end. The glycerol in a triglyceride is a small 3 carbon chain with 3 alcohol groups.

Phospholipids

Phospholipids are used to make up the two-yearlayered cell membrane of all cells. The third fatty acid group of a triglyceride is replaced with an inorganic phosphate group. This end is hydrophilic (water soluble), while the polar tail is hydrophobic (not water soluble).

Steroids

Steroids are made up of four carbon ring molecules fused together. They are used as either a sex hormone, such as testosterone, or vitamin D or cholesterol. 

Synthesis/Hydrolysis and Carbohydrates

Monomers are amino acids, sugars, fatty acids, and nucleotides. They are joined together to form polymers (a chain of monomers linked together). Monomers are joined together through dehydration synthesis, and are broken down through hydrolysis. These reactions require ATP energy, water and enzymes in order to work.

Carbohydrates

In carbohydrates, the carbons, hydrogens, and oxygen are found in the ratio of 1:2:1, and are made up of a repeating chain of sugars. For example, C3H6O3 follows the ratio of 1:2:1and is therefore a carbohydrate. Monosaccharides include fructose, ribose, and deoxyribose. The basic sugar molecule is glucose and has a ring structure.

Disaccharides are formed when dehydration synthesis binds two sugars together. This is what a disaccharide looks like:

Types of disaccharides are maltose, sucrose, and lactose.

Polysaccharides mean there are many sugars that have been binded together though dehydration synthesis.When this occurs, four types of polysaccharides may be formed: starch, glycogen, cellulose, and chitin.

• Cellulose is the simplest carbohydrate in terms of structure. It is made up of long chains of glucose molecules and has no side chains. Cellulose makes up the cell walls of plants and cannot be digested by mammals. 

• Starch is made up of many glucose molecules linked together and has few side chains. Plants store their energy as starch  

• Animals store their energy as glycogen and is stored in humans in our liver and muscles. Glycogen has many side chains. 

• Chitin is long glucose chains linked with covalent bonds. It is very strong, and makes up structures such as exo-skeletons, fingernails, claws, and beaks.

Carbohydrates are used as energy. When the bonds between carbon atoms are broken, energy is released and this energy is used by cells. Carbs also have a structural function: cellulose is a structural compound found in plants.