We learn that you are what you eat in Episode 5. Melanie explores the four types of biological molecules in both structure and function.
We learn that you are what you eat in Episode 5. Melanie explores the four types of biological molecules in both structure and function. Kick it off with proteins (1:20) which have the greatest diversity in structure and function due to R-groups chemistry (2:49). Melanie reminds us of the elemental ratios in carbohydrates and to notice the pattern of an -ose ending (4:10). She also recAPs the diversity and characteristics of lipids - Do you remember what saturated fatty acids are? (4:40). Don’t forget the crucial role of phospholipids in the formation of membranes (6:05). She takes us back to kindergarten (6:26) to recall nucleotide arrangement. Did you count how many times the cow mooed?
The Question of the Day (8:19) asks “Which category of biological molecules is ATP found in?.Thank you for listening to The APsolute RecAP: Biology Edition!
(AP is a registered trademark of the College Board and is not affiliated with The APsolute RecAP. Copyright 2020 - The APsolute RecAP, LLC. All rights reserved.)
EMAIL:
Follow Us:
Hi and welcome to the APsolute Recap: Biology Edition. Today’s episode will recap Biological Molecules
Zoom out:
Unit 1 - Chemistry of life
Topic 1.4-1.5 – Properties, Structure, and Functions of Biological Molecules. We will also recap 1.6 Nucleic Acids
Two Big ideas - Systems interaction and Information storage and transmission
Remember – you are what you eat. And so it should be no surprise that the four major biological molecules are carbohydrates, proteins, lipids, and nucleic acids. Structure influences function! Let's talk about the way these monomers are arranged first, and then some examples of how the polymers function.
Let’s Zoom in:
First up: Proteins. Proteins are polymers (or polypeptides) of the monomer amino acids. Their diversity in structure is the greatest of all the biological molecules. An amino acid is made up of one central carbon atom that forms four single covalent bonds – one is to hydrogen, another to a carboxyl (c=o, o) and a third is to an amino (NH3). The fourth covalent bond is to an “R” group. This R group is a substitute for different side chains that give each of the 20 different amino acids their unique properties. These properties may be hydrophobic, hydrophilic, or ionic. When amino acids link together, dehydration synthesis occurs between an amino group of one monomer and the carboxyl group of the other. The covalent bond formed between them is referred to as a peptide bond.
Proteins have four levels of structure as it bends and folds in upon itself. Primary structure is a chain of amino acids. Secondary can either form an alpha helix or a beta pleated sheet. Tertiary is when alpha helices and beta sheets fold further inwards. The final is quaternary, which has two separate amino acid chains, bent and folded and interacting together. The specific structure that each protein has is dependent upon the chemical properties of the R group. Just to name a few protein functions, because they have the most. Proteins can be enzymes that catalyze chemical reactions, they provide structural support and transport channels, they serve as receptors in signaling pathways, and also form motors for cellular movement.
Next, let's discuss carbohydrates. Carbohydrates only contain the elements carbon, hydrogen and oxygen - and in a very specific way. Think of a carbohydrate you are familiar with - probably glucose - C6H12O6. Carbon, hydrogen and oxygen will always be found in a 1:2:1 ratio in a carbohydrate. These biological molecules can form long chains, some of which are branched, or ringed structures. Here are some examples of carbohydrates. Carbohydrates serve as a cellular fuel and building material. Monosaccharides like glucose and fructose as well as disaccharides, such as lactose and sucrose are often used as fuel sources for the cell. Larger polysaccharides can be used for structural support such as cellulose in plant cell walls or chitin in animal exoskeletons or fungi cell walls. Starch and glycogen and used for long term energy storage in plants and animals respectively. You may have noticed, but ending in -ose is a common pattern in naming carbohydrates.
The third group are lipids. Lipids are a very diverse group of hydrophobic molecules that are nonpolar. Nonpolar means that they won’t interact with water or “water fearing” as a literal translation of hydrophobic. Looking at the elemental properties of lipids, you will always see a ratio of Hydrogen to Oxygen that is greater than 2:1. A common characterization of lipids is saturated or unsaturated. But what are they saturated with? This is referring to a literal elemental saturation of hydrogens. If all bonds are saturated, then the chains are straight and more closely packed together. An example would be butter which is solid at room temperature. If chains are unsaturated, that means that there is a double bond or a bend in the fatty acid chain, and they cannot closely pack together and would be a liquid at room temperature – like oil. Some further examples of lipids include triglycerides, or fats and oils. These are made up of a glycerol and three fatty acids and serve as an important energy source. Steroids have 4 carbon rings with attached functional groups. They can be found in cell membranes like cholesterol, as well as with signaling molecules like hormones.
Perhaps the most common, or common to this class, lipid will be the phospholipid. Phospholipids are polar. Remember water? Water was polar too. So we should expect a phospholipid to have different chemical properties on each side of the molecule. Phospholipids have hydrophilic tails and hydrophobic heads. The two fatty acid tails have a saturated and unsaturated components. The hydrophobic head has a glycerol, phosphate, and choline group. The property of phospholipid and their nature of forming a bilayer structure makes them the ideal structure to make up all cellular membranes.
The last group of biological molcuels is less associated with foods. These are the nucleic acids. Nucleic acids are made up of monomers called nucleotides. A nucleotide has three parts: the pentose sugar, the phosphate group and a nitrogenous base. Think of a nucleotide like you used to draw your kindergarten drawings. There was the house, with five sides. Coming off of the house may have been a garage and above the house a sun. This structure can be represented as a nucleotide with the sun as a phosphate, the house a pentose sugar and the garage representing the nitrogenous base. All three of these pieces will be covalently bonded together.
Nitrogenous bases are formed into two main groups. The purines have two rings and are Guanine and Adenine. The pyrimidines are one ring and are cytosine, thymine or uracil. All nucelic acids have linear sequence with directionality, designated as 5’ or 3’. These primal natures refer to the identified carbon on the pentose sugar.
Some examples of nucleic acids include DNA, or deoxyribonucleic acid. It has a deoxyribose sugar, base pairs of ATCG and is double stranded. The backbone of DNA is made of sugars and phosphates covalently bonded together. According to base paring rules, A bonds with T via two H bonds and C bonds with G with 3 H bonds. This nitrogenous bonding is the foundation of hereditary information and DNA is found in the nucleus of eukaryotic cells. RNA has a ribose sugar with bases AUCG and is typically single stranded. RNA has a very large role in gene expression and will be represented in molecules of mRNA, tRNA, and rRNA with the central dogma.
To recap……
The four major biological molecules are carbohydrates, proteins, Lipids, and Nucleic Acids. Each has a very specific structure.
Question of the day: Which category of biological molecules is ATP found in? Remember, ATP stands for adenosine triphosphate and is the primary energy source for the cell.