Biochemistry Overview Quiz

Biochemistry Overview

• Four major types of organic molecules are important in biology: carbohydrates, lipids, proteins, and nucleic acids.

Carbohydrates

• Carbohydrates are the body's main energy source.
• Humans cannot produce carbohydrates, so they must be consumed from plants.
• Carbohydrates are made of carbon, hydrogen, and oxygen with a ratio of 1:2:1.
• Examples include glucose, fructose, sucrose, starch, and glycogen.
• Monosaccharides are single sugar units.
• Disaccharides are two sugar units.
• Polysaccharides are many sugar units.
• Disaccharides and polysaccharides are formed through dehydration synthesis.
• Monosaccharides are also known as isomers. The chemical formula is C₆H₁₂O₆.

Lipids

• Lipids are insoluble in water.
• Lipids contain carbon, hydrogen, and oxygen with a ratio of H to O greater than 2 to 1.
• Lipids include triglycerides, phospholipids, and steroids.
• Triglycerides are commonly known as fats and are formed from one glycerol and three fatty acids through dehydration synthesis.
• Saturated fats are usually from animals, have only single bonds between carbon atoms, are very stable, and are solid or semi-solid at room temperature. Examples include butter.
• Unsaturated fats are usually from plants, have some double bonds between carbon atoms, are more reactive, and are liquid at room temperature. Examples include canola oil.
• Phospholipids are major components of cell membranes. They are formed from one glycerol, two fatty acids, and one phosphate. Phosphates are hydrophilic (polar), and fatty acid tails are hydrophobic (nonpolar).
• Steroids have a structure of four fused carbon rings. Examples include cholesterol and testosterone.
• Lipids are long-term energy storage molecules, containing more than twice the calories than carbohydrates or proteins. They provide structural materials for cell membranes, cushion for organs, and carry vitamins. They're also raw materials for hormone synthesis and provide insulation.

Proteins

• Proteins are made of amino acids.
• Proteins have four levels of structure: primary, secondary, tertiary, and quaternary.

Nucleic Acids

• Nucleic acids include DNA and RNA.

Metabolism

• Metabolism is all the chemical reactions that occur in the body.
• Metabolism can be catabolic or anabolic. Over 200,000 reactions happen in your body cells.
• Monomers are basic subunits used to build larger molecules. Examples include amino acids.
• Polymers are molecules composed of many monomers bonded together, such as a protein.
• Catabolic reactions break down larger molecules (polymers) into smaller ones (monomers). Digestion is an example.
• Anabolic reactions build larger molecules (polymers) from smaller ones (monomers). Photosynthesis and the formation of carbohydrates are examples.
• Hydrolysis is a catabolic process that uses water to break down a molecule.
• Dehydration synthesis is an anabolic process that forms a larger molecule while removing water.

Polymers

• Natural polymers include clothing, food (meat, eggs, etc.), and DNA.
• Human-made polymers include containers and cookware.

Important Polysaccharides

• Starch (plants): a storage molecule for glucose.
• Glycogen (animals): a branched storage molecule for glucose.
• Cellulose (plants): a structural material in plant cell walls.

Cholesterol & Diet

• Cholesterol is a lipid molecule made in the liver. It's used in cell membranes and hormones.
• High cholesterol levels have been linked to atherosclerosis, gallstones, and heart disease.
• People get cholesterol from foods like egg yolks, meat, poultry, fish, and milk products.
• Saturated fats and trans fats can raise blood cholesterol levels.
• Decreasing cholesterol intake involves eating lean meat, fish, poultry, using fat-free and low-fat dairy, and eating vegetables as good protein substitutes.
• Exercise can also lower LDLs (bad cholesterol).

Other Terms

• HDL: High-Density Lipoproteins - A type of lipoprotein considered "good".
• LDL: Low-Density Lipoproteins - A type of lipoprotein considered "bad".