Chemistry and Biomolecules Chapter 2.3

Chemical Reactions Bonds between atoms are built and broken causing substances to combine and recombine as different molecules during chemical reactions. All of the chemical reactions within a cell are referred to as the cell’s metabolism.

The Role of Carbon The carbon atom has four electrons available for bonding in its outer energy level. When two carbons bond, they can form a single, double or triple bond (sharing 1, 2, or 3 electrons) Carbons can form short chains, long chains, branched chains, or rings

Organic Compounds Organic compounds are any compound that contain carbon-hydrogen bonds. There are four types of organic compounds necessary for life –Carbohydrates –Lipids –Proteins –Nucleic Acids

Carbohydrate Structure Carbohydrates contain: Carbon, Hydrogen, and Oxygen Structures: –Monosaccharides – 1 ring (simple sugars) Glucose (cell’s primary source of energy) –Disaccharides – 2 rings Sucrose (table sugar) –Polysaccharides – 3 or more rings (complex carbohydrates) Amylose (component of starch) Cellulose (structural carbohydrate in plants)

Role of Carbohydrates In Plants –Carbohydrates are synthesized during the process of photosynthesis –The plants then: Use them as a source of energy Store them in the cells. In Animals –Carbohydrates are consumed as sugars, starches, and fiber –When complex carbohydrates are consumed, digestion breaks the bonds between the larger carbohydrate molecules so that individual simple sugars can be absorbed into the bloodstream through the walls of the intestines. The bloodstream carries the simple sugars to cells throughout the body where they cross into the cells through the cell membrane. Once inside the cells, simple sugars are used as fuel in the process of cellular respiration, releasing energy which is stored as ATP. –If an organism has a greater supply of carbohydrates than needed for its energy requirements, the extra energy is converted to fats and stored by the body.

Carbohydrates Functions –Energy Source Glucose in cells is the primary source of energy - fuel for cellular respiration –Energy Storage (short term) Glycogen in the liver of animals Starch in the structures of plants –Structural Support Cellulose forms cell walls in plants –Also an important source of fiber for animals to stimulate the digestive system

Lipids Like carbohydrates, Lipids also contain Carbon, Hydrogen, and Oxygen A triglyceride is a lipid made up of –a glycerol –three fatty acids The high number of C-H bonds makes lipids very energy rich. glycerolthree fatty acids

Role of Lipids Fats are important to organisms for energy when carbohydrates are scarce, but when there is no shortage of food, stored fat accumulates. When fats are consumed, the molecules are broken down during digestion so that individual glycerol and fatty acid molecules are absorbed into the bloodstream through the walls of the intestines. –The blood stream carries the glycerol and fatty acid molecules to cells throughout the body where the molecules cross into the cells through the cell membrane. –Once inside the cell, glycerols and fatty acids are stored for later use or used as fuel for cellular respiration if there are no carbohydrates available. The process of cellular respiration releases the energy that is held in the chemical bonds of the glycerol and fatty acid molecules.

Functions –Energy Storage (long-term) Animals in colder climates will store more fats to use as insulation as well as energy to keep warm Stored fats are also used to cushion vital organs –Cellular Membrane Structure A major component of the cell membrane is the phospholipid –Building Vitamins and Hormones These help regulate our metabolism Sources –Can be found in oils, meats, and nuts Lipids steroid

Proteins Proteins contain Carbon, Hydrogen, Oxygen, and Nitrogen and sometimes Sulfur The building blocks of proteins are amino acids There are 20 different amino acids –12 amino acids are made in the human body –Humans need to consume the other 8 amino acids from sources such as nuts, beans, or meat.

Role of Proteins Proteins are more important as a source of building blocks than as a source of energy. Proteins can function as an energy source only if there is a shortage of carbohydrates or lipids. Because of their structures, proteins serve different functions. –Structural proteins are used for support such as connective tissue and keratin that forms hair and finger nails. –Transport proteins transport many substances throughout the body such as hemoglobin which transports oxygen from the lungs to the other parts of the body to be used by cells in cellular respiration. –Hormone proteins coordinate body activities such as insulin which regulates the amount of sugar in the blood. –Contractile proteins help control movement such as proteins in the muscles which help control contraction. –Enzymatic proteins accelerate the speed of chemical reactions such as digestive enzymes which break down food in the digestive tract.

Nucleic Acids Nucleotides are made up of Carbon, Hydrogen, Oxygen, Nitrogen, and Phosphorus Nucleic Acids are long chains of nucleotides Nucleotides are made up of three parts –Five carbon sugar –Phosphate –Nitrogen base

Nucleic Acids Function –Store information DNA – holds genetic code for an organism RNA – makes a copy of DNA in order to make a protein

Calorie Comparison Energy stored in organic molecules determines the caloric value Lipids have the greatest chemical bond energy over carbohydrates and proteins This can be seen in their calorie comparisons –Proteins4 calories per gram –Lipids9 calories per gram –Carbohydrates4 calories per gram