Four Classes of Organic Molecules- the Foundations and Structures of Life (page
ID: 996237 • Letter: F
Question
Four Classes of Organic Molecules- the Foundations and Structures of Life (page 554 onwards)
*1) What are organic molecules? Name the four classes of organic molecules that are essential to life.
Carbohydrates Provide Fuel and Structure for Life
1a) Many simple carbohydrates are important ____________________ molecules for living organisms while complex carbohydrates provide ____________________ and energy ____________________.
1b) Carbohydrates are divided into three major types: ____________________, ____________________, and ____________________.
1c) ____________________ provide energy for living organisms. Monosaccharides consist of carbon, hydrogen, and oxygen in a ____________________ratio and are the simplest carbohydrates.
The most common monosaccharides are ____________________ (5-carbon sugars) and ____________________ (6-carbon sugars) (Fig. A 4). They tend to form a ring instead of a chain when dissolved in water.
____________________, a 6-carbon sugar, is the primary source of energy for plants as well as other organisms. As we discuss in Chapters 9 and 10, plants use photosynthesis to make glucose and aerobic respiration to break it down for energy.
1d) Disaccharide ____________________ transports glucose for plants.
1e) Polysaccharides are large and complex carbohydrates made from thousands of monosaccharides. ____________________ and ____________________ are the two most important polysaccharides in plants (Fig. A 7). These polysaccharides consist of glucose chains that are insoluble in water.
Starch is the primary ____________________ molecule in plants and comes in two forms, ____________________ and ____________________. Glucose chains are unbranched in amylose but highly branched in amylopectin. Many organisms have enzymes like amylase and glycosidases that break down starch into glucose molecules for energy.
In addition to starch, ____________________ are also storage molecules for grasses and cereals like wheat, rye, and barley (Pollock & Cairns 1991). Fructans are water-soluble polymers of fructose mainly found in leaves and stems.
Cellulose is the most abundant organic molecule on earth and the most important ____________________ molecule in plant cell walls. Although two other complex polysaccharides, ____________________ and ____________________ also contribute to the stability of cell walls.
Like amylose, cellulose is a large and water-insoluble polysaccharide made up of ____________________ glucose chains (Fig. A 7).
However, starch and cellulose differ in the ____________________ and ____________________ patterns of their glucose molecules (Fig. A 7). As a result, starch and cellulose have very different structure and physical properties.
Proteins are the Substance of Life
2a) Proteins are the most abundant organic molecules in most living organisms and account for 50% or more of their dry mass.
____________________ refers to the sum of all the proteins found in a cell or an organism. ____________________ is the systematic study of proteomes encoded by genomes.
*2) Describe the functions of proteins.
2b) Like carbohydrates and nucleic acids, proteins are polymers made up of monomers called ____________________ ____________________.
2c) Proteins consist of one or more ____________________, which are long chains of amino acids.
*3) What is gluten?
III. Lipids:
3a) Lipids are fats and fatlike substances that are generally insoluble in water or ____________________ (means “water-fearing”). Lipids contain large numbers of ____________________ and ____________________ atoms with a few ____________________ atoms (Fig. A 15).
3b) Most lipid molecules consist of a ____________________, a three-carbon molecule, and two or three ____________________ ____________________chains.
Fatty acid molecules are often referred to as ____________________ chains because of their numerous carbon and hydrogen atoms (Fig. A 15).
Explanation / Answer
Organic molecules contain carbon and hydrogen chemically linked to one another in long chains, with carbon as the backbone and hydrogen atoms attached to the carbon atoms. These atoms' ability to attach to one another allows for the creation of innumerable compounds conducive to life. All organisms need four types of organic molecules: nucleic acids, proteins, carbohydrates and lipids; life cannot exist if any of these molecules are missing.
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