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Ch 2 Notes. Molecules of Life. Four categories of molecules are unique to cells (called macromolecules ) Carbohydrates Lipids Proteins Nucleic acids Synthesis of macromolecules involves a dehydration reaction Breakdown of macromolecules involves a hydrolysis reaction. Carbohydrates. - PowerPoint PPT Presentation
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Ch 2 Notes
Molecules of Life
• Four categories of molecules are unique to cells (called macromolecules)– Carbohydrates– Lipids– Proteins– Nucleic acids
• Synthesis of macromolecules involves a dehydration reaction
• Breakdown of macromolecules involves a hydrolysis reaction
Carbohydrates
• The ratio of hydrogen (H) atoms to oxygen (O) atoms is approximately 2:1
• Function for quick, short-term cellular energy
Carbohydrates
• Simple carbohydrates– Low number of carbon atoms (3-7)– Monosaccharides• Glucose • Fructose – found in fruits• Galactose – found in milk
– Disaccharides• Two monosaccharides joined together• Sucrose (table sugar) – formed when glucose joins with
fructose• Lactose – formed when glucose joins with galactose
Carbohydrates
• Complex carbohydrates– Contain many glucose (monosaccharide) units– Starch – storage form of glucose in plants– Glycogen – storage form of glucose in animals– Cellulose• Found in plant cell walls• Humans are unable to digest (passes through digestive
tract as fiber)
Lipids
• Contain more energy per gram than other biological molecules
• Some function as long-term energy storage in organisms
• Do not dissolve in water • Consist mostly of carbon and hydrogen atoms;
contain few oxygen atoms
Lipids
• Fats and Oils– Formed when one glycerol molecule reacts with
three fatty acid molecules– Fats• Usually of animal origin• Solid at room temperature• Used for long-term energy storage, insulation, and
cushioning– Oils• Usually of plant origin• Liquid at room temperature
Lipids– Emulsification – cause fats to mix with water– Saturated and Unsaturated Fatty Acids• Fatty acid (carbon-hydrogen chain ending with an acidic
group –COOH• Saturated fatty acids have only single covalent bonds;
lard and butter are examples• Unsaturated fatty acids have double bonds between
carbon atoms wherever fewer than two hydrogens are bonded to a carbon atom; vegetable oils
Lipids
• Steroids– Structure consists of four fused carbon rings with
attached functional groups– Cholesterol• Structural component of animal cell membrane• Precursor of several other steroids
Proteins
• Function of proteins– Fibrous structural proteins– Hormones– Muscle contraction– Transport– Protection– Enzymes
Proteins
• Structure of proteins– Made of amino acid subunits• Amino group• Acid group• R (Remainder) group – differentiates amino acids
– Dipeptide – two amino acids joined together– Polypeptide – three or more amino acids joined
together
Nucleic Acids
• Huge macromolecules composed of nucleotides
• Nucleotides composed of 3 subunit molecules:– A phosphate– A pentose sugar– A nitrogen-containing base
• Two classes of nucleic acids– DNA– RNA
Nucleic Acids
• Two classes of nucleic acids– DNA• Make up genes• Contain pentose sugar deoxyribose• Nitrogen-containing bases
– Adenine (A)– Thymine (T)– Guanine (G)– Cytosine (C)
• Usually double stranded
Nucleic Acids
– RNA• Intermediary in process of protein synthesis• Contain pentose sugar ribose• The nitrogen-containing base uracil (U) replaces
thymine• Usually single stranded