Chemical Level of Cell Organization

• Decomposition reactions


  Catabolism - breaking down of large molecules into smaller ones
• Ammonia (NH3)


  Comes from the decomposition of proteins and the conversion of amino acids in cellular respiration to ATP molecules
• Carbohydrates


  Organic molecules containing carbon, hydrogen, and oxygen in a ratio near 1:2:1
• Carbohydrates


  • Ribose and deoxyribose (parts of RNA and DNA)
  • Sugars, starch, glycogen (energy storage)
  • Cellulose and chitin (cell strengthening)
• Lipids


  Insoluble in water, include fats, phospholipids, steroids, prostaglandins
• Proteins


  Composed of carbon, hydrogen, oxygen, and nitrogen covalently bonded
• Functions of proteins


  • Part of cell membranous structures
  • Enzymes
  • Antibodies
  • Source of energy converted to ATP
• Nucleic acids


  DNA and RNA, composed of CHONP
• Adenosine triphosphate (ATP)


  Energy stored in the ATP molecule is used to run the cell and perform activities such as repair, reproduction, assimilation, and transport of materials across cell membranes
• pH


  Defined as the negative logarithm of the hydrogen ion concentration in moles/liter
• Acidosis


  Abnormal physiological state caused by low blood pH (below 7.35)
• Alkalosis


  Abnormal physiological state caused by high blood pH (above 7.45)
• Blood pH above 7.8 generally causes uncontrollable and sustained skeletal muscle contractions
• Buffers


  Compounds that stabilize the pH of a solution by removing or replacing H+
• Buffer systems


  Usually involve a weak acid and its related salt, which functions as a weak base
• Buffers and buffer systems in body fluids help maintain the pH within normal limits
• Organic compounds


  Made up of long chains of carbon atoms linked by covalent bonds, forming additional covalent bonds with H+, O2, N2, P, S, Fe, or other elements
• Macromolecules


  Include carbohydrates, lipids, proteins, and nucleic acids
• Monomers


  Subunits that are bonded to other identical molecules to form a polymer
• Dehydration synthesis


  Reaction where monomers are joined together to form a polymer
• Hydrolysis


  Reaction where polymers are separated or released into their monomer subunits
• Glucose


  A monosaccharide carbohydrate
• Glycogen (animal starch) does not dissolve in water or other body fluids
• Lipids make up 12–18% of the total body weight of adult men, and 18–24% for adult women
• Most lipids are hydrophobic, or insoluble in water, but special transport mechanisms carry them into the bloodstream
• Classes of lipids


  • Fatty acids
  • Eicosanoids
  • Glycerides
  • Steroids
  • Phospholipids and glycolipids
• Saturated fatty acids


  Contain only single covalent bonds, found in whole milk, butter, eggs, beef, pork, and coconut and palm oils
• Eicosanoids


  Lipids derived from arachidonic acid, a fatty acid that must be absorbed in the diet because the body cannot synthesize it; include leukotrienes and prostaglandins
• Prostaglandins


  Compounds released by cells to coordinate or direct local cellular activities, extremely powerful even in small quantities
• Glycerides


  Include triglycerides (triacylglycerols or neutral fat), an energy source, insulation, and protection
• Steroids


  Differ in the functional groups attached to the basic framework, include cholesterol and steroid hormones
• Lipid reserves retain both valuable lipid-soluble vitamins (A, D, E, K) and potentially dangerous lipid-soluble pesticides
• Prostaglandins


  Compounds released by cells to coordinate or direct local cellular activities, and they are extremely powerful even in small quantities. Also known as local hormones
• Glycerides


  Triglycerides, also known as triacylglycerols or neutral fat; energy source, insulation, protection
• Cholesterol


  Contained in plasma membrane
• Functions of proteins


  • Support (structural proteins)
  • Movement (contractive proteins)
  • Transport (transport proteins)
  • Buffering
  • Metabolic regulation (enzymes)
  • Coordination and control (protein hormones)
  • Defense (special clotting proteins)
• Protein shape


  Determines its functional characteristics, and the sequence of amino acids ultimately determines its shape
• Primary structure of a protein

  Determined by its amino acid sequence
• Secondary structure of a protein

  Determined by the hydrogen bonds between amino acids that cause the protein to coil into helices or pleated sheets. This shape is crucial to the functioning of proteins. Once H-bonds are destroyed proteins becomes nonfunctional
• Tertiary structure of a protein


  A secondary folding caused by interactions within the peptide bonds and between sulfur atoms of different amino acids